Showing papers in "Cancer Research in 1995"

Vascular Permeability in a Human Tumor Xenograft: Molecular Size Dependence and Cutoff Size

Abstract: Molecular size is one of the key determinants of transvascular transport of therapeutic agents in tumors. However, there are no data in the literature on the molecular size dependence of microvascular permeability in tumors. Therefore, we measured microvascular permeability to various macromolecules in the human colon adenocarcinoma LS174T transplanted in dorsal skin chambers in severe combined immunodeficient mice. These molecules were fluorescently labeled and injected i.v. into mice. The microvascular permeability was calculated from the fluorescence intensity measured by the intravital fluorescence microscopy technique. The value of permeability varied approximately 2-fold in the range of molecular weight from 25,000 to 160,000. These data indicate that tumor vessels are less permselective than normal vessels, presumably due to large pores in the vessel wall. The transport of macromolecules appears to be limited by diffusion through these pores. The cutoff size of the pores was estimated by observations of transvascular transport of sterically stabilized liposomes of 100-600 nm in diameter. We found that tumor vessels in our model were permeable to liposomes of up to 400 nm in diameter, suggesting that the cutoff size of the pores is between 400 and 600 nm in diameter.

Infection with Helicobacter pylori Strains Possessing cagA Is Associated with an Increased Risk of Developing Adenocarcinoma of the Stomach

Abstract: To determine whether infection with a Helicobacter pylori strain possessing cagA is associated with an increased risk of development of adenocarcinoma of the stomach, we used a nested case-control study based on a cohort of 5443 Japanese-American men in Oahu, Hawaii, who had a physical examination and a phlebotomy during 1967 to 1970 We matched 103 H pylori -infected men who developed gastric cancer during a 21-year surveillence period with 103 H pylori -infected men who did not develop gastric cancer and tested stored serum specimens from patients and controls for the presence of serum IgG to the cagA product of H pylori using an ELISA The serum IgG assay using a recombinant CagA fragment had a sensitivity of 944% and a specificity of 925% when used in a clinically defined population; serological results were stable for more than 7 years For men with antibodies to CagA, the odds ratio of developing gastric cancer was 19 (95% confidence interval, 09–40); for intestinal type cancer of the distal stomach, the odds ratio was 23 (95% confidence interval, 10–52) Age cagA -positive H pylori strain in comparison with a cagA -negative strain somewhat increases the risk for development of gastric cancer, especially intestinal type affecting the distal stomach

Inactivation of the CDKN2/p16/MTS1 Gene Is Frequently Associated with Aberrant DNA Methylation in All Common Human Cancers

Abstract: The tumor suppressor gene CDKN2/p16/MTS1, located on chromosome 9p21, is frequently inactivated in many human cancers through homozygous deletion. Recently, we have reported another pathway of inactivation that involves loss of transcription associated with de novo methylation of a 5' CpG island of CDKN2/p16 in lung cancers, gliomas, and head and neck squamous cell carcinomas. We now show that this aberrant CpG island methylation also occurs frequently in cell lines of breast cancer (33%), prostate cancer (60%), renal cancer (23%), and colon cancer (92%) and is associated with loss of transcription. Primary tumors of the breast (31%) and colon (40%) also displayed de novo methylation of this CpG island. This alteration of p16 in colon cancer was particularly striking, since inactivation does not occur through homozygous deletion in this tumor type. Our data show that in tumors, de novo methylation of the 5' CpG island is a frequent mode of inactivation of CDKN2/p16 and also firmly demonstrate that CDKN2/p16 is one of the most frequently altered genes in human neoplasia.

Expression of vascular endothelial growth factor and its receptor, KDR, correlates with vascularity, metastasis, and proliferation of human colon cancer.

Abstract: We studied the correlation between expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and their receptors with vascularity, metastasis, and proliferative index of human colon cancers. Immunohistochemical analyses using antibodies against VEGF, bFGF, their receptors (KDR, flt-1, bek, and flg), factor VIII, and proliferating cell nuclear antigen were carried out on archival specimens of 52 human colon carcinomas and 10 adenomas. Vessels were quantitated by light microscopy (x200), and the intensity of staining for VEGF and bFGF was assessed on a scale of 0-3+. The presence or absence of immunostaining for KDR, flt-1, bek, and flg was evaluated in endothelial cells, and proliferation was determined by counting the number of proliferating cell nuclear antigen-positive cells per 500 tumor cells. Expression of VEGF and KDR was higher in metastatic than in nonmetastatic neoplasms and directly correlated with the extent of neovascularization and the degree of proliferation, whereas expression of bFGF, flt-1, bek, and flg did not differ among tumor types. Vessel counts were greater in metastatic tumors than in nonmetastatic tumors. These findings support the hypothesis that VEGF is an important angiogenic factor in primary and metastatic human colon cancer. VEGF expression and vessel counts may aid in predicting patients at risk for metastasis from colon cancer.

p21 is necessary for the p53-mediated G1 arrest in human cancer cells.

Abstract: DNA-damaging agents induce a p53-dependent G1 arrest that may be critical for p53-mediated tumor suppression. It has been suggested that p21WAF1/CIP1, a cdk inhibitory protein transcriptionally regulated by p53, is an effector of this arrest. To test this hypothesis, an isogenic set of human colon adenocarcinoma cell lines differing only in their p21 status was created. The parental cell line underwent the expected cell cycle changes upon induction of p53 expression by DNA damage, but the G1 arrest was completely abrogated in p21-deficient cells. These results unambiguously establish p21 as a critical mediator of one well-documented p53 function and have important implications for understanding cell cycle checkpoints and the mechanism(s) through which p53 inhibits human neoplasia.

Epothilones, a New Class of Microtubule-stabilizing Agents with a Taxol-like Mechanism of Action

Abstract: Tubulin polymerization into microtubules is a dynamic process, with the equilibrium between growth and shrinkage being essential for many cellular processes. The antineoplastic agent taxol hyperstabilizes polymerized microtubules, leading to mitotic arrest and cytotoxicity in proliferating cells. Using a sensitive filtration-calorimetric assay to detect microtubule nucleating activity, we have identified epothilones A and B as compounds that possess all the biological effects of taxol both in vitro and in cultured cells. The epothilones are equipotent and exhibit kinetics similar to taxol in inducing tubulin polymerization into microtubules in vitro (filtration, light scattering, sedimentation, and electron microscopy) and in producing enhanced microtubule stability and bundling in cultured cells. Furthermore, these 16-membered macrolides are competitive inhibitors of [3H]taxol binding, exhibiting a 50% inhibitory concentration almost identical to that of taxol in displacement competition assays. Epothilones also cause cell cycle arrest at the G2-M transition leading to cytotoxicity, similar to taxol. In contrast to taxol, epothilones retain a much greater toxicity against P-glycoprotein-expressing multiple drug resistant cells. Epothilones, therefore, represent a novel structural class of compounds, the first to be described since the original discovery of taxol, which not only mimic the biological effects of taxol but also appear to bind to the same microtubule-binding site as taxol.

Expression of Cyclooxygenase-1 and -2 in Human Colorectal Cancer

Abstract: Several studies indicate that nonsteroidal anti-inflammatory drugs including indomethacin, aspirin, sulindac, and piroxicam reduce the risk of colon cancer. Furthermore, nonsteroidal anti-inflammatory drugs that inhibit the cyclooxygenase (COX) enzyme were shown to inhibit the development of colon cancer in animal models of carcinogenesis. Non-steroidal anti-inflammatory drugs inhibit the enzymatic activity of both the constitutive (COX-1) and inducible (COX-2) isoforms of COX enzyme. We have investigated the expression of COX-1 and COX-2 polypeptides in human colon cancer tissues using immunohistochemistry. Enhanced COX-2 expression was observed in colon cancer tissues from 15 subjects with clinically diagnosed colorectal cancer. Marked COX-2 expression was observed in cancer cells, inflammatory cells, vascular endothelium, and fibroblasts of the lesional tissues compared with the nonlesional and normal colon tissues. The extent and intensity of the immunoreactive COX-2 in cancer cells was much greater than that of the other cell types. In contrast, the expression of COX-1 polypeptide was weak in both normal and cancerous specimens. These data suggest that the enhanced expression of the COX-2 gene in colon cancer tissues may contribute to the enhanced synthesis of prostaglandin E2 by the colon cancer tissues. Enhanced expression of COX-2 may play a role in the pathogenesis of colon cancer. Furthermore, selective inhibition of COX-2 may prove to be more efficacious in the retardation of colon cancer development.

Expression of Prostaglandin G/H Synthase-1 and -2 Protein in Human Colon Cancer

Abstract: Prostaglandin G/H synthase (PGHS), a key enzyme leading to the formation of prostaglandins, is the target of nonsteroidal antiinflammatory drugs Two forms of the enzyme have been identified, PGHS-1 and PGHS-2 Epidemiological evidence has suggested that aspirin and other nonsteroidal antiinflammatory drugs may reduce the risk of colorectal cancer We examined by immunoblot analyses the expression of human PGHS-1 and PGHS-2 protein in 25 matched colon cancer and nontumor tissues, 4 premalignant polyps, 5 control colon tissues from noncancer patients, and 3 matched normal and cancerous breast tissue samples PGHS-1 was detected in all normal and tumor tissue In contrast, PGHS-2 was not detected in 23 of 25 normal colon tissues but was detected in 19 of 25 colon tumors PGHS-2 protein was not observed in four human premalignant polyp samples, control colon from noncancer patients, or matched normal or cancerous breast tissues These results suggest that the beneficial effects of nonsteroidal antiinflammatory drugs in colon cancer may be mediated by inhibition of PGHS-2

E-Cadherin Expression Is Silenced by DNA Hypermethylation in Human Breast and Prostate Carcinomas

Abstract: Expression of the Ca2+-dependent, homotypic cell:cell adhesion molecule, E-cadherin (E-cad), suppresses tumor cell invasion and metastasis in experimental tumor models. Decreased E-cad expression is common in poorly differentiated, advanced-stage carcinomas. These data implicate E-cad as an “invasion suppressor” gene. The mechanism by which E-cad is silenced in advanced stage carcinomas is unclear. In this report, we show that: (a) the 5′ CpG island of E-cad is densely methylated in E-cad-negative breast and prostate carcinoma cell lines and primary breast carcinoma tissue but is unmethylated in normal breast tissue; (b) treatment with the demethylating agent, 5-aza-2′-deoxycytidine, partially restores E-cad RNA and protein levels in E-cad-negative breast and prostate carcinoma cell lines; and (c) an E-cad promoter/CAT construct is expressed in both E-cad-positive and -negative breast and prostate carcinoma cell lines, indicating that these cells have the active transcriptional machinery necessary for E-cad gene expression. Our data demonstrate that frequent loss of E-cad expression in human breast and prostate carcinomas results from hypermethylation of the E-cad promoter region.

Mutant ras oncogenes upregulate VEGF/VPF expression: implications for induction and inhibition of tumor angiogenesis.

Abstract: The growth of solid tumors in vivo beyond 1-2 mm in diameter requires induction and maintenance of an angiogenic response. This can occur through the release of various angiogenic growth factors from tumor cells. One such factor is vascular endothelial growth factor/vascular permeability factor (VEGF/VPF), a secreted and specific mitogen for vascular endothelial cells. We show that one of the most commonly encountered genetic changes detected in human cancer, i.e., expression of mutant ras oncogenes, is associated with marked up-regulation of VEGF/VPF in transformed epithelial cells. Thus, elevation of the levels of both VEGF/VPF mRNA and secreted functional protein were detected in human and rodent tumor cell lines expressing mutant K-ras or H-ras oncogenes, respectively. Genetic disruption of the mutant K-ras allele in human colon carcinoma cells was associated with a reduction in VEGF/VPF activity. Furthermore, pharmacological disruption of mutant RAS protein function in H-ras transformed rat intestinal epithelial cells by treatment with L-739,749 (a protein farnesyltransferase inhibitor) caused a significant suppression of VEGF/VPF. The results suggest that dominantly acting ras oncogenes may contribute to the growth of solid tumors in vivo not only by a direct effect on tumor cell proliferation but also indirectly, i.e., by facilitating tumor angiogenesis. Hence, pharmacologically targeting mutant ras oncogenes could conceivably suppress solid tumor growth in vivo, in part, by inhibiting tumor-induced angiogenesis.

Microsatellite instability and mutations of the transforming growth factor β type II receptor gene in colorectal cancer

Abstract: The TGF beta type II receptor (RII) was found to be mutated within a polyadenine tract in 100 of 111 (90%) colorectal cancers with microsatellite instability Other polyadenine tracts of similar length were mutated in these samples but not as frequently as RII In most cases, the polyadenine tract mutations affected both alleles of RII, and in four tumors heterozygous for the polyadenine mutations, three had additional mutations that were expected to inactivate the other RII allele These genetic data support the idea that RII behaves like a tumor suppressor during CR cancer development and is a critical target of inactivation in mismatch repair-deficient tumors

Methylation of the 5′ CpG Island of the p16/CDKN2 Tumor Suppressor Gene in Normal and Transformed Human Tissues Correlates with Gene Silencing

Abstract: Loss of heterozygosity on 9p21, where the p16/CDKN2 tumor suppressor and the p15INK4B cell cycle regulator genes are located, is a common genetic alteration in bladder cancer. However, it has been difficult to demonstrate homozygous deletions and intragenic mutations in either of these two genes in primary transitional cell carcinomas (TCC) of the bladder. Similarly, colon cancer-derived cell lines have shown no homozygous deletions of the p16/CDKN2 locus in contrast to a wide variety of tumor-derived cell lines. We have investigated abnormal methylation of the 5' CpG islands of the p16/CDKN2 and p15INK4B genes as an alternative mechanism of inactivation of these genes in bladder and colon cancers. De novo methylation of the 5' CpG island of p16/CDKN2 was observed in 12 of 18 (67%) uncultured bladder TCCs and in 2 of 3 (67%) bladder cell lines. In contrast, only 1 of 10 (10%) colon carcinomas showed methylation of the 5' CpG island of p16/CDKN2. It was striking to find that this region was extensively methylated and the gene not expressed in the normal colonic mucosa of 6 of 10 (60%) patients with colon cancer, whereas 5 of the corresponding colon tumors showed no methylation and high levels of p16/CDKN2 expression. Our data show a significant correlation (P = 0.00001, two-sided) between the absence of p16/CDKN2 expression and methylation of its 5' CpG island in bladder tumors, cell lines, and normal colon mucosa. In contrast, no association was observed between expression and methylation status of the 5' CpG island of p15INK4B. Our results suggest that the p16/CDKN2 tumor suppressor gene may be inactivated by methylation of its 5' CpG island in TCCs of the bladder. We also present evidence of methylation of the 5' CpG island in this autosomal gene in normal colonic tissue.

The Human Tumor Cell-derived Collagenase Stimulatory Factor (Renamed EMMPRIN) Is a Member of the Immunoglobulin Superfamily

Abstract: Tumor cell-derived collagenase stimulatory factor, renamed extracellular matrix metalloproteinase inducer (EMMPRIN), is a M(r) approximately 58,000 glycoprotein which is located on the outer surface of human tumor cells and which interacts with fibroblasts to stimulate expression of several matrix metalloproteinases in the fibroblasts. In this study, we have used several approaches to isolate a complementary DNA encoding EMMPRIN. Several peptide sequences obtained from the isolated M(r) 58,000 glycoprotein are found in the translated complementary DNA clone, verifying its identity. Computer database searches indicate that EMMPRIN is a member of the immunoglobulin superfamily and that the deduced amino acid sequence of EMMPRIN is identical to that recently reported for human basigin and M6 antigen, molecules of previously undetermined biological function.

Chemoprevention of Colon Carcinogenesis by Dietary Curcumin, a Naturally Occurring Plant Phenolic Compound

Abstract: Human epidemiological and laboratory animal model studies have suggested that nonsteroidal antiinflammatory drugs reduce the risk of development of colon cancer and that the inhibition of colon carcinogenesis is mediated through the alteration in cyclooxygenase metabolism of arachidonic acid. Curcumin, which is a naturally occurring compound, is present in turmeric, possesses both antiinflammatory and antioxidant properties, and has been tested for its chemopreventive properties in skin and forestomach carcinogenesis. The present study was designed to investigate the chemopreventive action of dietary curcumin on azozymethaneinduced colon carcinogenesis and also the modulating effect of this agent on the colonic mucosal and tumor phospholipase A 2 , phospholipase Cγ1, lipoxygenase, and cyclooxygenase activities in male F344 rats. At 5 weeks of age, groups of animals were fed the control (modified AIN-76A) diet or a diet containing 2000 ppm of curcumin. At 7 weeks of age, all animals, except those in the vehicle (normal saline)-treated groups, were given two weekly s.c. injections of azoxymethane at a dose rate of 15 mg/kg body weight. All groups were continued on their respective dietary regimen until the termination of the experiment at 52 weeks after the carcinogen treatment. Colonic tumors were evaluated histopathologically. Colonic mucosa and tumors were analyzed for phospholipase A 2 , phospholipase Cγ1, ex vivo prostaglandin (PG) E 2 , cyclooxygenase, and lipoxygenase activities. The results indicate that dietary administration of curcumin significantly inhibited incidence of colon adenocarcinomas ( P P P P 57% compared to the control diet. Animals fed the curcumin diet showed decreased activities of colonic mucosal and tumor phospholipase A 2 (50%) and phospholipase Cγ1 (40%) and levels of PGE 2 (>38%). The formation of prostaglandins such as PGE 2 , PGF 2α , PGD 2 , 6-keto PGF 1α , and thromboxane B 2 through the cyclooxygenase system and production of 5( S )-, 8( S )-, 12( S )-, and 15( S )-hydroxyeicosatetraenoic acids via the lipoxygenase pathway from arachidonic acid were reduced in colonic mucosa and tumors of animals fed the curcumin diet as compared to control diet. Although the precise mechanism by which curcumin inhibits colon tumorigenesis remains to be elucidated, it is likely that the chemopreventive action, at least in part, may be related to the modulation of arachidonic acid metabolism.

Thymidylate Synthase Gene and Protein Expression Correlate and Are Associated with Response to 5-Fluorouracil in Human Colorectal and Gastric Tumors

Abstract: Thymidylate synthase (TS) is the target enzyme for 5-fluorouracil (5-FU). We have correlated TS protein and gene expression with the response in patients with colorectal ( n = 9) and gastric cancer ( n = 12) treated with infusional 5-FU plus leucovorin (LV) or infusional 5-FU/LV and cisplatin, respectively. TS protein expression was analyzed by Western blot using TS106 monoclonal antibody and densitometry scanning. TS gene expression was measured by PCR analysis using β-actin as an internal standard and expressed as a TS:β-actin mRNA ratio. A close linear relationship was noted between TS protein expression and TS gene expression ( r 2 = 0.60) for the 21 tumor samples analyzed. TS immunohistochemical staining on 15 of the 21 samples revealed that the TS staining intensity correlated closely with TS protein and mRNA expression. In two biopsy samples, TS protein levels and TS gene expression did not correlate; however, one of these exhibited a focal TS staining pattern. Both the TS protein level and TS gene expression were significantly associated with response to 5-FU-based therapy. Patients with responsive disease had a mean TS protein level of 0.17 ± 0.03 arbitrary units (range, 0.05 to 0.38), whereas in patients whose tumors did not respond, the mean TS protein level was significantly higher 0.60 ± 0.09 (range, 0.06 to 1.01; P < 0.01). A similar pattern was noted with TS gene expression. In patients with responsive disease, the mean TS:β-actin gene ratio was 1.36 ± 0.3 (range, 0.5–3.3 × 10-3). In contrast, biopsies from patients with unresponsive disease had a mean TS:β-actin gene ratio of 15.4 ± 2.6 × 10-3 (range, 2.7–35.9; P < 0.01). TS protein and TS mRNA expression are highly correlated, and each predict for response to 5-FU/LV-based chemotherapy in patients with colorectal and gastric cancer.

Frequent Expression of a Mutant Epidermal Growth Factor Receptor in Multiple Human Tumors

Abstract: The epidermal growth factor receptor has received much interest as a target for various antineoplastic agents, but a complication is that many normal tissues also express this receptor. We have previously identified in human glial tumors an 801-bp in-frame deletion within the epidermal growth factor receptor gene that created a novel epitope at the junction. By using Western blot assays with a mutant-specific antibody as a rapid and sensitive means for detecting this alteration in primary human tumors, it was found that 57% (26 of 46) of high-grade and 86% (6 of 7) of low-grade glial tumors, but not normal brain, express this protein. This altered receptor was also present in 66% (4 of 6) of pediatric gliomas and 86% (6 of 7) of medulloblastomas, 78% (21 of 27) of breast carcinomas, and 73% (24 of 32) of ovarian carcinomas. The fact that this receptor is frequently found in tumors but not in normal tissue makes it an attractive candidate for various antitumor strategies.

Overexpression of the Focal Adhesion Kinase (p125FAK) in Invasive Human Tumors

Abstract: The focal adhesion kinase (FAK) gene encodes a tyrosine kinase (p125FAK) thought to be involved in signal transduction pathways used in cell adhesion, motility, and anchorage-independent growth. Because alterations in these cellular processes occur in tumor invasion and metastasis, we studied the protein expression of FAK in a variety of human tumors and found that in the 119 samples studied, increased levels of p125FAK correlated with the invasive potential of a tumor. By comparing FAK expression in tumors with normal tissue from the same patient, we found that p125FAK was significantly elevated in 17 (100%) of 17 invasive and metastatic colonic lesions and in 22 (88%) of 25 invasive and metastatic breast tumors. Additional studies of FAK expression in 13 high grade sarcomas showed high levels in all samples compared to benign, noninvasive mesenchymal specimens. Furthermore, FAK protein levels were elevated in preinvasive lesions, such as large (> 2 cm) colonic villous adenomas, whereas noninvasive, yet hypercellular, neoplastic tissues such as parathyroid and hepatocellular adenomas did not overexpress FAK. These data provide evidence that both epithelial and mesenchymal tumor progression are accompanied by increased p125FAK expression and suggest that the level of FAK expression might be a marker for the invasive potential of a tumor.

The Insulin-like Growth Factor I Receptor: A Key to Tumor Growth?

Abstract: The insulin-like growth factor I receptor (IGF-IR) belongs to the family of transmembrane tyrosine kinase receptors, like the receptors for platelet-derived growth factor, the epidermal growth factor, insulin, and others. Genetic evidence has shown that the IGF-IR is required for optimal growth in vitro and in vivo. Even more important, however, have been recent findings from several laboratories clearly showing that the IGF-IR is an absolute requirement for the establishment and maintenance of the transformed phenotype, both in vivo and in vitro and in several cell types. These findings indicate that the IGF-IR plays a central role in the mechanism of transformation and, as such, could be a preferred target for therapeutic interventions.

Topological Control of p21WAF1/CIP1 Expression in Normal and Neoplastic Tissues

Abstract: The p53-regulated gene product p21WAF1/CIP1 is the prototype of a family of small proteins that negatively regulate the cell cycle. To learn more about p21WAF1/CIP1 regulation in vivo, monoclonal antibodies were developed for immunohistochemistry. These revealed that p21WAF1/CIP1 expression followed radiation-induced DNA damage in human skin in a pattern consistent with its regulation by p53. A detailed comparison of the human, rat, and mouse p21WAF1/CIP1 promoter sequences revealed that this induction was probably mediated by conserved p53-binding sites upstream of the transcription start site. In unirradiated tissues, p21WAF1/CIP1 expression was apparently independent of p53 and was observed in a variety of cell types. Moreover, there was a striking compartmentalization of p21WAF1/CIP1 expression throughout the gastrointestinal tract that correlated with proliferation rather than differentiation. As epithelial cells migrated up the crypts, the Ki67-expressing proliferating compartment near the crypt base ended abruptly, with the coincident appearance of a nonproliferating compartment expressing p21WAF1/CIP1. In colonic neoplasms, this distinct compartmentalization was largely abrogated. Cell cycle inhibitors are thus subject to precise topological control, and escape from this regulation may be a critical feature of neoplastic transformation.

bcl-2 and p53 Oncoprotein Expression during Colorectal Tumorigenesis

Abstract: Apoptosis or programmed cell death represents a mechanism by which cells possessing DNA damage can be deleted. The bcl-2 proto-oncogene is a known inhibitor of apoptosis that may allow the accumulation and propagation of cells containing genetic alterations. To determine if and when the bcl-2 gene is activated during colorectal tumorigenesis and its relationship to p53, we analyzed normal mucosa, hyperplastic and dysplastic epithelial polyps, and carcinomas for the expression of these markers using immunohistochemistry. Whereas bcl-2 staining was restricted to basal epithelial cells in normal and hyperplastic mucosa, bcl-2 expression was detected in parabasal and superficial regions in dysplastic polyps and carcinomas. An inverse correlation was found between bcl-2 and p53 expression in adenomas, suggesting that these markers may regulate a common cell death pathway. Furthermore, carcinomas with a high percentage of bcl-2-positive cells were significantly more likely to have low rates of spontaneous apoptosis, as determined histologically, than those cancers with low or absent bcl-2 expression. Abnormal activation of the bcl-2 gene appears to be an early event in colorectal tumorigenesis that can inhibit apoptosis in vivo and may facilitate tumor progression.

Overexpression of bcl-2 Protects Prostate Cancer Cells from Apoptosis in Vitro and Confers Resistance to Androgen Depletion in Vivo

Abstract: Normal (nonneoplastic) human prostatic secretory epithelial cells do not express the bcl-2 protein. However, a recent immunohistochemical survey of neoplastic human prostate tissues showed that a fraction of primary untreated prostate adenocarcinoma cells expressed this apoptosis-suppressing oncoprotein at significant levels (Colombel et al., Am. J. Pathol., 143: 390-400, 1993). Additionally, a number of hormone-refractory prostatic adenocarcinomas obtained from hormonally-treated patients (subsequent to surgical or drug castration therapy) were examined and were found to be uniform in their elevated expression of bcl-2 oncoprotein. The results of this preliminary survey imply that bcl-2 expression distinguishes a subgroup of primary human prostate cancers and that the expression of this protein might be a factor enabling prostate cancer cells to survive in an androgen-deprived environment. The current study was undertaken to determine the degree to which overexpression of bcl-2 can protect human prostate cancer cells from apoptotic stimuli in vitro and in vivo. Human prostate cancer cells (LNCaP) were transfected with a neomycin-selectable eucaryotic expression vector containing cDNA encoding human bcl-2. Transfected clonal variants that express bcl-2 protein (LNCaP/bcl-2) were unaltered with regard to their basal growth rate in 10% serum-containing medium, or with regard to their expression of the differentiated human prostate cell gene products prostate-specific antigen or androgen receptor protein. The bcl-2-transfected clones were altered, however, with regard to their growth rate in charcoal-stripped serum lacking dihydrotestosterone. Additionally, in contrast to the parental or control-transfected cell lines, LNCaP/bcl-2 cells were highly resistant to a variety of apoptotic stimuli in vitro including serum starvation and 10 nM phorbol ester (phorbol 12-myristate 13-acetate) supplementation of the medium. Lastly, the overexpression of bcl-2 by these prostate cancer cells altered their tumorigenic potential in a nude mouse assay. s.c. injections of 10(6) LNCaP/bcl-2 cells into male nude mice resulted in earlier and larger tumor formation compared to an equivalent injection of parental or control-transfected LNCaP cells. When these variant cell lines were injected into castrated male nude mice, only the LNCaP/bcl-2-transformed cells gave rise to tumors. Moreover, LNCaP/bcl-2 tumors grown in intact male nude mice were refractory to the growth-inhibiting effects of castration demonstrated by parental LNCaP cells. Data obtained in this study demonstrate that the bcl-2 oncoprotein can protect prostate cancer cells from apoptotic stimuli in vitro and suggest that such protection correlates with the ability to form hormone-refractory prostate tumors in vivo.

Inhibition of apoptosis during development of colorectal cancer.

Abstract: Colorectal tumorigenesis proceeds through an accumulation of specific genetic alterations. Studies of the mechanism by which these genetic changes effect malignant transformation have focused on the deregulation of cell proliferation. However, colorectal epithelial homeostasis is dependent not only on the rate of cell production but also on apoptosis, a genetically programmed process of autonomous cell death. We investigated whether colorectal tumorigenesis involved an altered susceptibility to apoptosis by examining colorectal epithelium from normal mucosa, adenomas from familial adenomatous polyposis, sporadic adenomas, and carcinomas. The transformation of colorectal epithelium to carcinomas was associated with a progressive inhibition of apoptosis. The inhibition of apoptosis in colorectal cancers may contribute to tumor growth, promote neoplastic progression, and confer resistance to cytotoxic anticancer agents.

Genetic Changes in Primary and Recurrent Prostate Cancer by Comparative Genomic Hybridization

Abstract: Genetic changes leading to the development of prostate cancer and factors that underlie the clinical progression of the disease are poorly characterized. Here, we used comparative genomic hybridization (CGH) to screen for DNA sequence copy number changes along all chromosomes in 31 primary and 9 recurrent uncultured prostate carcinomas. The aim of the study was to identify those chromosome regions that contain genes important for the development of prostate cancer and to identify genetic markers of tumor progression. CGH analysis indicated that 74% of primary prostate carcinoma showed DNA sequence copy number changes. Losses were 5 times more common than gains and most often involved 8p (32%), 13q (32%), 6q (22%), 16q (19%), 18q (19%), and 9p (16%). Allelic loss studies with 5 polymorphic microsatellite markers for 4 different chromosomes were done from 13 samples and showed a 76% concordance with CGH results. In local recurrences that developed during endocrine therapy, there were significantly more gains (P < 0.001) and losses (P < 0.05) of DNA sequences than in primary tumors, with gains of 8q (found in 89% of recurrences versus 6% of primary tumors), X (56% versus 0%), and 7 (56% versus 10%), as well as loss of 8p (78% versus 32%), being particularly often involved. In conclusion, our CGH results indicate that losses of several chromosomal regions are common genetic changes in primary tumors, suggesting that deletional inactivation of putative tumor suppressor genes in these chromosomal sites is likely to underlie development of prostate cancer. Furthermore, the pattern of genetic changes seen in recurrent tumors with the frequent gains of 7, 8q, and X suggests that the progression of prostate cancer and development of hormone-independent growth may have a distinct genetic basis. These chromosome aberrations may have diagnostic utility as markers of prostate cancer progression.

Monoclonal Antibodies against EGFRvIII Are Tumor Specific and React with Breast and Lung Carcinomas and Malignant Gliomas

Abstract: Despite molecular biological advances in understanding human cancers, translation into therapy has been less forthcoming; targeting neoplastic cells still requires that tumor-specific markers, preferably those on the cell surface, be identified. The epidermal growth factor receptor (EGFR) exists in a deletion-mutant form, EGFRvIII, which has been identified by genetic and immunological means in a subset of gliomas and non-small cell lung carcinomas. Specific polyvalent antisera to the extracellular portion of the variant were readily induced, but immunization using a synthetic linear peptide representing the unique EGFRvIII primary sequence has been unsuccessful in mice or macaques. We report here five specific monoclonal antibodies (mAbs) developed through long-term immunization protocols using the EGFRvIII-specific synthetic peptide and the intact variant in different formats that maintained secondary and tertiary conformation. These mAbs identify the EGFRvIII on the cell surface with relatively high affinity (KA range, 0.13 to 2.5 x 10(9) M-1) by live cell Scatchard analysis. These mAbs are specific for EGFRvIII as determined by RIA, ELISA, Western blot, analytical flow cytometry, autophosphorylation, and immunohistochemistry. Isolating specific mAbs enabled us to analyze normal and neoplastic human tissue and establish that EGFRvIII is truly tumor specific for subsets of breast carcinomas and for previously reported non-small cell lung carcinomas and gliomas. Also, this receptor is not expressed by any normal human tissues thus far examined, including elements of the peripheral, central nervous, and lymphoid systems. With mAbs, we identified a higher incidence of EGFRvIII positivity in gliomas than previously described and identified an EGFRvIII-positive subset of breast tumors; also, we observed that the EGFRvIII epitope is not expressed in normal tissues, and we demonstrated the localizing and therapeutic potential of the mAbs for tumors expressing this epitope. Our observations strongly warrant development of this mAb-antigen system as therapy for breast, lung, and central nervous system tumors.

Disruption of p53 function sensitizes breast cancer MCF-7 cells to cisplatin and pentoxifylline

Abstract: The possibility that appropriately designed chemotherapy could act selectively against p53-defective tumor cells was explored in MCF-7 human breast cancer cells These cells were chosen because they have normal p53 function but are representative of a tumor cell type that does not readily undergo p53-dependent apoptosis Two sublines (MCF-7/E6 and MCF-7/mu-p53) were established in which p53 function was disrupted by transfection with either the human papillomavirus type-16 E6 gene or a dominant-negative mutant p53 gene p53 function in MCF-7/E6 and MCF-7/mu-p53 cells was defective relative to control cells in that there were no increases in p53 or p21Waf1/Cip1 protein levels and no G1 arrest following exposure to ionizing radiation Survival assays showed that p53 disruption sensitized MCF-7 cells to cisplatin (CDDP) but not to several other DNA-damaging agents CDDP sensitization was not limited to MCF-7 cells since p53 disruption in human colon carcinoma RKO cells also enhanced sensitivity to CDDP Contrary to the other DNA-damaging agents tested, CDDP-induced DNA lesions are repaired extensively by nucleotide excision, and in agreement with a defect in this process, MCF-7/E6 and MCF-7/mu-p53 cells exhibited a reduced ability to repair a CDDP-damaged chloramphenicol acetyltransferase-reporter plasmid transfected into the cells Therefore, we attributed the increased CDDP sensitivity of MCF-7 cells with disrupted p53 to defects in G1 checkpoint control, nucleotide excision repair, or both The G2 checkpoint inhibitor pentoxifylline exhibited synergism with CDDP in killing MCF-7/E6 cells but did not affect sensitivity of the control cells Moreover, pentoxifylline inhibited G2 checkpoint function to a greater extent in MCF-7/E6 than in the parental cells These results suggested that, in the absence of p53 function, cancer cells are more vulnerable to G2 checkpoint abrogators Our results show that a combination of CDDP and pentoxifylline is capable of synergistic and preferential killing of p53-defective tumor cells that do not readily undergo apoptosis

Molecular Insights into Cancer Invasion: Strategies for Prevention and Intervention

Abstract: The diagnosis and treatment of solid tumors usually begins at a late stage when most patients already have occult or overt metastasis. Many years of cancer progression precede diagnosis of most solid tumors. Novel noncytotoxic therapeutics may be specially suited for administration during this interval. An important window of intervention can be defined as the period during which transition from a hyperproliferative state to acquisition of the capacity for invasion and metastasis occurs. Investigation of the molecular basis of invasion is uncovering strategies for delaying progression of preinvasive carcinoma and treatment of primary tumors and established metastasis. Although tumor cell invasion might not be rate limiting for the growth of metastasis, anti-invasive agents can block tumor angiogenesis and thereby indirectly block metastasis growth. Two classes of molecular anti-invasion targets exist: (a) cell surface and extracellular proteins, which mediate sensing, adhesion, and proteolysis; and (b) signal transduction pathways, which regulate invasion, angiogenesis, and proliferation. Both categories of targets yield treatment approaches that are now being tested in the clinic. Metalloproteinase inhibitors, such as BB94, are based on the recognition that metalloproteinases play a necessary role in invasion and angiogenesis. The orally active signal transduction inhibitor carboxyamidotriazole modulates non-voltage-gated calcium influx-regulated signal pathways and reversibly inhibits tumor invasion, growth, and angiogenesis. Blockade of invasion, angiogenesis, or cellular signal pathways is likely to generate a cytostatic, rather than a cytotoxic effect. Cytostatic therapy constitutes an alternative paradigm for clinical translation that may complement conventional cytotoxic therapy. For patients with newly diagnosed solid tumors, long-term cytostatic therapy could potentially create a state of metastasis dormancy or delay the time to overt relapse following cytotoxic agent-induced remission. Clinical toxicity and pharmacology using oral cytostatic agents in phase I trials and in adjuvant settings will provide an important foundation for the translation of this approach to the preinvasive carcinoma period.

Reduced expression of proapoptotic gene BAX is associated with poor response rates to combination chemotherapy and shorter survival in women with metastatic breast adenocarcinoma.

Abstract: Bax is a homologue of Bcl-2 that promotes apoptosis. Bax protein levels were assessed by immunohistochemical methods in primary tumors derived from 119 women with metastatic breast cancer. These patients had received combination chemotherapy either with a once a month dosage schedule or in 4 weekly divided doses. The BAX immunostaining results were retrospectively compared with overall survival, time to tumor progression (TTP), and response, as well as several laboratory markers. Normal breast epithelium and in situ carcinomas immunostained positively for Bax. Marked reductions in Bax immunostaining were observed in 40 (34%) of 119 evaluable tumors. Reduced Bax correlated with shorter overall survival (median, 8.1 versus 15.7 months; P = 0.04), faster TTP (median, 2.0 versus 6.3 months; P = 0.009), and failure to respond (complete response, partial responses; 6% versus 42%, P = 0.01) in the subgroup of patients who received divided dose therapy. Reduced Bax immunostaining was not significant in the monthly dose group. When the two groups were combined, however, reduced Bax was significantly correlated in univariate analysis with failure to respond (21 versus 43% achieving complete response or partial response; P = 0.02), faster TTP (median, 3.7 versus 9.0 months; P = 0.02), and shorter survival (median, 10.7 versus 17.1 months; P = 0.04). Bax immunostaining was not significantly correlated with tumor histology, S-phase fraction, aneuploidy, p53 HER2, or cathepsin D, but was positively associated with Bcl-2 (P = 0.005). In multivariate analysis (Bax, tumor grade, and treatment group), reduced Bax was strongly associated with faster TTP (P ≅ 0.009) and shorter survival (P ≅ 0.001). Although highly preliminary, the finding suggest that loss of Bax immunostaining represents a novel prognostic indicator of poor response to chemotherapy and shorter survival in women with metastatic breast cancer, and raise the possibility that the subgroup of women with Bax-negative tumors may benefit from more aggressive therapy.

The CAG and GGC Microsatellites of the Androgen Receptor Gene Are in Linkage Disequilibrium in Men with Prostate Cancer

Abstract: The androgen receptor genotype was determined in the white blood cell DNA of 45 African-American, 39 non-Hispanic white, and 39 Asian (Chinese, Japanese) normal subjects and 68 patients with prostate cancer (57 whites), all of whom were residents of Los Angeles County. For each subject, we measured the number of repeats in the polymorphic CAG and GGC microsatellites of exon 1 of the androgen receptor gene. In normal subjects, the distributions of CAG and GGC microsatellites differed significantly among the races (two-sided P = 0.046 and CAG alleles ( GGC allele with 16 repeats; the comparable values for intermediate-risk whites and low-risk Asians were 57% and 70%, respectively. Consistent with the interracial variation in CAG and GGC distributions, there was an excess of white patients with P = 0.08). We observed no association (linkage) between the two microsatellites among normal subjects. On the other hand, there was a statistically signifiant negative association between the numbers of CAG and GGC repeats among the prostate cancer patients studied (two-sided P = 0.008). Among the 47 subjects with short CAG alleles ( GGC alleles (>16 repeats) whereas only 15% of the 20 subjects with long CAG alleles (≥22 repeats) had long GGC alleles. Overall, our data suggest a possible association between CAG and GGC microsatellites of the androgen receptor gene and prostate cancer development.

APC binds to the novel protein EB1

Abstract: Mutations of the APC gene play a critical role in both sporadic and familial forms of colorectal cancer. The vast majority of these mutations result in the loss of the carboxyl terminus of the protein. To further elucidate the function of APC, we searched for cellular proteins that associate with its carboxyl terminus. One million human cDNA clones were screened with the use of the interaction trap two-hybrid system, and 67 clones were found to have a phenotype suggestive of an APC-interacting protein. Nucleotide sequence analysis revealed that 48 of these clones were derived from a single novel gene named EB1. The association of APC and EB1 proteins was confirmed with in vitro Binding assays. mAbs against EB1 were then produced and used to demonstrate the association of APC and EB1 in vivo. The EB1 gene was predicted to encode a 268-amino acid protein without significant homology to proteins with known function. However, searches of nucleotide databases did identify evidence for at least two related human genes and a yeast homologue. This conservation suggests an essential function for EB1 that might provide clues to the mechanism through which APC suppresses colonic neoplasia.

Sigma-1 and sigma-2 receptors are expressed in a wide variety of human and rodent tumor cell lines

Abstract: Thirteen tumor-derived cell lines of human and nonhuman origin and from various tissues were examined for the presence and density of sigma-1 and sigma-2 receptors. Sigma-1 receptors of a crude membrane fraction were labeled using [3H](+)-pentazocine, and sigma-2 receptors were labeled with [3H]1,3-di-o-tolylguanidine ([3H]DTG); in the presence or absence of dextrallorphan. [3H](+)-Pentazocine-binding sites were heterogeneous. In rodent cell lines (e.g., C6 glioma, N1E-115 neuroblastoma, and NG108-15 neuroblastoma x glioma hybrid), human T47D breast ductal carcinoma, human NCI-H727 lung carcinoid, and human A375 melanoma, [3H](+)-pentazocine bound to high- and low-affinity sites with Kd1 = 0.67-7.0 nM, Bmax1 = 25.5-108 fmol/mg protein, Kd2 = 127-600 nM, and Bmax2 = 942-5431 fmol/mg protein. However, [3H](+)-pentazocine bound to a single site in other cell lines. In human U-138MG glioblastoma, SK-N-SH neuroblastoma, and LNCaP.FGC prostate, Kd = 28-61 nM and Bmax = 975-1196 fmol/mg protein, whereas in ThP-1 leukemia Kd = 146 nM and Bmax = 1411 fmol/mg protein. The sigma-1-like nature of [3H](+)-pentazocine-binding sites was confirmed by competition studies which revealed high affinity for haloperidol and enantioselectivity for (+)-pentazocine over (-)-pentazocine. Interestingly, human MCF-7 breast adenocarcinoma showed little or no specific binding of [3H](+)-pentazocine, suggesting the absence of sigma-1 receptors in this cell line. All cell lines examined expressed a high density of sigma-2 receptors with Kd values for [3H]DTG ranging from 20 to 101 nM and Bmax values of 491 to 7324 fmol/mg protein. Competition studies indicated possible heterogeneity of sigma-2 receptors. While sites labeled by [3H]DTG in all cell lines tested exhibited affinity for haloperidol and preference for (-)-pentazocine over the (+)-enantiomer, human cell lines generally showed 4- to 7-fold lower affinity for haloperidol and approximately 10-fold lower affinity for (-)-pentazocine compared with the rodent cell lines. The high density of sigma-1 and sigma 2-binding sites in these cell lines suggests important cellular functions in cancer, as well as potential diagnostic utility for tumor-imaging agents which target sigma sites. These cell lines may be useful as model systems in which to study the functions of sigma sites in normal tissues, as well as their possible role in tumor biology.