Showing papers by "Eppley Institute for Research in Cancer and Allied Diseases published in 1993"
TL;DR: Investigation of the expression of annexin II in pancreatic adenocarcinoma cells and primary tumors finds that it has a role in cell proliferation and its regulation is altered in Pancic cancer.
Abstract: Annexin II is a calcium and phospholipid binding protein and a substrate for protein-tyrosine kinases. Recent investigations have revealed involvement of annexin II in DNA synthesis and cell proliferation. Increased levels of annexin II are observed in cancer cells and tissues. To investigate the expression of annexin II in pancreatic adenocarcinoma cells and primary tumors, we measured the levels of annexin II mRNA and protein in normal human pancreas, five established human pancreatic adenocarcinoma cell lines, three primary pancreatic cancers and one metastatic tumor. All five cell lines examined had 5- to 15-fold higher levels of annexin II as compared to normal pancreas. Significant elevations (2- to 8-fold) of annexin II expression were observed in the three primary pancreatic tumors and one metastatic tumor examined. Immunocytochemical analysis indicates that the increased expression of annexin II is limited to proliferating ductular adenocarcinoma, and annexin II expression co-localizes with cells that express PCNA. In normal pancreas, annexin II expression is seen in ductal and ductular cells and no expression is seen in acinar or islet cells. We conclude from these findings that annexin II has a role in cell proliferation and its regulation is altered in pancreatic cancer.
131 citations
TL;DR: The identification and quantitation of the depurination adducts of BP were reported, which were similar both qualitatively and quantitatively with native or denatured DNA, as well as the major stable adduct formed via the diolepoxide pathway, BP diol bound at C-10 to the 2-amino of dG (BPDE-10-N2dG).
Abstract: The DNA adducts of benzo[a]pyrene (BP) formed in vitro were previously identified and quantitated. In this paper, we report the identification and quantitation of the depurination adducts of BP, 8-(benzo[a]pyren-6-yl)guanine (BP-6-C8Gua), BP-6-N7Gua, and BP-6-N7Ade, formed in mouse skin by one-electron oxidation, as well as the major stable adduct formed via the diolepoxide pathway, BP diolepoxide bound at C-10 to the 2-amino of dG (BPDE-10-N2dG). Identification of the depurination adducts was achieved by HPLC and fluorescence line narrowing spectroscopy. The depurination adducts, BP-6-C8Gua (34%), BP-6-N7Gua (10%), and BP-6-N7Ade (30%), constituted 74% of the adducts found in mouse skin 4 h after treatment with BP. The stable adduct BPDE-10-N2dG accounted for 22% of the adducts. Treatment of the skin with BP-7,8-dihydrodiol or BP diolepoxide yielded almost exclusively the stable adduct BPDE-10-N2dG. When BP or BP-7,8-dihydrodiol was bound to RNA or denatured DNA in reactions catalyzed by rat liver microsomes, no depurination adducts were detected. The profiles of stable adducts were similar both qualitatively and quantitatively with native or denatured DNA. With activation of BP by horseradish peroxidase, the profiles of stable adducts differed with native and denatured DNA. The total amount of adducts with denatured DNA was only 25% of the amount detected with native DNA. No depurination adducts were detected with denatured DNA or RNA in the peroxidase system.(ABSTRACT TRUNCATED AT 250 WORDS)
126 citations
TL;DR: The comparison of in vitro and intracellular hCG-beta folding and hCG subunit assembly indicates that the assisted folding and assembly pathway that occurs in cells, where proteins such as PDI play a role, differs only in rate but not in the order of disulfide bond formation or in the precursor-product relationships among the folding intermediates.
76 citations
TL;DR: Nine human exocrine pancreatic adenocarcinomas were examined by serial sectioning and double- and triple-labeled immunohistochemical techniques with antibodies against chromogranin A, insulin, islet amyloid polypeptide, glucagon, somatostatin, pancreatic polypePTide, serotonin, pancreastatin, and neuron-specific enolase, suggesting abnormalities may contribute to the impaired glucose tolerance found in six of these patients.
Abstract: Nine human exocrine pancreatic adenocarcinomas were examined by serial sectioning and double- and triple-labeled immunohistochemical techniques with antibodies against chromogranin A, insulin, islet amyloid polypeptide, glucagon, somatostatin, pancreatic polypeptide, serotonin, pancreastatin, and neuron-specific enolase. The results were correlated with the stage of the disease, histologic characteristics of the tumors, and survival of the patients. Cells immunoreactive with most or all of the antibodies were found in all nine cases. Abnormal co-location of some hormones in the same cell and the lack of normal co-location of other hormones were found. Endocrine cells also were identified in the invasive regions of the cancer, including perineural spaces. Abnormality in the production and release of the peptide was indicated not only in the endocrine cells of exocrine cancer, but also in the islets near the cancer. Patients whose cancer contained many endocrine cells seemed to survive longer than those with tumors containing fewer endocrine cells. The overall data suggested that the observed abnormalities may contribute to the impaired glucose tolerance found in six of these patients.
66 citations
TL;DR: A comparison of the methylation patterns of MeOSO2(CH2)n-Lex as a function of tether length provides an insight into Lex sequence and orientational preferences.
Abstract: A series of sulfonate esters that are attached to a noncationic minor-groove-binding N-methylpyrrole dipeptide (Lex) related to netrospin have been synthesized. The compounds prepared differ in two respects: (1) the length [(CH2)2 vs (CH2)8] of the tether between the DNA affinity binding portion of the molecule and the sulfonate ester and (2) whether a methyl group [MeOSO2(CH2)n-Lex] or the dipeptide including the aliphatic tether [MeSO2O(CH2)n-Lex] is covalently transferred to the DNA. The DNA-cleavage patterns of these bimolecular alkylating compounds have been mapped in 32P-end-labeled restriction fragments using neutral thermal hydrolysis and alkali treatment to expose single-strand breaks at bases with thermally labile modifications. In contrast to the alkylation of DNA by simple alkyl alkanesulfonate esters, that predominantly yield major-groove alkylation at N7-guanine, the modification of DNA by MeOSO2(CH2)n-Lex and MeSO2O(CH2)n-Lex occurs primarily at N3-adenine residues associated with previously footprinted Lex DNA affinity binding regions. The ratio for the formation of N3-methyladenine (minor groove) to N7-methylguanine (major groove) in calf thymus DNA is 1:7 for dimethyl sulfate, while only the former adenine product is observed with MeSO2O(CH2)n-Lex indicating the change in groove specificity. DNA cleavage by MeOSO2(CH2)n-Lex and MeSO2O(CH2)n-Lex is efficiently inhibited by the coaddition of distamycin; however, only the DNA damage generated by the latter is blocked by NaCl. As expected, increasing the length of the (CH2)n tether from n = 2 to n = 8 moves the alkylation site by 1-2 base pairs further from the affinity binding domain. Finally, a comparison of the methylation patterns of MeOSO2(CH2)n-Lex as a function of tether length provides an insight into Lex sequence and orientational preferences.
61 citations
TL;DR: The hypothesis that individual S-S bonds are involved in discrete steps in the hCG-beta folding pathway is supported.
56 citations
TL;DR: The results showed that, in comparison with NIH3T3 cells, bothras transfectants have increased sensitivity to the cytotoxic action of L-PHA, and suggest that a specific induction of GlcNAc-T V occurs after transfection with either the proto- or activated Ha-ras oncogenes, which is responsible for the increased β1-6 branching.
Abstract: Viral infection of cultured cells with transforming viruses causes an increase in cell-surface N-linked β1-6 (GlcNAcβ1-6Man) branching of complex-type oligosaccharides. Similar observations have been made after transfection of cells with activated oncogenes, which is associated with an induction of tumorigenic and metastatic properties. In this study, the effects of transfection of both activated and proto-Ha-ras oncogenes into NIH3T3 cells were analyzed. The results showed that, in comparison with NIH3T3 cells, bothras transfectants have increased sensitivity to the cytotoxic action of L-PHA. An increase in β1-6 branching and an increased level of N-acetylglucosaminyltransferase V (GlcNAc-T V), the enzyme which initiates the β1-6 branching were also observed. The levels of GlcNAc-T I and β1-4 Gal-T remained unchanged in activated Ha-ras transfected NIH3T3 cells. These data suggest that a specific induction of GlcNAc-T V occurs after transfection with either the proto- or activated Ha-ras oncogenes, which is responsible for the increased β1-6 branching previously observed. (Mol Cell Biochem122: 85–92, 1993)
50 citations
TL;DR: It appears that cell cycle and heat stress are two of the factors that influence cellular localization of p53 protein in both human and hamster pancreatic cancer cells.
Abstract: We compared the expression of p53 protein in four human pancreatic cancer cell lines (HPAF, CD11, CD18 and PANC-1) and four hamster pancreatic cancer cell lines (PC-1, PC-1.2, PC-1.0 and H2T) by the monoclonal antibodies PAb421 and PAb240. PAb421 reacted with all human pancreatic cancer cell lines but not with the hamster cells. PAb240, on the other hand, reacted with all human and hamster pancreatic cancer cell lines in immunoblotting and in immunocytochemistry. However, immunoprecipitation with PAb240 was detected only in human cell lines HPAF, CD11 and CD18 cells but not in PANC-1 or in any of the hamster cell lines. During exponential growth, immunoreactivity was detected mainly in the nucleus of PC-1, PC-1.2 and PANC-1 cells (nuclear type) and in both the nucleus and the cytoplasm of PC-1.0, H2T, HPAF, CD11 and CD18 cells (diffuse type). At the confluence, the expression of p53 was decreased in most of the human cell lines as was proliferative cell nuclear antigen. After incubation with 1 mM hydroxyurea, cells with nuclear p53 expression did not show an altered cellular distribution of p53 protein, whereas cells with a diffuse type of localization pattern showed an increase in the nuclear staining. On the other hand, cytoplasmic immunoreactivity was found in PC-1.0, PC-1, PC-1.2, HPAF, CD11 and CD18 cells that were treated with 100 ng/ml of nocodazole. After heat stress with 1 h incubation at 42 degrees C, p53 protein was detected in the cytoplasm and nucleolus of all cell lines. After 24-48 h incubation at 37 degrees C, this change in cellular distribution of p53 in response to heat stress was reverted to a preheat stress pattern. The overall results suggest that neither the p53 of PANC-1 nor the hamster pancreatic cancer cell lines are immunoprecipitated with the PAb240. It appears that cell cycle and heat stress are two of the factors that influence cellular localization of p53 protein in both human and hamster pancreatic cancer cells.
32 citations
TL;DR: The concentration-dependence of repression by DNA oligonucleotides provides triple-helix inhibition constant (Ki) estimates of approximately 2 x 10(-7) M for both purine motif and pyrimidine motif DNA complexes, which suggest prospects for, and constraints on, natural and artificial RNA-based repressors.
Abstract: We are interested in creating artificial gene repressors based on duplex DNA recognition by nucleic acids rather than polypeptides. An in vitro model system involving repression of bacteriophage T7 RNA polymerase initiation has been employed to demonstrate that certain DNA oligonucleotides can repress transcription by site-specific triple-helix formation at two kinds of homopurine operator sequences [Maher, L. J., III, (1992) Biochemistry 31, 7587-7594]. Recognition in the purine motif is based on antiparallel oligonucleotide binding (G.G.C and T.A.T triplets). Recognition in the pyrimidine motif is based on parallel oligonucleotide binding (C+.G.C and T.A.T base triplets). Using this system, we report that the concentration-dependence of repression by DNA oligonucleotides provides triple-helix inhibition constant (Ki) estimates of approximately 2 x 10(-7) M for both purine motif and pyrimidine motif DNA complexes. RNA oligonucleotides are shown to repress promoters overlapping pyrimidine motif operators (Ki = 6 x 10(-7) M), but not purine motif operators. Although competent to hybridize to complementary single strands, RNA oligonucleotides fail to bind the purine motif operator. Partial substitution of deoxyribose residues tends to rescue repressor activity by RNA oligonucleotides in the purine motif. These results suggest prospects for, and constraints on, natural and artificial RNA-based repressors.
30 citations
Journal Article•
24 citations
TL;DR: The results indicate that a combination of reagents which report electronic and steric perturbations can be a useful approach to monitor DNA mismatches and bulges.
Abstract: The detection of abnormal DNA base pairing arrangements and conformations is chemically probed in synthetic 32P-end-labeled deoxyribonucleotide oligomers using N-methyl-N-nitrosourea (MNU) and 2,12,-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]heptadeca-1 -[17],2,11,13,15 pentaene-Ni (II) (Ni-complex) with KHSO5. The DNA targets studied are single-stranded (s-s) DNA, double-stranded (d-s) DNA, d-s DNA with G-G, G-A and G-T mismatches, d-s DNA with a single bulged G and d-s DNA with two bulged G's. The effect of the non-Watson--Crick structures on the formation of N7-methylguanine (N7-MeG) by MNU and the oxidation of G by Ni-complex is reported along with the Tm's and circular dichroism spectra of the different duplex oligomers. The results for MNU and Ni-complex show that the qualitative and quantitative character of the cleavage patterns at a G3 run change with the nature of the abnormal base pairing motif. Based on the DNA substrates studied, the results indicate that a combination of reagents which report electronic and steric perturbations can be a useful approach to monitor DNA mismatches and bulges.
TL;DR: The results suggest that the efficiency of artificial repressors based on triple-helix formation may be limited by transcriptional activity in the gene control region.
Abstract: We have characterized triple-helix-mediated inhibition of an artificial bacteriophage promoter with respect to relief of inhibition by incoming RNA polymerases that initiate upstream or downstream from the operator sequence. Whereas oligonucleotide-directed triple-helix formation inhibits the test promoter, promoter activity is restored when the triple-helical complexes are disrupted by transcription of either strand of the homopurine operator sequence. The degree of relief from inhibition is related to the frequency of operator transcription. These observations demonstrate that this artificial repressor-operator complex is subject to antagonism by cis elements (other promoters) acting at a distance. Such antagonism might also arise between certain natural transcriptional control regions. Our results suggest that the efficiency of artificial repressors based on triple-helix formation may be limited by transcriptional activity in the gene control region.
TL;DR: A wide range of new developments in the field of gene targeting are discussed with a focus on issues to be considered by those planning to use this new technology and some of the lessons learned from recent gene targeting studies are examined.
Abstract: Over 1500 mouse mutants have been identified, but few of the genes responsible for the defects have been identified. Recent developments in the area of gene targeting are revolutionizing the field of mouse genetics and our understanding of numerous genes, including those thought to be involved in cell proliferation and differentiation. Gene targeting was developed as a method for producing a predetermined mutation in a specific endogenous gene. Advances in the design of targeting vectors and in the use of embryonic stem cells have permitted the production of numerous mutant mice with null mutations in specific genes. These mutant mice will be critical for investigating the in vivo functions of many genes that have been cloned in recent years. This review discusses a wide range of new developments in the field of gene targeting with a focus on issues to be considered by those planning to use this new technology. It also examines some of the lessons learned from recent gene targeting studies and discusses different applications of the technology that are likely to generate scores of new animal models for a wide range of human diseases.
TL;DR: In vitro studies show that the minor groove binding CENU-lex's afford a lower level of sister chromatid exchange (SCE) in 9L cells that are sensitive to CenU, and this results are consistent with the novel minor groove adduction being a 'detoxification' pathway for the CEN U-lex' since this lesion is formed at the expense of the cytotoxic major groove interstrand crosslink.
Abstract: Chloroethylnitrosoureas (CENU) are clinically important chemotherapeutic agents whose mechanism of action involves the formation of interstrand DNA crosslinks via an ethane bridge between N1-G and N3-C. CENU generally alkylate G at the N7- and O6-positions, with the latter lesion being the precursor to the interstrand crosslink. In previous studies, we reported the synthesis of CENU appended by a C2H4 linker to the N-terminus of DNA minor groove binding dipeptides (lex, information reading peptides) based on N-methylpyrrole-carboxamide subunits. Because of the dipeptide structure, these CENU-lex's react with DNA at adenines associated with lex equilibrium binding sites. No other CENU has been reported to yield A adducts. The biological evaluation of these CENU-lex's show that they are somewhat less cytotoxic than their simpler counterparts. In addition, in vitro studies show that the minor groove binding CENU-lex's afford a lower level of sister chromatid exchange (SCE) in 9L cells that are sensitive to CENU. There is no difference between CENU-lex in SCE induction in 9L-2 cells that are resistant to CENU. Formation of DNA interstrand crosslinks from the CENU-lex's is lower than for their nonaffinity binding analogs in low ionic strength buffer, but similar in the same buffer containing 200 mM NaCl. Salt inhibits crosslinking for all CENU, but distamycin, a competitive inhibitor of lex minor groove binding, uniquely enhances crosslinks for the CENU-lex's. These results are consistent with the novel minor groove adduction being a 'detoxification' pathway for the CENU-lex's since this lesion is formed at the expense of the cytotoxic major groove interstrand crosslink.
TL;DR: The pathogenetic mechanism) responsible for SIM or FIM remain unknown mainly owing to the limited number of cases and the difficulties in establishing a precise diagnosis.
Abstract: Infectious mononucleosis (IM), caused by primary infection of Epstein-Barr virus (EBV), is a self-limiting benign lymphoproliferative disease.1 Rare cases, however, develop severe or fatal IM (SIM or FIM) either sporadically or with X-linked lymphoproliferative disease (XLP).1,2 The pathogenetic mechanism) responsible for SIM or FIM remain unknown mainly owing to the limited number of cases and the difficulties in establishing a precise diagnosis.
TL;DR: The data suggest that the induction of PRL mRNA by EGF may require the induced synthesis of an intermediary regulatory protein, and this hypothesis is tested in GH4C1 rat pituitaries.
TL;DR: The adducts of 6-FBP and 6-CH3BP appear to be formed mostly through the diolepoxide pathway, whereas those of 7,8-dihydrodiol appear to arise mostly via one-electron oxidation.
Abstract: Studies of benzo[a]pyrene (BP) and selected derivatives are part of the strategy to elucidate mechanisms of tumor initiation by polycyclic aromatic hydrocarbons. Substitution of BP at C-6 with fluorine to form 6-fluorobenzo[a]pyrene (6-FBP) or a methyl group to form 6-methylbenzo[a]pyrene (6-CH3BP) decreases tumorigenicity compared to BP. BP, 6-FBP, and 6-CH3BP formed adducts with DNA when (1) they were activated by 3-methylcholanthrene-induced rat liver microsomes, (2) they were activated by horseradish peroxidase (HRP), (3) their 7,8-dihydrodiols were activated by microsomes, or (4) the radical cation of BP, 6-FBP, or 6-CH3-BP was directly reacted with DNA. With microsomes, 6.5 mumol of [3H]6-FBP/mol of DNA-P and 10 mumol of [14C]6-CH3BP/mol of DNA-P were bound vs 15 mumol of [3H]BP. With microsomes, two major 6-FBP adducts and some minor adducts were obtained. One major adduct coincided with that from 6-FBP-7,8-dihydrodiol. With microsomes, the minor 6-FBP adducts coincided with the adducts obtained from 6-FBP radical cation plus DNA and the major adduct of HRP-activated 6-FBP. With microsomes, 6-CH3BP showed adducts similar to some formed with HRP and one from 6-CH3BP radical cation. 6-CH3BP-7,8-dihydrodiol produced a small amount of one adduct that did not coincide with any from 6-CH3BP. The adducts of 6-FBP appear to be formed mostly through the diolepoxide pathway, whereas those of 6-CH3BP appear to arise mostly via one-electron oxidation.
TL;DR: The nt sequence of 2531 bp of the rOAT domain flanking the promoter revealed several putative promoter/enhancer elements in positions analogous to the human OAT gene, numerous AGGTCA-like motifs related to the binding sites for the estrogen and thyroid hormone receptors, and multiple motifs resembling a putative regulatory element associated with genes encoding enzymes of the urea cycle.
TL;DR: The results suggest that NaB stimulates the differentiation of the hamster and human pancreatic cancer cell lines and increases or induces the expression of some tumor-associated antigens.
Abstract: The effects of sodium butyrate (NaB) on the growth, morphology, and expression of blood group A, Lewis(a), and CA 19-9 antigen in the hamster pancreatic cancer cell lines, PC-1 (well differentiated) and PC-1.0 (poorly differentiated), and of blood group A, DU-PAN-2, and CA 19-9 antigens in four human pancreatic cancer cell lines, HPAF and CD11 (well differentiated) and CD18 and PANC-1 (poorly differentiated), were examined. NaB inhibited the growth of all cell lines and induced cell enlargement, an increase in secretory material, microfilaments, and pseudopodia. NaB stimulated the production of blood group A antigen in PC-1.0 cells dose dependently, but no change in the expression of this antigen was observed in the human cell lines. However, NaB treatment increased the presence of cells positive for CA 19-9 in PANC-1 but not in the remaining cell lines, none of which reacted with the anti-CA 19-9 antibody before or after NaB treatment. Untreated PANC-1 cells did not produce either blood group A or DU-PAN-2 antigen, but expressed these antigens after NaB treatment in a dose-dependent manner. The results suggest that NaB stimulates the differentiation of the hamster and human pancreatic cancer cell lines and increases or induces the expression of some tumor-associated antigens.
TL;DR: Results using molecular genetic techniques are reported to provide information as to the relative risks of EBV negative males and potential carrier females in ten families wherein a single male had died of IM.
Abstract: The Epstein-Barr virus (EBV)-induced diseases of males with X-linked lymphoproliferative disease (XLP) include fatal infectious mononucleosis (IM), non-Hodgkin lymphoma (ML), agammaglobulinemia, and aplastic anemia. These phenotypes also occur as sporadic cases in families, and EBV seronegative males in these families must be considered at risk for XLP until they seroconvert normally to EBV. Given that 50% of males inheriting the defective XLP gene die following primary EBV infection, it is vital that they be identified pre-EBV infection. Here we report result using molecular genetic techniques to provide information as to the relative risks of EBV negative males and potential carrier females in ten families wherein a single male had died of IM. © 1993 Wiley-Liss, Inc.
TL;DR: The potential of the culture environment to alter the responsiveness to estrogenic stimuli by altering the properties of the ER is illustrated by showing that GH4C1 cells maintained at low density expressed fewer ER than cells cultured at high density.
TL;DR: It is argued strongly that other factors, in addition to high-affinity FGF receptor number, are important in determining sensitivity of cells of bFGF-saporin, which is cytotoxic for CHO-KI cells, but not for embryonal carcinoma cells.
Abstract: Fibroblast growth factors (FGFs) have been implicated in a number of proliferative lesions, including malignant tumor growth and vascularization. As a result, cytotoxic agents that target cell surface FGF receptors are currently under investigation. Previous reports have shown that conjugation of basic FGF with the ribosome inactivator, saporin, results in a potent cytotoxin specific for cells bearing high-affinity FGF receptors. In this report, we have used this FGF receptor-dependent cytotoxin to study receptor interactions at the surface of embryonal carcinoma cells, which express low numbers of high-affinity FGF receptors. The growth of three embryonal carcinoma cell lines and one embryonic stem cell line was shown to be inhibited by bFGF-saporin, suggesting that these cells are able to bind and internalize FGF through high-affinity FGF receptors. In addition, we determined that the responses of these cells to bFGF-saporin are qualitatively different than the responses of CHO-KI cells, which also exhibit low numbers of high-affinity FGF receptors. Specifically, pretreatment with bFGF-saporin reduces the cloning efficiency of CHO-KI cells 8- to 10-fold, whereas bFGF-saporin has little or no effect on the cloning efficiency of embryonal carcinoma cells. This finding suggests that bFGF-saporin is cytotoxic for CHO-KI cells, but not for embryonal carcinoma cells. Thus, our findings argue strongly that other factors, in addition to high-affinity FGF receptor number, are important in determining sensitivity of cells of bFGF-saporin.
01 Jan 1993
TL;DR: More than 70% of pancreatic carcinoma contains endocrine cells, some in a pattern consistent with the mixed-cell tumors of Cubilla and Fitzgerald, and Kloppel and Heitz do not classify these tumors as separate entities, and rightly so.
Abstract: Classification of tumors is important for understanding the tumor histogenesis and prognosis. Since 1836, when pancreatic cancer was first described [1], progress has been made in pancreatic cancer morphology. However, there are still inconsistencies in the description and classification of pancreatic tumors, mostly because of the lack of information on the natural history of the disease. The silent course of the disease and its late clinical manifestation and diagnosis are contributing factors, as are the insufficient availability of tissues (biopsy, autopsy), the technique in preparation of the specimen, methods of histological examination (including the number of sections taken for evaluation), and personal experience. Therefore, some of the classifications have been either simplified, exaggerated by details or are incomplete [2–10]. For example, the classification by Cubilla and Fitzgerald [5] and Sommers and Meissner [10] include mixed duct-islet, duct-islet-acinar and acinar-islet tumors. In our experience and that of others [11–17], more than 70% of pancreatic carcinoma contains endocrine cells, some in a pattern consistent with the mixed-cell tumors of Cubilla and Fitzgerald (Figs. 1, 2). Therefore, Kloppel and Heitz [18] do not classify these tumors as separate entities, and rightly so. The same applies for the mixed acinar-islet and carcinoid-islet cell tumors that neither we nor other investigators have encountered in their material, except for rare tumors that contain both zymogen and endocrine granules [17]. Such tumors should not be regarded as mixed tumors but rather reflect altered differentiation.
TL;DR: The results suggest that A-transferase is activated during nitrosamine-induced pancreatic carcinogenesis, which results in the neoexpression of blood group-A antigen.
Abstract: Ductal adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine treatment in Syrian hamsters produce blood group-A antigen, which is not present in normal hamster pancreas. To understand the underlying mechanism of A antigen neoexpression in pancreatic cancer cells, we examined the activity of UDP-GalNAc:Fuc alpha 1-2Gal alpha 1-3GalNAc transferase (A-transferase), the enzyme responsible for blood group-A antigen production. The specific activity of A-transferase in the pancreatic cancers was approximately 8 nmol/mg protein/h in membrane preparations, 0.3 nmol/mg protein/h in whole cell extracts, and undetectable in normal hamster pancreas. Significant A-transferase activity was found in normal tissues expressing blood group-A antigen. Although both normal (gastric antrum, colon) and pancreatic cancer cells showed similar enzymatic characteristics (optimal pH, substrate affinity, optimal [Mn2+]), there was a difference in the requirement for divalent cations. The A-transferase in cancer cells showed a more stringent requirement for Mn2+. These results suggest that A-transferase is activated during nitrosamine-induced pancreatic carcinogenesis, which results in the neoexpression of blood group-A antigen. The difference in divalent cation requirements between A-transferase activities of cancer and normal cells may indicate that there are multiple A-transferases present in hamster tissues.
TL;DR: Data show that methylation was a more mutagenic lesion than hydroxypropylation in BHP and BOP, and there was no evidence of a correlation between mutagenicity and the formation of O6alkylG.
Abstract: N-Nitrosobis (2-hydroxypropyl) amine (BHP) and N-nitrosobis (2-oxopropyl) amine (BOP) require metabolism to be carcinogenic and mutagenic. This metabolism produces hydroxypropylating and methylating alkylating species. To measure the effects of these species, we compared the action of direct-acting model compounds that are hydroxypropylating or methylating agents with those of BHP and BOP. Mutagenicity in V79 cells and the alkylation of V79 cell DNA were measured. The model compounds were ethyl-N-nitroso (2-oxopropyl) carbamate (NOPC), a methylating agent, and its 2-hydroxypropyl congener (NHPC), a hydroxypropylating agent. BHP and BOP were metabolized by hepatocytes from male Syrian hamsters. At the highest dose (2 mM) BOP produced 12 times more mutants than BHP but only 2.5 times more O6methylguanine (O6MeG) than BHP. When a pancreas duct homogenate was used, 87 (BOP) and six (BHP) mutants/106 survivors were measured. When hepatocytes (not a homogenate) were used to metabolize BOP, 351 μmol O6MeG/mol guanine (G) and 39 μmol O6 (2-hydroxypropyl) G (O6HpG)/mole G were found in V79 DNA. When a pancreas duct homogenate was used BHP produced O6HpG (65 μmol/mol G) and BOP O6MeG (20 μmol/mol G). NOPC produced five times more mutants than NHPC, over the range of doses. At the highest dose (10 μM) it produced less (70%) O6alkylG than NHPC. These data show that methylation was a more mutagenic lesion than hydroxypropylation. There was no evidence of a correlation between mutagenicity and the formation of O6alkylG. ©1993 Wiley-Liss, Inc.