Masami Fujita

Bio: Masami Fujita is an academic researcher from Osaka University. The author has contributed to research in topics: Ovarian cancer & Adenocarcinoma. The author has an hindex of 33, co-authored 88 publications receiving 3135 citations.

Molecular Evidence That Most but not All Carcinosarcomas of the Uterus Are Combination Tumors

Abstract: The pathogenesis of carcinosarcoma is still a subject of controversy. In the present study, molecular techniques were applied to determine the pathogenesis of uterine carcinosarcomas. The patterns of chromosome X inactivation were analyzed, targeting a portion of exon 1 of the human androgen receptor (HUMARA) in malignant epithelial and mesenchymal components. The presence of p53 and K-ras mutations were also analyzed. H&E-stained sections of paraffin-embedded, formalin-fixed tissues were microdissected to obtain both epithelial and nonepithelial lesions from 25 carcinosarcomas, and DNAs were extracted by proteinase K digestion. Following treatment with methylation-sensitive restriction endonuclease (HhaI or HpaII), PCR amplification was performed using nested primers targeted to the HUMARA locus. Mutations in the p53 gene and K-ras gene were found in eight (32%) and six (24%) tumors, respectively. The patterns of chromosome X inactivation were different between the carcinomatous and sarcomatous components of three carcinosarcomas, indicating that these three tumors represent collision tumors. By contrast, the patterns of chromosome X inactivation, K-ras sequence, and p53 sequence were identical in both carcinomatous and sarcomatous components in 21 carcinosarcomas, indicating that these 21 tumors represent combination tumors. One case produced equivocal results that precluded determination of whether it represented a collision or combination tumor. These observations show that although most carcinosarcomas are combination tumors, some develop as collision tumors. The determination of histogenesis in individual cases of carcinosarcoma using molecular markers may be worthwhile, because the result could help predict the prognosis of individual cases and help guide clinical management.

Alterations of the p53 gene in human primary cervical carcinoma with and without human papillomavirus infection.

Abstract: A previous report using cervical carcinoma cell lines suggests that the inactivation of two tumor suppressor gene products, p53 and pRB, either by complex formation with the E6 and E7 proteins of oncogenic human papillomaviruses (HPVs) or by mutation, may be an important step in cervical carcinogenesis (M Scheffner et al, Proc Natl Acad Sci USA, 88: 5523-5527, 1991) The present study was designed to clarify the association between p53 inactivation and infection with oncogenic HPVs in primary carcinomas of human uterine cervix We examined 36 primary cervical carcinomas for the presence of HPV DNAs by Southern blot analysis with probes specific for HPV-16, -18, -31, -33, -52, -56, and -58 HPV DNA sequences were detected in 19 of 36 tumors: 10 cases with HPV-16; 3 cases with -18; 3 cases with -58; 2 cases with -56; and one case with -52 The presence of HPV-16 and -18 in cervical carcinomas was further reexamined using polymerase chain reaction HPV DNA sequences were detected in an additional 10 cases: 9 cases with -16 and one case with -18 The inactivation of the p53 gene by allelic loss or by point mutation was also examined No allelic loss at the polymorphic site in codon 72 of the p53 gene was detected in any of 10 informative cases Missense point mutations in the highly conserved regions of the p53 gene were demonstrable as single-stranded conformational polymorphisms of polymerase chain reaction-amplified DNA fragments and subsequently identified by direct DNA sequencing Point mutations were detected in only two cases: one with an ATG----CTG transversion in codon 133 of exon 5, resulting in a Met----Leu substitution, and another with a CGG----TGG transition in codon 248 of exon 7, resulting in an Arg----Trp substitution Both tumors with point mutations in p53 genes were among 10 tumors which contained a small copy number of HPV-16 DNA sequences (1 copy of HPV/10(1) to 10(5) cells) detectable by polymerase chain reaction amplification but not by Southern blot analysis of genomic DNAs derived from the tumors None of 19 tumors with a large copy number of HPV DNA sequences detectable by Southern blot analysis (more than 1 copy of HPV/2 to 10 cells) nor any of 7 tumors with undetectable HPV DNA sequences contained p53 gene mutations in the regions examined(ABSTRACT TRUNCATED AT 400 WORDS)

Coexpression of the c-kit Receptor and the Stem Cell Factor in Gynecological Tumors

Abstract: The protooncogene c-kit encodes a transmembrane receptor-type tyrosine kinase which belongs to the beta-PDGER/CSF-1 receptor tyrosine kinase family. The interaction between c-kit receptor and its corresponding ligand, stem cell factor (SCF), has been suggested to be involved in embryogenesis as well as carcinogenesis via the autocrine/paracrine system. In the present study, cancer cell lines and normal/benign/malignant tissues of the human female genital tract were examined for the expression of both c-kit and SCF by Northern blot and immunohistochemical analyses. Two of 16 cell lines showed mRNA expression of both c-kit and SCF, while 2 and 12 cell lines expressed c-kit and SCF, respectively. In tissues, several cases of malignant tumors, including three cervical cancers, one ovarian cancer, and one ovarian immature teratoma, expressed mRNA of both c-kit and SCF. In normal tissues, squamous epithelium expressed SCF immunohistochemically, while c-kit protein was detected only in melanocytes. Some tissues of malignant tumors, one squamous cell carcinoma of the cervix, two small cell carcinomas of the cervix, two serous adenocarcinomas of the ovary, and two immature teratomas of the ovary, expressed both c-kit and SCF proteins immunohistochemically. It is also notable that c-kit protein was expressed only in malignant germ cells of dysgerminomas, while SCF was expressed in the connective tissues surrounding germ cells. The present study suggests that the c-kit/SCF system may play an important role in the carcinogenesis of the female genital tract.

Alterations of the p53 tumor suppressor gene and its association with activation of the c-K-ras-2 protooncogene in premalignant and malignant lesions of the human uterine endometrium

Abstract: We previously reported (T. Enomoto et al. , Cancer Res., 50: 6139–6145, 1990; T. Enomoto et al. , Cancer Res., 51: 5308–5314, 1991) a significant frequency of activating point mutations in codon 12 of the c-K- ras -2 protooncogene in endometrial adenocarcinoma and its premalignant precursor lesions (series 1 and 2). To reveal the role of the p53 tumor suppressor gene in the development of endometrial adenocarcinoma and to study the association of p53 alterations with K- ras activation, an additional 28 endometrial adenocarcinomas and an additional 11 premalignant atypical uterine hyperplasias (series 3), as well as 12 cases of endometrial adenocarcinoma (10 having K- or N- ras activation) and 2 cases of atypical hyperplasia from series 1 and 2, were screened for the presence of p53 alterations. Allelic loss, recognized at the polymorphic site in codon 72 of the p53 gene, was detected in 6 of 19 (32%) informative cases of endometrial adenocarcinoma and 1 of 4 (25%) informative cases of endometrial atypical hyperplasia by restriction fragment length polymorphism analysis and by single-strand conformation polymorphism analysis of polymerase chain reaction (PCR)-amplified DNA fragments. Mutations in the highly conserved regions of the p53 gene were detected by single-strand conformation polymorphism analysis of PCR-amplified DNA fragments. Mutations were found in 9 of 40 (23%) endometrial adenocarcinomas and 1 of 13 (8%) atypical hyperplasias that were studied. Mutations in p53 were significantly more frequently found in clinical grade 3 (G3) cancers (6 of 14, 43%) than in G1-G2 cancers (3 of 26, 12%) ( P = 0.033). Mutations were subsequently confirmed by direct sequencing. Single missense base substitutions were detected in 6 cases of endometrial carcinoma and in one case of atypical hyperplasia. Deletions of a single base and of 2 bases were each detected in single cases of endometrial carcinoma, and a single base insertion was found in a third case. Point mutations in K- ras were also identified in tumors of series 3 by direct sequencing of PCR-amplified DNA fragments of exons 1 and 2. Point mutations in codons 12 and 13 in K- ras were detected by direct sequencing of PCR-amplified DNA in 7 of 28 adenocarcinomas in series 3, but none were found in exon 2 (codons 59–63). The spectrum of point mutations in p53 in endometrial adenocarcinomas was almost identical to what we found in K- ras in series 1 and 2 and in series 3, suggesting the possible role of a mutagen that might be responsible for mutations in both K- ras and p53 . However, there was no correlation between the presence of p53 gene mutations and K- ras activation in these tumors. It appears that inactivation of p53 , as well as K- ras activation, plays a significant role in the development of endometrial adenocarcinoma. In contrast to K- ras activation, which commonly occurs as an early event, inactivation of p53 usually occurs as a later event in endometrial carcinogenesis, independently of K- ras activation.

A Frequent Alteration of p53 Gene in Carcinoma in Adenoma of Colon

Abstract: In general, colorectal carcinoma is thought to originate mainly from adenoma, and this pathway is called the adenoma-carcinoma sequence. Carcinoma in adenoma is an appropriate model for analysis of this mechanism, because adenoma and carcinoma tissues coexist in the same polyp and the carcinoma is thought to have originated from the surrounding adenoma. Expression of the p53 protein was analyzed in 36 cases of carcinoma in adenoma in the colon by immunohistochemistry using an anti-human p53 monoclonal antibody (PAb1801). Alterations of the p53 gene were analyzed by the polymerase chain reaction for microanalysis of normal mucosa, adenoma, and carcinoma from histological slides. Mutations were assessed by the polymerase chain reaction-single strand conformation polymorphism analysis and identified by DNA sequencing in some cases. Loss of heterozygosity was studied by polymerase chain reaction-restriction fragment length polymorphism analysis. Positive staining for p53 was detected in three (8%) of 37 adenomas and 20 (53%) of 38 focal carcinomas. One (7%) of 15 adenomas with mild dysplasia, three (14%) of 22 adenomas with moderate dysplasia, and 16 (42%) of 38 focal carcinomas had a mutation in exon 5 through exon 8 of the p53 gene. As for allelic loss in the p53 gene locus, only one adenoma with moderate dysplasia had loss of heterozygosity, whereas six (40%) of 15 focal carcinomas had loss of heterozygosity. Of those tumors (3 of 37 adenomas and 20 of 38 focal carcinomas) that reacted with PAb1801, 78% (18 of 23) showed genetic alterations. Among 52 tumors which showed negative staining, five tumors had a p53 mutation and four of them were nonsense mutations. Putting all of these results together, 71% (24 of 34) of the cases underwent p53 gene and protein alterations during the conversion from adenoma to focal carcinoma. These data clearly indicate that genetic alterations of p53 are involved mainly in the malignant transformation from adenoma to focal carcinoma in colon carcinogenesis. In addition, some cases show heterogeneity of the p53 gene in carcinoma in adenoma of the colon. There may be other pathways than p53 responsible for malignant change in the colon.

Targeting the phosphoinositide 3-kinase pathway in cancer.

Abstract: The phosphoinositide 3-kinase (PI3K) pathway is a key signal transduction system that links oncogenes and multiple receptor classes to many essential cellular functions, and is perhaps the most commonly activated signalling pathway in human cancer. This pathway therefore presents both an opportunity and a challenge for cancer therapy. Even as inhibitors that target PI3K isoforms and other major nodes in the pathway, including AKT and mammalian target of rapamycin (mTOR), reach clinical trials, major issues remain. Here, we highlight recent progress that has been made in our understanding of the PI3K pathway and discuss the potential of and challenges for the development of therapeutic agents that target this pathway in cancer.

Molecular pathogenesis of human hepatocellular carcinoma

Abstract: Hepatocarcinogenesis is a slow process during which genomic changes progressively alter the hepatocellular phenotype to produce cellular intermediates that evolve into hepatocellular carcinoma. During the long preneoplastic stage, in which the liver is often the site of chronic hepatitis, cirrhosis, or both, hepatocyte cycling is accelerated by upregulation of mitogenic pathways, in part through epigenetic mechanisms. This leads to the production of monoclonal populations of aberrant and dysplastic hepatocytes that have telomere erosion and telomerase re-expression, sometimes microsatellite instability, and occasionally structural aberrations in genes and chromosomes. Development of dysplastic hepatocytes in foci and nodules and emergence of hepatocellular carcinoma are associated with the accumulation of irreversible structural alterations in genes and chromosomes, but the genomic basis of the malignant phenotype is heterogeneous. The malignant hepatocyte phenotype may be produced by the disruption of a number of genes that function in different regulatory pathways, producing several molecular variants of hepatocellular carcinoma. New strategies should enable these variants to be characterized.

Abl protein-tyrosine kinase inhibitor STI571 inhibits in vitro signal transduction mediated by c-kit and platelet-derived growth factor receptors.

Abstract: STI571 (formerly known as CGP 57148B) is a protein-tyrosine kinase inhibitor that is currently in clinical trials for the treatment of chronic myelogenous leukemia. STI571 selectively inhibits the Abl and platelet-derived growth factor (PDGF) receptor tyrosine kinases in vitro and blocks cellular proliferation and tumor growth of Bcr-abl - or v- abl -expressing cells. We have further investigated the profile of STI571 against related receptor tyrosine kinases. STI571 was found to potently inhibit the kinase activity of the α- and β-PDGF receptors and the receptor for stem cell factor, but not the closely related c-Fms, Flt-3, Kdr, Flt-1, and Tek tyrosine kinases. Additionally, no inhibition of c-Met or nonreceptor tyrosine kinases such as Src and Jak-2 has been observed. In cell-based assays, STI571 selectively inhibited PDGF and stem cell factor-mediated cellular signaling, including ligand-stimulated receptor autophosphorylation, inositol phosphate formation, and mitogen-activated protein kinase activation and proliferation. These results expand the profile of STI571 and suggest that in addition to chronic myelogenous leukemia, STI571 may have clinical potential in the treatment of diseases that involve abnormal activation of c-Kit or PDGF receptor tyrosine kinases.