Assignment of RAS proto-oncogenes in Chinese hamsters: implications for mammalian gene linkage conservation and neoplasia

Chromosomal characteristics of tumorigenic cells derived from a spontaneous uterine leiomyosarcoma of the Chinese hamster

A tumorigenic cell line (CHAUT) derived from a spontaneous uterine leiomyosarcoma of the Chinese hamster was established, and two clones (CHAUT-C and CHAUT-G) were characterized cytogenetically by both G- and C-band techniques. In both clones, all cells analyzed (53 in the C clone and 65 in the G clone) were distributed within a diploid range (24-26) with a modal number of 25. Their karyotypes were also characterized by four common changes; translocation of heterochromatic segment onto chromosome 2, tetrasomy of chromosome 10, monosomy of X chromosome, and one to three additional marker chromosomes of unknown origin.

Specific chromosomal aberrations correlated to transformation in Chinese hamster cells

Cytogenetic changes were investigated during the spontaneous progression of CHEF18 Chinese hamster cells towards tumorigenicity. We further report the chromosomal characterization of a series of spontaneous anchorage-independent clones, as well as of a series of tumor-derived cell lines resulting from injection of late passage cells in nude mice. The high karyotypic homogeneity (presence of four marker chromosomes strictly associated in all the metaphases analyzed) in all clones and tumor-derived cell lines prompted us to alter the specific pattern of chromosomal aberrations in order to identify which if any of the aberrations were more strictly related to transformation. For this purpose we treated a tumor-derived cell line with Colcemid and analyzed the reversion of anchorage-independent phenotype in the subclones showing an altered association of the four marker chromosomes. We conclude that two of four marker chromosomes contribute to anchorage independence.

Folate-sensitive fragile sites in Chinese hamster cell lines

The expression of fragile sites in three different Chinese hamster cell lines was studied. Results showed that folate-sensitive fragile sites were expressed in the pericentromeric regions of chromosomes 1, 3, 4, 6, and 7 and in band 1q22. A comparison of the breakpoints involved in formation of chromosome rearrangements in some established Chinese hamster cell lines was also made. Results showed that while the specific type of rearrangement was random, the breakpoints were not. Three of the chromosomal sites most frequently involved in breaks were regions in which fragile sites were expressed.

Pancreatic ductal adenocarcinomas induced in Syrian hamsters by N-nitrosobis(2-oxopropyl)amine contain a c-Ki-ras oncogene with a point-mutated codon 12

We have used the polymerase chain reaction and dideoxynucleotide sequencing to amplify and sequence exons 1 and 2 of the c-Ki-ras proto-oncogene from the normal Syrian golden hamster. Similar methods were employed to screen for the presence of point mutations in the c-Ki-ras oncogene in primary hamster pancreatic ductal adenocarcinomas (PDC) induced by N-nitrosobis(2-oxopropyl)amine (BOP). A GGT to GAT point mutation was detected in codon 12 of the c-Ki-ras gene in 10 primary hamster PDCs. This same point mutation was present in two nonclonal cell lines, PC-1 and PC-1-0, established from tumors that were produced in hamsters by subcutaneously implanting a preparation of minced BOP-induced PDC. Two clonal cell lines, Cl-3 and Cl-7, were cloned from the PC-1 cell line, and these cell lines also carried the GAT point mutation at codon 12. This point mutation was the same as that detected in greater than 75% of adenocarcinomas from the human exocrine pancreas. Thus, our findings provide further validation for the use of the BOP-induced hamster PDC model as a relevant experimental model for human pancreas cancer: not only did the hamster pancreatic ductal adenocarcinomas closely resemble their human counterpart in histopathological morphology and sequential development, but they also contained the same point mutation in codon 12 of the c-Ki-ras oncogene, as has been reported for human pancreatic adenocarcinomas.

Qualitative analysis of chromosomal evolution in a colcemid-treated Chinese hamster population

Colcemid is known to inhibit the spindle formation and to induce polyploidy and chromosomal nondisjunction. Using a V79 Chinese hamster cell line, we have shown that colcemid is able to induce the formation of cells that are numerically diploid but whose karyotype, when analyzed with the G-banding technique, differs from that of the untreated ones. Even though these cells have a normal chromosomal constitution, they carry alterations in the chromosomal balance and, consequently, in gene dosage. This could result in an abnormal expression of cellular genes or in the expression of new or preexisting recessive mutations, even in a diploid chromosomal constitution.

Genetic analysis of tumorigenesis: a conserved region in the human and Chinese hamster genomes contains genetically identified tumor-suppressor genes

Regional chromosome homologies were found in a comparison of human 11p with Chinese hamster 3p. By use of probes that recognize six genes of human 11p (INS, CAT, HBBC, CALC, PTH, and HRAS), the corresponding genes were localized by in situ hybridization on Chinese hamster chromosome 3. INS and CAT were located close to the centromere on 3p, whereas HBBC, CALC, and PTH were at 3q3-4 and HRAS at 3q4. Extensive prior data from chromosome studies of tumorigenic and tumor-derived Chinese hamster cells have suggested the presence of a tumor-suppressor gene on 3p. Two tumor-suppressor genes have been described on human 11p, one linked to CAT and one to INS. The present study raises the possibility that the Chinese hamster suppressor may be closely linked to INS or CAT.