Cancer may be defined as a progressive series of genetic events that occur in a single clone of cells because of alterations in a limited number of specific genes: the oncogenes and tumor suppressor genes. The association of consistent chromosome aberrations with particular types of cancer has led to the identification of some of these genes and the elucidation of their mechanisms of action. Consistent chromosome aberrations are observed not only in rare tumor types but also in the relatively common lung, colon, and breast cancers. Identification of additional mutated genes through other chromosomal abnormalities will lead to a more complete molecular description of oncogenesis.

https://science.sciencemag.org/content/sci/254/5035/1153.full.pdf

Chromosome aberrations and cancer

Genes that can inhibit the expression of the tumorigenic phenotype have been detected by the fusion of normal and malignant cells, the phenotypic reversion of in vitro transformants, the induction of terminal differentiation of malignant cell lineages, the loss of "recessive cancer genes," the discovery of regulatory sequences in the immediate vicinity of certain oncogenes, and the inhibition of tumor growth by normal cell products Such tumor suppressor genes will probably turn out to be as, if not more, diversified as the oncogenes Consideration of both kinds of genes may reveal common or interrelated functional properties

The Approaching Era of the Tumor Suppressor Genes

The concept that cells can become malignant upon the elimination of parts of chromosomes inhibiting cell division dates back to Boveri in 1914. Deletions occurring in tumor cells are therefore considered a first indication of possible locations of tumor suppressor gene. Approaches used to localize and identify the paradigm of tumor suppressors, RB1, have also been applied to localize tumor suppressor genes on 3p, the short arm of chromosome 3. This review discusses the methodological advantages and limitations of the various approaches. From a review of the literature on losses of 3p in different types of solid tumors it appears that some tumor types show involvement of the same region, while between others the regions involved clearly differ. Also discussed are results of functional assays of tumor suppression by transfer of part of chromosome 3 into tumor cell lines. The likelihood that a common region of deletions would contain a tumor suppressor is strongly enhanced by coincidence of that region with a chromosome fragment suppressing tumorigenicity upon introduction in tumor cells. Such a situation exists for a region in 3p21.3 as well as for one or more in 3p12-p14. The former region is considered the location of a lung cancer suppressor. The same gene or a different one in the same region may also play a role in the development of other cancers including renal cell cancer. In the latter cancer, there may be additional roles of the VHL region and/or a 3p12-p14 region. The breakpoint region of a t(3;8) originally found to be constitutively present in a family with hereditary renal cell cancer now seems to be excluded from such a role. Specific genes on 3p have been suggested to act as suppressor genes based on either their location in a common deletion region, a markedly reduced expression or presence of aberrant transcripts, their capacity to suppress tumorigenicity upon transfection in to tumor cells, the presumed function of the gene product, or a combination of several of these criteria. A number of genes are evaluated for their possible role as a tumor suppressor according to these criteria. General agreement on such a role seems to exist only for VHL. Though hMLH1 plays an obvious role in the development of specific mismatch repair-deficient cancers, it cannot revert the tumor phenotype and therefore cannot be considered a proper tumor suppressor. The involvement of VHL and MLH1 also in some specific hereditary cancers allowed to successfully apply linkage analysis for their localization. TGFBR2 might well have a tumor suppressor function. It does reduce tumorigenicity upon transfection. Other 3p genes coding for receptor proteins THRB and RARB, are unlikely candidates for tumor suppression. Present observations on a possible association of FHIT with tumor development leave a number of questions unanswered, so that provisionally it cannot be considered a tumor suppressor. Regions that have been identified as crucial in solid tumor development appear to be at the edge of synteny blocks that have been rearranged through the chromosome evolution which led to the formation of human chromosome 3. Although this may merely represent a chance occurrence, it might also reflect areas of genomic instability.

Deletions of the short arm of chromosome 3 in solid tumors and the search for suppressor genes

RENAL carcinoma, the most common cancer of the kidney, occurs in over 27000 individuals in the United States each year and is responsible for over 11000 deaths annually. 1 The incidence of renal carcinoma worldwide has been increasing at an annual rate of approximately 2%. 1 Although renal carcinoma has been reported in children as young as 3 years, it most commonly occurs in adults between the ages of 50 and 70 years. 2 Renal carcinoma affects males twice as frequently as females and accounts for approximately 3% of adult cancers. Although a number of hormonal, environmental, cellular, and genetic factors have been evaluated, little is known about the etiology of renal cancer. 3 There is an increased incidence of renal cancer among workers exposed to asbestos and among leather workers, 4,5 and a strong correlation has been found with cigarette smoking. 6,7 In patients with end-stage renal disease, particularly

Identification of the von Hippel-Lindau (VHL) gene. Its role in renal cancer.

Chromosome aberrations were determined in short-term cultures of 18 papillary renal cell tumors, as well as in the cell line ACHN, and the results were evaluated together with 20 previously published cases. We found that chromosomes 7, 17, and 16 and the Y chromosome were specifically involved in the karyotype changes, marks benign papillary renal cell adenomas (ten cases). Malignant papillary renal cell carcinomas (29 cases) were characterized by additional trisomies: trisomy 16 occurred in 20 tumors, and trisomy 12 and 20 in 8 tumors each. Loss of the Y chromosome was observed in 7 of 9 benign and in 23 of 25 malignant tumors that developed in males. None of the papillary renal cell adenomas or carcinomas showed a loss of 3p or gain of a 5q segment, both of which are characteristic of common non-papillary renal cell carcinomas.

Cytogenetics of papillary renal cell tumors

A method combining an enzymatic technique and short term culture was applied to 27 tumor tissues from 22 patients with nonfamilial renal cell carcinoma in order to establish the chromosome changes in these tumors. Chromosome analyses were successfully carried out in quinacrine mustard-Hoechst 33258 and G-banded preparations of 14 tumors from 12 patients, including 2 cases in which established cell lines were obtained after 43 and 64 days in culture and maintained for 25 and 30 passages in an in vitro system, respectively. The modal chromosome numbers ranged from 38–46 in 11 samples, involving chromosomes in structural and numerical changes and 72 chromosomes in one case, with the remaining 2 samples showing a variety of chromosome numbers. Banding analysis revealed 45 clonal aberrations in 11 tumor samples from 10 patients and nonclonal aberrations in the remaining 3 samples from 2 of the patients. Rearrangements of chromosome 3 were observed in 12 tumors, with the breakpoints on this chromosome almost totally clustered from p11 to p21. In one case both primary and metastatic tumors were studied, and an isochromosome for the long arm of chromosome 1 was observed as clonal in origin in the metastatic tissue. Two cases showed nonclonal changes. The remaining case had one clonal abnormality, i.e. , deletion of 6q. Of the remaining 33 clones, chromosomes 1, 2, 6, 11, and 17 were frequently involved. These results suggest that renal cell carcinoma may be cytogenetically classified into 3 categories: ( a ) tumors with changes of chromosome 3; ( b ) tumors with other clonal aberrations; and ( c ) tumors without clonal changes. Rearrangements of chromosome 3 may be possibly associated with the genesis and/or progression of renal cell carcinoma.

Cytogenetic Studies of Tumor Tissue from Patients with Nonfamilial Renal Cell Carcinoma

Two new mouse epidermal cell lines have been isolated and characterized as target cells for three chemical carcinogens. The ability to grow these cells at low density (approximately 5 clonogenic cells/cm2) has permitted more precise quantitation of chemical carcinogen-induced changes in epidermal differentiation. The cell lines, designated 291 and 271c, retain the property previously observed in primary cultures of mouse epidermal cells, that is the regulation of terminal differentiation by extracellular Ca2+ ion. Altered response to extracellular Ca2+ after carcinogen treatment of these cells is the basis of the assay endpoint. Other normal properties demonstrated by these cells are keratin immunofluorescence patterns, ability to form cornified envelopes in response to Ca2+ and a lack of tumorigenicity. Both of the lines have high cloning efficiencies (up to 20%) and characteristic epidermal morphology. Their chromosome number, however, is near tetraploid. Dose response studies indicated an increase in colonies with altered response to Ca2+ proportional to the dose of three chemical carcinogens: DMBA 0.001-0.5 microgram/ml X 24 h, MCA 0.01-5 micrograms/ml X 24 h and MNNG 0.01-0.2 micrograms/ml X 1 h. The optimized assay protocol has provided a reproducible means of quantitating carcinogen-altered epidermal cells relative to carcinogen dose, and of isolating cell clones for studies of altered differentiation in carcinogenesis and chemotherapy.

Mitsuaki A. Yoshida

Papers

Cytogenetic Studies of Tumor Tissue from Patients with Nonfamilial Renal Cell Carcinoma

Mouse cell clones for improved quantitation of carcinogen-induced altered differentiation.

Recurrent endometrial adenocarcinoma with rearrangement of chromosomes 1 and 11.

Chromosome changes in mycosis fungoides in an XYY male

14q+ in Ph-positive chronic myelogenous leukemia.