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Approximately 10% of ovarian cancers are due to mutations in highly penetrant inherited cancer susceptibility genes. The highly polymorphic HRAS1 minisatellite locus, located just downstream from the proto-oncogene H-ras-1 on chromosome 11p, consists of four common progenitor alleles and several dozen rare alleles, which apparently derive from mutations of the progenitors. Mutant alleles of this locus represent a major risk factor for cancers of the breast, colorectum, and bladder, and it was found that BRCAI mutation carriers with at least one rare HRAS1 allele have a greater risk of ovarian cancer than BRCA1 carriers with only common HRAS1 alleles. There are no conclusive studies of HRAS1 alleles in sporadic epithelial ovarian cancer. A case-control study of HRAS1 alleles was performed on DNA from 136 Caucasian patients with ovarian cancer and 108 cancer-free controls using conventional (Southern blot) and PCR-based methods to determine the frequency of rare HRAS1 alleles. Odds ratios (ORs) were estimated using unconditional logistic regression methods. A single degree of freedom test was used to assess the significance of linear trend across categories of increasing exposure. A statistically significant association between rare HRAS1 alleles and risk of ovarian cancer was observed [OR, 1.70; 95% confidence interval (CI), 1.03-2.80; P = 0.04]. Having only one rare allele was associated with a relative risk of 1.66 (95% CI, 0.91-3.01), whereas having two rare alleles increased the relative risk to 2.86 (95% CI, 0.75-10.94; trend P = 0.03). Analysis of HRAS1 allele types by the age of the case at diagnosis revealed that younger cases (<45 years) had a borderline statistically significant increased association with rare HRAS1 alleles compared to older cases (> or = 0 years; OR, 1.89; 95% CI, 0.90-3.98; P = 0.09). Rare HRAS1 alleles contribute to ovarian cancer predisposition in the general population. Thus, the HRAS1-variable number of tandem repeats locus may function as a modifier of ovarian cancer risk in both sporadic and hereditary ovarian cancer.

The hypothesis that rare variable nucleotide tandem repeat alleles of the Ha-ras-1 polymorphism are an inherited predisposing factor in human lung carcinogenesis has been evaluated in an age, race, and smoking matched case-control study. Twenty-three different alleles were identified by their restriction fragment length in DNA isolated from peripheral blood lymphocytes and were categorized into three groups: common; intermediate; and rare. The frequencies of rare alleles in blacks with either squamous cell carcinoma, large cell carcinoma, or small cell carcinoma were found to be significantly higher than those among groups of control subjects that were comprised of chronic obstructive pulmonary disease patients and patients with cancer at sites other than the lung. A similar trend which did not reach statistical significance was observed in whites. These data are consistent with the hypothesis that inheritance of Ha-ras-1 rare restriction fragment length alleles represents a genetic risk factor for some human lung cancers. The biological basis of this observation remains to be clarified, and it is possible that ethnic variations in rare allele frequencies are responsible for the differences noted. However, the data suggest that further evaluation of the Ha-ras-1 polymorphism as a marker of individual lung cancer susceptibility is warranted.

We have prospectively examined 66 consecutive initial diagnostic lymph node biopsies from unselected patients suspected of having malignant lymphoma for clonal immunophenotypic and immunogenotypic markers. By morphological and cell surface phenotypic criteria 52 had non-Hodgkin's lymphoma derived from the B-cell lineage and in these we compared surface immunoglobulin criteria for clonality with immunoglobulin gene rearrangement as detected by JH, C kappa, and C lambda gene probes. We found that the addition of BglII and HindIII double digests to the standard BamHI and EcoRI restriction enzymes made it possible to detect rearrangement in the vast majority of lymphomas and that rearrangement of both JH alleles is the rule. A rearranged heavy and/or light chain gene was detected in 47 of 52 (91%) tumors and the JH probe alone detected rearrangements in 87% of tumors when multiple restriction enzymes were used. In contrast, surface immunoglobulin, the standard clonal marker for monoclonal B-cell malignancy, was either undetectable or did not exhibit light chain restriction in 29 of 52 tumors as detected by flow cytometric analysis. Further, in 24 of these 29 tumor DNAs we could detect an Ig gene rearrangement. In follicular (nodular) lymphoma which often gives ambiguous immunophenotypic results by cell suspension techniques, monoclonal gene rearrangements were detected in 16 of 18 tumor DNAs. Monoclonal surface immunoglobulin was detected in only 8 of 18 of this subset of cases. The 52 tumors were also analyzed for potential oligoclonality. We found that the use of BglII, a restriction enzyme that closely spanned the JH region, increased the sensitivity of detecting rearrangements and facilitated the identification of isotype switch variants. In only a single (1 of 52) tumor DNA were more than two rearranged bands seen with JH, C kappa, and C lambda probes, suggesting a multiclonal origin. Additional cases thought to potentially represent oligoclonality by immunophenotypic criteria proved to be isotype switch variants. We conclude that Ig gene rearrangement is an extremely sensitive method for defining monoclonality in lymphoma cell populations, particularly if multiple restriction enzymes are used, and that the vast majority of the clonal diversity seen in initial diagnostic biopsies is the result of isotypic switch within a given clone rather than true oligoclonality.