A single-nucleotide polymorphism (SNP) in the promoter of the MDM2 gene, SNP309 (a T→G change), was recently implicated in the early onset of cancer in individuals with Li-Fraumeni syndrome and of sporadic soft-tissue sarcoma. SNP309 induces an increase in the level of Mdm2 protein, which causes attenuation of the p53 pathway. To investigate the effect of this polymorphism in colorectal cancer pathogenesis, we genotyped 153 colorectal cancer patients who were randomly selected from among 330 consecutive patients stratified according to p53 mutation status and age at diagnosis, for alleles of MDM2–SNP309. Among the 77 patients with p53 wild-type tumors, the median age at colorectal cancer diagnosis was 71.5 years for patients with the T/T genotype and 61.0 years for patients with SNP309 (T/G or G/G genotype) (estimated difference between medians [Hodges–Lehmann method] = 8.0 years, 95% confidence interval = 1.0 to 16.0 years; P = .03 [two-sided Wilcoxon rank sum test]). Our data indicate that MDM2–SNP309 is a modifier of the age at colorectal cancer onset for patients whose tumors have a wild-type p53 gene.

A large body of evidence strongly suggests that the p53 tumor suppressor pathway is central in reducing cancer frequency in vertebrates. The protein product of the haploinsufficient mouse double minute 2 (MDM2) oncogene binds to and inhibits the p53 protein. Recent studies of human genetic variants in p53 and MDM2 have shown that single nucleotide polymorphisms (SNPs) can affect p53 signaling, confer cancer risk, and suggest that the pathway is under evolutionary selective pressure ( 1 – 4 ). In this report, we analyze the haplotype structure of MDM4, a structural homolog of MDM2, in several different human populations. Unusual patterns of linkage disequilibrium (LD) in the haplotype distribution of MDM4 indicate the presence of candidate SNPs that may also modify the efficacy of the p53 pathway. Association studies in 5 different patient populations reveal that these SNPs in MDM4 confer an increased risk for, or early onset of, human breast and ovarian cancers in Ashkenazi Jewish and European cohorts, respectively. This report not only implicates MDM4 as a key regulator of tumorigenesis in the human breast and ovary, but also exploits for the first time evolutionary driven linkage disequilibrium as a means to select SNPs of p53 pathway genes that might be clinically relevant.

Background: BRCA1 and BRCA2 are the two major genes responsible for the breast and ovarian cancers that cluster in families with a genetically determined predisposition. However, regardless of the mutation detection method employed, the percentage of families without identifiable alterations of these genes exceeds 50%, even when applying stringent criteria for family selection. A small but significant increase in mutation detection rate has resulted from the discovery of large genomic alterations in BRCA1. A few studies have addressed the question of whether BRCA2 might be inactivated by the same kinds of alteration, but most were either done on a relatively small number of samples or employed cumbersome mutation detection methods of variable sensitivity. Objective: To analyse 121 highly selected families using the recently available BRCA2 multiplex ligation dependent probe amplification (MLPA) technique. Results: Three different large genomic deletions were identified and confirmed by analysis of the mutant transcript and genomic characterisation of the breakpoints. Conclusions: Contrary to initial suggestions, the presence of BRCA2 genomic rearrangements is worth investigating in high risk breast or ovarian cancer families.

We investigated whether Circulating Tumor Cells (CTCs) isolated from epithelial tumors could survive and grow in xenotransplants. To this purpose, EpCAM-positive CTCs were enriched by CellSearch platform the only FDA-cleared automated platform that quantifies tumor burden in peripheral blood and provides clinical evidence of predictive and prognostic value. The CTCs were isolated from metastatic prostate (n=6) and breast (n=2) cancer patients. The xenograft assay was developed in 8-week-old NOD/SCID mice that were subcutaneously injected with increasing amounts of CTCs (ranging from 50 to 3000). Human CTCs were found in 8 out of 8 murine peripheral blood (muPB) and in 6 out of 8 murine bone marrow (muBM) samples, after a median follow-up of 10.3 months. Six out of 8 spleens were positive for human cytokeratin. Our assay showed higher successful rate than those previously reported in breast cancer and hepatocellular carcinoma. The role of EpCAM during carcinogenesis is controversial. The identification of human CTCs in muPB, muBM and spleen demonstrates that the EpCAM-positive fraction of CTCs retains the migratory capacity. This is the first experimental evidence that as few as 50 EpCAM-positive prostate cancer CTCs putatively contain metastasis-initiating-cells (MIC).

Purpose: A growing number of sequence changes of unknown clinical significance are being identified in the BRCA1 gene. However, these variants cannot be used for identification and surveillance of at-risk individuals unless their pathogenic role can be demonstrated. The frequency of these variants makes research on this subject a relevant topic in the field of predisposition to breast and ovarian cancers. Herein, we investigate the pathogenicity of the BRCA1 p.Val1688del (c.5181_5183delGTT) variant, which recurs in our population. Patients and Methods: Recent studies have drawn attention to different strategies that, if considered singly, do not usually provide sufficient power to firmly state for or against causality, thus forcing to a re-evaluation of the literature on each specific variant. To increase the power of our study, we used a recently described strategy that integrates data from multiple independent evidences. By this approach, we analyzed data from the comprehensive study of 12 breast/ovarian cancer families carrying p.Val1688del. Results: We succeeded in integrating five independent evidences of disease causality including segregation, tumor pathology, and evolutionary and epidemiologic data. Under this model, we obtained a final score of 349,000:1 in favor of disease causality. This result largely matches established cutoffs, and thus is readily translatable into a clear clinical message. Conclusion: We show that p.Val1688del is a pathogenic mutation deriving from a common founder. Notably, this study alone increases by 15% the number of BRCA1-positive families in our patients’ cohort, thus substantially contributing to explain many of the families wherein prediction of a BRCA1 mutation contrasted with the absence of a molecular recognizable defect.