Co-occurrence of germline pathogenic variants for different hereditary cancer syndromes in patients with Lynch syndrome.

BACKGROUND: Lynch syndrome (LS) is a hereditary condition characterized by a high risk of colorectal cancer, endometrial cancer, and other neoplasia associated with germline alterations in DNA mismatch repair genes. The classical genetic diagnostic strategy for LS consists of the Sanger sequencing of genes associated with the suspected syndrome. Next-generation sequencing (NGS) enables the simultaneous sequencing of a large number of hereditary cancer genes. Here, we aimed to study whether other germline pathogenic variants of hereditary cancer genes are present in patients with LS. METHODS: A cohort of 84 probands with a previous genetic diagnosis of LS by Sanger sequencing was reanalyzed using NGS via a commercial panel of 94 hereditary cancer genes by hybrid capture. The American College of Medical Genetics and Genomics criteria were used to classify the clinical significance of the variants. The findings of NGS were confirmed by Sanger sequencing. When possible, genetic analyses of the new findings in the proband's relatives were also performed by Sanger sequencing. RESULTS: We identified five families (6%), out of 84, with at least two germline pathogenic variants conferring to high or moderate risk in different dominant cancer-predisposing genes: [MLH1-BRCA2-NBN], [MLH1-BRCA1], [MSH2-ATM], [MSH6-NF1], and [MLH1-FANCA]. Interestingly, only one out of these five families exhibited a clinical phenotype associated with the new pathogenic variants. The family with three pathogenic variants of the [MLH1-BRCA2-NBN] genes showed a high aggregation of tumors associated with LS and breast and ovarian cancer syndrome. CONCLUSIONS: Our results showed that the co-occurrence of more than one pathogenic variant in cancer-predisposing genes was remarkable among cases of LS. In most cases, no clinicial manifestations were associated with the secondary pathogenic variants. Further studies are needed to confirm these findings and elucidate their clinical impact. Reanalysis of LS families should be considered only in families with mixed clinical phenotypes.

Circulating tumour cell analysis as an early marker for relapse in stage II and III colorectal cancer patients: a pilot study.

INTRODUCTION: Recent studies have identified both the prognostic and predictive utility of determining the number of circulating tumour cells (CTC) in patients with solid cancers. MATERIAL AND METHODS: In the present pilot study we evaluated the ability of two different methods to isolate CTC in combination with two strategies to enumerate CTC from patients with stages II and III surgically treated colorectal cancer (CRC). First, we used two systems for tumour cell enrichment (differential centrifugation and immunomagnetic beads), combined with two methods to enumerate CTC (real-time PCR and fl ow cytometry), to determine the most efficient combination. These experiments were performed in a model system using serial dilutions of HT29 tumour cell lines with lymphocytes. Then, CTC analysis using the technical approach selected before was performed in 109 blood samples from 16 stage II and III CRC patients during chemotherapy treatment and follow-up. RESULTS: Immunomagnetic beads followed by flow cytometry was the most efficient combination (ED=60.53; p=0.5). Two cases out of 16 patients analysed had clinical tumour relapse. In both, we detected a significant increase of CTC five and six months, respectively, before the relapse was clinically evidenced. An increase of CTC was also observed in another case without clinical evidence of relapse. The remaining cases (13) had very few or no detectable CTC and no clinical evidence of relapse (p=0.029). CONCLUSIONS: Changes in CTC numbers during follow-up might predict tumour relapse. Further evaluation of CTC prognostic and predictive value in patients with early CRC is warranted.