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  • Author: Anca Negura x
  • Microbiology and Virology x
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Abstract

Both incidence and mortality of colorectal cancer (CRC) in Romania have shown a continuous increase during the last decades. Hereditary Non-Polyposic Colorectal Cancer (HNPCC), also known as Lynch syndrome, is mainly attributable to mismatch repair (MMR) genes MSH2, MSH6, and MLH1. Individuals carrying germ-line mutations of these genes present high lifetime risk of colorectal and other cancers, compared to non-carriers. Oncogenetics is developed worldwide nowadays, for identifying hereditary predisposition to cancer and offering appropriate clinical follow-up to patients and mutation carriers in Lynch families. Molecular oncogenetic diagnosis in Lynch syndrome is based on complete Sanger sequencing of entire MMR genes, which is time and resources consuming, therefore needing an appropriate and adapted optimization. Conventional sequencing requires a sufficient number of available samples to be processed simultaneously, which increases the waiting time for diagnostic results. Complete analysis for only one patient meets difficult technical problems due to the complex co-amplification of all gene regions of interest within the same conditions, therefore increasing the costs and reducing the cost-effectiveness of the test. Here we present an original and robust technical protocol for sequencing the entire MSH2, MSH6, and MLH1 coding sequence for one patient in a single PCR plate. Our optimized and verified system overcomes all technical problems and offers a quick, robust, and cost-effective possibility to personalize molecular oncogenetic diagnosis in Lynch syndrome.

Abstract

Hereditary predisposition to breast and ovarian cancer (HBOC) is diagnosed by molecular analysis of deleterious mutations in BRCA genes, allowing oncogenetic follow-up of patients and of their families. BRCA testing addresses only to HBOC families, using restrictive inclusion criteria based on familial history of cancer and age at diagnosis. Sporadic ovarian cancer has high incidence and mortality in Romania, with low median age of diagnosis and possibly a higher magnitude of hereditary contribution comparing to othe populations. However, sporadic ovarian cancers do not qualify for BRCA testing according to inclusion criteria, and a complete BRCA screening of all cancers is neither feasible nor recommended. Despite the large diversity of BRCA mutations worldwide, some recurrent mutations have higher frequencies in diverse populations. Precisely screening for recurrent mutations in a target population allows to rapidly identifying mutation carriers without sequencing the entire BRCA genes. In Romanian population and neighboring countries, several recurrent mutations have already been described. In a consecutive series of 50 sporadic ovarian cancer patients, not qualifying for BRCA complete testing, we screened for 9 most common BRCA mutations, by multiplex-PCR, RFLP and targeted Sanger sequencing. Our results revealed 6 different BRCA mutations in 8 unrelated patients, with a frequency of 16%, much higher than expected. We further recommend screening for the identified mutations in larger series of cancer patients. The results are highly beneficial to cancer patients, healthy relatives, and overall, considering prevention in cancer a priority, to public health system and future of oncogenetics in Romania