Lynch syndrome (LS) is the most common hereditary colorectal cancer syndrome, caused by germline mutations in one of the major genes involved in mismatch repair (MMR): MLH1,MSH2,MSH6 and more rarely, PMS2. Recently, germline deletions in EPCAM have been also associated to the syndrome. Most of the pathogenic MMR mutations found in LS families occur in MLH1 or MSH2. Gene variants include missense, nonsense, frameshift mutations, large genomic rearrangements and splice‐site variants and most of the studies reporting the molecular characterization of LS families have been conducted outside South America. In this study, we analyzed 60 unrelated probands diagnosed with colorectal cancer and LS criteria. Testing for germline mutations and/or rearrangements in the most commonly affected MMR genes (MLH1, MSH2, EPCAM and MSH6) was done by Sanger sequencing and MLPA. Pathogenic or likely pathogenic variants were identified in MLH1 or MSH2 in 21 probands (35.0%). Of these, approximately one‐third were gene rearrangements. In addition, nine variants of uncertain significance (VUS) were identified in 10 (16.6%) of the sixty probands analyzed. Other four novel variants were identified, only in MLH1. Our results suggest that MSH6 pathogenic variants are not common among Brazilian LS probands diagnosed with CRC and that MMR gene rearrangements account for a significant proportion of the germline variants in this population underscoring the need to include rearrangement analysis in the molecular testing of Brazilian individuals with suspected Lynch syndrome.

Lynch syndrome (LS) is an autosomal dominant disorder, with high penetrance that affects approximately 3% of the cases of colorectal cancer. Affected individuals inherit germline mutations in genes responsible for DNA mismatch repair, mainly at MSH2, MLH1, MSH6 and PMS2. The molecular screening of these individuals is frequently costly and time consuming due to the large size of these genes. In addition, PMS2 mutation detection is often a challenge because there are 16 different pseudogenes identified until now. In the present work we evaluate a molecular screening strategy based in next generation sequencing (NGS) in order to optimize the mutation detection in LS patients. We established 16 multiplex PCRs for MSH2, MSH6 and MLH1 and 5 Long-Range PCRs for PMS2, coupled with NGS. The strategy was validated by screening 66 patients who filled Bethesda and Amsterdam criteria for LS from health institutions of Brazil. The mean depth of coverage for MSH2, MSH6, MLH1 and PMS2 genes was 7.988, 36.313, 11.899 and 4.772 times, respectively. Ninety-four variants were found in exons and flanking intron/exon regions for the four MMR genes. Twenty-five were pathogenic or VUS and found in 32 patients (7 in MSH2, 5 in MSH6, 12 in MLH1 e 1 in PMS2). All variants were confirmed by Sanger sequencing. The strategy was efficient to reduce time consuming and costs to identify genetic changes at these MMR genes, reducing in three times the number of PCR reactions performed per patient and was efficient in identifying variants at PMS2 gene.

Interferon regulatory factor 2-binding protein 2 (IRF2BP2) encodes a member of the IRF2BP family of transcriptional regulators, which includes IRF2BP1, IRF2BP2, and IRF2BPL (EAP1). IRF2BP2 was initially identified as a transcriptional corepressor that was dependent on Interferon regulatory factor-2 (IRF-2). The IRF2BP2 protein is found in different organisms and has been described as ubiquitously expressed in normal and tumor cells and tissues, indicating a possible role for this transcriptional cofactor in different cell signaling pathways. Recent data suggest the involvement of IRF2BP2 in the regulation of several cellular functions, such as the cell cycle, cell death, angiogenesis, inflammation and immune response, thereby contributing to physiological cell homeostasis. However, an imbalance in IRF2BP2 function may be related to the pathophysiology of cancer. Some studies have shown the association of IRF2BP2 expression in hematopoietic and solid tumors through mechanisms based on gene fusion and point mutations in gene coding sequences, and although the biological functions of these types of hybrid and mutant proteins are not yet known, they are thought to be involved in an increase in the likelihood of tumor development. In this review, we address the possible involvement of IRF2BP2 in tumorigenesis through its regulation of important pathways involved in tumor development.