The Transcriptional Co-factor IRF2BP2: A New Player in Tumor Development and Microenvironment.

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.

Germline MLH1, MSH2 and MSH6 variants in Brazilian patients with colorectal cancer and clinical features suggestive of Lynch Syndrome.

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.

Screening for germline mutations in mismatch repair genes in patients with Lynch syndrome by next generation sequencing.

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.

Variantes de seqüência no gene MSH2 em pacientes selecionados para a Síndrome de Lynch / [Sequence variants in the MSH2 gene in patients selected for Lynch syndrome]

A Síndrome de Lynch (SL) ou Câncer Colorretal Hereditário Não -Poliposo (HNPCC) é uma doença autossômica dominante associada a mutaçõesna linhagem germinativa nos genes do Sistema Mismatch Repair (MMR)de reparo do DNA e é responsável por aproximadamente 5% de todos os casos de câncer colorretal (CCR). A maioria das mutações ocorre nos genes MSH2 (50%) e MLH1 (40%), e gera uma proteína truncada e não funcional. Mais de 513 alterações diferentes nos genes de reparo foram relatadas, sendo que 10% das encontradas no gene MSH2envolvem a substituição de um aminoácido. O sistema de reparo MMR corrige erros de pareamento base base, além de inserções e deleções que ocorrem durante a síntese do DNA, melhorando a fidelidade do mecanismo de replicação, além de estar envolvido nos processos de ecombinação, na geração da diversidade imune e na resposta celular a danos específicos a o DNA. A inativação mutacional dos genes MMR leva a um reparo insuficiente do DNA e ao desenvolvimento de tumores caracterizados pelos altos níveis MSI...

Lynch syndrome (SL) or Colorectal Cancer Hereditary nonpolyposis (HNPCC) is an autosomal dominant disease associated with germline mutations in the MMR genes of the DNA repair system and it is responsible for approximately 5% of all cases of colorectal cancer (CCR). Most of the mutations occur in the MSH2 (50%) and MLH1 genes (40%), and generates a truncated, nonfunctional protein. More than 513 different changes in repair genes have been reported, and 10% of those mutations can be found in the MSH2 gene causing substitution of one amino acid. The repair system MMR corrects mismatched nucleotides, insertions and deletions that occur during DNA synthesis, improving the fidelity of replication mechanism and it is also involved in the process of recombination in the generation of immune diversity and specific cellular response to DNA damage. Mutational inactivation of MMR genes leads to insufficient DNA repair and the development of tumors characterized by high levels of MSI. SL patients often develop colorectal cancer at an early age, and they also have an increased risk of developing extra colonic tumors. The main objective of this study was to identify sequence variants in the MSH2 gene in selected patients for Lynch syndrome according to the criteria of Amsterdam or modified Bethesda, assessing the sensitivity and specificity for the presence of the mutation... .