Lynch syndrome (LS) is an autosomal dominant syndrome that predisposes individuals to development of cancers early in life. These cancers are mainly the following: colorectal, endometrial, ovarian, small intestine, stomach and urinary tract cancers. LS is caused by germline mutations in DNA mismatch repair genes (MMR), mostly MLH1 and MSH2, which are responsible for more than 85% of known germline mutations. To search for germline mutations in MLH1 and MSH2 genes in 123 unrelated South American suspected LS patients (Bethesda or Amsterdam Criteria) DNA was obtained from peripheral blood, and PCR was performed followed by direct sequencing in both directions of all exons and intron-exon junctions regions of the MLH1 and MSH2 genes. MLH1 or MSH2 pathogenic mutations were found in 28.45% (34/123) of the individuals, where 25/57 (43.85%) fulfilled Amsterdam I, II and 9/66 (13.63%) the Bethesda criteria. The mutations found in both genes were as follows: nonsense (35.3%), frameshift (26.47%), splicing (23.52%), and missense (9%). Thirteen alterations (35.14%) were described for the first time. The data reported in this study add new information about MLH1 and MSH2 gene mutations and contribute to better characterize LS in Brazil, Uruguay and Argentina. The high rate of novel mutations demonstrates the importance of defining MLH1 and MSH2 mutations in distinct LS populations.

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The ETV6 gene encodes an ETS family transcription factor that is involved in a myriad of chromosomal rearrangements found in hematological malignancies and other neoplasms. A recurrent ETV6 translocation, previously described in patients with acute myeloid leukemia (AML) (Genes Chromosomes Cancer 51:328–337,2012, Leuk Res 35:e212-214, 2011), whose partner has not been identified is t(7;12)(p15;p13). We herein report that the t(7;12)(p15;p13) fuses ETV6 to ANLN, a gene not previously implicated in the pathogenesis of hematological malignancies, and we demonstrate that this translocation leads to high expression of the fusion transcript in the myeloid and lymphoid lineages.

Introduction: The development of next-generation sequencing has made it feasible to interrogate the entire genome or exome (coding genome) in a single experiment. Accordingly, our knowledge of the somatic mutations that cause cancer has increased exponentially in the last years. MPNs and MDS/MPD are chronic myeloid neoplasms characterized by an increased proliferation of one or more hematopoietic cell lineages, and an increased risk of transformation to acute myeloid leukemia (AML). MPNs and MDS/MPDs are heterogenous disorders, both in clinical presentation and in prognosis. We sought to determine the genetic landscape of Ph-negative MPNs and MDS/MPD through next-generation sequencing. Methods: Paired DNA (sorted CD66b-granulocytes/skin biopsy) from 102 patients with MPNs or MDS/MPD was subjected to whole exome sequencing on a Illumina HiSeq 2000 platform using Agilent SureSelect kit. Diagnosis included primary myelofibrosis (MF; N=42), essential thrombocythemia (ET; N=28), polycythemia vera (PV; N=12), chronic myelomonocytic leukemia (CMML; N=10), systemic mastocytosis (MS; N=6), MDS/MPD-Unclassified (N=2) and post-MPN AML (N=2). Tumor coverage was 150x and germline coverage was 60x. Somatic variants calls were generated by combining the output of Somatic Sniper (Washington University), Mutect (Broad Institute) and Pindel (Washington University). The combined output of these 3 tools was further filtered by in-house criteria in order to reduce false-positive calls (minimum coverage at both tumor/germline ≥8 reads; fraction of reads supporting alternate allele ≥10% in tumor and ≤10% in germline; ratio of allele fraction tumor:germline >2; excluding mutations seen in SNP databases). All JAK2 and CALR mutations were validated through Sanger sequencing. Validation of other somatic mutations is currently underway. Analysis of driver mutations was made with the Intogen web-based software, using the Oncodrive-FM and Oncodrive-cluster algorithms (www.intogen.org). Significantly mutated genes were considered as those with a q-value of <0.10. Results: We identified a total of 309 somatic mutations in all patients, with each patient having an average of 3 somatic abnormalities, fewer than most solid tumors that have been sequenced so far. Mutations occurred in 166 genes, and 40 of these were recurrently somatically mutated in Ph-negative MPNs. By the Oncodrive-FM algorithm, the following genes were identified as the most significantly mutated driver genes in Ph-negative MPNs and MDS/MPDs (in order of significance): CALR, ASXL1, JAK2, CBL, DNMT3A, U2AF1, TET2, TP53, RUNX1, EZH2, SH2B3 and KIT. By the Oncodrive-cluster algorithm, which considers clustering of mutations at a hotspot, the following genes were significantly mutated: KIT, JAK2, SRSF2 and U2AF1. Somatic mutations were seen in genes that are mutated at a low frequency in Ph-negative MPNs, including ATRX, BCL11A, BCORL1, BIRC5, BRCC3, CSF2RB, CUX1, IRF1, KDM2B, ROS1 and SUZ12. Consistent with the clinical phenotype, 96 patients (94%) had mutations that lead to increased cellular proliferation, either through activation of the JAK-STAT pathway (e.g. JAK2, CALR) or mutations that activated directly or indirectly signaling by receptor tyrosine kinases (e.g. FLT3, KIT, CBL). Besides biological pathways regulating cell proliferation, the most commonly implicated pathways included regulation of DNA methylation (e.g. DNMT3A, TET2), mRNA splicing (e.g. U2AF1, SRSF2) and histone modifications (e.g. ASXL1, EZH2), seen in 27%, 25% and 22% of patients, respectively. Abnormalities in these 3 pathways were more often seen in MF, MDS/MPD and CMML, as compared to PV and ET (65% vs. 20%; p<0.0001). Conclusions: Our study represents one of the largest series of patients with these neoplasms evaluated by whole exome sequencing, and together with the published data helps to delineate the genomic landscape of Ph-negative MPNs and MDS/MPDs. The majority of the most frequent mutations seen in Ph-negative MPNs have already been reported. Nevertheless, there are several low frequency mutations that need to be further studied and functionally validated in vitro and in vivo for a deeper knowledge of the pathophysiology of MPNs. Besides activation of cellular proliferation, abnormalities of DNA methylation, histone modification and mRNA splicing emerge as the most important biological pathways in these disorders. Disclosures No relevant conflicts of interest to declare.

Background & Aim: Correlations between DNA variation and human phenotypic differences, such as susceptibility to certain diseases, are not well understood. Polymorphisms can contribute to the observed variation in complex human traits, but their relative contributions remain to be determined. Expression differences between alleles of the same gene have been observed, contributing to phenotypic variation between individuals. Studies showed that variations exist in the relative allelic expression levels in certain genes of heterozygote individuals. Polymorphism at codon 72 of TP53 results in either Arginine or Proline, whose functional significance in carcinogenesis is controversial. Studies showed that the Pro72 is less efficient than Arg72 allele in suppressing cell transformation and inducing apoptosis. We have investigated if the expression of these p53 polymorphs is selectively regulated, using mRNA and DNA from colorectal cancer tissues (CRC). Methods: 28 non-related patients treated at ACCamargo Cancer Center in Brazil were evaluated. DNA and RNA were isolated from frozen tumor tissue using Trizol and phenol/chloroform based protocol. TP53 sequences from DNA and RNA were evaluated by Sanger sequencing and quantified using Pyrosequencing. The assay for allele quantification was designed with the software PyroMark Assay Design Software 2.0, featuring algorithms for full quality control. Results: We found 28 p53 codon 72 SNP heterozygotes tumors and 11 (39.3%) of these showed differential expressions, and most of them preferentially expressed the Pro allele. Pyrogram peak heights are proportional to the frequency of an allele in the sample, providing accurate measures of the proportion of the alleles. Previous results revealed that these SNP expression was significantly associated with gender (P= 0.037), recurrence (P= .005), dirty tumor necrosis (P= 0.025), border pattern of tumor growth (P= 0.05), post chemoradiotherapy use (P= 0.002), p53 immunohistochemistry expression (P= 0.041) and TP53 mutation (P= 0.004), suggesting that the expression of the Pro72 allele is associated with worse tumor features. The expression of Arg72 (OR 3.83; CI 1.02-14.35; P= 0.046) and the TNM grouping stage (OR 7.15; CI 1.45-35.29; P= 0.016) were independent predictors for recurrence. This is the first report describing the differential expression of the p53 codon 72 SNP in CRC and revealed that heterozygotes preferentially express the Pro allele, suggesting that the Pro allele is selectively activated in CRC. Conclusions: The expression of the different p53 polymorphs is selectively regulated in Pro72Arg heterozygotes individuals. Thus, the expression status of the p53 polymorphs, rather than the genotypic status, might be an useful indicator tumor aggressiveness. Citation Format: Ligia P. Oliveira, Bianca G. Lisboa, Ignácio Lopez, Erika MM Santos, Dirce M. Carraro, Fernando A. Soares, Benedito M. Rossi, Renata A. Coudry. Differential expression of codon 72 of TP53 in colorectal tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 583. doi:10.1158/1538-7445.AM2014-583

Background & Aim: The tumor suppressor TP53 gene is one of the most frequently mutated in different types of human cancer. Particularly in colorectal cancer (CRC), it is believed that TP53 mutations play a role in the adenoma-carcinoma transition of tumors during pathological process. Alternative splicing expands the diversity of RNA transcripts and plays an important role in tissue-specific differentiation, what can be misregulated in diseases. The high value of silent mutations found in TP53 databases is much more than what would be expected if synonymous mutations were effectively neutral. Previous in silico studies suggested that p53 synonymous mutations colocalized with splicing sites. The purpose of this study was to determine the correct splicing patterns and to understand if synonymous mutations may affect TP53 function in tumoral processes by analyzing the complete coding region of TP53 mRNA searching for mutations involved with splicing mechanisms. Methods: Tumor samples from 101 patients with sporadic CRC from AC Camargo Hospital in Brazil were evaluated. RNA and DNA were isolated from frozen tumor tissue using Trizol and phenol/chloroform based protocol. TP53 sequences were evaluated by Sanger sequencing. Results: There were detected four deletions and four insertions. Of these, two deletions (c.159del1, c.792_796del5) and two insertions (c.672_673ins5, c.398_399ins4) were detected, to our knowledge, for the first time and submitted to GenBank. In addition, two deletions and one insertion lead to splicing variants or splicing errors, as the region deleted or inserted contains sequences that could be used as alternative splicing sites. The insertion results from a synonymous mutation. The other samples do not contain another mutation in RNA sequence that could be related to splicing errors. Considering the total number of alterations found, of the 42 types of alterations, 3 (7.1%) of them represent splicing variants, rate seven times higher than what was shown on TP53 IARC Database. The higher frequency could be explained by the strategy adopted for the screening, as the use of cDNA sequencing facilitated the detection of possible splicing variants that might have been underestimated in previous analyses using genomic approaches. Conclusion: The analysis of the whole transcript sequence of TP53 mRNA is important to determine the specific contribution of the alterations found. Synonymous mutations may alter p53 function. The findings strongly suggest that particular splicing modifications are associated with CRC and that there is considerably more transcript complexity than previously appreciated. Citation Format: Ligia P. Oliveira, Bianca Garcia Lisboa, Ignacio López, Mónica Marín, Dirce Maria Carraro, Renata de Almeida Coudry. Identification of TP53 splicing mutations in colorectal tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 785. doi:10.1158/1538-7445.AM2013-785

Background: Lynch syndrome (LS) is an autosomal dominant disorder predisposing to colorectal cancer and increased risk for cancers of the stomach, small intestine, hepatobiliary system, kidney, ureter, ovary, and sebaceous tumors. Germline mutations in the MMR genes MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), post- meiotic segregation increased 1 (PMS1) or post- meiotic segregation increased 2 (PMS2), are known to cause LS. While mutations in MLH1 and MSH2 gene, account for 70% - 80% of all Lynch syndrome colorectal cancers, the involvement of the MSH6, PMS2 and PMS1 gene is continually rising. Altogether, MSH6, PMS1 and PMS2 mutations account for 5-20% of kindreds in which MSH2 and MLH1 mutations are excluded. Objective: The aim of the study was evaluate the frequency of mutations in MSH6, PMS1 and PMS2 gene. Methods: Seventy one unrelated patients without MLH1/MSH2 mutations were eligible for this study. Genomic DNA was obtained from peripheral blood and primers were designed within introns of all exons of MSH6, PMS1 gene. In order to avoid the amplification of pseudogenes for the PMS2 gene, a set of four primer pairs were design. Results: Out of 71 patients, 20 fulfilled the Amsterdam criteria and other 51 fulfilled the Bethesda guideline. Four novel pathogenic mutations were detected, three in MSH6 and 1 in PMS2. In addition, 7 variants of uncertain significance were encountered, in which two of them were previously described as pathogenic. No mutations were found in PMS1 gene. Conclusion: Our data shows that 8.5% (6/71) of the individuals have mutations in MSH6 and PMS2 gene and these results strongly suggest that MSH6 and PMS2 should not be excluded from the MMR screening in Brazilian families suspected for Lynch syndrome. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2108. doi:1538-7445.AM2012-2108