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1. Oncogenic KRAS alters splicing factor phosphorylation and alternative splicing in lung cancer

   https://doi.org/10.1186/s12885-022-10311-1  

   Lo, April ; McSharry, Maria ; Berger, Alice H. ( December 2022 , BMC Cancer)

   Alternative RNA splicing is widely dysregulated in cancers including lung adenocarcinoma, where aberrant splicing events are frequently caused by somatic splice site mutations or somatic mutations of splicing factor genes. However, the majority of mis-splicing in cancers is unexplained by these known mechanisms. We hypothesize that the aberrant Ras signaling characteristic of lung cancers plays a role in promoting the alternative splicing observed in tumors.

   We recently performed transcriptome and proteome profiling of human lung epithelial cells ectopically expressing oncogenic KRAS and another cancer-associated Ras GTPase, RIT1. Unbiased analysis of phosphoproteome data identified altered splicing factor phosphorylation in KRAS-mutant cells, so we performed differential alternative splicing analysis using rMATS to identify significantly altered isoforms in lung epithelial cells. To determine whether these isoforms were uniquely regulated by KRAS, we performed a large-scale splicing screen in which we generated over 300 unique RNA sequencing profiles of isogenic A549 lung adenocarcinoma cells ectopically expressing 75 different wild-type or variant alleles across 28 genes implicated in lung cancer.

   Mass spectrometry data showed widespread downregulation of splicing factor phosphorylation in lung epithelial cells expressing mutant KRAS compared to cells expressing wild-type KRAS. We observed alternative splicing in the same cells, with 2196 and 2416 skipped exon events in KRAS^G12Vand KRAS^Q61Hcells, respectively, 997 of which were shared (p < 0.001 by hypergeometric test). In the high-throughput splicing screen, mutant KRAS induced the greatest number of differential alternative splicing events, second only to the RNA binding protein RBM45 and its variant RBM45^M126I. We identified ten high confidence cassette exon events across multiple KRAS variants and cell lines. These included differential splicing of the Myc Associated Zinc Finger (MAZ). As MAZ regulates expression of KRAS, this splice variant may be a mechanism for the cell to modulate wild-type KRAS levels in the presence of oncogenic KRAS.

   Proteomic and transcriptomic profiling of lung epithelial cells uncovered splicing factor phosphorylation and mRNA splicing events regulated by oncogenic KRAS. These data suggest that in addition to widespread transcriptional changes, the Ras signaling pathway can promote post-transcriptional splicing changes that may contribute to oncogenic processes.

    

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2. A Tunisian family with a novel mutation in the gene CYP4F22 for lamellar ichthyosis and co‐occurrence of hearing loss in a child due to mutation in the SLC26A4 gene

   https://doi.org/10.1111/ijd.14452  

   Sayeb, Marwa ; Riahi, Zied ; Laroussi, Nadia ; Bonnet, Crystel ; Romdhane, Lilia ; Mkaouar, Rahma ; Zaouak, Anissa ; Marrakchi, Jihene ; Abdessalem, Ghaith ; Messaoud, Olfa ; et al ( April 2019 , International Journal of Dermatology)

   Co‐occurrence of two genetic diseases is challenging for accurate diagnosis and genetic counseling. The recent availability of whole exome sequencing (WES) has dramatically improved the molecular diagnosis of rare genetic diseases in particular in consanguineous populations.

   We report here on a consanguineous family from Southern Tunisia including three members affected with congenital ichthyosis. The index case had a hearing loss (HL) and ichthyosis and was primarily suspected as suffering from keratitis‐ichthyosis‐deafness (KID) syndrome.WESwas performed for the index case, and all members of the nuclear family were sequenced (Sanger method).

   TheWESapproach allowed the identification of two strong candidate variants in two different genes; a missense mutation c.1334T>G (p.Leu445Trp) in exon 11 ofSLC26A4gene, associated with isolatedHLand a novel missense mutation c.728G>T (p.Arg243Leu) in exon 8 ofCYP4F22gene likely responsible for ichthyosis. These two mutations were predicted to be pathogenic by three pathogenicity prediction softwares (Scale‐Invariant Feature Transform [SIFT], Polymorphism Phenotyping [PolyPhen], Mutation Taster) to underlie theHLand ichthyosis, respectively.

   The present study raises awareness about the importance of familial history for accurate diagnosis of syndromic genetic diseases and differential diagnosis with co‐occurrence of two distinct clinical entities. In addition, in countries with limited resources,WESsequencing for a single individual provides a cost effective tool for molecular diagnosis confirmation and genetic counseling.

    

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3. Incorporating mutational heterogeneity to identify genes that are enriched for synonymous mutations in cancer

   https://doi.org/10.1186/s12859-023-05521-8  

   Rao, Yiyun ; Ahmed, Nabeel ; Pritchard, Justin ; O’Brien, Edward P. ( December 2023 , BMC Bioinformatics)

   Synonymous mutations, which change the DNA sequence but not the encoded protein sequence, can affect protein structure and function, mRNA maturation, and mRNA half-lives. The possibility that synonymous mutations might be enriched in cancer has been explored in several recent studies. However, none of these studies control for all three types of mutational heterogeneity (patient, histology, and gene) that are known to affect the accurate identification of non-synonymous cancer-associated genes. Our goal is to adopt the current standard for non-synonymous mutations in an investigation of synonymous mutations.

   Here, we create an algorithm, MutSigCVsyn, an adaptation of MutSigCV, to identify cancer-associated genes that are enriched for synonymous mutations based on a non-coding background model that takes into account the mutational heterogeneity across these levels. Using MutSigCVsyn, we first analyzed 2572 cancer whole-genome samples from the Pan-cancer Analysis of Whole Genomes (PCAWG) to identify non-synonymous cancer drivers as a quality control. Indicative of the algorithm accuracy we find that 58.6% of these candidate genes were also found in Cancer Census Gene (CGC) list, and 66.2% were found within the PCAWG cancer driver list. We then applied it to identify 30 putative cancer-associated genes that are enriched for synonymous mutations within the same samples. One of the promising gene candidates is the B cell lymphoma 2 (BCL-2) gene. BCL-2 regulates apoptosis by antagonizing the action of proapoptotic BCL-2 family member proteins. The synonymous mutations in BCL2 are enriched in its anti-apoptotic domain and likely play a role in cancer cell proliferation.

   Our study introduces MutSigCVsyn, an algorithm that accounts for mutational heterogeneity at patient, histology, and gene levels, to identify cancer-associated genes that are enriched for synonymous mutations using whole genome sequencing data. We identified 30 putative candidate genes that will benefit from future experimental studies on the role of synonymous mutations in cancer biology.

    

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4. Assessment of genetic susceptibility to multiple primary cancers through whole-exome sequencing in two large multi-ancestry studies

   https://doi.org/10.1186/s12916-022-02535-6  

   Cavazos, Taylor B. ; Kachuri, Linda ; Graff, Rebecca E. ; Nierenberg, Jovia L. ; Thai, Khanh K. ; Alexeeff, Stacey ; Van Den Eeden, Stephen ; Corley, Douglas A. ; Kushi, Lawrence H. ; Regeneron Genetics Center ; et al ( October 2022 , BMC Medicine)

   Up to one of every six individuals diagnosed with one cancer will be diagnosed with a second primary cancer in their lifetime. Genetic factors contributing to the development of multiple primary cancers, beyond known cancer syndromes, have been underexplored.

   To characterize genetic susceptibility to multiple cancers, we conducted a pan-cancer, whole-exome sequencing study of individuals drawn from two large multi-ancestry populations (6429 cases, 165,853 controls). We created two groupings of individuals diagnosed with multiple primary cancers: (1) an overall combined set with at least two cancers across any of 36 organ sites and (2) cancer-specific sets defined by an index cancer at one of 16 organ sites with at least 50 cases from each study population. We then investigated whether variants identified from exome sequencing were associated with these sets of multiple cancer cases in comparison to individuals with one and, separately, no cancers.

   We identified 22 variant-phenotype associations, 10 of which have not been previously discovered and were significantly overrepresented among individuals with multiple cancers, compared to those with a single cancer.

   Overall, we describe variants and genes that may play a fundamental role in the development of multiple primary cancers and improve our understanding of shared mechanisms underlying carcinogenesis.

    

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5. Comparison of germline mutations in African American and Caucasian men with metastatic prostate cancer

   https://doi.org/10.1002/pros.24123  

   Ledet, Elisa M. ; Burgess, Earle F. ; Sokolova, Alexandra O. ; Jaeger, Ellen B. ; Hatton, Whitley ; Moses, Marcus ; Miller, Patrick ; Cotogno, Patrick ; Layton, Jodi ; Barata, Pedro ; et al ( April 2021 , The Prostate)

   The goal of this study is to evaluate germline genetic variants in African American men with metastatic prostate cancer as compared to those in Caucasian men with metastatic prostate cancer in an effort to understand the role of genetic factors in these populations.

   African American and Caucasian men with metastatic prostate cancer who had germline testing using multigene panels were used to generate comparisons. Germline genetic results, clinical parameters, and family histories between the two populations were analyzed.

   A total of 867 patients were included in this retrospective study, including 188 African American and 669 Caucasian patients. There was no significant difference in the likelihood of a pathogenic or likely‐pathogenic variants (PV/LPVs) between African American and Caucasian patients (p = .09). African American patients were more likely to have a variant of unknown significance than Caucasians (odds ratio [OR] = 1.95;p < .0001). BRCA1 PV/LPVs were higher in African Americans (OR = 4.86;p = .04). African American patients were less likely to have a PV/LPV in non‐BRCA DNA repair genes (OR = 0.30;p = .008). Family history of breast (OR = 2.09;p = .002) or ovarian cancer (OR = 2.33;p = .04) predicted PV/LPVs in Caucasians but not African‐Americans. This underscores the limitations of family history in AA men and the importance of personal history to guide germline testing in AA men.

   In metastatic prostate cancer patients, PV/LPVs of tested genes did not vary by race, BRCA1 PV/LPVs were more common in the African American subset. However, PV/LPVs in non‐BRCA DNA repair genes were less likely to be encountered in African Americans. Family history associated with genetic testing results in Caucasians only.

    

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