DNA Damage Response and Mismatch Repair Gene Defects in Advanced and Metastatic Prostate Cancer

Alterations in DNA damage response (DDR) and related genes are present in up to 25% of advanced prostate cancers (PCa). Most frequently altered genes are involved in the homologous recombination repair, the Fanconi anemia, and the mismatch repair pathways, and their deficiencies lead to a highly heterogeneous spectrum of DDR-deficient phenotypes. More than half of these alterations concern non- BRCA DDR genes. From a therapeutic perspective, poly-ADP-ribose polymerase inhibitors have demonstrated robust clinical efficacy in tumors with BRCA2 and BRCA1 alterations. Mismatch repair-deficient PCa, and a subset of CDK12-deficient PCa, are vulnerable to immune checkpoint inhibitors. Emerging data point to the efficacy of ATR inhibitors in PCa with ATM deficiencies. Still, therapeutic implications are insufficiently clarified for most of the non- BRCA DDR alterations, and no successful targeted treatment options have been established.

Fanconi Anemia Pathway Genes Advance Cervical Cancer via Immune Regulation and Cell Adhesion

Fanconi anemia (FA) pathway is a typical and multienzyme-regulated DNA damage repairer that influences the occurrence and development of disease including cancers. Few comprehensive analyses were reported about the role of FA-related genes (FARGs) and their prognostic values in cancers. In this study, a comprehensive pan-cancer analysis on 79 FARGs was performed. According to the correlation analyses between HPV integration sites and FARGs, we found that FARGs played specific and critical roles in HPV-related cancers, especially in cervical cancer (CC). Based on this, a FARGs-associated prognostic risk score (FPS) model was constructed, and subsequently a nomogram model containing the FPS was developed with a good accuracy for CC overall survival (OS) and recurrence-free survival (RFS) outcome prediction. We also used the similar expression pattern of FARGs by consensus clustering analysis to separate the patients into three subgroups that exhibited significant differential OS but not RFS. Moreover, differential expressed genes (DEGs) between the two risk groups or three clusters were identified and immune pathways as well as cell adhesion processes were determined by functional enrichment analysis. Results indicated that FARGs might promote occurrence and development of CC by regulating the immune cells' infiltration and cell adhesion. In addition, through the machine learning models containing decision tree, random forest, naïve bayes, and support vector machine models, screening of important variables on CC prognosis, we finally determined that ZBTB32 and CENPS were the main elements affecting CC OS, while PALB2 and BRCA2 were for RFS. Kaplan-Meier analysis revealed that bivariate prediction of CC outcome was reliable. Our study systematically analyzed the prognostic prediction values of FARGs and demonstrated their potential mechanism in CC aggressiveness. Results provided perspective in FA pathway-associated modification and theoretical basis for CC clinical treatments.

Clear Cell Papillary Renal Cell Carcinoma Shares Distinct Molecular Characteristics and may be Significantly Associated With Higher Risk of Developing Second Primary Malignancy

Traditionally, clear cell papillary renal cell carcinoma (ccpRCC) was considered to share similar molecular and histological characteristics with clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC). Here we aimed to identify somatic and germline variants of ccpRCC. For this purpose, we conducted whole-exome sequencing to detect somatic variants in the tissues of 18 patients with pathologically confirmed ccpRCC, who underwent surgical treatment at Fudan University Shanghai Cancer Center. Targeted sequencing was conducted to detect germline variants in paired tumor or normal tissues or blood. Somatic and germline variants of ccRCC and Renal cell carcinoma included in The Cancer Genome Atlas data and other published data were analyzed as well. The molecular profiles of ccpRCC, ccRCC and pRCC were compared. Among the 387 somatic variants identified, TCEB1 (3/18) and VHL (3/18) variants occurred at the highest frequencies. Germline mutation detection showed that nine variants associated with Fanconi anemia (VAFAs) pathway (FANCA, 6/18; FANCI, 3/18) were identified in 18 ccpRCC patients. Among ccpRCC patients with VAFAs, five out of eight patients had second primary malignancy or family history of cancer. Somatic variants characteristics may distinguish ccpRCC from ccRCC or pRCC and germline VAFAs may be a molecular characterization of ccpRCC. Compared with ccRCC or pRCC, ccpRCC patients may be significantly correlated with higher risk of developing second primary malignancy.

Loss of the transforming growth factor-β effector β2-Spectrin promotes genomic instability

Exposure to genotoxins such as ethanol-derived acetaldehyde leads to DNA damage and liver injury and promotes the development of cancer. We report here a major role for the transforming growth factor β/mothers against decapentaplegic homolog 3 adaptor β2-Spectrin (β2SP, gene Sptbn1) in maintaining genomic stability following alcohol-induced DNA damage. β2SP supports DNA repair through β2SP-dependent activation of Fanconi anemia complementation group D2 (Fancd2), a core component of the Fanconi anemia complex. Loss of β2SP leads to decreased Fancd2 levels and sensitizes β2SP mutants to DNA damage by ethanol treatment, leading to phenotypes that closely resemble those observed in animals lacking both aldehyde dehydrogenase 2 and Fancd2 and resemble human fetal alcohol syndrome. Sptbn1-deficient cells are hypersensitive to DNA crosslinking agents and have defective DNA double-strand break repair that is rescued by ectopic Fancd2 expression. Moreover, Fancd2 transcription in response to DNA damage/transforming growth factor β stimulation is regulated by the β2SP/mothers against decapentaplegic homolog 3 complex.

CONCLUSION

Dysfunctional transforming growth factor β/β2SP signaling impacts the processing of genotoxic metabolites by altering the Fanconi anemia DNA repair pathway. (Hepatology 2017;65:678-693).