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Replication Gaps Underlie BRCA Deficiency and Therapy Response.

ABSTRACT: Defects in DNA repair and the protection of stalled DNA replication forks are thought to underlie the chemosensitivity of tumors deficient in the hereditary breast cancer genes BRCA1 and BRCA2 (BRCA). Challenging this assumption are recent findings that indicate chemotherapies, such as cisplatin used to treat BRCA-deficient tumors, do not initially cause DNA double-strand breaks (DSB). Here, we show that ssDNA replication gaps underlie the hypersensitivity of BRCA-deficient cancer and that defects in homologous recombination (HR) or fork protection (FP) do not. In BRCA-deficient cells, ssDNA gaps developed because replication was not effectively restrained in response to stress. Gap suppression by either restoration of fork restraint or gap filling conferred therapy resistance in tissue culture and BRCA patient tumors. In contrast, restored FP and HR could be uncoupled from therapy resistance when gaps were present. Moreover, DSBs were not detected after therapy when apoptosis was inhibited, supporting a framework in which DSBs are not directly induced by genotoxic agents, but rather are induced from cell death nucleases and are not fundamental to the mechanism of action of genotoxic agents. Together, these data indicate that ssDNA replication gaps underlie the BRCA cancer phenotype, "BRCAness," and we propose they are fundamental to the mechanism of action of genotoxic chemotherapies. SIGNIFICANCE: This study suggests that ssDNA replication gaps are fundamental to the toxicity of genotoxic agents and underlie the BRCA-cancer phenotype "BRCAness," yielding promising biomarkers, targets, and opportunities to resensitize refractory disease.See related commentary by Canman, p. 1214.

SUBMITTER: Panzarino NJ

PROVIDER: S-EPMC8026497 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundGenetic testing, particularly for BRCA1/2, is increasingly important in prostate cancer (PCa) care, with impact on PCa management and hereditary cancer risk. However, the extent of public awareness and online discourse on social media is unknown, and presents opportunities to identify gaps and enhance population awareness and uptake of advances in PCa precision medicine.ObjectiveThe objective of this study was to characterize activity and engagement across multiple social media platforms (Twitter, Facebook, and YouTube) regarding BRCA and genetic testing for PCa compared with breast cancer, which has a long history of public awareness, advocacy, and prominent social media presence.MethodsThe Symplur Signals online analytics platform was used to obtain metrics for tweets about (1) #BRCA and #breastcancer, (2) #BRCA and #prostatecancer, (3) #genetictesting and #breastcancer, and (4) #genetictesting and #prostatecancer from 2016 to 2020. We examined the total number of tweets, users, and reach for each hashtag, and performed content analysis for a subset of tweets. Facebook and YouTube were queried using analogous search terms, and engagement metrics were calculated.ResultsDuring a 5-year period, there were 10,005 tweets for #BRCA and #breastcancer, versus 1008 tweets about #BRCA and #prostatecancer. There were also more tweets about #genetictesting and #breastcancer (n=1748), compared with #genetic testing and #prostatecancer (n=328). Tweets about genetic testing (12,921,954) and BRCA (75,724,795) in breast cancer also had substantially greater reach than those about PCa (1,463,777 and 4,849,905, respectively). Facebook groups and pages regarding PCa and BRCA/genetic testing had fewer average members, new members, and new posts, as well as fewer likes and followers, compared with breast cancer. Facebook videos had more engagement than YouTube videos across both PCa and breast cancer content.ConclusionsThere is substantially less social media engagement about BRCA and genetic testing in PCa compared with breast cancer. This landscape analysis provides insights into strategies for leveraging social media platforms to increase public awareness about PCa germline testing, including use of Facebook to share video content and Twitter for discussions with health professionals.

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Replication Gaps Underlie BRCA Deficiency and Therapy Response.

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