Purpose: Germline alterations in homologous recombination repair (gHRR) genes affect the pathogenesis, treatment options, and survival of patients with cancer. However, distinct gHRR gene alterations may differentially affect treatment response and oncogenic signaling. In this study, we interrogated genomic and transcriptomic data and assessed clinical outcomes of patients with gHRR mutations across four BRCA-associated cancers (breast, ovarian, pancreatic, and prostate cancers) to identify therapeutic vulnerabilities. Experimental Design: We assessed 24,309 patients undergoing matched tumor/normal next-generation DNA and RNA sequencing. Annotated gHRR gene variants [germline BRCA1, germline BRCA2, germline PALB2, germline ATM (gATM), and germline CHEK2] were analyzed. HRs were used to assess survival outcomes comparing germline versus sporadic groups. Somatic alterations and their frequencies were compared across gHRR-altered groups. Differential gene expression and gene set enrichment analysis were used to compare transcriptomic profiles. Results: Somatic TP53 mutations were depleted in gATM carriers (P < 0.05) across all four BRCA-associated cancers by up to 2.5-fold. Tumors with germline BRCA1/2 mutations were associated with improved survival in patients with ovarian cancer and had consistent enrichment of TP53 mutations in all four cancers. gATM mutations displayed elevated p53 transcriptional activity in all four cancers, with significance reached in breast and prostate cancers (P < 0.01). In breast, ovarian, and prostate cancers, gATM tumors demonstrated significantly increased inflammatory pathways (P < 0.001). Finally, using gene dependency data, we found that cell lines that were highly dependent on ATM were co-dependent on canonical p53 function. Conclusions: gATM-associated cancers seem to require intact p53 activity and this synthetic essentiality may be used to guide targeted therapies that perturb canonical TP53 function.

Background/Objectives: The germline polymorphism in the HSD3B1 gene (c.1100 C) results in adrenal-permissive (CC) or adrenal-restrictive (AA) functions of the protein product by regulating the production of high-affinity ligands that activate androgen signaling. Prior studies have indicated that the CC genotype is associated with worse response to hormonal therapies in prostate cancer (PC) patients. Methods: To characterize the impact of germline HSD3B1 variants on somatic tumor features, we examined 6550 primary and metastatic PCs from the Caris Life Sciences database, in which the genomic and transcriptomic landscapes were acquired via paired whole-exome/whole-transcriptome sequencing. Results: The overall prevalence of the HSD3B1 AA genotype (restrictive–homozygous) was 48.8%, AC (permissive–heterozygous) was 32.8%, and CC (permissive–homozygous) was 14.9%. There was enrichment of the CC genotype in these PC patients as compared to prior reports that examined non-cancerous populations. However, the rates of the CC genotype varied between metastatic site and by race. Compared to the AA genotype, tumors harboring the CC genotype did not demonstrate increased AR alterations, nor higher expression of AR, FOXA1, HOXB13, or AR signaling signatures. We instead found significant changes in immune-associated hallmark pathways, immune cell fractions, and biomarkers that inform the use of immune therapies (TMB-high, MSI-high). Further, the CC and AA genotypes exhibited notable differences in the expression of immunoglobulins, MHC class I/II molecules, and cell surface targets. The differences in expression by HSD3B1 genotype were especially notable in lung and liver metastases. Conclusions: Our study indicates that in prostate cancers, HSD3B1 germline c.1100 allele status may not directly influence tumor-intrinsic genomics but is associated with novel functions beyond androgen signaling.

Fischer Exact T-test comparison between racial subgroups

Violin plots depicting somatic TMB