Unraveling the complexity of HRD assessment in ovarian cancer by combining genomic and functional approaches: translational analyses of MITO16-MaNGO-OV-2 trial

Abstract

Background: Ovarian cancer (OvC) constitutes significant management challenges primarily due to its late-stage diagnosis and the development of resistance to chemotherapy. The standard treatment regimen typically includes carboplatin and paclitaxel, with the addition of poly (ADP-ribose) polymerase inhibitors for patients with high-grade serous ovarian cancer (HGSOC) harboring BRCA1/2 mutations. However, the variability in treatment responses suggests the need to investigate factors beyond BRCA1/2 mutations, such as DNA repair mechanisms and epigenetic alterations. Notably, homologous recombination repair deficiency (HRD) is observed in an additional 20% of HGSOC cases, indicating a broader spectrum of DNA repair defects. Existing commercial HRD assays have certain limitations, prompting a global effort to develop new genomic and functional tests through academic research.

Materials and methods: This study investigates, in the 187 high-grade serous and endometrioid tumors from the MITO16/MaNGO-OV-2 trial, academic HRD genomic tests in conjunction with a RAD51 immunofluorescence assay to assess functional activation of HRD. Additionally, the study incorporates analysis of microRNA-506 (miR-506) expression as a putative epigenetic effector.

Results: The RAD51 test identified HRD in 73% of the samples and genomic HRD testing in 57%, with HRD identified in 45% of samples by both tests. The significant discrepancy between the two assays emphasizes the need to refine tumor classification for HRD. A three-group genomic classification unveiled superior progression-free survival (PFS) in high- and mild-HRD tumors compared with negative-HRD tumors. High concordance between RAD51 and genomic testing in high-HRD tumors suggests a subset of 'super-HRD' tumors exhibiting superior PFS. High expression of miR-506 may be used to further refine HRD status.

Conclusions: The study underscores the complexities of HRD assessment and advocates for a combined genomic and functional approach to enhance predictive accuracy in OvC treatment responses.

Keywords: HRD; RAD51; miR-506; ovarian cancer.

Figure 1

Functional HRD in ovarian cancer according to RAD51 assay. (A) Distribution of γH2AX: γH2AX is the main sensor of the HRR pathway; the presence of γH2AX foci in >25% of geminin-positive cells indicates the presence of double-strand breaks and it is the internal positive control of the RAD51 assay. (B) Distribution of BRCA1: BRCA1 is a mediator of the HRR pathway; the presence of BRCA1 foci in >10% of geminin-positive cells indicates the correct functionality of the BRCA1 protein. (C) Distribution of RAD51: RAD51 is the main effector of the HRR pathway; the presence of RAD51 foci in at least 10% of geminin-positive cells reveals the correct functionality of the HRR pathway. Dotted lines represent each cut-off for positive expression. HRD, homologous recombination repair deficiency; HRR, homologous recombination repair.

Figure 2

Prognostic role of functional and genomic HRD. (A) PFS in HRD and HRP tumors according to RAD51 assay. (B) OS in HRD and HRP tumors according to RAD51 assay. (C) PFS in HRD and neg-HRD tumors according to genomic HRD assay. (D) OS in HRD and neg-HRD tumors according to genomic HRD assay. (E) PFS in high-HRD, mild-HRD and neg-HRD tumors according to genomic HRD assay. (F) OS in high-HRD, mild-HRD and neg-HRD tumors according to genomic HRD assay. HRD, homologous recombination repair deficiency; HRP, homologous recombination repair proficient; neg, negative; OS, overall survival; PFS, progression-free survival.

Figure 3

Prognostic role of combined functional and genomic HRD test. (A) PFS in HRD tumors for at least one HRD test compared with HRP tumors for both tests. (B) OS in HRD tumors for at least one HRD test compared with HRP tumors for both tests. HRD, homologous recombination repair deficiency; HRP, homologous recombination repair proficient; OS, overall survival; PFS, progression-free survival.