Ovarian cancer onset across different BRCA mutation types: a view to a more tailored approach for BRCA mutated patients.

OBJECTIVE: To evaluate the role of different specific types of germline breast cancer susceptibility BRCA mutations on the age of onset of high grade serous ovarian cancer. METHODS: This was a multicenter, international, retrospective cohort of 474 patients diagnosed with recurrent or newly diagnosed high grade serous ovarian cancer, with known germline mutations in BRCA1/2 genes, treated between January 2011 and December 2020 in three academic centers in Europe. Patients were classified into four groups related to the type of BRCA1/2 genes mutation: frameshift, missense, nonsense, and splicing. Data from patients with splicing mutations were removed from the analysis because of the small numbers. The other three groups were compared. RESULTS: Excluding the 29 patients with a splicing mutation, 474 patients were enrolled: 309 (65.2%) with frameshift mutations, 102 (21.5%) with nonsense mutations, and 63 (13.3%) with missense mutations. The BRCA1 gene was affected in 324 (68.4%) cases, while BRCA2 was involved in 150 (31.6%) women (p=0.06). We found a difference of more than 5 years in the age of onset of high grade serous ovarian cancer between BRCA1 and BRCA2 patients (mean 53.3 years vs 58.4 years; p=0.001), with a mean age of 55.1 years. Patients with nonsense germline mutations had the youngest age of onset, while women with frameshift mutations had the oldest age of onset of high grade serous ovarian cancer (mean 52.2 years vs mean 55.9 years), both in the BRCA1 and BRCA2 subgroups. There was no statistically significant difference in age of onset between early and advanced groups (mean 55.8 years vs 55.0 years; p=0.55). CONCLUSION: Different types of germline BRCA mutations could determine different ages for onset of high grade serous ovarian cancer. If confirmed in larger series, this finding might have a clinical impact, potentially leading to a more tailored approach for risk reducing surgery for the prevention of high grade serous ovarian cancer.

PI3K/mTOR inhibition induces tumour microenvironment remodelling and sensitises pS6high uterine leiomyosarcoma to PD-1 blockade.

BACKGROUND: Uterine leiomyosarcomas (uLMS) are aggressive tumours with poor prognosis and limited treatment options. Although immune checkpoint blockade (ICB) has proven effective in some 'challenging-to-treat' cancers, clinical trials showed that uLMS do not respond to ICB. Emerging evidence suggests that aberrant PI3K/mTOR signalling can drive resistance to ICB. We therefore explored the relevance of the PI3K/mTOR pathway for ICB treatment in uLMS and explored pharmacological inhibition of this pathway to sensitise these tumours to ICB. METHODS: We performed an integrated multiomics analysis based on TCGA data to explore the correlation between PI3K/mTOR dysregulation and immune infiltration in 101 LMS. We assessed response to PI3K/mTOR inhibitors in immunodeficient and humanized uLMS patient-derived xenografts (PDXs) by evaluating tumour microenvironment modulation using multiplex immunofluorescence. We explored response to single-agent and a combination of PI3K/mTOR inhibitors with PD-1 blockade in humanized uLMS PDXs. We mapped intratumoural dynamics using single-cell RNA/TCR sequencing of serially collected biopsies. RESULTS: PI3K/mTOR over-activation (pS6high) associated with lymphocyte depletion and wound healing immune landscapes in (u)LMS, suggesting it contributes to immune evasion. In contrast, PI3K/mTOR inhibition induced profound tumour microenvironment remodelling in an ICB-resistant humanized uLMS PDX model, fostering adaptive anti-tumour immune responses. Indeed, PI3K/mTOR inhibition induced macrophage repolarisation towards an anti-tumourigenic phenotype and increased antigen presentation on dendritic and tumour cells, but also promoted infiltration of PD-1+ T cells displaying an exhausted phenotype. When combined with anti-PD-1, PI3K/mTOR inhibition led to partial or complete tumour responses, whereas no response to single-agent anti-PD-1 was observed. Combination therapy reinvigorated exhausted T cells and induced clonal hyper-expansion of a cytotoxic CD8+ T-cell population supported by a CD4+ Th1 niche. CONCLUSIONS: Our findings indicate that aberrant PI3K/mTOR pathway activation contributes to immune escape in uLMS and provides a rationale for combining PI3K/mTOR inhibition with ICB for the treatment of this patient population.