Among patients with advanced breast cancer and a germline BRCA1/2 mutation, single-agent talazoparib provided a significant benefit over standard chemotherapy with respect to progression-free survival. Patient-reported outcomes were superior with talazoparib. (Funded by Medivation [Pfizer]; EMBRACA ClinicalTrials.gov number, NCT01945775 .).

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NK cells are a major component of the antitumor immune response and are involved in controlling tumor progression and metastases in animal models. Here, we show that dysfunction of these cells accompanies human breast tumor progression. We characterized human peripheral blood NK (p-NK) cells and malignant mammary tumor-infiltrating NK (Ti-NK) cells from patients with noninvasive and invasive breast cancers. NK cells isolated from the peripheral blood of healthy donors and normal breast tissue were used as controls. With disease progression, we found that expression of activating NK cell receptors (such as NKp30, NKG2D, DNAM-1, and CD16) decreased while expression of inhibitory receptors (such as NKG2A) increased and that this correlated with decreased NK cell function, most notably cytotoxicity. Importantly, Ti-NK cells had more pronounced impairment of their cytotoxic potential than p-NK cells. We also identified several stroma-derived factors, including TGF-β1, involved in tumor-induced reduction of normal NK cell function. Our data therefore show that breast tumor progression involves NK cell dysfunction and that breast tumors model their environment to evade NK cell antitumor immunity. This highlights the importance of developing future therapies able to restore NK cell cytotoxicity to limit/prevent tumor escape from antitumor immunity. IntroductionBreast cancer (BC) is the primary cause of cancer deaths in women. The main cause of this mortality is the metastatic spread to other organs (1). Metastasis occurs when tumor cells acquire invasive features (2) and the ability to escape from antitumor immunity (3, 4). Defects in antitumor immunity may also facilitate BC occurrence. Indeed, mice deficient in IFN-γ production spontaneously develop mammary tumors (5). Breast tumor cells transplanted into NOD/SCID mice (which lack adaptive immunity) form noninvasive tumors, whereas the same cells transplanted into NOD/SCID/γ-c null mice (no adaptive immunity and no NK cells) form invasive tumors that metastasize rapidly (6). This effect is strictly dependent on NK cells (7). Similarly, in a highly metastatic model, BC metastasized to the lung only after elimination of NK cells by Tregs (8).Advanced BC patients show defects in antitumor immunity, such as alterations of DC maturation (9) and an increase in Treg infiltrates (10). Major impairment of peripheral blood NK cell maturation and cytotoxic functions has also been reported in metastatic BC (11). Several gene expression profiling studies have shown that a better outcome is associated with a strong cytotoxic infiltrate containing NK cells (12)(13)(14)(15). These data suggest that BC progression is linked to antitumor immunity efficiency and particularly to NK cells. However, the precise relationships between NK cells and BC progression in humans have not been studied so far.

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BackgroundMajor advances have been achieved in the characterization of early breast cancer (eBC) genomic profiles. Metastatic breast cancer (mBC) is associated with poor outcomes, yet limited information is available on the genomic profile of this disease. This study aims to decipher mutational profiles of mBC using next-generation sequencing.Methods and FindingsWhole-exome sequencing was performed on 216 tumor–blood pairs from mBC patients who underwent a biopsy in the context of the SAFIR01, SAFIR02, SHIVA, or Molecular Screening for Cancer Treatment Optimization (MOSCATO) prospective trials. Mutational profiles from 772 primary breast tumors from The Cancer Genome Atlas (TCGA) were used as a reference for comparing primary and mBC mutational profiles. Twelve genes (TP53, PIK3CA, GATA3, ESR1, MAP3K1, CDH1, AKT1, MAP2K4, RB1, PTEN, CBFB, and CDKN2A) were identified as significantly mutated in mBC (false discovery rate [FDR] < 0.1). Eight genes (ESR1, FSIP2, FRAS1, OSBPL3, EDC4, PALB2, IGFN1, and AGRN) were more frequently mutated in mBC as compared to eBC (FDR < 0.01). ESR1 was identified both as a driver and as a metastatic gene (n = 22, odds ratio = 29, 95% CI [9–155], p = 1.2e-12) and also presented with focal amplification (n = 9) for a total of 31 mBCs with either ESR1 mutation or amplification, including 27 hormone receptor positive (HR+) and HER2 negative (HER2−) mBCs (19%). HR+/HER2− mBC presented a high prevalence of mutations on genes located on the mechanistic target of rapamycin (mTOR) pathway (TSC1 and TSC2) as compared to HR+/HER2− eBC (respectively 6% and 0.7%, p = 0.0004). Other actionable genes were more frequently mutated in HR+ mBC, including ERBB4 (n = 8), NOTCH3 (n = 7), and ALK (n = 7). Analysis of mutational signatures revealed a significant increase in APOBEC-mediated mutagenesis in HR+/HER2− metastatic tumors as compared to primary TCGA samples (p < 2e-16). The main limitations of this study include the absence of bone metastases and the size of the cohort, which might not have allowed the identification of rare mutations and their effect on survival.ConclusionsThis work reports the results of the analysis of the first large-scale study on mutation profiles of mBC. This study revealed genomic alterations and mutational signatures involved in the resistance to therapies, including actionable mutations.