Pure estrogen receptor antagonists potentiate capecitabine activity in ESR1-mutant breast cancer.

The ESR1 ligand binding domain activating mutations are the most prevalent genetic mechanism of acquired endocrine resistance in metastatic hormone receptor-positive breast cancer. These mutations confer endocrine resistance that remains estrogen receptor (ER) dependent. We hypothesized that in the presence of the ER mutations, continued ER blockade with endocrine therapies that target mutant ER is essential for tumor suppression even with chemotherapy treatment. Here, we conducted comprehensive pre-clinical in vitro and in vivo experiments testing the efficacy of adding fulvestrant to fluorouracil (5FU) and the 5FU pro-drug, capecitabine, in models of wild-type (WT) and mutant ER. Our findings revealed that while this combination had an additive effect in the presence of WT-ER, in the presence of the Y537S ER mutation there was synergy. Notably, these effects were not seen with the combination of 5FU and selective estrogen receptor modulators, such as tamoxifen, or in the absence of intact P53. Likewise, in a patient-derived xenograft (PDX) harboring a Y537S ER mutation the addition of fulvestrant to capecitabine potentiated tumor suppression. Moreover, multiplex immunofluorescence revealed that this effect was due to decreased cell proliferation in all cells expressing ER and was not dependent on the degree of ER expression. Taken together, these results support the clinical investigation of the combination of ER antagonists with capecitabine in patients with metastatic hormone receptor-positive breast cancer who have experienced progression on endocrine therapy and targeted therapies, particularly in the presence of an ESR1 activating mutation.

Endocrine Therapy Synergizes with SMAC Mimetics to Potentiate Antigen Presentation and Tumor Regression in Hormone Receptor-Positive Breast Cancer.

Immunotherapies have yet to demonstrate significant efficacy in the treatment of hormone receptor-positive (HR+) breast cancer. Given that endocrine therapy (ET) is the primary approach for treating HR+ breast cancer, we investigated the effects of ET on the tumor immune microenvironment (TME) in HR+ breast cancer. Spatial proteomics of primary HR+ breast cancer samples obtained at baseline and after ET from patients enrolled in a neoadjuvant clinical trial (NCT02764541) indicated that ET upregulated ß2-microglobulin and influenced the TME in a manner that promotes enhanced immunogenicity. To gain a deeper understanding of the underlying mechanisms, the intrinsic effects of ET on cancer cells were explored, which revealed that ET plays a crucial role in facilitating the chromatin binding of RelA, a key component of the NF-κB complex. Consequently, heightened NF-κB signaling enhanced the response to interferon-gamma, leading to the upregulation of ß2-microglobulin and other antigen presentation-related genes. Further, modulation of NF-κB signaling using a SMAC mimetic in conjunction with ET augmented T-cell migration and enhanced MHC-I-specific T-cell-mediated cytotoxicity. Remarkably, the combination of ET and SMAC mimetics, which also blocks prosurvival effects of NF-κB signaling through the degradation of inhibitors of apoptosis proteins, elicited tumor regression through cell autonomous mechanisms, providing additional support for their combined use in HR+ breast cancer. SIGNIFICANCE: Adding SMAC mimetics to endocrine therapy enhances tumor regression in a cell autonomous manner while increasing tumor immunogenicity, indicating that this combination could be an effective treatment for HR+ patients with breast cancer.

Efficacy of immune check-point inhibitors (ICPi) in large cell neuroendocrine tumors of lung (LCNEC).

OBJECTIVES: Little is known regarding the ICPi efficacy in LCNEC. We explored the efficacy and safety of ICPi in LCNEC and assessed its impact on OS. MATERIALS AND METHODS: Thirty-seven consecutive patients with advanced LCNEC were selected from the Davidoff Cancer Center database. These were divided into groups A1 (patients treated with ICPi, n-23) and A2 (patients not treated with ICPi, n-14). Additionally, group A1* was introduced (patients treated with ICPi as a monotherapy, n-21). Another cohort of advanced non-LCNEC lung cancer patients treated with nivolumab at five Israeli cancer centers was chosen as a comparator (group B, n-270). ORR, PFS with ICPi in group A1* were assessed (RECIST 1.1), OS with ICPi was compared between groups A1* and B. OS since advanced disease diagnosis (OSDx) was compared between groups A1 and A2. RESULTS: In group A1*, ORR and median PFS with ICPi were 33 %, and 4.2 months (95 % CI, 2.4-8.1), respectively. With median follow-up since start of ICPi of 6.2 months [IQR 2.2-12.1] and 4.9 months [IQR 2.3-8.9] in groups A1* and B, respectively, 52 % and 64 % of patients died in groups A1* and B, respectively. Median OS with ICPi comprised 11.8 months (95 % CI, 3.7-NR) and 6.9 months (95 % CI, 5.5-8.1) in groups A1* and B, respectively (p-0.23). Median OSDx was 14.5 months (95 % CI, 10.1-38.9) and 10.3 months (95 % CI, 2.6-NR), in groups A1 and A2, respectively (p-0.54). CONCLUSION: In advanced LCNEC, ICPi outcomes are comparable to the outcomes observed in advanced NSCLC. Future research is needed to clarify the impact of ICPi on OS, and to correlate its benefit with tumor mutational landscape.