Autocrine 17-β-Estradiol/Estrogen Receptor-α Loop Determines the Response to Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer

Purpose: The response to immune checkpoint inhibitors (ICI) often differs between genders in non-small cell lung cancer (NSCLC), but metanalyses results are controversial, and no clear mechanisms are defined. We aim at clarifying the molecular circuitries explaining the differential gender-related response to anti-PD-1/anti-PD-L1 agents in NSCLC.Experimental Design: We prospectively analyzed a cohort of patients with NSCLC treated with ICI as a first-line approach, and we identified the molecular mechanisms determining the differential efficacy of ICI in 29 NSCLC cell lines of both genders, recapitulating patients' phenotype. We validated new immunotherapy strategies in mice bearing NSCLC patient-derived xenografts and human reconstituted immune system (immune-PDXs).Results: In patients, we found that estrogen receptor alpha (ER alpha) was a predictive factor of response to pembrolizumab, stronger than gender and PD-L1 levels, and was directly correlated with PD-L1 expression, particularly in female patients. ER alpha transcriptionally upregulated CD274/PD-L1 gene, more in females than in males. This axis was activated by 17-beta-estradiol, autocrinely produced by intratumor aromatase, and by the EGFR-downstream effectors Akt and ERK1/2 that activated ER alpha. The efficacy of pembrolizumab in immune-PDXs was significantly improved by the aromatase inhibitor letrozole, which reduced PD-L1 and increased the percentage of antitumor CD8+T-lymphocytes, NK cells, and V gamma 9V delta 2 T-lymphocytes, producing durable control and even tumor regression after continuous administration, with maximal benefit in 17-beta-estradiol/ER alpha highfemale immune-xenografts.Conclusions: Our work unveils that 17-beta-estradiol/ER alpha status predicts the response to pembrolizumab in patients with NSCLC. Second, we propose aromatase inhibitors as new gender-tailored immune-adjuvants in NSCLC. See related commentary by Valencia et al., p. 3832Conclusions: Our work unveils that 17-beta-estradiol/ER alpha status predicts the response to pembrolizumab in patients with NSCLC. Second, we propose aromatase inhibitors as new gender-tailored immune-adjuvants in NSCLC. See related commentary by Valencia et al., p. 3832

Automated summary

This study aims to elucidate the molecular circuitries explaining the differential gender-related response to anti-PD-1/anti-PD-L1 agents in non-small cell lung cancer (NSCLC). The results revealed that estrogen receptor alpha (ER alpha) is a predictive factor of response to pembrolizumab, particularly in female patients. Additionally, aromatase inhibitors are proposed as new gender-tailored immune-adjuvants in NSCLC.