hMENA isoforms regulate cancer specific Type I IFN signaling and extrinsic mechanisms of resistance to immune checkpoint blockade

The actin cytoskeleton regulatory protein hMENA and its splicing-derived isoforms, hMENA11a and hMENAΔV6 participate to non-small-cell lung cancer (NSCLC) progression with low hMENA11a expression, along with high overall hMENA identifying early NSCLC patients with poor prognosis, as we have demonstrated. hMENA11a loss in tumor cells perturbs cell-cell junction integrity, pre-requisite for EMT and herein we identify a novel role for hMENA11a as regulator of genes related to IFN and inflammatory pathways. To identify mechanisms underlying the poor prognostic value of low hMENA11a expression, we depleted hMENA11a from NSCLC cells (si-11a) and analyzed their transcriptome and secretome. Along with the expected down-regulation of E-cadherin transcripts, we observed the up-regulation of several IFN signaling-related transcripts, including STAT1, PD-L1 and IFNβ. Furthermore we found an increase of IFNβ secretion in si11a cells. Focusing on PD-L1 up-regulation, we found that it relies on JAK/STAT1/IRF1 axis activation occurring in si-11a cells but not in cells depleted for total hMENA. Notably, ATAC-Seq analysis of si-11a cells revealed the existence of unknown regulatory regions in CD274 (PD-L1) locus. We also found the production of different inflammatory molecules, including CXCL1, IL6 and IL8 consistent with higher activation of NF-kB observed in si-11a cells. However, depletion of E-cadherin in our cell lines activates NF-kB but not STAT1 pathway, suggesting a specific role of hMENA11a. hMENA11a silencing, which induces a critical cytoskeleton remodeling, increases the expression of the actin cytoskeleton-linked viral sensor RIG-I which sustains STAT1 activation and PD-L1 and IFNβ up-regulation. Overall, we propose that hMENA11a loss activates Type I IFN and inflammatory pathways, and in turn PD-L1 expression, by activating the viral sensor RIG-I. Considering that Type I IFN pathway has recently reported as crucial in ICB resistance, we are conducting studies to evaluate the role of hMENA11a in response to ICB in NSCLC.