Soluble TNF- induced mucin 4 is a mediator of trastuzumab resistance and of an immunosuppressive tumor microenvironment in HER2+ breast cancer

DE MARTINO M; ELIZALDE, PV; MAURO, F; SCHILLACI, R; BRUNI, S; SANTA MARIA DE LA PARRA, L

Congreso; 34th Annual Meeting & Pre-Conference Programs of the Society for Immunotherapy of Cancer; 2019

About 13-20% of breast cancer (BC) patients are HER2 positive (HER2+) and receive trastuzumab (T), an anti-HER2 monoclonal antibody, but 40-60% of them relapse. We have demonstrated that tumor necrosis factor alpha (TNFα) induces the expression of the transmembrane glycoprotein mucin 4 (MUC4), that shields T epitope in HER2, impairing its antitumor effects. Also, we have shown that Etanercept (E), an inhibitor of soluble and transmembrane TNFα (sTNFα, tmTNFα), downregulated MUC4 expression and sensitized de novo T-resistant BC xenografts to T (1). The aim of this work was to study the participation of MUC4 on T resistance in vivo, on T-mediated antitumor innate immune response, and to evaluate the role of sTNFα on MUC4 expression.We used the T-resistant JIMT-1 cell line transduced with a doxycycline (Dox)-inducible MUC4 shRNA construct (JIMT-shMUC4). To block TNFα, we used E or the dominant negative-TNFα protein INB03 (DN). Nude mice bearing JIMT-1-shMUC4 tumors (~50 mm3), were randomly assigned to the experimental (+Dox 2mg/ml in drinking water) or control group (−Dox). Both groups were treated with IgG, T, E (all 5 mg/kg), DN (10 mg/kg), T+E or T+DN i.p. twice a week and tumor volume was monitored routinely. MUC4 expression was determined by Western Blot in tumor extracts. Tumor-infiltrating immune cells were evaluated by immunofluorescence and analyzed by flow cytometry. In control groups, only T+E and T+DN administrations were able to inhibit tumor growth (72% and 75%, respectively, P