TNFalpha-induced Mucin 4 Expression Elicits Trastuzumab Resistance in HER2-Positive Breast Cancer

DE MARTINO M; PROIETTI, CJ; ALLEMAND D; GERCOVICH FG; ELIZALDE, PV; MERCOGLIANO MF; RIVAS, MA; FRAHM I; ARES S; ROA JC; VENTURUTTI, L; INURRIGARRO G; GIL DEZA E; GUZMÁN P; SCHILLACI R

CLINICAL CANCER RESEARCH

AMER ASSOC CANCER RESEARCH

Año: 2017 vol. 23 p. 636 - 648

1078-0432

Purpose: Although trastuzumab administration improved the outcome of HER2-positive breast cancer patients, resistance events hampered its clinical benefits. We demonstrated that TNFα stimulation in vitro induces trastuzumab resistance in HER2-positive breast cancer cell lines. Here, we explored the mechanism of TNFα-induced trastuzumab resistance and the therapeutic strategies to overcome it.Experimental Design: Trastuzumab-sensitive breast cancer cells, genetically engineered to stably overexpress TNFα, and de novo trastuzumab-resistant tumors, were used to evaluate trastuzumab response and TNFɑ-blocking antibodies effectiveness respectively. Immunohistochemistry and antibody-dependent cellcytotoxicity(ADCC), together with siRNA strategy, were used to explore TNFαinfluence on the expression and function of its downstream target, mucin 4 (MUC4).The clinical relevance of MUC4 expression was studied in a cohort of 78 HER2-positive breast cancer patients treated with adjuvant trastuzumab.Results: TNFα overexpression turned trastuzumab-sensitive cells and tumors into resistant ones. Histopathological findings revealed mucin foci in TNFα-producing tumors. TNFα induced upregulation of MUC4 which reduced trastuzumab binding to its epitope and impaired ADCC. Silencing MUC4 enhanced trastuzumab binding, increased ADCC, and overcame trastuzumab and trastuzumab-emtansine antiproliferative effects in TNFα-overexpressing cells. Accordingly, administration of TNFα-blocking antibodies downregulated MUC4 and sensitized de novo trastuzumabresistant breast cancer cells and tumors to trastuzumab. In HER2-positive breast cancer samples, MUC4 expression was found to be an independent predictor of poordisease-free survival (P = 0.008).Conclusions: We identified TNFɑ-induced MUC4 expression as a novel trastuzumab resistance mechanism. We propose MUC4 expression as a predictive biomarker of trastuzumab efficacy and a guide to combination therapy of TNFα-blocking antibodies with trastuzumab.