TNFα induces multiresistance to HER2-targeted therapies in HER2-positive breast cancer

MARÍA F. MERCOGLIANO, MARA DE MARTINO, SOFIA BRUNI, LEANDRO VENTURUTTI, MARTÍN RIVAS, MATÍAS AMASINO, CECILIA J. PROIETTI, PATRICIA V. ELIZALDE, ROXANA SCHILLACI

Congreso; AACR Annual Meeting 2017. April 1 - 5, 2017, Wahington, D.C., USA.; 2017

HER2 positive (HER2+) is a breast cancer (BC) subtype characterized byHER2 overexpression/amplification that affects nearly 15% of BC patients andcorrelates with poor prognosis. These patients receive trastuzumab (T), ananti-HER2 monoclonal antibody, but resistance events (40-60%) hamper itsclinical benefit. Previously we have demonstrated that TNFα (TNF) induced mucin 4 (MUC4) expression and turnedT-sensitive cell lines and tumors into resistant ones.Nowadays, new anti-HER2 therapies are being used in the clinicalsetting, such as lapatinib (a dual inhibitor of EGFR and HER2), and antibodieslike T-DM1 (combines TZ with the anti-microtubule agentemtansine), and pertuzumab (P) that impeds HER2 dimerization.The aim of this work was to study the role of TNF in resistance to the newHER2-targeted therapies.We used BT-474-C (control cells) and BT-474-T2, engineered in our lab tostably overexpress TNF, and were proven to be sensitive and resistant to T,respectively.We performed dose-response curves for T-DM1, they show that inhibitsproliferation of BT-474- C cells at 0.01 μg/ml. On the other hand, BT-474-T2 cells were resistant in the sameexperimental conditions and they exhibited reduced T-DM1 binding with respectto BT-474-C. BT-474-C cells were sensitive to low concentrations of T-DM1 with0.51 nmol/L, but in BT-474-T2 cells T-DM1 was ~10 times less potent thancontrol cells (IC 50 3.34 nmol/L). When we abrogated MUC4 expression, BT-474-T2cells were sensitized to T-DM1, showing that TNF-induced MUC4 expression isresponsible for T-DM1 resistance in this cell line.We assessed the effect of lapatinib performing a dose-response curve.Results shown a similar IC50 for BT-474 C and T2 cells (0.26 μM and 0.28 μM, respectively).When we studied P effect, we observed that the combination of T+P wasmore effective inhibiting proliferation in BT-474-C cells than T alone, despitethese results binding of the antibody showed no change between the cell lines.In BT-474-T2 cells proliferation was slightly inhibited by the combined treatment.In vivo experiments showed that BT-474-C tumors were sensitive to T and thecombination of T+P, but BT-474-T2 tumors did not respond to any of thesetreatments.These results suggest that TNF plays an important role inmultiresistance to HER2-targeted therapies, specifically T-DM1 and P, but notin lapatinib resistance. We propose TNF as an attractive target and we suggestthat HER2+ patients resistant to T could be eligible for a combination ofHER2-targeted therapies and a TNF-blocking treatment to overcome resistance.