Effect of Tumor Necrosis Factor Alpha-induced Mucin 4 on resistance to HER2-targeted therapies in breast cancer

DE MARTINO, M; MADERA, S; GERCOVICH, FG; BRUNI, S; CORDO RUSSO, RI; ARES, SL; SCHILLACI, R; MERCOGLIANO, MF; GIL DEZA, E; ELIZALDE, PV

Chicago, IL

Congreso; ASCO Annual Meeting; 2019

American Society of Clinical Oncology

Background: We have demonstrated that tumor necrosis factor alpha (TNFɑ) is a source of trastuzumab (Tz) resistance in HER2 positive breast cancer. TNFɑ upregulates mucin 4 (MUC4) expression, a transmembrane glycoprotein that shields Tz binding epitope on HER2 molecule, impairing its action. Here, we studied whether MUC4 is the leading cause of resistance to HER2-targeted therapies, Tz and lapatinib (L), induced by TNFɑ.Methods: We used the JIMT-1 cells that are HER2+ and de novo resistant to Tz and to L. MUC4 was targeted by a stable shRNA containing a tetracycline-inducible cassette (JIMT-1shMUC4). Cells were treated with 10 µg/ml INB03, a dominant negative protein that inhibits soluble TNFα, 10 µg/ml Tz or 1 µM L and cell proliferation was measured by cell count. Cell migration was evaluated by wound healing assay. In vivo studies were performed in nude mice bearing JIMT-1shMUC4 tumor and 10 mg/kg Tz, 10 mg/kg INB03, or the combination of both were administered i.p. twice a week with or without doxycycline administration in drinking water. Human IgG was used as a control.Results: JIMT-1 cell proliferation and migration was not affected by IgG, Tz, L or INB03. However, treatment with Tz + INB03 or L+ INB03 decreased proliferation by 50% and 36 % and cell migration by 50% and 45% respectively. Treatment with Tz or L inhibited JIMT-1shMUC4 cell proliferation when MUC4 was silenced. Addition of INB03 did not further improve the results. In vivo studies confirmed this observation since induction of shMUC4 by doxycycline in established JIMT-1shMUC4 tumors, Tz inhibited 90% tumor growth vs. IgG at day 20 of treatment (p=0.0004, n=6-8).Conclusions: These results highlight the participation of TNFɑ-induced MUC4 expression on Tz and L resistance and support the use of the combination of Tz or L with selective inhibitors of soluble TNFα in HER2+ breast cancer patients. Ongoing work will disclose the usefulness of MUC4 as biomarker of L resistance in a cohort of advanced breast cancer patients.