MUCIN 4 expression in high -risk breast cancer: predicting and overcoming resistance to immunotherapy

MAURO, FLORENCIA L.; PROIETTI, CECILIA JAZMÍN; DUPONT, AGUSTINA; BARCHUK, SABRINA; ARES, SANDRA; SCHILLACI, ROXANA; MERCOGLIANO, MARÍA FLORENCIA; CORDO RUSSO, ROSALÍA; ADAMI, CARLA; FIGURELLI, SILVINA; GERCOVICH, FELIPE G.; BRUNI, SOFIA; ROLDAN DEAMICIS, AGUSTINA; INURRIGARRO, GLORIA; LÓPEZ DELLA VECCHIA, DANIEL; GIL DEZA, ERNESTO; ELIZALDE, PATRICIA VIRGINIA

San Antonio

Simposio; San Antonio Breast Cancer Symposium; 2021

Background HER2-positive (+) and triple negative breast cancer (TNBC) have the worst s urvival among breast cancer subtypes. BC patients are treated with chemotherapy (CT) and/or radiotherapy (RT) , and HER2+ BC patients also receive targeted therapies, such as trastuzumab (Tz).. . The abundance of tumor infiltrating lymphocytes (TILs), in both HER2+ and TNBC, has a major good prognostic value. Thus, indicating that immunological evasion mechanisms may be present in the tumor microenvironment (TME) hampering the efficacy of Tz. We previously showed that soluble tumor necrosis factor alpha (sTNF) induces upregulation of mucin 4 (MUC4), which shields Tz epitope on HER2 impairing Tz binding and its therapeutic effects. In preclinical models of de novo Tz-resistant tumors, the combined administration of TNF-blocking agents etanercept or INB03 (DN) together with Tz inhibit tumor growth. We proved that MUC4 expression is an independent predictor of poor disease-free survival in patients treated with adjuvant Tz. Our goal is to study whether MUC4 plays a role in tumor immune evasion in HER2+ and TNBC.Methods Untreated primary BC samples were assessed for TILs density (% of occupied stromal area on H&E staining) and MUC4 expression by immunohistochemistry. Tumors with TILs ≥30% and >50%, for TNBC and HER2+ BC respectively, and MUC4 scores 2 and 3 (0-3) were deemed positive. A cohort of 56 TNBC and 90 HER2+BC, stage I-III were retrospectively retrieved from Hospital Fernández and Instituto Henry Moore from 2013 through 2017, and clinicopathological and treatment characteristics were obtained from electronic records. TNBC were treated with adjuvant (41) or neoadjuvant CT +/- RT (15). HER2+BC patients received adjuvant Tz plus CT. The association between MUC4 and overall survival (OS) was assessed using Cox proportional hazards model. The association between MUC4 and TILs was performed using Chi2. JIMT-1 HER2+ BC, de novo resistant tumors to Tz, containing a doxycycline (Dox)-inducible shRNA MUC4 plasmid (JIMT-1shMUC4) growing in nude mice were treated with IgG, Tz, the soluble TNF inhibitor DN or Tz + DN. Tumor growth was measured and macrophages and NK cells were determined in the TME by flow cytometry. Anti-asialo GM1 and clodronate-encapsulated liposomes were used to deplete NK cells and macrophages, respectively.ResultsWe found an inverse relation between TILs and MUC4 expression in HER2+ and TNBC (P=0.02 and P= 5 x10-5, respectively). Patients with MUC4+ TNBC have a shorter OS [P=0.05; HR 3.2 (95%CI 0.9-10.5)] and MUC4 was an independent predictor of OS [P=0.01; HR 4.9 (95%CI 1.4-17.0)]. To study MUC4 involvement on macrophage and NK recruitment in a Tz resistant model, nude mice bearing JIMT-1-shMUC4 tumors were treated or not with Dox to abolish MUC4 expression . Both groups received IgG, Tz, DN or DN + Tz. In Dox- groups, only Tz + DN administration was able to curb tumor growth (75% inhibition, P