Mucin 4 expression is associated with metastasis in triple-negative breast cancer and can be tackled by soluble TNF blockade, improving immunotherapy outcome.

Purpose: Triple-negative breast cancer (TNBC) has the worst prognosis among breast cancers. Immunotherapy is a therapeutic option, but there is no biomarker to guide promising combination treatments. Mucin 4 (MUC4) favors metastasis in preclinical cancer models. This study evaluates the efficacy of soluble TNF (sTNF) neutralization to tackle MUC4 expression preventing metastasis in combination with immunotherapy, and the potential use of MUC4 as a prognostic and predictive biomarker in TNBC patients.

Experimental Design: To explore TNF modulation of MUC4 expression, a panel of TNBC cell lines was used. To assess the effect of sTNF blockade with a dominant negative molecule in combination with anti-PD-1 antibody on lung metastasis and overall survival (OS), 4T1 and LMM3 tumors were used. MUC4, PD-L1 and Ki-67 expression was evaluated by immunohistochemistry, and tumor infiltrating lymphocytes (TILs) were assessed by H&E staining, in a cohort of 49 early TNBC patients treated with chemotherapy.

Results: TNF neutralization reduces MUC4 expression in TNBC cell lines. Only the combination of sTNF blockade with anti-PD-1 antibody prevents metastasis and increases mice survival. In early TNBC patients MUC4 expression is inversely associated with TILs presence and PD-L1 and Ki-67 expression. Finally, MUC4 is associated with metastasis and is an independent biomarker of poor OS.

Conclusions: We proved the existence of a sTNF/MUC4 axis in TNBC that can be actionable by sTNF neutralization, preventing metastasis. We suggest that MUC4 is a suitable biomarker to guide immunotherapy in TNBC, together with the administration of sTNF blocking drugs to improve outcome.