Tumor Suppressor Mir-16 Mediates ErbB-2-Targeted Therapies Effects in Breast and Gastric Cancer

VENTURUTTI, LEANDRO; CORDO RUSSO, ROSALÍA; RIVAS, MARTÍN A.; MERCOGLIANO, MARÍA FLORENCIA; IZZO, FRANCO; DE MARTINO, MARA; OAKLEY, ROBERT H; YANKILEVICH, PATRICIO; ALLEMAND, DANIEL; CHARREAU, EDUARDO; CIDLOWSKI, JOHN; SCHILLACI, ROXANA; ELIZALDE, PATRICIA V.

Boston

Congreso; Endocrine Society´s 98th Annual Meeting and Expo; 2016

Endocrine Society

Overexpression of ErbB-2, a member of the ErbBs family of receptor tyrosine kinases, accounts for a clinically aggressive breast cancer (BC) subtype (ErbB-2 positive). Trastuzumab (TZ), an anti-ErbB-2 monoclonal antibody, is the most commonly used therapeutic option for ErbB-2-positive BC. However, many patients show de novo or acquired resistance. Lapatinib (L), a reversible inhibitor of ErbB-2 and EGFR tyrosine kinases, provides clinical benefit to a subset of patients progressing on TZ, but less than 25% achieve an objective response and the majority eventually develops L resistance. On the other hand, miRNAs (miRs) are short non-coding endogenous RNAs with regulatory functions and a key role in cancer. We previously reported that miR-16 is upregulated by TZ in TZ-sensitive, but not in resistant BC models. Our molecular mechanisms studies revealed that this is mediated by ErbB-2 downstream signaling pathways and the oncogene c-Myc, which inhibit miR-16 expression. We also disclosed a novel role for miR-16 as a tumor suppressor and showed that miR-16 overexpression could serve as an alternative therapeutic strategy for ErbB-2 positive BC. Lastly, we identified two novel miR-16 targets, CCNJ and FUBP1, whose downregulation underlies miR-16 anti-proliferative effects. Here, our first aim was to explore miR-16 role on L therapeutic effects in ErbB-2 positive BC. In line with our observations with TZ, we found that L induced miR-16 upregulation only in L sensitive cells, where L suppressed cell growth, inhibited ErbB-2 downstream signaling, c-Myc expression and miR-16 targets levels. In resistant cell lines, L was unable to alter the expression of c-Myc, miR-16 or its direct targets. Interestingly, L did enhance miR-16 levels in L-sensitive cells with intrinsic or acquired TZ resistance. MiR-16 overexpression inhibited proliferation of both L-sensitive and resistant BC cells, supporting its role as potent tumor suppressor. Our second aim was to extend our observations in BC to gastric cancer (GC), another cancer type with ErbB-2 overexpression, in which TZ is used in the metastatic setting. In line with our results in BC, we found that TZ induced miR-16 upregulation only in TZ-sensitive GC models. In these cells, TZ treatment inhibited the Phosphatidylinositol 3-phosphate and p42/p44 mitogen-activated kinases pathways, downregulated c-Myc, and reduced CCNJ and FUBP1 expression. On the contrary, TZ failed to alter signaling pathways activation or CCNJ and FUBP1 levels in resistant cells. Importantly, miR-16 forced expression successfully inhibited proliferation of both TZ-sensitive and -resistant ErbB-2 positive GC cells. Our results shed light on miR-16 role on the mechanisms of action and resistance to ErbB-2-targeted therapies in BC and GC, and provide a mechanistic insight into the benefit from L treatment seen in BC patients with TZ-refractory disease. - See more at: http://press.endocrine.org/doi/abs/10.1210/endo-meetings.2016.TB.7.SUN-099#sthash.3lg7LMeV.dpuf