miR-143 or miR-145 overexpression increases cetuximab-mediated antibody-dependent cellular cytotoxicity in human colon cancer cells

// Sofia E. Gomes 1 , André E. S. Simões 1 , Diane M. Pereira 1 , Rui E. Castro 1 , Cecília M. P. Rodrigues 1 , Pedro M. Borralho 1 1 Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal Correspondence to: Cecília M P Rodrigues, e-mail: cmprodrigues@ff.ulisboa.pt Pedro M Borralho, e-mail: borralho@ff.ulisboa.pt Keywords: miR-143, miR-145, cetuximab, ADCC, granzyme B Received: July 16, 2015 Accepted: January 01, 2016 Published: January 25, 2016 ABSTRACT miR-143 and miR-145 are downregulated in colon cancer. Here, we tested the effect of restoring these miRNAs on sensitization to cetuximab in mutant KRAS (HCT116 and SW480) and wild-type KRAS (SW48) colon cancer cells. We evaluated cetuximab-mediated antibody-dependent cellular cytotoxicity (ADCC) and the modulation of signaling pathways involved in immune effector cell-mediated elimination of cancer cells. Stable miR-143 or miR-145 overexpression increased cell sensitivity to cetuximab, resulting in a significant increase of cetuximab-mediated ADCC independently of KRAS status. Importantly, HCT116 cells overexpressing these miRNAs triggered apoptosis in result of cetuximab-mediated ADCC, effected by peripheral blood mononuclear cells ( p < 0.01). This was associated with increased apoptosis and caspase-3/7 activity, and reduced Bcl-2 protein expression ( p < 0.01). In addition, caspase inhibition abrogated cetuximab-mediated ADCC in HCT116 cells overexpressing either miR-143 or miR-145 ( p < 0.01). Furthermore, Bcl-2 silencing led to high level of cetuximab-mediated ADCC, compared to control siRNA ( p < 0.05). Importantly, granzyme B inhibition, abrogated cetuximab-mediated ADCC, reducing caspase-3/7 activity ( p < 0.01). Collectively, our data suggests that re-introduction of miR-143 or miR-145 may provide a new approach for development of therapeutic strategies to re-sensitize colon cancer cells to cetuximab by stimulating cetuximab-dependent ADCC to induce cell death.