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.
Highlights
Colon cancer is among the most frequent malignant diseases in Western industrialized countries, and one of the most common cancer types
Our results demonstrated that SW48-derived cells treated with lower concentrations of cetuximab, 1 and 10 μg/ml, display reduced cell index values compared to untreated cells, with this reduction being more pronounced in SW48-miR-143 and SW48-miR-145, compared to SW48-Empty cells (Figure S2A)
Considering the lack of involvement of Fas in mediating cell death effected by peripheral blood mononuclear cells (PBMCs) following cetuximab treatment, we evaluated if caspase-dependent apoptosis resulting from cetuximab-mediated antibody-dependent cellular cytotoxicity (ADCC) was dependent on granzyme B activity
Summary
Colon cancer is among the most frequent malignant diseases in Western industrialized countries, and one of the most common cancer types. Cetuximab is a partially humanized monoclonal antibody, raised against the epidermal growth factor receptor (EGFR), which abrogates. EGFR signaling by impairing receptor dimerization, promoting receptor internalization and degradation, and by activating antibody-dependent cellular cytotoxicity (ADCC) [3, 4]. The targeting of EGFR pathways has been quite successful, mutations in KRAS carry a negative response predictive value of 99%, making it an ideal predictive biomarker for EGFR targeted therapy [5]. This dramatically reduces the therapeutic options for advanced colorectal cancer harboring KRAS mutations
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