Dual modulation of MCL-1 and mTOR determines the response to sunitinib
Mohamed Elgendy, … , Giuseppe Renne, Saverio Minucci
Mohamed Elgendy, … , Giuseppe Renne, Saverio Minucci
Published November 28, 2016
Citation Information: J Clin Invest. 2017;127(1):153-168. https://doi.org/10.1172/JCI84386.
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Research Article Cell biology Oncology

Dual modulation of MCL-1 and mTOR determines the response to sunitinib

Abstract

Most patients who initially respond to treatment with the multi–tyrosine kinase inhibitor sunitinib eventually relapse. Therefore, developing a deeper understanding of the contribution of sunitinib’s numerous targets to the clinical response or to resistance is crucial. Here, we have shown that cancer cells respond to clinically relevant doses of sunitinib by enhancing the stability of the antiapoptotic protein MCL-1 and inducing mTORC1 signaling, thus evoking little cytotoxicity. Inhibition of MCL-1 or mTORC1 signaling sensitized cells to clinically relevant doses of sunitinib in vitro and was synergistic with sunitinib in impairing tumor growth in vivo, indicating that these responses are triggered as prosurvival mechanisms that enable cells to tolerate the cytotoxic effects of sunitinib. Furthermore, higher doses of sunitinib were cytotoxic, triggered a decline in MCL-1 levels, and inhibited mTORC1 signaling. Mechanistically, we determined that sunitinib modulates MCL-1 stability by affecting its proteasomal degradation. Dual modulation of MCL-1 stability at different dose ranges of sunitinib was due to differential effects on ERK and GSK3β activity, and the latter also accounted for dual modulation of mTORC1 activity. Finally, comparison of patient samples prior to and following sunitinib treatment suggested that increases in MCL-1 levels and mTORC1 activity correlate with resistance to sunitinib in patients.

Authors

Mohamed Elgendy, Amal Kamal Abdel-Aziz, Salvatore Lorenzo Renne, Viviana Bornaghi, Giuseppe Procopio, Maurizio Colecchia, Ravindran Kanesvaran, Chee Keong Toh, Daniela Bossi, Isabella Pallavicini, Jose Luis Perez-Gracia, Maria Dolores Lozano, Valeria Giandomenico, Ciro Mercurio, Luisa Lanfrancone, Nicola Fazio, Franco Nole, Bin Tean Teh, Giuseppe Renne, Saverio Minucci

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Figure 5

Sunitinib modulates proteasome-mediated degradation of MCL-1.

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Sunitinib modulates proteasome-mediated degradation of MCL-1. (A) MCL1 m...
(A) MCL1 mRNA levels assessed by real-time qPCR in HCT116 cells treated as indicated. Cells transfected with MCL1 expression vector or MCL-1 shRNA were used as control for the validation of real-time qPCR protocol. Results are representative of 3 independent experiments. Error bars represent SEM. KD, knockdown; OE, overexpression. (B and C) MCL-1 protein levels in HCT116 cells treated with either DMSO or 1.25 μM (B) or 10 μM (C) sunitinib in the absence or presence of cycloheximide (20μg/ml) at the indicated time points. (D and E) Quantification of the MCL-1 protein levels as assessed by the intensity of MCL-1 bands in cells treated as in B and C. Results are representative of 3 independent experiments. Error bars indicate SEM. (F) Endogenous MCL-1 was immunoprecipitated from HCT116 cells treated with either DMSO, 1.25 μM sunitinib, or 10 μM sunitinib. The ubiquitination status of the immunoprecipitated MCL-1 protein was assessed in each condition. (G and H) MCL-1 protein levels in HCT116 cells treated with either DMSO or 10 μM (G) or 1.25 μM (H) sunitinib in the absence or presence of MG132 (2.5 μM).