Lercanidipine Synergistically Enhances Bortezomib Cytotoxicity in Cancer Cells via Enhanced Endoplasmic Reticulum Stress and Mitochondrial Ca2+ Overload

Abstract

The proteasome inhibitor (PI), bortezomib (Btz), is effective in treating multiple myeloma and mantle cell lymphoma, but not solid tumors. In this study, we show for the first time that lercanidipine (Ler), an antihypertensive drug, enhances the cytotoxicity of various PIs, including Btz, carfilzomib, and ixazomib, in many solid tumor cell lines by inducing paraptosis, which is accompanied by severe vacuolation derived from the endoplasmic reticulum (ER) and mitochondria. We found that Ler potentiates Btz-mediated ER stress and ER dilation, possibly due to misfolded protein accumulation, in MDA-MB 435S cells. In addition, the combination of Btz and Ler triggers mitochondrial Ca2+ overload, critically contributing to mitochondrial dilation and subsequent paraptotic events, including mitochondrial membrane potential loss and ER dilation. Taken together, our results suggest that a combined regimen of PI and Ler may effectively kill cancer cells via structural and functional perturbations of the ER and mitochondria.

Intracellular Ca2 + Imbalance Critically Contributes to Paraptosis

“…During this process, they disrupt Ca 2+ homeostasis at the ER by altering Ca 2+ store content and Ca 2+ dynamics (including the uptake, release, and leakage of Ca 2+ ) and/or at the mitochondria by affecting the activities of MCU complex components to regulate the mitochondrial Ca 2+ levels. In addition, recent studies have shown that treatment of cancer cells with drugs that perturb Ca 2+ homeostasis [CGP-37157 ( Yoon et al, 2012 ), lercanidipine ( Lee et al, 2019 ), and loperamide ( Kim et al, 2019 )] or Nutlin-3, which is a chemical that triggers the mitochondrial unfolded protein response (mtUPR) ( Lee et al, 2017 ), induces paraptosis when combined with proteasome inhibitors (PIs). The proposed targets through which these paraptosis-inducing agents disrupt Ca 2+ homeostasis are summarized in Figure 1 .…”

“…A recent study showed that lercanidipine (Ler), a third-generation 1,4-dihydropyridine (DHP) used to treat high blood pressure, potentiates the antitumor effects of various PIs (e.g., Btz, carfilzomib, and ixazomib) in many solid cancer cell lines by inducing paraptosis, a cell death mode accompanied by extensive vacuolation derived from the ER and the mitochondria ( Lee et al, 2019 ). Ler enhances Btz-mediated ER stress and ER dilation in MDA-MB 435S cells.…”

“…As the possible underlying mechanism, the authors proposed that the Ler/Btz-mediated stabilization of DHP receptor and RyR may result in the release of Ca 2+ from the ER and the subsequent MCU-mediated mitochondrial Ca 2+ uptake. This sustained mitochondrial Ca 2+ overload may cause mitochondrial dilation and prompt opening of mPTP, leading to the leakage of Ca 2+ into the cytosol ( Lee et al, 2019 ).…”

“…On the other hand, massive Ca 2+ release from the ER causes the prolonged mitochondrial Ca 2+ overload and excessive mitochondrial swelling ( Rovere et al, 2016 ; Marchi et al, 2018 ). Mitochondrial Ca 2+ overload has been commonly reported in paraptosis-associated cell death by curcumin ( Yoon et al, 2012 ), celastrol ( Yoon et al, 2014 ), hesperidin ( Yumnam et al, 2016 ), morusin ( Xue et al, 2018 ), δ-TT ( Fontana et al, 2020a ), IPH4 ( Yokoi et al, 2020 ), Me 2 NNMe 2 ( Hager et al, 2018 ), CGP-37157/PI ( Yoon et al, 2012 ), Ler/PI ( Lee et al, 2019 ), Lop/PI ( Kim et al, 2019 ), and Nutlin-3/PI ( Lee et al, 2017 ). Among them, the functional significance of MCU-mediated mitochondrial Ca 2+ overload as an early signal for paraptosis was confirmed by the reports that pharmacological and/or genetic inhibition of MCU attenuates the mitochondrial dilation and subsequent paraptotic cascades (i.e., ER stress, ER dilation, and subsequent cell death) induced by curcumin ( Yoon et al, 2012 ), celastrol ( Yoon et al, 2014 ), hesperidin ( Yumnam et al, 2016 ), CGP-37157/PI ( Yoon et al, 2012 ), and Ler/PI ( Lee et al, 2019 ).…”

“…VDAC-mediated mitochondria Ca 2+ uptake was shown to be involved in morusin- or δ-TT-induced paraptotic cell death ( Xue et al, 2018 ; Fontana et al, 2020a ). The source of overloaded Ca 2+ in the mitochondria was the ER ( Yoon et al, 2012 , 2014 ; Lee et al, 2019 ); RyR is reportedly involved in the release of Ca 2+ from the ER in curcumin- or Ler/PI-induced paraptosis ( Yoon et al, 2012 ; Lee et al, 2019 ), whereas IP 3 R was involved in that process during celastrol-induced cell death ( Yoon et al, 2014 ). In addition, both RyR and IP 3 R were reported to mediate the release of Ca 2+ from the ER during hesperidin-induced paraptosis ( Yumnam et al, 2016 ).…”