NCX1 disturbs calcium homeostasis and promotes RANKL-induced osteoclast differentiation by regulating JNK/c-Fos/NFATc1 signaling pathway in multiple myeloma

Abstract

Although several types of calcium channels abnormalities have been shown to promote myeloma bone disease (MBD), the relationship between Na+/Ca2+ exchanger 1 (NCX1) and MBD remains unexplored. Here, we examined the role of NCX1 in the development of multiple myeloma (MM), with a special focus on the underlying effects involved osteoclast differentiation. Firstly, we detected NCX1 protein highly expressed in BM tissues of MM patients, and its expression was positively correlated with serum calcium and the percentage of BM CD138+ cells. In vitro, NCX1 suppression with the inhibitor KB-R7943 reduced cell viability of MM cells and caused apoptosis. Extracellular high Ca2+ environment increased the level of intracellular Ca2+ in MM cells through gating the calcium influx, with subsequently promoting the expression of NCX1 and osteoclastogenesis-related genes (receptor activator of nuclear factor-κB (RANKL), nuclear factor of activated T cell cytoplasmic 1 (NFATc1), and proto-oncogene Fos (c-Fos). This phenomenon could be reversed by KB-R7943 or calcium chelation. Furthermore, NCX1 overexpression in MM cells accelerated osteoclastogenesis, while NCX1 knockdown or suppression resulted in the opposite effect. Mechanistically, we further investigated the related mechanisms of NCX1 regulating osteoclast differentiation using RNA sequencing, western blotting and Enzyme linked immunosorbent assay, and found that NCX1 modulated osteoclast differentiation in MM though JNK/c-Fos/NFATc1 signaling pathway. In conclusion, the Ca2+/NCX1-mediated signaling participates in the osteoclasts-myeloma cell interactions, which represents a promising target for future therapeutic intervention in MBD.

NCX1/Ca2+ promotes autophagy and decreases bortezomib activity in multiple myeloma through non-canonical NFκB signaling pathway

“…It is well known that cellular calcium homeostasis and autophagy play important roles in BTZ sensitivity of MM cells [26,27]. Our previous work detected [Ca 2+ ] i by flow cytometry and showed that [Ca 2+ ] o activated NCX1, promoted extracellular calcium influx [21], which we further demonstrated using calcium ion imaging system (Additional 1). Here, we would like to further investigate the potential effects of high calcium microenvironment activating NCX1 on autophagy and BTZ sensitivity in MM cells.…”

“…Multiple signaling pathways have been described to be involved in autophagy in MM, such as NFκB [ 46 ], P38 [ 47 ], ERK and mTOR [ 48 ]. Our previous research results showed that NCX1 expression had no effect on ERK/pERK and P38/pP38 [ 21 ]. It has been reported that NFκB plays an important role in the survival of various B-cell tumors, especially MM [ 49 ], and NFκB is a key target of BTZ.…”

“…And NCX1 expression were positively correlated with serum calcium in MM. More importantly, NCX1 induced calcium influx of MM cells promoted RANKL-induced osteoclast differentiation [ 21 ]. Studies have confirmed that the BM microenvironment, especially BM osteoclasts, play a central role in supporting MM cell survival and drug resistance [ 22 , 23 ].…”