Abstract
Neuronal calcium sensor‐1 (NCS‐1) is a positive modulator of IP3 receptors and was recently associated with poorer survival in breast cancers. However, the association between NCS‐1 and breast cancer molecular subtypes and the effects of NCS‐1 silencing on calcium (Ca2+) signaling in breast cancer cells remain unexplored. Herein, we report for the first time an increased expression of NCS‐1 in breast cancers of the basal molecular subtype, a subtype associated with poor prognosis. Using MDA‐MB‐231 basal breast cancer cells expressing the GCaMP6m Ca2+ indicator, we showed that NCS‐1 silencing did not result in major changes in cytosolic free Ca2+ increases as a result of endoplasmic reticulum Ca2+ store mobilization. However, NCS‐1 silencing suppressed unstimulated basal Ca2+ influx. NCS‐1 silencing in MDA‐MB‐231 cells also promoted necrotic cell death induced by the chemotherapeutic drug doxorubicin (1 µm). The effect of NCS‐1 silencing on cell death was phenocopied by silencing of ORAI1, a Ca2+ store‐operated Ca2+ channel that maintains Ca2+ levels in the endoplasmic reticulum Ca2+ store and whose expression was significantly positively correlated with NCS‐1 in clinical breast cancer samples. This newly identified association between NCS‐1 and basal breast cancers, together with the identification of the role of NCS‐1 in the regulation of the effects of doxorubicin in MDA‐MB‐231 breast cancer cells, suggests that NCS‐1 and/or pathways regulated by NCS‐1 may be important in the treatment of basal breast cancers in women.
Highlights
Aberrations in calcium (Ca2+) signaling and associated regulatory proteins such as Ca2+ channels occur in a variety of cancers (Stewart et al, 2015)
Given that neuronal calcium sensor-1 (NCS-1) was recently reported to be associated with increased breast tumor aggression and poor prognosis (Moore et al, 2017), we explored if NCS-1 is associated with any of the breast cancer intrinsic molecular subtypes using The Cancer Genome Atlas (TCGA) breast cancer database (Cancer Genome Atlas, 2012)
We found that NCS-1 expression is significantly higher in the basal molecular subtype (Fig. 1B) compared to other breast cancer subtypes
Summary
Aberrations in calcium (Ca2+) signaling and associated regulatory proteins such as Ca2+ channels occur in a variety of cancers (Stewart et al, 2015). Cancer cells may remodel their intracellular Ca2+ signaling machinery to favor tumorigenic processes that enable continued survival and proliferation (Prevarskaya et al., 2014). Prostate cancers exhibit increased expression of Ca2+ channels such as transient receptor potential vanilloid 6 (TRPV6) (Fixemer et al, 2003). ORAI3 channels (Dubois et al, 2014) compared to normal prostate tissues. The remodeling of ORAI3 channel expression in cancer cells causes a shift in Ca2+ influx from a store-regulated mechanism normally used by healthy prostate cells toward a store-. Abbreviations Ca2+, calcium; ER, endoplasmic reticulum; IP3, inositol triphosphate; NCS-1, neuronal calcium sensor-1; TCGA, The Cancer Genome Atlas; TRPV6, transient receptor potential vanilloid 6.
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