ICRAC controls the rapid androgen response in human primary prostate epithelial cells and is altered in prostate cancer

Abstract

Labelled 5α-dihydrotestosterone (DHT) binding experiments have shown that expression levels of (yet unidentified) membrane androgen receptors (mAR) are elevated in prostate cancer and correlate with a negative prognosis. However, activation of these receptors which mediate a rapid androgen response can counteract several cancer hallmark functions such as unlimited proliferation, enhanced migration, adhesion and invasion and the inability to induce apoptosis. Here, we investigate the downstream signaling pathways of mAR and identify rapid DHT induced activation of store-operated Ca2+ entry (SOCE) in primary cultures of human prostate epithelial cells (hPEC) from non-tumorous tissue. Consequently, down-regulation of Orai1, the main molecular component of Ca2+ release-activated Ca2+ (CRAC) channels results in an almost complete loss of DHT induced SOCE. We demonstrate that this DHT induced Ca2+ influx via Orai1 is important for rapid androgen triggered prostate specific antigen (PSA) release. We furthermore identified alterations of the molecular components of CRAC channels in prostate cancer. Three lines of evidence indicate that prostate cancer cells down-regulate expression of the Orai1 homolog Orai3: First, Orai3 mRNA expression levels are significantly reduced in tumorous tissue when compared to non-tumorous tissue from prostate cancer patients. Second, mRNA expression levels of Orai3 are decreased in prostate cancer cell lines LNCaP and DU145 when compared to hPEC from healthy tissue. Third, the pharmacological profile of CRAC channels in prostate cancer cell lines and hPEC differ and siRNA based knock-down experiments indicate changed Orai3 levels are underlying the altered pharmacological profile. The cancer-specific composition and pharmacology of CRAC channels identifies CRAC channels as putative targets in prostate cancer therapy.

STIM and Orai proteins as novel targets for cancer therapy. A Review in the Theme: Cell and Molecular Processes in Cancer Metastasis

“…Using mice xenograft models, Dubois and coworkers (25) showed that Orai3 plays a critical role in prostate cancer development in vivo. In stark contrast to this study, Holzmann et al (39) reported a decrease in Orai3 expression in prostate cancer samples compared with normal healthy tissues. Interestingly, these authors also proposed that in prostate cancer cells, Orai1 and Orai3 form heteromultimeric channels, which they referred to as altered calcium release-activated calcium current (I CRAC ) channels (39 (39).…”

“…In stark contrast to this study, Holzmann et al (39) reported a decrease in Orai3 expression in prostate cancer samples compared with normal healthy tissues. Interestingly, these authors also proposed that in prostate cancer cells, Orai1 and Orai3 form heteromultimeric channels, which they referred to as altered calcium release-activated calcium current (I CRAC ) channels (39 (39). Based on 2-APB pharmacology and molecular knockdown in LNCaP cells, the authors concluded that in normal prostate cells, Orai3 is the major contributor to I CRAC while the decrease in Orai3 expression in prostate cancer cells favors the formation of Orai1-Orai3 heteromultimeric channels (39).…”

“…Interestingly, these authors also proposed that in prostate cancer cells, Orai1 and Orai3 form heteromultimeric channels, which they referred to as altered calcium release-activated calcium current (I CRAC ) channels (39 (39). Based on 2-APB pharmacology and molecular knockdown in LNCaP cells, the authors concluded that in normal prostate cells, Orai3 is the major contributor to I CRAC while the decrease in Orai3 expression in prostate cancer cells favors the formation of Orai1-Orai3 heteromultimeric channels (39). Certainly, more studies from different groups are required for better understanding of specific Orai homolog contribution to prostate cancer.…”

A calcium optimum for cytotoxic T lymphocyte and natural killer cell cytotoxicity

“…Modified primer sequences are identical as previously published (Holzmann et al . ): Orai1_1_mod, sense: 5′ OMeC OMeG GCCUGAUCUUUAUCG d(UCU) OMeU OMeT OMeT 3′ Antisense: 3′ OmeG OmeC CGGACUAGAAAUAGCAGA d(A) 5′ Orai1_2_mod, sense: 5′ OMeC OMeA ACAUCGAGGCGGUGA d(GCA) OMeA OMeT OMeT 3′ Antisense: 3′ OMeG OMeT UGUAGCUCCGCCACUCGU d(U) 5′ Negative control siRNA_mod, sense: 5′ OMeA OMeA UUCUCCGAACGUGUC d(ACG) OmeU OmeT OMeT 3′ Antisense: 3′ OmeT OMeT AAGAGGCUUGCACAGUGC d(A) 5′ Control siRNA_mod, sense: 5′ OMeA OMeA AGGUAGUGUAAUCGC d(CUU) OMeG OMeT OMeT 3′ Antisense: 3′ OMeT OMeT UCCAUCACAUUAGCGGAA dC 5′ …”

Crosstalk between calcium and reactive oxygen species signaling in cancer

“…Holzmann et al . proposed that ROS-mediated inactivation of ORAI1 may also contribute to higher sensitivity of prostate cancer cells to ROS, due to dampening of SOCE dependent pro-proliferative Ca 2+ signaling [198, 230]. The authors proposed that this altered ORAI1/ORAI3 expression ratio could provide a therapeutic opportunity to target the pro-proliferative actions of SOCE by carefully tuning redox-mediated inactivation to only affect tumor cells [198].…”