Store-Operated Ca²⁺Entry Does Not Control Proliferation in Primary Cultures of Human Metastatic Renal Cellular Carcinoma

Abstract

Store-operated Ca2+ entry (SOCE) is activated following depletion of the inositol-1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pool to regulate proliferation in immortalized cell lines established from either primary or metastatic lesions. The molecular nature of SOCE may involve both Stim1, which senses Ca2+ levels within the endoplasmic reticulum (ER) Ca2+ reservoir, and a number of a Ca2+-permeable channels on the plasma membrane, including Orai1, Orai3, and members of the canonical transient receptor (TRPC1–7) family of ion channels. The present study was undertaken to assess whether SOCE is expressed and controls proliferation in primary cultures isolated from secondary lesions of heavily pretreated metastatic renal cell carcinoma (mRCC) patients. SOCE was induced following pharmacological depletion of the ER Ca2+ store, but not by InsP3-dependent Ca2+ release. Metastatic RCC cells express Stim1-2, Orai1–3, and TRPC1–7 transcripts and proteins. In these cells, SOCE was insensitive to BTP-2, 10 µM Gd3+ and Pyr6, while it was inhibited by 100 µM Gd3+, 2-APB, and carboxyamidotriazole (CAI). Neither Gd3+ nor 2-APB or CAI impaired mRCC cell proliferation. Consistently, no detectable Ca2+ signal was elicited by growth factor stimulation. Therefore, a functional SOCE is expressed but does not control proliferation of mRCC cells isolated from patients resistant to multikinase inhibitors.

Calcium signaling and cell proliferation

“…Knock-down of STIM1 expression resulting in almost complete inhibition of SOCE activity did not affect proliferation, as shown for HEK293 [21], endothelial cells [22] and differentiating myoblasts [94]. In metastatic renal carcinoma cells (mRCC), the pharmacological blockade of SOCE did not interfere with mRCC proliferation despite proper SOCE functioning in these cells [95]. In view that, store-independent Ca 2+ signaling triggers cell proliferation of some cell lines.…”

STIM and ORAI proteins: crucial roles in hallmarks of cancer

“…Moreover, Kim et al (50) reported an increase expression level of ORAI1, but not STIM1 or ORAI3, in RCC: pharmacological inhibition of SOCE or ORAI1 or STIM1 downregulation significantly impaired cell proliferation as well as cell migration of RCC Caki-1 cell lines. However, these data are a bit controversial and were not confirmed by Dragoni and colleagues (22), who could not find any role for SOCE in cell proliferation of freshly isolated RCC metastatic cells from patients.…”

“…In this research, the authors demonstrate the involvement of Orai1 in VEGF activated in vitro tubulogenesis and in vivo angiogenesis using the chick chorioallantoic membrane model (56). Similarly to HUVEC, suppression of ORAI1 in endothelial progenitor cells (EPCs) prevents VEGF-mediated SOCE and tubule formation (22,56). Moreover, EPCs isolated from RCC patients (RCC-EPCs) display an increased SOCE, which correlates with ORAI1, STIM1, and TRPC1 overexpression when compared with EPCs from healthy patients: genetic suppression of STIM1, ORAI1, and TRPC1 affects SOCE in RCC-EPCs (59).…”

Cavernous hemangioma of rhinopharynx: our experience and review of literature

“…Recently, their origin from late EPCs or differentiated endothelial cells was demonstrated [13]. EPCs are mobilized either from the bone marrow or the arterial area to replace dysfunctional endothelial cells and, using different molecular mechanisms, play a pivotal role in blood perfusion of ischemic and tumoral tissues [14–27]. Although haemangiomas are common lesions of the head and neck (over half of all hemangiomas are located in this region), in the nasal cavity and paranasal sinuses they are rare [1,3,5].…”