ORAI1 and ORAI3 in Breast Cancer Molecular Subtypes and the Identification of ORAI3 as a Hypoxia Sensitive Gene and a Regulator of Hypoxia Responses

Abstract

The remodeling of specific calcium-permeable ion channels is a feature of some breast cancer subtypes. ORAI1 is a protein that forms a calcium-permeable ion channel responsible for store-operated calcium entry (SOCE) in a variety of cell types. ORAI3, a related isoform, is not a regulator of SOCE in most cell types. However, ORAI3 does control SOCE in many estrogen receptor-positive breast cancer cell lines, where it also controls proliferation. ORAI1 is a well-characterized regulator of the proliferation and migration of many basal breast cancer cells; however, the role of ORAI3 in these types of breast cancer cells remains unclear. Here, we sought to define ORAI1 and ORAI3 expression in breast cancer cell lines of different molecular subtypes and assess the potential role and regulation of ORAI3 in basal breast cancer cells. Our study demonstrates that elevated ORAI1 is a feature of basal-like breast cancers, while elevated ORAI3 is a feature of luminal breast cancers. Intriguingly, we found that ORAI3 is over-expressed in the mesenchymal subtype of triple-negative breast cancer. Given this, we assessed ORAI3 levels in the presence of two inducers of the mesenchymal phenotype, hypoxia and epidermal growth factor (EGF). Hypoxia induced ORAI3 levels in basal breast cancer cell lines through a pathway involving hypoxia-inducible factor-1 alpha (HIF1α. The silencing of ORAI3 attenuated hypoxia-associated phosphorylation of the EGF receptor (EGFR) and the expression of genes associated with cell migration and inflammatory/immune responses in the MDA-MB-468 model of basal breast cancer. Although elevated ORAI3 levels were not associated with survival; basal, estrogen receptor-negative and triple-negative breast cancers with high ORAI3 and low ORAI1 levels were associated with poorer clinical outcomes. This study defines ORAI3 as a potential fine-tuner for processes relevant to the progression of basal breast cancers.

Synthesis and Pharmacological Characterization of 2-Aminoethyl Diphenylborinate (2-APB) Derivatives for Inhibition of Store-Operated Calcium Entry (SOCE) in MDA-MB-231 Breast Cancer Cells

“…The disruption of SOCE has various pathophysiological implications such as muscle, immune, and neurodegenerative disorders as well as cancer [ 12 , 13 , 14 , 15 , 16 ]. Breast cancer metastasis has been linked to STIM1/Orai1-mediated Ca 2+ influx [ 17 ] and several studies also highlighted the upregulation of STIM1 and Orai1 in basal breast cancers [ 18 , 19 ]. Our understanding on the remodeling of SOCE in breast cancer cells has increased over the years and has recently been reviewed [ 20 ].…”

Adenylyl Cyclase Type 8 Overexpression Impairs Phosphorylation-Dependent Orai1 Inactivation and Promotes Migration in MDA-MB-231 Breast Cancer Cells

“…Consequently, this type of cancer is resistant to hormonal therapies and chemicals that target the HER2 receptor [1]. Studies in TNBC cells revealed that Ca 2+ signaling is remodeled and plays a key functional role [2][3][4][5]. TNBC cells overexpress Orai1, which is responsible for the activation of store-operated Ca 2+ entry (SOCE) [6].…”

The Calcium-Signaling Toolkit in Cancer: Remodeling and Targeting

“…In estrogen receptor-positive breast cancer cells, but not in estrogen receptor-negative breast cancer cells; however, ORAI3 expression levels are increased (Motiani et al 2010). Assessment of clinical samples shows higher levels of ORAI3 in luminal breast cancer subtypes compared with the basal molecular subtype, which overlap with estrogen receptor-positive and estrogen receptor-negative breast cancer subtypes, respectively (Azimi et al 2019). Unlike in most other cell types, and in contrast to the estrogen receptor-negative breast cancer cell lines tested, the overexpression of ORAI3 in estrogen receptorpositive breast cancer cells is associated with ORAI3 also contributing along with ORAI1 to SOCE (Motiani et al 2010).…”