Orai1 promotes tumor progression by enhancing cancer stemness via NFAT signaling in oral/oropharyngeal squamous cell carcinoma

Abstract

Emerging evidence indicates that Orai1, a key calcium channel for store-operated Ca2+ entry, is associated with human cancer. However, the underlying mechanism by which Orai1 regulates cancer progression remains unknown. Here we report that intracellular level of Orai1 is increased in a stepwise manner during oral/oropharyngeal carcinogenesis and highly expressed in cancer stem-like cell (CSC)-enriched populations of human oral/oropharyngeal squamous cell carcinoma (OSCC). Ectopic Orai1 expression converted non-tumorigenic immortalized oral epithelial cells to malignant cells that showed CSC properties, e.g., self-renewal capacity, increased ALDH1HIGH cell population, increased key stemness transcription factors, and enhanced mobility. Conversely, inhibition of Orai1 suppressed tumorigenicity and CSC phenotype of OSCC, indicating that Orai1 could be an important element for tumorigenicity and stemness of OSCC. Mechanistically, Orai1 activates its major downstream effector molecule, NFATc3. Knockdown of NFATc3 in the Orai1-overexpressing oral epithelial cells abrogates the effect of Orai1 on CSC phenotype. Moreover, antagonist of NFAT signaling also decreases CSC phenotype, implying the functional importance of Orai1/NFAT axis in OSCC CSC regulation. Our study identifies Orai1 as a novel molecular determinant for OSCC progression by enhancing cancer stemness, suggesting that inhibition of Orai1 signaling may offer an effective therapeutic modality against OSCC.

Cancer stem cells and oral cancer: insights into molecular mechanisms and therapeutic approaches

“…CSCs are able to improve themselves in the nonadherent tumor spheres cultivated in ultra-low binding plates for supporting un-differentiated development of self-renovating stem cells [59]. Researchers found that the sphere medium would be in a serum-free situation complemented with sufficient mitogens, including fundamental fibroblast development agent and epidermal growth factor (EGF) [60][61][62]. Plentifulness and growth kinetics of the tumor spheres represent self-renovation capacities in a certain cultivation of heterogeneous cancer cells, which indicates the contents of cancer stem cells.…”

“…They show greater volume of expression of pluripotent transcription agents such as Lin28, Nanog, KLF4, Oct4, and Sox2 in comparison to the respective adherent mono-layer cells [26,60,70,71]. Moreover, influential expression of CSC specific markers, including CD44 and ALDH1 is expressed by oral tumor sphere-forming cells [60,61,72]. These would be largely tumorigenic as inoculated into nude mice and retain the respective selfrenovation capacities for several generations [72].…”

“…Recently, authors proposed the significance of calcium signaling in modulating oral cancer stemness traits [60,[176][177][178]. Ca 2+ is one of the global second messengers regulating several physiological procedures, and disruption of its homeostasis would be observed during carcinogenesis, which results in the deregulation of the rapid growth of the cells, emigration, and apoptosis inhibition [179][180][181][182].…”

“…Researchers have widely examined Orai1 in immunology, because NFAT is a transcription agent with a vital role to activate, differentiate, and effector functions of T-cells [189]. Results indicated essential contribution of Orai1 to carcinogenesis [60,177,181,[190][191][192][193][194][195][196][197].…”

Regulation of circular RNA circNFATc3 in cancer cells alters proliferation, migration and oxidative phosphorylation

“…NFATc3 plays an important role in retaining stemness via. NFATC3/OCT4 signaling and its overexpression increase tumorigenesis in oral cancer [18]. Unlike its parental gene, circNFATc3 remains uncharacterized functionally in cancer.…”