The apoptosis of non-small cell lung cancer induced by cisplatin through modulation of STIM1. ACTA ACUST UNITED AC. 2013;65:1073-1081. [PMID: 23714431 DOI: 10.1016/j.etp.2013.04.003]

Dysregulation of calcium homeostasis in cancer and its role in chemoresistance

Globally, cancer, as a major public health concern, poses a severe threat to people's well-being. Advanced and specialized therapies can now cure the majority of people with early-stage cancer. However, emerging resistance to traditional and novel chemotherapeutic drugs remains a serious issue in clinical medicine. Chemoresistance often leads to cancer recurrence, metastasis, and increased mortality, accounting for 90% of chemotherapy failures. Thus, it is important to understand the molecular mechanisms of chemoresistance and find novel therapeutic approaches for cancer treatment. Among the several factors responsible for chemoresistance, calcium (Ca2+) dysregulation plays a significant role in cancer progression and chemoresistance. Therefore, targeting this derailed Ca2+ signalling for cancer therapy has become an emerging research area. Of note, the Ca2+ signal and its proteins are a multifaceted and potent tool by which cells achieve specific outcomes. Depending on cell survival needs, Ca2+ is either upregulated or downregulated in both chemosensitive and chemoresistant cancer cells. Consequently, the appropriate treatment should be selected based on Ca2+ signalling dysregulation. This review discusses the role of Ca2+ in cancer cells and the targeting of Ca2+ channels, pumps, and exchangers. Furthermore, we have emphasised the role of Ca2+ in chemoresistance and therapeutic strategies. In conclusion, targeting Ca2+ signalling is a multifaceted process. Methods such as site-specific drug delivery, target-based drug-designing, and targeting two or more Ca2+ proteins simultaneously may be explored; however, further clinical studies are essential to validate Ca2+ blockers' anti-cancer efficacy.

Blockade of store-operated calcium entry sensitizes breast cancer cells to cisplatin therapy via modulating inflammatory response

Store-operated calcium entry (SOCE) is an important pathway for calcium signaling that regulates calcium influx across the plasma membrane upon the depletion of calcium stores in the endoplasmic reticulum. SOCE participates in regulating a number of physiological processes including cell proliferation and migration while SOCE dysregulation has been linked with pathophysiological conditions such as inflammation and cancer. The crosslink between cancer and inflammation has been well-established where abundant evidence demonstrate that inflammation plays a role in cancer pathophysiology and the response of cancer cells to chemotherapeutic agents including cisplatin. Indeed, the efficacy of cisplatin against cancer cells is reduced by inflammation. Interestingly, it was shown that SOCE enhances inflammatory signaling in immune cells. Therefore, the main objectives of this study are to examine the impact of SOCE inhibition on the cisplatin sensitivity of breast cancer cells and to explore its related mechanism in modulating the inflammatory response in breast cancer cells. Our findings showed that SOCE inhibitor (BTP2) enhanced cisplatin cytotoxicity against resistant breast cancer cells via inhibition of cell proliferation and migration as well as induction of apoptosis. We also found an upregulation in the gene expression of two major components of SOCE, STIM1 and ORAI1, in cisplatin-resistant breast cancer cells compared to cisplatin-sensitive breast cancer cells. In addition, cisplatin treatment increased the gene expression of STIM1 and ORAI1 in cisplatin-resistant breast cancer cells. Finally, this study also demonstrated that cisplatin therapy caused an increase in the gene expression of inflammatory mediators COX2, IL-8, and TNF-α as well as COX2 protein and upon SOCE inhibition using BTP2, the effect of cisplatin on the inflammatory mediators was reversed. Altogether, this study has proven the pivotal role of SOCE in cisplatin resistance of breast cancer cells and showed the importance of targeting this pathway in improving breast cancer therapy.

CRAC and SK Channels: Their Molecular Mechanisms Associated with Cancer Cell Development

Cancer represents a major health burden worldwide. Several molecular targets have been discovered alongside treatments with positive clinical outcomes. However, the reoccurrence of cancer due to therapy resistance remains the primary cause of mortality. Endeavors in pinpointing new markers as molecular targets in cancer therapy are highly desired. The significance of the co-regulation of Ca²⁺-permeating and Ca²⁺-regulated ion channels in cancer cell development, proliferation, and migration make them promising molecular targets in cancer therapy. In particular, the co-regulation of the Orai1 and SK3 channels has been well-studied in breast and colon cancer cells, where it finally leads to an invasion-metastasis cascade. Nevertheless, many questions remain unanswered, such as which key molecular components determine and regulate their interplay. To provide a solid foundation for a better understanding of this ion channel co-regulation in cancer, we first shed light on the physiological role of Ca²⁺ and how this ion is linked to carcinogenesis. Then, we highlight the structure/function relationship of Orai1 and SK3, both individually and in concert, their role in the development of different types of cancer, and aspects that are not yet known in this context.

The distinguishing electrical properties of cancer cells

In recent decades, medical research has been primarily focused on the inherited aspect of cancers, despite the reality that only 5-10% of tumours discovered are derived from genetic causes. Cancer is a broad term, and therefore it is inaccurate to address it as a purely genetic disease. Understanding cancer cells' behaviour is the first step in countering them. Behind the scenes, there is a complicated network of environmental factors, DNA errors, metabolic shifts, and electrostatic alterations that build over time and lead to the illness's development. This latter aspect has been analyzed in previous studies, but how the different electrical changes integrate and affect each other is rarely examined. Every cell in the human body possesses electrical properties that are essential for proper behaviour both within and outside of the cell itself. It is not yet clear whether these changes correlate with cell mutation in cancer cells, or only with their subsequent development. Either way, these aspects merit further investigation, especially with regards to their causes and consequences. Trying to block changes at various levels of occurrence or assisting in their prevention could be the key to stopping cells from becoming cancerous. Therefore, a comprehensive understanding of the current knowledge regarding the electrical landscape of cells is much needed. We review four essential electrical characteristics of cells, providing a deep understanding of the electrostatic changes in cancer cells compared to their normal counterparts. In particular, we provide an overview of intracellular and extracellular pH modifications, differences in ionic concentrations in the cytoplasm, transmembrane potential variations, and changes within mitochondria. New therapies targeting or exploiting the electrical properties of cells are developed and tested every year, such as pH-dependent carriers and tumour-treating fields. A brief section regarding the state-of-the-art of these therapies can be found at the end of this review. Finally, we highlight how these alterations integrate and potentially yield indications of cells' malignancy or metastatic index.

Targeting ion channels for the treatment of lung cancer

Lung cancer is caused by several environmental and genetic variables and is globally associated with elevated morbidity and mortality. Among these variables, membrane-bound ion channels have a key role in regulating multiple signaling pathways in tumor cells and dysregulation of ion channel expression and function is closely related to proliferation, migration, and metastasis of lung cancer. This work reviews and summarizes current knowledge about the role of ion channels in lung cancer, focusing on the changes in the expression and function of various ion channels in lung cancer and how these changes affect lung cancer cell biology both in vitro and in vivo as evidenced by both genetic and pharmacological studies. It can help understand the molecular mechanisms of various ion channels influencing the initiation and progression of lung cancer and shed new insights into their roles in the development and treatment of this deadly disease.

Cardiomyocyte Stim1 Deficiency Exacerbates Doxorubicin Cardiotoxicity by Magnification of Endoplasmic Reticulum Stress

INTRODUCTION

Doxorubicin (Dox) is an effective anticancer agent; however, its cardiotoxicity remains a challenge. Dysfunction of intracellular calcium ion (Ca2+) is implicated in the process of Dox-induced cardiomyocyte apoptosis. Although store-operated Ca2+ entry (SOCE) is suggested to be responsible for Ca2+ entry in cardiomyocytes, the direct role of store-operated Ca2+ channels in Dox-related cardiomyocyte apoptosis is unknown.

MATERIALS AND METHODS

Cardiomyocyte Stim1-specific knockout or overexpression mice were treated with Dox. Cardiomyocytes were pretreated with Stim1 adenovirus or siRNA followed by Dox incubation in vitro. Cardiac function and underlying mechanisms echocardiography were assessed via immunofluorescence, flow cytometry, real-time PCR, Western blotting and immunoprecipitation.

RESULTS

We observed the inhibition of Stim1 expression, association of Stim1 to Orai1 or Trpc1, and SOCE in Dox-treated mouse myocardium and cardiomyocytes. Orai1 and Trpc1 expression remained unchanged. Cardiomyocyte-specific deficiency of Stim1 exacerbated Dox-induced cardiac dysfunction and myocardial apoptosis. However, specific overexpression of Stim1 in the myocardium was associated with amelioration of cardiac dysfunction and myocardial apoptosis. In vitro, STIM1 knockdown potentiated Dox-induced AC16 human cardiomyocyte apoptosis. This apoptosis was attenuated by STIM1 upregulation. Moreover, STIM1 downregulation enhanced Dox-induced endoplasmic reticulum (ER) stress in cardiomyocytes. In contrast, STIM1 overexpression inhibited the activation of the above molecular markers of ER stress. Immunoprecipitation assay showed that STIM1 interacted with GRP78 in cardiomyocytes. This interaction was attenuated in response to Dox treatment.

CONCLUSION

Our data demonstrate that cardiomyocyte STIM1 binding to GRP78 ameliorates Dox cardiotoxicity by inhibiting pro-apoptotic ER stress.

Cross-Talk Between the Adenylyl Cyclase/cAMP Pathway and Ca2+ Homeostasis

Cyclic AMP and Ca²⁺ are the first second or intracellular messengers identified, unveiling the cellular mechanisms activated by a plethora of extracellular signals, including hormones. Cyclic AMP generation is catalyzed by adenylyl cyclases (ACs), which convert ATP into cAMP and pyrophosphate. By the way, Ca²⁺, as energy, can neither be created nor be destroyed; Ca²⁺ can only be transported, from one compartment to another, or chelated by a variety of Ca²⁺-binding molecules. The fine regulation of cytosolic concentrations of cAMP and free Ca²⁺ is crucial in cell function and there is an intimate cross-talk between both messengers to fine-tune the cellular responses. Cancer is a multifactorial disease resulting from a combination of genetic and environmental factors. Frequent cases of cAMP and/or Ca²⁺ homeostasis remodeling have been described in cancer cells. In those tumoral cells, cAMP and Ca²⁺ signaling plays a crucial role in the development of hallmarks of cancer, including enhanced proliferation and migration, invasion, apoptosis resistance, or angiogenesis. This review summarizes the cross-talk between the ACs/cAMP and Ca²⁺ intracellular pathways with special attention to the functional and reciprocal regulation between Orai1 and AC8 in normal and cancer cells.

Orai3-Mediates Cisplatin-Resistance in Non-Small Cell Lung Cancer Cells by Enriching Cancer Stem Cell Population through PI3K/AKT Pathway

Simple Summary

Lung cancer is recognized for having a very poor prognosis with an overall survival rate of 5-years not exceeding 15%. Platinum-doublet therapy is the most current chemotherapeutic treatment used to treat lung tumors. However, resistance to such drugs evolves rapidly in patients with non-small cell lung cancer (NSCLC) and is one of the major reasons behind therapy failure. Tumor recurrence due to chemoresistance is mainly attributed to the presence of cancer stem cells (CSCs) subpopulations. Thus, the identification of resistance actors and markers is necessary. The Orai3 channel has been recently identified as a predictive marker of metastasis and survival in resectable NSCLC tumors. Our results show, for the first time, that the Orai3 channel is able to induce chemoresistance by enriching CSCs population. Our findings present Orai3 as a promising predictive biomarker which could help with selecting chemotherapeutic drugs.

Abstract

The development of the resistance to platinum salts is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Among the reasons underlying this resistance is the enrichment of cancer stem cells (CSCs) populations. Several studies have reported the involvement of calcium channels in chemoresistance. The Orai3 channel is overexpressed and constitutes a predictive marker of metastasis in NSCLC tumors. Here, we investigated its role in CSCs populations induced by Cisplatin (CDDP) in two NSCLC cell lines. We found that CDDP treatment increased Orai3 expression, but not Orai1 or STIM1 expression, as well as an enhancement of CSCs markers. Moreover, Orai3 silencing or the reduction of extracellular calcium concentration sensitized the cells to CDDP and led to a reduction in the expression of Nanog and SOX-2. Orai3 contributed to SOCE (Store-operated Calcium entry) in both CDDP-treated and CD133⁺ subpopulation cells that overexpress Nanog and SOX-2. Interestingly, the ectopic overexpression of Orai3, in the two NSCLC cell lines, lead to an increase of SOCE and expression of CSCs markers. Furthermore, CD133⁺ cells were unable to overexpress neither Nanog nor SOX-2 when incubated with PI3K inhibitor. Finally, Orai3 silencing reduced Akt phosphorylation. Our work reveals a link between Orai3, CSCs and resistance to CDDP in NSCLC cells.

Molecular Choreography and Structure of Ca2+ Release-Activated Ca2+ (CRAC) and KCa2+ Channels and Their Relevance in Disease with Special Focus on Cancer

Ca2+ ions play a variety of roles in the human body as well as within a single cell. Cellular Ca2+ signal transduction processes are governed by Ca2+ sensing and Ca2+ transporting proteins. In this review, we discuss the Ca2+ and the Ca2+-sensing ion channels with particular focus on the structure-function relationship of the Ca2+ release-activated Ca2+ (CRAC) ion channel, the Ca2+-activated K+ (KCa2+) ion channels, and their modulation via other cellular components. Moreover, we highlight their roles in healthy signaling processes as well as in disease with a special focus on cancer. As KCa2+ channels are activated via elevations of intracellular Ca2+ levels, we summarize the current knowledge on the action mechanisms of the interplay of CRAC and KCa2+ ion channels and their role in cancer cell development.

Serum and Glucocorticoid-Inducible Kinase 1 (SGK1) in NSCLC Therapy

Non-small cell lung cancer (NSCLC) remains the most prevalent and one of the deadliest cancers worldwide. Despite recent success, there is still an urgent need for new therapeutic strategies. It is also becoming increasingly evident that combinatorial approaches are more effective than single modality treatments. This review proposes that the serum and glucocorticoid-inducible kinase 1 (SGK1) may represent an attractive target for therapy of NSCLC. Although ubiquitously expressed, SGK1 deletion in mice causes only mild defects of ion physiology. The frequent overexpression of SGK1 in tumors is likely stress-induced and provides a therapeutic window to spare normal tissues. SGK1 appears to promote oncogenic signaling aimed at preserving the survival and fitness of cancer cells. Most importantly, recent investigations have revealed the ability of SGK1 to skew immune-cell differentiation toward pro-tumorigenic phenotypes. Future studies are needed to fully evaluate the potential of SGK1 as a therapeutic target in combinatorial treatments of NSCLC. However, based on what is currently known, SGK1 inactivation can result in anti-oncogenic effects both on tumor cells and on the immune microenvironment. A first generation of small molecules to inactivate SGK1 has already been already produced.

[Pt(O,O'-acac)(γ-acac)(DMS)]: Alternative Strategies to Overcome Cisplatin-Induced Side Effects and Resistance in T98G Glioma Cells

Cisplatin (CDDP) is one of the most effective chemotherapeutic agents, used for the treatment of diverse tumors, including neuroblastoma and glioblastoma. CDDP induces cell death through different apoptotic pathways. Despite its clinical benefits, CDDP causes several side effects and drug resistance.[Pt(O,O'-acac)(γ-acac)(DMS)], namely PtAcacDMS, a new platinum(II) complex containing two acetylacetonate (acac) and a dimethylsulphide (DMS) in the coordination sphere of metal, has been recently synthesized and showed 100 times higher cytotoxicity than CDDP. Additionally, PtAcacDMS was associated to a decreased neurotoxicity in developing rat central nervous system, also displaying great antitumor and antiangiogenic activity both in vivo and in vitro. Thus, based on the knowledge that several chemotherapeutics induce cancer cell death through an aberrant increase in [Ca²⁺]_i, in the present in vitro study we compared CDDP and PtAcacDMS effects on apoptosis and intracellular Ca²⁺ dynamics in human glioblastoma T98G cells, applying a battery of complementary techniques, i.e., flow cytometry, immunocytochemistry, electron microscopy, Western blotting, qRT-PCR, and epifluorescent Ca²⁺ imaging. The results confirmed that (i) platinum compounds may induce cell death through an aberrant increase in [Ca²⁺]_i and (ii) PtAcacDMS exerted stronger cytotoxic effect than CDDP, associated to a larger increase in resting [Ca²⁺]_i. These findings corroborate the use of PtAcacDMS as a promising approach to improve Pt-based chemotherapy against gliomas, either by inducing a chemosensitization or reducing chemoresistance in cell lineages resilient to CDDP treatment.

Knockdown of STIM1 expression inhibits non-small-cell lung cancer cell proliferation in vitro and in nude mouse xenografts

Stromal interaction molecule 1 (STIM1) is a calcium-sensing protein localized in the membrane of the endoplasmic reticulum. The expression of STIM1 has been shown to be closely associated with cell proliferation. The aim of the present study was to investigate the role of STIM1 in the regulation of cancer progression and its clinical relevance. The data demonstrated that the expression of the STIM1 was significantly higher in non-small-cell lung cancer (NSCLC) tissues than in benign lesions and was associated with advanced NSCLC T stage. Knockdown of STIM1 expression in NSCLC cell lines A549 and SK-MES-1 significantly inhibited cell proliferation and induces A549 and SK-MES-1 cell arrest at the G2/M and S phases of the cell cycle. Western blotting showed that the expression of cyclin-dependent kinase (CDK) 1 and CDK2 were reduced while knockdown of STIM1 expression. Furthermore, knockdown of STIM1 in NSCLC cells significantly reduced the levels of xenograft tumor growth in nude mice. These data indicate that aberrant expression of the STIM1 protein may contribute to NSCLC progression. Future studies should focus on targeting STIM1 as a novel strategy for NSCLC therapy.

Roles of CRAC channel in cancer: implications for therapeutic development

Introduction

The Ca2+release-activated Ca2+ (CRAC) channel, composed of Orai and STIM proteins, represents one of the main routes of Ca²⁺ entry in most non-excitable cells. There is accumulating evidence to suggest that CRAC channel can influence various processes associated with tumorigenesis. Overexpression of CRAC channel proteins has been observed in several types of cancer tissues and cells, indicating that blocking CRAC channel activated Ca²⁺ influx can have therapeutic benefits for cancer patients.

Areas covered

In this review, we have primarily focused on the molecular composition and activation mechanism of CRAC channel as well as the myriad roles this Ca²⁺ channel play in various cancers. We further describe relevant information about several efforts aimed at developing CRAC channel blockers and their likely implications for cancer therapy. We have extensively utilized the available literature on PubMed to this end.

Expert opinion

The possibility of targeting CRAC channel mediated Ca²⁺ entry in cancer cells has generated considerable interest in recent years. Use of CRAC channel blockers in cancer preclinical studies and clinical trials has been relatively limited as compared to other diseases. The future lies in developing and testing more potent and selective drugs that target cancer cell specific CRAC channel proteins, hence opening better avenues for cancer therapeutic development.

Store-Operated Ca2+ Entry in Tumor Progression: From Molecular Mechanisms to Clinical Implications

The remodeling of Ca²⁺ homeostasis has been implicated as a critical event in driving malignant phenotypes, such as tumor cell proliferation, motility, and metastasis. Store-operated Ca²⁺ entry (SOCE) that is elicited by the depletion of the endoplasmic reticulum (ER) Ca²⁺ stores constitutes the major Ca²⁺ influx pathways in most nonexcitable cells. Functional coupling between the plasma membrane Orai channels and ER Ca²⁺-sensing STIM proteins regulates SOCE activation. Previous studies in the human breast, cervical, and other cancer types have shown the functional significance of STIM/Orai-dependent Ca²⁺ signals in cancer development and progression. This article reviews the information on the regulatory mechanisms of STIM- and Orai-dependent SOCE pathways in the malignant characteristics of cancer, such as proliferation, resistance, migration, invasion, and metastasis. The recent investigations focusing on the emerging importance of SOCE in the cells of the tumor microenvironment, such as tumor angiogenesis and antitumor immunity, are also reviewed. The clinical implications as cancer therapeutics are discussed.

STIM-Orai Channels and Reactive Oxygen Species in the Tumor Microenvironment

The tumor microenvironment (TME) is shaped by cancer and noncancerous cells, the extracellular matrix, soluble factors, and blood vessels. Interactions between the cells, matrix, soluble factors, and blood vessels generate this complex heterogeneous microenvironment. The TME may be metabolically beneficial or unbeneficial for tumor growth, it may favor or not favor a productive immune response against tumor cells, or it may even favor conditions suited to hijacking the immune system for benefitting tumor growth. Soluble factors relevant for TME include oxygen, reactive oxygen species (ROS), ATP, Ca2+, H⁺, growth factors, or cytokines. Ca2+ plays a prominent role in the TME because its concentration is directly linked to cancer cell proliferation, apoptosis, or migration but also to immune cell function. Stromal-interaction molecules (STIM)-activated Orai channels are major Ca2+ entry channels in cancer cells and immune cells, they are upregulated in many tumors, and they are strongly regulated by ROS. Thus, STIM and Orai are interesting candidates to regulate cancer cell fate in the TME. In this review, we summarize the current knowledge about the function of ROS and STIM/Orai in cancer cells; discuss their interdependencies; and propose new hypotheses how TME, ROS, and Orai channels influence each other.

Store-Operated Calcium Entry Contributes to Cisplatin-Induced Cell Death in Non-Small Cell Lung Carcinoma

Cisplatin (CDDP) is one of the principal chemotherapeutic agents used for the first-line treatment of many malignancies, including non-small cell lung carcinoma (NSCLC). Despite its use for over 40 years, its mechanism of action is not yet fully understood. Store-operated calcium entry (SOCE), the main pathway allowing Ca²⁺ entry in non-excitable cells, is involved in tumorogenesis, cancer progression and chemoresistance. It has become an attractive target in cancer treatment. In this study, we showed that siRNA-mediated depletion of stromal interaction molecule 1 (STIM1) and transient receptor potential channel 1 (TRPC1), two players of the store-operated calcium entry, dramatically reduced CDDP cytotoxicity in NSCLC cells. This was associated with an inhibition of the DNA damage response (DDR) triggered by CDDP. Moreover, STIM1 depletion also reduced CDDP-dependent oxidative stress. In parallel, SOCE activation induced Ca²⁺ entry into the mitochondria, a major source of reactive oxygen species (ROS) within the cell. This effect was highly decreased in STIM1-depleted cells. We then conclude that mitochondrial Ca²⁺ peak associated to the SOCE contributes to CDDP-induced ROS production, DDR and subsequent apoptosis. To the best of our knowledge, this is the first time that it is shown that Ca²⁺ signalling constitutes an initial step in CDDP-induced apoptosis.

Silencing Heat Shock Protein 27 Inhibits the Progression and Metastasis of Colorectal Cancer (CRC) by Maintaining the Stability of Stromal Interaction Molecule 1 (STIM1) Proteins

The incidence of colorectal cancer (CRC) has significantly increased in recent decades, and this disease has become an important health issue worldwide. Currently, there is no useful prognostic or diagnostic biomarker for CRC. Heat shock protein 27 (HSP27) is a chaperone that interacts with many proteins. HSP27 has been shown to be overexpressed in many cancers, including colon cancer, and its overexpression is related to poor disease outcome. Although the importance of HSP27 as a biomarker cannot be underrated, its detailed mechanisms in colon cancer are still unclear. In vitro studies have indicated that silencing HSP27 reduces the proliferation, migration and invasion of colon cancer cells, and xenograft models have shown that silencing HSP27 decreases tumor progression. Tissue array results showed that colon cancer patients with high expression of HSP27 exhibited poor prognosis. In addition, we found a reduction of calcium influx through a decrease in STIM1 protein after HSP27 was abolished. The formation of puncta was decreased in HSP27 knockdown (HSP27KD) cells after thapsigargin (TG) treatment. Finally, we confirmed that the reduction of STIM1 after HSP27 silencing may be due to a loss of STIM1 stability instead of transcription. HSP27 may interact with STIM1 but not Orai1, as shown by immunoprecipitation assays. HSP27 and STIM1 were co-expressed in CRC specimens. Our study showed that HSP27 is a key mediator in the progression and metastasis of CRC by regulating the store-operated calcium entry. This novel pathway may provide a new direction for development of therapeutic strategies for CRC.

Knockdown of stromal interaction molecule 1 inhibits proliferation of colorectal cancer cells by inducing apoptosis

Stromal interaction molecule 1 (STIM1) is an endoplasmic reticulum Ca²⁺ sensor which has been reported to be overexpressed in numerous types of cancer, and is involved in the cell proliferation, invasion, migration and metastasis frequently observed in cancer. However, the role of STIM1 in colorectal cancer (CRC) remains unknown. The purpose of the present study was to investigate the effect of STIM1 in human CRC. The expression of STIM1 was specifically knocked down using lentivirus-mediated small hairpin RNA (shRNA) interference techniques in the CRC cell lines HCT116 and SW1116. Subsequently, the efficiency of infection was confirmed using green fluorescent protein (GFP)-positive signals. The knockdown efficiency was further determined using the reverse transcription-quantitative polymerase chain reaction and western blotting analysis. As a result, CRC cell lines with STIM1 silenced were successfully constructed and subsequently employed in a series of cell function assays. Knockdown of STIM1 significantly suppressed cell proliferation and colony formation, as revealed by an MTT and colony formation assay. Furthermore, it was identified that STIM1 silencing may promote cell apoptosis through the induction of mitochondria-associated apoptosis, as was identified by increased expression levels of B-cell lymphoma 2 (Bcl-2)-associated death promoter, Bcl-2-associated X protein and poly(ADP-ribose) polymerase cleavage. Therefore, STIM1 may serve a critical role in the progression of CRC by regulating cell proliferation and apoptosis, which may provide a potential therapeutic target for the treatment of CRC.

Elevated expression of STIM1 is involved in lung tumorigenesis

This study aimed to address the potential role of STIM1 (stromal interaction molecule 1) in lung tumorigenesis. Colony formation in soft agar assay and tumorigenicity in nude mice assay were conducted. Western blot, immunohistochemistry and quantitative real-time polymerase chain reaction were used to measure the STIM1 expression. The distribution of cell cycle was detected by flow cytometry assay. Our results showed that the expression of STIM1 mRNA was significantly higher in human lung tumors than that in adjacent non-neoplastic lung tissues. Significantly increased expression of STIM1 mRNA and protein was observed in 16HBE-benzo(a)pyrene (BaP) cells and in BaP-treated mice lung tissues compared with 16HBE-control cells and the control group, respectively. Silencing STIM1 inhibited the proliferation and colony formation of A549 cells in in vitro experiments, attenuated the growth of tumor xenografts of A549 cells in in vivo experiments and induced the arrest of cell cycle in the G1 phase. The markedly decreased expression of cyclin D1 protein was observed in A549-shRNA-STIM1 cells as compared to A549-shRNA-control cells. The markedly increased expression of p21 protein was observed in A549-shRNA-STIM1 cells as compared to A549-shRNA-control cells. The expression levels of β-catenin and TGIF proteins were lower in A549-shRNA-STIM1 cells than those in A549-shRNA-control cells. In conclusion, this study indicated that the elevated expression of STIM1 might be involved in lung tumorigenesis.

STIM1 deficiency protects the liver from ischemia/reperfusion injury in mice

Hepatic ischemia reperfusion (I/R) injury is unavoidable in various clinical conditions. Despite considerable investigation, the underlying molecular mechanism revealing liver I/R injury remains elusive. Stromal interaction molecule 1 (STIM1) plays essential role in regulating the induction of cellular responses to a number of stress conditions, including temperature changes, elevated ROS, and hypoxia. Here, to explore if STIM1 is involved in hepatic injury, wild type (WT) and STIM1-knockout (STIM1^-/-) mice were subjected to I/R. Our results indicated that the WT mice with hepatic I/R injury showed higher STIM1 expressions from gene and protein levels in liver tissue samples. Similar results were observed in hypoxia-exposed cells in vitro. Significantly, STIM1^-/- attenuated hepatic injury compared to the WT mice after I/R, as evidenced by the improved pathological alterations in liver sections. WT mice subjected to liver I/R showed higher serum alanine aminotransferase (ALT) and aminotransferase (AST) levels, as well as pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β, which were significantly reduced by STIM1^-/-. In addition, STIM1^-/- also decreased the liver mRNA levels of pro-inflammatory cytokines in mice after I/R injury. Furthermore, significantly decreased oxidative stress was found in STIM1^-/- mice after I/R injury compared to the WT group of mice, evidenced by the enhanced superoxide dismutase (SOD) activity and the reduced malondialdehyde (MDA) and reactive oxygen species (ROS) levels in liver tissue samples. Moreover, STIM1^-/- mice with hepatic I/R injury displayed the down-regulated nuclear factor of activated T cell (NFAT1), Orai1 and cleaved Caspase-3 levels in liver, contributing to apoptosis suppression. The results above were confirmed in hypoxia-treated cells lacking of STIM1 expression. Together, the findings suggested that STIM1-deletion protects the liver from I/R injury in mice through inhibiting inflammation, oxidative stress and apoptosis. STIM1 could be considered as a potential therapeutic target to ameliorate I/R injury.

Resveratrol attenuates high glucose-induced endothelial cell apoptosis via mediation of store-operated calcium entry

The aim of this study was to evaluate the influence of resveratrol on HG-induced calcium entry in islet microvascular (MS-1) endothelial cells. MS-1 cells were pretreated with resveratrol or 2-APB (an inhibitor of store-operated calcium entry) and then incubated with high glucose. Cell viability was determined using the cell counting kit-8 method. Reactive oxygen species, endothelial apoptosis, and NO production were detected by DHE probe, TUNEL detection, and nitrate reductase assay kit. Protein levels of SOCE were detected by western blotting. Pretreatment with resveratrol significantly attenuated HG-induced endothelial apoptosis and improved cell viability. However, pretreatment with resveratrol and 2-APB abolished this effect, suggesting that the attenuation of HG-induced apoptosis by resveratrol may be associated with SOCE. Subsequent analyses indicated that HG induced the SOCE-related proteins, including TRPC1, Orai1, and Stim1. These results suggest that resveratrol pretreatment is associated with relieved HG-induced endothelial apoptosis at least partly via inhibition of SOCE-related proteins.

STIM1 silencing inhibits the migration and invasion of A549 cells

The present study aimed to explore the effects of stromal interaction molecule 1 (STIM1) knockdown on the migration, invasion and metastasis of A549 cells in vitro and in vivo. Western blotting and immunohistochemistry were used to detect protein expression levels. Wound healing and Transwell invasion assays were used to assess the migratory and invasive abilities of A549 cells transfected with STIM1-specific short hairpin (sh)RNA (shSTIM1). In addition, a tail vein metastatic assay was performed. The results demonstrated that the frequency of STIM1 high-expression was significantly increased in metastatic lung cancer tissues (72.2%) compared with in non-metastatic lung cancer tissues (33.0%). STIM1 knockdown inhibited A549 cell migration and invasion in vitro and tumor metastasis in vivo. The protein expression levels of Snail1, Vimentin, matrix metalloproteinase (MMP) 2 and MMP9 were markedly decreased in A549-shSTIM1 compared with in A549 cells transfected with control shRNA (shcon). In addition, the protein expression levels of E-cadherin were markedly increased in A549-shSTIM1 cells compared with in A549-shcon cells. These results suggested that STIM1 knockdown may inhibit the migration and invasion of A549 cells in vitro, and metastasis in vivo.

Blocking of stromal interaction molecule 1 expression influence cell proliferation and promote cell apoptosis in vitro and inhibit tumor growth in vivo in head and neck squamous cell carcinoma

Calcium signal plays an important role in a variety of cancer cell metabolism, but knowledge on its role in head and neck squamous cell carcinoma (HNSCC) is limited. Store-operated calcium entry (SOCE) is the principal Ca2+ entry mechanism that maintains calcium concentration and produces calcium signal in non-excitable cells. SOCE is triggered by stromal interaction molecule 1 (STIM1), which is located in endoplasmic reticulum (ER) as Ca2+ sensor. Although, many studies demonstrated that STIM1 and SOCE play important functions in the regulation of many cancer progressions, their clinical relevance in HNSCC remains unclear. In this study, STIM1 expression levels notably increased in 89% HNSCC tissues compared with those in adjacent normal tissues. Meanwhile, this overexpression was close associated with tumor size but not with neck lymph node metastasis. Thus, this study mainly focuses on STIM1 function in HNSCC tumor growth. Three HNSCC cell lines, namely, TSCCA (oral cancer cell line) and Hep2 (laryngeal cell line) with high STIM1 expression levels and Tb3.1 (oral cancer cell line) with STIM1 expression level lower than previous two cell lines, were selected for in vitro study. Downregulated STIM1 expression levels in TSCCA and Hep2 arrested cells in G0/G1 stages, promoted cell apoptosis, and inhibited cell proliferation. By contrast, upregulated STIM1 expression in Tb3.1 inhibited cell apoptosis and promoted cell proliferation. Induced by thapsigargin (TG), ER stress was amplified when STIM1 expression was downregulated but was attenuated as STIM1 expression was upregulated. Furthermore, TSCCA cell xenograft models confirmed that STIM1 could promote HNSCC tumor growth in vivo. The present study provides new insight into HNSCC molecular mechanism and potential therapeutic target through targeting SOCE-dependent process. However, whether STIM1 participates in HNSCC metastasis requires further study.

Enhanced Stim1 expression is associated with acquired chemo-resistance of cisplatin in osteosarcoma cells

Osteosarcoma is the most common primary malignant bone tumor. Although cisplatin is the primary chemotherapy used in osteosarcoma treatment, the cisplatin resistance remains a big challenge for improving overall survival. The store-operated calcium (Ca²⁺) entry (SOCE) and its major mediator Stim1 have been shown to be implicated in a number of pathological processes typical for cancer. In this study, we showed that Stim1 expression was significantly increased in chemo-resistant osteosarcoma tissues compared with chemo-sensitivity tissues. Patients with Sitm1 expression exhibited poorer overall survival than Stim1-negative patients. Moreover, un-regulation of Stim1 expression and SOCE were also observed in cisplatin-resistant MG63/CDDP cells compared with their parental cells. Cisplatin treatment obviously reduced Stim1 expression and SOCE in cisplatin-sensitivity MG63 cells, but had no effects on MG63/CDDP cells. In addition, cisplatin resulted in a more pronounced increase of endoplasmic reticulum (ER) stress in MG63 cells than in their resistant variants, which was evidenced by the activation of molecular markers of ER stress, GRP78, CHOP and ATF4. Knockdown of Stim1 using siRNA remarkably enhanced cisplatin-induced apoptosis and ER stress in MG63/CDDP cells, thereby sensitizing cancer cells to cisplatin. On the other hand, overexpression of Stim1 markedly reversed apoptosis and ER stress following cisplatin treatment. Taken together, these results demonstrate that Stim1 as well as Ca²⁺ entry contributes cisplatin resistance via inhibition of ER stress-mediated apoptosis, and provide important clues to the mechanisms involved in cisplatin resistance for osteosarcoma treatment. Stim1 represents as a target of cisplatin and blockade of Stim1-mediated Ca²⁺ entry may be a useful strategy to improve the efficacy of cisplatin to treat osteosarcoma.

Stromal interaction molecule 1 regulates growth, cell cycle, and apoptosis of human tongue squamous carcinoma cells

Oral tongue squamous cell carcinoma (OTSCC) is the most common type of oral carcinomas. However, the molecular mechanism by which OTSCC developed is not fully identified. Stromal interaction molecule 1 (STIM1) is a transmembrane protein, mainly located in the endoplasmic reticulum (ER). STIM1 is involved in several types of cancers. Here, we report that STIM1 contributes to the development of human OTSCC. We knocked down STIM1 in OTSCC cell line Tca-8113 with lentivirus-mediated shRNA and found that STIM1 knockdown repressed the proliferation of Tca-8113 cells. In addition, we also showed that STIM1 deficiency reduced colony number of Tca-8113 cells. Knockdown of STIM1 repressed cells to enter M phase of cell cycle and induced cellular apoptosis. Furthermore, we performed microarray and bioinformatics analysis and found that STIM1 was associated with p53 and MAPK pathways, which may contribute to the effects of STIM1 on cell growth, cell cycle, and apoptosis. Finally, we confirmed that STIM1 controlled the expression of MDM2, cyclin-dependent kinase 4 (CDK4), and growth arrest and DNA damage inducible α (GADD45A) in OTSCC cells. In conclusion, we provide evidence that STIM1 contributes to the development of OTSCC partially through regulating p53 and MAPK pathways to promote cell cycle and survival.

Phemindole, a Synthetic Di-indole Derivative Maneuvers the Store Operated Calcium Entry (SOCE) to Induce Potent Anti-Carcinogenic Activity in Human Triple Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC), is a specific subtype of epithelial breast tumors that are immuno-histochemically negative for the protein expression of the estrogen receptor (ER), the progesterone receptor (PR) and lack over expression/gene amplification of HER2. This subtype of breast cancers is highly metastatic, shows poor prognosis and hence represents an important clinical challenge to researchers worldwide. Thus alternative approaches of drug development for TNBC have gained utmost importance in the present times. Dietary indole and its derivatives have gained prominence as anti-cancer agents and new therapeutic approaches are being developed to target them against TNBC. But a major drawback with 3, 3′di Indolyl methane (DIM) is their poor bioavailability and high effective concentration against TNBC. However, the Aryl methyl ring substituted analogs of DIM display interesting anti-cancer activity in breast cancer cells. In the current study we report the synthesis of a novel synthetic aryl methyl ring substituted analog of DIM, named as Phemindole as an effective anti-tumor agent against TNBC cells. Furthermore, we enumerated that Phemindole caused reactive oxygen species mediated mitochondrial-dependent apoptosis in MDAMB-231 cells. Furthermore, Phemindole mediated Store Operated Calcium Entry (SOCE) retardation favored inactivation of STIM1 and henceforth activated ER stress to induce apoptosis in TNBC cells. Simultaneously, Phemindole was also found to restrict the in vitro cell migration through its anti mitotic property and pFAK regulation. Studies extended to ex ovo and in vivo mice models further validated the efficacy of Phemindole. Thus our results cumulatively propose Phemindole as a new chemotherapeutic regime which might be effective to target the deadly aspects of the TNBC.

CRAC channels, calcium, and cancer in light of the driver and passenger concept

Advances in next-generation sequencing allow very comprehensive analyses of large numbers of cancer genomes leading to an increasingly better characterization and classification of cancers. Comparing genomic data predicts candidate genes driving development, growth, or metastasis of cancer. Cancer driver genes are defined as genes whose mutations are causally implicated in oncogenesis whereas passenger mutations are defined as not being oncogenic. Currently, a list of several hundred cancer driver mutations is discussed including prominent members like TP53, BRAF, NRAS, or NF1. According to the vast literature on Ca(2+) and cancer, Ca(2+) signals and the underlying Ca(2+) channels and transporters certainly influence the development, growth, and metastasis of many cancers. In this review, I focus on the calcium release-activated calcium (CRAC) channel genes STIM and Orai and their role for cancer development, growth, and metastasis. STIM and Orai genes are being discussed in the context of current cancer concepts with a focus on the driver-passenger hypothesis. One result of this discussion is the hypothesis that a driver analysis of Ca(2+) homeostasis-related genes should not be carried out by looking at isolated genes. Rather a pool of “Ca(2+) genes” might be considered to act as one potential cancer driver. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

SOCE and cancer: Recent progress and new perspectives

Ca²⁺ acts as a universal and versatile second messenger in the regulation of a myriad of biological processes, including cell proliferation, differentiation, migration and apoptosis. Store‐operated Ca²⁺ entry (SOCE) mediated by ORAI and the stromal interaction molecule (STIM) constitutes one of the major routes of calcium entry in nonexcitable cells, in which the depletion of intracellular Ca²⁺ stores triggers activation of the endoplasmic reticulum (ER)‐resident Ca²⁺ sensor protein STIM to gate and open the ORAI Ca²⁺ channels in the plasma membrane (PM). Accumulating evidence indicates that SOCE plays critical roles in cancer cell proliferation, metastasis and tumor neovascularization, as well as in antitumor immunity. We summarize herein the recent advances in our understanding of the function of SOCE in various types of tumor cells, vascular endothelial cells and cells of the immune system. Finally, the therapeutic potential of SOCE inhibitors in the treatment of cancer is also discussed.

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

Calcium (Ca(2+)) regulates a plethora of cellular functions including hallmarks of cancer development such as cell cycle progression and cellular migration. Receptor-regulated calcium rise in nonexcitable cells occurs through store-dependent as well as store-independent Ca(2+) entry pathways. Stromal interaction molecules (STIM) and Orai proteins have been identified as critical constituents of both these Ca(2+) influx pathways. STIMs and Orais have emerged as targets for cancer therapeutics as their altered expression and function have been shown to contribute to tumorigenesis. Recent data demonstrate that they play a vital role in development and metastasis of a variety of tumor types including breast, prostate, cervical, colorectal, brain, and skin tumors. In this review, we will retrospect the data supporting a key role for STIM1, STIM2, Orai1, and Orai3 proteins in tumorigenesis and discuss the potential of targeting these proteins for cancer therapy.

Role of store-operated calcium entry in digestive system tumors

Store-operated calcium entry (SOCE) is one of the important channels mediating extracellular Ca²⁺ entry. Stromal interaction molecule 1 (STIM1) protein in the membrane of endoplasmic reticulum and calcium release-activated calcium channel protein 1 (CRCM1/Orai1) protein in the plasma membrane are two key components of SOCE. Current research has gradually elucidated the mechanism of action of SOCE in tumors, and it has been demonstrated that SOCE plays an important role in digestive system tumors. This paper gives an overview of SOCE and reviews the current progress in understanding the role of SOCE in digestive system tumors.

Ion channels in the regulation of apoptosis

Apoptosis, a type of genetically controlled cell death, is a fundamental cellular mechanism utilized by multicellular organisms for disposal of cells that are no longer needed or potentially detrimental. Given the crucial role of apoptosis in physiology, deregulation of apoptotic machinery is associated with various diseases as well as abnormalities in development. Acquired resistance to apoptosis represents the common feature of most and perhaps all types of cancer. Therefore, repairing and reactivating apoptosis represents a promising strategy to fight cancer. Accumulated evidence identifies ion channels as essential regulators of apoptosis. However, the contribution of specific ion channels to apoptosis varies greatly depending on cell type, ion channel type and intracellular localization, pathology as well as intracellular signaling pathways involved. Here we discuss the involvement of major types of ion channels in apoptosis regulation. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Orai1 and STIM1 mediate SOCE and contribute to apoptotic resistance of pancreatic adenocarcinoma

The store-operated calcium channels (SOCs) represent one of the major calcium-entry pathways in non-excitable cells. SOCs and in particular their major components ORAI1 and STIM1 have been shown to be implicated in a number of physiological and pathological processes such as apoptosis, proliferation and invasion. Here we demonstrate that ORAI1 and STIM1 mediate store-operated calcium entry (SOCE) in pancreatic adenocarcinoma cell lines. We show that both ORAI1 and STIM1 play pro-survival anti-apoptotic role in pancreatic adenocarcinoma cell lines, as siRNA-mediated knockdown of ORAI1 and/or STIM1 increases apoptosis induced by chemotherapy drugs 5-fluorouracil (5-FU) or gemcitabine. We also demonstrate that both 5-FU and gemcitabine treatments increase SOCE in Panc1 pancreatic adenocarcinoma cell line via upregulation of ORAI1 and STIM1. Altogether our results reveal the novel calcium-dependent mechanism of action of the chemotherapy drugs 5-FU and gemcitabine and emphasize the anti-apoptotic role of ORAI1 and STIM1 in pancreatic adenocarcinoma cells. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.