Altered expression of stromal interaction molecule (STIM)-calcium release-activated calcium channel protein (ORAI) and inositol 1,4,5-trisphosphate receptors (IP3Rs) in cancer: will they become a new battlefield for oncotherapy?

Blocking SIG1R Along with Low Cadmium Exposure Display Anti-cancer Qualities in Both MCF7 and MDA-MB-231 Cells

Sigma-1 receptor (SIG1R) is a chaperone that modulates inositol 1,4,5-trisphosphate receptor type1 (IP3R1) calcium (Ca2+) channels on the endoplasmic reticulum. Therefore, SIG1R functions as an indirect regulator of Ca2+ and acts as an apoptosis modulator. Increased expression of SIG1R is associated with poor prognosis in breast cancers (BC), and SIG1R antagonists like BD1047 induce apoptosis. As a heavy metal, cadmium (Cd2+) is competitive with Ca2+ due to its physicochemical similarities and may trigger apoptosis at low concentrations. Our study investigated the SIG1R protein expression in 74 BC patients and found a significant increase in SIG1R expression in the triple-negative BC subtype. We also examined the apoptotic and anti-cancer effects of BD1047 in combination with CdCl2 in MCF7 and MDA-MB-213 cells. Cells were treated with CdCl2 at doses of 1 μM, 25 μM, and 50 μM, along with BD1047. Higher doses of CdCl2 were cytotoxic on both cancer cells and significantly increased DNA breaks. However, low-dose CdCl2 with BD1047 increased cell death and the apoptotic index in BC cells, although it did not exhibit cytotoxic effects on HUVEC cells. Co-administration of low-dose CdCl2 with BD1047 also reduced the migration and colony-forming ability of BC cells. Moreover, the expression of SIG1R protein in these groups decreased significantly compared to groups treated with BD1047 or low-dose CdCl2 alone. In conclusion, low-dose CdCl2 is thought to increase the apoptotic ability of BD1047 in BC cells by reducing SIG1R expression.

Activation mechanisms and structural dynamics of STIM proteins

The family of stromal interaction molecules (STIM) includes two widely expressed single-pass endoplasmic reticulum (ER) transmembrane proteins and additional splice variants that act as precise ER-luminal Ca2+ sensors. STIM proteins mainly function as one of the two essential components of the so-called Ca2+ release-activated Ca2+ (CRAC) channel. The second CRAC channel component is constituted by pore-forming Orai proteins in the plasma membrane. STIM and Orai physically interact with each other to enable CRAC channel opening, which is a critical prerequisite for various downstream signalling pathways such as gene transcription or proliferation. Their activation commonly requires the emptying of the intracellular ER Ca2+ store. Using their Ca2+ sensing capabilities, STIM proteins confer this Ca2+ content-dependent signal to Orai, thereby linking Ca2+ store depletion to CRAC channel opening. Here we review the conformational dynamics occurring along the entire STIM protein upon store depletion, involving the transition from the quiescent, compactly folded structure into an active, extended state, modulation by a variety of accessory components in the cell as well as the impairment of individual steps of the STIM activation cascade associated with disease.

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.

Progress on role of ion channels of cardiac fibroblasts in fibrosis

Cardiac fibrosis is defined as excessive deposition of extracellular matrix (ECM) in pathological conditions. Cardiac fibroblasts (CFs) activated by injury or inflammation differentiate into myofibroblasts (MFs) with secretory and contractile functions. In the fibrotic heart, MFs produce ECM which is composed mainly of collagen and is initially involved in maintaining tissue integrity. However, persistent fibrosis disrupts the coordination of excitatory contractile coupling, leading to systolic and diastolic dysfunction, and ultimately heart failure. Numerous studies have demonstrated that both voltage- and non-voltage-gated ion channels alter intracellular ion levels and cellular activity, contributing to myofibroblast proliferation, contraction, and secretory function. However, an effective treatment strategy for myocardial fibrosis has not been established. Therefore, this review describes the progress made in research related to transient receptor potential (TRP) channels, Piezo1, Ca²⁺ release-activated Ca²⁺ (CRAC) channels, voltage-gated Ca²⁺ channels (VGCCs), sodium channels, and potassium channels in myocardial fibroblasts with the aim of providing new ideas for treating myocardial fibrosis.

Aberrant calcium signalling downstream of mutations in TP53 and the PI3K/AKT pathway genes promotes disease progression and therapy resistance in triple negative breast cancer

Triple-negative breast cancer (TNBC) is characterized as an aggressive form of breast cancer (BC) associated with poor patient outcomes. For the majority of patients, there is a lack of approved targeted therapies. Therefore, chemotherapy remains a key treatment option for these patients, but significant issues around acquired resistance limit its efficacy. Thus, TNBC has an unmet need for new targeted personalized medicine approaches. Calcium (Ca²⁺) is a ubiquitous second messenger that is known to control a range of key cellular processes by mediating signalling transduction and gene transcription. Changes in Ca²⁺ through altered calcium channel expression or activity are known to promote tumorigenesis and treatment resistance in a range of cancers including BC. Emerging evidence shows that this is mediated by Ca²⁺ modulation, supporting the function of tumour suppressor genes (TSGs) and oncogenes. This review provides insight into the underlying alterations in calcium signalling and how it plays a key role in promoting disease progression and therapy resistance in TNBC which harbours mutations in tumour protein p53 (TP53) and the PI3K/AKT pathway.

Altered Expression of ORAI and STIM Isoforms in Activated Human Cardiac Fibroblasts

Cardiac fibrotization is a well-known process characteristic of many cardiac pathological conditions. The key element is excessive activation of cardiac fibroblasts, their transdifferentiation into myofibroblasts, increased production, and accumulation of extracellular matrix proteins, resulting in cardiac stiffness. The exact cellular mechanisms and molecular components involved in the process are not fully elucidated, but the SOCE mechanism could play an important role. Its key molecules are the molecular sensor of calcium in ER/SR - STIM and the highly selective calcium channels Orai located in the plasma membrane. This study aims to evaluate selected SOCE-associated genes in the activation of HCF cell culture by several known substances (phenylephrine, isoprenaline) that represent cardiovascular overload. After cell cultivation, cell medium was collected to measure the soluble collagen content. From the harvested cells, qRT-PCR was performed to determine the mRNA levels of the corresponding genes. The activation of cells was based on changes in the relative expression of collagen genes as well as the collagen content in the medium of the cell culture. We detected an increase in the expression of the Orai2 isoform, a change in the Orai1/Orai3 ratio and also an increase in the expression of the STIM2 isoform. These results suggest an increased activation of the SOCE mechanism under stress conditions of fibroblasts, which supports the hypothesis of fibroblast activation in pathological processes by altering calcium homeostasis through the SOCE mechanism.

Cell death as a result of calcium signaling modulation: A cancer-centric prospective

Calcium ions (Ca²⁺) and the complex regulatory system governed by Ca²⁺ signaling have been described to be of crucial importance in numerous aspects related to cell life and death decisions, especially in recent years. The growing attention given to this second messenger is justified by the pleiotropic nature of Ca²⁺-binding proteins and transporters and their consequent involvement in cell fate decisions. A growing number of works highlight that deregulation of Ca²⁺ signaling and homoeostasis is often deleterious and drives pathological conditions; in particular, a disruption of the main Ca²⁺-mediated death mechanisms may lead to uncontrolled cell growth that results in cancer. In this work, we review the latest useful evidence to better understand the complex network of pathways by which Ca²⁺ regulates cell life and death decisions.

Altered Organelle Calcium Transport in Ovarian Physiology and Cancer

Calcium levels have a huge impact on the physiology of the female reproductive system, in particular, of the ovaries. Cytosolic calcium levels are influenced by regulatory proteins (i.e., ion channels and pumps) localized in the plasmalemma and/or in the endomembranes of membrane-bound organelles. Imbalances between plasma membrane and organelle-based mechanisms for calcium regulation in different ovarian cell subtypes are contributing to ovarian pathologies, including ovarian cancer. In this review, we focused our attention on altered calcium transport and its role as a contributor to tumor progression in ovarian cancer. The most important proteins described as contributing to ovarian cancer progression are inositol trisphosphate receptors, ryanodine receptors, transient receptor potential channels, calcium ATPases, hormone receptors, G-protein-coupled receptors, and/or mitochondrial calcium uniporters. The involvement of mitochondrial and/or endoplasmic reticulum calcium imbalance in the development of resistance to chemotherapeutic drugs in ovarian cancer is also discussed, since Ca²⁺ channels and/or pumps are nowadays regarded as potential therapeutic targets and are even correlated with prognosis.

Integrative natural medicine inspired graphene nanovehicle-benzoxazine derivatives as potent therapy for cancer

Natural products from medicinal plants have always attracted a lot of attention due to their diverse and interesting therapeutic properties. We have employed the principles of green chemistry involving isomerization, coupling and condensation reaction to synthesize a class of compounds derived from eugenol, a naturally occurring bioactive phytophenol. The compounds were characterized structurally by ¹H-, ¹³C-NMR, FT-IR spectroscopy and mass spectrometry analysis. The purity of compounds was detected by HPLC. The synthesized compounds exhibited anti-cancer activity. A 10-12-fold enhancement in efficiency of drug molecules (~ 1 µM) was observed when delivered with graphene oxide (GO) as a nanovehicle. Our data suggest cell death via apoptosis in a dose-dependent manner due to increase in calcium levels in specific cancer cell lines. Interestingly, the benzoxazine derivatives of eugenol with GO nanoparticle exhibited enhanced therapeutic potential in cancer cells. In addition to anti-cancer effect, we also observed significant role of these derivatives on parasite suggesting its multi-pharmacological capability.

Oncogenic KRAS suppresses store-operated Ca2+ entry and ICRAC through ERK pathway-dependent remodelling of STIM expression in colorectal cancer cell lines

The KRAS GTPase plays a fundamental role in transducing signals from plasma membrane growth factor receptors to downstream signalling pathways controlling cell proliferation, survival and migration. Activating KRAS mutations are found in 20% of all cancers and in up to 40% of colorectal cancers, where they contribute to dysregulation of cell processes underlying oncogenic transformation. Multiple KRAS-regulated cell functions are also influenced by changes in intracellular Ca2+ levels that are concurrently modified by receptor signalling pathways. Suppression of intracellular Ca2+ release mechanisms can confer a survival advantage in cancer cells, and changes in Ca2+ entry across the plasma membrane modulate cell migration and proliferation. However, inconsistent remodelling of Ca2+ influx and its signalling role has been reported in studies of transformed cells. To isolate the interaction between altered Ca2+ handling and mutated KRAS in colorectal cancer, we have previously employed isogenic cell line pairs, differing by the presence of an oncogenic KRAS allele (encoding KRASG13D), and have shown that reduced Ca2+ release from the ER and mitochondrial Ca2+ uptake contributes to the survival advantage conferred by oncogenic KRAS. Here we show in the same cell lines, that Store-Operated Ca2+ Entry (SOCE) and its underlying current, ICRAC are under the influence of KRASG13D. Specifically, deletion of the oncogenic KRAS allele resulted in enhanced STIM1 expression and greater Ca2+ influx. Consistent with the role of KRAS in the activation of the ERK pathway, MEK inhibition in cells with KRASG13D resulted in increased STIM1 expression. Further, ectopic expression of STIM1 in HCT 116 cells (which express KRASG13D) rescued SOCE, demonstrating a fundamental role of STIM1 in suppression of Ca2+ entry downstream of KRASG13D. These results add to the understanding of how ERK controls cancer cell physiology and highlight STIM1 as an important biomarker in cancerogenesis.

Targeting Intracellular Calcium Signaling ([Ca2+]i) to Overcome Acquired Multidrug Resistance of Cancer Cells: A Mini-Overview

Cancer is a main public health problem all over the world. It affects millions of humans no matter their age, gender, education, or social status. Although chemotherapy is the main strategy for the treatment of cancer, a major problem limiting its success is the intrinsic or acquired drug resistance. Therefore, cancer drug resistance is a major impediment in medical oncology resulting in a failure of a successful cancer treatment. This mini-overview focuses on the interdependent relationship between intracellular calcium ([Ca²⁺]_i) signaling and multidrug resistance of cancer cells, acquired upon treatment of tumors with anticancer drugs. We propose that [Ca²⁺]_i signaling modulates gene expression of multidrug resistant (MDR) genes which in turn can be modulated by epigenetic factors which in turn leads to modified protein expression in drug resistant tumor cells. A precise knowledge of these mechanisms will help to develop new therapeutic strategies for drug resistant tumors and will improve current chemotherapy.

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.