STIM1 plays an important role in TGF-β-induced suppression of breast cancer cell proliferation

Adaptation of STIM1 structure-function relationships for optogenetic control of calcium signaling

In cellular contexts, the oscillation of calcium ions (Ca2+) is intricately linked to various physiological processes, such as cell proliferation, metabolism, and survival. Stromal interaction molecule 1 (STIM1) proteins form a crucial regulatory component in the store-operated calcium entry (SOCE) process. The structural attributes of STIM1 are vital for its functionality, encompassing distinct domains situated in the endoplasmic reticulum (ER) lumen and the cytoplasm. The intraluminal domain enables the timely detection of diminishing Ca2+ concentrations, prompting structural modifications that activate the cytoplasmic domain. This activated cytoplasmic domain undergoes conformational alterations and engages with membrane components, opening a channel that facilitates the influx of Ca2+ from the extracellular environment. Given its multiple domains and interaction mechanisms, STIM1 plays a foundational role in cellular biology. This review focuses on the design of optogenetic tools inspired by the structure and function of STIM1. These tools offer a groundbreaking approach for studying and manipulating intracellular Ca2+ signaling with precisely spatiotemporal control. We further explore the practical applications of these tools, spanning fundamental scientific research, clinical studies, and their potential for translational research.

The Cytoplasmic Region of SARAF Reduces Triple-Negative Breast Cancer Metastasis through the Regulation of Store-Operated Calcium Entry

Triple-negative breast cancer has a poor prognosis and is non-responsive to first-line therapies; hence, new therapeutic strategies are needed. Enhanced store-operated Ca2+ entry (SOCE) has been widely described as a contributing factor to tumorigenic behavior in several tumor types, particularly in breast cancer cells. SOCE-associated regulatory factor (SARAF) acts as an inhibitor of the SOCE response and, therefore, can be a potential antitumor factor. Herein, we generated a C-terminal SARAF fragment to evaluate the effect of overexpression of this peptide on the malignancy of triple-negative breast cancer cell lines. Using both in vitro and in vivo approaches, we showed that overexpression of the C-terminal SARAF fragment reduced proliferation, cell migration, and the invasion of murine and human breast cancer cells by decreasing the SOCE response. Our data suggest that regulating the activity of the SOCE response via SARAF activity might constitute the basis for further alternative therapeutic strategies for triple-negative breast cancer.

Knockdown of Stromal Interaction Molecule 1 (STIM1) Suppresses Acute Myeloblastic Leukemia-M5 Cell Line Survival Through Inhibition of Reactive Oxygen Species Activities

Objective

This study aimed to investigate the role of the stromal interaction molecule 1 (STIM1) gene in the survival of the acute myeloblastic leukemia (AML)-M5 cell line (THP-1).

Materials and Methods

The STIM1 effect was assessed via dicersubstrate siRNA-mediated STIM1 knockdown. The effect of STIM1 knockdown on the expression of AKT and MAPK pathway-related genes and reactive oxygen species (ROS) generation-related genes was tested using real-time polymerase chain reaction. Cellular functions, including ROS generation, cell proliferation, and colony formation, were also evaluated following STIM1 knockdown.

Results

The findings revealed that STIM1 knockdown reduced intracellular ROS levels via downregulation of NOX2 and PKC. These findings were associated with the downregulation of AKT, KRAS, MAPK, and CMYC. BCL2 was also downregulated, while BAX was upregulated following STIM1 knockdown. Furthermore, STIM1 knockdown reduced THP-1 cell proliferation and colony formation.

Conclusion

This study has demonstrated the role of STIM1 in promoting AML cell proliferation and survival through enhanced ROS generation and regulation of AKT/MAPK-related pathways. These findings may help establish STIM1 as a potential therapeutic target for AML treatment.

MiR-191-5p inhibits KLF6 to promote epithelial-mesenchymal transition in breast cancer

BACKGROUND

MicroRNAs (miRNAs) exert certain functions in the development of several cancers and can be a potential hallmark for cancer diagnosis and prognosis. MiR-191-5p has been proven to have high expression in breast cancer (BC), while its biological role and potential regulatory mechanisms in BC remain an open issue.

OBJECTIVE

Bioinformatics was utilized to assay miR-191-5p level in BC tissues and predict its downstream target gene as well as the enriched signaling pathways of the target gene.

METHODS

qRT-PCR was carried out to assay miR-191-5p and KLF6 levels in BC cells as well as miR-191-5p level in blood-derived exosomes from BC patients. Western blot was to examine the expression of proteins linked with cell adhesion, epithelial-mesenchymal transition (EMT), and exosome markers. A dual luciferase reporter assay was utilized to verify the interaction between miR-191-5p and KLF6. Abilities of cell phenotypes of BC cells were detected by CCK8, Transwell, and cell adhesion assay, separately.

RESULTS

Upregulated miR-191-5p expression and downregulated KLF6 expression were observed in BC cells. There was a targeting relationship between miR-191-5p and KLF6. MiR-191-5p negatively regulated KLF6 to promote EMT and malignant progression of BC cells. Additionally, we described a dramatically high level of miR-191-5p in the blood exosomes of BC patients.

CONCLUSION

MiR-191-5p advances the EMT of BC by targeting KLF6, indicating that miR-191-5p and KLF6 may be new biomarkers for BC.

Advances in Intracellular Calcium Signaling Reveal Untapped Targets for Cancer Therapy

Intracellular Ca2+ distribution is a tightly regulated process. Numerous Ca2+ chelating, storage, and transport mechanisms are required to maintain normal cellular physiology. Ca2+-binding proteins, mainly calmodulin and calbindins, sequester free intracellular Ca2+ ions and apportion or transport them to signaling hubs needing the cations. Ca2+ channels, ATP-driven pumps, and exchangers assist the binding proteins in transferring the ions to and from appropriate cellular compartments. Some, such as the endoplasmic reticulum, mitochondria, and lysosomes, act as Ca2+ repositories. Cellular Ca2+ homeostasis is inefficient without the active contribution of these organelles. Moreover, certain key cellular processes also rely on inter-organellar Ca2+ signaling. This review attempts to encapsulate the structure, function, and regulation of major intracellular Ca2+ buffers, sensors, channels, and signaling molecules before highlighting how cancer cells manipulate them to survive and thrive. The spotlight is then shifted to the slow pace of translating such research findings into anticancer therapeutics. We use the PubMed database to highlight current clinical studies that target intracellular Ca2+ signaling. Drug repurposing and improving the delivery of small molecule therapeutics are further discussed as promising strategies for speeding therapeutic development in this area.

Calcium Channel Protein ORAI1 Mediates TGF-β Induced Epithelial-to-Mesenchymal Transition in Colorectal Cancer Cells

Accumulating evidence suggested that calcium release-activated calcium modulator 1(ORAI1), a key calcium channel pore-forming protein-mediated store-operated Ca2+ entry (SOCE), is associated with human cancer. However, its role in colorectal cancer (CRC) progression has not been well studied. Epithelial-mesenchymal transition (EMT) is a multistep process that occurs during the progression of cancers and is necessary for metastasis of epithelial cancer. Transforming growth factor-β (TGF-β) is a pleiotropic cytokine that has been shown to induce EMT. In this study, we are aimed at exploring the effects of ORAI1 on TGF-β1-induced EMT process in CRC cells. Herein, we confirmed ORAI1 expression was higher in CRC tissues than in adjacent non-cancerous tissues by using immunohistochemical staining and Western blot analysis. Higher ORAI1 expression was associated with more advanced clinical stage, higher incidence of metastasis and shorter overall survival. We compared ORAI1 expression in SW480 and SW620 cells, two CRC cell lines with the same genetic background, but different metastatic potential. We found ORAI1 expression was significantly higher in SW620 cells which exhibited higher EMT characteristics. Furthermore, knockdown of ORAI1 suppressed the EMT of SW620 Cells. After induced the EMT process in SW480 cells with TGF-β1, we found treatment of TGF-β1 showed a significant increase in cell migration along with the loss of E-cadherin and an increase in N-cadherin and Vimentin protein levels. Also, TGF-β1 treatment increased ORAI1 expression and was closely associated with the increase of SOCE. Silencing ORAI1 significantly suppressed Ca2+ entry, reversed the changes of EMT-relevant marks expression induced by TGF-β1, and inhibited TGF-β1-mediated calpain activation and cell migration. Finally, we blocked SOCE with 2-APB (2-Aminoethyl diphenylborinate), a pharmacological inhibitor. Interestingly, 2-APB and sh-ORAI1 both exhibited similar inhibition effects to the SW480 cells. In conclusion, our results demonstrated that ORAI1 could mediate TGF-β-Induced EMT by promoting Ca2+ entry and calpain activity in Colorectal Cancer Cells.

Purkinje Neurons with Loss of STIM1 Exhibit Age-Dependent Changes in Gene Expression and Synaptic Components

The stromal interaction molecule 1 (STIM1) is an ER-Ca²⁺ sensor and an essential component of ER-Ca²⁺ store operated Ca²⁺ entry. Loss of STIM1 affects metabotropic glutamate receptor 1 (mGluR1)-mediated synaptic transmission, neuronal Ca²⁺ homeostasis, and intrinsic plasticity in Purkinje neurons (PNs). Long-term changes of intracellular Ca²⁺ signaling in PNs led to neurodegenerative conditions, as evident in individuals with mutations of the ER-Ca²⁺ channel, the inositol 1,4,5-triphosphate receptor. Here, we asked whether changes in such intrinsic neuronal properties, because of loss of STIM1, have an age-dependent impact on PNs. Consequently, we analyzed mRNA expression profiles and cerebellar morphology in PN-specific STIM1 KO mice (STIM1^PKO ) of both sexes across ages. Our study identified a requirement for STIM1-mediated Ca²⁺ signaling in maintaining the expression of genes belonging to key biological networks of synaptic function and neurite development among others. Gene expression changes correlated with altered patterns of dendritic morphology and greater innervation of PN dendrites by climbing fibers, in aging STIM1^PKO mice. Together, our data identify STIM1 as an important regulator of Ca²⁺ homeostasis and neuronal excitability in turn required for maintaining the optimal transcriptional profile of PNs with age. Our findings are significant in the context of understanding how dysregulated calcium signals impact cellular mechanisms in multiple neurodegenerative disorders.SIGNIFICANCE STATEMENT In Purkinje neurons (PNs), the stromal interaction molecule 1 (STIM1) is required for mGluR1-dependent synaptic transmission, refilling of ER Ca²⁺ stores, regulation of spike frequency, and cerebellar memory consolidation. Here, we provide evidence for a novel role of STIM1 in maintaining the gene expression profile and optimal synaptic connectivity of PNs. Expression of genes related to neurite development and synaptic organization networks is altered in PNs with persistent loss of STIM1. In agreement with these findings the dendritic morphology of PNs and climbing fiber innervations on PNs also undergo significant changes with age. These findings identify a new role for dysregulated intracellular calcium signaling in neurodegenerative disorders and provide novel therapeutic insights.

Quantitative Proteomic Analysis in Alveolar Type II Cells Reveals the Different Capacities of RAS and TGF-β to Induce Epithelial-Mesenchymal Transition

Alveolar type II (ATII) epithelial cells function as stem cells, contributing to alveolar renewal, repair and cancer. Therefore, they are a highly relevant model for studying a number of lung diseases, including acute injury, fibrosis and cancer, in which signals transduced by RAS and transforming growth factor (TGF)-β play critical roles. To identify downstream molecular events following RAS and/or TGF-β activation, we performed proteomic analysis using a quantitative label-free approach (LC-HDMS^E) to provide in-depth proteome coverage and estimates of protein concentration in absolute amounts. Data are available via ProteomeXchange with identifier PXD023720. We chose ATII^ER:KRASV12 as an experimental cell line in which RAS is activated by adding 4-hydroxytamoxifen (4-OHT). Proteomic analysis of ATII cells treated with 4-OHT or TGF-β demonstrated that RAS activation induces an epithelial–mesenchymal transition (EMT) signature. In contrast, under the same conditions, activation of TGF-β signaling alone only induces a partial EMT. EMT is a dynamic and reversible biological process by which epithelial cells lose their cell polarity and down-regulate cadherin-mediated cell–cell adhesion to gain migratory properties, and is involved in embryonic development, wound healing, fibrosis and cancer metastasis. Thus, these results could help to focus research on the identification of processes that are potentially driving EMT-related human disease.

Regulation of breast cancer metastasis signaling by miRNAs

Despite the decline in death rate from breast cancer and recent advances in targeted therapies and combinations for the treatment of metastatic disease, metastatic breast cancer remains the second leading cause of cancer-associated death in U.S. women. The invasion-metastasis cascade involves a number of steps and multitudes of proteins and signaling molecules. The pathways include invasion, intravasation, circulation, extravasation, infiltration into a distant site to form a metastatic niche, and micrometastasis formation in a new environment. Each of these processes is regulated by changes in gene expression. Noncoding RNAs including microRNAs (miRNAs) are involved in breast cancer tumorigenesis, progression, and metastasis by post-transcriptional regulation of target gene expression. miRNAs can stimulate oncogenesis (oncomiRs), inhibit tumor growth (tumor suppressors or miRsupps), and regulate gene targets in metastasis (metastamiRs). The goal of this review is to summarize some of the key miRNAs that regulate genes and pathways involved in metastatic breast cancer with an emphasis on estrogen receptor α (ERα+) breast cancer. We reviewed the identity, regulation, human breast tumor expression, and reported prognostic significance of miRNAs that have been documented to directly target key genes in pathways, including epithelial-to-mesenchymal transition (EMT) contributing to the metastatic cascade. We critically evaluated the evidence for metastamiRs and their targets and miRNA regulation of metastasis suppressor genes in breast cancer progression and metastasis. It is clear that our understanding of miRNA regulation of targets in metastasis is incomplete.

Melatonin downregulates TRPC6, impairing store-operated calcium entry in triple-negative breast cancer cells

Melatonin has been reported to induce effective reduction in growth and development in a variety of tumors, including breast cancer. In triple-negative breast cancer (TNBC) cells, melatonin attenuates a variety of cancer features, such as tumor growth and apoptosis resistance, through a number of still poorly characterized mechanisms. One biological process that is important for TNBC cells is store-operated Ca2+ entry (SOCE), which is modulated by TRPC6 expression and function. We wondered whether melatonin might intersect with this pathway as part of its anticancer activity. We show that melatonin, in the nanomolar range, significantly attenuates TNBC MDA-MB-231 cell viability, proliferation, and migration in a time- and concentration-dependent manner, without having any effect on nontumoral breast epithelial MCF10A cells. Pretreatment with different concentrations of melatonin significantly reduced SOCE in MDA-MB-231 cells without altering Ca2+ release from the intracellular stores. By contrast, SOCE in MCF10A cells was unaffected by melatonin. In the TNBC MDA-MB-468 cell line, melatonin not only attenuated viability, migration, and SOCE, but also reduced TRPC6 expression in a time- and concentration-dependent manner, without altering expression or function of the Ca2+ channel Orai1. The expression of exogenous TRPC6 overcame the effect of melatonin on SOCE and cell proliferation, and silencing or inhibition of TRPC6 impaired the inhibitory effect of melatonin on SOCE. These findings indicate that TRPC6 downregulation might be involved in melatonin's inhibitory effects on Ca2+ influx and the maintenance of cancer hallmarks and point toward a novel antitumoral mechanism of melatonin in TNBC cells.

The Role of Calcium Signaling in Regulation of Epithelial-Mesenchymal Transition

Despite substantial advances in the field of cancer therapeutics, metastasis is a significant challenge for a favorable clinical outcome. Epithelial to mesenchymal transition (EMT) is a process of acquiring increased motility, invasiveness, and therapeutic resistance by cancer cells for their sustained growth and survival. A plethora of intrinsic mechanisms and extrinsic microenvironmental factors drive the process of cancer metastasis. Calcium (Ca2+) signaling plays a critical role in dictating the adaptive metastatic cell behavior comprising of cell migration, invasion, angiogenesis, and intravasation. By modulating EMT, Ca2+ signaling can regulate the complexity and dynamics of events leading to metastasis. This review summarizes the role of Ca2+ signal remodeling in the regulation of EMT and metastasis in cancer.

Potassium and Calcium Channel Complexes as Novel Targets for Cancer Research

The intracellular Ca²⁺ concentration is mainly controlled by Ca²⁺ channels. These channels form complexes with K⁺ channels, which function to amplify Ca²⁺ flux. In cancer cells, voltage-gated/voltage-dependent Ca²⁺ channels and non-voltage-gated/voltage-independent Ca²⁺ channels have been reported to interact with K⁺ channels such as Ca²⁺-activated K⁺ channels and voltage-gated K⁺ channels. These channels are activated by an increase in cytosolic Ca²⁺ concentration or by membrane depolarization, which induces membrane hyperpolarization, increasing the driving force for Ca²⁺ flux. These complexes, composed of K⁺ and Ca²⁺ channels, are regulated by several molecules including lipids (ether lipids and cholesterol), proteins (e.g. STIM), receptors (e.g. S1R/SIGMAR1), and peptides (e.g. LL-37) and can be targeted by monoclonal antibodies, making them novel targets for cancer research.

Pathological role of ion channels and transporters in the development and progression of triple-negative breast cancer

Breast cancer is a common malignancy in women. Among breast cancer types, triple-negative breast cancer (TNBC) tends to affect younger women, is prone to axillary lymph node, lung, and bone metastases; and has a high recurrence rate. Due to a lack of classic biomarkers, the currently available treatments are surgery and chemotherapy; no targeted standard treatment options are available. Therefore, it is urgent to find a novel and effective therapeutic target. As alteration of ion channels and transporters in normal mammary cells may affect cell growth, resulting in the development and progression of TNBC, ion channels and transporters may be promising new therapeutic targets for TNBC. This review summarizes ion channels and transporters related to TNBC and may provide new tumor biomarkers and help in the development of novel targeted therapies.

Calcium Homeostasis: A Potential Vicious Cycle of Bone Metastasis in Breast Cancers

Cancers have been considered as one of the most severe health problems in the world. Efforts to elucidate the cancer progression reveal the importance of bone metastasis for tumor malignancy, one of the leading causes for high mortality rate. Multiple cancers develop bone metastasis, from which breast cancers exhibit the highest rate and have been well-recognized. Numerous cells and environmental factors have been believed to synergistically facilitate bone metastasis in breast cancers, from which breast cancer cells, osteoclasts, osteoblasts, and their produced cytokines have been well-recognized to form a vicious cycle that aggravates tumor malignancy. Except the cytokines or chemokines, calcium ions are another element largely released from bones during bone metastasis that leads to hypercalcemia, however, have not been well-characterized yet in modulation of bone metastasis. Calcium ions act as a type of unique second messenger that exhibits omnipotent functions in numerous cells, including tumor cells, osteoclasts, and osteoblasts. Calcium ions cannot be produced in the cells and are dynamically fluxed among extracellular calcium pools, intracellular calcium storages and cytosolic calcium signals, namely calcium homeostasis, raising a possibility that calcium ions released from bone during bone metastasis would further enhance bone metastasis and aggravate tumor progression via the vicious cycle due to abnormal calcium homeostasis in breast cancer cells, osteoclasts and osteoblasts. TRPs, VGCCs, SOCE, and P2Xs are four major calcium channels/routes mediating extracellular calcium entry and affect calcium homeostasis. Here we will summarize the overall functions of these four calcium channels in breast cancer cells, osteoclasts and osteoblasts, providing evidence of calcium homeostasis as a vicious cycle in modulation of bone metastasis in breast cancers.

The role of WT1 in breast cancer: clinical implications, biological effects and molecular mechanism

Although Wilms' tumor gene 1 (WT1) was first cloned and identified as a tumor suppressor gene in nephroblastoma, subsequent studies have demonstrated that it can also play an oncogenic role in leukemia and various solid tumors. WT1 exerts biological functions with high tissue- and cell-specificity. This article reviews the relationship between WT1 and breast cancer from two aspects: (1) clinical application of WT1, including the relationship between expression of WT1 and prognosis of breast cancer patients, and its effectiveness as a target for comprehensive therapy of breast cancer; (2) the biological effects and molecular mechanisms of WT1 in the development and progression of breast cancer, including proliferation, apoptosis, invasion, and metastasis of breast cancer cells.

Assessment of doxorubicin-induced remodeling of Ca2+ signaling and associated Ca2+ regulating proteins in MDA-MB-231 breast cancer cells

Triple-negative breast cancers (TNBC) are often associated with high relapse rates, despite treatment with chemotherapy agents such as doxorubicin. A better understanding of the signaling and molecular changes associated with doxorubicin may provide novel insights into strategies to enhance treatment efficacy. Calcium signaling is involved in many pathways influencing the efficacy of chemotherapy agents such as proliferation and cell death. However, there are a limited number of studies exploring the effect of doxorubicin on calcium signaling in TNBC. In this study, MDA-MB-231 triple-negative, basal breast cancer cells stably expressing the genetically-encoded calcium indicator GCaMP6m (GCaMP6m-MDA-MB-231) were used to define alterations in calcium signaling. The effects of doxorubicin in GCaMP6m-MDA-MB-231 cells were determined using live cell imaging and fluorescence microscopy. Changes in mRNA levels of specific calcium regulating proteins as a result of doxorubicin treatment were also assessed using real time qPCR. Doxorubicin (1 μM) produced alterations in intracellular calcium signaling, including enhancing the sensitivity of MDA-MB-231 cells to ATP stimulation and prolonging the recovery time after store-operated calcium entry. Upregulation in mRNA levels of ORAI1, TRPC1, SERCA1, IP₃R2 and PMCA2 with doxorubicin 1 μM treatment was also observed. Doxorubicin treatment is associated with specific remodeling in calcium signaling in MDA-MB-231 cells, with associated changes in mRNA levels of specific calcium-regulating proteins.

A Novel Calcium-Mediated EMT Pathway Controlled by Lipids: An Opportunity for Prostate Cancer Adjuvant Therapy

The composition of periprostatic adipose tissue (PPAT) has been shown to play a role in prostate cancer (PCa) progression. We recently reported an inverse association between PCa aggressiveness and elevated PPAT linoleic acid (LA) and eicosapentaenoic acid (EPA) content. In the present study, we identified a new signaling pathway with a positive feedback loop between the epithelial-to-mesenchymal transition (EMT) transcription factor Zeb1 and the Ca²⁺-activated K⁺ channel SK3, which leads to an amplification of Ca²⁺ entry and cellular migration. Using in vitro experiments and ex vivo cultures of human PCa slices, we demonstrated that LA and EPA exert anticancer effects, by modulating Ca²⁺ entry, which was involved in Zeb1 regulation and cancer cellular migration. This functional approach using human prostate tumors highlights the clinical relevance of our observations, and may allow us to consider the possibility of targeting cancer spread by altering the lipid microenvironment.

MFAP5 promotes basal-like breast cancer progression by activating the EMT program

Purpose

Human basal-like breast cancer (BLBC) is an aggressive malignancy with poor prognosis. Since most current treatments are ineffective, there is an urgent need to identify therapeutic targets for BLBC. Microfibrillar-associated protein 5 (MFAP5) plays an important role in the integration of elastic microfibers and the regulation of endothelial cell behaviors. We previously demonstrated that MFAP5 was significantly overexpressed in BLBC tissues and associated with poor metastasis-free survival of patients with BLBC. However, the detailed role of MFAP5 in BLBC is unclear. Thereby, the current study aimed to investigate the underlying function of MFAP5 in BLBC.

Method

Functional analyses were conducted for the role of MFAP5 in BLBC in vitro and in vivo.

Results

Overexpression of MFAP5 resulted in a significant increase in the proliferation, migration, invasion and epithelial–mesenchymal transition (EMT) markers in BLBC in vitro and in vivo. In addition, other metastasis animal models by tail intravenous injection of BT20 cells further confirmed that MFAP5 overexpression promoted BLBC proliferation and BT20 cells metastasis. We found that the TGF-β or Notch inhibitor significantly reversed the tumorigenicity and metastasis of MFAP5-induced BLBC cells.

Conclusion

Our findings suggest that MFAP5 may promote EMT in BLBC metastasis via the TGF-β/Notch pathway.

Electronic supplementary material

The online version of this article (10.1186/s13578-019-0284-0) contains supplementary material, which is available to authorized users.

FUN14 domain-containing 1 promotes breast cancer proliferation and migration by activating calcium-NFATC1-BMI1 axis

BACKGROUND

FUN14 domain-containing 1 (FUNDC1), as a novel member of mitochondria-associated endoplasmic reticulum (ER) membranes associates with mitochondrial division and mitophagy. However, the expression profile and functional roles of FUNDC1 remain largely unclear in human cancer biology, including breast cancer (BC).

METHODS

Immunohistochemistry and western blot analysis were used to determine the expression of FUNDC1 and BMI1 polycomb ring finger oncogene (BMI1). CCK8, cell counting and transwell assays were used to analyze cell proliferation, migration and invasion, respectively. Luciferase reporter and chromatin immunoprecipitation (ChIP) assays were used to detect the transcriptional regulation of Nuclear factor of activated T-cells, cytoplasmic 1 (NFATC1). The prognostic merit of NFATC1 expression was assessed by Kaplan-Meier assay.

FINDINGS

Immunohistochemistry revealed strong immunostaining for FUNDC1 in cytoplasmic and nuclear membrane distribution in BC tissues as compared with normal breast epithelium. Kaplan-Meier survival analysis showed worse outcome for BC patients with high FUNDC1 expression. In vitro assay of gain- and loss-of-function of FUNDC1 suggested that FUNDC1 could stimulate BC cell proliferation, migration and invasion. Furthermore, elevated FUNDC1 level promoted Ca²⁺ cytosol influx from ER and extracellular, as well as NFATC1 nuclear translocation and activity. Nuclear NFATC1 bound to the BMI1 gene promoter and transcriptionally upregulated its expression. Notably, BMI1 overexpression could rescue the loss of function of FUNDC1. Co-expression of FUNDC1 and BMI1 in BC patients predicted worse prognosis than without either expression.

INTERPRETATION

FUNDC1 might promote BC progression by activating the Ca²⁺-NFATC1-BMI1 axis. This pathway may be promising for developing multiple targets for BC therapy.

STIM1 expression is associated with osteosarcoma cell survival

OBJECTIVE

To examine the role of store-operated calcium entry (SOCE) and stromal interaction molecule 1 (STIM1) in survival and migration of osteosarcoma cells and investigate what blockade of store-operated Ca2+ contributes to the regulation of osteosarcoma cells.

METHODS

First, we examined the expression levels of STIM1 in osteosarcoma cell lines by Western analysis and in tissue specimens by immunohistochemistry. Second, we investigated the effect of SOCE and STIM1 on osteosarcoma cell viability using MTS assays and on cell proliferation using colony formation. Third, we investigated the role of SOCE and STIM1 in cell migration using wound healing assays and Boyden chamber assays. Finally, we studied the effect of SOCE on the nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) activity by luciferase assays.

RESULTS

STIM1 was overexpressed in osteosarcoma cell lines and tissue specimens and was associated with poor survival of osteosarcoma patients. Also, inhibition of SOCE and STIM1 decreased the cell viability and migration of osteosarcoma cells. Furthermore, our results showed that blockade of store-operated Ca2+ channels involved down-regulation of NFATc1 in osteosarcoma cells.

CONCLUSIONS

STIM1 is essential for osteosarcoma cell functions, and STIM1 and Ca2+ entry pathway could be further explored as molecular targets in the treatment of osteosarcoma.

Store-Operated Ca2+ Entry in Breast Cancer Cells: Remodeling and Functional Role

Breast cancer is the most common type of cancer in women. It is a heterogeneous disease that ranges from the less undifferentiated luminal A to the more aggressive basal or triple negative breast cancer molecular subtype. Ca²⁺ influx from the extracellular medium, but more specifically store-operated Ca²⁺ entry (SOCE), has been reported to play an important role in tumorigenesis and the maintenance of a variety of cancer hallmarks, including cell migration, proliferation, invasion or epithelial to mesenchymal transition. Breast cancer cells remodel the expression and functional role of the molecular components of SOCE. This review focuses on the functional role and remodeling of SOCE in breast cancer cells. The current studies suggest the need to deepen our understanding of SOCE in the biology of the different breast cancer subtypes in order to develop new and specific therapeutic strategies.

Integration of Ca2+ signaling regulates the breast tumor cell response to simvastatin and doxorubicin

Recent studies have suggested that the lipid-lowering agent simvastatin holds great promise as a cancer therapeutic; it inhibits the growth of multiple tumors, including triple-negative breast cancer. Doxorubicin- and simvastatin-induced cytotoxicity has been associated with the modulation of Ca2+ signaling, but the underlying mechanisms remain incompletely understood. Here we identify how Ca2+ signaling regulates the breast tumor cell response to doxorubicin and simvastatin. These two drugs inhibit cell survival while increasing apoptosis in two human breast cancer cell lines and five primary breast tumor specimens through the modulation of Ca2+ signaling. Signal transduction and functional studies revealed that both simvastatin and doxorubicin trigger persistent cytosolic Ca2+ release, thereby stimulating the proapoptotic BIM pathway and mitochondrial Ca2+ overload, which are responsible for metabolic dysfunction and apoptosis induction. Simvastatin and doxorubicin suppress the prosurvival ERK1/2 pathway in a Ca2+-independent and Ca2+-dependent manner, respectively. In addition, reduction of the Ca2+ signal by chelation or pharmacological inhibition significantly prevents drug-mediated anticancer signaling. Unexpectedly, a scratch-wound assay indicated that these two drugs induce rapid cell migration, while inhibiting cell invasion and colony formation in a Ca2+-dependent manner. Further, the in vivo data for MDA-MB-231 xenografts demonstrate that upon chelation of Ca2+, the ability of both drugs to reduce the tumor burden was significantly reduced via caspase-3 deactivation. Our results establish a calcium-based mechanism as crucial for executing the cell death process triggered by simvastatin and doxorubicin, and suggest that combining simvastatin with doxorubicin may be an effective regimen for the treatment of breast cancer.

Identification of epigenetic modulators in human breast cancer by integrated analysis of DNA methylation and RNA-Seq data

Human tumors undergo massive changes in DNA methylation. Recent studies showed that site-specific methylation of CpG sites is determined by the DNA sequence context surrounding the CpG site, which alludes to a possible mechanism for site-specific aberrant DNA methylation in cancer through DNA-binding proteins. In this paper, DNA methylation data and RNA-Seq data of breast tumors and normal tissues in the database of The Cancer Genome Atlas (TCGA) were integrated with information of DNA motifs in seven databases to find DNA-binding proteins and their binding motifs that were involved in aberrant DNA methylation in breast cancer. A total of 42,850 differentially methylated regions (DMRs) that include 77,298 CpG sites were detected in breast cancer. One hundred eight DNA motifs were found to be enriched in DMRs, and 109 genes encoding proteins binding to these motifs were determined. Based on these motifs and genes, 63 methylation modulator genes were identified to regulate differentially methylated CpG sites in breast cancer. A network of these 63 modulator genes and 645 transcription factors was constructed, and 20 network modules were determined. A number of pathways and gene sets related to breast cancer were found to be enriched in these network modules. The 63 methylation modulator genes identified may play an important role in aberrant methylation of CpG sites in breast cancer. They may help to understand site-specific dysregulation of DNA methylation and provide epigenetic markers for breast cancer.

Calcium store refilling and STIM activation in STIM- and Orai-deficient cell lines

Mediated through the combined action of STIM proteins and Orai channels, store-operated Ca²⁺ entry (SOCE) functions ubiquitously among different cell types. The existence of multiple STIM and Orai genes has made it difficult to assign specific roles of each STIM and Orai homolog in mediating Ca²⁺ signals. Using CRISPR/Cas9 gene editing tools, we generated cells with both STIM or all three Orai homologs deleted and directly monitored store Ca²⁺ and Ca²⁺ signals. We found that unstimulated, SOCE null KO cells still retain 50~70% of ER Ca²⁺ stores of wildtype (wt) cells. After brief exposure to store-emptying conditions, acute refilling of ER Ca²⁺ stores was totally blocked in KO cells. However, after 24 h in culture, stores were eventually refilled. Thus, SOCE is critical for immediate refilling of ER Ca²⁺ but is dispensable for the maintenance of long-term ER Ca²⁺ homeostasis. Using the Orai null background triple Orai-KO cells, we examined the plasma membrane translocation properties of a series of truncated STIM1 variants. FRET analysis reveals that, even though PM tethering of STIM1 expedites the activation of STIM1 by facilitating its oligomerization, migration, and accumulation in ER-PM junctions, it is not required for the conformational switch, oligomerization, and clustering of STIM1. Even without overt puncta formation at ER-PM junctions, STIM1_1–491 and STIM1_1–666 could still rescue SOCE when expressed in STIM KO cells. Thus, ER-PM trapping and clustering of STIM molecules only facilitates the process of SOCE activation, but is not essential for the activation of Orai channels.

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.

Transcriptomic response of breast cancer cells to anacardic acid

Anacardic acid (AnAc), a potential dietary agent for preventing and treating breast cancer, inhibited the proliferation of estrogen receptor α (ERα) positive MCF-7 and MDA-MB-231 triple negative breast cancer cells. To characterize potential regulators of AnAc action, MCF-7 and MDA-MB-231 cells were treated for 6 h with purified AnAc 24:1n5 congener followed by next generation transcriptomic sequencing (RNA-seq) and network analysis. We reported that AnAc-differentially regulated miRNA transcriptomes in each cell line and now identify AnAc-regulated changes in mRNA and lncRNA transcript expression. In MCF-7 cells, 80 AnAc-responsive genes were identified, including lncRNA MIR22HG. More AnAc-responsive genes (886) were identified in MDA-MB-231 cells. Only six genes were commonly altered by AnAc in both cell lines: SCD, INSIG1, and TGM2 were decreased and PDK4, GPR176, and ZBT20 were increased. Modeling of AnAc-induced gene changes suggests that AnAc inhibits monounsaturated fatty acid biosynthesis in both cell lines and increases endoplasmic reticulum stress in MDA-MB-231 cells. Since modeling of downregulated genes implicated NFκB in MCF-7, we confirmed that AnAc inhibited TNFα-induced NFκB reporter activity in MCF-7 cells. These data identify new targets and pathways that may account for AnAc’s anti-proliferative and pro-apoptotic activity.

Store operated calcium entry is altered by the inhibition of receptors tyrosine kinase

SOCE (Store-Operated Calcium Entry) is the main mechanism by which external Ca²⁺ enters into non-excitable cells after endoplasmic reticulum emptying. It is implicated in several processes such as proliferation and migration. Alterations in SOCE could initiate or support the development of hallmarks of cancer. In this project, we showed that disruption of the EGFR/ErbB2-dependent signalling by lapatinib and CP-724714, two inhibitors of the receptor tyrosine kinase (RTK), dramatically reduced the amplitude of the SOCE in breast cancer cells. LY294002 and MK2206, two inhibitors of the PI3K/Akt pathway, mimicked the effect of the inhibition of EGFR/ErbB2. In contrast, inhibitors of the MAPK pathway had no effect on SOCE. The involvement of EGFR/ErbB2 receptors and the PI3K/Akt pathway in the regulation of SOCE was confirmed in other cell lines derived from various cancer types. All these results showed that SOCE is positively regulated by the PI3K/Akt pathway and that this effect may be suppressed by the inhibition of the upstream RTKs. Inhibition of SOCE might therefore contribute to the anticancer effects of RTK inhibitors.

The current status and perspectives regarding the clinical implication of intracellular calcium in breast cancer

Calcium ions (Ca²⁺ ) act as second messengers in intracellular signaling. Ca²⁺ pumps, channels, sensors, and calcium binding proteins, regulate the concentrations of intracellular Ca²⁺ as a key regulator of important cellular processes such as gene expression, proliferation, differentiation, DNA repair, apoptosis, metastasis, and hormone secretion. Intracellular Ca²⁺ also influences the functions of several organelles, that include: the endoplasmic reticulum, mitochondria, the Golgi, and cell membrane both in normal and breast cancer cells. In breast cancer, the disruption of intracellular: Ca²⁺ homeostasis may cause tumor progression by affecting key factors/pathways including phospholipase C (PLC), inositol 1,4,5-trisphosphate (IP3), calmodulin (CaM), nuclear factor of activated T-cells (NFAT), calpain, calmodulin-dependent protein kinase II (CaMKII), mitogen-activated protein kinase (MAPK), epithelial-mesenchymal transition (EMT), vascular endothelial growth factor (VEGF), poly (ADP-Ribose) polymerase-1 (PARP1), estrogen, and estrogen receptor. Because the foregoing molecules play crucial roles in breast cancer, the factors/pathways influencing intracellular Ca²⁺ concentrations are putative targets for cancer treatment, using drugs such as Mephebrindole, Tilapia piscidin 4, Nifetepimine, Paricalcitol, and Prednisolone. We have explored the factors/pathways which are related to breast cancer and Ca²⁺ homeostasis and signaling in this review, and also discussed their potential as biomarkers for breast cancer staging, prognosis, and therapy.

Abnormal expression of TGF-beta type II receptor isoforms contributes to acute myeloid leukemia

Altered transforming growth factor-beta (TGF-β) signaling has been implicated in the pathogenesis of leukemia. Although TGF-β type II receptor (TβRII) isoforms have been isolated from human leukemia cells, their expression patterns and functions of these variants are unclear. In this study, we determined that two TβRII isoforms (TβRII and TβRII-B) are abnormally expressed in leukemic cells, as compared to normal hematopoietic cells. TβRII-B, but not TβRII, was found to promote cell cycle arrest, apoptosis, and differentiation of leukemic cells. TβRII-B also enhanced TGF-β1 binding and downstream signaling and reduced tumorigenicity in vivo. By contrast, TβRII blocked all-trans retinoic acid-induced differentiation through inhibition of TβRII-B. Overall survival was significantly lower in acute myeloid leukemia (AML) patients with high compared to low TβRII expression. Thus, whereas TβRII-B is a potent inducer of cell cycle arrest, apoptosis, and differentiation, higher TβRII expression correlates with poor clinical prognosis in AML.

TGF-β-Dependent Growth Arrest and Cell Migration in Benign and Malignant Breast Epithelial Cells Are Antagonistically Controlled by Rac1 and Rac1b

Despite improvements in diagnosis and treatment, breast cancer is still the most common cancer type among non-smoking females. TGF-β can inhibit breast cancer development by inducing cell cycle arrest in both, cancer cells and, as part of a senescence program in normal human mammary epithelial cells (HMEC). Moreover, TGF-β also drives cell migration and invasion, in part through the small GTPases Rac1 and Rac1b. Depletion of Rac1b or Rac1 and Rac1b in MDA-MB-231 or MDA-MB-435s breast cancer cells by RNA interference enhanced or suppressed, respectively, TGF-β1-induced migration/invasion. Rac1b depletion in MDA-MB-231 cells also increased TGF-β-induced p21^WAF1 expression and ERK1/2 phosphorylation. Senescent HMEC (P15/P16), when compared to their non-senescent counterparts (P11/P12), presented with dramatically increased migratory activity. These effects were paralleled by elevated expression of genes associated with TGF-β signaling and metastasis, downregulated Rac1b, and upregulated Rac1. Our data suggest that acquisition of a motile phenotype in HMEC resulted from enhanced autocrine TGF-β signaling, invasion/metastasis-associated gene expression, and a shift in the ratio of antimigratory Rac1b to promigratory Rac1. We conclude that although enhanced TGF-β signaling is considered antioncogenic in HMEC by suppressing oncogene-induced transformation, this occurs at the expense of a higher migration and invasion potential.

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.

CaMKIIδ meditates phenylephrine induced cardiomyocyte hypertrophy through store-operated Ca2+ entry

Evidence suggests that store-operated Ca2+ entry (SOCE) is involved in the hypertrophy of cardiomyocytes. The signaling mechanisms of SOCE contributing to cardiac hypertrophy following phenylephrine (PE) stimulation are not fully understood. Ca²⁺/calmodulin-dependent protein kinase II δ (CaMKIIδ) plays an important role in regulating intracellular Ca²⁺ hemostasis and function in the cardimyocytes. This study is aimed to determine the role of CaMKIIδ in regulating the PE-induced myocardial hypertrophy and the associated molecular signaling mechanisms. We used primary cultures of neonatal cardimyocytes isolated from the left ventricle of Sprague Dawley rats to investigate the effects of CaMKIIδ on myocardial hypertrophy and intracellular Ca²⁺ mobilization. We found that the expression of CaMKIIδ was enhanced in PE-induced hypertrophic cardiomyocytes. CaMKIIδ siRNA, CaMKII inhibitor KN93, and SOCE blocker BTP2 attenuated the increase in the expression of CaMKIIδ and normalized the hypertrophic markers, atrial natriuretic peptide and brain natriuretic peptide, and size of cardiomyocytes induced by PE stimulation. The protein level of stromal interaction molecule 1 and Orai1, the essential components of the SOCE, is also enhanced in hypertrophic cardiomyocytes, which were normalized by CaMKIIδ siRNA and KN93 treatment. Hypertrophic cardiomyocytes showed an increase in the peak of Ca²⁺ transient following store depletion, which was inhibited by SOCE blocker BTP2, CaMKIIδ siRNA, and KN93. The Ca²⁺ currents through Ca²⁺ release-activated Ca²⁺ channels were increased in PE-treated cardiomyocytes and were attenuated by CaMKIIδ siRNA and KN93. These data indicate that PE-induced myocardial hypertrophy requires a complex signaling pathway that involves activation of both CaMKIIδ and SOCE. In conclusion, these studies reveal that up-regulation of CaMKIIδ may contribute to the PE-induced myocardial hypertrophy through the activation of SOCE expressed in the cardiomyocytes.