TRPM8 promotes aggressiveness of breast cancer cells by regulating EMT via activating AKT/GSK-3β pathway

TRPM channels in human cancers: regulatory mechanism and therapeutic prospects

The transient receptor potential melastatin (TRPM) channel family has been previously implicated in various diseases, including those related to temperature sensing, cardiovascular health, and neurodegeneration. Nowadays, increasing evidence indicates that TRPM family members also play significant roles in various types of cancers, exhibiting both pro- and anti-tumorigenic functions. They are involved in tumor cell proliferation, survival, invasion, and metastasis, serving as potential diagnostic and prognostic biomarkers for cancer. This paper begins by describing the structure and physiological functions of the TRPM family members. It then outlines their roles in several common malignancies, including pancreatic, prostate, colorectal, breast, brain cancer, and melanoma. Subsequently, we focused on investigating the specific mechanisms by which TRPM family members are involved in tumorigenesis and development from both the tumor microenvironment (TME) and intracellular signaling. TRPM channels not only transmit signals from the TME to regulate tumor cell functions, but also mediate extracellular matrix remodeling, which is conducive to the malignant transformation of tumor cells. Importantly, TRPM channels depend on the regulation of the inflow of various ions in cells, and participate in key signaling pathways involved in tumor progression, such as Wnt/β-catenin, MAPK, PI3K/AKT, p53, and autophagy. Finally, we summarize the current strategies and challenges of targeting TRPM channels in tumor treatment, and discuss the feasibility of combining targeted TRPM channel drugs with cancer immunotherapy.

TRPM8 overexpression suppresses hepatocellular carcinoma progression and improves survival by modulating the RTP3/STAT3 pathway

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is a malignant tumour associated with high morbidity and mortality rates worldwide. Recently, TRPM8 was reported to play an important role in tumour progression. However, the precise role of TRPM8 in HCC remains unclear. In this study, we explored the expression levels, molecular functions and underlying mechanisms of TRPM8 in HCC.

METHODS

Tissue samples were used to analyse the expression of TRPM8 to assess its diagnostic value for prognosis. Cell Counting Kit-8, EdU and colony formation assays were performed to evaluate the effects of TRPM8 on cell proliferation, whereas the Transwell assay was used to assess cell migration and invasion. The role of TRPM8 in vivo was evaluated using a mouse subcutaneous xenograft tumour model. We performed PPI network analyses to understand the possible mechanisms of TRPM8 action.

RESULTS

TRPM8 expression was decreased in HCC tissues and was correlated with histological grade and poor patient prognosis. Functionally, TRPM8 repressed the proliferation and metastasis of HCC cells both in vitro and in vivo by modulating the RTP3/STAT3 signalling pathway.

CONCLUSION

Our findings underscore the critical role of the TRPM8-RTP3-STAT3 axis in maintaining the malignant progression of HCC. Moreover, our study demonstrates that AD80 is involved in anti-tumour processes by upregulating the expression of TRPM8.

Targeting TRPs in autophagy regulation and human diseases

Transient receptor potential channels (TRPs) are widely recognized as a group of ion channels involved in various sensory perceptions, such as temperature, taste, pressure, and vision. While macroautophagy (hereafter referred to as autophagy) is primarily regulated by core machinery, the ion exchange mediated by TRPs between intracellular and extracellular compartments, as well as within organelles and the cytoplasm, plays a crucial role in autophagy regulation as an important signaling transduction mechanism. Moreover, certain TRPs can directly interact with autophagy regulatory proteins to participate in autophagy regulation. In this article, we provide an in-depth review of the current understanding of the regulatory mechanisms of autophagy, with a specific focus on TRPs. Furthermore, we highlight the potential prospects for drug development targeting TRPs in autophagy for the treatment of human diseases.

Pathological mechanisms of cold and mechanical stress in modulating cancer progression

Environmental temperature and cellular mechanical force are the inherent factors that participate in various biological processes and regulate cancer progress, which have been hot topics worldwide. They occupy a dominant part in the cancer tissues through different approaches. However, extensive investigation regarding pathological mechanisms in the carcinogenic field. After research, we found cold stress via two means to manipulate tumors: neuroscience and mechanically sensitive ion channels (MICHs) such as TRP families to regulate the physiological and pathological activities. Excessive cold stimulation mediated neuroscience acting on every cancer stage through the hypothalamus-pituitary-adrenocorticoid (HPA) to reach the target organs. Comparatively speaking, mechanical force via Piezo of MICHs controls cancer development. The progression of cancer depends on the internal activation of proto-oncogenes and the external tumorigenic factors; the above two means eventually lead to genetic disorders at the molecular level. This review summarizes the interaction of bidirectional communication between them and the tumor. It covers the main processes from cytoplasm to nucleus related to metastasis cascade and tumor immune escape.

The Role of TRPM7 in Oncogenesis

This review summarizes the current understanding of the role of transient receptor potential melastatin-subfamily member 7 (TRPM7) channels in the pathophysiology of neoplastic diseases. The TRPM family represents the largest and most diverse group in the TRP superfamily. Its subtypes are expressed in virtually all human organs playing a central role in (patho)physiological events. The TRPM7 protein (along with TRPM2 and TRPM6) is unique in that it has kinase activity in addition to the channel function. Numerous studies demonstrate the role of TRPM7 chanzyme in tumorigenesis and in other tumor hallmarks such as proliferation, migration, invasion and metastasis. Here we provide an up-to-date overview about the possible role of TRMP7 in a broad range of malignancies such as tumors of the nervous system, head and neck cancers, malignant neoplasms of the upper gastrointestinal tract, colorectal carcinoma, lung cancer, neoplasms of the urinary system, breast cancer, malignant tumors of the female reproductive organs, prostate cancer and other neoplastic pathologies. Experimental data show that the increased expression and/or function of TRPM7 are observed in most malignant tumor types. Thus, TRPM7 chanzyme may be a promising target in tumor therapy.

TRP Channels in Cancer: Signaling Mechanisms and Translational Approaches

Ion channels play a crucial role in a wide range of biological processes, including cell cycle regulation and cancer progression. In particular, the transient receptor potential (TRP) family of channels has emerged as a promising therapeutic target due to its involvement in several stages of cancer development and dissemination. TRP channels are expressed in a large variety of cells and tissues, and by increasing cation intracellular concentration, they monitor mechanical, thermal, and chemical stimuli under physiological and pathological conditions. Some members of the TRP superfamily, namely vanilloid (TRPV), canonical (TRPC), melastatin (TRPM), and ankyrin (TRPA), have been investigated in different types of cancer, including breast, prostate, lung, and colorectal cancer. TRP channels are involved in processes such as cell proliferation, migration, invasion, angiogenesis, and drug resistance, all related to cancer progression. Some TRP channels have been mechanistically associated with the signaling of cancer pain. Understanding the cellular and molecular mechanisms by which TRP channels influence cancer provides new opportunities for the development of targeted therapeutic strategies. Selective inhibitors of TRP channels are under initial scrutiny in experimental animals as potential anti-cancer agents. In-depth knowledge of these channels and their regulatory mechanisms may lead to new therapeutic strategies for cancer treatment, providing new perspectives for the development of effective targeted therapies.

Calcium signal modulation in breast cancer aggressiveness

Breast cancer (BC) is the second most common cancer and cause of death in women. The aggressive subtypes including triple negative types (TNBCs) show a resistance to chemotherapy, impaired immune system, and a worse prognosis. From a histological point of view, TNBCs are deficient in oestrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2⁺) expression. Many studies reported an alteration in the expression of calcium channels, calcium binding proteins and pumps in BC that promote proliferation, survival, resistance to chemotherapy, and metastasis. Moreover, Ca²⁺ signal remodeling and calcium transporters expression have been associated to TNBCs and HER2⁺ BC subtypes. This review provides insight into the underlying alteration of the expression of calcium-permeable channels, pumps, and calcium dependent proteins and how this alteration plays an important role in promoting metastasis, metabolic switching, inflammation, and escape to chemotherapy treatment and immune surveillance in aggressive BC including TNBCs models and highly metastatic BC tumors.

Intersection between calcium signalling and epithelial-mesenchymal plasticity in the context of cancer

Epithelial-mesenchymal transition (EMT) is a form of cellular phenotypic plasticity and is considered a crucial step in the progression of many cancers. The calcium ion (Ca²⁺) acts as a ubiquitous second messenger and is implicated in many cellular processes, including cell death, migration, invasion and more recently EMT. Throughout this review, the complex interplay between Ca²⁺ signalling and EMT will be explored. An overview of the Ca²⁺ pathways that are remodelled as a consequence of EMT is provided and the role of Ca²⁺ signalling in regulating EMT and its significance is considered. Ca²⁺ signalling pathways may represent a therapeutic opportunity to regulate EMT. However, as will be described in this review, the complexity of these signalling pathways represents significant challenges that must be considered if Ca²⁺ signalling is to be manipulated with the aim of therapeutic intervention in cancer.

'Toxic Masculinity': What Is Known about the Role of Androgen Receptors in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC), the most prevalent cancer in the head and neck region, develops from the mucosal epithelium of the upper aerodigestive tract. Its development directly correlates with alcohol and/or tobacco consumption and infection with human papillomavirus. Interestingly, the relative risk for HNSCC is up to five times higher in males, so it is considered that the endocrine microenvironment is another risk factor. A gender-specific risk for HNSCC suggests either the existence of specific risk factors that affect only males or that females have defensive hormonal and metabolic features. In this review, we summarized the current knowledge about the role of both nuclear and membrane androgen receptors (nAR and mARs, respectively) in HNSCC. As expected, the significance of nAR is much better known; it was shown that increased nAR expression was observed in HNSCC, while treatment with dihydrotestosterone increased proliferation, migration, and invasion of HNSCC cells. For only three out of five currently known mARs-TRPM8, CaV1.2, and OXER1-it was shown either their increased expression in various types of HNSCC or that their increased activity enhanced the migration and invasion of HNSCC cells. The primary treatments for HNSCC are surgery and radiotherapy, but targeted immunotherapies are on the rise. On the other hand, given the evidence of elevated nAR expression in HNSCC, this receptor represents a potential target for antiandrogen therapy. Moreover, there is still plenty of room for further examination of mARs' role in HNSCC diagnosis, prognosis, and treatment.

On the modulation of TRPM channels: Current perspectives and anticancer therapeutic implications

The transient melastatin receptor potential (TRPM) ion channel subfamily functions as cellular sensors and transducers of critical biological signal pathways by regulating ion homeostasis. Some members of TRPM have been cloned from cancerous tissues, and their abnormal expressions in various solid malignancies have been correlated with cancer cell growth, survival, or death. Recent evidence also highlights the mechanisms underlying the role of TRPMs in tumor epithelial-mesenchymal transition (EMT), autophagy, and cancer metabolic reprogramming. These implications support TRPM channels as potential molecular targets and their modulation as an innovative therapeutic approach against cancer. Here, we discuss the general characteristics of the different TRPMs, focusing on current knowledge about the connection between TRPM channels and critical features of cancer. We also cover TRPM modulators used as pharmaceutical tools in biological trials and an indication of the only clinical trial with a TRPM modulator about cancer. To conclude, the authors describe the prospects for TRPM channels in oncology.

The role of transient receptor potential channels in metastasis

Metastasis is the hallmark of failed tumor treatment and is typically associated with death due to cancer. Transient receptor potential (TRP) channels affect changes in intracellular calcium concentrations and participate at every stage of metastasis. Further, they increase the migratory ability of tumor cells, promote angiogenesis, regulate immune function, and promote the growth of tumor cells through changes in gene expression and function. In this review, we explore the potential mechanisms of action of TRP channels, summarize their role in tumor metastasis, compile inhibitors of TRP channels relevant in tumors, and discuss current challenges in research on TRP channels involved in tumor metastasis.

Therapeutic potential of TRPM8 channels in cancer treatment

Cancer is a multifactorial process associated with changes in signaling pathways leading to cell cycle variations and gene expression. The transient receptor potential melastatin 8 (TRPM8) channel is a non-selective cation channel expressed in neuronal and non-neuronal tissues, where it is involved in several processes, including thermosensation, differentiation, and migration. Cancer is a multifactorial process associated with changes in signaling pathways leading to variations in cell cycle and gene expression. Interestingly, it has been shown that TRPM8 channels also participate in physiological processes related to cancer, such as proliferation, survival, and invasion. For instance, TRPM8 channels have an important role in the diagnosis, prognosis, and treatment of prostate cancer. In addition, it has been reported that TRPM8 channels are involved in the progress of pancreatic, breast, bladder, colon, gastric, and skin cancers, glioblastoma, and neuroblastoma. In this review, we summarize the current knowledge on the role of TRPM8 channels in cancer progression. We also discuss the therapeutic potential of TRPM8 in carcinogenesis, which has been proposed as a molecular target for cancer therapy.

New Frontiers on ER Stress Modulation: Are TRP Channels the Leading Actors?

The endoplasmic reticulum (ER) is a dynamic structure, playing multiple roles including calcium storage, protein synthesis and lipid metabolism. During cellular stress, variations in ER homeostasis and its functioning occur. This condition is referred as ER stress and generates a cascade of signaling events termed unfolded protein response (UPR), activated as adaptative response to mitigate the ER stress condition. In this regard, calcium levels play a pivotal role in ER homeostasis and therefore in cell fate regulation since calcium signaling is implicated in a plethora of physiological processes, but also in disease conditions such as neurodegeneration, cancer and metabolic disorders. A large body of emerging evidence highlighted the functional role of TRP channels and their ability to promote cell survival or death depending on endoplasmic reticulum stress resolution, making them an attractive target. Thus, in this review we focused on the TRP channels' correlation to UPR-mediated ER stress in disease pathogenesis, providing an overview of their implication in the activation of this cellular response.

Nebivolol as a Potent TRPM8 Channel Blocker: A Drug-Screening Approach through Automated Patch Clamping and Ligand-Based Virtual Screening

Transient Receptor Potential Melastatin 8 (TRPM8) from the melastatin TRP channel subfamily is a non-selective Ca²⁺-permeable ion channel with multimodal gating which can be activated by low temperatures and cooling compounds, such as menthol and icilin. Different conditions such as neuropathic pain, cancer, overactive bladder syndrome, migraine, and chronic cough have been linked to the TRPM8 mode of action. Despite the several potent natural and synthetic inhibitors of TRPM8 that have been identified, none of them have been approved for clinical use. The aim of this study was to discover novel blocking TRPM8 agents using automated patch clamp electrophysiology combined with a ligand-based virtual screening based on the SwissSimilarity platform. Among the compounds we have tested, nebivolol and carvedilol exhibited the greatest inhibitory effect, with an IC₅₀ of 0.97 ± 0.15 µM and 9.1 ± 0.6 µM, respectively. This study therefore provides possible candidates for future drug repurposing and suggests promising lead compounds for further optimization as inhibitors of the TRPM8 ion channel.

AMTB, a TRPM8 antagonist, suppresses growth and metastasis of osteosarcoma through repressing the TGFβ signaling pathway

Since its first identification in prostate cancers and prostate tissues, transient receptor potential melastatin-subfamily member 8 (TRPM8) is subsequently found to be overexpressed in a wide range of cancers and is shown to be implicated in tumorigenesis and tumor progression. Here, we used N-(3-aminopropyl)-2-[(3-methylphenyl) methoxy] -N-(2-thienylmethyl) benzamide hydrochloride (AMTB), a specific TRPM8 antagonist, to explore its antitumoral effect on osteosarcoma. We find that AMTB suppresses osteosarcoma cell proliferation, metastasis and induces cellular apoptosis. Xenograft model in nude mice experiments also define that AMTB can increase the sensitivity of tumor cells to cisplatin, the cytotoxic chemotherapeutic regimens in treating osteosarcoma. Molecularly, AMTB specifically antagonizes TRPM8 which is upregulated in osteosarcoma and its expression level in osteosarcoma tissues is negatively related to patients’ prognosis. Finally, RNA sequencing analysis was performed to explore the mechanism underlying the antitumoral effect of AMTB on osteosarcoma cells and the results prove that AMTB suppresses the Transforming Growth Factor β (TGFβ) signaling pathway. Our study provides evidence that TRPM8 could be a potential therapeutic target and AMTB can suppress growth and metastasis of osteosarcoma cells through repressing the TGFβ signaling pathway and increase the sensitivity of tumor cells to cisplatin.

Bioelectric Dysregulation in Cancer Initiation, Promotion, and Progression

Cancer is primarily a disease of dysregulation – both at the genetic level and at the tissue organization level. One way that tissue organization is dysregulated is by changes in the bioelectric regulation of cell signaling pathways. At the basis of bioelectricity lies the cellular membrane potential or V_mem, an intrinsic property associated with any cell. The bioelectric state of cancer cells is different from that of healthy cells, causing a disruption in the cellular signaling pathways. This disruption or dysregulation affects all three processes of carcinogenesis – initiation, promotion, and progression. Another mechanism that facilitates the homeostasis of cell signaling pathways is the production of extracellular vesicles (EVs) by cells. EVs also play a role in carcinogenesis by mediating cellular communication within the tumor microenvironment (TME). Furthermore, the production and release of EVs is altered in cancer. To this end, the change in cell electrical state and in EV production are responsible for the bioelectric dysregulation which occurs during cancer. This paper reviews the bioelectric dysregulation associated with carcinogenesis, including the TME and metastasis. We also look at the major ion channels associated with cancer and current technologies and tools used to detect and manipulate bioelectric properties of cells.

In Vitro and In Vivo Pharmacological Characterization of a Novel TRPM8 Inhibitor Chemotype Identified by Small-Scale Preclinical Screening

Transient receptor potential melastatin type 8 (TRPM8) is a target for the treatment of different physio-pathological processes. While TRPM8 antagonists are reported as potential drugs for pain, cancer, and inflammation, to date only a limited number of chemotypes have been investigated and thus a limited number of compounds have reached clinical trials. Hence there is high value in searching for new TRPM8 antagonistic to broaden clues to structure-activity relationships, improve pharmacological properties and explore underlying molecular mechanisms. To address this, the EDASA Scientific in-house molecular library has been screened in silico, leading to identifying twenty-one potentially antagonist compounds of TRPM8. Calcium fluorometric assays were used to validate the in-silico hypothesis and assess compound selectivity. Four compounds were identified as selective TRPM8 antagonists, of which two were dual-acting TRPM8/TRPV1 modulators. The most potent TRPM8 antagonists (BB 0322703 and BB 0322720) underwent molecular modelling studies to highlight key structural features responsible for drug-protein interaction. The two compounds were also investigated by patch-clamp assays, confirming low micromolar potencies. The most potent compound (BB 0322703, IC50 1.25 ± 0.26 μM) was then profiled in vivo in a cold allodinya model, showing pharmacological efficacy at 30 μM dose. The new chemotypes identified showed remarkable pharmacological properties paving the way to further investigations for drug discovery and pharmacological purposes.

Cannabis with breast cancer treatment: propitious or pernicious?

Cannabis has been used for various medicinal applications including, but not limited to, cancer: most commonly to treat chemotherapy-associated side effects. Cannabis is often used for its palliative effects in the form of purified cannabinoids, or as extracts. This study was conducted using two breast cancer cell lines and aimed to evaluate potential anti-proliferative "intra-entourage effects" between purified phytocannabinoids resembling the THC and CBD ratios of medicinal and recreational cannabis strains, as well as to investigate potential "inter-entourage effects" between the different ratios and the phytochemicals found in a Cannabis sativa extract. This study also aimed to evaluate the potential interaction between cannabinoids and chemotherapeutic agents. The data identified an intra-entourage effect present in the MCF-7 cells when treated with a recreational, but not a medicinal, cannabis formulation. This effect may be due to THC partially exerting its anti-proliferative effects through the estrogen receptor (ER), present in the MCF-7 cell line. Little to no intra-entourage effects were observed in the MDA-MB-231 cell line and no inter-entourage effects were observed in either cell line. The simultaneous treatment of the MCF-7 cell line with various cannabinoid formulations and the common breast cancer treatment, tamoxifen, resulted in the diminished anti-proliferative activity of tamoxifen, an effect that was more evident when combined with recreational cannabis formulations. Since cannabis is commonly used in palliative care to treat chemotherapy-associated side effects, further research is required to investigate the potential interference of various cannabis formulations to ensure that the efficacy of chemotherapeutic agents is not compromised.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03102-1.

Diverse role of androgen action in human breast cancer

Breast cancer is a hormone-dependent cancer, and sex steroids play a pivotal role in breast cancer progression. Estrogens are strongly associated with breast cancers, and the estrogen receptor (estrogen receptor α; ERα) is expressed in 70-80% of human breast carcinoma tissues. Although antiestrogen therapies (endocrine therapies) have significantly improved clinical outcomes in ERα-positive breast cancer patients, some patients experience recurrence after treatment. In addition, patients with breast carcinoma lacking ERα expression do not benefit from endocrine therapy. The androgen receptor (AR) is also expressed in >70% of breast carcinoma tissues. Growing evidence supports this novel therapeutic target for the treatment of triple-negative breast cancers that lack ERα, progesterone receptor, and human EGF receptor 2, and ERα-positive breast cancers, which are resistant to conventional endocrine therapy. However, the clinical significance of AR expression is still controversial and the biological function of androgens in breast cancers is unclear. In this review, we focus on the recent findings concerning androgen action in breast cancers and the contributions of androgens to improved breast cancer therapy.

Modulators of TRPM7 and its potential as a drug target for brain tumours

TRPM7 is a non-selective divalent cation channel with an alpha-kinase domain. Corresponding with its broad expression, TRPM7 has a role in a wide range of cell functions, including proliferation, migration, and survival. Growing evidence shows that TRPM7 is also aberrantly expressed in various cancers, including brain cancers. Because ion channels have widespread tissue distribution and result in extensive physiological consequences when dysfunctional, these proteins can be compelling drug targets. In fact, ion channels comprise the third-largest drug target type, following enzymes and receptors. Literature has shown that suppression of TRPM7 results in inhibition of migration, invasion, and proliferation in several human brain tumours. Therefore, TRPM7 presents a potential target for therapeutic brain tumour interventions. This article reviews current literature on TRPM7 as a potential drug target in the context of brain tumours and provides an overview of various selective and non-selective modulators of the channel relevant to pharmacology, oncology, and ion channel function.

Molecular Characterization of Membrane Steroid Receptors in Hormone-Sensitive Cancers

Cancer is one of the most common causes of death worldwide, and its development is a result of the complex interaction of genetic factors, environmental cues, and aging. Hormone-sensitive cancers depend on the action of one or more hormones for their development and progression. Sex steroids and corticosteroids can regulate different physiological functions, including metabolism, growth, and proliferation, through their interaction with specific nuclear receptors, that can transcriptionally regulate target genes via their genomic actions. Therefore, interference with hormones’ activities, e.g., deregulation of their production and downstream pathways or the exposition to exogenous hormone-active substances such as endocrine-disrupting chemicals (EDCs), can affect the regulation of their correlated pathways and trigger the neoplastic transformation. Although nuclear receptors account for most hormone-related biologic effects and their slow genomic responses are well-studied, less-known membrane receptors are emerging for their ability to mediate steroid hormones effects through the activation of rapid non-genomic responses also involved in the development of hormone-sensitive cancers. This review aims to collect pre-clinical and clinical data on these extranuclear receptors not only to draw attention to their emerging role in cancer development and progression but also to highlight their dual role as tumor microenvironment players and potential candidate drug targets.

Transient Receptor Potential (TRP) Ion Channels Involved in Malignant Glioma Cell Death and Therapeutic Perspectives

Among the most biologically, thus clinically, aggressive primary brain tumors are found malignant gliomas. Despite recent advances in adjuvant therapies, which include targeted and immunotherapies, after surgery and radio/chemotherapy, the tumor is recurrent and always lethal. Malignant gliomas also contain a pool of initiating stem cells that are highly invasive and resistant to conventional treatment. Ion channels and transporters are markedly involved in cancer cell biology, including glioma cell biology. Transient receptor potential (TRP) ion channels are calcium-permeable channels implicated in Ca²⁺ changes in multiple cellular compartments by modulating the driving force for Ca²⁺ entry. Recent scientific reports have shown that these channels contribute to the increase in glioblastoma aggressiveness, with glioblastoma representing the ultimate level of glioma malignancy. The current review focuses on each type of TRP ion channel potentially involved in malignant glioma cell death, with the ultimate goal of identifying new therapeutic targets to clinically combat malignant gliomas. It thus appears that cannabidiol targeting the TRPV2 type could be such a potential target.

Transient Receptor Potential Channels in the Epithelial-to-Mesenchymal Transition

The epithelial-to-mesenchymal transition (EMT) is a strictly regulated process that is indispensable for normal development, but it can result in fibrosis and cancer progression. It encompasses a complete alteration of the cellular transcriptomic profile, promoting the expression of genes involved in cellular migration, invasion and proliferation. Extracellular signaling factors driving the EMT process require secondary messengers to convey their effects to their targets. Due to its remarkable properties, calcium represents an ideal candidate to translate molecular messages from receptor to effector. Therefore, calcium-permeable ion channels that facilitate the influx of extracellular calcium into the cytosol can exert major influences on cellular phenotype. Transient receptor potential (TRP) channels represent a superfamily of non-selective cation channels that decode physical and chemical stimuli into cellular behavior. Their role as cellular sensors renders them interesting proteins to study in the context of phenotypic transitions, such as EMT. In this review, we elaborate on the current knowledge regarding TRP channel expression and activity in cellular phenotype and EMT.

TRP Channels Interactome as a Novel Therapeutic Target in Breast Cancer

Breast cancer is one of the most frequent cancer types worldwide and the first cause of cancer-related deaths in women. Although significant therapeutic advances have been achieved with drugs such as tamoxifen and trastuzumab, breast cancer still caused 627,000 deaths in 2018. Since cancer is a multifactorial disease, it has become necessary to develop new molecular therapies that can target several relevant cellular processes at once. Ion channels are versatile regulators of several physiological- and pathophysiological-related mechanisms, including cancer-relevant processes such as tumor progression, apoptosis inhibition, proliferation, migration, invasion, and chemoresistance. Ion channels are the main regulators of cellular functions, conducting ions selectively through a pore-forming structure located in the plasma membrane, protein–protein interactions one of their main regulatory mechanisms. Among the different ion channel families, the Transient Receptor Potential (TRP) family stands out in the context of breast cancer since several members have been proposed as prognostic markers in this pathology. However, only a few approaches exist to block their specific activity during tumoral progress. In this article, we describe several TRP channels that have been involved in breast cancer progress with a particular focus on their binding partners that have also been described as drivers of breast cancer progression. Here, we propose disrupting these interactions as attractive and potential new therapeutic targets for treating this neoplastic disease.

Involvement of TRPM8 Channel in Radiation-Induced DNA Damage Repair Mechanism Contributing to Radioresistance of B16 Melanoma

Radiation is an effective cancer treatment, but cancer cells can acquire radioresistance, which is associated with increased DNA damage response and enhanced proliferative capacity, and therefore, it is important to understand the intracellular biochemical responses to γ-irradiation. The transient receptor potential melastatin 8 (TRPM8) channel plays roles in the development and progression of tumors, but it is unclear whether it is involved in the DNA damage response induced by γ-irradiation. Here, we show that a TRPM8 channel inhibitor suppresses the DNA damage response (phosphorylated histone variant H2AX-p53-binding protein 1 (γH2AX-53BP1) focus formation) and colony formation of B16 melanoma cells. Furthermore, the TRPM8 channel-specific agonist WS-12 enhanced the DNA damage response and increased the survival fraction after γ-irradiation. We found that the TRPM8 channel inhibitor enhanced G₂/M phase arrest after γ-irradiation. Phosphorylation of ataxia telangiectasia mutated and p53, which both contribute to the DNA damage response was also suppressed after γ-irradiation. In addition, the TRPM8 channel inhibitor enhanced the γ-irradiation-induced suppression of tumor growth in vivo. We conclude that the TRPM8 channel is involved in radiation-induced DNA damage repair and contributes to the radioresistance of B16 melanoma cells. TRPM8 channel inhibitors might be clinically useful as radiosensitizers to enhance radiation therapy of melanoma.

The epithelial sodium channel has a role in breast cancer cell proliferation

PURPOSE

Breast cancer is the most common cancer affecting women worldwide with half a million associated deaths annually. Despite a huge global effort, the pathways of breast cancer progression are not fully elucidated. Ion channels have recently emerged as novel regulators of cancer cell proliferation and metastasis. The epithelial sodium channel, ENaC, made up of α, β and γ subunits is well known for its role in Na⁺ reabsorption in epithelia, but a number of novel roles for ENaC have been described, including potential roles in cancer. A role for ENaC in breast cancer, however, has yet to be described. Therefore, the effects of ENaC level and activity on breast cancer proliferation were investigated.

METHODS

Through the publicly available SCAN-B dataset associations between αENaC mRNA expression and breast cancer subtypes, proliferation markers and epithelial-mesenchymal transition markers (EMT) were assessed. αENaC expression, through overexpression or siRNA-mediated knockdown, and activity, through the ENaC-specific inhibitor amiloride, were altered in MCF7, T47D, BT549, and MDAMB231 breast cancer cells. MTT and EdU cell proliferation assays were used to determine the effect of these manipulations on breast cancer cell proliferation.

RESULTS

High αENaC mRNA expression was associated with less aggressive and less proliferative breast cancer subtypes and with reduced expression of proliferation markers. Decreased αENaC expression or activity, in the mesenchymal breast cancer cell lines BT549 and MDAMB231, increased breast cancer cell proliferation. Conversely, increased αENaC expression decreased breast cancer cell proliferation.

CONCLUSION

αENaC expression is associated with a poor prognosis in breast cancer and is a novel regulator of breast cancer cell proliferation. Taken together, these results identify ENaC as a potential future therapeutic target.

Upregulation of TRPM8 can promote the colon cancer liver metastasis through mediating Akt/GSK-3 signal pathway

This study aims to clarify the function of transient receptor potential melastatin 8 (TRPM8) in colon cancer liver metastasis. First, TRPM8 expression was determined by Western blotting in colon cancer patients with/without liver metastasis. Second, colon cancer cells were grouped into Mock, siCON, and siTRPM8 groups. Then, a series of in vitro experiments were conducted. Last, CT26 cells were used to construct colon cancer liver metastasis models on mice in vivo, followed by comparison of liver metastasis and determination of AKT/glycogen synthase kinase-3β (GSK-3β) pathway. Consequently, TRPM8 was upregulated in both colon cancer patients with/without liver metastasis, especially in those with metastasis. Compared with Mock and siCON groups, cells in siTRPM8 group demonstrated significant decreases in clone numbers, cell invasion, and migration; and obvious downregulations of p-AKT/AKT, p-GSK3β/GSK3β, Snail, and Vimentin, with an upregulation of E-cadherin. For in vivo experiments, a sharp decrease was observed in metastatic liver of mice in siTRPM8 group, with significant downregulations of p-AKT/AKT, p-GSK3β/GSK3β, Snail, and Vimentin and an upregulation of E-cadherin, as compared with Mock and siCON groups. Thus, TRPM8 was upregulated in colon cancer patients with liver metastasis, and silencing TRPM8 may suppress the progression and epithelial-mesenchymal transition of colon cancer cells to block its liver metastasis possibly by inhibiting AKT/GSK-3β pathway.

Deciphering the Role of Ca2+ Signalling in Cancer Metastasis: From the Bench to the Bedside

Metastatic cancer is one of the major causes of cancer-related mortalities. Metastasis is a complex, multi-process phenomenon, and a hallmark of cancer. Calcium (Ca2+) is a ubiquitous secondary messenger, and it has become evident that Ca2+ signalling plays a vital role in cancer. Ca2+ homeostasis is dysregulated in physiological processes related to tumour metastasis and progression-including cellular adhesion, epithelial-mesenchymal transition, cell migration, motility, and invasion. In this review, we looked at the role of intracellular and extracellular Ca2+ signalling pathways in processes that contribute to metastasis at the local level and also their effects on cancer metastasis globally, as well as at underlying molecular mechanisms and clinical applications. Spatiotemporal Ca2+ homeostasis, in terms of oscillations or waves, is crucial for hindering tumour progression and metastasis. They are a limited number of clinical trials investigating treating patients with advanced stages of various cancer types. Ca2+ signalling may serve as a novel hallmark of cancer due to the versatility of Ca2+ signals in cells, which suggests that the modulation of specific upstream/downstream targets may be a therapeutic approach to treat cancer, particularly in patients with metastatic cancers.

Calcium signaling: breast cancer's approach to manipulation of cellular circuitry

Calcium is a versatile element that participates in cell signaling for a wide range of cell processes such as death, cell cycle, division, migration, invasion, metabolism, differentiation, autophagy, transcription, and others. Specificity of calcium in each of these processes is achieved through modulation of intracellular calcium concentrations by changing the characteristics (amplitude/frequency modulation) or location (spatial modulation) of the signal. Breast cancer utilizes calcium signaling as an advantage for survival and progression. This review integrates evidence showing that increases in expression of calcium channels, GPCRs, pumps, effectors, and enzymes, as well as resulting intracellular calcium signals, lead to high calcium and/or an elevated calcium- mobilizing capacity necessary for malignant functions such as migratory, invasive, proliferative, tumorigenic, or metastatic capacities.

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.

Transient Receptor Potential Melastatin 8 (TRPM8) Channel Regulates Proliferation and Migration of Breast Cancer Cells by Activating the AMPK-ULK1 Pathway to Enhance Basal Autophagy

The calcium-permeable cation channel TRPM8 (transient receptor potential melastatin 8) is a member of the TRP superfamily of cation channels that is upregulated in various types of cancer with high levels of autophagy, including prostate, pancreatic, breast, lung, and colon cancers. Autophagy is closely regulated by AMP-activated protein kinase (AMPK) and plays an important role in tumor growth by generating nutrients through degradation of intracellular structures. Additionally, AMPK activity is regulated by intracellular Ca²⁺ concentration. Considering that TRPM8 is a non-selective Ca²⁺-permeable cation channel and plays a key role in calcium homoeostasis, we hypothesized that TRPM8 may control AMPK activity thus modulating cellular autophagy to regulate the proliferation and migration of breast cancer cells. In this study, overexpression of TRPM8 enhanced the level of basal autophagy, whereas TRPM8 knockdown reduced the level of basal autophagy in several types of mammalian cancer cells. Moreover, the activity of the TRPM8 channel modulated the level of basal autophagy. The mechanism of regulation of autophagy by TRPM8 involves autophagy-associated signaling pathways for activation of AMPK and ULK1 and phagophore formation. Impaired AMPK abolished TRPM8-dependent regulation of autophagy. TRPM8 interacts with AMPK in a protein complex, and cytoplasmic C-terminus of TRPM8 mediates the TRPM8–AMPK interaction. Finally, basal autophagy mediates the regulatory effects of TRPM8 on the proliferation and migration of breast cancer cells. Thus, this study identifies TRPM8 as a novel regulator of basal autophagy in cancer cells acting by interacting with AMPK, which in turn activates AMPK to activate ULK1 in a coordinated cascade of TRPM8-mediated breast cancer progression.

MAP30 Inhibits Bladder Cancer Cell Migration and Invasion In Vitro Through Suppressing Akt Pathway and the Epithelial/Mesenchymal Transition Process

The antitumor activity of Momordica anti-human immunodeficiency virus protein of 30 kDa (MAP30) has been proved. However, the role of MAP30 on tumor metastasis has not yet been identified. For this purpose, we investigated this effect and underlying mechanism of MAP30 in bladder cancer (BC). Here, we reported that MAP30 significantly inhibited the cell proliferation and clone formation of 5637 and T24 cells in vitro by promoting apoptosis and cell cycle arrest. We also found MAP30 inhibited cell migration and invasion by suppressing the epithelial/mesenchymal transition (EMT) process. Moreover, the Affymetrix GeneChip assay revealed that MAP30 significantly changed gene expression profile in T24 cells, especially the genes in cell cycle regulation pathways. After the Ingenuity Pathway Analysis, we predicted that NUPR1 was the most important upstream regulator. Subsequently, we verified that the AKT and EMT signaling pathways were inhibited by MAP30 treatment in T24 cells. In conclusion, MAP30 treatment inhibited the progression of human BC, especially cell migration and invasion through suppressing AKT pathways.

TRIM4 interacts with TRPM8 and regulates its channel function through K423-mediated ubiquitination

Transient receptor potential melastatin member 8 (TRPM8), a Ca²⁺ -permeable nonselective cation channel activated by cold and cooling agents, mediates allodynia. Dysfunction or abnormal expression of TRPM8 has been found in several human cancers. The role of ubiquitination in the regulation of TRPM8 function remains poorly understood. Here, we identified the ubiquitin (Ub)-ligase E3, tripartite motif-containing 4 (TRIM4), as a novel interaction partner of TRPM8 and confirmed that the TRIM4-TRPM8 interaction was mediated through the SPRY domain of TRIM4. Patch-clamp assays showed that TRIM4 negatively regulates TRPM8-mediated currents in HEK293 cells. Moreover, TRIM4 reduced the expression of TRPM8 on the cell surface by promoting the K63-linked ubiquitination of TRPM8. Further analyses revealed that the TRPM8 N-terminal lysine residue at 423 was the major ubiquitination site that mediates its functional regulation by TRIM4. A Ub-activating enzyme E1, Ub-like modifier-activating enzyme 1 (UBA1), was also found to interact with TRPM8, thereby regulating its channel function and ubiquitination. In addition, knockdown of UBA1 impaired the regulation of TRPM8 ubiquitination and function by TRIM4. Thus, this study demonstrates that TRIM4 downregulates TRPM8 via K423-mediated TRPM8 ubiquitination and requires UBA1 to regulate TRPM8.

TRP Channels and Small GTPases Interplay in the Main Hallmarks of Metastatic Cancer

Transient Receptor Potential (TRP) cations channels, as key regulators of intracellular calcium homeostasis, play a central role in the essential hallmarks of cancer. Among the multiple pathways in which TRPs may be involved, here we focus our attention on the ones involving small guanosine triphosphatases (GTPases), summarizing the main processes associated with the metastatic cascade, such as migration, invasion and tumor vascularization. In the last decade, several studies have highlighted a bidirectional interplay between TRPs and small GTPases in cancer progression: TRP channels may affect small GTPases activity via both Ca²⁺-dependent or Ca²⁺-independent pathways, and, conversely, some small GTPases may affect TRP channels activity through the regulation of their intracellular trafficking to the plasma membrane or acting directly on channel gating. In particular, we will describe the interplay between TRPC1, TRPC5, TRPC6, TRPM4, TRPM7 or TRPV4, and Rho-like GTPases in regulating cell migration, the cooperation of TRPM2 and TRPV2 with Rho GTPases in increasing cell invasiveness and finally, the crosstalk between TRPC1, TRPC6, TRPM8, TRPV4 and both Rho- and Ras-like GTPases in inducing aberrant tumor vascularization.

TRPV6 calcium channel directs homeostasis of the mammary epithelial sheets and controls epithelial mesenchymal transition

Epithelial integrity is lost upon cancer progression as cancer cells detach from the primary tumor site and start to invade to the surrounding tissues. Invasive cancers of epithelial origin often express altered levels of TRP-family cation channels. Upregulation of TRPV6 Ca2+-channel has been associated with a number of human malignancies and its high expression in breast cancer has been linked to both proliferation and invasive disease. The mechanisms behind the potential of TRPV6 to induce invasive progression have, however, not been well elucidated. Here we show that TRPV6 is connected to both E-cadherin-based adherens junctions and intracellular cytoskeletal structures. Loss of TRPV6 from normal mammary epithelial cells led to disruption of epithelial integrity and abnormal 3D-mammo sphere morphology. Furthermore, expression level of TRPV6 was tightly linked to the levels of common EMT markers, suggesting that TRPV6 may have a role in the mesenchymal invasion of breast cancer cells. Thus, either too low or too high TRPV6 levels compromise homeostasis of the mammary epithelial sheets and may promote the progression of pathophysiological conditions.

Highly functionalized β-lactams and 2-ketopiperazines as TRPM8 antagonists with antiallodynic activity

The cool sensor transient receptor potential melastatin channel 8 (TRPM8) is highly expressed in trigeminal and dorsal root ganglia, playing a key role in cold hypersensitivity associated to different peripheral neuropathies. Moreover, these channels are aberrantly expressed in different cancers, and seem to participate in tumor progression, survival and invasion. Accordingly, the search for potent and selective TRPM8 modulators attracted great interest in recent years. We describe new heterocyclic TRPM8 antagonist chemotypes derived from N-cloroalkyl phenylalaninol-Phe conjugates. The cyclization of these conjugates afforded highly substituted β-lactams and/or 2-ketopiperazine (KP) derivatives, with regioselectivity depending on the N-chloroalkyl group and the configuration. These derivatives behave as TRPM8 antagonists in the Ca2+ microfluorometry assay, and confirmed electrophysiologically for the best enantiopure β-lactams 24a and 29a (IC50, 1.4 and 0.8 µM). Two putative binding sites by the pore zone, different from those found for typical agonists and antagonists, were identified by in silico studies for both β-lactams and KPs. β-Lactams 24a and 29a display antitumor activity in different human tumor cell lines (micromolar potencies, A549, HT29, PSN1), but correlation with TRPM8 expression could not be established. Additionally, compound 24a significantly reduced cold allodynia in a mice model of oxaliplatin-induced peripheral neuropathy.

Calcium Permeable Channels in Cancer Hallmarks

Cancer, the second cause of death worldwide, is characterized by several common criteria, known as the “cancer hallmarks” such as unrestrained cell proliferation, cell death resistance, angiogenesis, invasion and metastasis. Calcium permeable channels are proteins present in external and internal biological membranes, diffusing Ca²⁺ ions down their electrochemical gradient. Numerous physiological functions are mediated by calcium channels, ranging from intracellular calcium homeostasis to sensory transduction. Consequently, calcium channels play important roles in human physiology and it is not a surprise the increasing number of evidences connecting calcium channels disorders with tumor cells growth, survival and migration. Multiple studies suggest that calcium signals are augmented in various cancer cell types, contributing to cancer hallmarks. This review focuses in the role of calcium permeable channels signaling in cancer with special attention to the mechanisms behind the remodeling of the calcium signals. Transient Receptor Potential (TRP) channels and Store Operated Channels (SOC) are the main extracellular Ca²⁺ source in the plasma membrane of non-excitable cells, while inositol trisphosphate receptors (IP₃R) are the main channels releasing Ca²⁺ from the endoplasmic reticulum (ER). Alterations in the function and/or expression of these calcium channels, as wells as, the calcium buffering by mitochondria affect intracellular calcium homeostasis and signaling, contributing to the transformation of normal cells into their tumor counterparts. Several compounds reported to counteract several cancer hallmarks also modulate the activity and/or the expression of these channels including non-steroidal anti-inflammatory drugs (NSAIDs) like sulindac and aspirin, and inhibitors of polyamine biosynthesis, like difluoromethylornithine (DFMO). The possible role of the calcium permeable channels targeted by these compounds in cancer and their action mechanism will be discussed also in the review.

TRPM8 channels: A review of distribution and clinical role

Ion channels are important therapeutic targets due to their plethoric involvement in physiological and pathological consequences. The transient receptor potential cation channel subfamily M member 8 (TRPM8) is a nonselective cation channel that controls Ca²⁺ homeostasis. It has been proposed to be the predominant thermoreceptor for cellular and behavioral responses to cold stimuli in the transient receptor potential (TRP) channel subfamilies and exploited so far to reach the clinical-stage of drug development. TRPM8 channels can be found in multiple organs and tissues, regulating several important processes such as cell proliferation, migration and apoptosis, inflammatory reactions, immunomodulatory effects, pain, and vascular muscle tension. The related disorders have been expanded to new fields ranging from cancer and migraine to dry eye disease, pruritus, irritable bowel syndrome (IBS), and chronic cough. This review is aimed to summarize the distribution of TRPM8 and disorders related to it from a clinical perspective, so as to broaden the scope of knowledge of researchers to conduct more studies on this subject.

Exploring the Therapeutic Potential of Membrane Transport Proteins: Focus on Cancer and Chemoresistance

Improving the therapeutic efficacy of conventional anticancer drugs represents the best hope for cancer treatment. However, the shortage of druggable targets and the increasing development of anticancer drug resistance remain significant problems. Recently, membrane transport proteins have emerged as novel therapeutic targets for cancer treatment. These proteins are essential for a plethora of cell functions ranging from cell homeostasis to clinical drug toxicity. Furthermore, their association with carcinogenesis and chemoresistance has opened new vistas for pharmacology-based cancer research. This review provides a comprehensive update of our current knowledge on the functional expression profile of membrane transport proteins in cancer and chemoresistant tumours that may form the basis for new cancer treatment strategies.

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.

Differential engagement of ORAI1 and TRPC1 in the induction of vimentin expression by different stimuli

The Ca²⁺ signal is essential in both hypoxia- and epidermal growth factor (EGF)-mediated epithelial to mesenchymal transition (EMT) in MDA-MB-468 breast cancer cells. This finding suggests that Ca²⁺-permeable ion channels participate in the induction of expression of some mesenchymal markers such as vimentin. However, the ion channels involved in vimentin expression induction have not been fully characterized. This work sought to define how differential modulation of the calcium signal effects the induction of vimentin and the Ca²⁺ influx pathways involved. We identified that the intracellular Ca²⁺ chelator EGTA-AM, cytochalasin D (a modulator of cytoskeletal dynamics and cell morphology), and the sarco/endoplasmic reticulum ATPase inhibitor thapsigargin are all inducers of vimentin in MDA-MB-468 breast cancer cells. EGTA-AM- and thapsigargin-mediated induction of vimentin expression in MDA-MB-468 cells involves store-operated Ca²⁺ entry, as evidenced by sensitivity to silencing of the molecular components of this pathway, STIM1 and ORAI1. In stark contrast, cytochalasin D-mediated vimentin induction was insensitive to silencing of ORAI1, despite sensitivity to silencing of its canonical activator the endoplasmic reticulum Ca²⁺ sensor STIM1. Cytochalasin D-mediated vimentin induction was, however, sensitive to silencing of another reported STIM1 target, TRPC1. Subsequent studies identified that EGTA-AM-induced vimentin expression also partially involved a TRPC1-dependent pathway. These studies define a complex interplay between vimentin expression in this model and the specific Ca²⁺-permeable ion channels involved. The complexity in the engagement of different Ca²⁺ influx pathways that regulate vimentin induction are opportunities but also potential challenges in targeting Ca²⁺ signaling to block EMT in cancer cells. Our findings further highlight the need to identify potential indispensable ion channels that can regulate induction of specific mesenchymal markers via different stimuli.

Calcium transport and signalling in breast cancer: Functional and prognostic significance

Comprised of a complex network of numerous intertwining pathways, the Ca²⁺ signalling nexus is an essential mediator of many normal cellular activities. Like many other such functions, the normal physiological activity of Ca²⁺ signalling is frequently co-opted and reshaped in cases of breast cancer, creating a potent oncogenic drive within the affected cell population. Such modifications can occur within pathways mediating either Ca²⁺ import (e.g. TRP channels, ORAI-STIM1) or Ca²⁺ export (e.g. PMCA), indicating that both increases and decreases within cellular Ca²⁺ levels have the potential to increase the malignant potential of a cell. Increased understanding of these pathways may offer clinical benefit in terms of both prognosis and treatment; patient survival has been linked to expression levels of certain Ca²⁺ transport proteins, whilst selective targeting of these factors with novel anti-cancer agents has demonstrated a variety of anti-tumour effects in in vitro studies. In addition, the activity of several Ca²⁺ signalling pathways has been shown to influence chemotherapy response, suggesting that a synergistic approach coupling traditional chemotherapy with Ca²⁺ targeting agents may also improve patient outcome. As such, targeted modulation of these pathways represents a novel approach in precision medicine and breast cancer therapy.

The oncogenic roles of TRPM ion channels in cancer

Transient receptor potential (TRP) proteins are a diverse family of ion channels present in multiple types of tissues. They function as gatekeepers for responses to sensory stimuli including temperature, vision, taste, and pain through their activities in conducting ion fluxes. The TRPM (melastatin) subfamily consists of eight members (i.e., TRPM1-8), which collectively regulate fluxes of various types of cations such as K⁺ , Na⁺ , Ca²⁺ , and Mg²⁺ . Growing evidence in the past two decades indicates that TRPM ion channels, their isoforms, or long noncoding RNAs encoded within the locus may be oncogenes involved in the regulation of cancer cell growth, proliferation, autophagy, invasion, and epithelial-mesenchymal transition, and their significant association with poor clinical outcomes of cancer patients. In this review, we describe and discuss recent findings implicating TRPM channels in different malignancies, their functions, mechanisms, and signaling pathways involved in cancers, as well as summarizing their normal physiological functions and the availability of ion channel pharmacological inhibitors.

Bioelectric Control of Metastasis in Solid Tumors

As the leading cause of death in cancer, there is an urgent need to develop treatments to target the dissemination of primary tumor cells to secondary organs, known as metastasis. Bioelectric signaling has emerged in the last century as an important controller of cell growth, and with the development of current molecular tools we are now beginning to identify its role in driving cell migration and metastasis in a variety of cancer types. This review summarizes the currently available research for bioelectric signaling in solid tumor metastasis. We review the steps of metastasis and discuss how these can be controlled by bioelectric cues at the level of a cell, a population of cells, and the tissue. The role of ion channel, pump, and exchanger activity and ion flux is discussed, along with the importance of the membrane potential and the relationship between ion flux and membrane potential. We also provide an overview of the evidence for control of metastasis by external electric fields (EFs) and draw from examples in embryogenesis and regeneration to discuss the implications for endogenous EFs. By increasing our understanding of the dynamic properties of bioelectric signaling, we can develop new strategies that target metastasis to be translated into the clinic.

The Calcium-Signaling Toolkit in Cancer: Remodeling and Targeting

Processes that are important in cancer progression, such as sustained cell growth, invasion to other organs, and resistance to cell death inducers, have a clear overlap with pathways regulated by Ca²⁺ signaling. It is therefore not surprising that proteins important in Ca²⁺ signaling, sometimes referred to as the "Ca²⁺ signaling toolkit," can contribute to cancer cell proliferation and invasiveness, and the ability of agents to induce cancer cell death. Ca²⁺ signaling is also critical in other aspects of cancer progression, including events in the tumor microenvironment and processes involved in the acquisition of resistance to anticancer therapies. This review will consider the role of Ca²⁺ signaling in tumor progression and highlight areas in which a better understanding of the interplay between the Ca²⁺-signaling toolkit and tumorigenesis is still required.

TRPM2 in Cancer

The TRP ion channel TRPM2 has an essential function in cell survival and protects the viability of a number of cell types after oxidative stress. It is highly expressed in many cancers including breast, prostate, and pancreatic cancer, melanoma, leukemia, and neuroblastoma, suggesting it promotes cancer cell survival. TRPM2 is activated by production of ADP-ribose (ADPR) following oxidative stress, which binds to the C-terminus of TRPM2, resulting in channel opening. In a number of cancers including neuroblastoma, TRPM2 has been shown to preserve viability and mechanisms have been identified. Activation of TRPM2 results in expression of transcription factors and kinases important in cell proliferation and survival including HIF-1/2α, CREB, nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2), and Pyk2, and Src phosphorylation. Together, HIF-1/2α and CREB regulate expression of genes encoding proteins with roles in mitochondrial function including members of the electron transport complex involved in ATP production. These contribute to lower mitochondrial ROS production while expression of antioxidants regulated by HIF-1/2α, FOXO3a, CREB, and Nrf2 is maintained. CREB is also important in control of expression of key proteins involved in autophagy. When TRPM2-mediated calcium influx is inhibited, mitochondria are dysfunctional, cellular bioenergetics are reduced, production of ROS is increased, and autophagy and DNA repair are impaired, decreasing tumor growth and increasing chemotherapy sensitivity. Inhibition of TRPM2 expression or function results in decreased tumor proliferation and/or viability in many malignancies including breast, gastric, pancreatic, prostate, head and neck cancers, melanoma, neuroblastoma, and T-cell and acute myelogenous leukemia. However, in a small number of malignancies, activation of TRPM2 rather than inhibition has been reported to reduce tumor cell survival. Here, TRPM2-mediated Ca²⁺ signaling and mechanisms of regulation of cancer cell growth and survival are reviewed and controversies discussed. Evidence suggests that targeting TRPM2 may be a novel therapeutic approach in many cancers.

Ion Channels in Cancer: Are Cancer Hallmarks Oncochannelopathies?

Genomic instability is a primary cause and fundamental feature of human cancer. However, all cancer cell genotypes generally translate into several common pathophysiological features, often referred to as cancer hallmarks. Although nowadays the catalog of cancer hallmarks is quite broad, the most common and obvious of them are 1) uncontrolled proliferation, 2) resistance to programmed cell death (apoptosis), 3) tissue invasion and metastasis, and 4) sustained angiogenesis. Among the genes affected by cancer, those encoding ion channels are present. Membrane proteins responsible for signaling within cell and among cells, for coupling of extracellular events with intracellular responses, and for maintaining intracellular ionic homeostasis ion channels contribute to various extents to pathophysiological features of each cancer hallmark. Moreover, tight association of these hallmarks with ion channel dysfunction gives a good reason to classify them as special type of channelopathies, namely oncochannelopathies. Although the relation of cancer hallmarks to ion channel dysfunction differs from classical definition of channelopathies, as disease states causally linked with inherited mutations of ion channel genes that alter channel's biophysical properties, in a broader context of the disease state, to which pathogenesis ion channels essentially contribute, such classification seems absolutely appropriate. In this review the authors provide arguments to substantiate such point of view.

Carbonate Apatite Nanoparticles-Facilitated Intracellular Delivery of siRNA(s) Targeting Calcium Ion Channels Efficiently Kills Breast Cancer Cells

Specific gene knockdown facilitated by short interfering RNA (siRNA) is a potential approach for suppressing the expression of ion channels and transporter proteins to kill breast cancer cells. The overexpression of calcium ion channels and transporter genes is seen in the MCF-7 breast cancer cell line. Since naked siRNA is anionic and prone to nuclease-mediated degradation, it has limited permeability across the cationic cell membrane and short systemic half-life, respectively. Carbonate apatite (CA) nanoparticles were formulated, characterized, loaded with a series of siRNAs, and delivered into MCF-7 and 4T1 breast cancer cells to selectively knockdown the respective calcium and magnesium ion channels and transporters. Individual knockdown of TRPC6, TRPM7, TRPM8, SLC41A1, SLC41A2, ORAI1, ORAI3, and ATP2C1 genes showed significant reduction (p < 0.001) in cell viability depending on the cancer cell type. From a variety of combinations of siRNAs, the combination of TRPC6, TRPM8, SLC41A2, and MAGT1 siRNAs delivered via CA produced the greatest cell viability reduction, resulting in a cytotoxicity effect of 57.06 ± 3.72% (p < 0.05) and 59.83 ± 2.309% (p = 0.09) in 4T1 and MCF-7 cell lines, respectively. Some of the combinations were shown to suppress the Akt pathway in Western Blot analysis when compared to the controls. Therefore, CA-siRNA-facilitated gene knockdown in vitro holds a high prospect for deregulating cell proliferation and survival pathways through the modulation of Ca²⁺ signaling in breast cancer cells.

Elevated Transient Receptor Potential Melastatin 8 (TRPM8) Expression Is Correlated with Poor Prognosis in Pancreatic Cancer

BACKGROUND The transient receptor potential melastatin 8 (TRPM8) was found to be expressed abnormally in a variety of tumors and is associated with unfavorable prognosis in human cancers. However, its clinical significance in pancreatic cancer (PC) is mostly unknown. MATERIAL AND METHODS qRT-PCR was performed to measure the expression of TRPM8 in 110 pairs of PC tissues and the adjacent non-cancerous tissues. The association of TRPM8 expression with the clinical characters of PC patients was analyzed using the chi-square test. Furthermore, the prognostic value of TRPM8 was determined with Kaplan-Meier survival curve and Cox regression analysis. RESULTS We found that the expression level of TRPM8 was significantly elevated in PC tissues compared to the non-cancerous controls (P<0.001). In addition, a close relationship was observed between elevated TRPM8 expression with large tumor size (P=0.001), advanced TNM (P=0.013), and distant metastasis (P=0.034). Survival analysis suggested that patients with high TRPM8 expression has worse OS (P=0.001) and DFS (P<0.001) than those with low TRPM8 expression. Moreover, TRPM8 was confirmed as a valuable prognostic biomarker for OS (HR=1.913; 95% CI: 1.020-3.589; P=0.043) or DFS (HR=2.374; 95% CI: 1.269-4.443; P=0.007) of PC patients. CONCLUSIONS This study shows that TRPM8 expression is significantly up-regulated in PC and it might be a useful prognostic factor for patients with PC.