TRPM8: a potential target for cancer treatment

Roles of TRPM channels in glioma

Gliomas are the most common type of primary brain tumor. Despite advances in treatment, it remains one of the most aggressive and deadly tumor of the central nervous system (CNS). Gliomas are characterized by high malignancy, heterogeneity, invasiveness, and high resistance to radiotherapy and chemotherapy. It is urgent to find potential new molecular targets for glioma. The TRPM channels consist of TRPM1-TPRM8 and play a role in many cellular functions, including proliferation, migration, invasion, angiogenesis, etc. More and more studies have shown that TRPM channels can be used as new therapeutic targets for glioma. In this review, we first introduce the structure, activation patterns, and physiological functions of TRPM channels. Additionally, the pathological mechanism of glioma mediated by TRPM2, 3, 7, and 8 and the related signaling pathways are described. Finally, we discuss the therapeutic potential of targeting TRPM for glioma.

Population-enriched innate immune variants may identify candidate gene targets at the intersection of cancer and cardio-metabolic disease

Both cancer and cardio-metabolic disease disparities exist among specific populations in the US. For example, African Americans experience the highest rates of breast and prostate cancer mortality and the highest incidence of obesity. Native and Hispanic Americans experience the highest rates of liver cancer mortality. At the same time, Pacific Islanders have the highest death rate attributed to type 2 diabetes (T2D), and Asian Americans experience the highest incidence of non-alcoholic fatty liver disease (NAFLD) and cancers induced by infectious agents. Notably, the pathologic progression of both cancer and cardio-metabolic diseases involves innate immunity and mechanisms of inflammation. Innate immunity in individuals is established through genetic inheritance and external stimuli to respond to environmental threats and stresses such as pathogen exposure. Further, individual genomes contain characteristic genetic markers associated with one or more geographic ancestries (ethnic groups), including protective innate immune genetic programming optimized for survival in their corresponding ancestral environment(s). This perspective explores evidence related to our working hypothesis that genetic variations in innate immune genes, particularly those that are commonly found but unevenly distributed between populations, are associated with disparities between populations in both cancer and cardio-metabolic diseases. Identifying conventional and unconventional innate immune genes that fit this profile may provide critical insights into the underlying mechanisms that connect these two families of complex diseases and offer novel targets for precision-based treatment of cancer and/or cardio-metabolic disease.

Expression of TRPM8 in sheep reproductive tissues and brain areas important for the expression of reproductive behavior

The Transient Receptor Potential Melastatin 8 (TRPM8) channel is a temperature-sensitive, calcium permeable ion channel and purported testosterone receptor. To determine how the hormone environment influences the expression of TRPM8 in gonadal tissue and areas of the brain important for reproduction, tissue from western white-faced cross-bred ewes, rams, and gonadectomized males (wethers; n = 6 per group) approximately 6 mo of age were collected. TRPM8 mRNA expression was greater (P = 0.01) in prostate of rams than wethers. Testes had greater (P = 0.004) expression of TRPM8 mRNA than the ovary. Differences in protein expression was similar with the testes having greater (P = 0.007) TRPM8 protein than the ovary. Protein expression did not differ (P = 0.6) in the prostate due to presence (ram) or absence (wether) of the testes. In the brain, TRPM8 varied in the amygdala with rams tending (P = 0.07) to express more mRNA which was reflected in greater (P = 0.04) number of neurons staining positive for TRPM8 in the central amygdala. Differences among ewes and wethers were not detected. This pattern was not observed (P ≥ 0.16) in the hypothalamus or olfactory bulb. To determine if TRPM8 was associated with the expression of ram sexual behavior, brains from rams categorized as high (n = 4) or low (n = 3) sexual activity were collected and blocked. Presence of TRPM8 channels was verified in the amygdala and hypothalamus of rams but was absent in the ventral tegmental area. Numbers of neurons staining positive for TRPM8 did not differ by expression of sexual behavior (P ≥ 0.2) in any area quantified. While expression of TRPM8 is more robust in tissues from intact males, expression of the channel does not appear to be important in the expression of sexual behavior.

The Role of Calcium Channels in Prostate Cancer Progression and Potential as a Druggable Target for Prostate Cancer Treatment

Prostate cancer (PCa) is the most diagnosed cancer among men. Discovering novel prognostic biomarkers and potential therapeutic targets are critical. Calcium signaling has been implicated in PCa progression and development of treatment resistance. Altered modification of Ca²⁺ flows leads to serious pathophysiological processes, such as malignant transformation, tumor proliferation, epithelial to mesenchymal transition, evasion of apoptosis, and treatment resistance. Calcium channels control and contribute to these processes. PCa has shown defective Ca²⁺ channels, which subsequently promotes tumor metastasis and growth. Store-operated Ca²⁺ entry channels such as Orai and STIM channels and transient receptor potential channels play a significant role in PCa pathogenesis. Pharmacological modulation of these calcium channels or pumps has been suggested as a practical approach. In this review, we discuss the role of calcium channels in PCa development and progression, and we identify current novel discoveries of drugs that target specific calcium channels for the treatment of PCa.

TRPM8 promotes hepatocellular carcinoma progression by inducing SNORA55 mediated nuclear-mitochondrial communication

Transient receptor potential melastatin 8 (TRPM8) play crucial roles in solid tumors such as prostate and breast cancers. But the role of TRPM8 in hepatocellular carcinoma (HCC) and its underlying molecular mechanisms remain largely unknown. In this study, the functional roles of TRPM8 in HCC were systematically investigated for the first time. It was found that the expression level of TRPM8 was significantly upregulated in HCC, which was positively correlated with the worse clinicopathological characteristics. Functional studies revealed that pharmacological inhibition or genetic downregulation of TRPM8 ameliorated hepatocarcinogenesis in vitro and in vivo. Mechanistically, the oncogenic role of TRPM8 in HCC was at least partially achieved by affecting mitochondrial function. TRPM8 could modulate the expression of nucleolar relative molecule-small nucleolar RNA, H/ACA box 55 (SNORA55) by inducing transformation of chromatin structure and histone modification type. These data suggest that as a bridge molecule in TRPM8-triggered HCC, SNORA55 can migrate from nucleus to mitochondria and exert oncogenic role by affecting mitochondria function through targeting ATP5A1 and ATP5B. Herein, we uncovered the potent oncogenic role of TRPM8 in HCC by inducing nuclear and mitochondrial dysfunction in a SNORA55 dependent manner, and provided a potential therapeutic target for HCC.

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.

Tegaserod maleate exhibits antileukemic activity by targeting TRPM8

To identify therapeutic targets in acute myeloid leukemia (AML), we conducted growth inhibition screens of 2040 small molecules from a library of FDA-approved drugs using a panel of 12 AML cell lines. Tegaserod maleate, a 5-hydroxytryptamine 4 receptor partial agonist, elicits strong anti-AML effects in vitro and in vivo by targeting transient receptor potential melastatin subtype 8 (TRPM8), which plays critical roles in several important processes. However, the role of TRPM8 remains incompletely described in AML, whose treatment is based mostly on antimitotic chemotherapy. Here, we report an unexpected role of TRPM8 in leukemogenesis. Strikingly, TRPM8 knockout inhibits AML cell survival/proliferation by promoting apoptosis. Mechanistically, TRPM8 exerts its oncogenic effect by regulating the ERK-CREB/c-Fos signaling axis. Hyperactivation of ERK signaling can be reversed by TRPM8 inhibition. Importantly, TRPM8 is overexpressed in AML patients, indicating that it is a new prognostic factor in AML. Collectively, our work demonstrates the anti-AML effects of tegaserod maleate via targeting TRPM8 and indicates that TRPM8 is a regulator of leukemogenesis with therapeutic potential in AML.

Comprehensive Pan-Cancer Analysis of TRPM8 in Tumor Metabolism and Immune Escape

Background

Transient receptor potential melastatin 8 (TRPM8) modulates tumor biology and sensitivity to treatment. The present study aimed to determine the part it plays in tumor immunity and physiology using pan-cancer analysis.

Method

Data from the GTEx, CCLE, TISIDB, GSCA, cBioportal, and TCGA databases were collected using Estimate, Scanneo, and GSEA, and the associations between TRPM8 and prognosis, molecular subtypes, mutational burden, microsatellite instability, immune gene functions, and drug sensitivity were analyzed in 33 tumor types.

Result

TRPM8 levels were found to be elevated in most tumors, particularly in solid tumors, with variations according to clinical stage. Mutation frequency was greatest in endometrial carcinoma. High levels of TRPM8 were linked to unfavorable prognosis, immune cell infiltration, and the tumor microenvironment, as well as correlating with abnormalities in the transcription levels of genes associated with immunity and DNA repair. TRPM8 was also linked to unfavorable patient outcomes and cancer-associated signaling.

Conclusions

TRPM8 is strongly associated with tumor physiology and immunity. The Pan-Cancer analysis suggests the potential of TRPM8 as a treatment target or biomarker for determining the prognosis of a specific type of cancer.

The LCK-14-3-3ζ-TRPM8 axis regulates TRPM8 function/assembly and promotes pancreatic cancer malignancy

Transient receptor potential melastatin 8 (TRPM8) functions as a Ca2+-permeable channel in the plasma membrane (PM). Dysfunction of TRPM8 is associated with human pancreatic cancer and several other diseases in clinical patients, but the underlying mechanisms are unclear. Here, we found that lymphocyte-specific protein tyrosine kinase (LCK) directly interacts with TRPM8 and potentiates TRPM8 phosphorylation at Y1022. LCK positively regulated channel function characterized by increased TRPM8 current densities by enhancing TRPM8 multimerization. Furthermore, 14-3-3ζ interacted with TRPM8 and positively modulated channel multimerization. LCK significantly enhanced the binding of 14-3-3ζ and TRPM8, whereas mutant TRPM8-Y1022F impaired TRPM8 multimerization and the binding of TRPM8 and 14-3-3ζ. Knockdown of 14-3-3ζ impaired the regulation of TRPM8 multimerization by LCK. In addition, TRPM8 phosphotyrosine at Y1022 feedback regulated LCK activity by inhibiting Tyr505 phosphorylation and modulating LCK ubiquitination. Finally, we revealed the importance of TRPM8 phosphorylation at Y1022 in the proliferation, migration, and tumorigenesis of pancreatic cancer cells. Our findings demonstrate that the LCK-14-3-3ζ-TRPM8 axis for regulates TRPM8 assembly, channel function, and LCK activity and maybe provide potential therapeutic targets for pancreatic cancer.

Identification of a Novel Inhibitor of TfR1 from Designed and Synthesized Muriceidine A Derivatives

The transferrin receptor 1 (TfR1) plays a key role in cellular iron uptake through its interaction with iron-bound Tf. TfR1 is often reported to be overexpressed in malignant cells, and this increase may be associated with poor prognosis in different types of cancer, which makes it an attractive target for antitumor therapy. The marine natural product Muriceidine A is a potent anticancer agent reported in our previous work. In this study, we designed and synthesized a series of Muriceidine A derivatives and described the systematic investigation into their cytotoxic activities against four tumor cells. Most of the derivatives showed stronger antitumor activity and we found that the introduction of electron-donating groups at position C-2 of unsaturated piperidine was beneficial to anticancer activity and unsaturated piperidine was responsible for the antiproliferative activity. Among these compounds, 12b (methyl at position C-2 of unsaturated piperidine) exhibited the strongest cytotoxicity against MDA-MB-231 cells. Further pharmacological research showed that 12b bound to Transferrin receptor 1 (TfR1) directly caused iron deprivation and ROS imbalance along with the degradations of several oncoproteins, especially FGFR1, through the proteasome pathway; thus, inducing cell cycle arrest and apoptosis in MDA-MB-231 breast cancer cells. Our findings indicate that 12b is a promising lead compound targeting TfR1 for triple negative breast cancer.

On the Connections between TRPM Channels and SOCE

Plasma membrane protein channels provide a passageway for ions to access the intracellular milieu. Rapid entry of calcium ions into cells is controlled mostly by ion channels, while Ca2+-ATPases and Ca2+ exchangers ensure that cytosolic Ca2+ levels ([Ca2+]cyt) are maintained at low (~100 nM) concentrations. Some channels, such as the Ca2+-release-activated Ca2+ (CRAC) channels and voltage-dependent Ca2+ channels (CACNAs), are highly Ca2+-selective, while others, including the Transient Receptor Potential Melastatin (TRPM) family, have broader selectivity and are mostly permeable to monovalent and divalent cations. Activation of CRAC channels involves the coupling between ORAI1-3 channels with the endoplasmic reticulum (ER) located Ca2+ store sensor, Stromal Interaction Molecules 1-2 (STIM1/2), a pathway also termed store-operated Ca2+ entry (SOCE). The TRPM family is formed by 8 members (TRPM1-8) permeable to Mg2+, Ca2+, Zn2+ and Na+ cations, and is activated by multiple stimuli. Recent studies indicated that SOCE and TRPM structure-function are interlinked in some instances, although the molecular details of this interaction are only emerging. Here we review the role of TRPM and SOCE in Ca2+ handling and highlight the available evidence for this interaction.

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.

New Insights and Emerging Therapeutic Approaches in Prostate Cancer

Prostate cancer is the second most frequently diagnosed cancer in men and several therapeutic approaches are currently available for patient's care. Although the androgen receptor status represents a good predictor of response to androgen deprivation therapy, prostate cancer frequently becomes resistant to this approach and spreads. The molecular mechanisms that contribute to progression and drug-resistance of this cancer remain still debated. However, few therapeutic options are available for patient's management, at this stage. Recent years have seen a great expansion of the studies concerning the role of stromal-epithelial interactions and tumor microenvironment in prostate cancer progression. The findings so far collected have provided new insights into diagnostic and clinical management of prostate cancer patients. Further, new fascinating aspects concerning the intersection of the androgen receptor with survival factors as well as calcium channels have been reported in cultured prostate cancer cells and mouse models. The results of these researches have opened the way for a better understanding of the basic mechanisms involved in prostate cancer invasion and drug-resistance. They have also significantly expanded the list of new biomarkers and druggable targets in prostate cancer. The primary aim of this manuscript is to provide an update of these issues, together with their translational aspects. Exploiting the power of novel promising therapeutics would increase the success rate in the diagnostic path and clinical management of patients with advanced disease.

Therapeutic potential of TRPM8 antagonists in prostate cancer

Transient receptor potential melastatin-8 (TRPM8) represents an emerging target in prostate cancer, although its mechanism of action remains unclear. Here, we have characterized and investigated the effects of TRPM8 modulators in prostate cancer aggressiveness disclosing the molecular mechanism underlying their biological activity. Patch-clamp and calcium fluorometric assays were used to characterize the synthesized compounds. Androgen-stimulated prostate cancer-derived cells were challenged with the compounds and the DNA synthesis was investigated in a preliminary screening. The most effective compounds were then employed to inhibit the pro-metastatic behavior of in various PC-derived cells, at different degree of malignancy. The effect of the compounds was then assayed in prostate cancer cell-derived 3D model and the molecular targets of selected compounds were lastly identified using transcriptional and non-transcriptional reporter assays. TRPM8 antagonists inhibit the androgen-dependent prostate cancer cell proliferation, migration and invasiveness. They are highly effective in reverting the androgen-induced increase in prostate cancer cell spheroid size. The compounds also revert the proliferation of castrate-resistant prostate cancer cells, provided they express the androgen receptor. In contrast, no effects were recorded in prostate cancer cells devoid of the receptor. Selected antagonists interfere in non-genomic androgen action and abolish the androgen-induced androgen receptor/TRPM8 complex assembly as well as the increase in intracellular calcium levels in prostate cancer cells. Our results shed light in the processes controlling prostate cancer progression and make the transient receptor potential melastatin-8 as a ‘druggable’ target in the androgen receptor-expressing prostate cancers.

Discovery of Novel TRPM8 Blockers Suitable for the Treatment of Somatic and Ocular Painful Conditions: A Journey through pKa and LogD Modulation

Transient receptor potential melastatin 8 (TRPM8) is crucially involved in pain modulation and perception, and TRPM8 antagonists have been proposed as potential therapeutic approaches for pain treatment. Previously, we developed two TRPM8 antagonists and proposed them as drug candidates for topical and systemic pain treatment. Here, we describe the design and synthesis of these two TRPM8 antagonists (27 and 45) and the rational approach of modulation/replacement of bioisosteric chemical groups, which allowed us to identify a combination of narrow ranges of pK_a and LogD values that were crucial to ultimately optimize their potency and metabolic stability. Following the same approach, we then pursued the development of new TRPM8 antagonists suitable for the topical treatment of ocular painful conditions and identified two new compounds (51 and 59), N-alkoxy amide derivatives, that can permeate across ocular tissue and reduce the behavioral responses induced by the topical ocular menthol challenge in vivo.

Design, synthesis and biological evaluation of new thiazole scaffolds as potential TRPM8 antagonists

The preliminary results on the development of a viable methodology for the further functionalization of 4-hydroxythiazole derivatives to afford target TRPM8 antagonists are reported. The combined Sonogashira coupling/annulation reactions of the ethyl 2-(3-fluorophenyl)-4-tifluoromethylsulfonyloxy-1,3-thiazole-5-carboxylate have been applied to the synthesis of analogues of the selective blocker of TRPM8 DFL23448. Among all the synthetised derivatives, the most promising compound resulted to be active as TRPM8 blocker (IC50 = 4.06 µM), showing an excellent metabolic stability and no cytotoxic effects. Finally, in silico characterisation of the derivatives showed no violation of the drug-likeness rules.

TRPM8 Channels: Advances in Structural Studies and Pharmacological Modulation

The transient receptor potential melastatin subtype 8 (TRPM8) is a cold sensor in humans, activated by low temperatures (>10, <28 °C), but also a polymodal ion channel, stimulated by voltage, pressure, cooling compounds (menthol, icilin), and hyperosmolarity. An increased number of experimental results indicate the implication of TRPM8 channels in cold thermal transduction and pain detection, transmission, and maintenance in different tissues and organs. These channels also have a repercussion on different kinds of life-threatening tumors and other pathologies, which include urinary and respiratory tract dysfunctions, dry eye disease, and obesity. This compendium firstly covers newly described papers on the expression of TRPM8 channels and their correlation with pathological states. An overview on the structural knowledge, after cryo-electron microscopy success in solving different TRPM8 structures, as well as some insights obtained from mutagenesis studies, will follow. Most recently described families of TRPM8 modulators are also covered, along with a section of molecules that have reached clinical trials. To finalize, authors provide an outline of the potential prospects in the TRPM8 field.

Role of TRPM7 kinase in cancer

Cancer is the second leading cause of death worldwide and accounted for an estimated 9.6 million deaths, or 1 in 6 deaths, in 2018. Despite recent advances in cancer prevention, diagnosis, and treatment strategies, the burden of this disease continues to grow with each year, with dire physical, emotional, and economic consequences for all levels of society. Classic characteristics of cancer include rapid, uncontrolled cell proliferation and spread of cancerous cells to other parts of the body, a process known as metastasis. Transient receptor potential melastatin 7 (TRPM7), a Ca²⁺- and Mg²⁺-permeable nonselective divalent cation channel defined by the atypical presence of an α-kinase within its C-terminal domain, has been implicated, due to its modulation of Ca²⁺ and Mg²⁺ influx, in a wide variety of physiological and pathological processes, including cancer. TRPM7 is overexpressed in several cancer types and has been shown to variably increase cellular proliferation, migration, and invasion of tumour cells. However, the relative contribution of TRPM7 kinase domain activity to cancer as opposed to ion flux through its channel pore remains an area of active discovery. In this review, we describe the specific role of the TRPM7 kinase domain in cancer processes as well as mechanisms of regulation and inhibition of the kinase domain.

Expression of transient receptor potential cation channel subfamily M member 8 in gastric cancer and its clinical significance

Transient receptor potential cation channel subfamily M member (TRPM8) is abnormally expressed in many malignant tumors, such as breast cancer and pancreatic cancer, but its expression in gastric cancer (GC) has remained unclear. The present study aimed to detect TRPM8 expression and to explore its clinical significance in GC. Western blotting and immunohistochemistry were used to detect the protein expression of TRPM8 in 134 pairs of GC and adjacent healthy tissues. The association of TRMP8 with the 5-year overall survival rate of patients with GC was assessed using a Cox regression model. TRPM8 protein expression was significantly elevated (P<0.05) in gastric tumor cells (SUN-1, AGS, SNU-5 and NCI-N87) and was significantly associated with tumor diameter (P=0.003), Tumor-Node-Metastasis stage (P=0.003), lymph node metastasis (P=0.001) and cancer cell remote metastasis (P=0.010) in patients with GC. The expression of TRPM8 protein was significantly higher in GC patients with a tumor diameter of ≥2.5 cm. Additionally, TRPM8 protein expression in patients with metastases was significantly higher compared with patients without metastasis. Cox regression analysis revealed that TRPM8 protein expression was an independent risk factor for prognosis (odds ratio, 1.625; 95% CI=0.552-3.128) in patients with GC. In addition, the 5-year overall survival rate of patients with high expression of TRPM8 protein (64.44%) in GC was significantly lower compared with patients with low expression (12.36%). TRPM8 was highly expressed in GC tissues and may promote GC cell proliferation and metastasis in vivo.

Transient receptor potential (TRP) channels in human colorectal cancer: evidence and perspectives

Colorectal cancer (CRC) is one of the leading causes of death in the civilized world. Transient receptor potential channels (TRPs) are a heterogeneous family of cation channels that play an important role in gastrointestinal physiology. TRPs have been linked with carcinogenesis in the colon and their role as potential therapeutic targets and prognostic biomarkers is under investigation.

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.

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.

Menthol in electronic cigarettes: A contributor to respiratory disease?

Menthol is widely used in tobacco products. This study compared the effects of menthol on human bronchial epithelium using submerged cultures, a VITROCELL® cloud chamber that provides air liquid interface (ALI) exposure without solvents or heating, and a Cultex ALI system that delivers aerosol equivalent to that inhaled during vaping. In submerged culture, menthol significantly increased calcium influx and mitochondrial reactive oxygen species (ROS) via the TRPM8 receptor, responses that were inhibited by a TRPM8 antagonist. VITROCELL® cloud chamber exposure of BEAS-2B monolayers increased mitochondrial protein oxidation, expression of the antioxidant enzyme SOD2, activation of NF-κB, and secretion of inflammatory cytokines (IL-6 and IL-8). Proteomics data collected following ALI exposure of 3D EpiAirway tissue in the Cultex showed upregulation of NRF-2-mediated oxidative stress, oxidative phosphorylation, and IL-8 signaling. Across the three platforms, menthol adversely effected human bronchial epithelium in a manner that could lead to respiratory disease.

TRPM8 Inhibition Regulates the Proliferation, Migration and ROS Metabolism of Bladder Cancer Cells

Introduction

Based on accumulating evidence, transient receptor potential (TRP) ion channels may play important roles in the occurrence and the progression of cancer. TRP melastatin 8 (TRPM8), a member of the TRP family, functions as a Ca²⁺-permeable channel and regulates various physiological and pathological processes. However, the effects of TRPM8 on bladder cancer (BCa) and its underlying mechanisms have not been elucidated.

Methods

BCa tissues and matched noncancerous tissues were collected to examine the expression of the TRPM8 mRNA and protein using qRT-PCR, Western blotting and immunofluorescence staining. Meanwhile, the effect of knockdown or inhibition of the activity of the TRPM8 protein on the proliferation, migration and ROS metabolism of bladder cancer cells was detected using the MTT assay, clonogenic survival assay, Transwell chamber migration assay, and reactive oxygen species (ROS) detection, respectively. Furthermore, a mouse model transplanted with BCa cells was established to assess tumor growth after TRPM8 expression was inhibited in vivo.

Results

Compared with the noncancerous tissues, the levels of TRPM8 in BCa tissues were significantly increased. Knockdown or inhibition of the activity of the TRPM8 protein in BCa cells reduced cell proliferation and migration. Moreover, the production of ROS was increased in cells treated with siTRPM8, which was accompanied by increased levels of Catalase, HO-1 and SOD2. Furthermore, a mouse model transplanted with the stable TRPM8-deficient T24 cell line was established, demonstrating that knockdown of TRPM8 delayed tumor growth in vivo.

Discussion

TRPM8 might play an essential for BCa tumor progression and metastasis by interfering with BCa cell proliferation, motility, ROS metabolism and migration.

How Dysregulated Ion Channels and Transporters Take a Hand in Esophageal, Liver, and Colorectal Cancer

Over the last two decades, the understanding of how dysregulated ion channels and transporters are involved in carcinogenesis and tumor growth and progression, including invasiveness and metastasis, has been increasing exponentially. The present review specifies virtually all ion channels and transporters whose faulty expression or regulation contributes to esophageal, hepatocellular, and colorectal cancer. The variety reaches from Ca²⁺, K⁺, Na⁺, and Cl^- channels over divalent metal transporters, Na⁺ or Cl^- coupled Ca²⁺, HCO₃^- and H⁺ exchangers to monocarboxylate carriers and organic anion and cation transporters. In several cases, the underlying mechanisms by which these ion channels/transporters are interwoven with malignancies have been fully or at least partially unveiled. Ca²⁺, Akt/NF-κB, and Ca²⁺- or pH-dependent Wnt/β-catenin signaling emerge as cross points through which ion channels/transporters interfere with gene expression, modulate cell proliferation, trigger epithelial-to-mesenchymal transition, and promote cell motility and metastasis. Also miRs, lncRNAs, and DNA methylation represent potential links between the misexpression of genes encoding for ion channels/transporters, their malfunctioning, and cancer. The knowledge of all these molecular interactions has provided the basis for therapeutic strategies and approaches, some of which will be broached in this review.

Transient Receptor Potential (TRP) Channels in Head-and-Neck Squamous Cell Carcinomas: Diagnostic, Prognostic, and Therapeutic Potentials

Head-and-neck squamous cell carcinomas (HNSCC) remain a leading cause of cancer morbidity and mortality worldwide. This is a largely preventable disease with smoking, alcohol abuse, and human papilloma virus (HPV) being the main risk factors. Yet, many patients are diagnosed with advanced disease, and no survival improvement has been seen for oral SCC in the past decade. Clearly, new diagnostic and prognostic markers are needed for early diagnosis and to guide therapy. Gene expression studies implied the involvement of transient receptor potential (TRP) channels in the pathogenesis of HNSCC. TRPs are expressed in normal epithelium where they play a key role in proliferation and differentiation. There is increasing evidence that the expression of TRP channels may change in HNSCC with important implications for diagnosis, prognosis, and therapy. In this review, we propose that TRP channel expression may afford a novel opportunity for early diagnosis of HNSCC and targeted molecular treatment.

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.

Identification of a natural compound, sesamin, as a novel TRPM8 antagonist with inhibitory effects on prostate adenocarcinoma

Transient receptor potential melastatin 8 (TRPM8) is a calcium ion-permeable cation channel that is used as a prognostic marker and therapeutic target for different tumor types. To identify natural selective TRPM8 antagonists, we tested 158 traditional Chinese medicine (TCM) compounds for the ability to inhibit TRPM8. Calcium mobilization assays were used to evaluate the 158 TCM compound components in HEK293 cells stably expressing TRPM8. An identified putative TRPM8 antagonist, sesamin, was further evaluated. Publicly available cancer OMICS data were used to explore the expression of TRPM8, its gene regulatory network, and the survival of patients with prostate adenocarcinoma (PRAD). The cytotoxicity and specificity of sesamin to TRPM8 were tested in HEK293/TRPM8 cells. The effect of sesamin on cell proliferation in PRAD cell lines was assessed. Sesamin selectively inhibited TRPM8 in HEK293/TRPM8 cells (IC50: 9.78 μM), and a molecular docking study confirmed the binding of sesamin to TRPM8. TRPM8 was highly overexpressed in PRAD, and high TRPM8 expression was associated with poor survival of PRAD patients. Functional network analysis suggested that TRPM8 has key effects on proliferation, survival, and invasion of prostate cancer cells. Cell proliferation assays supported these findings and showed that sesamin inhibited the proliferation of PRAD cell lines DU145 and LNCaP cells. These data revealed that abnormal TRPM8 expression is associated with PRAD and that sesamin is a new anti-PRAD candidate drug, exerting inhibitory effects on TRPM8.

Impact of radiation dose and pre-treatment pain levels on survival in dogs undergoing radiotherapy with or without chemotherapy for presumed extremity osteosarcoma

The purpose of this bi-institutional retrospective study was to determine whether survival for dogs with extremity osteosarcoma (OS) is improved through the use of stereotactic radiotherapy (SRT; a single fraction of 25 Gy, or 36 Gy total given in three consecutive daily fractions) plus chemotherapy, vs lower dose conventionally planned and delivered hypofractionated radiotherapy (CHRT; 14-20 Gy total in 1-2 consecutive daily fractions) plus chemotherapy. We also sought to determine whether baseline pain severity influences oncologic outcomes following radiotherapy for canine extremity OS. The medical records of 82 dogs undergoing radiotherapy for confirmed or presumed OS were reviewed. In dogs receiving combinations of both chemotherapy and radiotherapy, survival was significantly longer with SRT vs CHRT (median overall survival time: 350 vs 147 days; P = .031). In a univariate analysis, dogs with pulmonary metastases and high pain at the time of irradiation had short overall survival times; use of high radiation doses and chemotherapy were associated with improved survival. Separate multivariable models were built to assess the predictive nature of various factors that might influence event-free or overall survival in dogs treated with radiotherapy, with or without chemotherapy; for dogs treated with both chemotherapy and radiotherapy, overall survival times were significantly longer when baseline pain scores were 'low' (vs 'high'; hazard ratio: 0.258; P = .030), radiation doses were high (hazard ratio: 0.943; P = .034). Neither pain nor radiation dose were associated with survival in dogs treated with radiotherapy, without chemotherapy.

MiR-567 regulates proliferation and apoptosis of colorectal cancer cells by targeting TRPM8

BACKGROUND

The role of miRNAs in cancer is increasingly becoming a hot research topic. There have been relatively few studies on miR-567 in cancer, and its functional role in colorectal cancer (CRC) is still little understood.

AIM

To investigate the effect of miR-567 on proliferation and apoptosis of CRC cells and the underlying mechanism.

METHODS

qRT-PCR was used to detect the expression of miR-567 and transient receptor potential melastatin 8 (TRPM8) in the CRC cell lines SW480, SW1116, and HT29 as well as in the normal colorectal epithelial cell line NCM460. SW480 cells were transfected with miR-NC, miR-567 mimic, si-NC, si-TRPM8, miR-567 + pcDNA, or miR-567 + pcDNA-TRPM8 by using the liposome method. Cell proliferation was detected by MTT assay; cell apoptosis was detected by flow cytometry; protein expression of TRPM8, CyclinD1, p21, p23, Bcl-2, Bax, and cleaved Capase-3 was detected by Western blot; and the fluorescence activity was detected by double luciferase reporter gene assay.

RESULTS

Compared with normal colonic epithelial cells (NCM460), the expression of miR-567 was significantly decreased in CRC cells, and the expression of TRPM8 was significantly increased. Overexpression of miR-567 or inhibition of TRPM8 inhibited the proliferation and promoted apoptosis of SW480 cells. MiR-567 can inhibit the fluorescence activity of wild-type TRPM8 cells and negatively regulate the expression of TRPM8, while overexpression of TRPM8 reversed the proliferation inhibition and apoptosis-promoting effect of miR-567 overexpression in SW480 cells.

CONCLUSION

MiR-567 can inhibit the proliferation of CRC cells and promote their apoptosis via a mechanism possibly related to the targeting of TRPM8. This finding will provide a new direction for the prevention and treatment of CRC.

Circulating mRNA signature as a marker for high-risk prostate cancer

Prostate cancer (PCa) is the second most common cancer in men. The indolent course of the disease makes the treatment choice a challenge for physicians and patients. In this study, a minimally invasive method was used to evaluate the potential of molecular markers in identifying patients with aggressive disease. Cell-free plasma samples from 60 PCa patients collected before radical prostatectomy were used to evaluate the levels of expression of eight genes (AMACR, BCL2, NKX3-1, GOLM1, OR51E2, PCA3, SIM2 and TRPM8) by quantitative real-time PCR. Overexpression of AMACR, GOLM1, TRPM8 and NKX3-1 genes was significantly associated with aggressive disease characteristics, including extracapsular extension, tumor stage and vesicular seminal invasion. A trio of genes (GOLM1, NKX3-1 and TRPM8) was able to identify high-risk PCa cases (85% of sensitivity and 58% of specificity), yielding a better overall performance compared with the biopsy Gleason score and prostate-specific antigen, routinely used in the clinical practice. Although more studies are required, these circulating markers have the potential to be used as an additional test to improve the diagnosis and treatment decision of high-risk PCa patients.

Recent Progress in TRPM8 Modulation: An Update

The transient receptor potential melastatin subtype 8 (TRPM8) is a nonselective, multimodal ion channel, activated by low temperatures (<28 °C), pressure, and cooling compounds (menthol, icilin). Experimental evidences indicated a role of TRPM8 in cold thermal transduction, different life-threatening tumors, and other pathologies, including migraine, urinary tract dysfunction, dry eye disease, and obesity. Hence, the modulation of the TRPM8 channel could be essential in order to understand its implications in these pathologies and for therapeutic intervention. This short review will cover recent progress on the TRPM8 agonists and antagonists, describing newly reported chemotypes, and their application in the pharmacological characterization of TRPM8 in health and disease. The recently described structures of the TRPM8 channel alone or complexed with known agonists and PIP₂ are also discussed.

Genetic variants in the calcium signaling pathway genes are associated with cutaneous melanoma-specific survival

Remodeling or deregulation of the calcium signaling pathway is a relevant hallmark of cancer including cutaneous melanoma (CM). In this study, using data from a published genome-wide association study (GWAS) from The University of Texas M.D. Anderson Cancer Center, we assessed the role of 41,377 common single-nucleotide polymorphisms (SNPs) of 167 calcium signaling pathway genes in CM survival. We used another GWAS from Harvard University as the validation dataset. In the single-locus analysis, 1830 SNPs were found to be significantly associated with CM-specific survival (CMSS; P ≤ 0.050 and false-positive report probability ≤ 0.2), of which 9 SNPs were validated in the Harvard study (P ≤ 0.050). Among these, three independent SNPs (i.e. PDE1A rs6750552 T>C, ITPR1 rs6785564 A>G and RYR3 rs2596191 C>A) had a predictive role in CMSS, with a meta-analysis-derived hazards ratio of 1.52 (95% confidence interval = 1.19-1.94, P = 7.21 × 10-4), 0.49 (0.33-0.73, 3.94 × 10-4) and 0.67 (0.53-0.86, 0.0017), respectively. Patients with an increasing number of protective genotypes had remarkably improved CMSS. Additional expression quantitative trait loci analysis showed that these genotypes were also significantly associated with mRNA expression levels of the genes. Taken together, these results may help us to identify prospective biomarkers in the calcium signaling pathway for CM prognosis.

Cannabinoid Signaling in the Skin: Therapeutic Potential of the "C(ut)annabinoid" System

The endocannabinoid system (ECS) has lately been proven to be an important, multifaceted homeostatic regulator, which influences a wide-variety of physiological processes all over the body. Its members, the endocannabinoids (eCBs; e.g., anandamide), the eCB-responsive receptors (e.g., CB₁, CB₂), as well as the complex enzyme and transporter apparatus involved in the metabolism of the ligands were shown to be expressed in several tissues, including the skin. Although the best studied functions over the ECS are related to the central nervous system and to immune processes, experimental efforts over the last two decades have unambiguously confirmed that cutaneous cannabinoid ("c[ut]annabinoid") signaling is deeply involved in the maintenance of skin homeostasis, barrier formation and regeneration, and its dysregulation was implicated to contribute to several highly prevalent diseases and disorders, e.g., atopic dermatitis, psoriasis, scleroderma, acne, hair growth and pigmentation disorders, keratin diseases, various tumors, and itch. The current review aims to give an overview of the available skin-relevant endo- and phytocannabinoid literature with a special emphasis on the putative translational potential, and to highlight promising future research directions as well as existing challenges.

Expression of TRPM8 in human reactive lymphoid tissues and mature B-cell neoplasms

Transient receptor potential melastatin 8 (TRPM8) is a member of the transient receptor potential superfamily of Ca²⁺ channels. The aim of the present study was to clarify TRPM8 expression in reactive lymphoid tissues and mature B-cell neoplasms. Reactive and neoplastic lymphoid tissues were used to evaluate TRPM8 expression by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). TRPM8⁺ cells were frequently detected in the follicular light zone and marginal zone of reactive lymphoid tissues. Double immunostaining revealed that TRPM8⁺ cells co-expressed cluster of differentiation (CD) 38, CD79a, CD138, interferon regulatory factor 4/melanoma associated antigen (mutated) 1, B cell CLL/lymphoma 6 and transmembrane activator and CAML interactor. TRPM8⁺ neoplastic cells were frequently detected in plasma cell myeloma. The positive band of TRPM8 mRNA was confirmed by RT-PCR in cases of myeloma. The present study is, to the best of our knowledge, the first to demonstrate the expression of TRPM8 in reactive lymphoid tissues and mature B-cell neoplasms, revealing that TRPM8 is frequently expressed in pre-plasmablasts, plasmablasts, plasma cells and mature B-cell lymphomas that are likely to differentiate into plasma cells.

Transient Receptor Potential (TRP) Channels

Transient Receptor Potential (TRP) channels are evolutionarily conserved integral membrane proteins. The mammalian TRP superfamily of ion channels consists of 28 cation permeable channels that are grouped into six subfamilies based on sequence homology (Fig. 6.1). The canonical TRP (TRPC) subfamily is known for containing the founding member of mammalian TRP channels. The vanilloid TRP (TRPV) subfamily has been extensively studied due to the heat sensitivity of its founding member. The melastatin-related TRP (TRPM) subfamily includes some of the few known bi-functional ion channels, which contain functional enzymatic domains. The ankyrin TRP (TRPA) subfamily consists of a single chemo-nociceptor that has been proposed to be a target for analgesics. The mucolipin TRP (TRPML) subfamily channels are found primarily in intracellular compartments and were discovered based on their critical role in type IV mucolipidosis (ML-IV). The polycystic TRP (TRPP) subfamily is a diverse group of proteins implicated in autosomal dominant polycystic kidney disease (ADPKD). Overall, this superfamily of channels is involved in a vast array of physiological and pathophysiological processes making the study of these channels imperative to our understanding of subcellular biochemistry.

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.

TRPM Family Channels in Cancer

Members of the TRPM ("Melastatin") family fall into the subclass of the TRP channels having varying permeability to Ca²⁺ and Mg²⁺, with three members of the TRPM family being chanzymes, which contain C-terminal enzyme domains. The role of different TRPM members has been shown in various cancers such as prostate cancer for mostly TRPM8 and TRPM2, breast cancer for mostly TRPM2 and TRPM7, and pancreatic cancer for TRPM2/7/8 channels. The role of TRPM5 channels has been shown in lung cancer, TRPM1 in melanoma, and TRPM4 channel in prostate cancer as well. Thus, the TRPM family of channels may represent an appealing target for the anticancer therapy.

Sensitization of TRPV1 and TRPA1 via peripheral mGluR5 signaling contributes to thermal and mechanical hypersensitivity

Peripheral tissue inflammation or injury causes glutamate release from nociceptive axons, keratinocytes, and Schwann cells, resulting in thermal hypersensitivity. However, the detailed molecular mechanisms underlying glutamate-induced thermal hypersensitivity are unknown. The aim of this study was to clarify the involvement of peripheral transient receptor potential (TRP) TRP vanilloid 1 (TRPV1), TRP ankyrin 1 (TRPA1), and protein kinase C epsilon (PKCε) in glutamate-induced pain hypersensitivity. The amount of glutamate in the facial tissue was significantly increased 3 days after facial Complete Freund's adjuvant injection. The head-withdrawal reflex threshold to heat, cold, or mechanical stimulation was significantly decreased on day 7 after continuous glutamate or metabotropic glutamate receptor 5 (mGluR5) agonist (CHPG) injection into the facial skin compared with vehicle-injected rats, and glutamate-induced hypersensitivity was significantly recovered by mGluR5 antagonist MTEP, TRPA1 antagonist HC-030031, TRPV1 antagonist SB366791, or PKCε translocation inhibitor administration into the facial skin. TRPV1 and TRPA1 were expressed in mGluR5-immunoreactive (IR) trigeminal ganglion (TG) neurons innervating the facial skin, and mGluR5-IR TG neurons expressed PKCε. There was no significant difference in the number of GluR5-IR TG neurons among glutamate-injected, saline-injected, and naive rats, whereas that of TRPV1- or TRPA1-IR TG neurons was significantly increased 7 days after continuous glutamate injection into the facial skin compared with vehicle injection. PKCε phosphorylation in TG was significantly enhanced following glutamate injection into the facial skin. Moreover, neuronal activity of TG neurons was significantly increased following facial glutamate treatment. The present findings suggest that sensitization of TRPA1 and/or TRPV1 through mGluR5 signaling via PKCε is involved in facial thermal and mechanical hypersensitivity.

Decreased TRPM7 inhibits activities and induces apoptosis of bladder cancer cells via ERK1/2 pathway

Transient receptor potential melastatin 7 (TRPM7) functions as a Mg²⁺/Ca²⁺-permeable channel fused with a kinase domain and regulates various physical processes and diseases. However, its effects on pathogenesis of human bladder cancer (BCa) has not been clarified yet. Our microarray analysis has suggested that calcium signaling pathway is connected with bladder cancer via MAPK pathway. Therefore, we aim to investigate the mechanism of TRPM7 in BCa tumorigenesis by using BCa tissues compared with normal bladder epithelium tissues, as well as using distinct BCa cell lines (EJ, 5637 and T24). We observed increased TRPM7 expression and dysregulation of proteins involved in Epithelial-Mesenchymal Transition (EMT) in BCa tissues. Moreover, knockdown of TRPM7 in BCa cells reversed the EMT status, accompanied by increase of reactive oxygen species (ROS). Furthermore, TRPM7 deficiency could inhibit BCa cell proliferation, migration and invasion, as well as induce p-ERK1/2 and suppress PI3K/AKT at the protein level. Downregulation of TRPM7 promoted cell cycle arrest at G0/G1 phase and apoptosis in vitro, which could be recovered by pre-treatment with U0126 to deactivate ERK1/2, suggesting a close correlation between TRPM7 and the MAPK signaling pathway. Furthermore, a NOD/SCID mouse model transplanted using the BCa cells was established, revealing delayed tumor growth by reduced protein activity and mRNA transcription of TRPM7 in vivo. Our results suggested TRPM7 might be essential for BCa tumorigenesis by interfering BCa cell proliferation, motility and apoptosis.

RHCG and TCAF1 promoter hypermethylation predicts biochemical recurrence in prostate cancer patients treated by radical prostatectomy

PURPOSE

The lack of biomarkers that can distinguish aggressive from indolent prostate cancer has caused substantial overtreatment of clinically insignificant disease. Here, by genome-wide DNA methylome profiling, we sought to identify new biomarkers to improve the accuracy of prostate cancer diagnosis and prognosis.

EXPERIMENTAL DESIGN

Eight novel candidate markers, COL4A6, CYBA, TCAF1 (FAM115A), HLF, LINC01341 (LOC149134), LRRC4, PROM1, and RHCG, were selected from Illumina Infinium HumanMethylation450 BeadChip analysis of 21 tumor (T) and 21 non-malignant (NM) prostate specimens. Diagnostic potential was further investigated by methylation-specific qPCR analysis of 80 NM vs. 228 T tissue samples. Prognostic potential was assessed by Kaplan-Meier, uni- and multivariate Cox regression analysis in 203 Danish radical prostatectomy (RP) patients (cohort 1), and validated in an independent cohort of 286 RP patients from Switzerland and the U.S. (cohort 2).

RESULTS

Hypermethylation of the 8 candidates was highly cancer-specific (area under the curves: 0.79-1.00). Furthermore, high methylation of the 2-gene panel RHCG-TCAF1 was predictive of biochemical recurrence (BCR) in cohort 1, independent of the established clinicopathological parameters Gleason score, pathological tumor stage, and pre-operative PSA (HR (95% confidence interval (CI)): 2.09 (1.26 - 3.46); P = 0.004), and this was successfully validated in cohort 2 (HR (95% CI): 1.81 (1.05 - 3.12); P = 0.032).

CONCLUSION

Methylation of the RHCG-TCAF1 panel adds significant independent prognostic value to established prognostic parameters for prostate cancer and thus may help to guide treatment decisions in the future. Further investigation in large independent cohorts is necessary before translation into clinical utility.

Menthol evokes Ca2+ signals and induces oxidative stress independently of the presence of TRPM8 (menthol) receptor in cancer cells

Menthol is a naturally occurring monoterpene alcohol possessing remarkable biological properties including antipruritic, analgesic, antiseptic, anti-inflammatory and cooling effects. Here, we examined the menthol-evoked Ca²⁺ signals in breast and prostate cancer cell lines. The effect of menthol (50–500 µM) was predicted to be mediated by the transient receptor potential ion channel melastatin subtype 8 (TRPM8). However, the intensity of menthol-evoked Ca²⁺ signals did not correlate with the expression levels of TRPM8 in breast and prostate cancer cells indicating a TRPM8-independent signaling pathway. Menthol-evoked Ca²⁺ signals were analyzed in detail in Du 145 prostate cancer cells, as well as in CRISPR/Cas9 TRPM8-knockout Du 145 cells. Menthol (500 µM) induced Ca²⁺ oscillations in both cell lines, thus independent of TRPM8, which were however dependent on the production of inositol trisphosphate. Results based on pharmacological tools point to an involvement of the purinergic pathway in menthol-evoked Ca²⁺ responses. Finally, menthol (50–500 µM) decreased cell viability and induced oxidative stress independently of the presence of TRPM8 channels, despite that temperature-evoked TRPM8-mediated inward currents were significantly decreased in TRPM8-knockout Du 145 cells compared to wild type Du 145 cells.

Do estrogens enhance activation of brown and beiging of adipose tissues?

Obesity and its associated co-morbidities are worldwide public health concerns. Obesity is characterized by excessive adipose tissue accumulation; however, it is important to recognize that human and rodent adipose tissues are made up of several distinct adipose tissue sub-types. White adipose tissue (WAT) is considered the prototypical fat cell, due to its capacity and capability to store large amounts of lipid. In contrast, brown adipose tissue (BAT) oxidizes substrates to generate heat. BAT contains more mitochondria than WAT and express uncoupling protein-1 (UCP1), which mediates BAT thermogenesis. A third sub-type of adipose tissue, Brown-in-white (BRITE)/beige adipocytes arise from WAT upon adrenergic stimulation and resembles BAT functionally. The energy burning feature of BAT/beige cells, combined with evidence of an inverse-correlation between BAT/beige adipose tissue and obesity have given rise to the hypothesis that obesity may be linked to BAT/beige 'malfunction'. Females have more BAT and perhaps an enhanced capacity to beige their adipose tissue when compared to males. Multiple signal pathways are capable of activating BAT thermogenesis and beiging of WAT; here, we discuss the potential role of estrogens in enhancing and mediating these factors to enhance adipose tissue thermogenesis.

TRPM channels as potential therapeutic targets against pro-inflammatory diseases

The immune system protects our body against foreign pathogens. However, if it overshoots or turns against itself, pro-inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, or diabetes develop. Ions, the most basic signaling molecules, shape intracellular signaling cascades resulting in immune cell activation and subsequent immune responses. Mutations in ion channels required for calcium signaling result in human immunodeficiencies and highlight those ion channels as valued targets for therapies against pro-inflammatory diseases. Signaling pathways regulated by melastatin-like transient receptor potential (TRPM) cation channels also play crucial roles in calcium signaling and leukocyte physiology, affecting phagocytosis, degranulation, chemokine and cytokine expression, chemotaxis and invasion, as well as lymphocyte development and proliferation. Therefore, this review discusses their regulation, possible interactions and whether they can be exploited as targets for therapeutic approaches to pro-inflammatory diseases.

Cutaneous Penetration-Enhancing Effect of Menthol: Calcium Involvement

Menthol is a naturally occurring terpene used as a penetration enhancer in topical and transdermal formulations. Literature shows a growing interest in menthol's interactions with the transient receptor potential melastatin 8. A decrease in extracellular Ca²⁺ due to the activation of the transient receptor potential melastatin 8 receptor produces inhibition of E-cadherin expression that is responsible for cell-cell adhesion. Because calcium is present in the entire epidermis, the purpose of this study is to evaluate whether the aforementioned properties of menthol are also related to its penetration-enhancing effects. We formulated 16 gels: (i) drug-alone (diphenhydramine or lidocaine), (ii) drug with menthol, (iii) drug, menthol, and calcium channel blocker (CCB; verapamil or diltiazem), and (iv) drug and CCB. In vitro studies showed no effect of the CCB on the release of the drugs either with or without menthol. In vivo experiments were performed for each drug/menthol/CCB combination gel by applying 4 formulations on a shaved rabbit's dorsum on the same day. Dermis concentration profiles were assessed with microdialysis. The gels containing menthol showed higher penetration of drugs than those without whereas the addition of the CCB consistently inhibited the penetration-enhancing effects of menthol. In summary, these findings strongly support the involvement of calcium in the penetration-enhancing effect of menthol.

TRPM8 and Migraine

Migraine is among the most common diseases on earth and one of the most disabling, the latter due in large part to poor treatment efficacy. Development of new therapeutics is dependent on the identification of mechanisms contributing to migraine and discovery of targets for new drugs. Numerous genome-wide association studies (GWAS) have implicated the transient receptor-potential M8 (TRPM8) channel in migraine. This channel is predominantly expressed on peripheral sensory neurons and is known as the sensor for cold temperature in cutaneous tissue but is also expressed on deep visceral afferents where cold is not likely a stimulus. Consequently, a number of alternative endogenous agonists have been proposed. Apart from its role in cold sensation, TRPM8 also contributes to cold allodynia after nerve injury or inflammation, and it is necessary for cooling/menthol-based analgesia. How it might contribute to migraine is less clear. The purpose of this review is to discuss the anatomical and physiological mechanisms by which meningeal TRPM8 may play a role in migraine as well as the potential of TRPM8 as a therapeutic target. TRPM8 is expressed on sensory afferents innervating the meninges, and these neurons are subject to developmental changes that may influence their contribution to migraine. As in viscera, meningeal TRPM8 channels are unlikely to be activated by temperature fluctuations and their endogenous ligands remain unknown. Preclinical migraine studies show that activation of meningeal TRPM8 by exogenous agonists can both cause and alleviate headache behaviors, depending on whether other meningeal afferents concurrently receive noxious stimuli. This is reminiscent of the fact that cold can trigger migraine in humans but menthol can also alleviate headache. We propose that both TRPM8 agonists and antagonists may be potential therapeutics, depending on how migraine is triggered in individual patients. In this regard, TRPM8 may be a novel target for personalized medicine in migraine treatment.