T-type Ca 2+ Channels: T for Targetable

Induction of Ca2+-dependent autophagy and concurrent lysosomal alkalinization underlies the cytotoxic effects of NNC-55-0396 on glioblastoma cells

Diverse agents targeting (macro)autophagy, a critical metabolic stress response in cancer cells, have been proposed for cancer therapy. In previous studies, we showed that NNC-55-0396 (NNC) induces glioblastoma cell death by activating the Unfolded Protein Response (UPR) of ER stress and increasing cytosolic Ca2+ levels. Here, we report that NNC affects both ends of the autophagy process, causing extensive cytoplasmic vacuolation. Our results show that: (1) NNC induces autophagy downstream of UPR and Ca2+ signaling pathways, thus silencing IRE1α/JNK1 or inhibiting Ca2+/IP3R signaling prevents NNC-induced vacuolation. (2) Silencing ATG5 delays cell death, indicating that autophagy induction plays a role in NNC's cytotoxic effects. (3) NNC and other Ca2+-mobilizing agents transcriptionally upregulate p62/SQSTM1, an autophagosome cargo receptor, highlighting a role for this protein in the response to NNC. (4) Studies using tandem fluorescent-tagged LC3 and electron microscopy, however, further reveal that NNC blocks late-stage autophagy that leads to enlarged degradative compartments accumulating ubiquitin-tagged cargoes. (5) Finally, NNC impedes pro-cathepsin-B processing, an effect that is reversed with a weak acid co-treatment, suggesting that lysosomal dysfunction due to increased intraluminal pH is the underlying cause of the autophagy blockade. Together, these findings underscore a multi-level dysregulation of autophagy that contributes to NNC's anti-tumoral effects.

Blockade of CaV3 calcium channels and induction of G0/G1 cell cycle arrest in colon cancer cells by gossypol

BACKGROUND AND PURPOSE

Gastrointestinal tumours overexpress voltage-gated calcium (CaV3) channels (CaV3.1, 3.2 and 3.3). CaV3 channels regulate cell growth and apoptosis colorectal cancer. Gossypol, a polyphenolic aldehyde found in the cotton plant, has anti-tumour properties and inhibits CaV3 currents. A systematic study was performed on gossypol blocking mechanism on CaV3 channels and its potential anticancer effects in colon cancer cells, which express CaV3 isoforms.

EXPERIMENTAL APPROACH

Transcripts for CaV3 proteins were analysed in gastrointestinal cancers using public repositories and in human colorectal cancer cell lines HCT116, SW480 and SW620. The gossypol blocking mechanism on CaV3 channels was investigated by combining heterologous expression systems and patch-clamp experiments. The anti-tumoural properties of gossypol were estimated by cell proliferation, viability and cell cycle assays. Ca2+ dynamics were evaluated with cytosolic and endoplasmic reticulum (ER) Ca2+ indicators.

KEY RESULTS

High levels of CaV3 transcripts correlate with poor prognosis in gastrointestinal cancers. Gossypol blockade of CaV3 isoforms is concentration- and use-dependent interacting with the closed, activated and inactivated conformations of CaV3 channels. Gossypol and CaV3 channels down-regulation inhibit colorectal cancer cell proliferation by arresting cell cycles at the G0/G1 and G2/M phases, respectively. CaV3 channels underlie the vectorial Ca2+ uptake by endoplasmic reticulum in colorectal cancer cells.

CONCLUSION AND IMPLICATIONS

Gossypol differentially blocked CaV3 channel and its anticancer activity was correlated with high levels of CaV3.1 and CaV3.2 in colorectal cancer cells. The CaV3 regulates cell proliferation and Ca2+ dynamics in colorectal cancer cells. Understanding this blocking mechanism maybe improve cancer therapies.

The mmu_circ_003062, hsa_circ_0075663/miR-490-3p/CACNA1H axis mediates apoptosis in renal tubular cells in association with endoplasmic reticulum stress following ischemic acute kidney injury

BACKGROUND

While recent studies have suggested a potential involvement of circRNAs in acute kidney injury (AKI) after ischemia, mmu_circ_003062 role is undetermined.

METHODS

The levels of mmu_circ_003062, miR-490-3p, CACNA1H, GRP78, CHOP and hsa_circ_0075663 were detected by Relative qPCR in Boston University mouse proximal tubule (BUMPT) cells, mouse kidneys, and human renal tubular epithelial (HK-2) cells. Moreover, the levels of hsa_circ_0075663 in serum and urine of patients with AKI following cardiopulmonary resuscitation (CPR) were detected by absolute quantitative PCR. Western blot was used to detect the relative expression of the protein. The function and regulatory mechanism of mmu_circ_003062 and hsa_circ_0075663 were investigated through a series of in vitro and in vivo experiments, including bioinformatic prediction, luciferase reporter assays, FISH, FCM, TUNEL staining, and H&E staining.

RESULTS

It was found that mmu_circ_003062, hsa_circ_0075663 mediated apoptosis after ischemia/reperfusion (I/R) by interaction with miR-490-3p to enhance CACNA1H expression, thereby leading to the upregulation of endoplasmic reticulum stress (ERS)-relevant proteins GRP78 and CHOP. Ultimately, mmu_circ_003062 downregulation significantly ameliorated ischemic AKI by modulating the miR-490-3p/CACNA1H/GRP78 and CHOP pathway. Furthermore, the plasma and urinary levels of hsa_circ_0075663 in patients with AKI following CPR were significantly higher than non-AKI patients, exhibited a strongly correlation with serum creatinine.

CONCLUSION

The involvement of mmu_circ_003062, hsa_circ_0075663/miR-490-3p/CACNA1H/GRP78 and CHOP axis is significant in the development of ischemic AKI. Moreover, hsa_circ_0075663 has potential as an early diagnostic biomarker.

Tetralol derivative NNC-55-0396 targets hypoxic cells in the glioblastoma microenvironment: an organ-on-chip approach

Glioblastoma (GBM) is a highly malignant brain tumour characterised by limited treatment options and poor prognosis. The tumour microenvironment, particularly the central hypoxic region of the tumour, is known to play a pivotal role in GBM progression. Cells within this region adapt to hypoxia by stabilising transcription factor HIF1-α, which promotes cell proliferation, dedifferentiation and chemoresistance. In this study we sought to examine the effects of NNC-55-0396, a tetralol compound which overactivates the unfolded protein response inducing apoptosis, using the organ-on-chip technology. We identified an increased sensitivity of the hypoxic core of the chip to NNC, which correlates with decreasing levels of HIF1-α in vitro. Moreover, NNC blocks the macroautophagic process that is unleashed by hypoxia as revealed by increased levels of autophagosomal constituent LC3-II and autophagy chaperone p62/SQSTM1. The specific effects of NNC in the hypoxic microenvironment unveil additional anti-cancer abilities of this compound and further support investigations on its use in combined therapies against GBM.

KTt-45, a T-type calcium channel blocker, acts as an anticancer agent by inducing apoptosis on HeLa cervical cancer cell line

The abnormal expression in the T-type calcium channels is involved in various cancer types, thus inhibiting T-type calcium channels is one of approaches in cancer treatment. The fact that KTt-45 acted as a T-type calcium channel inhibitor as well as a pain-relief agent prompts us to address if KTt-45 plays any role against cancer cells. The results showed that KTt-45 caused cytotoxic effects towards HeLa cervical, Raji lymphoma, MCF-7 breast cancer, and A549 lung cancer cell lines with IC50 values less than 100 μM, in which highly selective toxicity was against HeLa cells (IC50 = 37.4 μM, SI > 3.2). Strikingly, the KTt-45 induced an accumulation of cytoplasmic vacuoles after 48 h treatment and mitochondrial-dependent apoptosis activation as evidenced by morphological features, chromatin condensation, nuclear fragmentation, and significant activation of caspase-9 as well as caspase-3. In conclusion, KTt-45 could inhibit cell growth and trigger mitochondrial-dependent apoptosis in HeLa cervical cancer cells. The results, taken together, strongly demonstrated that KTt-45 is a potential agent for further study on anticancer drug development which not only targets cancer cells but also helps to relieve neuropathic pain in cancer patients.

Ion channels and their role in chemo-resistance

Ion channels play a crucial role in cellular signaling, homeostasis, and generation of electrical and chemical signals. Aberrant expression and dysregulation of ion channels have been associated with cancer development and resistance to conventional cancer treatment such as chemotherapy. Several molecular mechanisms have been proposed to explain this phenomenon. Including evasion of apoptosis, decreased drug accumulation in cancer cells, detoxifying and activation of alternative escape pathways such as autophagy. Each of these mechanisms leads to a reduction of the therapeutic efficacy of administered drugs, causing more difficulty in cancer treatment. This review highlights the linkages between ion channels and resistance to chemotherapy. Furthermore, it elaborates their molecular mechanisms and the potential of being therapeutic targets in clinical management.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.

Inactivation of CACNA1H induces cell apoptosis by initiating endoplasmic reticulum stress in glioma

Background

Ca²⁺ channels are abnormally expressed in various tumor cells and are involved in the progression of human glioma. Here, we explored the role of a calcium channel, voltage-dependent, T-type, alpha 1H subunit (CACNA1H), which encodes T-type Ca²⁺ channel Cav3.2 in glioma cells.

Methods

Cell viability and apoptosis were detected using cell-counting kit-8 and flow cytometry, respectively. The expression of target protein was determined using western blot analysis.

Results

Cell viability of U251 cells was inhibited significantly after the knockdown of CACNA1H. The apoptosis of U251 cells was enhanced significantly after the knockdown of CACNA1H. Importantly, knockdown of CACNA1H decreased the levels of p-PERK, GRP78, CHOP, and ATF6, indicating that CACNA1H knockdown activated endoplasmic reticulum stress (ERS) in U251 cells. In addition, T-type Ca²⁺ channel inhibitor NNC55-0396 also induced apoptosis through the activation of ERS in U251 cells. ERS inhibitor UR906 could block CACNA1H inhibitor ABT-639-induced apoptosis.

Conclusion

Suppression of CACNA1H activated the ERS and thus induced apoptosis in glioma cells. T-type Ca²⁺ channel inhibitors ABT-639 and NNC55-0396 also induced apoptosis through ERS in glioma cells. Our data highlighted the effect of CACNA1H as an oncogenic gene in human glioma.

Androgen receptor signaling-mitochondrial DNA-oxidative phosphorylation: A critical triangle in early prostate cancer

Mitochondria are more than just the cellular powerhouse. They also play key roles in vital functions such as apoptosis, metabolism regulation, and other intracellular interactions. The mitochondrial DNA (mtDNA) encodes for 12 subunits of the oxidative phosphorylation (OXPHOS) system. Depletion of mtDNA in androgen-dependent prostate cancer (PCa) cell lines renders them androgen-independent and more aggressive. Paradoxically, pharmaceutical inhibition of OXPHOS is lethal for subsets of PCa cells, whereas others become dependent on androgen receptor (AR) signaling for survival. Given that the AR-mitochondria interaction is critical for early PCa, it is crucial to understand the details of this interaction. Technical hurdles have made mitochondria traditionally difficult to study, with many techniques used for isolation masking the properties of given individual mitochondria. Although the isolation of mitochondria enables us to study OXPHOS, we miss the context in which mitochondria interact with the rest of the cell. Both AR signaling and mtDNA affect apoptosis, metabolism regulation, cellular calcium storage and homeostasis, intracellular calcium signaling, and redox homeostasis. In this review, we will attempt to understand how the crosstalk between AR-mtDNA-OXPHOS is responsible for "life or death" decisions inside the cells. Our aim is to point toward potential vulnerabilities that can lead to the discovery of novel therapeutic targets.

T-Type Calcium Channels: A Mixed Blessing

The role of T-type calcium channels is well established in excitable cells, where they preside over action potential generation, automaticity, and firing. They also contribute to intracellular calcium signaling, cell cycle progression, and cell fate; and, in this sense, they emerge as key regulators also in non-excitable cells. In particular, their expression may be considered a prognostic factor in cancer. Almost all cancer cells express T-type calcium channels to the point that it has been considered a pharmacological target; but, as the drugs used to reduce their expression are not completely selective, several complications develop, especially within the heart. T-type calcium channels are also involved in a specific side effect of several anticancer agents, that act on microtubule transport, increase the expression of the channel, and, thus, the excitability of sensory neurons, and make the patient more sensitive to pain. This review puts into context the relevance of T-type calcium channels in cancer and in chemotherapy side effects, considering also the cardiotoxicity induced by new classes of antineoplastic molecules.

T-type channels in cancer cells: Driving in reverse

In the strongly polarized membranes of excitable cells, activation of T-type Ca²⁺ channels (TTCCs) by weak depolarizing stimuli allows the influx of Ca²⁺ which further amplifies membrane depolarization, thus "recruiting" higher threshold voltage-gated channels to promote action potential firing. Nonetheless, TTCCs perform other functions in the plasma membrane of both excitable and non-excitable cells, in which they regulate a number of biochemical pathways relevant for cell cycle and cell fate. Furthermore, data obtained in the last 20 years have shown the involvement of TTCCs in tumor biology, designating them as promising chemotherapeutic targets. However, their activity in the steadily-depolarized membranes of cancer cells, in which most voltage-gated channels are in the inactivated (nonconducting) state, is counter-intuitive. Here we discuss that in cancer cells weak hyperpolarizing stimuli increase the fraction of open TTCCs which, in association with Ca²⁺-dependent K⁺ channels, may critically boost membrane hyperpolarization and driving force for Ca²⁺ entry through different voltage-independent Ca²⁺ channels. Available evidence also shows that TTCCs participate in positive feedback circuits with signaling effectors, which may warrant a switch-like activation of pro-proliferative and pro-survival pathways in spite of their low availability. Unravelling TTCC modus operandi in the context of non-excitable membranes may facilitate the development of novel anticancer approaches.

Tetralol derivative NNC-55-0396 induces glioblastoma cell death by activating IRE1α, JNK1 and calcium signaling

Mibefradil and NNC-55-0396, tetralol derivatives with a proven -ability to block T-type calcium channels in excitable cells, reduce cancer cell viability in vitro, causing cell death. Furthermore, they reduce tumor growth in preclinical models of Glioblastoma multiforme (GBM), a brain tumor of poor prognosis. Here we found that GBM cells treated with cytotoxic concentrations of NNC-55-0396 paradoxically increased cytosolic calcium levels through the activation of inositol triphosphate receptors (IP₃R) and ER stress. We used pharmacological inhibitors and gene silencing to dissect the cell death pathway stimulated by NNC-55-0396 in GBM cell lines and biopsy-derived cultures. Calcium chelation or IP₃R inhibition prevented NNC-55-0396-mediated cytotoxicity, indicating that ER calcium efflux is the cause of cell death. Upstream of calcium mobilization, NNC-55-0396 activated the IRE1α arm of the Unfolded Protein Response (UPR) resulting in the nuclear translocation of pro-apoptotic CHOP. Consistent with these findings, silencing IRE1α or JNK1 rescued the cell death elicited by NNC-55-0396. Therefore, we demonstrate that activation of IRE1α and calcium signaling accounts for the cytotoxicity of NNC-55-0396 in GBM cells. The delineation of the signaling pathway that mediates the abrupt cell death triggered by this compound can help the development of new therapies for GBM.

Ion Channel Involvement in Tumor Drug Resistance

Over 90% of deaths in cancer patients are attributed to tumor drug resistance. Resistance to therapeutic agents can be due to an innate property of cancer cells or can be acquired during chemotherapy. In recent years, it has become increasingly clear that regulation of membrane ion channels is an important mechanism in the development of chemoresistance. Here, we review the contribution of ion channels in drug resistance of various types of cancers, evaluating their potential in clinical management. Several molecular mechanisms have been proposed, including evasion of apoptosis, cell cycle arrest, decreased drug accumulation in cancer cells, and activation of alternative escape pathways such as autophagy. Each of these mechanisms leads to a reduction of the therapeutic efficacy of administered drugs, causing more difficulty in cancer treatment. Thus, targeting ion channels might represent a good option for adjuvant therapies in order to counteract chemoresistance development.

Targeting T-type channels in cancer: What is on and what is off?

Over the past 20 years, various studies have demonstrated a pivotal role of T-type calcium channels (TTCCs) in tumor progression. Cytotoxic effects of TTCC pharmacological blockers have been reported in vitro and in preclinical models. However, their roles in cancer physiology are only beginning to be understood. In this review, we discuss evidence for the signaling pathways and cellular processes stemming from TTCC activity, mainly inferred by inverse reasoning from pharmacological blocks and, only in a few studies, by gene silencing or channel activation. A thorough analysis indicates that drug-induced cytotoxicity is partially an off-target effect. Dissection of on/off-target activity is paramount to elucidate the physiological roles of TTCCs, and to deliver efficacious therapies suited to different cancer types and stages.

ML218 HCl Is More Efficient Than Capsaicin in Inhibiting Bacterial Antigen-Induced Cal 27 Oral Cancer Cell Proliferation

The bacterial antigen, lipopolysaccharide (LPS) and disruptions in calcium channels are independently known to influence oral cancer progression. Previously, we found that bacterial antigens, LPS and lipoteichoic acid (LTA) act as confounders during the action of capsaicin on Cal 27 oral cancer proliferation. As calcium channel drugs may affect oral cancer cell proliferation, we investigated the effect of ML218 HCl, a T-type voltage-gated calcium channel blocker, on the proliferation of Cal 27 oral cancer cells. We hypothesized that ML218 HCl could effectively reduce LPS-induced oral cancer cell proliferation. LPS and LTA antigens were added to Cal 27 oral cancer cells either prior to and/or concurrently with ML218 HCl treatment, and the efficacy of the treatment was evaluated by measuring Cal 27 proliferation, cell death and apoptosis. ML218 HCl inhibited oral cancer cell proliferation, increased apoptosis and cell death, but their efficacy was significantly reduced in the presence of bacterial antigens. ML218 HCl proved more effective than capsaicin in reducing bacterial antigen-induced Cal 27 oral cancer cell proliferation. Our results also suggest an interplay of proliferation factors during the bacterial antigens and calcium channel drug interaction in Cal 27. Bacterial antigen reduction of drug efficacy should be considered for developing newer pharmacological agents or testing the efficacy of the existing oral cancer chemotherapeutic agents. Finally, voltage gated calcium channel drugs should be considered for future oral cancer research.

Advances in Intracellular Calcium Signaling Reveal Untapped Targets for Cancer Therapy

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

Structural optimization, synthesis and in vitro synergistic anticancer activities of combinations of new N3-substituted dihydropyrimidine calcium channel blockers with cisplatin and etoposide

T-type calcium channels are considered potential drug targets to combat cancer. Combining T-type calcium channel blockers with conventional chemotherapy drugs represents a promising strategy towards successful cancer treatment. From this perspective, we report in this study the design and synthesis of a novel series of N3-sustituted dihydropyrimidines (DHPMs) as anticancer adjuvants to cisplatin (Cis) and etoposide (Eto). Full spectral characterization of the new compounds was done using FT-IR, ¹H NMR, ¹³C NMR, and HRMS. Structure elucidation was confirmed by 2D NMR ¹H-H COSY, HSQC and NOESY experiments. Novel derivatives were tested for their Ca²⁺ channel blocking activity by employing the whole cell patch-clamp technique. Results demonstrated that most compounds were potential T-type calcium channel blockers with the triazole-based C12 and C13 being the most selective agents against Ca_V3.2 channel. Further electrophysiological studies demonstrated that C12 and C13 inhibited Ca_V3.2 currents with respective affinity of 2.26 and 1.27 µM, and induced 5 mV hyperpolarizing shifts in the half-inactivation potential. Subsequently, C12 and C13 were evaluated for their anticancer activities alone and in combination with Cis and Eto against A549 and MDA-MB 231 cancer cells. Interestingly, both compounds exhibited potential anticancer effects with IC₅₀ values < 5 µM. Combination studies revealed that both compounds had synergistic effects (combination index CI < 1) on Cis and Eto through induction of apoptosis (p53 activation and up-regulation of BAX and p21 gene expression). Importantly, in silico physicochemical and ADMET assessment of both compounds revealed their potential drug-like properties with decreased risk of cardiac toxicity. Hence, C12 and C13 are promising anticancer adjuvants through inhibition of Ca_V3.2 T-type calcium channels, thereby serving as eminent leads for further modification.

Improved tumor-suppressive effect of OZ-001 combined with cisplatin mediated by mTOR/p70S6K and STAT3 inactivation in A549 human lung cancer cells

We previously reported the anticancer activity of 4-(4-fluorobenzylcarbamoylmethyl)-3-(4-cyclohexylphenyl)-2-[3-(N,N-dimethylureido)-N'-methylpropylamino]-3,4-dihydroquinazoline (OZ-001), a T-type calcium channel (TTCC) blocker, against non-small cell lung cancer (NSCLC) in vitro and in vivo. Here, we evaluated the synergistic effect of OZ-001 and cisplatin on A549 human lung cancer cells and A549 xenograft mice. Our study demonstrated that treatment with OZ-001 and cisplatin sensitized A549 cells to cisplatin and significantly inhibited cell growth, increased the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, and induced poly (ADP-ribose) polymerase (PARP) cleavage in A549 cells and an A549 xenograft tumor mouse model. Moreover, our findings showed that mechanistic target of rapamycin (mTOR), ribosomal protein S6 kinase (p70S6K), and signal transducer and activator of transcription (STAT3) inactivation was required for apoptosis induced by the combination of OZ-001 and cisplatin in in vitro and in vivo experiments. Our results suggest that combined treatment with OZ-001 and cisplatin could potentiate antiproliferative effects via suppression of the mTOR/p70S6K and STAT3 pathways and may be considered a potential therapeutic agent for NSCLC.

Evaluation of the effects of the T-type calcium channel enhancer SAK3 in a rat model of TAF1 deficiency

The TATA-box binding protein associated factor 1 (TAF1) is part of the TFIID complex that plays a key role during the initiation of transcription. Variants of TAF1 are associated with neurodevelopmental disorders. Previously, we found that CRISPR/Cas9 based editing of the TAF1 gene disrupts the morphology of the cerebral cortex and blunts the expression as well as the function of the CaV3.1 (T-type) voltage gated calcium channel. Here, we tested the efficacy of SAK3 (ethyl 8'-methyl-2', 4-dioxo-2-(piperidin-1-yl)-2'H-spiro [cyclopentane-1, 3'-imidazo [1, 2-a] pyridine]-2-ene-3-carboxylate), a T-type calcium channel enhancer, in an animal model of TAF1 intellectual disability (ID) syndrome. At post-natal day 3, rat pups were subjected to intracerebroventricular (ICV) injection of either gRNA-control or gRNA-TAF1 CRISPR/Cas9 viruses. At post-natal day 21, the rat pups were given SAK3 (0.25 mg/kg, p.o.) or vehicle for 14 days (i.e. till post-natal day 35) and then subjected to behavioral, morphological, and molecular studies. Oral administration of SAK3 (0.25 mg/kg, p.o.) significantly rescued locomotion abnormalities associated with TAF1 gene editing. SAK3 treatment prevented the loss of cortical neurons and GFAP-positive astrocytes observed after TAF1 gene editing. In addition, SAK3 protected cells from apoptosis. SAK3 also restored the Brain-derived neurotrophic factor/protein kinase B/Glycogen Synthase Kinase 3 Beta (BDNF/AKT/GSK3β) signaling axis in TAF1 edited animals. Finally, SAK3 normalized the levels of three GSK3β substrates - CaV3.1, FOXP2, and CRMP2. We conclude that the T-type calcium channel enhancer SAK3 is beneficial against the deleterious effects of TAF1 gene-editing, in part, by stimulating the BDNF/AKT/GSK3β signaling pathway.

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.

Cepharanthine induces ROS stress in glioma and neuronal cells via modulation of VDAC permeability

Cepharanthine (CEP) is a bisbenzylisoquinoline alkaloid. Molecular dynamics studies show that CEP interacts with Voltage-dependent anion channel (VDAC), inducing the voltage-independent channel narrowing. In the new conformation, transport between mitochondria and cytoplasm is altered, which leads to the dose-dependent cytotoxicity. The biological effects of the interaction were investigated on glioblastoma multiforme (SNB-19) and neuronal (PC-12 + NGF) cell lines. The cytotoxic potential of cepharanthine was determined by MTT assay and flow cytometry apoptosis/necrosis studies. T-type calcium channel and VDAC were labelled by the immunocytochemical method. Additionally, fluorescent labelling of reactive oxygen species and mitochondria was performed. Changes in the pore size of VDAC were calculated as well. Molecular dynamics simulations were carried out to examine the interactions of cepharanthine with VDAC. The obtained results prove that cepharanthine enhances the apoptosis in glioma and neuronal cells by the release of reactive oxygen species. Cepharanthine alters the mitochondria-to-cytoplasm transport and thus induces the cytotoxicity with no selectivity.

T-type calcium channel antagonist, TTA-A2 exhibits anti-cancer properties in 3D spheroids of A549, a lung adenocarcinoma cell line

AIMS

Despite the advanced cancer treatments, there is increased resistance to chemotherapy and subsequent mortality. In lack of reliable data in monolayer cultures and animal models, researchers are shifting to 3D cancer spheroids, which represents the in vivo robust tumour morphology. Calcium is essential in cell signalling and proliferation. It is found that T-type calcium channels (TTCCs) are overexpressed in various cancer cells, supporting their increased proliferation. Many of the TTCCs blockers available could target other channels besides TTCCs, which can cause adverse effects. Therefore, we hypothesise that TTA-A2, a highly selective blocker towards TTCCs, can inhibit the growth of cancer spheroids, and provide an anti-cancer and an adjuvant role in cancer therapy.

METHODS

We studied TTA-A2 and paclitaxel (PTX-control drug) in lung adenocarcinoma cell line- A549, cancer cells and human embryonic kidney cell line- HEK 293, control cell, in their monolayer and spheroids forms for viability, proliferation, morphology change, migration, and invasion-after 48-96 h of treatment.

KEY FINDINGS

Though the results varied between the monolayer and spheroids studies, we found both anti-cancer as well as adjuvant effect of TTA-A2 in both the studies. TTA-A2 was able to inhibit the growth, viability, and metastasis of the cancer cells and spheroids. Differences in the results of two modes might explain that why drugs tested successfully in monolayer culture fail in clinical trials.

SIGNIFICANCE

This study establishes the role of TTA-A2, a potent TTCC blocker as an anti-cancer and adjuvant drug in reducing the viability and metastasis of the cancer cells.

Transportome Malfunctions and the Hallmarks of Pancreatic Cancer

Ion channels and transporters (ICT) play important roles in almost all basic cellular processes. During last decades, abundant evidences have been provided that ICT (e.g., Ca²⁺ and K⁺ channels) are notable for regulating physiological pancreatic duct cellular function and deregulation of ICT is closely associated with the widely accepted hallmarks of pancreatic ductal adenocarcinoma (PDAC) such as proliferation, apoptosis resistance, invasion, and metastasis. Hence this review focuses on the role of ICT malfunctions in context with the hallmarks of PDAC. After briefly introducing epidemiology and history of molecular oncology of PDAC and summarizing the recent studies on molecular classification systems, we focus then on the exocrine pancreas as a very active secretory gland which considerably impacts the changes in the ion transport system (the transportome) upon malignant transformation. We highlight multiplicity of ICT members (H⁺ transporters, Ca²⁺, K⁺, Na⁺ and Cl^- channels) and their functional impact in PDAC. We also present some selective therapeutic options to interfere with transportome functions and thereby with key mechanisms of malignant progression. This will hopefully contribute to a better clinical outcome based on improved therapeutic strategies for this still extremely deadly disease.

Targeting DNA Double-Strand Break (DSB) Repair to Counteract Tumor Radio-resistance

During the last decade, advances of radiotherapy (RT) have been made in the clinical practice of cancer treatment. RT exerts its anticancer effect mainly via leading to the DNA Double-Strand Break (DSB), which is one of the most toxic DNA damages. Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR) are two major DSB repair pathways in human cells. It is known that dysregulations of DSB repair elicit a predisposition to cancer and probably result in resistance to cancer therapies including RT. Therefore, targeting the DSB repair presents an attractive strategy to counteract radio-resistance. In this review, we describe the latest knowledge of the two DSB repair pathways, focusing on several key proteins contributing to the repair, such as DNA-PKcs, RAD51, MRN and PARP1. Most importantly, we discuss the possibility of overcoming radiation resistance by targeting these proteins for therapeutic inhibition. Recent tests of DSB repair inhibitors in the laboratory and their translations into clinical studies are also addressed.

Calcium Signaling Alterations Caused by Epigenetic Mechanisms in Pancreatic Cancer: From Early Markers to Prognostic Impact

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with high mortality rates. PDAC initiation and progression are promoted by genetic and epigenetic dysregulation. Here, we aimed to characterize the PDAC DNA methylome in search of novel altered pathways associated with tumor development. We examined the genome-wide DNA methylation profile of PDAC in an exploratory cohort including the comparative analyses of tumoral and non-tumoral pancreatic tissues (PT). Pathway enrichment analysis was used to choose differentially methylated (DM) CpGs with potential biological relevance. Additional samples were used in a validation cohort. DNA methylation impact on gene expression and its association with overall survival (OS) was investigated from PDAC TCGA (The Cancer Genome Atlas) data. Pathway analysis revealed DM genes in the calcium signaling pathway that is linked to the key pathways in pancreatic carcinogenesis. DNA methylation was frequently correlated with expression, and a subgroup of calcium signaling genes was associated with OS, reinforcing its probable phenotypic effect. Cluster analysis of PT samples revealed that some of the methylation alterations observed in the Calcium signaling pathway seemed to occur early in the carcinogenesis process, a finding that may open new insights about PDAC tumor biology.

Synthesis and cytotoxic effects of 2-thio-3,4-dihydroquinazoline derivatives as novel T-type calcium channel blockers

In our previous work, a series of 2-amino-3,4-dihydroquinazoline derivativesusing an electron acceptor group was reported to be potent T-type calcium channel blockers and exhibit strong cytotoxic effects against various cancerous cell lines. To investigate the role of the guanidine moiety in the 2-amino-3,4-dihydroquinazoline scaffold as a pharmacophore for dual biological activity, a new series of 2-thio-3,4-dihydroquniazoline derivatives using an electron donor group at the C2-position was synthesized and evaluated for T-type calcium channel blocking activity and cytotoxic effects against two human cancerous cell lines (lung cancer A549 and colon cancer HCT-116). Among them, compound 6g showed potent inhibition of Ca_v3.2 currents (83% inhibition) at 10 µM concentrations. The compound also exhibited IC₅₀ values of 5.0 and 6.4 µM against A549 and HCT-116 cell lines, respectively, which are comparable to the parental lead compound KYS05090. These results indicate that the isothiourea moiety similar to the guanidine moiety of 2-amino-3,4-dihydroquinazoline derivatives may be an essential pharmacophore for the desired biological activities. Therefore, our preliminary work can provide the opportunity to expand a chemical repertoire to improve affinity and selectivity for T-type calcium channels.

The rise of T-type channels in melanoma progression and chemotherapeutic resistance

Hyperactivation of the Mitogen Activated Protein Kinase (MAPK) pathway is prevalent in melanoma, principally due to mutations in the BRAF and NRAS genes. MAPK inhibitors are effective only short-term, and recurrence occurs due to functional redundancies or intertwined pathways. The remodeling of Ca²⁺ signaling is also common in melanoma cells, partly through the increased expression of T-type channels (TTCCs). Here we summarize current knowledge about the prognostic value and molecular targeting of TTCCs. Furthermore, we discuss recent evidence pointing to TTCCs as molecular switches for melanoma chemoresistance, which set the grounds for novel combined therapies against the advanced disease.

Plasma membrane Ca2+-permeable channels and sodium/calcium exchangers in tumorigenesis and tumor development of the upper gastrointestinal tract

The upper gastrointestinal (GI) tumors are multifactorial diseases associated with a combination of oncogenes and environmental factors. Currently, surgery, chemotherapy, radiotherapy and immunotherapy are relatively effective treatment options for the patients with these tumors. However, the asymptomatic phenotype of these tumors during the early stages poses as a significant limiting factor to diagnosis and often renders treatments ineffective. Therefore, new early diagnosis and effective therapy for upper GI tumors are urgently needed. Ca²⁺ is a pivotal intracellular second messenger and plays a crucial role in living cells by regulating several processes from cell division to death. The aberrant Ca²⁺ homeostasis is related to many human pathological conditions and diseases, including cancer, and thus the changes in the expression and function of plasma membrane Ca²⁺ permeable channels and sodium/calcium exchangers are frequently described in tumorigenesis and tumor development of the upper GI tract, including voltage-gated Ca²⁺ channels (VGCC), transient receptor potential (TRP) channels, store-operated channels (SOC) and Na⁺/Ca²⁺ exchanger (NCX). This review will summarize the current knowledge about plasma membrane Ca²⁺ permeable channels and sodium/calcium exchangers in the upper GI tumors and provide a synopsis of recent advancements on the role and involvement of these channels in upper GI tumors as well as a discussion of the possible strategies to target these channels and exchangers for diagnosis and therapy of the upper GI tumors.

Targeting Calcium Signalling in Malignant Mesothelioma

Calcium ions (Ca²⁺) are central in cancer development and growth, serving as a major signaling system determining the cell’s fate. Therefore, the investigation of the functional roles of ion channels in cancer development may identify novel approaches for determining tumor prognosis. Malignant mesothelioma is an aggressive cancer that develops from the serosal surface of the body, strictly related to asbestos exposure. The treatment of malignant mesothelioma is complex and the survival outcomes, rather than the overall survival data are, to date, disappointedly daunting. Nevertheless, conventional chemotherapy is almost ineffective. The alteration in the expression and/or activity of Ca²⁺ permeable ion channels seems to be characteristic of mesothelioma cells. In this review, we explore the involvement of the Ca²⁺toolkit in this disease. Moreover, the established sensitivity of some Ca²⁺channels to selective pharmacological modulators makes them interesting targets for mesothelioma cancer therapy.

[Role of Cav3.2 T-type Ca2+ channels in prostate cancer cells]

Among voltage-gated Ca²⁺ channels, T-type Ca²⁺ channels, which are activated by low voltages, regulate neuronal excitability, spontaneous neurotransmitter release, hormone secretion, etc. and also participate in proliferation of distinct cancer cells. Among three isoforms of T-type Ca²⁺ channels, Ca_v3.2 is detectable in 100% of biopsy samples from prostate cancer patients. In general, prostate cancer cells are highly sensitive to androgen deprivation therapy, but often acquire hormone-therapy resistance. The androgen deprivation may trigger neuroendocrine (NE)-like differentiation of some prostate cancer cells. We have analyzed the expression and function of Ca_v3.2 in human prostate cancer LNCaP cells during NE-like differentiation. NE-like LNCaP cells overexpress Ca_v3.2 through the CREB/Egr-1 pathway and also cystathionine-γ-lyase (CSE), which generates H₂S that enhances the channel activity of Ca_v3.2. H₂S generated by upregulated CSE appears to enhance the activity of upregulated Ca_v3.2 after the differentiation. The enhanced Ca_v3.2 activity in NE-like cells may contribute to increased secretion of mitogenic factors essential for androgen-independent proliferation of surrounding prostate cancer cells. It is known that increased extracellular glucose levels enhance Ca_v3.2 activity through asparagine (N)-linked glycosylation of Ca_v3.2, which might contribute to diabetic neuropathy. We then found that high glucose accelerates the enhanced channel function and overexpression of Ca_v3.2 in NE-like LNCaP cells, which might be associated with clinical evidence for diabetes-related poor prognosis of prostate cancer and development of hormone therapy resistance. Thus, Ca_v3.2 is considered to play a role in the pathophysiology of prostate cancer, and may serve as a therapeutic target.

T-type calcium channels drive the proliferation of androgen-receptor negative prostate cancer cells

BACKGROUND

Androgen deprivation therapy (ADT) is the treatment of choice for metastatic prostate cancer (PCa). After an initial response to ADT, PCa cells can generate castration resistant (CRPC) or neuroendocrine (NEPC) malignancies, which are incurable. T-type calcium channels (TTCCs) are emerging as promising therapeutic targets for several cancers, but their role in PCa progression has never been investigated.

METHODS

To examine the role of TTCCs in PCa, we analyzed their expression level, copy number variants (CNV) and prognostic significance using clinical datasets (Oncomine and cBioPortal). We then evaluated TTCC expression in a panel of PCa cell lines and measured the effect of their inhibition on cell proliferation and survival using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and caspase assays.

RESULTS

TTCCs were upregulated in PCas harboring androgen receptor (AR) mutations; CNV rate was positively associated with PCa progression. Higher expression of one TTCC isoform (CACNA1G) predicted poorer postoperative prognosis in early stage PCa samples. Pharmacological or small interfering RNA (siRNA)-based inhibition of TTCCs caused a decrease in PC-3 cell survival and proliferation.

CONCLUSIONS

Our results show that TTCCs are overexpressed in advanced forms of PCa and correlate with a poorer prognosis. TTCC inhibition reduces cell proliferation and survival, suggesting that there may be possible value in the therapeutic targeting of TTCCs in advanced PCa.

Ca2+ and CACNA1H mediate targeted suppression of breast cancer brain metastasis by AM RF EMF

BACKGROUND

Brain metastases are a major cause of death in patients with metastatic breast cancer. While surgical resection and radiation therapy are effective treatment modalities, the majority of patients will succumb from disease progression. We have developed a novel therapy for brain metastases that delivers athermal radiofrequency electromagnetic fields that are amplitude-modulated at breast cancer specific frequencies (BCF).

METHODS

27.12 MHz amplitude-modulated BCF were administered to a patient with a breast cancer brain metastasis by placing a spoon-shaped antenna on the anterior part of the tongue for three one-hour treatments every day. In preclinical models, a BCF dose, equivalent to that delivered to the patient's brain, was administered to animals implanted with either brain metastasis patient derived xenografts (PDXs) or brain-tropic cell lines. We also examined the efficacy of combining radiation therapy with BCF treatment. Additionally, the mechanistic underpinnings associated with cancer inhibition was identified using an agnostic approach.

FINDINGS

Animal studies demonstrated a significant decrease in growth and metastases of brain-tropic cell lines. Moreover, BCF treatment of PDXs established from patients with brain metastases showed strong suppression of their growth ability. Importantly, BCF treatment led to significant and durable regression of brain metastasis of a patient with triple negative breast cancer. The tumour inhibitory effect was mediated by Ca2+ influx in cancer cells through CACNA1H T-type voltage-gated calcium channels, which, acting as the cellular antenna for BCF, activated CAMKII/p38 MAPK signalling and inhibited cancer stem cells through suppression of β-catenin/HMGA2 signalling. Furthermore, BCF treatment downregulated exosomal miR-1246 level, which in turn decreased angiogenesis in brain environment. Therefore, targeted growth inhibition of breast cancer metastases was achieved through CACNA1H.

INTERPRETATION

We demonstrate that BCF, as a single agent or in combination with radiation, is a novel treatment approach to the treatment of brain metastases. This paradigm shifting modality warrants further clinical trials for this unmet medical need.

The Hard-To-Close Window of T-Type Calcium Channels

T-Type calcium channels (TTCCs) are key regulators of membrane excitability, which is the reason why TTCC pharmacology is subject to intensive research in the neurological and cardiovascular fields. TTCCs also play a role in cancer physiology, and pharmacological blockers such as tetralols and dihydroquinazolines (DHQs) reduce the viability of cancer cells in vitro and slow tumor growth in murine xenografts. However, the available compounds are better suited to blocking TTCCs in excitable membranes rather than TTCCs contributing window currents at steady potentials. Consistently, tetralols and dihydroquinazolines exhibit cytostatic/cytotoxic activities at higher concentrations than those required for TTCC blockade, which may involve off-target effects. Gene silencing experiments highlight the targetability of TTCCs, but further pharmacological research is required for TTCC blockade to become a chemotherapeutic option.

T-Type Cav3.1 Channels Mediate Progression and Chemotherapeutic Resistance in Glioblastoma

T-type Ca²⁺ channels (TTCC) have been identified as key regulators of cancer cell cycle and survival. In vivo studies in glioblastoma (GBM) murine xenografts have shown that drugs able to block TTCC in vitro (such as tetralol derivatives mibefradil/NNC-55-096, or different 3,4-dihydroquinazolines) slow tumor progression. However, currently available TTCC pharmacologic blockers have limited selectivity for TTCC and are unable to distinguish between TTCC isoforms. Here we analyzed the expression of TTCC transcripts in human GBM cells and show a prevalence of Cacna1g/Ca_v3.1 mRNAs. Infection of GBM cells with lentiviral particles carrying short hairpin RNA against Ca_v3.1 resulted in GBM cell death by apoptosis. We generated a murine GBM xenograft via subcutaneous injection of U87-MG GBM cells and found that tumor size was reduced when Ca_v3.1 expression was silenced. Furthermore, we developed an in vitro model of temozolomide-resistant GBM that showed increased expression of Ca_v3.1 accompanied by the activation of macroautophagy. We confirmed a positive correlation between Ca_v3.1 and autophagic markers in both GBM cultures and biopsies. Of note, Ca_v3.1 knockdown resulted in transcriptional downregulation of p62/SQSTM1 and deficient autophagy. Together, these data identify Ca_v3.1 channels as potential targets for slowing GBM progression and recurrence based on their role in regulating autophagy. SIGNIFICANCE: These findings identify Ca_v3.1 calcium channels as a molecular target to regulate autophagy and prevent progression and chemotherapeutic resistance in glioblastoma.

Voltage-Dependent Calcium Channels, Calcium Binding Proteins, and Their Interaction in the Pathological Process of Epilepsy

As an important second messenger, the calcium ion (Ca²⁺) plays a vital role in normal brain function and in the pathophysiological process of different neurodegenerative diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), and epilepsy. Ca²⁺ takes part in the regulation of neuronal excitability, and the imbalance of intracellular Ca²⁺ is a trigger factor for the occurrence of epilepsy. Several anti-epileptic drugs target voltage-dependent calcium channels (VDCCs). Intracellular Ca²⁺ levels are mainly controlled by VDCCs located in the plasma membrane, the calcium-binding proteins (CBPs) inside the cytoplasm, calcium channels located on the intracellular calcium store (particular the endoplasmic reticulum/sarcoplasmic reticulum), and the Ca²⁺-pumps located in the plasma membrane and intracellular calcium store. So far, while many studies have established the relationship between calcium control factors and epilepsy, the mechanism of various Ca²⁺ regulatory factors in epileptogenesis is still unknown. In this paper, we reviewed the function, distribution, and alteration of VDCCs and CBPs in the central nervous system in the pathological process of epilepsy. The interaction of VDCCs with CBPs in the pathological process of epilepsy was also summarized. We hope this review can provide some clues for better understanding the mechanism of epileptogenesis, and for the development of new anti-epileptic drugs targeting on VDCCs and CBPs.

Calcium signaling and the therapeutic targeting of cancer cells

The calcium signal is implicated in a variety of processes important in tumor progression (e.g. proliferation and invasiveness). The calcium signal has also been shown to be important in other processes important in cancer progression including the development of resistance to current cancer therapies. In this review, we discuss how Ca²⁺ channels, pumps and exchangers may be drug targets in some cancer types. We consider what factors should be taken into account when considering an optimal Ca²⁺ channel, pump or exchanger as a candidate for further assessment as a novel drug target in cancer. We also present and summarize how some therapies for the treatment of cancer intersect with Ca²⁺ signaling and how pharmacological manipulation of the machinery of Ca²⁺ signaling could promote the effectiveness of some therapies. We also review new therapeutic opportunities for Ca²⁺ signal modulators in the context of the tumor microenvironment.