Histone deacetylase inhibitor- and PMA-induced upregulation of PMCA4b enhances Ca2+ clearance from MCF-7 breast cancer cells

Plasma membrane Ca2+ pump isoform 4 function in cell migration and cancer metastasis

The Ca2+ ion is a universal second messenger involved in many vital physiological functions including cell migration and development. To fulfil these tasks the cytosolic Ca2+ concentration is tightly controlled, and this involves an intricate functional balance between a variety of channels and pumps of the Ca2+ signalling machinery. Among these proteins, plasma membrane Ca2+ ATPases (PMCAs) represent the major high-affinity Ca2+ extrusion systems in the cell membrane that are effective in maintaining free Ca2+ concentration at exceedingly low cytosolic levels, which is essential for normal cell function. An imbalance in Ca2+ signalling can have pathogenic consequences including cancer and metastasis. Recent studies have highlighted the role of PMCAs in cancer progression and have shown that a particular variant, PMCA4b, is downregulated in certain cancer types, causing delayed attenuation of the Ca2+ signal. It has also been shown that loss of PMCA4b leads to increased migration and metastasis of melanoma and gastric cancer cells. In contrast, an increased PMCA4 expression has been reported in pancreatic ductal adenocarcinoma that coincided with increased cell migration and shorter patient survival, suggesting distinct roles of PMCA4b in various tumour types and/or different stages of tumour development. The recently discovered interaction of PMCAs with basigin, an extracellular matrix metalloproteinase inducer, may provide further insights into our understanding of the specific roles of PMCA4b in tumour progression and cancer metastasis.

Calcium Homeostasis in the Development of Resistant Breast Tumors

Cancer is one of the main health problems worldwide. Only in 2020, this disease caused more than 19 million new cases and almost 10 million deaths, with breast cancer being the most diagnosed worldwide. Today, despite recent advances in breast cancer treatment, a significant percentage of patients will either not respond to therapy or will eventually experience lethal progressive disease. Recent studies highlighted the involvement of calcium in the proliferation or evasion of apoptosis in breast carcinoma cells. In this review, we provide an overview of intracellular calcium signaling and breast cancer biology. We also discuss the existing knowledge on how altered calcium homeostasis is implicated in breast cancer development, highlighting the potential utility of Ca²⁺ as a predictive and prognostic biomarker, as well as its potential for the development of new pharmacological treatments to treat the disease.

Genetic variations in human ATP2B4 gene alter Plasmodium falciparum in vitro growth in RBCs from Gambian adults

BACKGROUND

Polymorphisms in ATP2B4 coding for PMCA4b, the primary regulator of erythrocyte calcium concentration, have been shown by GWAS and cross-sectional studies to protect against severe malaria but the mechanism remains unknown.

METHODS

Using a recall-by-genotype design, we investigated the impact of a common haplotype variant in ATP2B4 using in vitro assays that model erythrocyte stage malaria pathogenesis. Ninety-six donors representing homozygote (carriers of the minor allele, C/C), heterozygote (T/C) and wildtype (T/T) carriers of the tagging SNP rs1541252 were selected from a cohort of over 12,000 participants in the Keneba Biobank.

RESULTS

Red blood cells (RBCs) from homozygotes showed reduced PMCA4b protein expression (mean fluorescence intensities (MFI = 2428 ± 124, 3544 ± 159 and 4261 ± 283], for homozygotes, heterozygotes and wildtypes respectively, p < 0.0001) and slower rates of calcium expulsion (calcium t_½ ± SD = 4.7 ± 0.5, 1.8 ± 0.3 and 1.9 ± 0.4 min, p < 0.0001). Growth of a Plasmodium falciparum laboratory strain (FCR3) and two Gambian field isolates was decreased in RBCs from homozygotes compared to heterozygotes and wildtypes (p < 0.01). Genotype group did not affect parasite adhesion in vitro or var-gene expression in malaria-infected RBCs. Parasite growth was inhibited by a known inhibitor of PMCA4b, aurintricarboxylic acid (IC₅₀ = 122uM CI: 110-134) confirming its sensitivity to calcium channel blockade.

CONCLUSION

The data support the hypothesis that this ATP2B4 genotype, common in The Gambia and other malaria-endemic areas, protects against severe malaria through the suppression of parasitaemia during an infection. Reduction in parasite density plays a pivotal role in disease outcome by minimizing all aspects of malaria pathogenesis. Follow up studies are needed to further elucidate the mechanism of protection and to determine if this ATP2B4 genotype carries a fitness cost or increases susceptibility to other human disease.

The Prognostic Relevance of PMCA4 Expression in Melanoma: Gender Specificity and Implications for Immune Checkpoint Inhibition

PMCA4 is a critical regulator of Ca2+ homeostasis in mammalian cells. While its biological and prognostic relevance in several cancer types has already been demonstrated, only preclinical investigations suggested a metastasis suppressor function in melanoma. Therefore, we studied the expression pattern of PMCA4 in human skin, nevus, as well as in primary and metastatic melanoma using immunohistochemistry. Furthermore, we analyzed the prognostic power of PMCA4 mRNA levels in cutaneous melanoma both at the non-metastatic stage as well as after PD-1 blockade in advanced disease. PMCA4 localizes to the plasma membrane in a differentiation dependent manner in human skin and mucosa, while nevus cells showed no plasma membrane staining. In contrast, primary cutaneous, choroidal and conjunctival melanoma cells showed specific plasma membrane localization of PMCA4 with a wide range of intensities. Analyzing the TCGA cohort, PMCA4 mRNA levels showed a gender specific prognostic impact in stage I-III melanoma. Female patients with high transcript levels had a significantly longer progression-free survival. Melanoma cell specific PMCA4 protein expression is associated with anaplasticity in melanoma lung metastasis but had no impact on survival after lung metastasectomy. Importantly, high PMCA4 transcript levels derived from RNA-seq of cutaneous melanoma are associated with significantly longer overall survival after PD-1 blockade. In summary, we demonstrated that human melanoma cells express PMCA4 and PMCA4 transcript levels carry prognostic information in a gender specific manner.

LncPTSR Triggers Vascular Remodeling in Pulmonary Hypertension by Regulating [Ca2+]i in Pulmonary Arterial Smooth Muscle Cells

Pulmonary hypertension (PH) is characterized by vascular remodeling and sustained increase in right ventricular systolic pressure (RVSP). The molecular mechanisms behind PH development remain unclear. Here, a long non-coding RNA (lncRNA) attenuated by platelet-derived growth factor BB (PDGF-BB) was identified and its functional roles were investigated in vitro and in vivo. Using RNA-seq data and rapid amplification of cDNA ends, a lncRNA neighboring the locus of plasma membrane calcium transporting ATPase 4 (PMCA4) was identified and named lncPTSR. It is a highly-conserved nuclear lncRNA, and was downregulated in pulmonary arterial smooth muscle cells (PASMCs) with PDGF-BB stimulation or hypoxia induction. Gene interruption/overexpression assays revealed that lncPTSR negatively regulates rat PASMCs proliferation, apoptosis, and migration. LncPTSR interruption in Sprague Dawley (SD) rats using adenovirus associated virus type 9 (AAV9)-mediated short-hairpin RNA (shRNA) resulted in a significant increase in RVSP and vascular remodeling in normoxic condition. LncPTSR knockdown also suppressed PMCA4 expression and attenuated the intracellular Ca2+ efflux of PASMCs in vitro and in vivo. Further studies suggest a complex cross-talk between lncPTSR and mitogen-activated protein kinase (MAPK) pathway: inhibition of mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated kinase (ERK) abolishes the PDGF-BB-mediated lncPTSR downregulation, and lncPTSR plays a feedback regulation for MAPK signaling molecules. The present study suggests that lncPTSR participates in pulmonary artery (PA) remodeling via modulating the expression of PMCA4 and intracellular Ca2+ homeostasis downstream of PDGF-BB driven MEK/ERK signaling. These results suggest lncPTSR may be a promising therapeutic target in PH treatment.

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.

The effect of iron on the expression levels of calcium related gene in cisplatin resistant epithelial ovarian cancer cells

Aim: Anticancer drugs (chemotherapeutics) used in cancer treatment (chemotherapy) lead to drug resistance. This study was conducted to investigate the possible effect of iron on calcium homeostasis in epithelial ovarian cancer cells (MDAH-2774) and cisplatin-resistant cells of the same cell line (MDAH-2774/DDP). Methods: To develop MDAH-2774/DDP cells, MDAH-2774 (MDAH) cells were treated with cisplatin in dose increases of 5 μM between 0 μM and 70 μM. The effect of iron on the viability of MDAH and MDAH/DDP cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test at the end of 24 h incubation. Results: At increasing iron concentrations in MDAH and MDAH/DDP cells, the mRNA gene of fifteen genes [inositol 1,4,5-triphosphate receptor (IP3R)1/2/3, ryanodine receptor (RYR)1/2, sarco/endoplasmic reticulum Ca2+ ATPase (SERCA)1/2/3, Na+/Ca2+ exchange (NCX)1/2/3, and plasma membrane Ca2+ ATPase (PMCA)1/2/3/4] associated with Ca2+ differences in expression were determined by quantitative reverse transcription-polymerase chain reaction. Changes in IP3R2, RYR1, SERCA2, NCX3, PMCA1, and PMCA3 gene expressions were observed in iron treatment of MDAH/DDP cells, while changes were detected in iron treatment of MDAH cells in IP3R1/2/3, RYR1/2, SERCA1/2/3, NCX2/3, and PMCA1 expressions. Conclusions: This changes in the expression of calcium channels, pumps, and exchange proteins in the epithelial ovarian cancer cell line and in cisplatin-resistant epithelial ovarian cancer cells suggest that iron may have an important role in regulating calcium homeostasis. Due to differences in the expression of genes that play of an important role in the regulation of calcium homeostasis in the effect of iron, drug resistance can be prevented by introducing a new perspective on the use of inhibitors and activators of these genes and thus cytostatic treatment strategies.

Genome-wide DNA methylome and whole-transcriptome landscapes of spontaneous intraductal papilloma in tree shrews

Background

Breast intraductal papilloma (IP) is mainly caused by the abnormal proliferation of ductal epithelial cells. Tree shrews have potential as an animal model for the study of breast tumours; however, little is known regarding the transcriptome and DNA methylome landscapes of breast IP in tree shrews. In this research, we conducted whole-genome DNA methylation and transcriptome analyses of breast IP and normal mammary glands in tree shrews.

Methods

DNA methylation profiles were generated from the whole-genome bisulfite sequencing and whole-transcriptome landscapes of IP and control groups of tree shrews through strand-specific library construction and RNA sequencing. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes functional enrichment analyses and gene set enrichment analysis were performed. Spearman’s correlation analysis was used to identify statistical relationships between gene expression and DNA methylation.

Results

A genome-wide perspective of the epigenetic regulation of protein-coding genes in breast IP in tree shrews was obtained. The methylation levels at CG sites were considerably higher than those at CHG or CHH sites, and were highest in gene body regions. In total, 3,486, 82 and 361 differentially methylated regions (DMRs) were identified in the context of CG, CHG, and CHH, respectively, and 701 differentially methylated genes (DMGs) were found. Further, through transcriptomic analysis, 62 differentially expressed genes, 50 long noncoding RNAs, and 32 circular RNAs were identified in breast IP compared to normal mammary glands. Correlation analysis between the DNA methylation and transcriptome data revealed that 25 DMGs were also differentially expressed genes, among which the expression levels of 9 genes were negatively correlated with methylation levels in gene body regions. Importantly, integrated analysis identified 3 genes (PDZ domain-containing 1, ATPase plasma membrane Ca²⁺ transporting 4 and Lymphocyte cytosolic protein 1) that could serve as candidates for further study of breast IP in tree shrews.

Conclusions

This research has unearthed the comprehensive landscape of the transcriptome and DNA methylome of spontaneous IP in tree shrews, as well as candidate tumorigenesis related genes in IP. These results will contribute to the use of tree shrews in animal models of breast tumours.

The Plasma Membrane Ca2+ Pump PMCA4b Regulates Melanoma Cell Migration through Remodeling of the Actin Cytoskeleton

Simple Summary

Earlier we demonstrated that the plasma membrane Ca²⁺ pump PMCA4b inhibits migration and metastatic activity of BRAF mutant melanoma cells, however, the exact mechanism has not been fully understood. Here we demonstrate that PMCA4b acted through actin cytoskeleton remodeling in generating a low migratory melanoma cell phenotype resulting in increased cell–cell connections, lamellipodia and stress fiber formation. Both proper trafficking and calcium transporting activity of the pump were essential to complete these tasks indicating that controlling Ca²⁺ concentration levels at specific plasma membrane locations such as the cell front played a role. Our findings suggest that PMCA4b downregulation is likely one of the mechanisms that leads to the perturbed cancer cell cytoskeleton organization resulting in enhanced melanoma cell migration and metastasis.

Abstract

We demonstrated that the plasma membrane Ca²⁺ ATPase PMCA4b inhibits migration and metastatic activity of BRAF mutant melanoma cells. Actin dynamics are essential for cells to move, invade and metastasize, therefore, we hypothesized that PMCA4b affected cell migration through remodeling of the actin cytoskeleton. We found that expression of PMCA4b in A375 BRAF mutant melanoma cells induced a profound change in cell shape, cell culture morphology, and displayed a polarized migratory character. Along with these changes the cells became more rounded with increased cell–cell connections, lamellipodia and stress fiber formation. Silencing PMCA4b in MCF-7 breast cancer cells had a similar effect, resulting in a dramatic loss of stress fibers. In addition, the PMCA4b expressing A375 cells maintained front-to-rear Ca²⁺ concentration gradient with the actin severing protein cofilin localizing to the lamellipodia, and preserved the integrity of the actin cytoskeleton from a destructive Ca²⁺ overload. We showed that both PMCA4b activity and trafficking were essential for the observed morphology and motility changes. In conclusion, our data suggest that PMCA4b plays a critical role in adopting front-to-rear polarity in a normally spindle-shaped cell type through F-actin rearrangement resulting in a less aggressive melanoma cell phenotype.

Transcriptional and epigenetic landscape of Ca2+-signaling genes in hepatocellular carcinoma

Calcium (Ca²⁺) signaling has a major role in regulating a wide range of cellular mechanisms, including gene expression, proliferation, metabolism, cell death, muscle contraction, among others. Recent evidence suggests that ~ 1600 genes are related to the Ca²⁺ signaling. Some of these genes' expression is altered in several pathological conditions, including different cancer types, and epigenetic mechanisms are involved. However, their expression and regulation in hepatocellular carcinoma (HCC) and the liver are barely known. Here, we aimed to explore the expression of genes involved in the Ca²⁺-signaling in HCC, liver regeneration, and hepatocyte differentiation, and whether their expression is regulated by epigenetic mechanisms such as DNA methylation and histone posttranslational modifications (HPM). Results show that several Ca²⁺-signaling genes' expression is altered in HCC samples; among these, a subset of twenty-two correlate with patients' survival. DNA methylation correlates with eight of these genes' expression, and Guadecitabine, a hypomethylating agent, regulates the expression of seven down-regulated and three up-regulated genes in HepG2 cells. The down-regulated genes displayed a marked decrease of euchromatin histone marks, whereas up-regulated genes displayed gain in these marks. Additionally, the expression of these genes is modulated during liver regeneration and showed similar profiles between in vitro differentiated hepatocytes and liver-derived hepatocytes. In conclusion, some components of the Ca²⁺-signaling are altered in HCC and displayed a correlation with patients' survival. DNA methylation and HMP are an attractive target for future investigations to regulate their expression. Ca²⁺-signaling could be an important regulator of cell proliferation and differentiation in the liver.

The histone deacetylase inhibitor PCI-24781 impairs calcium influx and inhibits proliferation and metastasis in breast cancer

Histone deacetylases (HDACs) are involved in key cellular processes and have been implicated in cancer. As such, compounds that target HDACs or drugs that target epigenetic markers may be potential candidates for cancer therapy. This study was therefore aimed to identify a potential epidrug with low toxicity and high efficiency as anti-tumor agents. Methods: We first screened an epigenetic small molecule inhibitor library to screen for an epidrug for breast cancer. The candidate was identified as PCI-24781 and was characterized for half maximal inhibitory concentration (IC₅₀), for specificity to breast cancer cells, and for effects on carcinogenesis and metastatic properties of breast cancer cell lines in vitro. A series of in silico and in vitro analyses were further performed of PCI-24781 to identify and understand its target. Results: Screening of an epigenetic inhibitor library in MDA-MB-231 cells, a malignant cancer cell line, showed that PCI-24781 is a potential anti-tumor drug specific to breast cancer. Ca²⁺ related pathways were identified as a potential target of PCI-24781. Further analyses showed that PCI-24781 inhibited Gαq-PLCβ3-mediated calcium signaling by activating the expression of regulator of G-protein signaling 2 (RGS2) to reduce cell proliferation, metastasis, and differentiation, resulting in cell death in breast cancer. In addition, RGS2 depletion reversed anti-tumor effect and inhibition of calcium influx induced by PCI-24781 treatment in breast cancer cells. Conclusions: We have demonstrated that PCI-24781 is an effective anti-tumor therapeutic agent that targets calcium signaling by activating RGS2. This study also provides a novel perspective into the use of HDAC inhibitors for cancer therapy.

PDGF/MEK/ERK axis represses Ca2+ clearance via decreasing the abundance of plasma membrane Ca2+ pump PMCA4 in pulmonary arterial smooth muscle cells

Pulmonary arterial hypertension (PAH) is a rare and lethal disease characterized by vascular remodeling and vasoconstriction, which is associated with increased intracellular calcium ion concentration ([Ca2+]i). Platelet-derived growth factor-BB (PDGF-BB) is the most potent mitogen for pulmonary arterial smooth muscle cells (PASMCs) and is involved in vascular remodeling during PAH development. PDGF signaling has been proved to participate in maintaining Ca2+ homeostasis of PASMCs; however, the mechanism needs to be further elucidated. Here, we illuminate that the expression of plasma membrane calcium-transporting ATPase 4 (PMCA4) was downregulated in PASMCs after PDGF-BB stimulation, which could be abolished by restraining the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK). Functionally, suppression of PMCA4 attenuated the [Ca2+]i clearance in PASMCs after Ca2+ entry, promoting cell proliferation and elevating cell locomotion through mediating formation of focal adhesion. Additionally, the expression of PMCA4 was decreased in the pulmonary artery of monocrotaline (MCT)- or hypoxia-induced PAH rats. Moreover, knockdown of PMCA4 could increase the right ventricular systolic pressure (RVSP) and wall thickness (WT) of pulmonary artery in rats raised under normal conditions. Taken together, our findings demonstrate the importance of the PDGF/MEK/ERK/PMCA4 axis in intracellular Ca2+ homeostasis in PASMCs, indicating a functional role of PMCA4 in pulmonary arterial remodeling and PAH development.

Basolateral Secretion from Caco-2 Cells Pretreated with Fecal Waters from Breast Cancer Patients Affects MCF7 Cell Viability

We hypothesized that the role of microbiota in breast cancer relates to its influence on gut lipid metabolism. This was tested in an in vitro model combining MCF-7 and Caco-2 cells. A total of 32 women newly diagnosed for breast cancer before any treatment and 28 healthy women provided their stools. Bacterial DNA was amplified by qPCR targeting 16s rRNA specific to Bacteroidetes and Firmicutes phyla, Lactobacillales sp., Clostridium cluster IV, Faecalibacterium prausnitzii, Clostridium cluster XIVa, Roseburia intestinalis, Blautia sp., Lactonifactor longoviformis, Bifidobacterium sp., Coriobacteriaceae, Eggertella lenta, Escherichia, and Shigella. Fecal waters (FW) were quantified for short chain fatty acids (SCFA). Caco-2 cells grown on filter inserts were incubated apically with 10% FW for 24 h, and LXR, apolipoproteins AIV, and E gene expression were estimated by real time (RT) qPCR. Then, MCF-7 cells were incubated with the whole basolateral medium for 24 h, and their viability was estimated by 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) test. Regression models were used to determine the correlation between MCF-7 viability and bacteria relative abundance, Caco-2 cells lipid metabolism gene expression and stool composition, as well as microbiota composition and short chain fatty acids. Logistic regression models established disease odds ratios (OR) for MCF-7 viability and Caco-2 gene expression. The OR of MCF-7 viability was 1.05 (1.01–1.10) (OR (5th–95th), p = 0.04), while that of apo AIV gene expression was 0.63 (0.39–1.01), p = 0.055). Viability correlated with % Bifidobacterium sp. (21.18 ± 7.66, p = 0.008) and valerate (−2.849 ± 1.048, p = 0.009) (β ± s.d.). This study suggests that microbiota interacts with intestine cell lipid metabolism. Since these metabolites can reach breast cells by systemic circulation, we hypothesized that they may influence cancer disease.

P38 MAPK Promotes Migration and Metastatic Activity of BRAF Mutant Melanoma Cells by Inducing Degradation of PMCA4b

Metastatic melanoma is the most aggressive type of skin cancer. Previously, we identified the plasma membrane Ca²⁺ pump isoform 4b (PMCA4b or ATP2B4) as a putative metastasis suppressor in BRAF mutant melanoma cells. Metastasis suppressors are often downregulated in cancer, therefore, it is important to identify the pathways involved in their degradation. Here, we studied the role of p38 MAPK in PMCA4b degradation and its effect on melanoma metastasis. We found that activation of p38 MAPK induces internalization and subsequent degradation of PMCA4b through the endo/lysosomal system that contributes to the low PMCA4b steady-state protein level of BRAF mutant melanoma cells. Moreover, BRAF wild type cell models including a doxycycline-inducible HEK cell system revealed that p38 MAPK is a universal modulator of PMCA4b endocytosis. Inhibition of the p38 MAPK pathway markedly reduced migration, colony formation and metastatic activity of BRAF mutant cells in vitro partially through an increase in PMCA4b and a decrease in β4 integrin abundance. In conclusion, our data suggest that the p38 MAPK pathway plays a key role in PMCA4b degradation and inhibition of this pathway—by increasing the stability of PMCA4b—may provide a potential therapeutic target for inhibition of melanoma progression and metastasis.

Endoplasmic Reticulum Calcium Pumps and Tumor Cell Differentiation

Endoplasmic reticulum (ER) calcium homeostasis plays an essential role in cellular calcium signaling, intra-ER protein chaperoning and maturation, as well as in the interaction of the ER with other organelles. Calcium is accumulated in the ER by sarco/endoplasmic reticulum calcium ATPases (SERCA enzymes) that generate by active, ATP-dependent transport, a several thousand-fold calcium ion concentration gradient between the cytosol (low nanomolar) and the ER lumen (high micromolar). SERCA enzymes are coded by three genes that by alternative splicing give rise to several isoforms, which can display isoform-specific calcium transport characteristics. SERCA expression levels and isoenzyme composition vary according to cell type, and this constitutes a mechanism whereby ER calcium homeostasis is adapted to the signaling and metabolic needs of the cell, depending on its phenotype, its state of activation and differentiation. As reviewed here, in several normal epithelial cell types including bronchial, mammary, gastric, colonic and choroid plexus epithelium, as well as in mature cells of hematopoietic origin such as pumps are simultaneously expressed, whereas in corresponding tumors and leukemias SERCA3 expression is selectively down-regulated. SERCA3 expression is restored during the pharmacologically induced differentiation of various cancer and leukemia cell types. SERCA3 is a useful marker for the study of cell differentiation, and the loss of SERCA3 expression constitutes a previously unrecognized example of the remodeling of calcium homeostasis in tumors.

Expression of calcium pumps is differentially regulated by histone deacetylase inhibitors and estrogen receptor alpha in breast cancer cells

Background

Remodeling of Ca²⁺ signaling is an important step in cancer progression, and altered expression of members of the Ca²⁺ signaling toolkit including the plasma membrane Ca²⁺ ATPases (PMCA proteins encoded by ATP2B genes) is common in tumors.

Methods

In this study PMCAs were examined in breast cancer datasets and in a variety of breast cancer cell lines representing different subtypes. We investigated how estrogen receptor alpha (ER-α) and histone deacetylase (HDAC) inhibitors regulate the expression of these pumps.

Results

Three distinct datasets displayed significantly lower ATP2B4 mRNA expression in invasive breast cancer tissue samples compared to normal breast tissue, whereas the expression of ATP2B1 and ATP2B2 was not altered. Studying the protein expression profiles of Ca²⁺ pumps in a variety of breast cancer cell lines revealed low PMCA4b expression in the ER-α positive cells, and its marked upregulation upon HDAC inhibitor treatments. PMCA4b expression was also positively regulated by the ER-α pathway in MCF-7 cells that led to enhanced Ca²⁺ extrusion capacity in response to 17β-estradiol (E2) treatment. E2-induced PMCA4b expression was further augmented by HDAC inhibitors. Surprisingly, E2 did not affect the expression of PMCA4b in other ER-α positive cells ZR-75-1, T-47D and BT-474. These findings were in good accordance with ChIP-seq data analysis that revealed an ER-α binding site in the ATP2B4 gene in MCF-7 cells but not in other ER-α positive tumor cells. In the triple negative cells PMCA4b expression was relatively high, and the effect of HDAC inhibitor treatment was less pronounced as compared to that of the ER-α positive cells. Although, the expression of PMCA4b was relatively high in the triple negative cells, a fraction of the protein was found in intracellular compartments that could interfere with the cellular function of the protein.

Conclusions

Our results suggest that the expression of Ca²⁺ pumps is highly regulated in breast cancer cells in a subtype specific manner. Our results suggest that hormonal imbalances, epigenetic modifications and impaired protein trafficking could interfere with the expression and cellular function of PMCA4b in the course of breast cancer progression.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4945-x) contains supplementary material, which is available to authorized users.

The Plasma Membrane Calcium ATPases and Their Role as Major New Players in Human Disease

The Ca²⁺ extrusion function of the four mammalian isoforms of the plasma membrane calcium ATPases (PMCAs) is well established. There is also ever-increasing detail known of their roles in global and local Ca²⁺ homeostasis and intracellular Ca²⁺ signaling in a wide variety of cell types and tissues. It is becoming clear that the spatiotemporal patterns of expression of the PMCAs and the fact that their abundances and relative expression levels vary from cell type to cell type both reflect and impact on their specific functions in these cells. Over recent years it has become increasingly apparent that these genes have potentially significant roles in human health and disease, with PMCAs1-4 being associated with cardiovascular diseases, deafness, autism, ataxia, adenoma, and malarial resistance. This review will bring together evidence of the variety of tissue-specific functions of PMCAs and will highlight the roles these genes play in regulating normal physiological functions and the considerable impact the genes have on human disease.

Histone Deacetylase Inhibitor Treatment Increases the Expression of the Plasma Membrane Ca2+ Pump PMCA4b and Inhibits the Migration of Melanoma Cells Independent of ERK

Several new therapeutic options emerged recently to treat metastatic melanoma; however, the high frequency of intrinsic and acquired resistance among patients shows a need for new therapeutic options. Previously, we identified the plasma membrane Ca²⁺ ATPase 4b (PMCA4b) as a metastasis suppressor in BRAF-mutant melanomas and found that mutant BRAF inhibition increased the expression of the pump, which then inhibited the migratory and metastatic capability of the cells. Earlier it was also demonstrated that histone deacetylase inhibitors (HDACis) upregulated PMCA4b expression in gastric, colon, and breast cancer cells. In this study, we treated one BRAF wild-type and two BRAF-mutant melanoma cell lines with the HDACis, SAHA and valproic acid, either alone, or in combination with the BRAF inhibitor, vemurafenib. We found that HDACi treatment strongly increased the expression of PMCA4b in all cell lines irrespective of their BRAF mutational status, and this effect was independent of ERK activity. Furthermore, HDAC inhibition also enhanced the abundance of the housekeeping isoform PMCA1. Combination of HDACis with vemurafenib, however, did not have any additive effects on either PMCA isoform. We demonstrated that the HDACi-induced increase in PMCA abundance was coupled to an enhanced [Ca²⁺]_i clearance rate and also strongly inhibited both the random and directional movements of A375 cells. The primary role of PMCA4b in these characteristic changes was demonstrated by treatment with the PMCA4-specific inhibitor, caloxin 1c2, which was able to restore the slower Ca²⁺ clearance rate and higher motility of the cells. While HDAC treatment inhibited cell motility, it decreased only modestly the ratio of proliferative cells and cell viability. Our results show that in melanoma cells the expression of both PMCA4b and PMCA1 is under epigenetic control and the elevation of PMCA4b expression either by HDACi treatment or by the decreased activation of the BRAF-MEK-ERK pathway can inhibit the migratory capacity of the highly motile A375 cells.

Sphingomyelin-induced inhibition of the plasma membrane calcium ATPase causes neurodegeneration in type A Niemann-Pick disease

Niemann-Pick disease type A (NPA) is a rare lysosomal storage disorder characterized by severe neurological alterations that leads to death in childhood. Loss-of-function mutations in the acid sphingomyelinase (ASM) gene cause NPA, and result in the accumulation of sphingomyelin (SM) in lysosomes and plasma membrane of neurons. Using ASM knockout (ASMko) mice as a NPA disease model, we investigated how high SM levels contribute to neural pathology in NPA. We found high levels of oxidative stress both in neurons from these mice and a NPA patient. Impaired activity of the plasma membrane calcium ATPase (PMCA) increases intracellular calcium. SM induces PMCA decreased activity, which causes oxidative stress. Incubating ASMko-cultured neurons in the histone deacetylase inhibitor, SAHA, restores PMCA activity and calcium homeostasis and, consequently, reduces the increased levels of oxidative stress. No recovery occurs when PMCA activity is pharmacologically impaired or genetically inhibited in vitro. Oral administration of SAHA prevents oxidative stress and neurodegeneration, and improves behavioral performance in ASMko mice. These results demonstrate a critical role for plasma membrane SM in neuronal calcium regulation. Thus, we identify changes in PMCA-triggered calcium homeostasis as an upstream mediator for NPA pathology. These findings can stimulate new approaches for pharmacological remediation in a disease with no current clinical treatments.

Multifaceted plasma membrane Ca(2+) pumps: From structure to intracellular Ca(2+) handling and cancer

Plasma membrane Ca(2+) ATPases (PMCAs) are intimately involved in the control of intracellular Ca(2+) concentration. They reduce Ca(2+) in the cytosol not only by direct ejection, but also by controlling the formation of inositol-1,4,5-trisphosphate and decreasing Ca(2+) release from the endoplasmic reticulum Ca(2+) pool. In mammals four genes (PMCA1-4) are expressed, and alternative RNA splicing generates more than twenty variants. The variants differ in their regulatory characteristics. They localize into highly specialized membrane compartments and respond to the incoming Ca(2+) with distinct temporal resolution. The expression pattern of variants depends on cell type; a change in this pattern can result in perturbed Ca(2+) homeostasis and thus altered cell function. Indeed, PMCAs undergo remarkable changes in their expression pattern during tumorigenesis that might significantly contribute to the unbalanced Ca(2+) homeostasis of cancer cells. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

Histone deacetylases and atherosclerosis

Atherosclerosis is the most common pathological process that leads to cardiovascular diseases, a disease of large- and medium-sized arteries that is characterized by a formation of atherosclerotic plaques consisting of necrotic cores, calcified regions, accumulated modified lipids, smooth muscle cells (SMCs), endothelial cells, leukocytes, and foam cells. Recently, the question about how to suppress the occurrence of atherosclerosis and alleviate the progress of cardiovascular disease becomes the hot topic. Accumulating evidence suggests that histone deacetylases(HDACs) play crucial roles in arteriosclerosis. This review summarizes the effect of HDACs and HDAC inhibitors(HDACi) on the progress of atherosclerosis.

Altered calcium signaling in cancer cells

It is the nature of the calcium signal, as determined by the coordinated activity of a suite of calcium channels, pumps, exchangers and binding proteins that ultimately guides a cell's fate. Deregulation of the calcium signal is often deleterious and has been linked to each of the 'cancer hallmarks'. Despite this, we do not yet have a full understanding of the remodeling of the calcium signal associated with cancer. Such an understanding could aid in guiding the development of therapies specifically targeting altered calcium signaling in cancer cells during tumorigenic progression. Findings from some of the studies that have assessed the remodeling of the calcium signal associated with tumorigenesis and/or processes important in invasion and metastasis are presented in this review. The potential of new methodologies is also discussed. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.