The type III inositol 1,4,5-trisphosphate receptor is associated with aggressiveness of colorectal carcinoma

ER Ca2+ release and store-operated Ca2+ entry - partners in crime or independent actors in oncogenic transformation?

Ca²⁺ is a pleiotropic messenger that controls life and death decisions from fertilisation until death. Cellular Ca²⁺ handling mechanisms show plasticity and are remodelled throughout life to meet the changing needs of the cell. In turn, as the demands on a cell alter, for example through a change in its niche environment or its functional requirements, Ca²⁺ handling systems may be targeted to sustain the remodelled cellular state. Nowhere is this more apparent than in cancer. Oncogenic transformation is a multi-stage process during which normal cells become progressively differentiated towards a cancerous state that is principally associated with enhanced proliferation and avoidance of death. Ca²⁺ signalling is intimately involved in almost all aspects of the life of a transformed cell and alterations in Ca²⁺ handling have been observed in cancer. Moreover, this remodelling of Ca²⁺ signalling pathways is also required in some cases to sustain the transformed phenotype. As such, Ca²⁺ handling is hijacked by oncogenic processes to deliver and maintain the transformed phenotype. Central to generation of intracellular Ca²⁺ signals is the release of Ca²⁺ from the endoplasmic reticulum intracellular (ER) Ca²⁺ store via inositol 1,4,5-trisphosphate receptors (InsP₃Rs). Upon depletion of ER Ca²⁺, store-operated Ca²⁺ entry (SOCE) across the plasma membrane occurs via STIM-gated Orai channels. SOCE serves to both replenish stores but also sustain Ca²⁺ signalling events. Here, we will discuss the role and regulation of these two signalling pathways and their interplay in oncogenic transformation.

Oncoproteomic and gene expression analyses identify prognostic biomarkers for second primary malignancy in patients with head and neck squamous cell carcinoma

Patients with head and neck squamous cell carcinoma are at increased risk of developing a second primary malignancy, which is associated with poor prognosis and early death. To help improve clinical outcome, we aimed to identify biomarkers for second primary malignancy risk prediction using the routinely obtained formalin-fixed paraffin-embedded tissues of the index head and neck cancer. Liquid chromatography-tandem mass spectrometry was initially performed for candidate biomarker discovery in 16 pairs of primary cancer tissues and their matched normal mucosal epithelia from head and neck squamous cell carcinoma patients with or without second primary malignancy. The 32 candidate proteins differentially expressed between head and neck cancers with and without second primary malignancy were identified. Among these, 30 selected candidates and seven more from literature review were further studied using NanoString nCounter gene expression assay in an independent cohort of 49 head and neck cancer patients. Focusing on the p16-negative cases, we showed that a multivariate logistic regression model comprising the expression levels of ITPR3, KMT2D, EMILIN1, and the patient's age can accurately predict second primary malignancy occurrence with 88% sensitivity and 75% specificity. Furthermore, using Cox proportional hazards regression analysis and survival analysis, high expression levels of ITPR3 and DSG3 were found to be significantly associated with shorter time to second primary malignancy development (log-rank test P = 0.017). In summary, we identified a set of genes whose expressions may serve as the prognostic biomarkers for second primary malignancy occurrence in head and neck squamous cell carcinomas. In combination with the histopathologic examination of index tumor, these biomarkers can be used to guide the optimum frequency of second primary malignancy surveillance, which may lead to early diagnosis and better survival outcome.

Dysregulation of the miR-25-IMPA2 axis promotes metastatic progression in clear cell renal cell carcinoma

Background

The molecular mechanism underlying clear cell renal cell carcinoma (ccRCC) metastasis remains unclear. We therefore aimed to elucidate the role of IMPA2 in ccRCC metastatic progression.

Methods

Using the Cancer Genome Atlas (TCGA) database and immunohistochemistry (IHC) staining, we investigated differences in IMPA2 mRNA and protein expression, as well as their clinical relevance, in ccRCC. To investigate the function of IMPA2 in ccRCC metastasis, we performed in vitro migration and in vivo lung colony-forming assays. We further explored the effect of microRNA (miR)-25 on IMPA2 expression by performing a luciferase reporter assay.

Findings

We show that ccRCC expresses relatively lower transcript levels of IMPA2 than normal kidney tissue. IMPA2 downregulation was greater in high-grade ccRCC than in low-grade ccRCC and was correlated with a poor prognosis in ccRCC patients. Importantly, we demonstrate that IMPA2 expression is inversely associated with the metastatic potential of ccRCC cells. We found that IMPA2 knockdown promotes, but overexpression suppresses, the cellular migration and lung colony-forming abilities of ccRCC cells. By using in silico and luciferase reporter assays, we found that IMPA2 expression is primarily influenced by miR-25 in ccRCC cells. Significantly, the inhibition of miR-25 function restored IMPA2 expression, thereby diminishing the metastatic potential of ccRCC cells.

Interpretation

We conclude that miR-25-mediated IMPA2 downregulation constitutes a novel signature for cancer metastasis and poor outcomes in ccRCC. We further postulate that the therapeutic targeting of miR-25 can be useful for preventing the metastatic progression of ccRCC associated with IMPA2 downregulation.

Fund

This study was supported by the Ministry of Science and Technology, Taiwan (MOST 107-2314-B-038-094, MOST 106-2314-B-038-069-MY3, MOST 105-2320-B-038-021-MY3 and MOST 107-2320-B-038-056).

Immunolocalization of IP3R and V-ATPase in Ameloblastomas

The goal of this study was to investigate the immunolocalization of inositol 1,4,5-trisphosphate receptor (IP3R) and vacuolar ATPase (V-ATPase) in ameloblastomas with special attention to the invasive front. Thirty-seven cases of previously diagnosed formalin-fixed paraffin-embedded (FFPE) human ameloblastoma samples were selected for this study. The samples were grouped according to the predominant histologic pattern and comprised twelve plexiform, eighteen follicular, and seven unicystic ameloblastomas. Of the unicystic variants, six demonstrated purely luminal and intraluminal growth, and one displayed mural extension. One granular cell variant was included in the follicular ameloblastoma group. All specimens were evaluated for IP3R and V-ATPase expression by immunohistochemistry (IHC). IP3R was positive in columnar cells, similar to ameloblasts, and non-peripheral cells in all samples. In the area of tumor protrusion and front of invasion, membranous and cystoplasmic IP3R expression was observed. In contrast, areas adjacent to tumoral protrusion demonstrated only membranous staining patterns. V-ATPase was not expressed in peripheral columnar cells of the unicystic and granular cell variants of ameloblastoma; however, strong staining was present in these cells in plexiform ameloblastomas, follicular ameloblastomas, and areas of mural growth of unicystic ameloblastomas. In areas of tumor protrusion, reactivity for V-ATPase was observed with both membranous and cytoplasmic staining, while other areas showed only membranous V-ATPase. These findings suggest that concomitant immunolocalization of IP3R and V-ATPase, with both cytoplasmic and membranous expression in the peripheral columnar cells, may indicate the invasive potential of ameloblastomas. Furthermore, these results suggest the tumoral spread of ameloblastomas may be correlated with the autophagy process and channelopathy. The expression of these proteins could establish a baseline for future research and provide therapeutic targets for treatment of ameloblastomas.

Targeting Ca2+ signalling through phytomolecules to combat cancer

Cancer is amongst the life-threatening public health issue worldwide, hence responsible for millions of death every year. It is affecting human health regardless of their gender, age, eating habits, and ecological location. Many drugs and therapies are available for its cure still the need for effective targeted drugs and therapies are of paramount importance. In the recent past, Ca²⁺ signalling (including channels/transporters/pumps) are being studied as a plausible target for combating the cancer menace. Many evidence has shown that the intracellular Ca²⁺ homeostasis is altered in cancer cells and the remodelling is linked with tumor instigation, angiogenesis, progression, and metastasis. Focusing on these altered Ca²⁺ signalling tool kit for cancer treatment is a cross-cutting and emerging area of research. In addition, there are numerous phytomolecules which can be exploited as a potential Ca²⁺ (channels/transporters/ pumps) modulators in the context of targeting Ca²⁺ signalling in the cancer cell. In the present review, a list of plant-based potential Ca²⁺ (channel/transporters/pumps) modulators has been reported which could have application in the framework of repurposing the potential drugs to target Ca²⁺ signalling pathways in cancer cells. This review also aims to gain attention in and support for prospective research in this field.

Type 3 inositol 1,4,5-trisphosphate receptor has antiapoptotic and proliferative role in cancer cells

Although the involvement of type 1 (IP₃R1) and type 2 (IP₃R2) inositol 1,4,5-trisphosphate receptors in apoptosis induction has been well documented in different cancer cells and tissues, the function of type 3 IP₃R (IP₃R3) is still elusive. Therefore, in this work we focused on the role of IP₃R3 in tumor cells in vitro and in vivo. We determined increased expression of this receptor in clear cell renal cell carcinoma compared to matched unaffected part of the kidney from the same patient. Thus, we hypothesized about different functions of IP₃R3 compared to IP₃R1 and IP₃R2 in tumor cells. Silencing of IP₃R1 prevented apoptosis induction in colorectal cancer DLD1 cells, ovarian cancer A2780 cells, and clear cell renal cell carcinoma RCC4 cells, compared to apoptosis in cells treated with scrambled siRNA. As expected, silencing of IP₃R3 and subsequent apoptosis induction resulted in increased levels of apoptosis in all these cells. Further, we prepared a DLD1/IP₃R3_del cell line using CRISPR/Cas9 gene editing method. These cells were injected into nude mice and tumor's volume was compared with tumors induced by DLD1 cells. Lower volume of tumors originated from DLD1/IP₃R3_del cells was observed after 12 days, compared to wild type DLD1 cells. Also, the migration of these cells was lesser compared to wild type DLD1 cells. Apoptosis under hypoxic conditions was more pronounced in DLD1/IP₃R3_del cells than in DLD1 cells. These results clearly show that IP₃R3 has proliferative and anti-apoptotic effect in tumor cells, on contrary to the pro-apoptotic effect of IP₃R1.

Mitochondrial calcium: Transport and modulation of cellular processes in homeostasis and cancer (Review)

In addition to their role in providing cellular energy, mitochondria fulfill a key function in cellular calcium management. The present review provides an integrative view of cellular and mitochondrial calcium homeostasis, and discusses how calcium regulates mitochondrial dynamics and functionality, thus affecting various cellular processes. Calcium crosstalk exists in the domain created between the endoplasmic reticulum and mitochondria, which is known as the mitochondria‑associated membrane (MAM), and controls cellular homeostasis. Calcium signaling participates in numerous biochemical and cellular processes, where calcium concentration, temporality and durability are part of a regulated, finely tuned interplay in non‑transformed cells. In addition, cancer cells modify their MAMs, which consequently affects calcium homeostasis to support mesenchymal transformation, migration, invasiveness, metastasis and autophagy. Alterations in calcium homeostasis may also support resistance to apoptosis, which is a serious problem facing current chemotherapeutic treatments. Notably, mitochondrial dynamics are also affected by mitochondrial calcium concentration to promote cancer survival responses. Dysregulated levels of mitochondrial calcium, alongside other signals, promote mitoflash generation in tumor cells, and an increased frequency of mitoflashes may induce epithelial‑to‑mesenchymal transition. Therefore, cancer cells remodel their calcium balance through numerous mechanisms that support their survival and growth.

Calcium, mitochondria and cell metabolism: A functional triangle in bioenergetics

The versatility of mitochondrial metabolism and its fine adjustments to specific physiological or pathological conditions regulate fundamental cell pathways, ranging from proliferation to apoptosis. In particular, Ca²⁺ signalling has emerged as a key player exploited by mitochondria to tune their activity according with cell demand. The functional interaction between mitochondria and endoplasmic reticulum (ER) deeply impacts on the correct mitochondrial Ca²⁺ signal, thus modulating cell bioenergetics and functionality. Indeed, Ca²⁺ released by the ER is taken up by mitochondria where, both in the intermembrane space and in the matrix, it regulates the activity of transporters, enzymes and proteins involved in organelles' metabolism. In this review, we will briefly summarize Ca²⁺-dependent mechanisms involved in the regulation of mitochondrial activity. Moreover, we will discuss some recent reports, in which alterations in mitochondrial Ca²⁺ signalling have been associated with specific pathological conditions, such as neurodegeneration and cancer.

Pathophysiological consequences of isoform-specific IP3 receptor mutations

Ca²⁺ signaling governs a diverse range of cellular processes and, as such, is subject to tight regulation. A main component of the complex intracellular Ca²⁺-signaling network is the inositol 1,4,5-trisphosphate (IP₃) receptor (IP₃R), a tetrameric channel that mediates Ca²⁺ release from the endoplasmic reticulum (ER) in response to IP₃. IP₃R function is controlled by a myriad of factors, such as Ca²⁺, ATP, kinases and phosphatases and a plethora of accessory and regulatory proteins. Further complexity in IP₃R-mediated Ca²⁺ signaling is the result of the existence of three main isoforms (IP₃R1, IP₃R2 and IP₃R3) that display distinct functional characteristics and properties. Despite their abundant and overlapping expression profiles, IP₃R1 is highly expressed in neurons, IP₃R2 in cardiomyocytes and hepatocytes and IP₃R3 in rapidly proliferating cells as e.g. epithelial cells. As a consequence, dysfunction and/or dysregulation of IP₃R isoforms will have distinct pathophysiological outcomes, ranging from neurological disorders for IP₃R1 to dysfunctional exocrine tissues and autoimmune diseases for IP₃R2 and -3. Over the past years, several IP₃R mutations have surfaced in the sequence analysis of patient-derived samples. Here, we aimed to provide an integrative overview of the clinically most relevant mutations for each IP₃R isoform and the subsequent molecular mechanisms underlying the etiology of the disease.

Role of Mitochondria-Associated ER Membranes in Calcium Regulation in Cancer-Specific Settings

Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are highly specialized subcellular compartments that are shaped by ER subdomains juxtaposed to mitochondria but are biochemically distinct from pure ER and pure mitochondria. MAMs are enriched in enzymes involved in lipid synthesis and transport, channels for calcium transfer, and proteins with oncogenic/oncosuppressive functions that modulate cell signaling pathways involved in physiological and pathophysiological processes. The term "cancer" denotes a group of disorders that result from uncontrolled cell growth driven by a mixture of genetic and environmental components. Alterations in MAMs are thought to account for the onset as well as the progression and metastasis of cancer and have been a focus of investigation in recent years. In this review, we present the current state of the art regarding MAM-resident proteins and their relevance, alterations, and deregulating functions in different types of cancer from a cell biology and clinical perspective.

ITPR3 gene haplotype is associated with cervical squamous cell carcinoma risk in Taiwanese women

Host immunogenetic background plays an important role in human papillomavirus (HPV) infection and cervical cancer development. Inositol 1,4,5-triphosphate receptor type 3 (ITPR3) is essential for both immune activation and cancer pathogenesis. We aim to investigate if ITPR3 genetic polymorphisms are associated with the risk of cervical cancer in Taiwanese women. ITPR3 rs3748079 A/G and rs2229634 C/T polymorphisms were genotyped in a hospital-based study of 462 women with cervical squamous cell carcinoma (CSCC) and 921 age-matched healthy control women. The presence and genotypes of HPV in CSCC was determined. No significant association of individual ITPR3 variants were found among controls, CSCC, and HPV-16 positive CSCC. However, we found a significant association of haplotype AT between CSCC and controls (OR = 2.28, 95% CI 1.31-3.97, P = 2.83 × 10-3) and the OR increased further in CSCC patients infected with HPV-16 (OR = 2.89, 95% CI 1.55-5.37, P = 4.54 × 10-4). The linkage disequilibrium analysis demonstrated that ITPR3 association with CSCC was independent of HLA-DRB1 alleles. In conclusion, these findings suggest that AT haplotype in the ITPR3 gene may serve as a potential marker for genetic susceptibility to CSCC.

The BAX/BAK-like protein BOK is a prognostic marker in colorectal cancer

The intrinsic or mitochondrial apoptosis pathway is controlled by the interaction of antiapoptotic and pro-apoptotic members of the BCL-2 protein family. Activation of this death pathway plays a crucial role in cancer progression and chemotherapy responses. The BCL-2-related ovarian killer (BOK) possesses three BCL-2 homology domains and has been proposed to act in a similar pro-apoptotic pathway as the pro-apoptotic proteins BAX and BAK. In this study, we showed that stage II and III colorectal cancer patients possessed decreased levels of BOK protein in their tumours compared to matched normal tissue. BOK protein levels in tumours were also prognostic of clinical outcome but increased BOK protein levels surprisingly associated with earlier disease recurrence and reduced overall survival. We found no significant association of BOK protein tumour levels with ER stress markers GRP78 or GRP94 or with cleaved caspase-3. In contrast, BOK protein levels correlated with Calreticulin. These data indicate BOK as a prognostic marker in colorectal cancer and suggest that different activities of BOK may contribute to cancer progression and prognosis.

Cancer-selective cytotoxic Ca2+ overload in acute myeloid leukemia cells and attenuation of disease progression in mice by synergistically acting polyphenols curcumin and carnosic acid

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by extremely heterogeneous molecular and biologic abnormalities that hamper the development of effective targeted treatment modalities. While AML cells are highly sensitive to cytotoxic Ca²⁺ overload, the feasibility of Ca²⁺- targeted therapy of this disease remains unclear. Here, we show that apoptotic response of AML cells to the synergistically acting polyphenols curcumin (CUR) and carnosic acid (CA), combined at low, non-cytotoxic doses of each compound was mediated solely by disruption of cellular Ca²⁺ homeostasis. Specifically, activation of caspase cascade in CUR+CA-treated AML cells resulted from sustained elevation of cytosolic Ca²⁺ (Ca²⁺_cyt) and was not preceded by endoplasmic reticulum stress or mitochondrial damage. The CUR+CA-induced Ca²⁺_cyt rise did not involve excessive influx of extracellular Ca²⁺ but, rather, occurred due to massive Ca²⁺ release from intracellular stores concomitant with inhibition of Ca²⁺_cyt extrusion through the plasma membrane. Notably, the CUR+CA combination did not alter Ca²⁺ homeostasis and viability in non-neoplastic hematopoietic cells, suggesting its cancer-selective action. Most importantly, co-administration of CUR and CA to AML-bearing mice markedly attenuated disease progression in two animal models. Collectively, our results provide the mechanistic and translational basis for further characterization of this combination as a prototype of novel Ca²⁺-targeted pharmacological tools for the treatment of AML.

Endoplasmic Reticulum-Mitochondria Calcium Communication and the Regulation of Mitochondrial Metabolism in Cancer: A Novel Potential Target

Cancer is characterized by an uncontrolled cell proliferation rate even under low nutrient availability, which is sustained by a metabolic reprograming now recognized as a hallmark of cancer. Warburg was the first to establish the relationship between cancer and mitochondria; however, he interpreted enhanced aerobic glycolysis as mitochondrial dysfunction. Today it is accepted that many cancer cell types need fully functional mitochondria to maintain their homeostasis. Calcium (Ca²⁺)—a key regulator of several cellular processes—has proven to be essential for mitochondrial metabolism. Inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca²⁺ transfer from the endoplasmic reticulum to the mitochondria through the mitochondrial calcium uniporter (MCU) proves to be essential for the maintenance of mitochondrial function and cellular energy balance. Both IP3R and MCU are overexpressed in several cancer cell types, and the inhibition of the Ca²⁺ communication between these two organelles causes proliferation arrest, migration decrease, and cell death through mechanisms that are not fully understood. In this review, we summarize and analyze the current findings in this area, emphasizing the critical role of Ca²⁺ and mitochondrial metabolism in cancer and its potential as a novel therapeutic target.

The Shigella type III effector IpgD recodes Ca2+ signals during invasion of epithelial cells

The role of second messengers in the diversion of cellular processes by pathogens remains poorly studied despite their importance. Among these, Ca2+ virtually regulates all known cell processes, including cytoskeletal reorganization, inflammation, or cell death pathways. Under physiological conditions, cytosolic Ca2+ increases are transient and oscillatory, defining the so-called Ca2+ code that links cell responses to specific Ca2+ oscillatory patterns. During cell invasion, Shigella induces atypical local and global Ca2+ signals. Here, we show that by hydrolyzing phosphatidylinositol-(4,5)bisphosphate, the Shigella type III effector IpgD dampens inositol-(1,4,5)trisphosphate (InsP3) levels. By modifying InsP3 dynamics and diffusion, IpgD favors the elicitation of long-lasting local Ca2+ signals at Shigella invasion sites and converts Shigella-induced global oscillatory responses into erratic responses with atypical dynamics and amplitude. Furthermore, IpgD eventually inhibits InsP3-dependent responses during prolonged infection kinetics. IpgD thus acts as a pathogen regulator of the Ca2+ code implicated in a versatility of cell functions. Consistent with this function, IpgD prevents the Ca2+-dependent activation of calpain, thereby preserving the integrity of cell adhesion structures during the early stages of infection.

Downregulation of type 3 inositol (1,4,5)-trisphosphate receptor decreases breast cancer cell migration through an oscillatory Ca2+ signal

Breast cancer remains a research priority due to its invasive phenotype. Although the role of ion channels in cancer is now well established, the role of inositol (1,4,5)-trisphosphate (IP₃) receptors (IP₃Rs) remains enigmatic. If the three IP₃Rs subtypes expression have been identified in various cancers, little is known about their physiological role. Here, we investigated the involvement of IP₃R type 3 (IP₃R₃) in the migration processes of three human breast cancer cell lines showing different migration velocities: the low-migrating MCF-7 and the highly migrating and invasive MDA-MB-231 and MDA-MB-435S cell lines. We show that a higher IP₃R3 expression level, but not IP₃R1 nor IP₃R2, is correlated to a stronger cell line migration capacity and a sustained calcium signal. Interestingly, silencing of IP₃R3 highlights an oscillating calcium signaling profile and leads to a significant decrease of cell migration capacities of the three breast cancer cell lines. Conversely, stable overexpression of IP₃R3 in MCF-7 cells significantly increases their migration capacities. This effect is completely reversed by IP₃R3 silencing. In conclusion, we demonstrate that IP₃R3 expression level increases the migration capacity of human breast cancer cells by changing the calcium signature.

The Regulation of Tumor Cell Invasion and Metastasis by Endoplasmic Reticulum-to-Mitochondrial Ca2+ Transfer

Cell migration is one of the many processes orchestrated by calcium (Ca²⁺) signaling, and its dysregulation drives the increased invasive and metastatic potential of cancer cells. The ability of Ca²⁺ to function effectively as a regulator of migration requires the generation of temporally complex signals within spatially restricted microdomains. The generation and maintenance of these Ca²⁺ signals require a specific structural architecture and tightly regulated communication between the extracellular space, intracellular organelles, and cytoplasmic compartments. New insights into how Ca²⁺ microdomains are shaped by interorganellar Ca²⁺ communication have shed light on how Ca²⁺ coordinates cell migration by directing cellular polarization and the rearrangement of structural proteins. Importantly, we are beginning to understand how cancer subverts normal migration through the activity of oncogenes and tumor suppressors that impinge directly on the physiological function or expression levels of Ca²⁺ signaling proteins. In this review, we present and discuss research at the forefront of interorganellar Ca²⁺ signaling as it relates to cell migration, metastasis, and cancer progression, with special focus on endoplasmic reticulum-to-mitochondrial Ca²⁺ transfer.

Transcriptomic Analysis of Calcium Remodeling in Colorectal Cancer

Colorectal cancer (CRC) cells undergo the remodeling of intracellular Ca²⁺ homeostasis, which contributes to cancer hallmarks such as enhanced proliferation, invasion and survival. Ca²⁺ remodeling includes critical changes in store-operated Ca²⁺ entry (SOCE) and Ca²⁺ store content. Some changes have been investigated at the molecular level. However, since nearly 100 genes are involved in intracellular Ca²⁺ transport, a comprehensive view of Ca²⁺ remodeling in CRC is lacking. We have used Next Generation Sequencing (NGS) to investigate differences in expression of 77 selected gene transcripts involved in intracellular Ca²⁺ transport in CRC. To this end, mRNA from normal human colonic NCM460 cells and human colon cancer HT29 cells was isolated and used as a template for transcriptomic sequencing and expression analysis using Ion Torrent technology. After data transformation and filtering, exploratory analysis revealed that both cell types were well segregated. In addition, differential gene expression using R and bioconductor packages show significant differences in expression of selected voltage-operated Ca²⁺ channels and store-operated Ca²⁺ entry players, transient receptor potential (TRP) channels, Ca²⁺ release channels, Ca²⁺ pumps, Na⁺/Ca²⁺ exchanger isoforms and genes involved in mitochondrial Ca²⁺ transport. These data provide the first comprehensive transcriptomic analysis of Ca²⁺ remodeling in CRC.

1H NMR Metabolomics Reveals Association of High Expression of Inositol 1, 4, 5 Trisphosphate Receptor and Metabolites in Breast Cancer Patients

¹H NMR is used to detect alterations in metabolites and their linkage to metabolic processes in a number of pathological conditions including breast cancer. Inositol 1, 4, 5 trisphosphate (IP₃R) receptor is an intracellular calcium channel known to regulate metabolism and cellular bioenergetics. Its expression is up regulated in a number of cancers. However, its linkage to metabolism in disease conditions has not been evaluated. This study was designed to determine the association if any, of these metabolites with altered expression of IP3R in breast cancer. We used ¹H NMR to identify metabolites in the serum of breast cancer patients (n = 27) and performed Real-time Polymerase Chain Reaction analysis for quantifying the expression of IP₃R type 3 and type 2 in tissues from breast cancer patients (n = 40). Principal Component Analysis (PCA) and Partial Least Square-Discriminant Analysis (PLS-DA) clearly distinguished patients with high/low IP₃R expression from healthy subjects. The present study revealed high expression of IP₃R type 2 and type 3 in human breast tumor tissue compared to adjacent non-tumorous tissue. Moreover, patients with ≥ 2-fold increase in IP₃R (high IP₃R group) had significantly higher concentration of metabolic intermediates compared to those with < 2-fold increase in IP₃R (low IP₃R group). We observed an increase in lipoprotein content and the levels of metabolites like lactate, lysine and alanine and a decrease in the levels of pyruvate and glucose in serum of high IP₃R group patients when compared to those in healthy subjects. Receiver operating characteristic (ROC) curve analysis was performed to show the clinical utility of metabolites. In addition to the human studies, functional relevance of IP₃Rs in causing metabolic disruption was observed in MCF-7 and MDA MB-231 cells. Results from our studies bring forth the importance of metabolic (or metabolomics) profiling of serum by ¹H NMR in conjunction with tissue expression studies for characterizing breast cancer patients. The results from this study provide new insights into relationship of breast cancer metabolites with IP₃R.

Targeting calcium signaling in cancer therapy

The intracellular calcium ions (Ca2+) act as second messenger to regulate gene transcription, cell proliferation, migration and death. Accumulating evidences have demonstrated that intracellular Ca2+ homeostasis is altered in cancer cells and the alteration is involved in tumor initiation, angiogenesis, progression and metastasis. Targeting derailed Ca2+ signaling for cancer therapy has become an emerging research area. This review summarizes some important Ca2+ channels, transporters and Ca2+-ATPases, which have been reported to be altered in human cancer patients. It discusses the current research effort toward evaluation of the blockers, inhibitors or regulators for Ca2+ channels/transporters or Ca2+-ATPase pumps as anti-cancer drugs. This review is also aimed to stimulate interest in, and support for research into the understanding of cellular mechanisms underlying the regulation of Ca2+ signaling in different cancer cells, and to search for novel therapies to cure these malignancies by targeting Ca2+ channels or transporters.

Structural and dynamic insights into the subtype-specific IP3-binding mechanism of the IP3 receptor

There are three subtypes of vertebrate inositol 1,4,5-trisphosphate (IP3) receptor (IP3R), a Ca2+-release channel on the ER membrane — IP3R1, IP3R2, and IP3R3 — each of which has a distinctive role in disease development. To determine the subtype-specific IP3-binding mechanism, we compared the thermodynamics, thermal stability, and conformational dynamics between the N-terminal regions of IP3R1 (IP3R1-NT) and IP3R3 (IP3R3-NT) by performing circular dichroism (CD), isothermal titration calorimetry (ITC), and hydrogen–deuterium exchange mass spectrometry (HDX-MS). Previously determined crystal structures of IP3R1-NT and HDX-MS results from this study revealed that both IP3R1 and IP3R3 adopt a similar IP3-binding mechanism. However, several regions, including the α- and β-interfaces, of IP3R1-NT and IP3R3-NT show significantly different conformational dynamics upon IP3 binding, which may explain the different IP3-binding affinities between the subtypes. The importance of the interfaces for subtype-specific IP3 binding is also supported by the different dynamic conformations of the two subtypes in the apo-states. Furthermore, IP3R1-NT and IP3R3-NT show different IP3-binding affinities and thermal stabilities, but share similar thermodynamic properties for IP3 binding. These results collectively provide new insights into the mechanism underlying IP3 binding to IP3Rs and the subtype-specific regulatory mechanism.

The Inositol Trisphosphate/Calcium Signaling Pathway in Health and Disease

Many cellular functions are regulated by calcium (Ca2+) signals that are generated by different signaling pathways. One of these is the inositol 1,4,5-trisphosphate/calcium (InsP3/Ca2+) signaling pathway that operates through either primary or modulatory mechanisms. In its primary role, it generates the Ca2+ that acts directly to control processes such as metabolism, secretion, fertilization, proliferation, and smooth muscle contraction. Its modulatory role occurs in excitable cells where it modulates the primary Ca2+ signal generated by the entry of Ca2+ through voltage-operated channels that releases Ca2+ from ryanodine receptors (RYRs) on the internal stores. In carrying out this modulatory role, the InsP3/Ca2+ signaling pathway induces subtle changes in the generation and function of the voltage-dependent primary Ca2+ signal. Changes in the nature of both the primary and modulatory roles of InsP3/Ca2+ signaling are a contributory factor responsible for the onset of a large number human diseases.

Impact of intracellular ion channels on cancer development and progression

Cancer research is nowadays focused on the identification of possible new targets in order to try to develop new drugs for curing untreatable tumors. Ion channels have emerged as "oncogenic" proteins, since they have an aberrant expression in cancers compared to normal tissues and contribute to several hallmarks of cancer, such as metabolic re-programming, limitless proliferative potential, apoptosis-resistance, stimulation of neo-angiogenesis as well as cell migration and invasiveness. In recent years, not only the plasma membrane but also intracellular channels and transporters have arisen as oncological targets and were proposed to be associated with tumorigenesis. Therefore, the research is currently focusing on understanding the possible role of intracellular ion channels in cancer development and progression on one hand and, on the other, on developing new possible drugs able to modulate the expression and/or activity of these channels. In a few cases, the efficacy of channel-targeting drugs in reducing tumors has already been demonstrated in vivo in preclinical mouse models.

Altered expression of stromal interaction molecule (STIM)-calcium release-activated calcium channel protein (ORAI) and inositol 1,4,5-trisphosphate receptors (IP3Rs) in cancer: will they become a new battlefield for oncotherapy?

The stromal interaction molecule (STIM)-calcium release-activated calcium channel protein (ORAI) and inositol 1,4,5-trisphosphate receptors (IP₃Rs) play pivotal roles in the modulation of Ca²⁺-regulated pathways from gene transcription to cell apoptosis by driving calcium-dependent signaling processes. Increasing evidence has implicated the dysregulation of STIM–ORAI and IP₃Rs in tumorigenesis and tumor progression. By controlling the activities, structure, and/or expression levels of these Ca²⁺-transporting proteins, malignant cancer cells can hijack them to drive essential biological functions for tumor development. However, the molecular mechanisms underlying the participation of STIM–ORAI and IP₃Rs in the biological behavior of cancer remain elusive. In this review, we summarize recent advances regarding STIM–ORAI and IP₃Rs and discuss how they promote cell proliferation, apoptosis evasion, and cell migration through temporal and spatial rearrangements in certain types of malignant cells. An understanding of the essential roles of STIM–ORAI and IP₃Rs may provide new pharmacologic targets that achieve a better therapeutic effect by inhibiting their actions in key intracellular signaling pathways.

Selective Vulnerability of Cancer Cells by Inhibition of Ca(2+) Transfer from Endoplasmic Reticulum to Mitochondria

In the absence of low-level ER-to-mitochondrial Ca(2+) transfer, ATP levels fall, and AMPK-dependent, mTOR-independent autophagy is induced as an essential survival mechanism in many cell types. Here, we demonstrate that tumorigenic cancer cell lines, transformed primary human fibroblasts, and tumors in vivo respond similarly but that autophagy is insufficient for survival, and cancer cells die while their normal counterparts are spared. Cancer cell death is due to compromised bioenergetics that can be rescued with metabolic substrates or nucleotides and caused by necrosis associated with mitotic catastrophe during their proliferation. Our findings reveal an unexpected dependency on constitutive Ca(2+) transfer to mitochondria for viability of tumorigenic cells and suggest that mitochondrial Ca(2+) addiction is a feature of cancer cells.

Hypoxic conditions increases H₂S-induced ER stress in A2870 cells

Hypoxia - a state of lower oxygen demand-is responsible for a higher aggressiveness of tumors and therefore a worse prognosis. During hypoxia, several metabolic pathways are re-organized, e.g., energetic metabolism, modulation of pH, and calcium transport. Calcium is an important second messenger that regulates variety of processes in the cell. Thus, aim of this work was to compare H2S modulation of the intracellular calcium transport systems in hypoxia and in cells grown in standard culture conditions. For all experiments, we used ovarian cancer cell line (A2780). H2S is a novel gasotransmitter, known to be involved in a modulation of several calcium transport systems, thus resulting in altered calcium signaling. Two models of hypoxia were used in our study-chemical (induced by dimethyloxallyl glycine) and 2 % O2 hypoxia, both combined with a treatment using a slow H2S donor GYY4137. In hypoxia, we observed rapid changes in cytosolic and reticular calcium levels compared to cells grown in standard culture conditions, and these changes were even more exagerrated when combined with the GYY4137. Changes in a calcium homeostasis result from IP3 receptor´s up-regulation and down-regulation of the SERCA 2, which leads to a development of the endoplasmic reticulum stress. Based on our results, we propose a higher vulnerability of calcium transport systems to H2S regulation under hypoxia.

BRAFV600E-Associated Gene Expression Profile: Early Changes in the Transcriptome, Based on a Transgenic Mouse Model of Papillary Thyroid Carcinoma

Background

The molecular mechanisms driving the papillary thyroid carcinoma (PTC) are still poorly understood. The most frequent genetic alteration in PTC is the BRAFV600E mutation–its impact may extend even beyond PTC genomic profile and influence the tumor characteristics and even clinical behavior.

Methods

In order to identify BRAF-dependent signature of early carcinogenesis in PTC, a transgenic mouse model with BRAFV600E-induced PTC was developed. Mice thyroid samples were used in microarray analysis and the data were referred to a human thyroid dataset.

Results

Most of BRAF(+) mice developed malignant lesions. Nevertheless, 16% of BRAF(+) mice displayed only benign hyperplastic lesions or apparently asymptomatic thyroids. After comparison of non-malignant BRAF(+) thyroids to BRAF(−) ones, we selected 862 significantly deregulated genes. When the mouse BRAF-dependent signature was transposed to the human HG-U133A microarray, we identified 532 genes, potentially indicating the BRAF signature (representing early changes, not related to developed malignant tumor). Comparing BRAF(+) PTCs to healthy human thyroids, PTCs without BRAF and RET alterations and RET(+), RAS(+) PTCs, 18 of these 532 genes displayed significantly deregulated expression in all subgroups. All 18 genes, among them 7 novel and previously not reported, were validated as BRAFV600E-specific in the dataset of independent PTC samples, made available by The Cancer Genome Atlas Project.

Conclusion

The study identified 7 BRAF-induced genes that are specific for BRAF V600E-driven PTC and not previously reported as related to BRAF mutation or thyroid carcinoma: MMD, ITPR3, AACS, LAD1, PVRL3, ALDH3B1, and RASA1. The full signature of BRAF-related 532 genes may encompass other BRAF-related important transcripts and require further study.

Genetic landscape of metastatic and recurrent head and neck squamous cell carcinoma

BACKGROUND

Recurrence and/or metastasis occurs in more than half of patients with head and neck squamous cell carcinoma (HNSCC), and these events pose the greatest threats to long-term survival. We set out to identify genetic alterations that underlie recurrent/metastatic HNSCC.

METHODS

Whole-exome sequencing (WES) was performed on genomic DNA extracted from fresh-frozen whole blood and patient-matched tumor pairs from 13 HNSCC patients with synchronous lymph node metastases and 10 patients with metachronous recurrent tumors. Mutational concordance within and between tumor pairs was used to analyze the spatiotemporal evolution of HNSCC in individual patients and to identify potential therapeutic targets for functional evaluation.

RESULTS

Approximately 86% and 60% of single somatic nucleotide variants (SSNVs) identified in synchronous nodal metastases and metachronous recurrent tumors, respectively, were transmitted from the primary index tumor. Genes that were mutated in more than one metastatic or recurrent tumor, but not in the respective primary tumors, include C17orf104, inositol 1,4,5-trisphosphate receptor, type 3 (ITPR3), and discoidin domain receptor tyrosine kinase 2 (DDR2). Select DDR2 mutations have been shown to confer enhanced sensitivity to SRC-family kinase (SFK) inhibitors in other malignancies. Similarly, HNSCC cell lines harboring endogenous and engineered DDR2 mutations were more sensitive to the SFK inhibitor dasatinib than those with WT DDR2.

CONCLUSION

In this WES study of patient-matched tumor pairs in HNSCC, we found synchronous lymph node metastases to be genetically more similar to their paired index primary tumors than metachronous recurrent tumors. This study outlines a compendium of somatic mutations in primary, metastatic, and/or recurrent HNSCC cancers, with potential implications for precision medicine approaches.

FUNDING

National Cancer Institute, American Cancer Society, Agency for Science, Technology and Research of Singapore, and Gilead Sciences Inc.

Calcium signaling and secretion in cholangiocytes

Alcoholic hepatitis affects up to one-third of individuals who abuse alcohol and can be associated with high mortality. Although this disorder is characterized by hepatocellular damage, steatosis and neutrophil infiltration, recent evidence suggests that cholestasis or impaired bile secretion may be a frequent occurrence as well. Bile secretion results from the concerted activity of hepatocytes and cholangiocytes, the epithelial cells that line the bile ducts. Hepatocytes secrete bile acids and conjugated products into the bile canaliculi, which then are modified by cholangiocytes through secretion of bicarbonate and water to give rise to the final secreted bile. Here the molecular mechanisms regulating bile secretion in cholangiocytes are reviewed. Moreover, we discuss how the expression of intracellular Ca(2+) channels might be regulated in cholangiocytes, plus evidence that components of the Ca(2+) signaling machinery are altered in a range of cholestatic diseases of the bile ducts.

HOXA5 inhibits metastasis via regulating cytoskeletal remodelling and associates with prolonged survival in non-small-cell lung carcinoma

Homeobox genes comprise a family of regulatory genes that contain a common homeobox domain and act as transcription factors. Recent studies indicate that homeobox A5 (HOXA5) may serve as a tumour suppressor gene in breast cancers. However, the precise role and the underlying mechanism of HOXA5 in lung cancer remain unclear. Oligonucleotide microarrays and an invasion/metastasis lung adenocarcinoma cell line model were used to determine the correlation between HOXA5 expression and cancer cell invasion ability. We found that ectopic expression of HOXA5 in highly invasive cancer cells suppressed cell migration, invasion, and filopodia formation in vitro and inhibited metastatic potential in vivo. Knockdown of HOXA5 promoted the invasiveness of lung cancer cells. In addition, HOXA5 expression was associated with better clinical outcome in non-small cell lung cancer patients with wild-type EGFR. Furthermore, genome-wide transcriptomic and pathway analyses were performed to identify the potential molecular mechanisms. Our data showed that HOXA5 may bind to the promoters of the cytoskeleton-related genes and downregulate their mRNA and protein expression levels. Our studies provide new insights into how HOXA5 may contribute to the suppression of metastasis in lung cancer via cytoskeleton remodelling regulation. Therefore, targeted induction of HOXA5 may represent a promising approach for non-small-cell lung cancer therapy.

ITPR1 protects renal cancer cells against natural killer cells by inducing autophagy

Clear cell renal cell carcinomas (RCC) frequently display inactivation of von Hippel-Lindau (VHL) gene leading to increased level of hypoxia-inducible factors (HIF). In this study, we investigated the potential role of HIF2α in regulating RCC susceptibility to natural killer (NK) cell-mediated killing. We demonstrated that the RCC cell line 786-0 with mutated VHL was resistant to NK-mediated lysis as compared with the VHL-corrected cell line (WT7). This resistance was found to require HIF2α stabilization. On the basis of global gene expression profiling and chromatin immunoprecipitation assay, we found ITPR1 (inositol 1,4,5-trisphosphate receptor, type 1) as a direct novel target of HIF2α and that targeting ITPR1 significantly increased susceptibility of 786-0 cells to NK-mediated lysis. Mechanistically, HIF2α in 786-0 cells lead to overexpression of ITPR1, which subsequently regulated the NK-mediated killing through the activation of autophagy in target cells by NK-derived signal. Interestingly, both ITPR1 and Beclin-1 silencing in 786-0 cells inhibited NK-induced autophagy and subsequently increased granzyme B activity in target cells. Finally, in vivo ITPR1 targeting significantly enhanced the NK-mediated tumor regression. Our data provide insight into the link between HIF2α, the ITPR1-related pathway, and natural immunity and strongly suggest a role for the HIF2α/ITPR1 axis in regulating RCC cell survival.

Structural insights into endoplasmic reticulum stored calcium regulation by inositol 1,4,5-trisphosphate and ryanodine receptors

The two major calcium (Ca²⁺) release channels on the sarco/endoplasmic reticulum (SR/ER) are inositol 1,4,5-trisphosphate and ryanodine receptors (IP3Rs and RyRs). They play versatile roles in essential cell signaling processes, and abnormalities of these channels are associated with a variety of diseases. Structural information on IP3Rs and RyRs determined using multiple techniques including X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy and cryo-electron microscopy (EM), has significantly advanced our understanding of the mechanisms by which these Ca²⁺ release channels function under normal and pathophysiological circumstances. In this review, structural advances on the understanding of the mechanisms of IP3R and RyR function and dysfunction are summarized. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

Post-translational regulation of the type III inositol 1,4,5-trisphosphate receptor by miRNA-506

The type III isoform of the inositol 1,4,5-trisphosphate receptor (InsP3R3) is apically localized and triggers Ca(2+) waves and secretion in a number of polarized epithelia. However, nothing is known about epigenetic regulation of this InsP3R isoform. We investigated miRNA regulation of InsP3R3 in primary bile duct epithelia (cholangiocytes) and in the H69 cholangiocyte cell line, because the role of InsP3R3 in cholangiocyte Ca(2+) signaling and secretion is well established and because loss of InsP3R3 from cholangiocytes is responsible for the impairment in bile secretion that occurs in a number of liver diseases. Analysis of the 3'-UTR of human InsP3R3 mRNA revealed two highly conserved binding sites for miR-506. Transfection of miR-506 mimics into cell lines expressing InsP3R3-3'UTR-luciferase led to decreased reporter activity, whereas co-transfection with miR-506 inhibitors led to enhanced activity. Reporter activity was abrogated in isolated mutant proximal or distal miR-506 constructs in miR-506-transfected HEK293 cells. InsP3R3 protein levels were decreased by miR-506 mimics and increased by inhibitors, and InsP3R3 expression was markedly decreased in H69 cells stably transfected with miR-506 relative to control cells. miR-506-H69 cells exhibited a fibrotic signature. In situ hybridization revealed elevated miR-506 expression in vivo in human-diseased cholangiocytes. Histamine-induced, InsP3-mediated Ca(2+) signals were decreased by 50% in stable miR-506 cells compared with controls. Finally, InsP3R3-mediated fluid secretion was significantly decreased in isolated bile duct units transfected with miR-506, relative to control IBDU. Together, these data identify miR-506 as a regulator of InsP3R3 expression and InsP3R3-mediated Ca(2+) signaling and secretion.

Ion channels in the regulation of apoptosis

Apoptosis, a type of genetically controlled cell death, is a fundamental cellular mechanism utilized by multicellular organisms for disposal of cells that are no longer needed or potentially detrimental. Given the crucial role of apoptosis in physiology, deregulation of apoptotic machinery is associated with various diseases as well as abnormalities in development. Acquired resistance to apoptosis represents the common feature of most and perhaps all types of cancer. Therefore, repairing and reactivating apoptosis represents a promising strategy to fight cancer. Accumulated evidence identifies ion channels as essential regulators of apoptosis. However, the contribution of specific ion channels to apoptosis varies greatly depending on cell type, ion channel type and intracellular localization, pathology as well as intracellular signaling pathways involved. Here we discuss the involvement of major types of ion channels in apoptosis regulation. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Cyst formation following disruption of intracellular calcium signaling

Mutations in polycystin 1 and 2 (PC1 and PC2) cause the common genetic kidney disorder autosomal dominant polycystic kidney disease (ADPKD). It is unknown how these mutations result in renal cysts, but dysregulation of calcium (Ca(2+)) signaling is a known consequence of PC2 mutations. PC2 functions as a Ca(2+)-activated Ca(2+) channel of the endoplasmic reticulum. We hypothesize that Ca(2+) signaling through PC2, or other intracellular Ca(2+) channels such as the inositol 1,4,5-trisphosphate receptor (InsP3R), is necessary to maintain renal epithelial cell function and that disruption of the Ca(2+) signaling leads to renal cyst development. The cell line LLC-PK1 has traditionally been used for studying PKD-causing mutations and Ca(2+) signaling in 2D culture systems. We demonstrate that this cell line can be used in long-term (8 wk) 3D tissue culture systems. In 2D systems, knockdown of InsP3R results in decreased Ca(2+) transient signals that are rescued by overexpression of PC2. In 3D systems, knockdown of either PC2 or InsP3R leads to cyst formation, but knockdown of InsP3R type 1 (InsP3R1) generated the largest cysts. InsP3R1 and InsP3R3 are differentially localized in both mouse and human kidney, suggesting that regional disruption of Ca(2+) signaling contributes to cystogenesis. All cysts had intact cilia 2 wk after starting 3D culture, but the cells with InsP3R1 knockdown lost cilia as the cysts grew. Studies combining 2D and 3D cell culture systems will assist in understanding how mutations in PC2 that confer altered Ca(2+) signaling lead to ADPKD cysts.

A dual role for the anti-apoptotic Bcl-2 protein in cancer: mitochondria versus endoplasmic reticulum

Anti-apoptotic Bcl-2 contributes to cancer formation and progression by promoting the survival of altered cells. Hence, it is a prime target for novel specific anti-cancer therapeutics. In addition to its canonical anti-apoptotic role, Bcl-2 has an inhibitory effect on cell-cycle progression. Bcl-2 acts at two different intracellular compartments, the mitochondria and the endoplasmic reticulum (ER). At the mitochondria, Bcl-2 via its hydrophobic cleft scaffolds the Bcl-2-homology (BH) domain 3 (BH3) of pro-apoptotic Bcl-2-family members. Small molecules (like BH3 mimetics) can disrupt this interaction, resulting in apoptotic cell death in cancer cells. At the ER, Bcl-2 modulates Ca(2+) signaling, thereby promoting proliferation while increasing resistance to apoptosis. Bcl-2 at the ER acts via its N-terminal BH4 domain, which directly binds and inhibits the inositol 1,4,5-trisphosphate receptor (IP3R), the main intracellular Ca(2+)-release channel. Tools targeting the BH4 domain of Bcl-2 reverse Bcl-2's inhibitory action on IP3Rs and trigger pro-apoptotic Ca(2+) signaling in cancer B-cells, including chronic lymphocytic leukemia (CLL) cells and diffuse large B-cell lymphoma (DLBCL) cells. The sensitivity of DLBCL cells to BH4-domain targeting tools strongly correlated with the expression levels of the IP3R2 channel, the IP3R isoform with the highest affinity for IP3. Interestingly, bio-informatic analysis of a database of primary CLL patient cells also revealed a transcriptional upregulation of IP3R2. Finally, this review proposes a model, in which cancer cell survival depends on Bcl-2 at the mitochondria and/or the ER. This dependence likely will have an impact on their responses to BH3-mimetic drugs and BH4-domain targeting tools. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.

Alterations in the rat serum proteome induced by prepubertal exposure to bisphenol a and genistein

Humans are exposed to an array of chemicals via the food, drink and air, including a significant number that can mimic endogenous hormones. One such chemical is Bisphenol A (BPA), a synthetic chemical that has been shown to cause developmental alterations and to predispose for mammary cancer in rodent models. In contrast, the phytochemical genistein has been reported to suppress chemically induced mammary cancer in rodents, and Asians ingesting a diet high in soy containing genistein have lower incidence of breast and prostate cancers. In this study, we sought to: (1) identify protein biomarkers of susceptibility from blood sera of rats exposed prepubertally to BPA or genistein using Isobaric Tandem Mass Tags quantitative mass spectrometry (TMT-MS) combined with MudPIT technology and, (2) explore the relevance of these proteins to carcinogenesis. Prepubertal exposures to BPA and genistein resulted in altered expression of 63 and 28 proteins in rat sera at postnatal day (PND) 21, and of 9 and 18 proteins in sera at PND35, respectively. This study demonstrates the value of using quantitative proteomic techniques to explore the effect of chemical exposure on the rat serum proteome and its potential for unraveling cellular targets altered by BPA and genistein involved in carcinogenesis.

Early insights into the function of KIAA1199, a markedly overexpressed protein in human colorectal tumors

We previously reported that the expression of KIAA1199 in human colorectal tumors (benign and malignant) is markedly higher than that in the normal colonic mucosa. In this study, we investigated the functions of the protein encoded by this gene, which are thus far unknown. Immunostaining studies were used to reveal its subcellular localization, and proteomic and gene expression experiments were conducted to identify proteins that might interact with KIAA1199 and molecular pathways in which it might play roles. Using colon cancer cell lines, we showed that both endogenous and ectopically expressed KIAA1199 is secreted into the extracellular environment. In the cells, it was found mainly in the perinuclear space (probably the ER) and cell membrane. Both cellular compartments were also over-represented in lists of proteins identified by mass spectrometry as putative KIAA1199 interactors and/or proteins encoded by genes whose transcription was significantly changed by KIAA1199 expression. These proteomic and transcriptomic datasets concordantly link KIAA1199 to several genes/proteins and molecular pathways, including ER processes like protein binding, transport, and folding; and Ca²⁺, G-protein, ephrin, and Wnt signaling. Immunoprecipitation experiments confirmed KIAA1199’s interaction with the cell-membrane receptor ephrin A2 and with the ER receptor ITPR3, a key player in Ca²⁺ signaling. By modulating Ca²⁺ signaling, KIAA1199 could affect different branches of the Wnt network. Our findings suggest it may negatively regulate the Wnt/CTNNB1 signaling, and its expression is associated with decreased cell proliferation and invasiveness.

Canonical transient receptor potential 3 channel triggers vascular endothelial growth factor-induced intracellular Ca2+ oscillations in endothelial progenitor cells isolated from umbilical cord blood

Endothelial colony-forming cells (ECFCs) are the only endothelial progenitor cells (EPCs) that are capable of acquiring a mature endothelial phenotype. ECFCs are mainly mobilized from bone marrow to promote vascularization and represent a promising tool for cell-based therapy of severe ischemic diseases. Vascular endothelial growth factor (VEGF) stimulates the proliferation of peripheral blood-derived ECFCs (PB-ECFCs) through oscillations in intracellular Ca(2+) concentration ([Ca(2+)]i). VEGF-induced Ca(2+) spikes are driven by the interplay between inositol-1,4,5-trisphosphate (InsP3)-dependent Ca(2+) release and store-operated Ca(2+) entry (SOCE). The therapeutic potential of umbilical cord blood-derived ECFCs (UCB-ECFCs) has also been shown in recent studies. However, VEGF-induced proliferation of UCB-ECFCs is faster compared with their peripheral counterpart. Unlike PB-ECFCs, UCB-ECFCs express canonical transient receptor potential channel 3 (TRPC3) that mediates diacylglycerol-dependent Ca(2+) entry. The present study aimed at investigating whether the higher proliferative potential of UCB-ECFCs was associated to any difference in the molecular underpinnings of their Ca(2+) response to VEGF. We found that VEGF induces oscillations in [Ca(2+)]i that are patterned by the interaction between InsP3-dependent Ca(2+) release and SOCE. Unlike PB-ECFCs, VEGF-evoked Ca(2+) oscillations do not arise in the absence of extracellular Ca(2+) entry and after pharmacological (with Pyr3 and flufenamic acid) and genetic (by employing selective small interference RNA) suppression of TRPC3. VEGF-induced UCB-ECFC proliferation is abrogated on inhibition of the intracellular Ca(2+) spikes. Therefore, the Ca(2+) response to VEGF in UCB-ECFCs is shaped by a different Ca(2+) machinery as compared with PB-ECFCs, and TRPC3 stands out as a promising target in EPC-based treatment of ischemic pathologies.

Altered Ca(2+) signaling in cancer cells: proto-oncogenes and tumor suppressors targeting IP3 receptors

Proto-oncogenes and tumor suppressors critically control cell-fate decisions like cell survival, adaptation and death. These processes are regulated by Ca(2+) signals arising from the endoplasmic reticulum, which at distinct sites is in close proximity to the mitochondria. These organelles are linked by different mechanisms, including Ca(2+)-transport mechanisms involving the inositol 1,4,5-trisphosphate receptor (IP3R) and the voltage-dependent anion channel (VDAC). The amount of Ca(2+) transfer from the endoplasmic reticulum to mitochondria determines the susceptibility of cells to apoptotic stimuli. Suppressing the transfer of Ca(2+) from the endoplasmic reticulum to the mitochondria increases the apoptotic resistance of cells and may decrease the cellular responsiveness to apoptotic signaling in response to cellular damage or alterations. This can result in the survival, growth and proliferation of cells with oncogenic features. Clearly, proper maintenance of endoplasmic reticulum Ca(2+) homeostasis and dynamics including its links with the mitochondrial network is essential to detect and eliminate altered cells with oncogenic features through the apoptotic pathway. Proto-oncogenes and tumor suppressors exploit the central role of Ca(2+) signaling by targeting the IP3R. There are an increasing number of reports showing that activation of proto-oncogenes or inactivation of tumor suppressors directly affects IP3R function and endoplasmic reticulum Ca(2+) homeostasis, thereby decreasing mitochondrial Ca(2+) uptake and mitochondrial outer membrane permeabilization. In this review, we provide an overview of the current knowledge on the proto-oncogenes and tumor suppressors identified as IP3R-regulatory proteins and how they affect endoplasmic reticulum Ca(2+) homeostasis and dynamics.

Calcium channels and pumps in cancer: changes and consequences

Increases in intracellular free Ca(2+) play a major role in many cellular processes. The deregulation of Ca(2+) signaling is a feature of a variety of diseases, and modulators of Ca(2+) signaling are used to treat conditions as diverse as hypertension to pain. The Ca(2+) signal also plays a role in processes important in cancer, such as proliferation and migration. Many studies in cancer have identified alterations in the expression of proteins involved in the movement of Ca(2+) across the plasma membrane and subcellular organelles. In some cases, these Ca(2+) channels or pumps are potential therapeutic targets for specific cancer subtypes or correlate with prognosis.

Selective modulation of subtype III IP₃R by Akt regulates ER Ca²⁺ release and apoptosis

Ca²⁺ transfer from endoplasmic reticulum (ER) to mitochondria can trigger apoptotic pathways by inducing release of mitochondrial pro-apoptotic factors. Three different types of inositol 1,4,5-trisphosphate receptor (IP₃R) serve to discharge Ca²⁺ from ER, but possess some peculiarities, especially in apoptosis induction. The anti-apoptotic protein Akt can phosphorylate all IP₃R isoforms and protect cells from apoptosis, reducing ER Ca²⁺ release. However, it has not been elucidated which IP₃R subtypes mediate these effects. Here, we show that Akt activation in COS7 cells, which lack of IP₃R I, strongly suppresses IP₃-mediated Ca²⁺ release and apoptosis. Conversely, in SH-SY 5Y cells, which are type III-deficient, Akt is unable to modulate ER Ca²⁺ flux, losing its anti-apoptotic activity. In SH-SY 5Y-expressing subtype III, Akt recovers its protective function on cell death, by reduction of Ca²⁺ release. Moreover, regulating Ca²⁺ flux to mitochondria, Akt maintains the mitochondrial integrity and delays the trigger of apoptosis, in a type III-dependent mechanism. These results demonstrate a specific activity of Akt on IP₃R III, leading to diminished Ca²⁺ transfer to mitochondria and protection from apoptosis, suggesting an additional level of cell death regulation mediated by Akt.