Mechanisms of resveratrol-induced changes in cytosolic free calcium ion concentrations and cell viability in OC2 human oral cancer cells

A systematic review and meta-analysis of the impact of resveratrol on oral cancer: potential therapeutic implications

The present study aimed to investigate the impact of resveratrol on oral neoplastic parameters through a systematic review and meta-analysis. Resveratrol, a naturally occurring polyphenol, has shown promising potential as a therapeutic agent in various cancer types, including oral neoplasms. Understanding the collective findings from existing studies can shed light on the efficacy and mechanisms of resveratrol in oral cancer management. The systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive search was performed to identify relevant studies from various databases, registers, websites, and citation searches. The inclusion criteria encompassed in-vivo studies investigating the impact of resveratrol on oral neoplastic parameters in animal models. After screening and assessment, a total of five eligible studies were included in the meta-analysis. The meta-analysis of the selected studies revealed that resveratrol treatment exhibited a potential impact on reducing oral neoplastic proliferation and promoting neoplastic apoptosis. The combined analysis showed a statistically significant decrease in neoplastic parameters with an overall effect size (ES) of 0.85 (95% CI: [0.74, 0.98]). Subgroup analyses were conducted to explore potential variations among different cellular types and exposure compounds, providing further insights into the efficacy of resveratrol in specific contexts. This systematic review and meta-analysis support the potential of resveratrol as a promising therapeutic agent in oral cancer management. The findings indicate that resveratrol may effectively modulate neoplastic proliferation and apoptosis in various cellular types within animal models of oral cancer. However, further well-controlled studies and clinical trials are warranted to validate these observations and elucidate the underlying mechanisms of resveratrol's actions. Resveratrol holds promise as a complementary therapeutic approach in the prevention and treatment of oral neoplastic conditions.

Applications of resveratrol in the treatment of gastrointestinal cancer

Natural product compounds have lately attracted interest in the scientific community as a possible treatment for gastrointestinal (GI) cancer, due to their anti-inflammatory and anticancer properties. There are many preclinical, clinical, and epidemiological studies, suggesting that the consumption of polyphenol compounds, which are abundant in vegetables, grains, fruits, and pulses, may help to prevent various illnesses and disorders from developing, including several GI cancers. The development of GI malignancies follows a well-known path, in which normal gastrointestinal cells acquire abnormalities in their genetic composition, causing the cells to continuously proliferate, and metastasize to other sites, especially the brain and liver. Natural compounds with the ability to affect oncogenic pathways might be possible treatments for GI malignancies, and could easily be tested in clinical trials. Resveratrol is a non-flavonoid polyphenol and a natural stilbene, acting as a phytoestrogen with anti-cancer, cardioprotective, anti-oxidant, and anti-inflammatory properties. Resveratrol has been shown to overcome resistance mechanisms in cancer cells, and when combined with conventional anticancer drugs, could sensitize cancer cells to chemotherapy. Several new resveratrol analogs and nanostructured delivery vehicles with improved anti-GI cancer efficacy, absorption, and pharmacokinetic profiles have already been developed. This present review focuses on the in vitro and in vivo effects of resveratrol on GI cancers, as well as the underlying molecular mechanisms of action.

Lockdown of mitochondrial Ca2+ extrusion and subsequent resveratrol treatment kill HeLa cells by Ca2+ overload

Anticancer effect of resveratrol and the role of sodium/lithium/calcium exchanger in context with calcium ions are studied in human cervical cancer cell line. This therapeutic approach using siNCLX mediated gene silencing and drug therapy with resveratrol indicates the disruption of calcium homeostasis, increase in caspase (-3, 8, 9) mRNA expressions and DNA damage leading to apoptotic cell death. Monitoring the intracellular Ca2+ changes using fluo-4AM indicates highest rise in [Ca2+] level in sodium/lithium/calcium exchanger silenced group with five different stages, that is distinguishable based on the fluorescence intensity. In resveratrol treated and siNCLX + resveratrol treated groups no such cell staging differences were observed, despite uniform Ca2+ rise followed by decrease in the intensity. Integrating RNAi gene silencing of sodium/lithium/calcium exchanger with resveratrol can form the most interesting, efficient and promising therapeutic strategy in the treatment of cancer.

Resveratrol effects in oral cancer cells: a comprehensive review

Oral cancer is a very common tumor worldwide with high incidence and mortality. The treatment of oral cancer involves surgery, radio- and chemotherapy; however, high failure rates and toxicity are noticed. Thus, the search of new drugs aiming a more effective treatment is welcomed. Natural products present chemopreventive and anti-cancer effects. Resveratrol is a naturally occurring antioxidant that contains several health benefits, including anti-inflammatory and antiproliferative activities. This review discusses the different action mechanisms of resveratrol related in the in vitro and in vivo studies using models of oral cancer.

Combination of Resveratrol and Quercetin Causes Cell Growth Inhibition, DNA Damage, Cell Cycle Arrest, and Apoptosis in Oral Cancer Cells

Resveratrol and quercetin alone are well reported to have anticancer potential, but their combination studies are very inadequate. We have examined their combination in Cal-33 and SCC-15 oral cancer cells (OCCs) and noncancerous HEK-293 cells. Combination of 10 μM concentration of each resveratrol and quercetin brought additive effect on cellular growth, DNA damage, S-phase cell cycle arrest, and cell death in Cal-33 cells but not in the HEK-293 cells. Augmentation of the cell cycle regulatory protein, Cyclin E, and downregulation of Cyclin A possibly caused S-phase arrest in Cal-33 cancer cells. Comet formation and presence of gamma-H2AX foci confirmed DNA damage, and cleavage of PARP1 and upregulation in Bax level specified apoptosis after combined treatment. Ratio of transcription activation and repression histone marks was found increased after alone as well as combined treatment. Histone deacetylase (HDAC)1, HDAC3, and HDAC8 were downregulated by resveratrol alone and combined treatment. Conclusively, combination of resveratrol and quercetin brings cell growth inhibition, DNA damage, and cell cycle arrest in OCCs but not in normal cells. Additionally, combined treatment causes downregulation of HDACs and apoptosis in cancer cells and it could be an incisive strategy against oral cancer.

Resveratrol is an arginase inhibitor contributing to vascular smooth muscle cell vasoconstriction via increasing cytosolic calcium

The contractility of vascular smooth muscle cells (VSMCs) controls the lumen diameter of vessels, thus serving a role in regulating blood pressure and organ blood flow. Although arginases are known to have numerous effects in the biological activities of VSMCs, the effects of arginase II on the constriction of VSMCs has not yet been investigated. When conducting a natural products screen for an inhibitor against arginase, the present study identified that a relatively high concentration of resveratrol (RSV) exhibited arginase inhibitory activity. Therefore, the present study investigated whether RSV could regulate VSMCs contractions and the underlying mechanism. Arginase inhibition by RSV led to an increase in the concentration of the substrate L‑Arg and an accompanying increase in the cytosol Ca2+ concentration [(Ca2+)c] in VSMCs. The increased [Ca2+]c induced by RSV and L‑Arg treatments resulted in CaMKII‑dependent MLC20 phosphorylation. The effects of RSV on VSMCs were maintained even when VSMCs were pre‑treated with sirtinol, an inhibitor of Sirt proteins. In a vascular tension assay with de‑endothelialized aortic vessels, vasoconstrictor responses, which were measured using phenylephrine (PE), were significantly enhanced in the RSV‑ and L‑Arg‑treated vessels. Therefore, although arginase inhibition has exhibited beneficial effects in various diseases, care is required when considering administration of an arginase inhibitor to patients with vessels endothelial dysfunction as RSV can induce vessel contraction.

Resveratrol-induced autophagy is dependent on IP3Rs and on cytosolic Ca2

Previous work revealed that intracellular Ca²⁺ signals and the inositol 1,4,5-trisphosphate (IP₃) receptors (IP₃R) are essential to increase autophagic flux in response to mTOR inhibition, induced by either nutrient starvation or rapamycin treatment. Here, we investigated whether autophagy induced by resveratrol, a polyphenolic phytochemical reported to trigger autophagy in a non-canonical way, also requires IP₃Rs and Ca²⁺ signaling. Resveratrol augmented autophagic flux in a time-dependent manner in HeLa cells. Importantly, autophagy induced by resveratrol (80μM, 2h) was completely abolished in the presence of 10μM BAPTA-AM, an intracellular Ca²⁺-chelating agent. To elucidate the IP₃R's role in this process, we employed the recently established HEK 3KO cells lacking all three IP₃R isoforms. In contrast to the HEK293 wt cells and to HEK 3KO cells re-expressing IP₃R1, autophagic responses in HEK 3KO cells exposed to resveratrol were severely impaired. These altered autophagic responses could not be attributed to alterations in the mTOR/p70S6K pathway, since resveratrol-induced inhibition of S6 phosphorylation was not abrogated by chelating cytosolic Ca²⁺ or by knocking out IP₃Rs. Finally, we investigated whether resveratrol by itself induced Ca²⁺ release. In permeabilized HeLa cells, resveratrol neither affected the sarco- and endoplasmic reticulum Ca²⁺ ATPase (SERCA) activity nor the IP₃-induced Ca²⁺ release nor the basal Ca²⁺ leak from the ER. Also, prolonged (4 h) treatment with 100μM resveratrol did not affect subsequent IP₃-induced Ca²⁺ release. However, in intact HeLa cells, although resveratrol did not elicit cytosolic Ca²⁺ signals by itself, it acutely decreased the ER Ca²⁺-store content irrespective of the presence or absence of IP₃Rs, leading to a dampened agonist-induced Ca²⁺ signaling. In conclusion, these results reveal that IP₃Rs and cytosolic Ca²⁺ signaling are fundamentally important for driving autophagic flux, not only in response to mTOR inhibition but also in response to non-canonical autophagy inducers like resveratrol. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Resveratrol Specifically Kills Cancer Cells by a Devastating Increase in the Ca2+ Coupling Between the Greatly Tethered Endoplasmic Reticulum and Mitochondria

Background/Aims

Resveratrol and its derivate piceatannol are known to induce cancer cell-specific cell death. While multiple mechanisms of actions have been described including the inhibition of ATP synthase, changes in mitochondrial membrane potential and ROS levels, the exact mechanisms of cancer specificity of these polyphenols remain unclear. This paper is designed to reveal the molecular basis of the cancer-specific initiation of cell death by resveratrol and piceatannol.

Methods

The two cancer cell lines EA.hy926 and HeLa, and somatic short-term cultured HUVEC were used. Cell viability and caspase 3/7 activity were tested. Mitochondrial, cytosolic and endoplasmic reticulum Ca²⁺ as well as cytosolic and mitochondrial ATP levels were measured using single cell fluorescence microscopy and respective genetically-encoded sensors. Mitochondria-ER junctions were analyzed applying super-resolution SIM and ImageJ-based image analysis.

Results

Resveratrol and piceatannol selectively trigger death in cancer but not somatic cells. Hence, these polyphenols strongly enhanced mitochondrial Ca²⁺ uptake in cancer exclusively. Resveratrol and piceatannol predominantly affect mitochondrial but not cytosolic ATP content that yields in a reduced SERCA activity. Decreased SERCA activity and the strongly enriched tethering of the ER and mitochondria in cancer cells result in an enhanced MCU/Letm1-dependent mitochondrial Ca²⁺ uptake upon intracellular Ca²⁺ release exclusively in cancer cells. Accordingly, resveratrol/piceatannol-induced cancer cell death could be prevented by siRNA-mediated knock-down of MCU and Letm1.

Conclusions

Because their greatly enriched ER-mitochondria tethering, cancer cells are highly susceptible for resveratrol/piceatannol-induced reduction of SERCA activity to yield mitochondrial Ca²⁺ overload and subsequent cancer cell death.

Natural products induce a G protein-mediated calcium pathway activating p53 in cancer cells

Paclitaxel, etoposide, vincristine and doxorubicin are examples of natural products being used as chemotherapeutics but with adverse side effects that limit their therapeutic window. Natural products derived from plants and having low toxicity, such as quercetin, resveratrol, epigallocatechin gallate and piceatannol, have been shown to inhibit tumor cell growth both in vitro and in pre-clinical models of cancer, but their mechanisms of action have not been fully elucidated, thus restricting their use as prototypes for developing synthetic analogs with improved anti-cancer properties. We and others have demonstrated that one of the earliest and consistent events upon exposure of tumor cells to these less toxic natural products is a rise in cytoplasmic calcium, activating several pro-apoptotic pathways. We describe here a G protein/inositol 1,4,5-trisphosphate pathway (InsP3) in MDA-MB-231 human breast cancer cells that mediates between these less toxic natural products and the release of calcium from the endoplasmic reticulum. Further, we demonstrate that this elevation of intracellular calcium modulates p53 activity and the subsequent transcription of several pro-apoptotic genes encoding PIG8, CD95, PIDD, TP53INP, RRM2B, Noxa, p21 and PUMA. We conclude from our findings that less toxic natural products likely bind to a G protein coupled receptor that activates a G protein-mediated and calcium-dependent pathway resulting selectively in tumor cell death.

Migration and invasion of oral squamous carcinoma cells is promoted by WNT5A, a regulator of cancer progression

BACKGROUND

Oral squamous cell carcinoma (OSCC) constitutes 90% of all cancers in the oral cavity, and the prognosis for patients diagnosed with OSCC is still poor. The identification of novel therapeutic targets and prognostic markers for OSCC is therefore essential. Previous studies of OSCC revealed an increased expression of WNT5A in the tumor tissue. However, no functional studies of WNT5A-induced effects in OSCC have been performed.

METHODS

Two different OSCC cell lines were used for analysis of WNT5A expression by Western blot, whereas WNT5A-induced responses were analyzed by measuring calcium (Ca²⁺) signaling, PKC activation, migration and invasion.

RESULTS

Despite the lack of WNT5A expression, both cell lines responded to recombinant WNT5A (rWNT5A) with activation of the non-canonical WNT/Ca²⁺ /PKC pathway. This effect was ascertained to be mediated by WNT5A by use of the WNT5A antagonist, Box5. To investigate how WNT5A affects tumor progression, rWNT5A-induced alterations in BrdU absorbance (reflecting the number of tumor cells) were analyzed. rWNT5A had no effect on BrdU absorbance but instead promoted tumor cell migration and invasion. These results were confirmed by the use of the WNT5A-mimicking peptide Foxy5, while the rWNT5A-induced migration was blocked by secreted Frizzled-related protein 1 (SFRP1), protein kinase C inhibitors or the intracellular Ca²⁺ chelator, MAPT.

CONCLUSIONS

These novel data clearly show that WNT5A activates the non-canonical WNT/Ca²⁺ /PKC pathway and increases migration and invasion of OSCC cells. This may indicate how an increased WNT5A expression in the tumor tissue is likely to promote progression of OSCC.