3,3'-Diindolylmethane alters Ca2+ homeostasis and viability in MG63 human osteosarcoma cells

3,3'-Diindolylmethane induces gastric cancer cells death via STIM1 mediated store-operated calcium entry

3,3'-Diindolylmethane (DIM), a natural phytochemicals isolated from cruciferous vegetables, has been reported to inhibit human gastric cancer cells proliferation and induce cells apoptosis as well as autophagy, but its mechanisms are still unclear. Store-operated calcium entry (SOCE) is a main Ca2+ influx pathway in various of cancers, which is activated by the depletion of endoplasmic reticulum (ER) Ca2+ store. Stromal interaction molecular 1 (STIM1) is the necessary component of SOCE. In this study, we focus on to examine the regulatory mechanism of SOCE on DIM-induced death in gastric cancer. After treating the human BGC-823 and SGC-7901 gastric cancer cells with DIM, cellular proliferation was determined by MTT, apoptosis and autophagy were detected by flow cytometry or Hoechst 33342 staining. The expression levels of related proteins were evaluated by Western blotting. Free cytosolilc Ca2+ level was assessed by fluorescence monitoring under a laser scanning confocal microscope. The data have shown that DIM could significantly inhibit proliferation and induce apoptosis as well as autophagy in two gastric cancer cell lines. After DIM treatment, the STIM1-mediated SOCE was activated by upregulating STIM1 and decreasing ER Ca2+ level. Knockdown STIM1 with siRNA or pharmacological inhibition of SOCE attenuated DIM induced apoptosis and autophagy by inhibiting p-AMPK mediated ER stress pathway. Our data highlighted that the potential of SOCE as a promising target for treating cancers. Developing effective and selective activators targeting STIM1-mediated SOCE pathway will facilitate better therapeutic sensitivity of phytochemicals acting on SOCE in gastric cancer. Moreover, more research should be performed to validate the efficacy of combination chemotherapy of anti-cancer drugs targeting SOCE for clinical application.

Action of the insecticide cyfluthrin on Ca2+ signal transduction and cytotoxicity in human osteosarcoma cells

Cyfluthrin is a pyrethroid insecticide and common household pesticide. The effect of cyfluthrin on Ca²⁺-related physiology in human osteosarcoma is unclear. This study investigated the effect of cyfluthrin on cytosolic-free Ca²⁺ concentrations ([Ca²⁺]_i) and viability in MG63 human osteosarcoma cells. Cyfluthrin concentration-dependently induced [Ca²⁺]_i rises. Cyfluthrin-induced Ca²⁺ entry was confirmed by the Mn²⁺-induced quench of fura-2 fluorescence. Cyfluthrin at concentrations of 10-100 μM induced [Ca²⁺]_i rises. Ca²⁺ removal reduced the signal by approximately 50%. Cyfluthrin (100 μM) induced Mn²⁺ influx suggesting Ca²⁺ entry. Cyfluthrin-induced Ca²⁺ entry was inhibited 50% by protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate) and inhibitor (GF109203X) and also by three inhibitors of store-operated Ca²⁺ channels: nifedipine, econazole, and SKF96365. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin (TG) completely inhibited cyfluthrin-evoked [Ca²⁺]_i rises. Conversely, treatment with cyfluthrin abolished TG-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with 1-[6-[((17β)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dion abolished cyfluthrin-induced [Ca²⁺]_i rises. Cyfluthrin at 25-65 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester. Together, in MG63 cells, cyfluthrin induced [Ca²⁺]_i rises by evoking PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. Cyfluthrin also caused Ca²⁺-independent cell death.

Small Molecules as Drugs to Upregulate Metastasis Suppressors in Cancer Cells

It is well-recognized that the majority of cancer-related deaths is attributed to metastasis, which can arise from virtually any type of tumor. Metastasis is a complex multistep process wherein cancer cells must break away from the primary tumor, intravasate into the circulatory or lymphatic systems, extravasate, proliferate and eventually colonize secondary sites. Since these molecular processes involve the coordinated actions of numerous proteins, targeted disruptions of key players along these pathways represent possible therapeutic interventions to impede metastasis formation and reduce cancer mortality. A diverse group of proteins with demonstrated ability to inhibit metastatic colonization have been identified and they are collectively known as metastasis suppressors. Given that the metastasis suppressors are often downregulated in tumors, drug-induced re-expression or upregulation of these proteins represents a promising approach to limit metastasis. Indeed, over 40 compounds are known to exhibit efficacy in upregulating the expression of metastasis suppressors via transcriptional or post-transcriptional mechanisms, and the most promising ones are being evaluated for their translational potentials. These small molecules range from natural products to drugs in clinical use and they apparently target different molecular pathways, reflecting the diverse nature of the metastasis suppressors. In this review, we provide an overview of the different classes of compounds known to possess the ability to upregulate one or more metastasis suppressors, with an emphasis on their mechanisms of action and therapeutic potentials.

Amitriptyline modulated Ca2+ signaling and induced Ca2+-independent cell viability in human osteosarcoma cells

Amitriptyline is a widely used tricyclic antidepressant, which acts primarily as a serotonin–norepinephrine reuptake inhibitor. This study examined the effect of amitriptyline on Ca2+ homeostasis and its related mechanism in MG63 human osteosarcoma cells. Amitriptyline evoked cytosolic-free Ca2+ concentrations ([Ca2+]i) rises concentration dependently. Amitriptyline-evoked Ca2+ entry was confirmed by Mn2+-induced quench of fura-2 fluorescence. This entry was inhibited by Ca2+ entry modulators nifedipine, econazole, SKF96365, the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate but was not affected by the PKC inhibitor GF109203X. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) inhibited amitriptyline-evoked [Ca2+]i rises by 95%. Conversely, treatment with amitriptyline abolished TG-evoked [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 inhibited amitriptyline-evoked [Ca2+]i rises by 70%. Amitriptyline killed cells at 200–500 μM in a concentration-dependent fashion. Chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid/AM did not reverse amitriptyline-induced cytotoxicity. Collectively, our data suggest that in MG63 cells, amitriptyline induced [Ca2+]i rises by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via PKC-regulated store-operated Ca2+ entry. Amitriptyline also induced Ca2+-disassociated cell death.

Effect of diindolylmethane on Ca2+ homeostasis and viability in MDCK renal tubular cells

The effect of the natural product diindolylmethane (DIM) on cytosolic Ca2+ concentrations ([Ca2+]i) and viability in MDCK renal tubular cells was explored. The Ca2+-sensitive fluorescent dye fura-2 was applied to measure [Ca2+]i. DIM at concentrations 1–50 μM induced a [Ca2+]i rise in a concentration-dependent manner. The response was reduced partly by removing Ca2+. DIM induced Mn2+ influx leading to quenching of fura-2 fluorescence. DIM-evoked Ca2+ entry was suppressed by nifedipine, econazole, SK&F96365 and protein kinase C modulators. In the absence of extracellular Ca2+, incubation with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) or 2,5-di-tert-butylhydroquinone (BHQ) greatly inhibited DIM-induced [Ca2+]i rise. Incubation with DIM abolished TG or BHQ-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 reduced DIM-induced [Ca2+]i rise by 50%. At 1, 10, 40 and 50 μM, DIM slightly enhanced cell proliferation. The effect of 50 μM DIM was reversed by chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N', N'-tetraacetic acid. In sum, in MDCK cells, DIM induced a [Ca2+]i rise by evoking phospholipase C-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via protein kinase C-sensitive store-operated Ca2+ channels. DIM did not induce cell death.