Anti-cancer effects of JKA97 are associated with its induction of cell apoptosis via a Bax-dependent and p53-independent pathway

p53, one of the most commonly mutated genes in human cancers, is thought to be associated with cancer development. Hence, screening and identifying natural or synthetic compounds with anti-cancer activity via p53-independent pathway is one of the most challenging tasks for scientists in this field. Compound JKA97 (methoxy-1-styryl-9H-pyrid-[3,4-b]-indole) is a small molecule synthetic anti-cancer agent, with unknown mechanism(s). In this study we have demonstrated that the anti-cancer activity of JKA97 is associated with apoptotic induction via p53-independent mechanisms. We found that co-incubation of human colon cancer HCT116 cells with JKA97 inhibited HCT116 cell anchorage-independent growth in vitro and tumorigenicity in nude mice and also induced a cell apoptotic response, both in the cell culture model and in a tumorigenesis nude mouse model. Further studies showed that JKA97-induced apoptosis was dramatically impaired in Bax knock-out (Bax(-/-)) HCT116 cells, whereas the knock-out of p53 or PUMA did not show any inhibitory effects. The p53-independent apoptotic induction by JKA97 was confirmed in other colon cancer and hepatocarcinoma cell lines. In addition, our results showed an induction of Bax translocation and cytochrome c release from the mitochondria to the cytosol in HCT116 cells, demonstrating that the compound induces apoptosis through a Bax-initiated mitochondria-dependent pathway. These studies provide a molecular basis for the therapeutic application of JKA97 against human cancers with p53 mutations.     

BAI,A novel cyclin‐dependent kinase inhibitor induces apoptosis in A549 cells through activation of caspases and inactivation of Akt

Previously, we have synthesized a novel cyclin‐dependent kinase (CDK) inhibitor, 2‐[1,1′biphenyl]‐4‐yl‐N‐[5‐(1,1‐dioxo‐1λ⁶‐isothiazolidin‐2‐yl)‐1H‐indazol‐3‐yl]acetamide (BAI) and reported its anti‐cancer activity in head and neck cancer cells. In this study, we further evaluated the effect of BAI on growth of various human cancer cell lines, including A549 (nonsmall cell lung cancer), HCT116 (colon), and Caki (kidney). Profoundly, results of XTT and clonogenic assays demonstrated that BAI at nanomolar concentrations (20–60 nM) inhibited growth of A549, HCT116, and Caki cells, suggesting the anti‐cancer potency. We show that BAI induced a dose‐dependent apoptotic cell death in these human cancer cells, as measured by fluorescence‐activated cell sorting (FACS). Interestingly, further biochemical analysis showed that treatment with BAI at 20 nM induced apoptosis in A549 cells in association with activation of caspases, cleavage of phospholipase C‐γ1 (PLC‐γ1), and inhibition of Akt in A549 cells. Importantly, pharmacological inhibition study revealed that pretreatment with z‐VAD‐fmk, a pan caspase inhibitor strongly blocked the BAI‐induced apoptosis in A549 cells. Transfection analysis with Akt cDNA encoding constitutively active Akt further addressed the significance of Akt inhibition in the BAI‐induced apoptosis in A549 cells. Notably, disruption of the PI3K/Akt pathway by LY294002, a PI3K/Akt inhibitor potentiated apoptosis in A549 cells by BAI at a subcytotoxic concentration. These findings collectively suggest that BAI potently inhibits growth of A549, HCT116, and Caki cells, and that the BAI‐induced apoptosis in A549 cells is associated with activation of caspases, and inhibition of Akt. J. Cell. Biochem. 114: 282–293, 2013. © 2012 Wiley Periodicals, Inc.     

Dual role of CO2/HCO3(-) buffer in the regulation of intracellular pH of three-dimensional tumor growths

Intracellular pH (pH(i)), a major modulator of cell function, is regulated by acid/base transport across membranes. Excess intracellular H(+) ions (e.g. produced by respiration) are extruded by transporters such as Na(+)/H(+) exchange, or neutralized by HCO(3)(-) taken up by carriers such as Na(+)-HCO(3)(-) cotransport. Using fluorescence pH(i) imaging, we show that cancer-derived cell lines (colorectal HCT116 and HT29, breast MDA-MB-468, pancreatic MiaPaca2, and cervical HeLa) extrude acid by H(+) efflux and HCO(3)(-) influx, largely sensitive to dimethylamiloride and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS), respectively. The magnitude of HCO(3)(-) influx was comparable among the cell lines and may represent a constitutive element of tumor pH(i) regulation. In contrast, H(+) efflux varied considerably (MDA-MB-468 > HCT116 > HT29 > MiaPaca2 > HeLa). When HCO(3)(-) flux was pharmacologically inhibited, acid extrusion in multicellular HT29 and HCT116 spheroids (～10,000 cells) was highly non-uniform and produced low pH(i) at the core. With depth, acid extrusion became relatively more DIDS-sensitive because the low extracellular pH at the spheroid core inhibits H(+) flux more than HCO(3)(-) flux. HCO(3)(-) flux inhibition also decelerated HCT116 spheroid growth. In the absence of CO(2)/HCO(3)(-), acid extrusion by H(+) flux in HCT116 and MDA-MB-468 spheroids became highly non-uniform and inadequate at the core. This is because H(+) transporters require extracellular mobile pH buffers, such as CO(2)/HCO(3)(-), to overcome low H(+) ion mobility and chaperone H(+) ions away from cells. CO(2)/HCO(3)(-) exerts a dual effect: as substrate for membrane-bound HCO(3)(-) transporters and as a mobile buffer for facilitating extracellular diffusion of H(+) ions extruded from cells. These processes can be augmented by carbonic anhydrase activity. We conclude that CO(2)/HCO(3)(-) is important for maintaining uniformly alkaline pH(i) in small, non-vascularized tumor growths and may be important for cancer disease progression.     

Synthesis, biological evaluation and molecular docking studies of 3-(1,3-diphenyl-1H-pyrazol-4-yl)-N-phenylacrylamide derivatives as inhibitors of HDAC activity

In present study, a series of 3-(1,3-diphenyl-1H-pyrazol-4-yl)-N-phenylacrylamide derivatives (5a-8d) were designed, synthesized, and evaluated for HDAC inhibition and tumor cell antiproliferation. All of these compounds are reported for the first time, the chemical structures of these compounds were confirmed by means of (1)H NMR, ESI-MS and elemental analyzes. Among the compounds, compound 8c showed the most potent biological activity against HCT116 cancer cell line (IC(50) of 0.42 ± 0.02 μM for HDAC-1 and IC(50)=0.62 ± 0.02 for HCT116). Docking simulation was performed to position compound 8c into the HDAC active site to determine the probable binding model. The results of antiproliferative assay and western-blot demonstrated that compound 8c with potent inhibitory activity in tumor growth inhibition may be a potential anticancer agent against HCT116 cancer cell.     

Intra-Tumoral Heterogeneity in Metastatic Potential and Survival Signaling between Iso-Clonal HCT116 and HCT116b Human Colon Carcinoma Cell Lines

Background

Colorectal cancer (CRC) metastasis is a leading cause of cancer-related deaths in the United States. The molecular mechanisms underlying this complex, multi-step pathway are yet to be completely elucidated. Recent reports have stressed the importance of intra-tumoral heterogeneity in the development of a metastatic phenotype. The purpose of this study was to characterize the intra-tumoral phenotypic heterogeneity between two iso-clonal human colon cancer sublines HCT116 and HCT116b on their ability to undergo metastatic colonization and survive under growth factor deprivation stress (GFDS).

Materials and Methods

HCT116 and HCT116b cells were transfected with green fluorescence protein and subcutaneously injected into BALB/c nude male mice. Once xenografts were established, they were excised and orthotopically implanted into other male BALB/c nude mice using microsurgical techniques. Animal tissues were studied for metastases using histochemical techniques. Microarray analysis was performed to generate gene signatures associated with each subline. In vitro assessment of growth factor signaling pathway was performed under GFDS for 3 and 5 days.

Results

Both HCT116 and HCT116b iso-clonal variants demonstrated 100% primary tumor growth, invasion and peritoneal spread. However, HCT116 was highly metastatic with 68% metastasis observed in liver and/or lungs compared to 4% in HCT116b. Microarray analysis revealed an upregulation of survival and metastatic genes in HCT116 cells compared to HCT116b cells. In vitro analysis showed that HCT116 upregulated survival and migratory signaling proteins and downregulated apoptotic agents under GFDS. However, HCT116b cells effectively showed the opposite response under stress inducing cell death.

Conclusions

We demonstrate the importance of clonal variation in determining metastatic potential of colorectal cancer cells using the HCT116/HCT116b iso-clonal variants in an orthotopic metastatic mouse model. Determination of clonal heterogeneity in patient tumors can serve as useful tools to identify clinically relevant biomarkers for diagnostic and therapeutic assessment of metastatic colorectal cancer.     

Growth inhibition due to complementation of transforming growth factor-beta receptor type II-defect by human chromosome 3 transfer in human colorectal carcinoma cells

The transforming growth-beta receptor type II (TGF-beta RII) gene is one of the target genes of the DNA mismatch repair (MMR) defect. The human colorectal carcinoma cell line HCT116 has mutations in the hMLH1 gene and in the microsatellite region of the TGF-beta RII gene, both located on the short arm of chromosome 3. Introduction of the wild-type hMLH1 gene on transferred human chromosome 3 restores many characteristics of MMR-deficiency in HCT116. In this study, we determined whether transfer of chromosome 3 into HCT116 also complements the TGF-beta RII gene defect. We compared in vitro growth characteristics between HCT116 and HCT116 with a transferred chromosome 3 (HCT116 + ch3). The growth was suppressed in HCT116 + ch3 compared with parental HCT116. This suppression was abolished by frequent replacement with fresh medium, suggesting that the autocrine TGF-beta-TGF-beta RII system may be responsible for growth suppression. To explore this possibility, we determined several characteristics essential for the autocrine system. We found that HCT116 + ch3 expresses wild-type as well as mutated TGF-beta RII mRNA. In addition, phosphorylation of TGF-beta RI and growth inhibition were observed in HCT116 + ch3 but not in HCT116 by exposure to exogenous TGF-beta. The amount of TGF-beta1 in HCT116 + ch3 cultures was remarkably less than that in the HCT116, suggesting that TGF-beta produced by HCT116 + ch3 cells may be consumed by the cells. The conditioned medium from HCT116 cultures inhibits HCT116 + ch3 growth. This inhibition was neutralized by the anti-TGF-beta antibody. Taken together, these results strongly suggest that the TGF-beta RII gene defect in HCT116 is complemented by a wild-type gene on the transferred chromosome 3 and that HCT116 + ch3 gained the ability to respond to TGF-beta. Simultaneous complementation of defects of a responsible gene and a major target gene by the chromosome transfer is useful to prove the inactivated phenotypes acquired during colorectal tumorigenesis.     

Synthesis and Cytotoxicity Evaluation of Panaxadiol Derivatives

In this study, 13 panaxadiol (PD) derivatives were synthesized via reactions with aromatic compounds and amino acids. Following this, the cytotoxicity of these compounds was evaluated against four cancer cell lines (human hepatoma cells HepG‐2, human lung cancer cells A549, human breast cancer cells MCF‐7, and human colon cancer cells HCT‐116) and one normal cell lines (human gastric epithelial cells GES‐1). The results showed that the panaxadiol derivatives 3 , 12 , and 13 showed significant inhibition of cellular proliferation against cancer cells compared with PD, and the panaxadiol derivative 12 had the lowest IC₅₀ value for A549 (IC₅₀=18.91±1.03 μm ). For MCF‐7 cells, most compounds exhibited good inhibition of cellular proliferation, and the panaxadiol derivative 13 showed the strongest inhibitory effect (IC₅₀=8.62±0.23 μm ), which significantly increased the cytotoxicity of PD and was stronger than the positive control (mitomycin). For normal cells, all compounds exhibited low or no toxic effects; thus, these derivatives can be used to develop novel antiproliferative agents.     

All-trans retinoic acid activates E-cadherin expression via promoter hypomethylation in the human colon carcinoma HCT116 cells

All-trans retinoic acid (ATRA) inhibits the invasive and metastatic potentials of various cancer cells; however, the underlying mechanism is unclear. Here, we show that ATRA activated E-cadherin expression via promoter hypomethylation to facilitate Sp1 binding on its recognition sites in human colon carcinoma HCT116 cells. This effect was mediated by retinoic acid receptor-β2, as demonstrated by knock-down experiments using a specific siRNA. As a result, ATRA increased cell-to-cell interactions, reduced cell migration, and downregulated levels of Vimentin and Fibronectin in HCT116 cells. The present study thus provides the mechanism for the beneficial effects of ATRA in the treatment of metastatic human carcinomas.     

Honokiol radiosensitizes colorectal cancer cells: enhanced activity in cells with mismatch repair defects

DNA mismatch repair is required for correcting any mismatches that are created during replication and recombination, and a defective mismatch repair system contributes to DNA damage-induced growth arrest. The colorectal cancer cell line HCT116 is known to have a mutation in the hMLH1 mismatch repair gene resulting in microsatellite instability and defective mismatch repair. Honokiol is a biphenolic compound that has been used in traditional Chinese medicine for treating various ailments including cancer. This study was designed to test the hypothesis that honokiol enhances the radiosensitivity of cancer cells with mismatch repair defect (HCT116) compared with those that are mismatch repair proficient (HCT116-CH3). We first determined that the combination of honokiol and γ-irradiation treatment resulted in dose-dependent inhibition of proliferation and colony formation in both cell lines. However, the effects were more pronounced in HCT116 cells. Similarly, the combination induced higher levels of apoptosis (caspase 3 activation, Bax to Bcl2 ratio) in the HCT116 cells compared with HCT116-CH3 cells. Cell cycle analyses revealed higher levels of dead cells in HCT116 cells. The combination treatment reduced expression of cyclin A1 and D1 and increased phosphorylated p53 in both cell lines, although there were significantly lower amounts of phosphorylated p53 in the HCT116-CH3 cells, suggesting that high levels of hMLH1 reduce radiosensitivity. These data demonstrate that honokiol is highly effective in radiosensitizing colorectal cancer cells, especially those with a mismatch repair defect.     

New microtubule polymerization inhibitors comprising a nitrooxymethylphenyl group

We have designed cancer antiproliferative compounds, starting from aniline or phenol derivative, which comprise one or two nitrooxymethylphenyl groups as do the hybrid drugs NCX4040 and NCX530. Compound 2a with p-nitrooxymethylbenzoyl-oxy and -amino groups as well as 8a with a p-nitrooxymethylbenzoylamino group showed more promising effects than NCX4040 against human colon and breast cancer cells. Since 2a and 8a, but not NCX4040, arrested human colon carcinoma HCT116 cells in the M phase, the former two compounds may inhibit cell growth differently from NCX4040. Merged images of immunofluorescence-stained α-tubulin and Hoechst-stained nuclei in human fibrosarcoma HT1080 cells showed that 2a and 8a disrupted microtubule formation just as did vincristine, the tubulin polymerization inhibitor. In experiments in vivo, the intraperitoneal administration of 8a at 80 mg/kg/day reduced the growth of HCT116 xenografts in nude mice to T/C 55%.     

Snake venom toxin from Vipera lebetina turanica sensitizes cancer cells to TRAIL through ROS- and JNK-mediated upregulation of death receptors and downregulation of survival proteins

We investigated whether snake venom toxin (SVT) from Vipera lebetina turanica enhances the apoptosis ability of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in cancer cells. TRAIL inhibited HCT116 cell growth in a dose-dependent manner; however, this reduction did not occur in TRAIL resistant HT-29, A549 and HepG2 cells with an even higher dose of TRAIL. SVT, but not TRAIL enhanced expression of cell death receptor (DR) in TRAIL resistant cancer cells in a dose-dependent manner. A combination of SVT with TRAIL significantly inhibited cell growth of TRAIL resistant HT-29, A549 and HepG2 cells. Consistent with cell growth inhibition, the expression of TRAIL receptors; DR4 and DR5 was significantly increased as well as apoptosis related proteins such as cleaved caspase-3, -8, -9 and Bax. However, the expression of survival proteins (e.g., cFLIP, survivin, XIAP and Bcl2) was suppressed by the combination treatment of SVT and TRAIL. Depletion of DR4 or DR5 by small interfering RNA significantly reversed the cell growth inhibitory and apoptosis blocking effects of SVT in HCT116 and HT-29 cells. Pretreatment with the c-Jun N-terminal kinase (JNK) inhibitor SP600125 and the reactive oxygen species (ROS) scavenger N-acetylcysteine reduced the SVT and TRAIL-induced upregulation of DR4 and DR5 expression, expression of the apoptosis related protein such as caspase-3 and-9, as well as cell growth inhibitory effects. The collective results suggest that SVT facilitates TRAIL-induced apoptosis in cancer cells through up-regulation of the TRAIL receptors; DR4 and DR5 via ROS/JNK pathway signals.     

Autocrine and exogenous transforming growth factor beta control cell cycle inhibition through pathways with different sensitivity

Human colon carcinoma cells HCT116 that lack transforming growth factor beta (TGF-beta) type II receptor (RII) demonstrated restoration of autocrine TGF-beta activity upon reexpression of RII without restoring inhibitory responses to exogenous TGF-beta treatment. RII transfectants (designated RII Cl 37) had a longer lag phase relative to NEO-transfected control cells (designated NEO pool) before entering exponential growth in tissue culture. The prolonged growth arrest of RII Cl 37 cells was associated with markedly reduced cyclin-dependent kinase (CDK)2 activity. Our results demonstrate that p21 induction by autocrine TGF-beta is responsible for reduced CDK2 activity, which at least partially contributes to prolonged growth arrest and reduced cell proliferation in RII Cl 37 cells. In contrast to RII transfectants, HCT116 cells transfected with chromosome 3 (designated HCT116Ch3), which bears the RII gene, restored the response to exogenous TGF-beta as well as autocrine TGF-beta activity. Autocrine TGF-beta activity in HCT116Ch3 cells induced p21 expression as seen in RII Cl 37 cells; however, in addition to autocrine activity, HCT116Ch3 cells responded to exogenous TGF-beta as decreased CDK4 expression and reduced pRb phosphorylation mediated a TGF-beta inhibitory response in these cells. These results indicate that autocrine TGF-beta regulates the cell cycle through a pathway different from exogenous TGF-beta in the sense that p21 is a more sensitive effector of the TGF-beta signaling pathway, which can be induced and saturated by autocrine TGF-beta, whereas CDK4 inhibition is a less sensitive effector, which can only be activated by high levels of exogenous TGF-beta     

A proteomics approach to identifying novel protein targets involved in erinacine A–mediated inhibition of colorectal cancer cells’ aggressiveness

Erinacine A, a major active component of a diterpenoid derivative isolated from Hericium erinaceus mycelium, has been demonstrated to exert anticancer effects. Herein, we present an investigation of the molecular mechanism of erinacine A induction associated with cancer cells’ aggressive status and death. A proteomic approach was used to purify and identify the differentially expressed proteins following erinacine A treatment and the mechanism of its action in apoptotic and the targets of erinacine A. Our results demonstrate that erinacine A treatment of HCT‐116 and DLD‐1 cells increased cell cytotoxicity and reactive oxygen species (ROS) production as well as decreased cell proliferation and invasiveness. Ten differentially displayed proteins were determined and validated in vitro and in vivo between the erinacine A‐treated and untreated groups. In addition, erinacine A time‐dependent induction of cell death and inhibitory invasiveness was associated with sustained phosphorylation of the PI3K/mTOR/p70S6K and ROCK1/LIMK2/Cofilin pathways. Furthermore, we demonstrated that erinacine A–induced HCT‐116 and DLD‐1 cells viability and anti‐invasion properties by up‐regulating the activation of PI3K/mTOR/p70S6K and production of ROS. Experiments involving specific inhibitors demonstrated that the differential expression of cofilin‐1 (COFL1) and profilin‐1 (PROF1) during erinacine A treatment could be involved in the mechanisms of HCT‐116 and DLD‐1 cells death and decreased aggressiveness, which occurred via ROCK1/LIMK2/Cofilin expression, with activation of the PI3K/mTOR/p70S6K signalling pathway. These findings elucidate the mechanism of erinacine A inhibiting the aggressive status of cells by activating PI3K/mTOR/p70S6K downstream signalling and the novel protein targets COF1 and PROF1; this could be a good molecular strategy to limit the aggressiveness of CRC cells.     

Characterization of dihydroartemisinin-resistant colon carcinoma HCT116/R cell line

Dihydroartemisinin (DHA) is an important artemisinin derivative and presents profound anti-tumor potential. A DHA-resistant cell line named HCT116/R derived from colon carcinoma cell line HCT116 was established in our previous study. Herein, we found that HCT116/R cells were much more resistant to DHA- or artesunate-induced proliferation inhibition and more tolerant to DHA-induced cell cycle arrest and apoptosis compared with those of the parent HCT116 cells. The protein levels of P-glycoprotein and MDR-associated protein 1 and the accumulation of doxorubicin in cells were similar in both cell lines. Moreover, HCT116/R cells were still sensitive to camptothecin- and doxorubicin-induced cell growth inhibition. To further explore the characterization of HCT116/R cell line, a proteomic study employing two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was performed. Eight different expressed proteins between the two cell lines were identified including some heat shock proteins, annexins, etc. This study not only indicates that exposure to DHA may not induce a tumor multi-drug-resistant phenotype but also affords new clues for the further investigation of the anti-cancer mechanisms of DHA and other artemisinin derivatives.     

Neutralizing FGF4 protein in conditioned medium of IL-21-silenced HCT116 cells restores the migratory activity of the colorectal cancer cells

The interleukin-21 (IL-21) protein was found to be expressed at an elevated level in clinical samples of colorectal cancer patients without or with a parasitic infection that were collected from Sudan in our previous study. The IL-21 gene in HT29 and HCT116 cells was then correlated to cell proliferation and cell migration, as well as the cellular mechanisms associated with gene expressions in our present study. Our results demonstrated that silencing the IL-21 gene in HCT116 cells increased the cytotoxic level and fibroblast growth factor-4 (FGF4) mRNA expression in the cancer cells. Moreover, specific gene silencing reduced the migration of cancer cells compared to non-silenced cancer cells. These events were not observed in IL-21-silenced HT29 cells. Neutralizing FGF4 in conditioned medium of IL-21-silenced HCT116 cells further increased the cytotoxic level and restored the migratory activity of HCT116 cells in the culture compared to silencing the IL-21 gene alone in the cancer cells. Our results indicate the importance of both silencing the IL-21 gene and co-expression of the FGF4 protein in HCT116 cells, which pave the way for the discovery of important factors to be used as biomarkers for the design of drugs or cost-effective supplements to effectively treat the patients having infectious disease and HCT116 cells of colorectal cancer simultaneously in the future.     

Resveratrol inhibits Erk1/2-mediated adhesion of cancer cells via activating PP2A–PTEN signaling network

Resveratrol, a natural polyphenol compound, has been shown to possess anticancer activity. However, how resveratrol inhibits cancer cell adhesion has not been fully elucidated. Here, we show that resveratrol suppressed the basal or type I insulin-like growth factor (IGF)-1-stimulated adhesion of cancer cells (Rh1, Rh30, HT29, and HeLa cells) by inhibiting the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway. Inhibition of Erk1/2 with U0126, knockdown of Erk1/2, or overexpression of dominant-negative mitogen-activated protein kinase kinase 1 (MKK1) strengthened resveratrol’s inhibition of the basal or IGF-1-stimulated of Erk1/2 phosphorylation and cell adhesion, whereas ectopic expression of constitutively active MKK1 attenuated the inhibitory effects of resveratrol. Further research revealed that both protein phosphatase 2A (PP2A) and phosphatase and tensin homolog (PTEN)–Akt were implicated in resveratrol-inactivated Erk1/2-dependent cell adhesion. Inhibition of PP2A with okadaic acid or overexpression of dominant-negative PP2A rendered resistance to resveratrol’s suppression of the basal or IGF-1-stimulated phospho-Erk1/2 and cell adhesion, whereas expression of wild-type PP2A enhanced resveratrol’s inhibitory effects. Overexpression of wild-type PTEN or dominant-negative Akt or inhibition of Akt with Akt inhibitor X strengthened resveratrol’s inhibition of the basal or IGF-1-stimulated Erk1/2 phosphorylation and cell adhesion. Furthermore, inhibition of mechanistic/mammalian target of rapamycin (mTOR) with rapamycin or silencing mTOR enhanced resveratrol’s inhibitory effects on the basal and IGF-1-induced inhibition of PP2A–PTEN, activation of Akt–Erk1/2, and cell adhesion. The results indicate that resveratrol inhibits Erk1/2-mediated adhesion of cancer cells via activating PP2A–PTEN signaling network. Our data highlight that resveratrol has a great potential in the prevention of cancer cell adhesion.     

Apoptin induces pyroptosis of colorectal cancer cells via the GSDME-dependent pathway

Apoptin is a small molecular weight protein encoded by the VP3 gene of chicken anemia virus (CAV). It can induce apoptosis of tumor cells and play anti-tumorigenic functions. In this study, we identified a time-dependent inhibitory role of apoptin on the viability of HCT116 cells. We also demonstrated that apoptin induces pyroptosis through cleaved caspase 3, and with a concomitant cleavage of gasdermin E (GSDME) rather than GSDMD. GSDME knockdown switched the apoptin-induced cell death from pyroptosis to apoptosis in vitro. Furthermore, we demonstrated that the effect of apoptin on GSDME-dependent pyroptosis could be mitigated by caspase-3 and caspase-9 siRNA knockdown. Additionally, apoptin enhanced the intracellular reactive oxygen species (ROS), causing aggregation of the mitochondrial membrane protein Tom20. Moreover, bax and cytochrome c were released to the activating caspase-9, eventually triggering pyroptosis. Therefore, GSDME mediates the apoptin-induced pyroptosis through the mitochondrial apoptotic pathway. Finally, using nude mice xenografted with HCT116 cells, we found that apoptin induces pyroptosis and significantly inhibits tumor growth. Based on this mechanism, apoptin may provide a new strategy for colorectal cancer therapy.