Generation of ROS by CAY10598 leads to inactivation of STAT3 signaling and induction of apoptosis in human colon cancer HCT116 cells

Carnosic acid (CA), the main antioxidant compound of Rosmarinus officinalis L., has been reported to possess anticancer activity. However, the molecular mechanisms underlying the anticancer effects of CA remain poorly understood. Our study revealed that CA treatment significantly reduced the viability of human colon cancer HCT116, SW480, and HT-29 cells. Treatment with CA induced apoptosis, which was associated with the induction of p53 and Bax, inhibition of Mdm2, Bcl-2, and Bcl-xl expression, activation of caspase-9, and -3, and the cleavage of PARP in HCT116 cells. CA inhibited the constitutive phosphorylation, the DNA binding and the reporter gene activity of STAT3 in HCT116 cells by blocking the phosphorylation of upstream JAK2 and Src kinases. Moreover, CA attenuated the expression of STAT3 target gene products, such as survivin, cyclin D1, D2, and D3. In STAT3-overexpressed HCT116 cells, CA inhibited cell viability and the expression of cyclin D1 and survivin. Furthermore, CA treatment induced the generation of ROS in these colon cancer cells. Pretreatment of cells with ROS scavenger N-acetyl cysteine abrogated the inhibitory effect of CA on the JAK2-STAT3/Src-STAT3 signaling and rescued cells from CA-induced apoptosis by blocking the induction of p53 and the cleavage of caspase-3 and PARP in HCT116 cells. However, L-buthionine-sulfoximine, a pharmacological inhibitor of GSH synthesis, increased CA-induced ROS production, thereby potentiating apoptotic effect of CA. In conclusion, our study provides the first report that CA induced apoptosis in HCT116 cells via generation of ROS, induction of p53, activation of caspases, and inhibition of STAT3 signaling pathway. © 2015 Wiley Periodicals, Inc.

Carnosic acid (CA), the main antioxidant compound of Rosmarinus officinalis L., has been shown to display anticancer activity. However, the molecular mechanisms underlying the anticancer effects of CA remain poorly understood. This study revealed that treatment with CA significantly reduced the cell viability and induced apoptosis in HCT116 cells as evidenced by the induction of p53 and Bax, release of cytochrome c, cleavage of caspase-9, -7 and -3 and PARP and the inhibition of Bcl-2 and Bcl-xl expression. CA inhibited the constitutive phosphorylation, the DNA binding and the reporter gene activity of signal transducer and activator of transcription-3 (STAT3) in HCT116 cells by blocking the phosphorylation of upstream Janus-activated kinase-2 (JAK2) and Src kinases. Moreover, CA attenuated the expression of STAT3 target gene products, such as survivin, cylcin D1, D2, and D3. Since ROS is a universal entity mediating apoptosis, we examined whether CA induced apoptosis via ROS formation. Treatment with CA generated ROS and pretreatment with ROS scavenger N-acetyl cysteine (NAC) rescued cells from apoptosis by abrogating the inhibitory effect of CA on the activation of JAK2-STAT3 and Src-STAT3 signaling pathways and rescued cells from CA-induced apoptosis by blocking the induction of p53, and the cleavage of caspase-3 and PARP. In conclusion, CA induced apoptosis in HCT116 cells via generation of ROS, induction of p53, activation of caspases and inhibition of STAT3 signaling pathway. Citation Format: In Gyeong Chae, Mi-Hee Yu, Ki-Woong Park, Kyung-Soo Chun. Carnosic acid induces apoptosis through inhibition of STAT3 signaling and production of ROS in human colon cancer HCT116 cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5566. doi:10.1158/1538-7445.AM2015-5566

Fisetin, or 3,3',4',7-tetrahydroxyflavone, is present in fruits and vegetables and has been previously reported to inhibit the proliferation of a variety of cancer cells (Lu X, Jung J, Cho HJ, Lim do Y, Lee HS, Chun HS, Kwon DY, Park JH. J Nutr 135: 2884-2890, 2005). We have demonstrated in a previous work that 20-60 micromol/l fisetin inhibits cyclin-dependent kinase activities resulting in cell cycle arrest in HT-29 colon cancer cells. In the present study, we attempted to characterize the mechanisms by which fisetin induces apoptosis in HCT-116 cells. DNA condensations, cleavage of poly(ADP-ribose) polymerase (PARP), and cleavage of caspases 9, 7, and 3 were induced in HCT-116 cells treated with 5-20 micromol/l of fisetin. Fisetin induced a reduction in the protein levels of antiapoptotic Bcl-xL and Bcl-2 and an increase in the levels of proapoptotic Bak and Bim. Fisetin did not affect the Bax protein levels, but induced the mitochondrial translocation of this protein. Fisetin also enhanced the permeability of the mitochondrial membrane and induced the release of cytochrome c and Smac/Diablo. Additionally, fisetin caused an increase in the protein levels of cleaved caspase-8, Fas ligand, death receptor 5, and TNF-related apoptosis-inducing ligand, and the caspase-8 inhibitor Z-IETD-FMK suppressed fisetin-induced apoptosis and the activation of caspase-3. Furthermore, fisetin increases p53 protein levels, and the inhibition of p53 expression by small interference RNA resulted in a decrease in the fisetin-induced translocation of Bax to the mitochondria, release of mono- and oligonucleosome in the cytoplasm, and PARP cleavage. These results show that fisetin induces apoptosis in HCT-116 cells via the activation of the death receptor- and mitochondrial-dependent pathway and subsequent activation of the caspase cascade. The induction of p53 results in the translocation of Bax to the mitochondria, which contributes to fisetin-induced apoptosis in HCT-116 cells.

BackgroundBursopentin (BP5) is a multifunctional pentapeptide found in the chicken bursa of Fabricius. Recent study indicated that BP5 significantly stimulates expression of p53 protein in colon cancer HCT116 cells. However, the effects and underlying mechanisms of BP5 on HCT116 cell proliferation remain largely unclear.MethodsAnalyses of cell viability, cell cycle arrest as well as apoptosis were performed to study the actions of BP5 on HCT116 cells. Western blot analyse was assayed to measure the cell cycle-related and apoptosis-related proteins. Specific siRNAs targeting IRE1, ATF-6, and PERK were used for IRE1, ATF-6, and PERK knockdown, respectively. Cellular reactive oxygen species (ROS) were detected using a H2DCF-DA green fluorescence probe. Cytosolic free Ca2+ concentrations and mitochondrial membrane potential (ΔΨm) were measured using Fluo-3 AM and JC-1 stains, respectively.ResultsBP5 possessed strong inhibitory effects on the cell growth and induced apoptosis in HCT116 cells. Mechanistically, BP5 arrested the cell cycle at G1 phase by increasing p53 and p21 expression and decreasing cyclin E1-CDK2 complex expression. BP5 treatment dramatically activated the endoplasmic reticulum (ER) stress-mediated apoptotic pathway, as revealed by the significantly enhanced expression of unfolded protein response (UPR) sensors (IRE1α, ATF6, PERK) as well as downstream signaling molecules (XBP-1s, eIF2α, ATF4 and CHOP), and by the significantly altered the BP5-induced phenotypic changes in IRE1, ATF6, and PERK knockdown cells. Additionally, BP5-induced ER stress was accompanied by the accumulation of cytosolic free Ca2+ and intracellular ROS. Furthermore, BP5 treatment resulted in the increase of Bax expression, the decrease of Bcl-2 expression and the reduction of ΔΨm, subsequently causing a release of cytochrome c from the mitochondria into the cytoplasm and finally enhancing the activities of caspase-9 and -3. In addition, z-VAD-fmk, a pan-caspase inhibitor, markedly rescued BP5-induced cell viability reduction and reduced BP5-induced apoptosis.ConclusionsOur present results suggest that BP5 has an anticancer capacity to arrest cell cycle at G1 phase and to trigger ER stress/mitochondria-mediated caspase-dependent apoptosis in HCT116 cells. Therefore, our findings provide insight into further investigations of the anticancer activities of BP5.

Colon cancer is the third most common malignancy around the world. Surgery, chemotherapy, and radiotherapy are generally used to treat colon cancer, but no effective therapy for advanced colon carcinoma is available. Therefore, there is a need to identify other therapeutic agents against this disease. Magnolol, a hydroxylated biphenyl compound present in Magnolia officinalis, exerts anticancer potential and low toxicity. Emerging evidence has suggested that activation of AMP-activated protein kinase (AMPK), a potential cancer therapeutic target is involved in apoptosis in colon cancer cells. However, the effects of magnolol on human colon cancer through activation of AMPK remain unexplored. In this study, we explored whether magnolol exerts an antiproliferative effect, and induces apoptosis in HCT-116 human colon cancer cells. Magnolol displayed several apoptotic features, including propidium iodide labeling, DNA fragmentation, and caspase-3 and poly(ADP-ribose) polymerase cleavages. We showed that magnolol induced the phosphorylation of AMPK in dose- and time-dependent manners. The selective AMPK inhibitor compound C abrogated the effect of magnolol on AMPK activation, suppression of proliferation, and caspase-3 cleavage. Magnolol downregulated expression of the antiapoptotic protein Bcl2, upregulated expression of pro-apoptotic protein p53 and Bax, and caused the release of mitochondrial cytochrome c. Magnolol-induced p53 and Bcl2 expression was abolished in the presence of compound C. Magnolol inhibited migration and invasion of HCT-116 cells through AMPK activation. These findings demonstrate that AMPK mediates the anticancer effects of magnolol through apoptosis in HCT-116 cells.

Prostaglandin (PG) A2, one of cyclopentenone PGs, is known to induce activation of apoptosis in various cancer cells. Although PGA2 has been reported to cause activation of apoptosis by altering the expression of apoptosis-related genes, the role of p53, one of the most critical pro-apoptotic genes, on PGA2-induced apoptosis has not been clarified yet. To address this issue, we compared the apoptosis in HCT116 p53 null cells (HCT116 p53-/-) to that in HCT116 cells containing the wild type p53 gene. Cell death induced by PGA2 was associated with phosphorylation of histone H2A variant H2AX (H2AX), activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase 1 in HCT116 cells. Induction of apoptosis in PGA2-treated cells was almost completely prevented by pretreatment with a pan-caspase inhibitor, z-VAD-Fmk, or an inhibitor of protein synthesis, cycloheximide. While PGA2 induced apoptosis in HCT116 cells, phosphorylation of p53 and transcriptional induction of p53-target genes such as p21WAF1, PUMA, BAX, NOXA, and DR5 occurred. Besides, pretreatment of pifithrin-α (PFT-α), a chemical inhibitor of p53’s transcriptional activity, interfered with the induction of apoptosis in PGA2-treated HCT116 cells. Pretreatment of NU7441, a small molecule inhibitor of DNA-activated protein kinase (DNA-PK) suppressed PGA2-induced phosphorylation of p53 and apoptosis as well. Moreover, among target genes of p53, knockdown of DR5 expression by RNA interference, suppressed PGA2-induced apoptosis. In the meanwhile, in HCT116 p53-/- cells, PGA2 induced apoptosis in delayed time points and with less potency. Delayed apoptosis by PGA2 in HCT116 p53-/- cells was also associated with phosphorylation of H2AX but was not inhibited by either PFT-α or NU7441. Collectively, these results suggest the following. PGA2 may induce p53-dependent apoptosis in which DNA-PK activates p53, and DR5, a transcriptional target of p53, plays a pivotal role in HCT116 cells. In contrast to apoptosis in HCT116 cells, PGA2 may induce apoptosis in a fashion of less potency, which is independent of p53 and DNA-PK in HCT116 p53-/- cells

Thymoquinone (TQ), a compound isolated from black seed oil (Nigella sativa), has been reported to possess anti-inflammatory and anticancer activities. However, the molecular mechanisms underlying the anticancer effects of TQ remain poorly understood. In the present study, we found that TQ significantly reduced the viability of human colon cancer HCT116 cells in a concentration- and time-dependent manner. Treatment of cells with TQ induced apoptosis, which was associated with the upregulation of Bax and inhibition of Bcl-2 and Bcl-xl expression. TQ also activated caspase-9,-7, and -3, and induced the cleavage of poly-(ADP-ribose) polymerase (PARP). Pretreatment with a pan-caspase inhibitor, z-VAD-fmk, abrogated TQ-induced apoptosis by blocking the cleavage of caspase-3 and PARP. Treatment of cells with TQ also diminished the constitutive phosphorylation, nuclear localization and the reporter gene activity of signal transducer and activator of transcription-3 (STAT3). TQ attenuated the expression of STAT3 target gene products, such as survivin, c-Myc, and cyclin-D1, -D2, and enhanced the expression of cell cycle inhibitory proteins p27 and p21. Treatment with TQ attenuated the phosphorylation of upstream kinases, such as Janus-activated kinase-2 (JAK2), Src kinase and epidermal growth factor receptor (EGFR) tyrosine kinase. Pharmacological inhibition of JAK2 and Src blunted tyrosine phosphorylation of EGFR and STAT3, while treatment with an EGFR tyrosine kinase inhibitor gefitinib inhibited phosphorylation of STAT3 without affecting that of JAK2 and Src in HCT116 cells. Collectively, our study revealed that TQ induced apoptosis in HCT116 cells by blocking STAT3 signaling via inhibition of JAK2- and Src-mediated phosphorylation of EGFR tyrosine kinase.

Prostaglandin E2 (PGE2) has been reported to play critical roles in cell fate decision by interacting with four types of G protein-coupled membrane receptors such as EP1, EP2, EP3 and EP4. We previously reported that EP4 stimulation by treatment with its agonist CAY10598 induced apoptosis via reactive oxygen species (ROS) formation in colon cancer HCT116 cells. Moreover, treatment with CAY10598 diminished the phosphorylation of JAK2 and induced degradation of this oncoprotein, leading to the attenuation of STAT3 activation in HCT116 cells. In the present study, we attempted to delineate the molecular mechanisms underlying the degradation of JAK2 by activation of EP4. HSP90, a member of the heat shock protein family, is a molecular chaperone that supports stability of client proteins, such as, EGFR, MET, Akt and JAK2. HSP90-mediated stabilization/activation of these client proteins contributes to the acquisition of cancer cell hallmarks, including proliferation, survival, angiogenesis and invasion. It has been recently reported that the chaperoning function of HSP90 may be disrupted by post-translational modification induced by oxidative stress. Treatment of human colon cancer HCT116 cells with CAY10598 down-regulated expression of HSP90 client proteins in a concentration- and time-dependent manner and the down-regulation was restored by pretreatment with ROS scavenger N-acetyl cysteine (NAC) or proteasome inhibitor MG132. However, cotreatment with cycloheximide, protein synthesis inhibitor, accelerated the CAY10598-induced degradation of HSP90 client proteins. These data suggest that CAY10598-induced HSP90 client protein degradation may be caused by ROS generation. In renal carcinoma Caki cells, CAY10598 also down-regulated expression of HSP90 client proteins, suggesting that EP4 stimulation may regulate HSP90 activity in colon cancer cells as well as renal cancer cells. We found that HSP90α was cleaved to 40 or 55 kDa, while HSP90β cleaved to 25 kDa by CAY10598 treatment and the cleavage of HSP90α and β was blocked by NAC treatment. Furthermore, EP4 inhibition by treatment with antagonist GW627368x attenuated not only degradation of HSP90 client proteins but also cleavage of HSP90 in CAY105998-treated HCT116 cells. In conclusions, EP4 agonist CAY10598 induces degradation of HSP90 client proteins via ROS-dependent HSP90 cleavage, leading to apoptosis in HCT116 cells. This is a novel mechanism by which EP4 activation induces apoptosis of cancer cells that involved inhibiting HSP90 function. Citation Format: In Gyeong Chae, Mi-hee Yu, Kyung-Soo Chun. Prostanoid EP4 receptor induces cleavage of HSP90 via ROS generation in human colon cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2317. doi:10.1158/1538-7445.AM2017-2317

Bound polyphenol from foxtail millet bran induces apoptosis in HCT-116 cell through ROS generation

Carnosol, an active constituent of rosemary, has been reported to possess anti-inflammatory and anticancer activities. However, the molecular mechanisms underlying the anticancer effects of carnosol remain poorly understood. In the present study, we found that carnosol significantly reduced the viability of human colon cancer (HCT116) cells in a concentration- and time-dependent manner. Treatment of cells with carnosol induced apoptosis, which was associated with activation of caspase-9 and -3 and the cleavage of poly-(ADP-ribose) polymerase (PARP). Incubation with carnosol elevated the expression of Bax and inhibited the levels of Bcl-2 and Bcl-xl. Carnosol induced expression of p53 and inhibited that of murine-double minute-2 (Mdm2). Moreover, carnosol generated reactive oxygen species (ROS), and pretreatment with N-acetyl cysteine abrogated carnosol-induced cleavage of caspase-3 and PARP. The constitutive phosphorylation, the DNA binding and reporter gene activity of signal transducer and activator of transcription-3 (STAT3) was diminished by treatment with carnosol. To further elucidate the molecular mechanisms of STAT3 inactivation, we found that carnosol attenuated the phosphorylation of Janus-activated kinase-2 (Jak2) and Src kinase. Pharmacological inhibition of Jak2 and Src inhibited STAT3 phosphorylation. Furthermore, carnosol attenuated the expression of STAT3 target gene products, such as survivin, cyclin-D1, -D2, and -D3. Taken together, our study provides the first report that carnosol induced apoptosis in HCT116 cells via generation of ROS, induction of p53, activation of caspases and inhibition of STAT3 signaling pathway.

Lappaconitine hydrochloride inhibits proliferation and induces apoptosis in human colon cancer HCT-116 cells via mitochondrial and MAPK pathway

8-Shogaol from White Ginger induces cell apoptosis and autophagy in human colon cancer HCT116 cells and in vivo.

Cocoa tea (Camellia ptilophylla) induces mitochondria-dependent apoptosis in HCT116 cells via ROS generation and PI3K/Akt signaling pathway.

Objective To investigate the effect of phosphatidylinositol 3 kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitor NVP-BEZ235 on apoptosis induced by oxaliplatin in human colon cancer HCT116 cells. Methods Colon cancer HCT116 cells were cultured in vitro with different concentrations of oxaliplatin and/or dual PI3K/mTOR inhibitor NVP-BEZ235. Methyl thiazol tetrazolium (MTT) assay was used to detect the effects of oxaliplatin and/or dual PI3K/mTOR inhibitor NVP-BEZ235 on cell viability of HCT116 cells. Flow cytometry (FCM) was used to detect the effect of oxaliplatin and/or dual PI3K/mTOR inhibitor NVP-BEZ235 on HCT116 cells. Immunofluorescence was used to detect the effect of oxaliplatin and/or dual PI3K/mTOR inhibitor NVP-BEZ235 on the nuclear morphology of HCT116 cells. Western blotting was used to detect the effects of oxaliplatin and/or dual PI3K/mTOR inhibitor NVP-BEZ235 on DNA damage marker gene gamma histone variant H2A histone family member X (γ-H2AX) and apoptosis-related protein expression. Results The results of MTT showed that 2, 4, 8, 16, 32 and 64 μg/ml oxaliplatin inhibited proliferation of HCT116 cells in a dose-dependent manner, and about 16 μg/ml oxaliplatin platinum could decrease 50% HCT116 cells on the growth. The results of flow cytometry revealed that the apoptosis rate of HCT116 cells treated with 4, 16 and 64 μg/ml oxaliplatin was 11%, 36% and 80% respectively (P=0.026). The results of immunofluorescence demonstrated that the combination of oxaliplatin and NVP-BEZ235 obviously induced the apoptosis of HCT116 cells, and the nuclear shrinkage of HCT116 cells. Western blotting indicated that the expression of Cleaved cysteinyl aspartate-specific protease (Caspase)-3 was significantly increased (P=0.026), and the level of γ-H2AX was also up-regulated (P=0.017). Conclusion Dual PI3K/mTOR inhibitor NVP-BEZ235 significantly enhanced the apoptosis of colon cancer cells induced by oxaliplatin and enhanced the DNA damage of colon cancer cells induced by oxaliplatin. Key words: Colon cancer; Dual phosphatidylinositol 3 kinase/mammalian target of rapamycin; Oxaliplatin; Apoptosis; DNA damage

Aurora kinases (AURKs) are mitotic kinases important for regulating cell cycle progression. Small-molecule inhibitors of AURK have shown promising antitumor effects in multiple cancers; however, the utility of these inhibitors as inducers of cancer cell death has thus far been limited. Here, we examined the role of the Bcl-2 family proteins in AURK inhibition–induced apoptosis in colon cancer cells. We found that alisertib and danusertib, two small-molecule inhibitors of AURK, are inefficient inducers of apoptosis in HCT116 and DLD-1 colon cancer cells, the survival of which requires at least one of the two antiapoptotic Bcl-2 family proteins, Bcl-xL and Mcl-1. We further identified Bcl-xL as a major suppressor of alisertib- or danusertib-induced apoptosis in HCT116 cells. We demonstrate that combination of a Bcl-2 homology (BH)3-mimetic inhibitor (ABT-737), a selective inhibitor of Bcl-xL, Bcl-2, and Bcl-w, with alisertib or danusertib potently induces apoptosis through the Bcl-2 family effector protein Bax. In addition, we identified Bid, Puma, and Noxa, three BH3-only proteins of the Bcl-2 family, as mediators of alisertib–ABT-737-induced apoptosis. We show while Noxa promotes apoptosis by constitutively sequestering Mcl-1, Puma becomes associated with Mcl-1 upon alisertib treatment. On the other hand, we found that alisertib treatment causes activation of caspase-2, which promotes apoptosis by cleaving Bid into truncated Bid, a suppressor of both Bcl-xL and Mcl-1. Together, these results define the Bcl-2 protein network critically involved in AURK inhibitor–induced apoptosis and suggest that BH3-mimetics targeting Bcl-xL may help overcome resistance to AURK inhibitors in cancer cells.