Encorafenib enhances TRAIL-induced apoptosis of colorectal cancer cells dependent on p53/PUMA signaling

TRAIL has been demonstrated to play a critical role in the apoptosis of colorectal cancer (CRC) cells, but drug resistance markedly restricts its therapeutic effects. Objectives: This study aims to investigate whether encorafenib can enhance TRAIL-induced apoptosis of colorectal cancer cells and the underlying mechanism. TRAIL was first used to induce CRC cells. CCK-8 assays were conducted for detecting cell viability of TRAIL-induced CRC cells with encorafenib treatment. Flow cytometry was used to detect the cell apoptosis of CRC cells and western blot was used to measure the expressions of apoptosis-related proteins. The expressions of DR4, DR5, p53, and PUMA were then evaluated by qPCR and western blot. After transfecting the interference plasmid of p53 into CRC cells, the expressions of PUMA and DR5 were further explored. TRAIL reduced the cell viability of CRC cells, and the inhibition was further reinforced under co-treatment of TRAIL and encorafenib. Encorafenib also triggered the promotion of CRC cell apoptosis induced by TRAIL. It was also found that encorafenib exerted its promoting effects on cell apoptosis of CRC cells via the elevation of DR5. Besides, encorafenib administration promoted the expression levels of p53 and PUMA in TRAIL-induced CRC cells. Furthermore, p53 knockdown attenuated the expression of PUMA and DR5 in TRAIL-induced CRC cells treated with encorafenib. This study indicates that encorafenib stimulates TRAIL-induced apoptosis of CRC cells dependent on p53/PUMA signaling, which may provide instructions for the treatment of CRC.     

Annexin A3 depletion overcomes resistance to oxaliplatin in colorectal cancer via the MAPK signaling pathway

Colorectal cancer (CRC) is a common disease with high mortality and morbidity. Annexin A3 (ANXA3) belongs to the structurally homologous family of Ca²⁺ and phospholipid-binding proteins. This study aimed to investigate the effects and potential mechanisms of ANXA3 on oxaliplatin (Ox) resistance in CRC. We generated two human CRC cell lines (HCT116/Ox and SW480/Ox) with acquired Ox resistance and determined their resistance properties. ANXA3 expression and cell apoptosis, migration and invasion also were evaluated. We found that cell viability of HCT116/Ox and SW480/Ox was higher than that in parental cells in the presence of Ox. ANXA3 was highly expressed in HCT116/Ox and SW480/Ox cells. ANXA3 downregulation diminished cell survival, migration and invasion, while increased the apoptosis of HCT116 and SW480 with or without Ox. Moreover, depletion of ANXA3 reduced cell viability and BrdU incorporation, increased cell apoptosis and c-caspase 3 expression in HCT116/Ox with or without Ox. A transwell assay determined that knockdown of ANXA3 impeded the migration and invasion of HCT116/Ox and SW480/Ox cells. Additionally, phosphorylation of extracellular signal–regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) decreased upon ANXA3 depletion in HCT116/Ox cells, and ANXA3 silencing suppressed Ox-induced activation of ERK and JNK signaling pathway. ANXA3 downregulation reduced Ox resistance in CRC, and treatment with the ERK inhibitor PD098059 or JNK inhibitor SP600125 contributed to this process. These results indicate that silencing ANXA3 could overcome Ox resistance in CRC via the mitogen-activated protein kinase signaling pathway.     

Use of Metformin Alone Is Not Associated with Survival Outcomes of Colorectal Cancer Cell but AMPK Activator AICAR Sensitizes Anticancer Effect of 5-Fluorouracil through AMPK Activation

Colorectal cancer (CRC) is still the third most common cancer and the second most common causes of cancer-related death around the world. Metformin, a biguanide, which is widely used for treating diabetes mellitus, has recently been shown to have a suppressive effect on CRC risk and mortality, but not all laboratory studies suggest that metformin has antineoplastic activity. Here, we investigated the effect of metformin and AMPK activator AICAR on CRC cells proliferation. As a result, metformin did not inhibit cell proliferation or induce apoptosis for CRC cell lines in vitro and in vivo. Different from metformin, AICAR emerged antitumor activity and sensitized anticancer effect of 5-FU on CRC cells in vitro and in vivo. In further analysis, we show that AMPK activation may be a key molecular mechanism for the additive effect of AICAR. Taken together, our results suggest that metformin has not antineoplastic activity for CRC cells as a single agent but AMPK activator AICAR can induce apoptosis and enhance the cytotoxic effect of 5-FU through AMPK activation.     

Comprehensive Suppression of All Apoptosis-Induced Proliferation Pathways as a Proposed Approach to Colorectal Cancer Prevention and Therapy

Mutations in the WNT/beta-catenin pathway are present in the majority of all sporadic colorectal cancers (CRCs), and histone deacetylase inhibitors induce apoptosis in CRC cells with such mutations. This apoptosis is counteracted by (1) the signaling heterogeneity of CRC cell populations, and (2) the survival pathways induced by mitogens secreted from apoptotic cells. The phenomena of signaling heterogeneity and apoptosis-induced survival constitute the immediate mechanisms of resistance to histone deacetylase inhibitors, and probably other chemotherapeutic agents. We explored the strategy of augmenting CRC cell death by inhibiting all survival pathways induced by the pro-apoptotic agent LBH589, a histone deacetylase inhibitor: AKT, JAK/STAT, and ERK signaling. The apoptosis-enhancing ability of a cocktail of synthetic inhibitors of proliferation was compared to the effects of the natural product propolis. We utilized colorectal adenoma, drug-sensitive and drug-resistant colorectal carcinoma cells to evaluate the apoptotic potential of the combination treatments. The results suggest that an effective approach to CRC combination therapy is to combine apoptosis-inducing drugs (e.g., histone deacetylase inhibitors, such as LBH589) with agents that suppress all compensatory survival pathways induced during apoptosis (such as the cocktail of inhibitors of apoptosis-associated proliferation). The same paradigm can be applied to a CRC prevention approach, as the apoptotic effect of butyrate, a diet-derived histone deacetylase inhibitor, is augmented by other dietary agents that modulate survival pathways (e.g., propolis and coffee extract). Thus, dietary supplements composed by fermentable fiber, propolis, and coffee extract may effectively counteract neoplastic growth in the colon.     

Upregulation of UGT1A1 expression by ursolic acid and oleanolic acid via the inhibition of the PKC/NF-κB signaling pathway

BackgroundIsomeric ursolic acid (UA) and oleanolic acid (OA) compounds have recently garnered great attention due to their biological effects. Previously, it had been shown that UA and OA can exert important pharmacological action via the protein kinase C (PKC) and nuclear factor-κB (NF-κB) signaling, and that they can induce the expression of UDP-glucuronosyltransferase 1A1 (UGT1A1) in HepG2 cells. This study aims to investigate the role of PKC/NF-κB signaling in regulating the expression of UGT1A1 and examine how UA and OA induce UGT1A1 based on this signaling pathway.MethodsHepG2 cells, hp65-overexpressed HepG2 cell and lentivirus-hp65-shRNA silenced HepG2 cells were stimulated with PKC/NF-κB specific agonists and inhibitors for 24 h in the presence or absence of UA and OA. The expression of UGT1A1, PKC, and NF-κB were determined by qRT-PCR, western blot, and dual-luciferase reporter gene assays.ResultsPKC/NF-κB activation downregulates UGT1A1 expression. This effect is countered by UA and OA treatment. Phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS), the agonists of PKC and NF-κB signaling, respectively, significantly inhibit hp65-mediated UGT1A1 luciferase activity. UA, OA, and the PKC/NF-κB inhibitors suppress this effect. PMA and LPS do not affect UGT1A1 activity in p65-silenced HepG2 cells; however, UA and OA mildly influence UGT1A1 expression in these cells.ConclusionThe activation of PKC/NF-κB signaling can significantly downregulate UGT1A1 expression. By inhibiting the PKC/NF-κB signaling pathway, UA and OA promote UGT1A1 expression in HepG2 cells.     

ZNF746 plays cardinal roles on colorectal cancer (CRC) cell invasion and migration and regulates mitochondrial dynamics and morphological changes of CRC cells—Role of combined melatonin and 5-FU regimen

The underlying mechanism of colorectal cells developing into cancer cells has been extensively investigated, yet is still not fully delineated, resulting in the treatment of advanced colorectal cancer (CRC) remains regrettably an unmet need. Zinc Finger Protein 746/Parkin-interacting substrate (ZNF746/PARIS) has previously been identified to play a fundamental role on bladder cancer cell proliferation and metastasis that were effectively inhibited by melatonin (Mel). In this study, we utilized ex vivo/in vivo studies to verify whether the ZNF746 signaling was also crucial in CRC growth/invasion/migration. Tissue-bank specimens showed that the protein expression of ZNF746 was significantly increased in CRC than that of healthy colorectal tissues (p < 0.001). Additionally, in vitro study demonstrated that excessive expression of ZNF746 significantly inhibited mitochondrial activity via (1) interfering with the dynamic balance of mitochondrial fusion/fission and (2) inhibiting the protein expression of MFN1/MFN2/PGC1a (all p < 0.001). Furthermore, we identified that inhibition of ZNF746 protein expression significantly reduced the resistance of CRC cell lines to the anticancer drug of 5-FU (p < 0.001), whereas overexpression of ZNF746 significantly augmented resistance of CRC cells to 5-FU (all p < 0.001). Finally, using the cell culture method, we found that combined Mel and 5-FU was superior to merely one on promoting the CRC cell apoptosis (p < 0.001). Our results confirmed that ZNF746 signaling played a cardinal role of CRC cell proliferation/survival and combined Mel and 5-FU treatment attenuated the resistance of CRC cells to the drug mainly through suppressing this signaling.     

Atractylenolide I inhibits colorectal cancer cell proliferation by affecting metabolism and stemness via AKT/mTOR signaling

BackgroundAtractylenolide I (ATL-1) is a natural herbal compound used in traditional Chinese medicine that has exhibited anti-cancer properties. The anti-tumorigenic activity of ATL-1 against colorectal cancer (CRC) and the underlying signaling pathways involved in its mechanisms are examined here.HypothesisATL-1 exerts therapeutic effect against CRC by disrupting glucose metabolism and cancer stem cell maintenance via AKT/mTOR pathway regulation.Study designIn vitro studies were performed in COLO205 and HCT116 CRC cell lines and in vivo studies were conducted in a mouse xenograft model of CRC tumor.MethodsCRC cells were treated with ATL-1 at various concentrations, with or without inhibitors of AKT or mTOR. Cell proliferation, apoptosis, invasion, stemness maintenance, glucose metabolism, and AKT/mTOR signaling were evaluated. CRC tumor-xenografted mice were treated with an AKT inhibitor and/or ATL-1, and glucose metabolism and stemness maintenance were examined in tumor tissues.ResultsATL-1 significantly inhibited the invasion of CRC cells by inducing their apoptosis, possibly via the excessive production of reactive oxygen species. Glucose metabolism (Warburg effect) was also altered and stem-like traits were suppressed by ATL-1. In addition, ATL-1 effectively acted as an inhibitor or AKT/mTOR by downregulating the phosphorylation of proteins related to the AKT/mTOR pathway. In vivo studies showed that tumor weight and volume were reduced by ATL-1 and that aerobic glycolysis, stemness maintenance, and AKT/mTOR activation were impaired by ATL-1 in colorectal tumors.ConclusionsATL-1 acts as an effective agent to suppress colorectal tumor progression, mainly by inhibiting CRC cell proliferation through altering apoptosis, glucose metabolism, and stem-like behavior. These processes were mediated by the AKT/mTOR signaling pathway both in vitro and in vivo. ATL-1 may be a potential agent to be used in molecular-targeted strategies for cancer treatment.     

Monomer gypenoside LI from Gynostemma pentaphyllum inhibits cell proliferation and upregulates expression of miR‐128‐3p in melanoma cells

Gypenosides have anticancer activity against many cancers. Gypenoside LI is a gypenoside monomer from Gynostemma pentaphyllum, its pharmacological functions in melanoma have not been reported. In this study, we found that gypenoside LI had a potent cytotoxic effect on melanoma cells. Gypenoside LI can induce intrinsic apoptosis along with S phase arrest. Furthermore, gypenoside LI inhibited the colony formation ability of melanoma through inhibition of the Wnt/β‐catenin signaling pathway. Interestingly, we also found that gypenoside LI can induce the upregulation of the tumor suppressor miR‐128‐3p during melanoma apoptosis. In contrast, gypenoside LI induced apoptosis, cell cycle arrest, and inhibition of the Wnt/β‐catenin signaling pathway, which were abolished by overexpression of the miR‐128‐3p inhibitor in A375 cells. Taken together, these results showed that gypenoside LI could inhibit human melanoma cells through inducing apoptosis, arresting cell cycle at the S phase and suppressing the Wnt/β‐catenin signaling pathway in a miR‐128‐3p dependent manner.     

Protein disulfide isomerase inhibits endoplasmic reticulum stress response and apoptosis via its oxidoreductase activity in colorectal cancer

Protein disulfide isomerase (PDI), a principal endoplasmic reticulum resident oxidoreductase chaperone, is known to play a role in malignancies. This study aims to explore the molecular mechanism by which PDI regulates endoplasmic reticulum stress and the apoptosis signaling pathway in colorectal cancer (CRC). We determined the expression of PDI in CRC tissues and adjacent normal tissues. Gain- and loss- of function assays were conducted to evaluate the effects of PDI on oxidative stress, endoplasmic reticulum stress, and apoptosis in CRC cells, as reflected by hydrogen peroxide (H₂O₂) level and the expression of related proteins. PDI protein expression was upregulated in CRC tissues. Small molecule inhibitor of PDI or PDI knockdown reduced CRC cell viability and induced apoptosis. Overexpression of wild-type PDI augmented the viability of CRC cells and inhibited endoplasmic reticulum stress response and apoptosis. Small molecule inhibitor of PDI or PDI knockdown increased intracellular H₂O₂ level and activated apoptosis signaling pathway, which could be reversed by wild-type PDI restoration. Moreover, the catalytic active site of C-terminal of PDI was found to be indispensable for the regulatory effects of PDI on H₂O₂ levels, apoptosis and cell viability in CRC cells. Collectively, PDI inhibits endoplasmic reticulum stress and apoptosis of CRC cells through its oxidoreductase activity, thereby promoting the malignancy of CRC.     

circPPP1R12A激活p53信号通路调控骨关节炎中软骨细胞增殖和凋亡

摘要 目的：探讨circPPP1R12A（circ_0000423）调控p53信号通路对骨关节炎（osteoarthritis,OA）中软骨细胞增殖和凋亡的影响。方法：采用qRT-PCR检测circPPP1R12A在OA软骨细胞中的表达水平。在OA软骨细胞中分别转染oe-circPPP1R12A和sh-circPPP1R12A后,采用CCK-8检测细胞增殖情况;免疫荧光检测Ki-67阳性细胞表达率;流式细胞术检测细胞凋亡情况;qRT-PCR检测Ki-67和p53表达水平;Western Blot检测Cleaved-caspase3、P53、BCL-2和BAX的表达水平。结果：OA软骨细胞中circPPP1R12A的表达水平明显高于正常软骨细胞。过表达circPPP1R12A能够抑制OA软骨细胞增殖和促进细胞凋亡,通过上调p53表达激活p53信号通路,低表达circPPP1R12A能够促进OA软骨细胞增殖和抑制细胞凋亡,通过下调p53表达阻滞p53信号通路。在OA软骨细胞中同时低表达circPPP1R12A和过表达p53能够反转单独低表达circPPP1R12A对OA软骨细胞增殖和凋亡的影响。结论：circPPP1R12A在OA软骨细胞中明显高表达,circPPP1R12A能够通过激活p53信号通路抑制骨OA软骨细胞增殖和促进软骨细胞凋亡。circPPP1R12A可能成为OA治疗的干预靶点。     

Valosin-containing protein (VCP) promotes the growth,invasion, and metastasis of colorectal cancer through activation of STAT3 signaling

Valosin-containing protein (VCP) was previously shown to exhibit high expression in colorectal cancer (CRC) tissues as compared with that in normal tissues; however, the role of VCP in human CRC cells has remained to be elucidated. Two colorectal cancer cell lines HCT116 and RKO were used in the experiment. We introduced lentiviral constructs expressing VCP to infect RKO cells and lenti-shRNA targeting VCP into HCT116 cells, respectively. Cell proliferation, invasion, apoptosis, and cell cycle arrest were subsequently examined by MTT assay, transwell chamber assay, flow cytometry, and western blot analysis, respectively. Furthermore, a subcutaneous tumor mouse model and lung metastasis model was used to investigate the effects of VCP on the growth and metastasis of CRC cells in vivo. VCP knockdown was shown to inhibit cell proliferation, chemoresistance and invasion, and induce apoptosis in the HCT116 CRC cells, whereas VCP over-expression suppressed apoptosis and chemoresponse, promoted proliferation and invasion of the RKO CRC cells. In addition, in the subcutaneous tumor and lung metastasis mouse model, VCP knockdown in HCT116 cells suppressed carcinogenesis and metastasis in vivo. The findings of the present study indicated that VCP is very important for the proliferation and metastasis of CRC; therefore, targeting VCP and its downstream targets may represent novel therapies for the treatment of CRC.

     

Protosappanin‐A and oleanolic acid protect injured podocytes from apoptosis through inhibition of AKT‐mTOR signaling

Protosappanin‐A (PrA) and oleanolic acid (OA), which are important effective ingredients isolated from Caesalpinia sappan L., exhibit therapeutic potential in multiple diseases. This study focused on exploring the mechanisms of PrA and OA function in podocyte injury. An in vitro model of podocyte injury was induced by the sC5b‐9 complex and assays such as cell viability, apoptosis, immunofluorescence, quantitative real‐time polymerase chain reaction, and western blot were performed to further investigate the effects and mechanisms of PrA and OA in podocyte injury. The models of podocyte injury were verified to be successful as seen through significantly decreased levels of nephrin, podocin, and CD2AP and increased level of desmin. The sC5b‐9‐induced podocyte apoptosis was inhibited in injured podocytes treated with PrA and OA, accompanied by increased protein levels of nephrin, podocin, CD2AP, and Bcl2 and decreased levels of desmin and Bax. The p‐AKT/p‐mTOR levels were also reduced by treatment of PrA and OA while AKT/mTOR was unaltered. Further, the effects of PrA and OA on injured podocytes were similar to that of LY294002 (a PI3K‐AKT inhibitor). PrA and OA were also seen to inhibit podocyte apoptosis and p‐AKT/p‐mTOR levels induced by IGF‐1 (a PI3K‐AKT activator). Our data demonstrate that PrA and OA can protect podocytes from injury or apoptosis, which may occur through inhibition of the abnormal activation of AKT‐mTOR signaling.     

Differential induction of apoptosis and inhibition of the PI3-kinase pathway by saturated, monounsaturated and polyunsaturated fatty acids in a colon cancer cell model

Although numerous studies have shown that certain long chain fatty acids can induce apoptosis in cancer cells, the molecular mechanisms for this phenomenon are still poorly elucidated. The phosphoinositide 3-kinase (PI3-kinase) signaling pathway plays a pivotal role in the regulation of cell growth and can also contribute to tumorigenesis and cancer progression. The aims of the present study were three fold: (i) to investigate the potential chemopreventative/antiproliferative effect of various fatty acids in colon cancer cells (CaCo-2 cells) and normal colon epithelium cells (NCM460 cells); (ii) to investigate the mechanisms by which incubation with various fatty acids influences the PI3-kinase pathway in CaCo-2 cells; and (iii) to evaluate apoptosis in our cell model. Although all the fatty acids increased the viability of normal (NCM460) cells, only docosahexaenoic acid (DHA) significantly reduced cell viability and induced apoptosis in the cancer (CaCo-2) cells. Our results indicate that DHA is an effective chemotherapeutic agent to induce apoptosis in cancer cells and that this effect is mediated by the PI3-kinase signaling pathway.     

FLI‐1 mediates tumor suppressor function via Klotho signaling in regulating CRC

Colorectal cancer (CRC) is an aggressive malignancy with a high incidence and mortality rate. Although a targeting therapy has been developed, the 5‐year survival rate is still very low in CRC patients with distant metastasis. Thus, the identification of new targets is still significant for improving CRC treatment. Klotho is a tumor suppressor, and its expression is aberrant in CRC. In this study, the roles of the FLI‐1 gene in regulating Klotho gene expression and Klotho‐associated signaling, as well as the effects of FLI‐1 on colony formation, invasion, and apoptosis were investigated in CRC cell lines. The methylation of the FLI‐1 gene was analyzed using a commercial methylation kit. Results showed that FLI‐1 messenger RNA and protein expression were downregulated in six CRC cell lines when compared with the normal colon mucosal epithelial cell line, which negatively correlated with the level of DNA methylation. Silencing of FLI‐1 gene expression decreased Klotho protein expression and phosphorylation of β‐catenin protein at Thr⁴¹/Ser⁴⁵, but increased Wnt3a and β‐catenin protein expression and IGF‐1R phosphorylation in HT29 cells. In contrast to silencing FLI‐1, overexpressing FLI‐1 significantly increased Klotho protein expression and phosphorylation of β‐catenin protein at Thr⁴¹/Ser⁴⁵, but decreased Wnt3a and β‐catenin protein expression and IGF‐1R phosphorylation in Caco‐2 cells. Silencing of FLI‐1 gene expression significantly increased colony formation and invasion, but decreased apoptosis in HT29 cells. In contrast, overexpressing the FLI‐1 gene significantly decreased colony formation and invasion, but increased apoptosis in Caco‐2 cells. These findings suggest that FLI‐1 functions as a tumor suppressor in CRC cells and positively regulates Klotho signaling. Hypermethylation may be one of the causes of the loss of FLI‐1 gene expression in CRC cells.     

Silencing of RHEB inhibits cell proliferation and promotes apoptosis in colorectal cancer cells via inhibition of the mTOR signaling pathway

Colorectal cancer (CRC) is commonly known as one of the most prominent reasons for cancer-related death in China. Ras homolog enriched in brain (RHEB) and the mammalian target activity of rapamycin (mTOR) signaling pathway were found correlated with CRC, but their specific interaction in CRC was still to be investigated. Therefore, we explored whether RHEB gene silencing affected the cell proliferation, differentiation, and apoptosis by directly targeting the mTOR signaling pathway in cells previously harvested from CRC patients. A microarray analysis was subsequently conducted to investigate the relationship between RHEB and mTOR. Eighty-three adjacent normal tissues and CRC tissues were selected. Immunohistochemistry was carried out to detect the positive expression rates of RHEB and Ki-67 in the CRC tissues. Cells were then transfected with different siRNAs to investigate the potential effects RHEB would have on CRC progression. The expressions of RHEB, 4EBP1, ribosomal protein S6 kinase (p70S6K), proliferating cell nuclear antigen (PCNA), B cell lymphoma 2 (bcl-2), and bcl-2-associated X protein (bax) were determined and then the cell cycle, cell proliferation, and apoptotic rate were also measured. We identified RHEB and mTOR as upregulated genes in CRC. Cells treated with RHEB silencing showed a decreased extent of mTOR, p70S6K, 4EBP1 phosphorylation and expression of RHEB, Ki-67, mTOR, p70S6K, 4EBP1, bcl-2, and PCNA as well as decreased activity of cell proliferation and differentiation; although, the expression of bax was evidently higher. Collectively, our data propose the idea that RHEB gene silencing might repress cell proliferation and differentiation while accelerating apoptosis via inactivating the mTOR signaling pathway.