ag-490 and Colonic-Neoplasms

The study aimed to investigate the reason of HCT116 cell resistance to MEK inhibitor, and the combination treatment effects of MEK inhibitor AZD6244 and JAK2/STAT3 inhibitor AG490 on colon cancer in vitro and in vivo, including cell viability, apoptosis, and explore the partial mechanisms focused on AZD6244 promoted the activation of JAK2-STAT3 pathways. In vitro, we examined the HCT116 cell viability by CCK8, cell apoptosis by flow cytometry; Western blot measured p-ERK, p-JAK2, p-STAT3 and STAT3 expression. In vivo, nude mice were subcutaneously injected by HCT116 cells. The tumor volume and weight were detected. HCT116 cell resistance to MEK inhibitor AZD6244, which inhibited the activation of ERK and promoted the activation of JAK2-STAT3 signaling. The combination treatment of AZD6244 and AG490 significantly inhibited cell viability and induced cell apoptosis, and completely inhibited the activation of ERK and JAK2-STAT3 signaling. Combination treatment of AZD6244 and AG490 had a stronger effect than that of AZD6244 as a monotherapy in vitro and in vivo. The treatment of AZD6244 on K-Ras mutations HCT116 cells promoted the activation of JAK2/STAT3 signaling. JAK2/STAT3 inhibitor AG490 synergistically increases effects of AZD6244 on colon cancer in vitro and in vivo. Collectively, these results provide a rationale for combining inhibitors of the JAK/STAT pathway and MEK inhibitors to reduce the potential impact of drug resistance.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Colonic Neoplasms; HCT116 Cells; Humans; Janus Kinase 2; MAP Kinase Kinase Kinases; Mice, Nude; Protein Kinase Inhibitors; Signal Transduction; STAT3 Transcription Factor; Tyrphostins; Xenograft Model Antitumor Assays

The purpose of the research is to investigate the roles of Jak-STAT3 signaling pathway in bufalin-induced apoptosis in colon cancer SW620 cells.. The inhibitory effects of bufalin on cell proliferation were determined by MTT (Methyl thiazolyltetrazolium) assay. The morphological changes of cells were measured by Wright-Giemsa staining. The cell cycle arrest and apoptosis were tested by flow cytometry analysis. Western Blot was used to determine the protein expression of the apoptosis inhibitors livin and caspase-3, the apoptosis-related proteins Bax and Bcl-2, as well as the key protein kinases in the Jak-stat3 signaling pathway, stat3 and p-stat3.. (1) Bufalin inhibited the proliferation of SW620 cells. IC50 at 24 h, 48 h and 72 h were 76.72 ± 6.21 nmol/L, 34.05 ± 4.21 nmol/L and 16.7 ± 6.37 nmol/L. (2) Bufalin induced SW620 cell cycle arrest and apoptosis, indicated by the appearance of apoptotic bodies; (3) The results from flow cytometry demonstrated that there was cell cycle G2/M phase arrest in 20 nmol/L bufalin treatment group (36.29 ± 2.11% vs 18.39 ± 1.74%, P<0.01); there was a sub-diploid apoptosis peak in 80 nmol/L bufalin treatment group (19.69 ± 1.63% vs 0.99 ± 0.23%, P <0.01). The apoptosis rate was 34.63 ± 2.57% (vs 19.69 ± 1.63%, P = 0.002) in JAK kinase inhibitor AG490 plus bufalin treatment group. (4) During the process of bufalin-induced apoptosis in SW620 cells, transient activation of p-stat3 inhibited the activation of stat3, up-regulated Bax expression, down-regulated livin and Bcl-2 expression (P<0.01), and activated caspase-3. Inhibition of Jak-stat3 signaling pathway by pre-treatment with AG490 significantly enhanced the bufalin-induced apoptosis (P<0.01), further up-regulated Bax protein expression, down-regulated livin and Bcl-2 protein expression and enhanced caspase-3 activation.. Bufalin not only inhibited the growth of colon cancer SW620 cells, but also induced apoptosis of SW620 cells. Activation of caspase-3, up-regulation of Bax, down-regulation of livin and Bcl-2, as well as inhibition of Jak-stat3 signaling pathway might be the important mechanisms for the bufalin-induced apoptosis.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Blotting, Western; Bufanolides; Cell Cycle; Cell Proliferation; Colonic Neoplasms; Enzyme Inhibitors; Humans; Janus Kinase 1; Mitotic Index; STAT3 Transcription Factor; Tumor Cells, Cultured; Tyrphostins

Glycine-extended gastrin (G-Gly) is produced by colon cancers and has growth promoting and anti-apoptotic effects in the colonic epithelium. We have examined the anti-apoptotic effects of G-Gly and the signal transduction pathways involved. G-Gly stimulated HT-29 cell proliferation in a concentration dependent manner and inhibited serum-starvation and celecoxib-induced apoptosis. Inhibition of signalling via c-Jun NH2-terminal kinase (JNK) with SP600125 or PI3-kinase/Akt with LY294002 abolished the effects of G-Gly. G-Gly significantly increased phosphorylation of both JNK and Akt. The JAK2 inhibitor AG490 abolished the anti-apoptotic effect of G-Gly and inhibited phosphorylation of Akt but not of JNK. G-Gly stimulated tyrosine phosphorylation of JAK2. G-Gly-increased activation of AP-1 was JNK-dependant and activation of STAT3 was JAK2-dependant. We conclude that G-Gly promotes growth and inhibits apoptosis in colon cancer cells. These effects are mediated via the JAK2, PI3-kinase/Akt and JNK pathways. Activation of JAK2 is upstream of Akt but not of JNK.

Topics: Anthracenes; Apoptosis; Celecoxib; Cell Line, Tumor; Cell Survival; Chromones; Colonic Neoplasms; Gastrins; Humans; Janus Kinase 2; JNK Mitogen-Activated Protein Kinases; Morpholines; Phosphatidylinositol 3-Kinases; Phosphorylation; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Pyrazoles; Signal Transduction; STAT3 Transcription Factor; Sulfonamides; Transcription Factor AP-1; Tyrosine; Tyrphostins

Kaempferol induces differentiation in partially differentiated colon cancer cells which express low levels of connexin43 protein and connexin43 mRNA (KNC cells). Differentiation was observed as changes in cell morphology and the activity of alkaline phosphatase. Increased differentiation in kaempferol-treated KNC cells correlated with restoration of gap junctional intercellular communication (GJIC), increased levels of connexin43 protein and its phosphorylation status. Phosphorylation (activation) of Stat3 and Erk was also reduced by kaempferol. An inhibitor of Stat3 phosphorylation also induced morphological changes in KNC cells similar to those in kaempferol-treated cells, suggesting that kaempferol-induced differentiation may be mediated by inhibition of Stat3 phosphorylation. These effects were not observed in HCT116 cells, a poorly differentiated colon cancer cell line deficient in expression of connexin43 mRNA and connexin43 protein. In conclusion, kaempferol might function as an anticancer agent by re-establishing GJIC through enhancement of the expression and phosphorylation of connexin43 protein in a tumorigenic colon cancer cell line that already expresses connexin43 mRNA via a Stat3-dependent mechanism. In contrast, kaempferol had no effect in a tumorigenic colon cancer cell line that did not express connexin43 mRNA and was deficient in GJIC.

Topics: Alkaline Phosphatase; Base Sequence; Cell Differentiation; Cell Line; Colonic Neoplasms; Connexin 43; DNA Primers; DNA-Binding Proteins; Gap Junctions; Humans; Kaempferols; STAT3 Transcription Factor; Trans-Activators; Tyrphostins

Signal transducer and activator of transcription 3 (STAT3) has oncogenic potential. The biological effects of STAT3 have not been studied extensively in the pathogenesis of colon cancer, nor has the role of Janus kinase 3 (JAK3), the physiological activator of STAT3, been evaluated. Here, we demonstrate that activated STAT3 (pSTAT3) and activated JAK3 (pJAK3) are expressed constitutively in two colon cancer cell lines, SW480 and HT29. To evaluate the significance of JAK3/STAT3 signaling, we inhibited JAK3 with AG490 and STAT3 with a dominant-negative construct. Inhibition of JAK3 down-regulated pSTAT3. The blockade of JAK3/STAT3 signaling significantly decreased viability of colon cancer cells due to apoptosis and cell-cycle arrest through down-regulation of Bcl-2, Bcl-X(L), Mcl-1, and cyclin D2 and up-regulation of p21(waf1/cip1) and p27(kip1). We also examined histological sections from 22 tumors from patients with stage II or stage IV colon cancer and found STAT3, JAK3, and their activated forms to be frequently expressed. Furthermore, quantitative reverse transcriptase-polymerase chain reaction identified JAK3 mRNA in colon cancer cell lines and primary tumors. Our findings illustrate the biological importance of JAK3/STAT3 activation in the oncogenesis of colon cancer and provide novel evidence that JAK3 is expressed and contributes to STAT3 activation in this malignant neoplasm.

Topics: Aged; Apoptosis; Carcinoma; Cell Cycle; Cell Line, Tumor; Cell Survival; Colonic Neoplasms; Cyclin D2; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; Enzyme Activation; Enzyme Inhibitors; Female; Gene Expression Regulation, Neoplastic; HT29 Cells; Humans; Immunohistochemistry; Janus Kinase 3; Male; Middle Aged; Neoplasm Staging; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-bcl-2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Tyrphostins