α-Carboline derivative TJY-16 inhibits tumor growth by inducing G2/M cell cycle arrest in glioma cells.

BACKGROUND: Glioblastoma multiforme (GBM) is the most lethal primary brain tumors which remains difficult to cure despite advances in surgery, radiotherapy and chemotherapy. Therefore, the development of new drug is urgently needed. α-carboline derivatives were usually isolated from marine animals such as Britannia marine tunicate Dendrodoa grossularia and Indonesian ascidian Polycarpa aurata. In this study, we have synthesized several α-carboline compounds and examined their anti-glioma activities. RESULTS: We report that among α-carboline derivatives TJY-16 (6-acetyl-9-(3,4,5-trimethoxybenzyl)-9H-pyrido[2,3-b] indole) is the most potent α-carboline analog to induce glioma cell death with IC50 value of around 50 nM. TJY-16 decreased cell viability of glioma cells in a concentration- and time-dependent manner. Trypan blue exclusion assay showed that the reduction of cell viability was due to both cell growth inhibition and cell death. Flow cytometric analysis showed that TJY-16 induced G2/M cell cycle arrest followed by induction of sub-G1 phase. Hoechst staining detected the apoptotic features such as nuclear shrinkage and DNA condensation. Western blot analysis showed the increased level of cleaved caspase-3. The activation of caspase-8 and depolarization of mitochondrial membrane potential (ΔΨm) indicated that both extrinsic and intrinsic apoptotic pathways were involved in TJY-16-induced apoptosis. TJY-16 effectively inhibited tumor growth and induced caspase-3 activation in the xenograft tumor model of U87 glioma cells. CONCLUSIONS: Our results suggest that TJY-16 may kill glioma cells by inducing G2/M cell cycle arrest followed by apoptosis. Thus, TJY-16 is a promising agent for the treatment of malignant gliomas.

The novel synthetic compound 6-acetyl-9-(3,4,5-trimetho-xybenzyl)-9H-pyrido[2,3-b]indole induces mitotic arrest and apoptosis in human COLO 205 cells.

A novel synthetic compound 6-acetyl-9-(3,4,5-trimetho-xybenzyl)-9H-pyrido[2,3-b]indole (HAC-Y6) demonstrated selective anticancer activity. In the present study, COLO 205 cells were treated with HAC-Y6 to investigate the molecular mechanisms underlying its effects. HAC-Y6 induced growth inhibition, G2/M arrest and apoptosis in COLO 205 cells with an IC50 of 0.52±0.035 µM. Annexin V/PI double staining demonstrated the presence of apoptotic cells. JC-1 staining analysis showed that HAC-Y6 decreased mitochondrial membrane potential in support of apoptosis. An immunostaining assay revealed that HAC-Y6 depolymerized microtubules. Treatment of COLO 205 cells with HAC-Y6 resulted in increased expression of BubR1 and cyclin B1 and decreased expression of aurora A, phospho-aurora A, aurora B, phospho-aurora B and phospho-H3. HAC-Y6 treatment increased protein levels of active caspase-3, caspase-9, Endo G, AIF, Apaf-1, cytochrome c and Bax, but treatment with the compound caused reduced levels of procaspase-3, procaspase-9, Bcl-xL and Bcl-2. Overall, our results suggest that HAC-Y6 exerts anticancer effects by disrupting microtubule assembly and inducing G2/M arrest, polyploidy and apoptosis via mitochondrial pathways in COLO 205 cells.

Synthesis and cytotoxicity of 1,6,8,9-substituted α-carboline derivatives.

α-Carboline (pyrido[2,3-b]indole) was selected as the basic scaffold for development of antileukemic agents by structural modification. From the structure-activity study, it was found that sequential introduction of 6-acetyl and 9-substituted benzyl groups onto an α-Carboline scaffold resulted in 6-acetyl-9-(3,5-dimethoxybenzyl)-9H-pyrido[2,3-b]indole and 6-acetyl-9-(3,4,5-trimethoxybenzyl)-9H-pyrido[2,3-b]indole with potent cytotoxicity against the HL-60 cell line. These two compounds will be used as new lead compounds for further investigation.

Induction of apoptosis by HAC-Y6, a novel microtubule inhibitor, through activation of the death receptor 4 signaling pathway in human hepatocellular carcinoma cells.

The present data showed that a novel synthesized compound, 6-acetyl-9-(3,4,5-trimethoxybenzyl)-9H-pyrido [2,3-b]indole (HAC-Y6), exhibited potent antitumor activity against human hepatocellular carcinoma (HCC) cells in vitro. Western blot and immunofluorescence experiments showed that HAC-Y6 depolymerized microtubules similarly to the effects of colchicine. HAC-Y6-treatment in Hep3B cells resulted in the accumulation of the G2/M phase and induced apoptosis. In addition, HAC-Y6-treatment influenced the expression of cell cycle and apoptosis related proteins in Hep3B cells. HAC-Y6 exposure increased caspases-3, -8, -9 and Bax protein levels, while reducing levels of Bcl-2 family proteins. Moreover, Bid, a substrate of caspase-8, was also activated by HAC-Y6. Treatment of cells caused the up-regulation of the death receptor 4 (DR4) and phosphorylation of p38. Taken together, we show that HAC-Y6 exhibited its antitumor activity by disrupting microtubule assembly, causing cell cycle arrest and apoptosis through both extrinsic and intrinsic pathways in Hep3B cells. Therefore, the novel compound HAC-Y6 is a promising microtubule inhibitor that has great potential for treatment of HCC.