Chun-Han Chen

The HDAC inhibitor, MPT0E028, enhances erlotinib-induced cell death in EGFR-TKI-resistant NSCLC cells.

Epidermal growth factor receptor (EGFR), which promotes cell survival and division, is found at abnormally high levels on the surface of many cancer cell types, including many cases of non-small cell lung cancer. Erlotinib (Tarceva), an oral small-molecule tyrosine kinase inhibitor, is a so-called targeted drug that inhibits the tyrosine kinase domain of EGFR, and thus targets cancer cells with some specificity while doing less damage to normal cells. However, erlotinib resistance can occur, reducing the efficacy of this treatment. To develop more effective therapeutic interventions by overcoming this resistance problem, we combined the histone deacetylase inhibitor, MPT0E028, with erlotinib in an effort to increase their antitumor effects in erlotinib-resistant lung adenocarcinoma cells. This combined treatment yielded significant growth inhibition, induced the expression of apoptotic proteins (PARP, γH2AX, and caspase-3), increased the levels of acetylated histone H3, and showed synergistic effects in vitro and in vivo. These effects were independent of the mutation status of the genes encoding EGFR or K-Ras. MPT0E028 synergistically blocked key regulators of the EGFR/HER2 signaling pathways, attenuating multiple compensatory pathways (e.g., AKT, extracellular signal-regulated kinase, and c-MET). Our results indicate that this combination therapy might be a promising strategy for facilitating the effects of erlotinib monotherapy by activating various networks. Taken together, our data provide compelling evidence that MPT0E028 has the potential to improve the treatment of heterogeneous and drug-resistant tumors that cannot be controlled with single-target agents.

Protopine, a novel microtubule-stabilizing agent, causes mitotic arrest and apoptotic cell death in human hormone-refractory prostate cancer cell lines

In this study, we investigated the anticancer effect of protopine on human hormone-refractory prostate cancer (HRPC) cells. Protopine exhibited an anti-proliferative effect by induction of tubulin polymerization and mitotic arrest, which ultimately led to apoptotic cell death. The data suggest that protopine increased the activity of cyclin-dependent kinase 1 (Cdk1)/cyclin B1 complex and that contributed to cell apoptosis by modulating mitochondria-mediated signaling pathways, such as Bcl-2 phosphorylation and Mcl-1 down-regulation. In conclusion, the data suggest that protopine is a novel microtubule stabilizer with anticancer activity in HRPC cells through apoptotic pathway by modulating Cdk1 activity and Bcl-2 family of proteins.

Thrombin induces expression of twist and cell motility via the hypoxia-inducible factor-1α translational pathway in colorectal cancer cells

Deep vein thrombosis associated with advanced cancer is known as Trousseaus syndrome. We hypothesized that thrombin, an activator of protease‐activated receptor (PAR)‐1 and PAR‐4 contributes to tumor metastasis. In this study, we demonstrated that thrombin and the PAR‐1 activating peptide (AP) SFLLRN, but not the PAR‐4 AP GYPGKF, induced HIF‐1α activities, protein expression, and cell motility in colorectal cancer cells, and these actions were significantly inhibited by the PAR‐1 antagonist SCH79797. Moreover, thrombin‐induced HIF‐1α activity and cell motility were blocked by inhibiting important mediators of signaling transduction, including the ERK, PI3K, and mTOR pathways. These results showed that thrombin induced HIF‐1α protein expression through PAR‐1 and HIF‐1α translational de novo protein synthesis. Twist can regulate epithelial–mesenchymal transition (EMT) and increase tumor metastasis. However, we observed that thrombin‐induced HIF‐1α increased Twist mRNA and its protein level was mediated by the modulation of PAR‐1 activation and the HIF‐1α translational pathway. In addition, Twist could increase N‐cadherin but not E‐cadherin to promote tumor metastasis. Overexpression of dominant‐negative HIF‐1α reversed thrombin‐mediated Twist and Twist‐induced N‐cadherin expression. Moreover, siTwist inhibited Twist‐induced N‐cadherin and Thrombin‐induced cell motility. In conclusion, our study showed that thrombin‐induced HIF‐1α upregulated Twist at the transcriptional level to enhance cell motility. These findings show that thrombin upregulates Twist via HIF‐1α to make tumor cells malignant and also establish a link between the coagulation disorder and cancer metastasis. J. Cell. Physiol. 226: 1060–1068, 2011.

Novel mechanism by which histone deacetylase inhibitors facilitate topoisomerase IIα degradation in hepatocellular carcinoma cells

Histone deacetylase (HDAC) inhibitors exhibit a unique ability to degrade topoisomerase (topo)IIα in hepatocellular carcinoma (HCC) cells, which contrasts with the effect of topoII‐targeted drugs on topoIIβ degradation. This selective degradation might foster novel strategies for HCC treatment in light of the correlation of topoIIα overexpression with the aggressive tumor phenotype and chemoresistance. Here we report a novel pathway by which HDAC inhibitors mediate topoIIα proteolysis in HCC cells. Our data indicate that HDAC inhibitors transcriptionally activated casein kinase (CK)2α expression through increased association of acetylated histone H3 with the CK2α gene promoter. In turn, CK2 facilitated the binding of topoIIα to COP9 signalosome subunit (Csn)5 by way of topoIIα phosphorylation. Furthermore, we identified Fbw7, a Csn5‐interacting F‐box protein, as the E3 ligase that targeted topoIIα for degradation. Moreover, knockdown of CK2α, Csn5, or Fbw7 reversed HDAC inhibitor‐induced topoIIα degradation. Mutational analysis indicates that the 1361SPKLSNKE1368 motif plays a crucial role in regulating topoIIα protein stability. This motif contains the consensus recognition sites for CK2 (SXXE), glycogen synthase kinase (GSK)3β (SXXXS), and Fbw7 (SPXXS). This study also reports the novel finding that topoIIα may be a target of GSK3β phosphorylation. Evidence suggests that CK2 serves as a priming kinase, through phosphorylation at Ser1365, for GSK3β‐mediated phosphorylation at Ser1361. This double phosphorylation facilitated the recruitment of Fbw7 to the phospho‐degron 1361pSPKLpS1365 of topoIIα, leading to its ubiquitin‐dependent degradation. Conclusion: This study shows a novel pathway by which HDAC inhibitors facilitate the selective degradation of topoIIα, which underlies the complexity of the functional role of HDAC in regulating tumorigenesis and aggressive phenotype in HCC cells. (Hepatology 2011;)

α-Tomatine-Mediated Anti-Cancer Activity In Vitro and In Vivo through Cell Cycle- and Caspase-Independent Pathways

α-Tomatine, a tomato glycoalkaloid, has been reported to possess antibiotic properties against human pathogens. However, the mechanism of its action against leukemia remains unclear. In this study, the therapeutic potential of α-tomatine against leukemic cells was evaluated in vitro and in vivo. Cell viability experiments showed that α-tomatine had significant cytotoxic effects on the human leukemia cancer cell lines HL60 and K562, and the cells were found to be in the Annexin V-positive/propidium iodide-negative phase of cell death. In addition, α-tomatine induced both HL60 and K562 cell apoptosis in a cell cycle- and caspase-independent manner. α-Tomatine exposure led to a loss of the mitochrondrial membrane potential, and this finding was consistent with that observed on activation of the Bak and Mcl-1 short form (Mcl-1s) proteins. Exposure to α-tomatine also triggered the release of the apoptosis-inducing factor (AIF) from the mitochondria into the nucleus and down-regulated survivin expression. Furthermore, α-tomatine significantly inhibited HL60 xenograft tumor growth without causing loss of body weight in severe combined immunodeficiency (SCID) mice. Immunohistochemical test showed that the reduced tumor growth in the α-tomatine-treated mice was a result of increased apoptosis, which was associated with increased translocation of AIF in the nucleus and decreased survivin expression ex vivo. These results suggest that α-tomatine may be a candidate for leukemia treatment.

MPT0G066, a novel anti-mitotic drug, induces JNK-independent mitotic arrest, JNK-mediated apoptosis, and potentiates antineoplastic effect of cisplatin in ovarian cancer

Developing new anticancer agents against ovarian cancer is an urgent medical need. MPT0G066, a novel synthetic arylsulfonamide compound, was shown to inhibit cell growth and decrease viability in human ovarian cancer cells. MPT0G066 induced arrest of the cell cycle at the multipolyploidy (MP) phase in SKOV3 and at the G2/M phase in A2780 cells, while increasing the proportion of cells in the subG1. Additionally, MPT0G066 induced c-Jun-NH2 terminal kinase (JNK) activation, influenced cell cycle regulatory and Bcl-2 family proteins, which triggered intrinsic apoptotic pathways through cleavage of caspase-3, -7, -9, and poly-(ADP-ribose) polymerase (PARP). Flow cytometry analysis of p-glycoprotein (p-gp) function showed that MPT0G066 was not a substrate of p-gp. Additionally, it was shown that MPT0G066 could decrease cell viability in multiple-drug-resistant human ovarian cancer cells. Furthermore, the combination of MPT0G066 and cisplatin presented a synergistic cytotoxic effect against ovarian cancer cell lines in vitro. MPT0G066 also significantly suppressed the growth of ovarian carcinoma and potentiated the antineoplastic effects of cisplatin in vivo. In conclusion, these findings indicate that MPT0G066 can be a potential anticancer agent against ovarian cancer that worthy of further development.

Trichlorobenzene-substituted azaaryl compounds as novel FGFR inhibitors exhibiting potent antitumor activity in bladder cancer cells in vitro and in vivo

In the present study, we examined the antitumor activity of a series of trichlorobenzene-substituted azaaryl compounds and identified MPT0L145 as a novel FGFR inhibitor with better selectivity for FGFR1, 2 and 3. It was preferentially effective in FGFR-activated cancer cells, including bladder cancer cell lines expressing FGFR3-TACC3 fusion proteins (RT-112, RT-4). MPT0L145 decreased the phosphorylation of FGFR1, FGFR3 and their downstream proteins (FRS2, ERK and Akt). Mechanistically, cDNA microarray analysis revealed that MPT0L145 decreased genes associated cell cycle progression, and increased genes associated with autophagy pathway. Accordingly, the data revealed that MPT0L145 induced G0/G1 cell cycle arrest and decreased protein levels of cyclin E. Moreover, we provided the evidence that autophagy contributes to FGFR inhibitor-related cell death. Finally, MPT0L145 exhibited comparable antitumor activity to cisplatin with better safety in a RT-112 xenograft model. Taken together, these findings support the utility of MPT0L145 as a novel FGFR inhibitor, providing a strong rationale for further evaluation of this compound as a therapeutic agent for bladder cancers.

Molecular mechanisms underlying the antitumor activity of (E)-N-hydroxy-3-(1-(4-methoxyphenylsulfonyl)-1,2,3,4-tetrahydroquinolin-6-yl)acrylamide in human colorectal cancer cells in vitro and in vivo

Upregulation of class I histone deacetylases (HDAC) correlates with poor prognosis in colorectal cancer (CRC) patients. Previous study revealed that (E)-N-hydroxy-3-(1-(4-methoxyphenylsulfonyl)-1,2,3,4-tetrahydroquinolin-6-yl)acrylamide (Compound 11) is a potent and selective class I HDAC inhibitor, exhibited significant anti-proliferative activity in various human cancer cell lines. In current study, we demonstrated that compound 11 exhibited significant anti-proliferative and cytotoxic activity in CRC cells. Notably, compound 11 was less potent than SAHA in inhibiting HDAC6 as evident from the lower expression of acetyl-α-tubulin, suggesting higher selectivity for class I HDACs. Mechanistically, compound 11 induced cell-cycle arrest at the G2/M phase, activated both intrinsic- and extrinsic-apoptotic pathways, altered the expression of Bcl-2 family proteins and exerted a potent inhibitory effect on survival signals (p-Akt, p-ERK) in CRC cells. Moreover, we provide evidence that compound 11 suppressed motility, decreased mesenchymal markers (N-cadherin and vimentin) and increased epithelial marker (E-cadherin) through down-regulation of Akt. The anti-tumor activity and underlying molecular mechanisms of compound 11 were further confirmed using the HCT116 xenograft model in vivo. Our findings provide evidence of the significant anti-tumor activity of compound 11 in a preclinical model, supporting its potential as a novel therapeutic agent for CRC.

Abstract 4494: MPT0G066, a novel microtubule-destabilizing agent, induces cell apoptosis and potentiates antineoplastic effects of cisplatin in human ovarian cancer cells in vitro and in vivo.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Ovarian cancer is one of the leading causes of death in women with gynecological malignancy in the United States. About 70% of ovarian cancer cases are diagnosed at an advanced stage resulting in poor survival rate. In the present study, we provide the data showing that MPT0G066, a novel synthetic arylsulfonamide compound, inhibited cell growth and viability in human ovarian cancer cell lines as evidenced by sulphorodamine B (SRB) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Cell cycle distribution was also determined by flow cytometry, the data revealed that MPT0G066 induced cell cycle arrest at multipolyploidy (MP) phase (SKOV3 cells) or at G2/M phase (A2780 cells) in 24 hours and ultimately increased the cell population in sub-G1 phase in 48 hours. Moreover, in vitro tubulin polymerization assay, in situ labeling of β-tubulin and western blot analysis showed that MPT0G066, similar to colchicine and vincristine, promoted tubulin depolymerization and altered the expression of G2/M cell cycle regulatory proteins. Mechanistically, MPT0G066 induced JNK activation and altered Bcl-2 family proteins by increasing the expression of p-Bcl-2, Bax, Bim, Puma and decreasing the level of Bcl-2 and Mcl-1. Disruption of mitochondrial proteins triggered intrinsic apoptotic pathways through the cleavage of caspase-3, -7, -9, and poly (ADP-ribose) polymerase (PARP). Moreover, treatment with SP600125, a JNK inhibitor, abolished the effects of MPT0G066 on cell viability, Bcl-2 family proteins and apoptotic cell death. Finally, we used xenograft mouse model to demonstrate that MPT0G066 is able to suppress the growth of ovarian carcinoma A2780 cells and potentiated the antineoplastic effects of cisplatin in vivo. Immunohistochemistry data also confirmed MPT0G066-induced JNK activation in tumor sections. In summary, these results suggested that MPT0G066 could disrupt microtubule dynamics, and lead to cell cycle arrest at MP phase or G2/M phase. MPT0G066 induced JNK activation and altered Bcl-2 family proteins, which ultimately caused apoptosis through the intrinsic apoptotic pathways. These finding indicated that MPT0G066 is a potential anticancer agent worthy for further development and may foster novel treatment for patients with ovarian cancer. Citation Format: Chun-Han Chen, Ya-Chi Li, Li-Hsun Chang, Jing-Ping Liou, Shiow-Lin Pan, Che-Ming Teng. MPT0G066, a novel microtubule-destabilizing agent, induces cell apoptosis and potentiates antineoplastic effects of cisplatin in human ovarian cancer cells in vitro and in vivo . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4494. doi:10.1158/1538-7445.AM2013-4494