Multiple Effects of a Novel Epothilone Analog on Cellular Processes and Signaling Pathways Regulated by Rac1 GTPase in the Human Breast Cancer Cells

Rongguo Qiu,Li Tang 대한약리학회 2014 The Korean Journal of Physiology & Pharmacology Vol.18 No.2

The epothilones are a class of microtubule inhibitors that exhibit a strong antitumor activity. UTD2is a novel epothilone analog generated by genetic manipulation of the polyketide biosynthetic genecluster. This study investigated the effects of UTD2 on the actin cytoskeleton and its critical regulators,and the signaling pathways which are essential for cell motility, growth and survival in MCF-7 breastcancer cells. Results showed that UTD2 inhibited the cellular functions of actin cytoskeleton, suchas wound-closure, migration and invasion, as well as adhesion. Our study further demonstrated thatUTD2 suppressed Rac1 GTPase activation and reduced the activity of PAK1, which is a downstreameffector of Rac1, while the activity of Cdc42 was not affected. Additionally, the phosphorylation of p38and ERK were significantly inhibited, but the phosphorylation of JNK remained the same after UTD2treatment. Moreover, UTD2 inhibited the activity and mRNA expression of MMP-2, which plays akey role in cell motility. UTD2 also reduced the phosphorylation of Akt, which is an important signalingkinase regulating the cell survival through Rac1. Furthermore, UTD2 interrupted the synergy betweenRac1 and Raf in focus formation assays. Taken together, these results indicated that UTD2 exertedmultiple effects on the actin cytoskeleton and signaling pathways associated with Rac1. This studyprovided novel insights into the molecular mechanism of the antineoplastic and antimetastaticactivities of epothilones. Our findings also suggest that the signaling pathways regulated by Rac1 maybe evaluated as biomarkers for the response to therapy in clinical trials of epothilones.

Multiple Effects of a Novel Epothilone Analog on Cellular Processes and Signaling Pathways Regulated by Rac1 GTPase in the Human Breast Cancer Cells

Zhang, Hong,An, Fan,Tang, Li,Qiu, Rongguo The Korean Society of Pharmacology 2014 The Korean Journal of Physiology & Pharmacology Vol.18 No.2

The epothilones are a class of microtubule inhibitors that exhibit a strong antitumor activity. UTD2 is a novel epothilone analog generated by genetic manipulation of the polyketide biosynthetic gene cluster. This study investigated the effects of UTD2 on the actin cytoskeleton and its critical regulators, and the signaling pathways which are essential for cell motility, growth and survival in MCF-7 breast cancer cells. Results showed that UTD2 inhibited the cellular functions of actin cytoskeleton, such as wound-closure, migration and invasion, as well as adhesion. Our study further demonstrated that UTD2 suppressed Rac1 GTPase activation and reduced the activity of PAK1, which is a downstream effector of Rac1, while the activity of Cdc42 was not affected. Additionally, the phosphorylation of p38 and ERK were significantly inhibited, but the phosphorylation of JNK remained the same after UTD2 treatment. Moreover, UTD2 inhibited the activity and mRNA expression of MMP-2, which plays a key role in cell motility. UTD2 also reduced the phosphorylation of Akt, which is an important signaling kinase regulating the cell survival through Rac1. Furthermore, UTD2 interrupted the synergy between Rac1 and Raf in focus formation assays. Taken together, these results indicated that UTD2 exerted multiple effects on the actin cytoskeleton and signaling pathways associated with Rac1. This study provided novel insights into the molecular mechanism of the antineoplastic and antimetastatic activities of epothilones. Our findings also suggest that the signaling pathways regulated by Rac1 may be evaluated as biomarkers for the response to therapy in clinical trials of epothilones.

Differential Effects of Tautomycetin and Its Derivatives on Protein Phosphatase Inhibition, Immunosuppressive Function and Antitumor Activity

Mingshan Niu,Yan Sun,Bo Liu,Li Tang,Rongguo Qiu 대한약리학회 2012 The Korean Journal of Physiology & Pharmacology Vol.16 No.2

In the present work, we studied the structure-activity relationship (SAR) of tautomycetin (TMC) and its derivatives. Further, we demonstrated the correlation between the immunosuppressive fuction, anticancer activity and protein phosphatase type 1 (PP1) inhibition of TMC and its derivatives. We have prepared some TMC derivatives via combinatorial biosynthesis, isolation from fermentation broth or chemical degradation of TMC. We found that the immunosuppressive activity was correlated with anticancer activity for TMC and its analog compounds, indicating that TMC may home at the same targets for its immunosuppressive and anticancer activities. Interestingly, TMC-F1, TMC-D1 and TMC-D2 all retained significant, albeit reduced PP1 inhibitory activity compared to TMC. However, only TMC-D2 showed immunosuppressive and anticancer activities in studies carried out in cell lines. Moreover, TMC-Chain did not show any significant inhibitory activity towards PP1 but showed strong growth inhibitory effect. This observation implicates that the maleic anhydride moiety of TMC is critical for its phosphatase inhibitory activity whereas the C1-C18 moiety of TMC is essential for the inhibition of tumor cell proliferation. Furthermore, we measured in vivo phosphatase activities of PP1 in MCF-7 cell extracts treated with TMC and its related compounds, and the results indicate that the cytotoxicity of TMC doesn’t correlate with its in vivo PP1 inhibition activity. Taken together, our study suggests that the immunosuppressive and anticancer activities of TMC are not due to the inhibition of PP1. Our results provide a novel insight for the elucidation of the underlying molecular mechanisms of TMC’s important biological functions.

Differential Effects of Tautomycetin and Its Derivatives on Protein Phosphatase Inhibition, Immunosuppressive Function and Antitumor Activity

Niu, Mingshan,Sun, Yan,Liu, Bo,Tang, Li,Qiu, Rongguo The Korean Society of Pharmacology 2012 The Korean Journal of Physiology & Pharmacology Vol.16 No.2

In the present work, we studied the structure-activity relationship (SAR) of tautomycetin (TMC) and its derivatives. Further, we demonstrated the correlation between the immunosuppressive fuction, anticancer activity and protein phosphatase type 1 (PP1) inhibition of TMC and its derivatives. We have prepared some TMC derivatives via combinatorial biosynthesis, isolation from fermentation broth or chemical degradation of TMC. We found that the immunosuppressive activity was correlated with anticancer activity for TMC and its analog compounds, indicating that TMC may home at the same targets for its immunosuppressive and anticancer activities. Interestingly, TMC-F1, TMC-D1 and TMC-D2 all retained significant, albeit reduced PP1 inhibitory activity compared to TMC. However, only TMC-D2 showed immunosuppressive and anticancer activities in studies carried out in cell lines. Moreover, TMC-Chain did not show any significant inhibitory activity towards PP1 but showed strong growth inhibitory effect. This observation implicates that the maleic anhydride moiety of TMC is critical for its phosphatase inhibitory activity whereas the C1-C18 moiety of TMC is essential for the inhibition of tumor cell proliferation. Furthermore, we measured $in$ $vivo$ phosphatase activities of PP1 in MCF-7 cell extracts treated with TMC and its related compounds, and the results indicate that the cytotoxicity of TMC doesn't correlate with its $in$ $vivo$ PP1 inhibition activity. Taken together, our study suggests that the immunosuppressive and anticancer activities of TMC are not due to the inhibition of PP1. Our results provide a novel insight for the elucidation of the underlying molecular mechanisms of TMC's important biological functions.

Functional Characterization of the Genes tauO, tauK, and tauI in the Biosynthesis of Tautomycetin

Fen Wang,Rixiang Kong,Bo Liu,Jing Zhao,Rongguo Qiu,Li Tang 한국미생물학회 2012 The journal of microbiology Vol.50 No.5

Tautomycetin is a specific protein phosphatase I inhibitor. In an effort to elucidate the biosynthetic mechanism of tautomycetin,we inactivated genes of the tautomycetin biosynthetic gene cluster, tauI, tauO, and tauK, which encode for putative P450 oxidase, citryl-CoA lyase, and esterase enzymes,respectively. The mutant STQ0606 (ΔtauO) did not produce any detectable amount of tautomycetin intermediates but could convert dialkylmaleic anhydride to tautomycetin,strongly indicating that TauO was involved in dialkylmaleic anhydride biosynthesis. STQ1211 (ΔtauK) accumulated dialkylmaleic anhydride, whereas the cofermentation of STQ1211(ΔtauK) and STQ0606 (ΔtauO) restored the production of tautomycetin. Together, these results suggest that TauK was responsible for the conjugation of dialkylmaleic anhydride and the polyketide moiety in tautomycetin biosynthesis. The disruption of tauI resulted in the accumulation of 5-des-ketotautomycetin,revealing that TauI was responsible for the oxidation at C5 as the last step. Although the shunt pathways were involved in the biosynthesis of tautomycetin, the main post-polyketide synthase tailoring steps were dehydration,decarboxylation and oxidation, taking place consecutively. This study allowed us to predict the biosynthesis of tautomycetin more accurately and provided novel insights into the mechanism of the biosynthesis of tautomycetin.