Ya Chun Wu

Zhejiang University, Hang-hsien, Zhejiang Sheng, China

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Publications (10)45.44 Total impact

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    ABSTRACT: Colorectal cancer (CRC) is the third most common malignancy and the fourth most frequent cause of cancer deaths worldwide. Ligand-mediated diagnosis and targeted therapy would have vital clinical applications in cancer treatment. In this study, an orthotopic model of colorectal cancer was established in mice. In vivo phage library selection was then utilized to isolate peptides specifically recognizing the vasculature of colorectal cancer tissues. A phage (termed TCP-1 phage) was isolated by this manner and it homed to the colorectal cancer tissues by 11- to 94-fold more than other organs. Chemical synthetic peptide (CTPSPFSHC, termed TCP-1) displayed by TCP-1 phage inhibited the homing ability of the phage to the tumor mass when co-injected intravenously with the TCP-1 phage into mice with colon cancer. Meanwhile, immunostaining analysis indicated that TCP-1 phage and peptide localized in the vasculature of the colorectal cancer tissue, but not of normal tissues. Moreover, TCP-1 peptide bound to blood vessels of surgical tissue samples of human colorectal cancer. After intravenous injection of FITC-labeled TCP-1 into the tumor-bearing mice for 20h, there was a strong fluorescent signal in the tumors but not other tissues when observed under blue light. In addition, TCP-1 conjugated with a pro-apoptotic peptide specifically induced apoptosis of tumor-associated blood vessels in vivo. The data define a novel peptide TCP-1 as an effective agent for imaging detection and drug delivery for colorectal cancer.
    Journal of Controlled Release 12/2010; 148(3):292-302. DOI:10.1016/j.jconrel.2010.09.015 · 7.26 Impact Factor
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    ABSTRACT: The ubiquitin-proteasome system and macroautophagy are two complementary pathways for protein degradation. Emerging evidence suggests that proteasome inhibition might be a promising approach for the treatment of cancer. In this study, we show that proteasome inhibitor MG-132 suppressed gastric cancer cell proliferation and induced macroautophagy. The induction of macroautophagy was evidenced by the formation of LC3(+) autophagosomes and the accumulation of acidic vesicular organelles and autolysosomes and was accompanied by the suppression of mammalian target of rapamycin complex 1 activity. Abolition of macroautophagy by knockdown of Class III phosphatidylinositol-3 kinase Vps34 or ATG5/7 sensitized gastric cancer cells to the antiproliferative effect of MG-132 by promoting G(2)/M cell cycle arrest. In addition, MG-132 increased ERK phosphorylation whose inhibition by MEK inhibitor significantly enhanced the antiproliferative effect of proteasome inhibition. To conclude, this study demonstrates that macroautophagy and ERK phosphorylation serve as protective mechanisms to counteract the antiproliferative effect of proteasome inhibition. This discovery may have implications for the application of proteasome-directed therapy for the treatment of cancer.
    Autophagy 02/2010; 6(2):228-38. DOI:10.1016/S0016-5085(10)62033-1 · 11.42 Impact Factor
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    ABSTRACT: Overexpression of cyclooxygenase-2 (COX-2) and elevation of its derivative prostaglandin E(2) (PGE(2)) are implicated in human esophageal squamous cell carcinoma. The expression of c-Myc, an oncogenic transcription factor, is also upregulated in this malignant disease. This study sought to elucidate whether a functional connection exists between COX-2/PGE(2) and c-Myc in esophageal squamous cell carcinoma. Results showed that PGE(2) substantially increased the proliferation of cultured esophageal squamous cell carcinoma cells. In this regard, PGE(2) substantially increased the mRNA and protein expression of c-Myc and its association with the binding partner Max. Knockdown of c-Myc by RNA interference also significantly attenuated PGE(2)-induced cell proliferation. Further, mechanistic study revealed that PGE(2) increased the protein stability and nuclear accumulation of c-Myc via phosphorylation on serine 62 in an extracellular signal regulated kinase (ERK)-dependent manner. To this end, ERK activation by PGE(2) was completely abolished by protein kinase C (PKC) inhibitors. Moreover, the effect of PGE(2) on c-Myc expression was mimicked by EP2 receptor agonist. In addition, knockdown of EP2 receptor by EP2 siRNA attenuated PGE(2)-induced c-Myc expression. Collectively, our findings suggest that PGE(2) upregulates c-Myc via the EP2/PKC/ERK pathway. This study sheds new light on the carcinogenic mechanism of PGE(2) in esophageal squamous cell carcinoma.
    International Journal of Cancer 12/2009; 125(11):2540-6. DOI:10.1002/ijc.24607 · 5.01 Impact Factor
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    ABSTRACT: Resveratrol, a naturally occurring polyphenolic antioxidant, is a compound holding promise for cancer chemoprevention. Previous studies suggest that 2,3',4,5'-tetramethoxy-trans-stilbene (TMS) and 3,4,4',5,-tetramethoxy-trans-stilbene (MR-4), both of which are derivatives of resveratrol, are potent apoptosis-inducing agents with clinical potential. In this study, we chemically synthesized 2,3',4,4',5'-pentamethoxy-trans-stilbene (PMS), the hybrid molecule of TMS and MR-4, and determined its effects on colon cancer growth. When compared with its parent compounds, PMS displayed more potent in vitro anti-mitogenic effect on colon cancer cells (Caco-2, HT-29 and SW1116). Moreover, PMS inhibited tumor growth in vivo in a colon cancer xenograft model. In this connection, PMS strongly induced apoptosis in HT-29 cells as evidenced by increased PARP cleavage, DNA fragmentation, and accumulation of sub-G(1) population. Further mechanistic analysis revealed that PMS enhanced the polymerization of microtubules, which was followed by G(2)/M mitotic arrest and caspase-dependent apoptosis. The activation of caspases-3, -7, -8, and -9 was involved in PMS-induced apoptosis with concomitant down-regulation of the pro-survival PI3K/Akt signaling. Collectively, these data suggest that PMS is a potent inducer of apoptosis via targeting microtubules and may merit investigation as a potential chemoprophylactic and therapeutic agent for colon cancer.
    Biochemical pharmacology 08/2009; 78(9):1224-32. DOI:10.1016/j.bcp.2009.06.109 · 4.65 Impact Factor
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    ABSTRACT: Protein homeostasis relies on a balance between protein synthesis and protein degradation. The ubiquitin-proteasome system is a major catabolic pathway for protein degradation. In this respect, proteasome inhibition has been used therapeutically for the treatment of cancer. Whether inhibition of protein degradation by proteasome inhibitor can repress protein translation via a negative feedback mechanism, however, is unknown. In this study, proteasome inhibitor MG-132 lowered the proliferation of colon cancer cells HT-29 and SW1116. In this connection, MG-132 reduced the phosphorylation of mammalian target of rapamycin (mTOR) at Ser2448 and Ser2481 and the phosphorylation of its downstream targets 4E-BP1 and p70/p85 S6 kinases. Further analysis revealed that MG-132 inhibited protein translation as evidenced by the reductions of (35)S-methionine incorporation and polysomes/80S ratio. Knockdown of raptor, a structural component of mTOR complex 1, mimicked the anti-proliferative effect of MG-132. To conclude, we demonstrate that the inhibition of protein degradation by proteasome inhibitor represses mTOR signaling and protein translation in colon cancer cells.
    Biochemical and Biophysical Research Communications 07/2009; 386(4):598-601. DOI:10.1016/j.bbrc.2009.06.080 · 2.28 Impact Factor
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    ABSTRACT: Macroautophagy is a process by which cytoplasmic content and organelles are sequestered by double-membrane bound vesicles and subsequently delivered to lysosomes for degradation. Macroautophagy serves as a major intracellular pathway for protein degradation and as a pro-survival mechanism in time of stress by generating nutrients. In the present study, bafilomycin A(1), a vacuolar type H(+)-ATPase inhibitor, suppresses macroautophagy by preventing acidification of lysosomes in colon cancer cells. Diminished macroautophagy was evidenced by the accumulation of undegraded LC3 protein. Suppression of macroautophagy by bafilomycin A(1) induced G(0)/G(1) cell cycle arrest and apoptosis which were accompanied by the down-regulation of cyclin D(1) and cyclin E, the up-regulation of p21(Cip1) as well as cleavages of caspases-3, -7, -8, and -9 and PARP. Further investigation revealed that bafilomycin A(1) increased the phosphorylation of ERK, JNK, and p38. In this regard, p38 inhibitor partially reversed the anti-proliferative effect of bafilomycin A(1). To conclude, inhibition of macroautophagy by bafilomycin A(1) lowers G(1)-S transition and induces apoptosis in colon cancer cells. Our results not only indicate that inhibitors of macroautophagy may be used therapeutically to inhibit cancer growth, but also delineate the relationship between macroautophagy and apoptosis.
    Biochemical and Biophysical Research Communications 06/2009; 382(2):451-6. DOI:10.1016/j.bbrc.2009.03.051 · 2.28 Impact Factor
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    ABSTRACT: Evolving evidence supports that cyclooxygenase-1 (COX-1) takes part in colon carcinogenesis. The effects of COX-1 inhibition on colon cancer cells, however, remains obscured. In this study, we demonstrate that COX-1 inhibitor sc-560 inhibited colon cancer cell proliferation with concomitant G(0)/G(1)-phase cell cycle arrest. The anti-proliferative effect was associated with down-regulation of c-Fos, cyclin E(2) and E(2)F-1 and up-regulation of p21(Waf1/Cip1) and p27(Kip1). In addition, sc-560 induced macroautophagy, an emerging mechanism of tumor suppression, as evidenced by the formation of LC3(+) autophagic vacuoles, enhanced LC3 processing, and the accumulation of acidic vesicular organelles and autolysosomes. In this connection, 3-methyladenine, a Class III phosphoinositide 3-kinase inhibitor, significantly abolished the formation of LC3(+) autophagic vacuoles and the processing of LC3 induced by sc-560. To conclude, this study reveals the unreported relationship between COX-1 and proliferation/macroautophagy of colon cancer cells.
    Biochemical and Biophysical Research Communications 05/2009; 382(1):79-84. DOI:10.1016/j.bbrc.2009.02.140 · 2.28 Impact Factor
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    ABSTRACT: Doxorubicin is a chemotherapeutic drug widely used for the treatment of advanced esophageal squamous cell carcinoma. However, its efficacy is usually limited by the development of multidrug resistance (MDR), which has been linked to the up-regulation of P-glycoprotein (P-gp) in cancer cells. Conventional nonsteroidal anti-inflammatory drugs and cyclooxygenase 2 (COX-2)-selective inhibitors have been demonstrated to overcome MDR in some cancer cells. Here we sought to elucidate the effect of COX inhibitors on doxorubicin-induced cytotoxicity in relation to P-gp function in human esophageal squamous cell carcinoma cells. Among the five tested COX inhibitors [indomethacin, 4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-benzenesulfonamide (SC236), 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluorom-ethylpyrazole (SC560), nimesulide, and N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide (NS398)], all of which substantially suppressed prostaglandin E(2) (PGE(2)) production to a similar extent, only the nonselective COX inhibitor indomethacin and the COX-2-selective inhibitor SC236 enhanced cytotoxic effects of doxorubicin on HKESC-1 and HKESC-2 cells. Moreover, these effects could not be reversed by the addition of PGE(2). Knockdown of COX-2 by small interference RNA also failed to mimic the enhancing effects of indomethacin or SC236, implicating that their action is COX- and PGE(2)-independent. To this end, we observed that indomethacin and SC236 directly functioned as noncompetitive inhibitors of P-gp, which were manifested as a reduction of P-gp ATPase activity. Collectively, these findings suggest that the direct inhibitory effects of indomethacin and SC236 on P-gp may contribute to their ability to increase the intracellular retention of doxorubicin and thus enhance its cytotoxicity. The combination of indomethacin or SC236 with doxorubicin may have significant potential clinical application, especially in the circumvention of P-gp-mediated MDR in cancer cells.
    Molecular pharmacology 04/2009; 75(6):1364-73. DOI:10.1124/mol.108.053546 · 4.12 Impact Factor
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    ABSTRACT: The ubiquitin-proteasome system (UPS) and lysosome-dependent macroautophagy (autophagy) are two major intracellular pathways for protein degradation. Blockade of UPS by proteasome inhibitors has been shown to activate autophagy. Recent evidence also suggests that proteasome inhibitors may inhibit cancer growth. In this study, the effect of a proteasome inhibitor MG-132 on the proliferation and autophagy of cultured colon cancer cells (HT-29) was elucidated. Results showed that MG-132 inhibited HT-29 cell proliferation and induced G(2)/M cell cycle arrest which was associated with the formation of LC3(+) autophagic vacuoles and the accumulation of acidic vesicular organelles. MG-132 also increased the protein expression of LC3-I and -II in a time-dependent manner. In this connection, 3-methyladenine, a Class III phosphoinositide 3-kinase inhibitor, significantly abolished the formation of LC3(+) autophagic vacuoles and the expression of LC3-II but not LC3-I induced by MG-132. Taken together, this study demonstrates that inhibition of proteasome in colon cancer cells lowers cell proliferation and activates autophagy. This discovery may shed a new light on the novel function of proteasome in the regulation of autophagy and proliferation in colon cancer cells.
    Biochemical and Biophysical Research Communications 09/2008; 374(2):258-63. DOI:10.1016/j.bbrc.2008.07.031 · 2.28 Impact Factor
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    ABSTRACT: The use of nonsteroidal anti-inflammatory drugs is associated with a lower risk for esophageal squamous cell carcinoma, in which overexpression of cyclooxygenase-2 (COX-2) is frequently reported. Prostaglandin E(2) (PGE(2)), a COX-2-derived eicosanoid, is implicated in the promotion of cancer growth. However, the precise role of PGE(2) in the disease development of esophageal squamous cell carcinoma remains elusive. In this study, we investigated the effect of PGE(2) on the proliferation of cultured esophageal squamous cell carcinoma cells (HKESC-1). Results showed that HKESC-1 cells expressed all four series of prostaglandin (EP) receptors, namely, EP1 to EP4 receptors. In this regard, PGE(2) and the EP2 receptor agonist (+/-)-15-deoxy-16S-hydroxy-17-cyclobutyl PGE(1) methyl ester (butaprost) markedly increased HKESC-1 cell proliferation. Moreover, the mitogenic effect of PGE(2) was significantly attenuated by RNA interference-mediated knockdown of the EP2 receptor, indicating that this receptor mediated the mitogenic effect of PGE(2). In this connection, PGE(2) and butaprost induced phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2), whose down-regulation by RNA interference significantly attenuated PGE(2)-induced cell proliferation. In addition, PGE(2) and butaprost increased c-Fos expression and activator protein 1 (AP-1) transcriptional activity, which were abolished by the mitogen-activated protein kinase/Erk kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)-butadiene ethanolate (U0126). AP-1-binding inhibitor curcumin also partially reversed the mitogenic effect of PGE(2). Taken together, these data demonstrate for the first time that the EP2 receptor mediates the mitogenic effect of PGE(2) in esophageal squamous cell carcinoma via activation of the Erk/AP-1 pathway. This study supports the growth-promoting action of PGE(2) in esophageal squamous cell carcinoma and the potential application of EP2 receptor antagonists in the treatment of this disease.
    Journal of Pharmacology and Experimental Therapeutics 07/2008; 327(1):258-67. DOI:10.1124/jpet.108.141275 · 3.86 Impact Factor