Zihao Qi

Aurora-A controls cancer cell radio- and chemoresistance via ATM/Chk2-mediated DNA repair networks

High expression of Aurora kinase A (Aurora-A) has been found to confer cancer cell radio- and chemoresistance, however, the underlying mechanism is unclear. In this study, by using Aurora-A cDNA/shRNA or the specific inhibitor VX680, we show that Aurora-A upregulates cell proliferation, cell cycle progression, and anchorage-independent growth to enhance cell resistance to cisplatin and X-ray irradiation through dysregulation of DNA damage repair networks. Mechanistic studies showed that Aurora-A promoted the expression of ATM/Chk2, but suppressed the expression of BRCA1/2, ATR/Chk1, p53, pp53 (Ser15), H2AX, γH2AX (Ser319), and RAD51. Aurora-A inhibited the focus formation of γH2AX in response to ionizing irradiation. Treatment of cells overexpressing Aurora-A and ATM/Chk2 with the ATM specific inhibitor KU-55933 increased the cell sensitivity to cisplatin and irradiation through increasing the phosphorylation of p53 at Ser15 and inhibiting the expression of Chk2, γH2AX (Ser319), and RAD51. Further study revealed that BRCA1/2 counteracted the function of Aurora-A to suppress the expression of ATM/Chk2, but to activate the expression of ATR/Chk1, pp53, γH2AX, and RAD51, leading to the enhanced cell sensitivity to irradiation and cisplatin, which was also supported by the results from animal assays. Thus, our data provide strong evidences that Aurora-A and BRCA1/2 inversely control the sensitivity of cancer cells to radio- and chemotherapy through the ATM/Chk2-mediated DNA repair networks, indicating that the DNA repair molecules including ATM/Chk2 may be considered for the targeted therapy against cancers with overexpression of Aurora-A.

RY-2f, an isoflavone analog, overcomes cisplatin resistance to inhibit ovarian tumorigenesis via targeting the PI3K/AKT/mTOR signaling pathway

Ovarian cancer remains the leading cause of death in gynecologic malignancies partially because of resistance to chemotherapy. In the present study, we show that RY-2f, a chemically synthesized isoflavone analog, inhibited ovarian cancer cell proliferation, blocked cell cycle in G2/M phase and induced cellular apoptosis through up-regulation of p21, cyclin B1, Bax, Bad and cleaved-PARP, and suppression of cyclin A, CDK2 and Bcl-2. We also show that RY-2f could increase the chemotherapeutic efficacy of cisplatin as tested by cell proliferation and colony formation assays, indicating a synergistic effect of RY-2f and cisplatin. Mechanistic study revealed that RY-2f exerted the anti-tumor activities mainly through suppression of the PI3K/AKT/mTOR signaling. Finally, in vivo studies showed that RY-2f blocked the A2780-induced xenograft tumor growth without detectable toxicity in the animals at the therapeutic doses, and whereas RY-2f re-sensitized the cisplatin resistant cell line A2780/CDDP induced xenograft tumor to cisplatin treatment. Thus, RY-2f may be developed as a potential therapeutic agent to treat ovarian cancer.

Small Ribosomal Protein Subunit S7 Suppresses Ovarian Tumorigenesis through Regulation of the PI3K/AKT and MAPK Pathways

Small ribosomal protein subunit S7 (RPS7) has been reported to be associated with various malignancies, but the role of RPS7 in ovarian cancer remains unclear. In this study, we found that silencing of RPS7 by a specific shRNA promoted ovarian cancer cell proliferation, accelerated cell cycle progression, and slightly reduced cell apoptosis and response to cisplatin treatment. Knockdown of RPS7 resulted in increased expression of P85α, P110α, and AKT2. Although the basal levels of ERK1/2, MEK1/2, and P38 were inconsistently altered in ovarian cancer cells, the phosphorylated forms of MEK1/2 (Ser217/221), ERK1/2 (Thr202/Tyr204), JNK1/2 (Thr183/Tyr185), and P38 (Thr180/Tyr182) were consistently reduced after RPS7 was silenced. Both the in vitro anchorage-independent colony formation and in vivo animal tumor formation capability of cells were enhanced after RPS7 was depleted. We also showed that silencing of RPS7 enhanced ovarian cancer cell migration and invasion. In sum, our results suggest that RPS7 suppresses ovarian tumorigenesis and metastasis through PI3K/AKT and MAPK signal pathways. Thus, RPS7 may be used as a potential marker for diagnosis and treatment of ovarian cancer.

Aurora-A: a potential DNA repair modulator

It is well-known that overexpression of Aurora-A promotes tumorigenesis, but the role of Aurora-A in the development of cancer has not been fully investigated. Recent studies indicate that Aurora-A may confer cancer cell chemo- and radioresistance through dysregulation of cell cycle progression and DNA damage response. Direct evidences from literatures suggest that Aurora-A inhibits pRb, p53, p21waf1/cip1, and p27cip/kip but enhances Plk1, CDC25, CDK1, and cyclin B1 to repeal cell cycle checkpoints and to promote cell cycle progression. Other studies indicate that Aurora-A suppresses BRCA1, BRCA2, RAD51, poly(ADP ribose) polymerase (PARP), and gamma-H2AX to dysregulate DNA damage response. Aurora-A may also interact with RAS and Myc to control DNA repair indirectly. In this review, we summarized the potential role of Aurora-A in DNA repair from the current literatures and concluded that Aurora-A may function as a DNA repair modulator to control cancer cell radio- and chemosensitivity, and that Aurora-A-associated DNA repair molecules may be considered for targeted cancer therapy.

The negative interplay between Aurora A/B and BRCA1/2 controls cancer cell growth and tumorigenesis via distinct regulation of cell cycle progression, cytokinesis, and tetraploidy

It is well known that the activation of Aurora A/B (Aur A/B) or inactivation of BRCA1/2 induces tumor formation. Others and we have reported that the mutual suppression between Aur A/B and BRCA1/2 may manipulate cancer cell growth and tumorigenesis, however, the interactive regulation and mechanism between these molecules are still elusive. In this study, by consecutive silencing of Aur A/B or/and BRCA1/2 with specific shRNAs, we showed that, in BRCA2-deficient pancreatic cancer cell line Capan-1 and in ovarian cancer cell line OVCA433, Aur A/B and BRCA1/2 inversely regulated the expression of each other likely through proteasome-mediated proteolysis but not through gene transcription. Aur A/B and BRCA1/2 conversely regulated cell cycle progression mainly through control of p53 and cyclin A. Moreover, the disruption of Aur A/B blocked abnormal cytokinesis and decreased cell multinuclearity and chromosome tetraploidy, whereas the deprivation of BRCA1/2 promoted the abnormal cytokinesis and enhanced the cell multinuclearity and tetraploidy. Furthermore, we showed by animal assays that the depletion of Aur A/B inhibited tumor growth of both cell lines, while the knockdown of BRCA1/2 promoted the tumor growth. However, the concurrent silencing of Aur A/B and BRCA1/2 diminished the effects of these molecules on the regulation of cell cycle, cytokinesis, and tetraploidy, leading to the burdened tumor sizes similar to those induced by scrambled shRNA-treated control cells. In summary, our study revealed that the negative interplay between Aur A/B and BRCA1/2 inversely controls the cell proliferation, cell cycle progression, cell multinuclearity, and tetraploidization to modulate tumorigenesis.

Wip1 suppresses ovarian cancer metastasis through the ATM/AKT/Snail mediated signaling

Inactivation of p53 greatly contributes to serous ovarian cancer, while the role of the wild-type p53 induced phosphatase 1 (Wip1) is quite unclear. In this study, by silencing or overexpression of Wip1, we found that Wip1 suppressed ovarian cancer cell invasion, migration, epithelial to mesenchymal transition (EMT), and ovarian cancer metastasis in xenograft animal models. Mechanistic studies showed that Wip1 may block ovarian cancer metastasis through inhibition of Snail and p-Akt expression because silencing or overexpression of Wip1 either upregulated or downregulated the expression of Snail and p-Akt (Ser 473), while further knockdown of Snail by shRNA or inhibition of p-Akt by a chemical compound attenuated cell invasion, migration and EMT in Wip1 silencing cells. We also found that the phosphorylation of Akt at Ser 473 might be mediated through p-ATM (Ser 1981). Thus, Wip1 may suppress ovarian cancer metastasis through negative regulation of p-ATM, p-Akt, and Snail, which was also evidenced in the limited clinical specimens. Therefore, our data may provide a novel therapeutic indication for serous ovarian cancer based on the uncovered mechanism associated with the precise function of Wip1 independent of p53.

Tetramethoxychalcone, a chalcone derivative, suppresses proliferation, blocks cell cycle progression, and induces apoptosis of human ovarian cancer cells.

In the present study, we investigated the in vitro antitumor functions of a synthetic chalcone derivative 4,3′,4′,5′- tetramethoxychalcone (TMOC) in ovarian cancer cells. We found that TMOC inhibited the proliferation and colony formation of cisplatin sensitive cell line A2780 and resistant cell line A2780/CDDP, as well as ovarian cancer cell line SKOV3 in a time- and dose-dependent manner. Treatment of A2780 cells with TMOC resulted in G0/G1 cell cycle arrest through the down-regulation of cyclin D1 and CDK4, and the up-regulation of p16, p21 and p27 proteins. We demonstrated that TMOC might induce cell apoptosis through suppressing Bcl-2 and Bcl-xL, but enhancing the expression of Bax and the cleavage of PARP-1. Treatment of TMOC also reduced the invasion and migration of A2780 cells. Finally, we found that TMOC inhibited the constitutive activation of STAT3 signaling pathway and induced the expression of the tumor suppressor PTEN regardless of the p53 status in cell lines. These data suggest that TMOC may be developed as a potential chemotherapeutic agent to effectively treat certain cancers including ovarian cancer.

Abstract 1605: Aurora-A promotes radio- and chemo- resistance through regulation of DNA damage response proteins.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Background: Poor prognosis of cancer is usually resulted from radio- and chemo-resistance. Aurora-A, a serine/threonine kinase, associated with spindle separation and centrosome duplication, is overexpressed in many cancers. Purposes: High expression of Aurora-A negatively regulates BRCA2, indicating that Aurora-A is probably associated with DNA damage repair, which may mediate resistance of radio- and chemo-therapy. This study was to investigate the role of Aurora-A in radio- and chemo-resistance in order to seek novel therapeutic methods for human cancer. Materials and methods: Cell lines from breast cancer, pancreatic cancer and ovarian cancer, including those with either low Aurora-A expression (MCF-7, PANC-1 and OVCA420), or high Aurora-A expression (MDA-MB-231, BXPC3 and OVCA429), were used to overexpress or silence Aurora-A, BRCA1, or BRCA2. Cell growth curve and colony formation were tested by cell counting and soft agar assay. Flow cytometry and MTT were used to examine cell apoptosis or cell viability (IC50) after treatment with radiation and cisplatin or VX680 (Aurora-A inhibitor). Western blotting was used to test the expression of DNA damage responsive proteins. Immunofluorescence was used to detect intracellular localization of above proteins. Results: Our data showed that introduction of Aurora-A or silencing of BRCA1 and BRCA2 increased cell growth and colony formation, while silencing of Aurora-A or introduction of BRCA1 and BRCA2 decreased cell proliferation and colony formation. Introduction of Aurora-A also reduced apoptosis in response to gamma-irradiation and cisplatin treatment, while silencing of Aurora-A or treatment of cells with VX680 enhanced apoptosis. Introduction of Aurora-A increased cell viability and IC50 in response to cisplatin treatment, while knockdown of Aurora-A or treatment with VX680 decreased cell viability and IC50. Western blot suggested that Aurora-A had a negative association with BRCA1 and BRCA2. Moreover, overexpression of Aurora-A either by introduction of Aurora-A cDNA or knockdown of BRCA1 or BRCA2 attenuated the expression of DNA damage responsive proteins including RAD51, H2AX, γH2AX, ATR, ERCC2, Chk1, pChk1, Chk2, pChk2,p53, pp53, DNApolζ, which was confirmed by Immunofluorescence. Conclusions: Aurora-A regulates DNA damage responsive proteins including BRCA1, BRCA2, RAD51, H2AX, ERCC2, Chk1, Chk2, ATR, DNA pol ζ to confer cancer radio- and chemo-resistance. Therefore, DNA damage pathway should be essentially considered in the targeted therapy against Aurora-A in cancer patients either with activated Aurora-A or with inactivated BRCA1 or BRCA2. Citation Format: Huizhen Sun, Ziliang Wang, Jiao Meng, Yan Wang, Zihao Qi, Han Xu, Fengjuan Lin, Wen Gao, Jianmin Sun, Jing Hou, Gong Yang. Aurora-A promotes radio- and chemo- resistance through regulation of DNA damage response proteins. [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 1605. doi:10.1158/1538-7445.AM2013-1605 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract 548: CXCR2 controls breast cancer metastasis and chemoresistance through PI3K/AKT and COX-2 signalings.

Background: Breast cancer is the chief culprit leading to woman9s death. The major cause is the chemoresistance and distant metastasis before or after surgery and standard treatment. Recent studies suggest that chemokines and their receptors may play important roles in breast cancer metastasis and chemoresistance. Purpose: The chemokine receptor CXCR2 is associated with tumor development in many cancers. Although IL-8 and Gro-alpha as the major ligands contribute to breast cancer progression, the function of their receptor CXCR2 in breast cancer is elusive. In this study, we investigated the role of CXCR2 in breast cancer metastasis and chemoresistance. Experimental design:Human breast cancer cell lines including MCF-7 and SKBR-3 (low metastasis), MDA-MB-231 (medium metastasis), MDA-MB-231HM (high lung metastasis), MDA-MB-231BO (high bone metastasis), and MDA-MB-231/Gem (Gemcitabine-resistant) were used to investigate cell proliferation, migration, invasion, colony formation, apoptosis, and tumorigenesis by MTT, scratch-wound, transwell, soft agar, flow cytometery, and animal assays after CXCR2 or its associated proteins were over expressed or silenced/inhibited. Protein expression in cell lines and tissues was examined by either Western blot, ELISA, immunofluorescence, or immunohistochemical staining. Results: CXCR2 expression was higher in chemoresistant breast cancer cell lines, high-metastatic cell lines and breast cancer tissues than in chemosensitive cell lines, low-metastatic cell lines, and breast cancer tissues. Overexpression of CXCR2 promoted cell proliferation, migration, invasion, cell anti-apoptosis, tumor formation, metastasis, and chemoresistance, but silencing of CXCR2 inhibited those activities both in vitro and in vivo. Mechanism studies revealed that CXCR2 suppresses AKT1 to promote breast cancer metastasis and chemoresistance through cyclooxygenase-2 (COX-2; PTGS2) to regulate caveolin-1, MMP2, MMP9, E-cardherin, and beta-catenin, which can be inversed by knock down of CXCR2 or COX-2, and over expression of AKT1 and P85alpha. Additionally, over expression of CXCR2 and COX-2, or silencing of PI3K/AKT1 inhibits p53 phosphorylation (Serine 15) and E2F1 expression, but activates MDM2, Bcl-xL and Bcl-2, leading to increased anti-apoptosis. Tissue microarray analysis from 300 breast cancer patients also indicated that over expression of CXCR2 is associated with enhanced COX2 expression and reduced AKT1 expression in metastatic and chemoresistant breast carcinomas (P Conclusions: Our results suggest that CXCR2 controls breast cancer metastasis and chemoresistance through regulating COX-2 and AKT1. Thus, antagonists of CXCR2 and COX-2 may be used synergistically to treat breast cancer patients particularly with high metastasis and chemoresistance. Citation Format: Han Xu, Fengjuan Lin, Ziliang Wang, Jiao Meng, Huizhen Sun, Zihao Qi, Yan Wang, Zhouluo Ou, Zhimin Shao, Genhong Di, Gong Yang. CXCR2 controls breast cancer metastasis and chemoresistance through PI3K/AKT and COX-2 signalings. [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 548. doi:10.1158/1538-7445.AM2013-548 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.