Cancer Letters

Cancer Letters

Volume 278, Issue 2, 18 June 2009, Pages 139-144
Cancer Letters

NSC606985 induces apoptosis, exerts synergistic effects with cisplatin, and inhibits hypoxia-stabilized HIF-1α protein in human ovarian cancer cells

https://doi.org/10.1016/j.canlet.2008.12.025Get rights and content

Abstract

The camptothecins, which target the intranuclear enzyme topoisomerase I, have advanced to the forefront of several areas of developmental chemotherapy of cancers. In the present study, we investigated the potential anti-human ovarian cancer effects of NSC606985, a novel and rarely studied camptothecin analog, and its combination with cisplatin (CDDP). Human ovarian cancer cell line COC1 cells were treated with different nanomolar of NSC606985 with or without CDDP, and cell growth and apoptosis were evaluated, respectively, by MTT assay and annexin-V assay on flow cytometry. Chou–Talalay analysis was used to evaluate combined effect of NSC606985 and CDDP. Western blot was used to detect protein kinase Cδ (PKCδ), caspase-3 and hypoxia-inducible factor-1α (HIF-1α) proteins. Our results showed that NSC606985 at nanomolar concentration induced apoptosis with the activation of PKCδ in COC1 cells. Especially, NSC606985 presented the significant combined effects on COC1 cells in terms of growth inhibition and apoptosis induction. In addition, NSC606985 significantly antagonized the accumulation of HIF-1α stabilized by hypoxia or hypoxia-mimetic agent. These results suggest that NSC606985 and its combination with CDDP present the therapeutic potential on ovarian cancer, and deserve further preclinical and clinical studies.

Introduction

Ovarian carcinoma is the seventh most common malignancy and the fifth leading cause of death from cancer in women [1], [2]. Due to the asymptomatic nature of early ovarian cancer, patients were diagnosed predominately at advanced stage [2], [3]. Primary treatment of ovarian cancer involves cytoreductive surgery and platinum-based combination chemotherapy, to which more than 80% of patients show an initial chemotherapeutic response. However, most women with advanced-stage disease at initial diagnosis will develop recurrent tumors that are resistant to traditional platinum-based therapy [4]. As documented, patients with ovarian cancer had a 5-year survival rate of less than 30% [3]. Therefore, it is imperative to continue exploring for novel therapies for ovarian cancer.

Camptothecin represents a promising new class of anticancer drugs, and have advanced to the forefront of several areas of therapeutic and developmental chemotherapy [5]. For example, topotecan, a water-soluble, semisynthetic analog of camptothecin, has been approved by the US Food and Drug Administration for the treatment of recurrent epithelial ovarian cancer and has demonstrated activity in both platinum – and paclitaxel-resistant ovarian cancer [6]. More recently, lower concentration (nanomolar, nM) of NSC606985, a highly water-soluble camptothecin analog [7], was reported to induce apoptosis in acute myeloid leukemia (AML) cells [8], and to present the potential therapeutic effects on the leukemic mice model [9]. Furthermore, NSC606985 was also shown to induce cell apoptosis and growth arrest in prostate tumor cells [10]. In this work, we attempted to explore the potential effects of NSC606985 and its combination with cisplatin (CDDP), a very well-established agent in the treatment of ovarian cancer [11], on ovarian cancer cells.

Section snippets

Cell treatment

Human ovarian cancer line COC1 was purchased from China Typical Culture Collection Center (Wuhan, China), and were cultured in RPMI-1640 medium (Sigma, St Louis, MO) supplemented with 10% heat-inactivated fetal calf serum (FCS; Hyclone, Logan, UT) in a 5% CO2 95% air humidified atmosphere at 37 °C. For experiments, cells were treated with the indicated concentrations of NSC606985 (kindly provided by National Cancer Institute Anticancer Drug Screen standard agent database, Bethesda, MD, and

NSC606985 induces apoptosis of human ovarian cancer COC1 cell line

To explore the effect of NSC606985 on human ovarian cancer cells, COC1 cells were treated with various concentrations (from 6.25 to 100 nM) of NSC606985 for the time period of 1 to 3 days, and cell growth was detected by MTT assay. The results showed that nM concentrations of NSC606985 induced growth inhibition in the time- and concentration-dependent manners (Fig. 1A). The estimated IC50 values for NSC606985 were 117.70, 29.73 and 19.27 nM for 24, 48 and 72 h treatments, respectively. To

Discussion

Camptothecin, an alkaloid isolated from the Chinese tree Camptotheca acuminata, have become a rapidly growing family of anticancer agents. Especially, topotecan has been approved as a second-line therapy for ovarian cancer or small-cell lung cancer, and irinotecan for the treatment of colorectal carcinoma refractory to 5-fluorouracil or as initial therapy in combination with 5-flurouracil for the treatment of metastatic colorectal cancer [18]. In the past years, anti-leukemic and anti-prostate

Conflict of interest

None of the authors has any potential conflicts of interest.

Acknowledgements

We are grateful to Dr. Robert Schultz at Division of Cancer Treatment and Diagnosis, National Cancer Institute (Bethesda, MD) to provide us the NSC606985 compound. This work has been sponsored by grants from International Collaborative Items of Ministry of Science and Technology of China (2006DFA32780) and National Natural Science Foundation (30500257), Science and Technology Commission of Shanghai (08JC1413700). Dr. GQ Chen is a Chang Jiang Scholar of Ministry of Education of China, and is

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