Elsevier

Gynecologic Oncology

Volume 98, Issue 1, July 2005, Pages 141-145
Gynecologic Oncology

An evaluation of cytotoxicity of the taxane and platinum agents combination treatment in a panel of human ovarian carcinoma cell lines

https://doi.org/10.1016/j.ygyno.2005.02.006Get rights and content

Abstract

Objectives

The objectives of this study were to determine the optimum schedule for combination of taxane and platinum agents in human ovarian carcinoma cell lines.

Methods

Cell growth inhibition was determined by the standard MTT assay and an IC50 was calculated for docetaxel, paclitaxel, cisplatin, and carboplatin in seven human ovarian cancer cell lines (CAOV-3, OVCAR-3, SKOV-3, ES-2, OV-90, TOV-112D, and TOV-21G). The IC50 was defined as the drug concentration required for a 50% reduction in optical density. Cytotoxicity assays were performed with four sequential combinations of a taxane and a platinum compound. In each combination, cell lines were treated with the appropriate IC50 of the drugs for varying time increments between 3 and 24 h. Controls were no drug, each agent alone and the combination of both. Results were obtained via manual cell counting with a hemocytometer.

Results

The inhibitory concentration to achieve 50% cell death (IC50) was determined for each compound in each cell line. The IC50 ranged from 0.8 to 1.7 nM, 0.7 to 1.8 nM for docetaxel and paclitaxel, respectively, and 17.4 to 25.7 μM, 15.1 to 25.7 μM for cisplatin and carboplatin, respectively.

Conclusion

In this study the combination of docetaxel plus cisplatin was considerably more active in vitro than any of the other taxane plus platinum agent combinations evaluated in the panel of human ovarian cancer cell lines. In vitro activity was similar to previously report clinical studies comparing taxane and platinum combination regimens. This suggests the combination of docetaxel with cisplatin will have enhanced clinical activity compared to the paclitaxel plus carboplatin regimen.

Introduction

Ovarian cancer is the most common cause of death from gynecologic malignancy and it is the fifth leading cause of cancer-related death [1]. The estimated number of new cases for the year 2004 was 25,580, while the estimated number of deaths was 16,090 [2]. The surveillance, epidemiology, and end results (SEER) data from 1989 to 1996 indicated a 95% versus 50% 5-year survival rate in localized stages versus all stages of ovarian cancer, respectively. With modern surgery and cytotoxic chemotherapy, an initial complete clinical response is seen in 70% of patients [1]. However, over 50% of these patients will recur within the first 2 years following their initial diagnosis. The agents used for chemotherapy in ovarian cancer have shifted over time from alkylating agents, to platinum-based chemotherapy, to the addition of taxane compounds in the development of combination therapies [3].

The taxanes are classified as anti-microtubular agents, stabilizing tubulin polymerization and cell arrest primarily in the M and G2 phases of the cell cycle. The taxanes have demonstrated significant activity in both pre-clinical models and clinical studies for the treatment of numerous solid malignancies. In vitro data have suggested that docetaxel is more potent than paclitaxel. In the gynecologic oncology setting, the dose-limiting toxicity of paclitaxel has been peripheral neuropathies. The dose-limiting toxicity of docetaxel has been myelosuppression, primarily neutropenia.

The platinum (PLT) analogues form PLT-DNA adducts that intercalate the DNA, thereby interrupting DNA synthesis. There are pre-clinical studies reported to support cisplatin having greater cytotoxic potential. Also, there are questions regarding the relationship between dose intensity and the platinum activity. Pre-clinical data suggest a benefit with dose intensity with platinum agents but clinical data are inconclusive. The dose-limiting toxicity associated with carboplatin is myelosuppression, primarily thrombocytopenia that resolves with limited complications. Both neurotoxicity and nephrotoxicity limit the dose of cisplatin. Higher doses of carboplatin have been associated with similar nephrotoxicity, neuropathies, and ototoxicity [4], [5]. The additive neurotoxicity associated with cisplatin and paclitaxel has limited the tolerability of this treatment combination in the clinical setting.

When focusing on toxicity profiles, studies such as GOG 158 by Ozols et al. have concluded that carboplatin is a reasonable substitution for cisplatin [6], [7]. Clinically, cisplatin and carboplatin given in combination with paclitaxel have demonstrated equal efficacy, with carboplatin demonstrating less neurotoxicity [8]. Recently, the question has arisen if the substitution of docetaxel in place of paclitaxel would be associated with even less neurotoxicity [9], [10]. The question still remains what is the best combination of taxane and platinum agents for the treatment of ovarian cancer. The primary objective of this in vitro study was to determine the optimal combination of the taxane agents and platinum agents to achieve maximum cytotoxic activity in human ovarian cancer cell lines. In this experiment, we evaluated the time-dependent cytotoxic effects of the combination of paclitaxel or docetaxel followed by each of the platinum agents over 3–24 h in six human ovarian cancer cell lines.

Section snippets

Drugs

Docetaxel was generously provided from Aventis Pharmaceuticals. Paclitaxel, cisplatin, and carboplatin were purchased from the institution pharmacy department. All drugs were diluted in fresh medium immediately before each experiment. Paclitaxel was available in a 6 mg/mL stock solution and docetaxel as a 40 mg/mL stock solution. The stock solution of carboplatin 10 mg/mL was prepared by diluting 15 mg of drug with 1.5 mL of respective cell culture media. Cisplatin was available in a 1 mg/mL

Results

Prior to initiation of the cytotoxicity assay, the growth inhibition assays were completed to determine the IC50 concentration for each agent in each ovarian cancer cell line. The IC50 concentrations for docetaxel ranged from 0.8 nM to 1.7 nM and paclitaxel had a similar range 0.7 nM to 1.8 nM. Previous in vitro studies have reported IC50 concentrations between 0.68 nM to 2.3 nM and 1.1 nM to 3.3 nM for docetaxel and paclitaxel, respectively [11], [12], [13], [14]. The growth inhibitory

Discussion

Although there are pharmacokinetic and pharmacodynamic limitations of in vitro data, the findings of this in vitro study were consistent with the clinical efficacy of comparison studies that have been reported previously. For example, consistent with the findings of the SCOTROC clinical study, in our in vitro study the combination of docetaxel plus carboplatin demonstrated similar in vitro activity in the panel of human ovarian cancer cell lines compared to the in vitro activity of paclitaxel

Acknowledgment

This research was sponsored by an unrestricted research grant from Aventis Pharmaceuticals, INC.

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