ABSTR 0932 – Poster Presentation: Cytotoxicity and Pharmacokinetics of Four Platinum Salts in Human Colon Carcinoma Cell-Line HCT116

摘要

Background: Adding oxaliplatin to 5-FU–based regimens improves outcomes of patients with colorectal cancer in the metastatic and adjuvant settings. The benefit of adding oxaliplatin (or other radiosensitizers) to chemoradiotherapy for rectal cancer has been suggested, but the best oxaliplatin schedule is yet to be determined. Newer liposomal formulations of platinums have been proposed to allow higher intracellular concentrations of platinum with limited toxicity. Understanding the cytotoxic mechanisms of platinum-based drugs and elucidating their underlying pharmacokinetics are crucial to improve their efficiency as radiosensitizers, and to determine the best treatment scheme for these patients. We studied the cytotoxic effects on human colorectal cancer cell line, the intracellular accumulation, and the DNA binding for Lipoplatin? and Lipoxal?, the liposomal formulations of cisplatin and oxaliplatin, respectively, which were compared to the liposome-free platinum compounds. Methods: The human colorectal cancer cell-line HCT116 cells was used. Cell growth inhibition by platinum derivatives was evaluated with a colony formation assay. The inhibitory concentration (IC₅₀) for each drug was determined. Cells exposed to cisplatin, oxaliplatin, Lipoplatin? and Lipoxal? at the IC₅₀ concentration were analyzed for their intracellular accumulation and DNA-binding of platinum using inductively coupled plasma mass spectrometry at 1, 4, 8, 24, and 48 h from exposure. Figure 1: Time course of the cellular accumulation of platinum derivatives in HCT116 cells. Cells were incubated at the IC₅₀ concentration previously measured after 4 h incubation. The amount of platinum accumulated in the cells was measured using ICP-MS. Each ... Figure 2: Time course of the binding of platinum to DNA after exposing the HCT116 cells. Cells were incubated at the IC₅₀ concentration previously measured after 4 h incubation. The amount of platinum accumulated in the cells was measured using ICP-MS. Each point ... Results: The colony formation assays showed an IC₅₀ of 7, 7.5, 21, and 70μM, for oxaliplatin, cisplatin, Lipoxal?, and Lipoplatin?, respectively. The liposomal formulations had reduced cytotoxicity on the HCT116 cells. The cellular uptake for three platinum derivatives continued to increase with time, except for oxaliplatin, which reached a plateau after 24 h incubation. Despite a higher intracellular accumulation, liposomal oxaliplatin provided lower DNA-bound platinum than the regular formulation. These data suggest that the liposomal oxaliplatin accumulated in the cancer cell might be relatively stable, which prevents the release of free oxaliplatin, impeding its binding to DNA. Conclusion: Our results support that incorporation of cisplatin and oxaliplatin in a liposomal formulation can reduce their cytotoxicity in vitro . Despite higher intracellular concentration, a smaller fraction is incorporated into DNA. Our subsequent trials on combined chemoradiotherapy will determine if the DNA-bound platinum will reflect the radiosensitizing effect for each drug. Articles from Gastrointestinal Cancer Research : GCR are provided here courtesy of International Society of Gastrointestinal Oncology