Cell cycle arrest and autoschizis in a human bladder carcinoma cell line following Vitamin C and Vitamin K3 treatment

Exponentially growing cultures of human bladder tumor cells (T24) were treated with Vitamin C (VC) alone, Vitamin K₃ (VK₃) alone, or with a VC:VK₃ combination for 1, 2, or 4hr. Flow cytometry of T24 cells exposed to the vitamins for 1h revealed a growth arrested population and a population undergoing cell death. Cells in G₁ during vitamin treatment arrested in G₁ while those in S phase progressed through S phase and arrested in G₂/M. DNA synthesis decreased to 14 to 21% of control levels which agreed with the percent of cells in S phase during treatment. Annexin V labeling demonstrated the majority of the cells died by autoschizis, but necrosis and apoptosis also were observed. Catalase treatment abrogated both cell cycle arrest and cell death which implicated hydrogen peroxide (H₂O₂) in these processes. Redox cycling of VC and VK₃ increased H₂O₂ production and decreased cellular thiol levels and DNA content, while increasing intracellular Ca²⁺ levels and lipid peroxidation. Feulgen staining of treated cells revealed a time-dependent decrease in tumor cell DNA, while electrophoresis revealed a spread pattern. These results suggest that Ca ²⁺ disregulation activates at least one DNase which degrades tumor cell DNA and induces tumor cell death.