THC treatment leads to reduced tumor burden and tumor-cell apoptosis in vivo.

C57BL/6 mice were injected IP on day 0 with 1 × 10⁶ EL-4 tumor cells. On day 10, the mice were treated with various doses of THC (1, 3, or 5 mg/kg IP) or the vehicle. One day later, the peritoneal cavity was flushed with 5 mL PBS, and the tumor cells were collected by aspiration. (A) The cell number was determined by trypan blue dye exclusion. The data represent the mean ± SEM from groups of 3 mice. (B) The tumor cells recovered from the peritoneal cavity were tested for apoptosis using the TUNEL method. Filled histogram shows tumor cells exposed to THC and open histogram shows cells exposed to the vehicle.