2.2 Cell lines
MC38 (a mouse colon tumor cell line) and RM-1 (a mouse prostate tumor cell line) cell lines were purchased from ATCC (Manassas, VA, USA). These cells were maintained in DMEM supplemented with 100 U/mL penicillin, 100 mg/mL streptomycin, and 10% fetal bovine serum (FBS). DMEM and FBS were purchased from Gibco (Grand Island, NY, USA).