Toward Better Predictions of Chemosensitivity: Comparative Study of Conventional and Simulated Chemosensitivity Tests for Bladder Cancer Cell Lines

Dear Editor, The recurrence rate of bladder cancer reaches up to 40–50%, and progression from non-muscle invasive bladder cancer (NMIBC) to muscle invasive bladder cancer (MIBC) occurs in up to 9.8–13.8% of cases [1]. When bladder cancer progresses to MIBC, radical cystectomy with orthotopic neobladder substitution or urinary diversion is required to improve survival, although this decreases patient quality of life [2]. Intravesical instillation of a chemotherapeutic agent is usually performed in cases of NMIBC to prevent recurrence after transurethral resection of the bladder tumor (TURBT) [3]. In moderate-risk or high-risk NMIBC patients, successive instillation of an intravesical chemotherapeutic agent once a week for six weeks is usually performed [4-6]. Given that proper selection of chemotherapeutic agents is essential for positive outcomes, chemosensitivity tests are required to provide a rationale for drug selection. To date, chemosensitivity tests have been based on cell survival assessments after a single treatment at a specific time with various methods. However, these in vitro tests are not accepted as routine tests before chemotherapy [7]. We developed in vitro chemosensitivity tests mimicking the situation of clinical chemotherapy by supporting the survival of a cancer cell line in vitro under treatment with an actual intravesical chemotherapy schedule. Mitomycin C, epirubicin, gemcitabine, and docetaxel were used at six concentrations for the chemosensitivity tests in six bladder cancer cell lines: J82, T24, SW780, UM-UC-3, TCCSUP, and HT-1376. For conventional analysis, cancer cells were seeded in welled plates (5×10 cells/well) on day one. The chemotherapeutic agent was administered from a dose of 0 (no drug) to 200% on the second day, and chemosensitivity tests were performed after five days. A negative control (no cells) was included on each evaluation plate. The effects of the drugs on cell viability were tested by using CellTiter 96 aqueous nonradioactive cell proliferation assay kits (Promega Co., Madison, WI, USA). Tests were repeated three times, and the mean values were analyzed. Inhibition as a percentage of cancer cells was measured for each plate by using the formula (1-T/C)×100, where T/C=absorbance of cultured cancer cells treated with each test drug/absorbance of cultured cells not treated with the test drug. Simulation of intravesical chemotherapy was performed according to an in vivo schedule. Chemotherapy was performed once a week in cells in plate wells for two hrs for six weeks (six cycles). The medium containing the chemotherapeutic agent was removed, and fresh medium was added to the wells; two-