Efficacy of selective estrogen receptor modulators (SERMs) in a murine xenograft model bearing human bladder cancer

Abstract

4582 We have demonstrated through Western Blot and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) that estrogen receptor (ER)-beta is expressed in RT-4, 5637, T-24, TSU-PR1 and TCC-SUP human bladder cancer cell lines, while ER-alpha is expressed at very low levels. Raloxifene, a SERM, induced apoptosis and decreased the viability of RT-4, T-24, and 5637 cell-lines in-vitro. Using tissue microarray analysis ER-beta was expressed in 133 (63.3%) of 210 bladder tumors, while ER-alpha was expressed in only 2 tumors. The expression of ER-beta was associated with higher stage and grade. We constructed a murine xenograft model bearing human bladder cancer to evaluate the efficacy of SERMs in an animal model. A total of 107 5637 human transitional cell carcinoma cells (suspended in 0.1 ml of a 1:1 mixture of RPMI with 10% FBS and matrigel) were injected into one site at a mammary fat pad of 6–8 week old female athymic BALB/c nu/nu mice. Only mice that developed measurable subcutaneous tumor (at least 3 mm in one dimension) within 2 weeks were chosen for further study. Raloxifene 100 mg (Sigma-Aldrich) powder was suspended in 9 ml of double-distilled water. One milliliter of 90% CMC and 10% PEG400/Tween80 was added to the raloxifene solution for a final concentration of 10 mg/ml. Five cohorts of mice consisting of 6–8 mice per cohort were administered no therapy, placebo (solvent only without raloxifene), raloxifene 0.01 mg/day, raloxifene 0.1 mg/day and raloxifene 1 mg/day for 5 days a week by oral gavage for 8 weeks. All of the doses of raloxifene significantly inhibited the growth of tumor (p<0.05). In a separate experiment, 107 5637 cells were subcutaneously injected into the flanks of 6–8 week old female athymic nu/nu mice. Four cohorts of mice with measurable tumors with 6–8 mice per cohort were implanted with subcutaneous 60-day time-release pellets (Innovative Research of America, Sarasota, FL) delivering placebo, tamoxifen 0.008 mg/day, tamoxifen 0.125 mg/day and tamoxifen 1.25 mg/day, respectively. Significant inhibition of tumor was observed with all of the doses of tamoxifen (p< 0.01). These data provide the rationale for evaluating SERMs as a targeted therapuetic for patients with bladder cancer. No significant financial relationships to disclose.