Combination Therapy for Tumor Xenografts

Animal studies were performed as published before [24 (link)] and in accordance to the guidelines of the Canadian Council on Animal Care with institutional certifications (University of British Columbia, A15–0231). Briefly, Caki-1WT/DC cells were injected subcutaneously (5 × 10⁶ cells) in the flank region of 8 weeks old nude mice (Charles Rivers Laboratories, MA, USA). Mice were randomly divided into groups after the tumors reached a volume of 100-200 mm³. Sunitinib malate was suspended in citrate-buffered solution (pH 3.5) and elacridar in diluent (0.5% methyl cellulose and 1% Tween-80 in ddH₂O). Treatment was administered by oral gavage once daily for 5 days followed by 2 days off for 2–3 weeks. For the combination treatment, mice were treated with elacridar 15 min prior to the administration of sunitinib malate. Tumor volume was measured every 3 days using calipers and calculated: tumor volume (mm³) = length×width×height× 0.5. Each treatment group had more than 5 mice. Tumors were fixed with 10% para-formaldehyde (Sigma-Aldrich, MO, USA) for 24-48 h, 70% ethanol for 24 h (VWR International, PA, USA) followed by paraffin embedding.