MDA-MB-231 cells (5×105) stably expressing vector control or shRNA targeting MRP4 along with stable expression of the luciferase enzyme (MDA-MB-231 shRNA/Luc, Figure 5A) were implanted subcutaneously proximal to the mammary fat pad of female BALB/c SCID mice; tumor growth was monitored by caliper, and metastatic spread was estimated by bioluminescent imaging [46]. This evidence concerns the gene ABCC4 and neoplasm.