Figure 6
Knockdown of SR-BI inhibits xenograft tumor growth in vivo. (A) Knockdown of SR-BI in MDA-MB-231 cells decreases tumor growth in vivo. Athymic nude mice were injected with 106 MDA-MB-231 cells carrying control shRNA (shCTL) or shSRBI. Four weeks after injection, mice were killed, and tumors were excised. Tumors were weighed and volume determined by using the formula (length × width2)/2. Columns represent the mean volume and mass, respectively; bars represent ±SD. Tumors obtained with shCTL cells were significantly larger by weight and volume than were the tumors obtained with shSRBI. (*P < 0.05; n = 14 shCTL, n = 13 shSRBI) (B) Knockdown of SR-BI in MCF7 cells decreases tumor growth in vivo. MCF7 cells (5 × 106) were orthotopically injected into the mammary fat pads of 9-week-old athymic nude mice implanted with slow-release 17β-estradiol pellets (0.36 mg/pellet, 60 days). Four weeks after injection, mice were killed, and the tumors were excised. Tumors were weighed and volume determined by using the formula (length × width2)/2. Columns represent the mean volume and mass, respectively; bars represent ± SD. The shCTL tumors were significantly larger by volume than were the shSRBI tumors (*P < 0.05; n = 8 shCTL, n = 7 shSRBI). (C) shCTL tumors display increased expression of proliferative markers compared with shSRBI tumors. Immunohistochemistry was performed to determine expression patterns of SR-BI and pErk1/2 in MDA-MB231 tumors. (D) The shCTL tumors display increased expression of proliferative markers compared with shSRBI tumors. Three tumors per cell type were analyzed by Western blot analysis for the indicated proteins. GAPDH was used as a loading control.