FIGURE 6.

Effect of loss of mtSSB function on mitochondrial mass, oxygen consumption, and cell growth. A, shown are representative microphotographs of an immunoblot demonstrating stable mtSSB knockdown (KD) in 143B cells that was achieved by using a viral vector containing shRNA against human mtSSB. The knockdown was confirmed for at least 10 passages. B and C, shown is the effect of mtSSB knockdown on the amount of mtDNA (B) and oxygen consumption (Vresp.) (C) in 143B cells. Mitochondrial DNA content and the rate of oxygen consumption were determined as described under “Experimental Procedures.” D and E, shown is the effect of mtSSB loss-of-function on the growth of cancer cells in vitro and in vivo. D, wild-type 143B or 143B-KD-mtSSB cells were seeded in 6-well plates at the density of 100,000 cells per well. After 24 or 48 h of incubation, the cells were trypsinized, harvested, and counted using an automatic cell counter. E, wild-type 143B or 143B-KD-mtSSB cells were injected subcutaneously into mice. Tumor size was measured at 7, 14, and 21 days. Values represent the means ± S.E.; n = 4 independent measurements. *, p < 0.05, as compared with non-transfected 143B cells.