Fig. 4. In vivo tumor growth of MMT cells stably expressing shRNA, MMT Rs, MMT Ri erm, MMT Ri pea3 and MMT Ri pea3/erm. (A) Validation of shRNA-mediated pea3 and erm knockdown. Relative mRNA expression levels of pea3 in MMT cells infected with pRS-pea3 A (dark gray bars) or pRS-pea3/erm (dark striped bars) and erm in MMT cells infected with pRS-erm (light gray bars) or pRS-pea3/erm (light striped bars) versus control pRS retroviruses, as assessed by quantitative RT-PCR. Results are expressed as ratios of mRNA levels of pea3 or erm to cyclophilin (endogenous control standard) (1=Rs) and are the mean ± s.d. of 3 experiments in duplicate. (B) Tumor growth of the MMT cells stably expressing shRNA. MMT cells infected with pRS-pea3 A, pRS-erm, pRS-pea3/erm or pRS retroviruses were subcutaneously injected into SCID mice. Three days after injection, tumors were measured every 3 days for 15 days. Values represent the mean ± s.d. of one representative experiment (five mice per group) from the three experiments under identical conditions. Error bars indicate + s.d. ^* P<0.05, ^** P<0.01.