Figure 4. MICA and ULBP2 expression is stably upregulated in senescent, but not quiescent cells. Growing IMR-90, WI38 and BJ cells were treated with Etoposide (100μM) and the level of MICA and ULBP2 expression were assessed by RT-PCR. The expression of MICA (A) and ULBP2 (B) was elevated 24 hours following treatment and was maintained at higher levels throughout the indicated time points. Growing cells at day 0 served as control. (C) Growing cells were treated with a low concentration of Etoposide (10μM) to induce transient growth arrest and the level of MICA and ULBP2 expression were assessed by RT-PCR. (D) IMR-90 cells were grown to confluence and maintained for a further 7 days until cells became quiescent. Cell-cycle arrest induced by quiescence was not sufficient to elevate MICA and ULBP2 expression as assessed by RT-PCR and compared to growing and senescent cells. Data presented as mean with S.E.M of three independent experiments. Two-tailed t-test *P<0.05, **P<0.001, ***P<0.0001.