Inhibition of Jak2 is associated with growth arrest during differentiation of 32D-δ cells.
(A) Tyrosine phosphorylation of Jak2 in 32D-δ and 32D-δ–Jak2 cells. Cells were treated with TPA and IL-3, as indicated, and Jak2 was immunoprecipitated and subjected to anti-phosphotyrosine immunoblotting. Upper panel shows Jak2 protein levels. (B) Effect of Jak2 overexpression on IL-3 induced proliferation of 32D cells. Growing cells were washed twice and treated as indicated (AG490, 100 μmol/L, TPA 100 ng/mL). After 18 hours 3H-thymidine was added to the cultures for 6 hours, after which the cells were harvested. (C) TPA-induced differentiation and apoptosis in different derivatives of 32D cells. The microphotographs were taken from cells cultured for 24 hours in 2% FCS + IL-3 in the absence (left) or presence (right) of TPA (100 ng/mL). Insets show TUNEL staining of cells grown under identical conditions on coverslips.
