Inhibition of PDGF or LGL patient sera stimulation of NK leukemia cell line growth by blockade of PI3K/SFK or neutralizing antibody to PDGF-BB, respectively. (A-B) NKL cells were treated with rhPDGF-BB in presence of AG1296 at different concentrations (A), or in presence or absence of LY294002, PP2, or the combination of these 2 compounds (B); cell proliferation was measured by MTT assay. (C-D) NKL cells were treated with 10% pooled sera from patients with T-LGL leukemia (C) or from patients with NK-LGL leukemia (D) for 24 hours; cell proliferation was determined by MTT assay. Ten percent pooled sera sample from normal donors was used as controls. *P < .01 for cell viability in samples receiving 10% normal sera treatment versus samples receiving 10% LGL patient sera treatment; **P < .03 for cell viability in the samples receiving 10% patient sera treatment versus samples receiving treatment of 10% patient sera preincubated with anti–PDGF-BB neutralizing antibody. Rabbit IgG antibody was used as isotype control.