FIG 4.

FGF signaling reduces the proportion of lung cancer stem cells. (A) Semiquantitative RT-PCR analysis of epithelial-specific FGF receptor isoforms FGFR1b and FGFR2b, in five cancer cells. (B) Semiquantitative RT-PCR analysis for FGFR1b-reacting FGFs (coded for by the FGF1, FGF2, FGF3, FGF7, FGF10, and FGF22 genes) in MSCs from three unrelated donors. For panels A and B, expression of β-actin mRNA (ACTB) was used as a control. (C and D) Functional analysis of recombinant FGF proteins. Cancer cells were cultured for 48 h with recombinant FGF10, FGF1, or vehicle (PBS [control]) and were stained with Hoechst 33342 to analyze the side population. A representative side population subset (SP) with its percentage in H1299 lung cancer cells (C) and proportions of five cancer cells in the side population (D) are shown. The cell proportion is reported as the mean percentage ± standard error per group (n = 3). Asterisks indicate significant differences compared with the control vehicle.