Figure 6

NPM-ALK oncogenic protein does not affect the levels of expression of IGF-IR and IGF-I. (A) Western blotting shows that at 48 h, downregulation of NPM-ALK by ALK siRNA was not associated with decreased expression of IGF-IR, pro-IGF-I or IGF-I proteins in SUP-M2, SR-786, and DEL cell lines. β-Actin shows equal protein loading. Analysis of IGF-IR levels after transfection of the cells with ALK siRNA was performed at extended time points (12, 24, 48, 72, and 96 h), and also in other cell lines including Karpas 299 and SU-DHL-1, with similar results (data not shown). (B) Downregulation of NPM-ALK in the 3 cell lines did not decrease the levels of IGF-IR mRNA. The example shown is at 48 h after transfection of the cells with ALK siRNA. The results are shown as means ± SE of 4 consistent experiments. In addition, analysis of IGF-IR mRNA was performed at other time points and cell lines as described in (A). Changes in IGF-IR mRNA levels were not detected at any time point (data not shown). (C) An ELISA assay showing that specific downregulation of NPM-ALK did not significantly decrease the levels of IGF-I secreted from the NPM-ALK⁺ T-cell lymphoma cells. The results represent the means ± SE of 3 experiments.