Anaplastic lymphoma kinase activity is essential for the proliferation and survival of anaplastic large-cell lymphoma cells

The roles of aberrant expression of constitutively active ALK chimeric proteins in the pathogenesis of anaplastic large-cell lymphoma (ALCL) have been well defined; nevertheless, the notion that ALK is a molecular target for the therapeutic modulation of ALK(+) ALCL has not been validated thus far. Select fused pyrrolocar-bazole (FP)-derived small molecules with ALK inhibitory activity were used as pharmacologic tools to evaluate whether functional ALK is essential for the proliferation and survival of ALK+ ALCL cells in culture. These compounds inhibited interleukin 3 (IL-3)-independent proliferation of BaF3/NPM-ALK cells in an ALK inhibition-dependent manner and significantly blocked colony formation in agar of mouse embryonic fibroblast (MEF) cells harboring NPM-ALK. Inhibition of NPM-ALK phosphorylation in the ALK(+) ALCL-derived cell lines resulted in significant inhibition of cell proliferation and induction of apoptotic-cell death, while having marginal effects on the proliferation and survival of K562, an ALK(-) leukemia cell line. ALK inhibition resulted in cell-cycle G, arrest and inactivation of ERK1/2, STAT3, and AKT signaling pathways. Potent and selective ALK inhibitors may have therapeutic application for ALK(+) ALCL and possibly other solid and hematologic tumors in which ALK activation is implicated in their pathogenesis.