Class IA phosphatidylinositol 3-kinase inhibition inhibits cell growth and proliferation in mantle cell lymphoma

Background/Aims: Constitutive activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin signaling pathway preferentially occurs in aggressive blastoid variants of mantle cell lymphoma (MCL) and is implicated in the pathogenesis of this disease. In this study, we investigated the role of PI3K isoforms on proliferation of aggressive MCL cells. Methods: The changes in cell viability, cell cycle distribution and apoptosis induction by the PI3K isoform-selective inhibitors were evaluated. The molecular basis underlying the effects of the specific inhibition of PI3K isoforms was investigated by Western blot analysis. Results: Our results demonstrated that a class IA PI3K isoform is most commonly involved in the constitutive activation of Akt in aggressive MCL. Treatment with a p110 isoform-specific inhibitor induced prominent cell cycle arrest followed by apoptosis through complete abolishment of phosphorylated (p)-Akt and its downstream targets. An inhibitor of isoform p110δ induced moderate cell cycle arrest with downregulation of p-Akt and p-S6K. A dual inhibitor of p110 and p110δ GDC-0941 caused more prominent cell growth inhibition compared to selective p110 or p110δ inhibitors. Inhibition of the class IB PI3K isoform p110γ did not cause cell cycle arrest or induce apoptosis in MCL cells. Conclusion: These findings suggest that the therapeutic ablation of class IA PI3K may be a promising strategy for the treatment of refractory, aggressive MCL.