NVP-BKM120 (
BKM120) is a new pan-class I phosphatidylinositol-3
kinase (PI3K) inhibitor and has been tested in clinical trials as an
anticancer agent. In this study, we determined whether
BKM120 induces autophagy and the impact of autophagy induction on
BKM120's growth-inhibitory activity.
BKM120 potently induced elevation of autophagosome-bound type II LC3 (LC3-II)
protein, predominantly in cell lines insensitive to
BKM120, thereby inducing autophagy. The presence of lysosomal
protease inhibitor chloroquine further enhanced the levels of LC3-II.
BKM120 combined with
chloroquine, enhanced growth-inhibitory effects including induction of apoptosis, suggesting that autophagy is a protective mechanism counteracting
BKM120's growth-inhibitory activity. Interestingly,
BKM120 increased p-ERK1/2 levels. When blocking the activation of this signaling with
MEK inhibitors or with knockdown of ERK1/2, the ability of
BKM120 to increase LC3-II was attenuated and the growth-inhibitory effects including induction of apoptosis were accordingly enhanced, suggesting that the
MEK/ERK activation contributes to BKM120-induced authophagy. In mouse xenograft model, we also found that the combination of
BKM120 and
PD0325901 synergistically suppressed cell growth in human
lung cancer cells. Thus, the current study not only reveals mechanisms accounting for BKM120-induced autophagy, but also suggests an alternative method to enhance
BKM120's therapeutic efficacy against
non-small cell lung cancer(NSCLC) by blocking autophagy with either a lysosomal
protease inhibitor or
MEK inhibitor.