Combating autophagy is a strategy to increase cytotoxic effects of novel ALK inhibitor entrectinib in neuroblastoma cells

// Sanja Aveic 1 , Marcella Pantile 1 , Anke Seydel 1 , Maria Rosaria Esposito 1 , Carlo Zanon 1 , Gary Li 2 , Gian Paolo Tonini 1 1 Neuroblastoma Laboratory, Pediatric Research Institute, Città della Speranza, Padua, Italy 2 Ignyta Inc., San Diego, California, USA Correspondence to: Sanja Aveic, e-mail: s.aveic@irpcds.org Keywords: neuroblastoma, autophagy, ALK inhibitors; drug combination, entrectinib Received: July 21, 2015     Accepted: December 22, 2015     Published: December 28, 2015 ABSTRACT Neuroblastoma (NB) is a threatening childhood malignancy. Its prognosis is affected by several morphological, and biological characteristics, including the constitutive expression of ALK tyrosine kinase. In this study we examined the therapeutic potential of a novel ALK inhibitor, entrectinib, in obliterating NB tumor cells. Entrectinib showed the growth-inhibitory effects on NB cells with a 50% inhibitory concentration range of 0.03–5 μM. In the ALK-dependent cells, entrectinib mediated G1-arrest, which was associated with modified expression of multiple cell-cycle regulators. Down-regulation of Ki-67 , and attenuated phosphorylation of ERK1/2, and STAT3, correlated with observed antiproliferative capacity of entrectinib. Initial cytostatic activity of entrectinib was followed by concentration-dependent apoptotic cell death, and Caspase-3 activation. However, we delineated a reduced sensitivity of ALK mutated NB cells to entrectinib, and demonstrated strong activation of autophagy in SH-SY5Y F1174L NB cell line. Abrogation of autophagy by chloroquine increased significantly the toxicity of entrectinib, as confirmed by enhanced death rate, and PARP protein cleavage in SH-SY5Y F1174L cells. In aggregate, our data show that entrectinib inhibits proliferation, and induces G1-arrest, and apoptosis in NB cells. We propose entrectinib for further consideration in treatment of NB, and recommend pharmacological inhibition of autophagy to be explored for a combined therapeutic approach in NB patients that might develop resistance to entrectinib.