Abstract 5010: Targeting of AKT pathway inhibit high-risk neuroblastoma growth

Abstract

Abstract High-risk neuroblastoma (NB) represents a major clinical challenge in pediatric oncology. Despite intensive genotoxic therapies, long-term survival for NB patients remains poor (<45%), and the disease accounts for almost 15% of all pediatric cancer deaths. Relapse of metastatic, drug-resistant disease, and treatment-related toxicities mandate the development of novel therapeutic strategies for NB patients. Oncogenic activation of AKT signaling pathway has been shown in different cancer types, including NB. Activation of AKT pathway induce cancer progression, proliferation, metabolism, angiogenesis, and resistance to drug-induced apoptosis. Activation of PI3K (phosphatidylinositol 3-kinase) and PDK1 (3-Phosphoinositide-dependent kinase 1) are the two major steps that mediate the AKT phosphorylation and activation. In the present study, we performed a custom low-density Human AKT pathway array and found that genes coding for PI3K, PIP3, PDK1, and AKT are overexpressed in NB cells in comparison to normal human fibroblast cells. Further, we analyzed a total of 1135 NB patient samples to determine the effect of PI3K and PDK1 overexpression on NB patient survival and correlation with disease stage. Kaplan-Meier analyses of patient datasets revealed that both PI3K and PDK1 high levels strongly correlate with poor overall and event-free survival of NB patients (p<0.0001). In addition, higher stage, more aggressive tumors have significantly higher PI3K and PDK1 expression, suggesting that gain of PI3K or PDK1 function may lead to de-differentiated invasive malignancy. To further analyze the effect of PI3K and PDK1 on NB cell proliferation, we used specific small molecule inhibitors that target PI3K and PDK1, and performed cell proliferation assays in NB cell lines. Results show that inhibition of either PI3K or PDK1 significantly inhibit NB cell proliferation (p<0.01) in a dose-dependent manner. Furthermore, both of the inhibitors induce apoptosis, block cell cycle progression, inhibit colony formation, and inhibit cell migration in NB cells, in comparison to control. Additionally, we performed in vitro 3D sphere formation assays that mimic in vivo tumor growth, and found that inhibition of AKT pathway by either inhibiting PI3K or PDK1 leads to significant reduction of sphere growth and size in contrast to control. Overall, these data highlight that: a) AKT signaling pathway is implicated in NB growth, b) PI3K and PDK1 upstream of the AKT are important regulators of NB proliferation, and c) direct targeting of these regulators is a novel therapeutic approach to high-risk NB. We will further explore these strategies and combine them with current therapies to develop effective therapeutic approaches for NB patients. Citation Format: Rameswari Chilamakuri, Saurabh Agarwal. Targeting of AKT pathway inhibit high-risk neuroblastoma growth [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5010.