Abstract 2503: PI3K/Akt/mTOR activity is a major determinant for the sensitivity of <i>NPM-ALK</i> (+) anaplastic large cell lymphoma cells to ALK inhibition
Authors: Matthew R. Quail, Weihua Wan, Xiaoyi Su, Gregory R. Ott, Amy J. Landis, Lihui Lu, Bruce D. Dorsey, Bruce A. Ruggeri, Mangeng Cheng
Journal: Cancer Research (2010)

Abstract Anaplastic large cell lymphomas (ALCLs) are a unique subgroup of high grade non-Hodgkin lymphomas. Approximately 60% to 70% of ALCLs contain a t (2:5) (p23; q35) chromosomal rearrangement, generating the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) fusion protein. NPM-ALK encodes a constitutively activated tyrosine kinase directly involved in the pathogenesis of ALCL. Recent studies have provided solid proof-of-concept validation that inhibition of ALK is sufficient to attenuate the growth and proliferation of ALK (+) ALCL cells. However, differential sensitivity to an ALK inhibitor among human NPM-ALK (+) ALCL cell lines has also been observed. In this study, using 2 fused pyrrolocarbazole (FP)-derived ALK inhibitors and a diaminopyrimidine (DAP)-derived ALK inhibitor as tools, the sensitivity of ALCL cells to ALK inhibition and the signaling pathway(s) that may contribute to the differential sensitivity of ALCL cells to ALK inhibition were characterized and compared. In all four NPM-ALK (+) ALCL cell lines tested, inhibition of Stat3 phosphorylation was consistent with ALK inhibitory activity. In contrast, inhibition of Akt phosphorylation by the FP- or DAP-ALK inhibitor was only observed in the more sensitive cell lines, Sup-M2 and Sudhl-1 cells while in less sensitive cell lines, Karpas-299 and SR-786 cells, Akt was constitutively activated even when ALK phosphorylation was completed abolished. Treatment with LY-294002, a PI3K inhibitor, at 30 µM completely inhibited Akt phosphorylation and led to partial growth inhibition of Karpas-299 and SR-786 cells. Co-treatment with LY-294002 and the FP- or DAP-ALK inhibitor significantly enhanced the cytotoxicity against Karpas-299 and SR-786 cells, similar to the degree observed in Sup-M2 or Sudhl-1 cells treated with the same concentration of ALK inhibitor alone, suggesting PI3K/Akt activity is a major determinant for the sensitivity of NPM-ALK (+) ALCL to ALK inhibition. Karpas-299 subcutaneous tumor xenografts displayed faster growth rate than Sup-M2 tumor xenografts in mice, and the DAP-ALK inhibitor was less efficacious against Karpas-299 tumor xenografts (about 40% TGI and 55% TGI respectively @ 30 or 55 mg/kg, bid, po) compared to that observed against Sup-M2 tumor xenografts (partial and near complete tumor regression respectively at the same dose regimes). Treatment of mice bearing Karpas-299 tumor xenografts with rapamycin, an mTOR inhibitor, @ 10 mg/kg, ip led to the inhibition of S6 and eIF4G phosphorylation in tumor xenografts. Co-administration of rapamycin (10 mg/kg, qd, ip) and the DAP-ALK inhibitor (55 mg/kg, bid, po) significantly enhanced the anti-tumor efficacy against Karpas-299 tumor xenografts and led to near complete tumor regression. These data further support that PI3K/Akt/mTOR activity is a major determinant for the sensitivity of NPM-ALK (+) ALCL to ALK inhibition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2503.