Abstract 1796: Significant in-vitro anti-myeloma activity of a novel Akt inhibitor MK2206
Authors: Ramakrishnan Vijay , Haug Jessica , Kimlinger Teresa , Halling Timothy , Wellik Linda , Rajkumar S Vincent , Kumar Shaji 
Published: February 2011

Abstract
Background: Cytokine stimulated signaling pathways contribute to multiple myeloma (MM) disease progression and in acquired resistance to current treatment options making MM an incurable malignancy. The PI3K/Akt/mTOR pathway is up-regulated in MM and appears to be critical for cell proliferation and blocking this pathway might have profound impact on disease progression. In addition, this pathway also has been found to cross talk with other signal transduction pathways preventing drug-induced apoptosis.
Methods: MK2206 was obtained from Merck Inc. MTT assay was performed to study drug induced cytotoxicity and thymidine uptake was used as a measure to study differences in proliferation. Flow cytometry using Annexin V-FITC and propidium iodide (PI) was used to measure drug induced apoptosis in cell lines and patient cells. In addition, apo-2.7 was also used to measure apoptosis in patient cells.
Results: MK2206 treatment led to dose and time dependent decrease in cell viability as observed by MTT assay with an IC50 range of 1-5µM on most MM cell lines tested. Most of the cytotoxicity was observed by 48hours with minimal increase in cytotoxicity beyond that point. The drug was able to induce cytotoxicity in myeloma cell lines when cells were cultured with IGF, IL6, or VEGF with minimal increase in IC50 values. MK2206 also inhibited MM cell proliferation as observed by reduced thymidine uptake. This reduction in proliferation was also observed when MM cells were co-cultured with bone marrow stromal cells. When myeloma cell lines were treated with the drug for various time points, percentage of apoptotic cells increased with time of incubation with the drug as observed by flow cytometry and annexin V-FITC/PI staining. There was also a time dependent increase in caspase cleavage observed indicating that MK2206 might elicit its functions by inducing caspase dependent pathways. Further studies are being carried out to understand the importance of caspase dependent pathways for the success of anti-MM effects of MK2206. Also, MK2206 was able to induce apoptosis in patient derived primary cells, though with varying degrees of response observed between patients. Examining signaling pathways by immunoblotting demonstrated clear down regulation of pAkt and Bcl-xl levels post treatment with the drug with minimal decrease in proteins associated with other signaling pathways, like pSTAT3 and pERK.
Conclusions: Taken together, our studies demonstrate significant anti-MM activity of MK2206 in-vitro. We are currently testing MK2206 in combination with known inhibitors of the other important signaling pathways implicated in MM disease biology as well as in-vivo experiments in mouse models. Performing these experiments will further validate the efficacy of MK2206 as an anti-MM agent and form the basis for it to be taken up for clinical evaluation either as a single agent or in combination with other agent(s).
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 1796.