The protein kinase Akt is commonly up-regulated in human cancers, leading to increased survival and proliferation, as well as to the relaxation of controls on cell cycle and genome integrity in various cell types. On the other hand, in some model systems Akt promotes terminal differentiation. I hypothesize that the status of additional cellular factors determines whether activated Akt contributes to tumorigenesis or to differentiation. Due to the pleiotropic role of Akt in normal cells, the events that cooperate with Akt in oncogenesis are likely to be more tractable therapeutic targets than Akt itself. We have established a model system in which Akt activation alone is unable to cause transformation, but can do so in cooperation with other genetic events. The cells harboring such events could be easily distinguished by the ability to form foci in confluent cultures. We have identified the accumulation of Raf as one such event: Akt and Raf cooperate in the activation of some downstream components of Raf-dependent signaling. We will investigate the mechanism of the Akt-Raf connection, as well as the essential downstream events in this cooperative process. In the same system we will also use an unbiased genetic screen to identify additional genetic events that may cooperate with activated Akt in oncogenic transformation. We have gained valuable experience with insertional mutagenesis as a foundation for gene discovery projects. We will conduct genome-wide insertional mutagenesis with a modified retroviral vector, which carries a promoter oriented towards the host DNA, driving production of full-length, truncated or anti-sense products of host genes. The vector is engineered to permit excision of the promoter, allowing for unequivocal validation of the promoter insertion as the cause of the transformed phenotype. The insertional events cooperating with Akt in transformation will be identified and the roles of the affected proteins in transformation and differentiation will be studied further, including analysis of direct interaction with Akt and components of the Raf pathway. We will examine the roles of the newly characterized factors in transformation by various oncogenes that are known to up-regulate Akt. The status of these factors in human cancers will be studied using RNA and tissue arrays. In the long run, the project will identify potential targets and markers for cancer therapy and provide the insights into the mechanisms of oncogenic transformation.
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| Singhal, Ruchi; Kandel, Eugene S (2012) The response to PAK1 inhibitor IPA3 distinguishes between cancer cells with mutations in BRAF and Ras oncogenes. Oncotarget 3:700-8 |
| Yang, Jiawen; Battacharya, Partho; Singhal, Ruchi et al. (2011) Xenotropic murine leukemia virus-related virus (XMRV) in prostate cancer cells likely represents a laboratory artifact. Oncotarget 2:358-62 |
| Singhal, Ruchi; Deng, Xiaotao; Chenchik, Alex A et al. (2011) Long-distance effects of insertional mutagenesis. PLoS One 6:e15832 |
| Kichina, Julia V; Goc, Anna; Al-Husein, Belal et al. (2010) PAK1 as a therapeutic target. Expert Opin Ther Targets 14:703-25 |
| Lu, Tao; Jackson, Mark W; Singhi, Aatur D et al. (2009) Validation-based insertional mutagenesis identifies lysine demethylase FBXL11 as a negative regulator of NFkappaB. Proc Natl Acad Sci U S A 106:16339-44 |
| Dong, Beihua; Silverman, Robert H; Kandel, Eugene S (2008) A natural human retrovirus efficiently complements vectors based on murine leukemia virus. PLoS One 3:e3144 |
| Dasgupta, Maupali; Agarwal, Mukesh K; Varley, Patrick et al. (2008) Transposon-based mutagenesis identifies short RIP1 as an activator of NFkappaB. Cell Cycle 7:2249-56 |
| Gartel, Andrei L; Kandel, Eugene S (2008) miRNAs: Little known mediators of oncogenesis. Semin Cancer Biol 18:103-10 |
| Somanath, Payaningal R; Kandel, Eugene S; Hay, Nissim et al. (2007) Akt1 signaling regulates integrin activation, matrix recognition, and fibronectin assembly. J Biol Chem 282:22964-76 |
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