Abstract 3049: Pathways of transformation in Kit-activated melanoma

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL KIT-activated melanoma is a recently recognized distinct genetic form of melanoma characterized by constitutively activating KIT mutations. To understand the biology of KIT-activated melanoma, we sought to develop both in vitro and in vivo models. Mouse Kit L575P, the orthologue of human KIT L576P, a common KIT mutation found in human melanoma, was expressed in an immortalized but non-transformed mouse Ink4a/Arf-deficient melanocyte cell line. The resultant Kit L575P cell line exhibited increased proliferation, the ability to grow in soft agar and increased migration, indicating that the cells had been transformed by Kit L575P. Furthermore, when Kit L575P cells were injected subcutaneously into NOD/SCID/gamma(c) mice, tumors with all of the histological and clinical hallmarks of melanomas arose in 5 of 7 (71%) mice, while control cells harboring wild-type Kit failed to develop tumors. In addition to a subcutaneous tumor, 1 of 7 mice (14%) injected with Kit L575P cells developed metastatic disease to liver and lungs. Evaluation of signal transduction pathways downstream of constitutively activated Kit L575P revealed striking activation of the phosphatidyl inositol 3-kinase (PI3K) pathway. Inhibition of the PI3K pathway pharmacologically with the PI3K inhibitor LY294002 or genetically by engineering a second Kit mutation (Y719F) which abrogated binding of Kit L575P to the p85α subunit of PI3K, abolished the transformation phenotypes gained in the L575P single mutant. These studies validate this Kit L575P-activated model of melanoma and establish the PI3K pathway as a dominant signaling pathway downstream of Kit in melanoma. This model should be of further use in the pre-clinical evaluation of various therapeutic strategies in Kit-activated melanoma and for studying different aspects of the biology of Kit-activated melanoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3049. doi:10.1158/1538-7445.AM2011-3049