Abstract 863: Tyrosine kinase activity profiling of metastatic malignant melanoma: Identification of possible therapeutic targets and markers predicting response to therapy

Abstract

Abstract Metastatic melanoma is an aggressive form of skin cancer that is highly resistant to conventional chemotherapy. Thus, novel approaches to improve the current treatment of advanced melanoma are urgently needed. Kinases are key regulators of cellular processes, and since nearly half of the tyrosine kinase complement is implicated in cancer, the information of kinase activity in tumors give important tumor-specific information on affected pathways and potential targets for treatment. With this in mind, we performed tyrosine kinase activity profiling of 26 tissue samples obtained from patients suffering from metastatic stage IV melanoma, prior to dacarbazine (DTIC) treatment, using Tyrosine Kinase PamChip® microarrays. Each sample lysate generated an individual phospho-substrate signature, representing the state of the kinase signalling cascades, which allowed us to compare affected targets in responders and non-responders to DTIC treatment. Further, we attempted to evaluate the kinase activity in response to BRAF inhibitor, PLX4032 (Vemurafenib), which has shown dramatic and positive effects in advanced melanoma tumors, and has recently been approved for the treatment of late stage melanoma. In this case, incubation was carried out on all samples with and without PLX4032. Our preliminary results showed that although the compound is mainly directed against a serine/threonine kinase, BRAF, PLX4032 also showed inhibitory effects on the activity of multiple tyrosine kinases. Since the drug is only beneficial for melanoma patients with BRAF V600E mutations, we compared the activated kinase pathways in patients with and without this mutation in order to identify alternative survival pathways in patients with wild type BRAF. The technology used in this study is based on a unique 3D flow-through microarray format that allows monitoring of the reaction in real time, ideal for the characterization of pathways. Each array contained 144 peptide substrates with sites for phosphorylation, representing about 100 different proteins. The use of kinase inhibitors will cause inhibition of corresponding kinases of activated signalling pathways; hence, providing us leads to therapeutic targets and possible prediction markers for response to therapy. The detailed effects of both PLX4032 and sunitinib in the chosen test system are currently prepared for presentation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 863. doi:1538-7445.AM2012-863