60P - MAPKAP1/SIN1: A promising therapeutic target in resistant BRAF-mutated melanoma

Background

The PI3K/AKT/mTOR pathway plays a major role in melanoma pathogenesis and is also involved in resistance to targeted therapies (TT). The mTORC2 complex plays an important role in this pathway allowing activation of AKT and contributes to the development of BRAF-mutated (BRAFm) melanomas and their resistance to treatments. Once activated, AKT phosphorylates several effector proteins, thus regulating multiple key cellular processes, including proliferation, survival, motility, metabolism and angiogenesis.The goal of our project is to study this complex in melanoma in order to target it specifically. For this purpose, we are focusing more particularly on one principal protein of this complex: SIN1 (also called MAPKAP1) involved in the stabilizing of mTORC2 complex, in its substrate’s specificity, and a major player in the total activation of AKT.

Methods

We are analysing SIN1 expression, by quantitative RT-PCR and IHC and its interaction with other proteins, by Proximity Ligation Assay (PLA), in situ in melanoma biopsies of the French national MELBASE cohort. We will correlate these results with clinico-biological data from MELBASE to determine if there is a diagnostic or prognostic value of these analyses. In a second step, we are mapping the minimal domain of SIN1/NRAS interaction by Peptide Array to develop cell-permeable peptides to inhibit NRAS/mTORC2 interaction. Furthermore, we are evaluating whether SIN1 has also functions independent of the mTORC2 complex in melanoma, by searching for other partners of SIN1 by PLA in melanoma lines.

Results

Our preliminary results show that mTORC2 interacts with NRAS in BRAFm melanoma and that inhibiting the NRAS/mTORC2 interaction reduces the proliferation of melanoma cell lines and in particular those resistant to TT. This leads us to develop inhibitors to specifically target resistant melanomas.

Conclusions

The results of this project will provide us a better understanding of the mTORC2 signalling pathway in the development of BRAFm melanoma and its response to TT. Given the lack of a specific mTORC2 inhibitor at this time, SIN1 could be an ideal therapeutic target to aim for mTORC2.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Fondation ARC.

Disclosure

All authors have declared no conflicts of interest.