PROGRAMM JAHRESTAGUNG 2012 30. Nov. – 2. Dez ... - ÖGDV

Freie Vorträge
FV 6
Combined targeting of MEK and PI3K/mTOR pathways effectively inhibits NRAS
mutant melanoma in vitro and in vivo
Christian Posch 1,2
Homayoun Moslehi 1
Luzviminda Feeney 1
Anoosheh Abaee 1
Lily Peng 1
Gary Green 1
Valentin Feichtenschlager 2
Philip LeBoit 1
Susana Ortiz 1
1 University of California San Francisco Department of Dermatology Mt. Zion Cancer
Research Center 2340 Sutter Street N461, San Francisco CA-94115, USA
2 Krankenanstalt Rudolfstiftung Abteilung für Dermatologie und Venerologie,
Juchgasse 25, 1030 Wien
Introduction: Activating mutations in the NRAS gene are among the most common
genetics events in malignant melanoma being found in 15-25% of melanomas. Mutated
NRAS proteins activate signaling pathways that promote the cell division cycle and cell
growth and suppress apoptosis. However, efforts at developing therapeutics that inhibit
mutant RAS directly have so far not been very successful. We investigated the effects
of blocking two major downstream signaling pathways of mutant NRAS, the
RAS/RAF/ERK and the PI3K/AKT/mTOR pathway with currently available inhibitors.
Material and Methods: Immunohistochemistry was used to analyze 14 primary
melanomas and 18 melanoma metastases for phospho-protein levels in the
RAS/RAF/ERK and the PI3K/AKT/mTOR cascade. We further evaluated the influence of
different components of the MEK and PI3K/mTOR cascade in a large set of NRAS mutant
melanoma cell lines employing a pool of single and combined inhibitors. Statistical and
mathematical models were used to calculate synergistic effects of inhibitor
combinations. Cell viability and apoptosis assays as well as kinome array analysis were
performed. Results were translated into a xenograft mouse model of NRAS mutant
melanoma.
Results: We found that combined targeting of MEK, PI3K and mTOR pathways is
necessary to effectively inhibit NRAS mutant melanoma cells. We learned that mTORC2
inhibition is more powerful in reducing cell growth than inhibition of mTORC1.
Comparing the inhibitory effects of selective mTOR and PI3K inhibitors we observed,
that dual inhibitors of PI3K and mTOR were generally more powerful in reducing cell
growth than selective mTOR and PI3K inhibitors alone or in combination. The
combination of MEK/PI3K was superior to MEK/mTOR in all NRAS mutant melanoma
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