mTOR inhibitor everolimus reduces invasiveness of melanoma cells

The mammalian target of rapamycin (mTOR) plays a key role in several cellular processes: proliferation, survival, invasion, and angiogenesis, and therefore, controls cell behavior both in health and in disease. Dysregulation of the mTOR signaling is involved in some of the cancer hallmarks, and thus the mTOR pathway is an important target for the development of a new anticancer therapy. The object of this study is recognition of the possible role of mTOR kinase inhibitors-everolimus single and in combination with selected downstream protein kinases inhibitors: LY294002 (PI3 K), U0126 (ERK1/2), GDC-0879 (B-RAF), AS-703026 (MEK), MK-2206 (AKT), PLX-4032 (B-RRAF) in cell invasion in malignant melanoma. Treatment of melanoma cells with everolimus led to a significant decrease in the level of both phosphorylated: mTOR (Ser2448) and mTOR (Ser2481) as well as their downstream effectors. The use of protein kinase inhibitors produced a significant decrease in metalloproteinases (MMPs) activity, as well as diminished invasion, especially when used in combination. The best results in the inhibition of both MMPs and cell invasiveness were obtained for the combination of an mTOR inhibitor- everolimus with a B-RAF inhibitor-PLX-4032. Slightly less profound reduction of invasiveness was obtained for the combinations of an mTOR inhibitor-everolimus with ERK1/2 inhibitor-U126 or MEK inhibitor-AS-703026 and in the case of MMPs activity decrease for PI3 K inhibitor-LY294002 and AKT inhibitor-MK-2206. The simultaneous use of everolimus or another new generation rapalog with selected inhibitors of crucial signaling kinases seems to be a promising concept in cancer treatment.