Topical Treatment with Inhibitors of the Phosphatidylinositol 3′-Kinase/Akt and Raf/Mitogen-Activated Protein Kinase Kinase/Extracellular Signal-Regulated Kinase Pathways Reduces Melanoma Development in Severe Combined Immunodeficient Mice

Abstract

Topical treatment with inhibitors of the phosphatidylinositol 3-kinase/ Akt and Raf/mitogen-activated protein kinase kinase/extracellular signalregulated kinase pathways inhibited the growth of TPras transgenic melanomas in severe combined immunodeficient mice, blocked invasive behavior, and reduced angiogenesis. The inhibitor Ly294002, which is specific for phosphatidylinositol 3-kinase, effectively reduced melanoma cell growth both in vitro and in vivo. Both Ly294002 and U0126, a mitogen-activated protein kinase kinase 1/2 inhibitor, reduced invasion, which correlated with reduction of the metalloproteinase matrix metalloproteinase 2. Tumor angiogenesis was disrupted through inhibition of vascular endothelial growth factor production from the tumor cells and antiangiogenic effects on endothelial cells. Observations with TPras melanoma cells that express dominant negative ⌬p85 or kinase-inactive Raf 301 supported the specificity of the phenomena observed with the chemical inhibitors. These studies demonstrate that topical treatment targeting Ras effectors is efficacious, without systemic toxicities, and may prove to be useful in treating and preventing the progression of cutaneous melanoma.

Notch1 is an effector of Akt and hypoxia in melanoma development

“…Major signaling pathways altered in melanoma include the Ras pathway and downstream effectors BRaf/MEK/Erks and PTEN/PI3K/Akt (32,33). It was previously shown that active Notch1 (i.e., Notch1-N IC ) can promote melanoma progression by activating both the PI3K/ Akt and the Raf/MEK pathways (21).…”

Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer

“…After 24 h, the cells were subjected to hypoxia treatment for 24 h and were colleted for total RNA, protein extraction, or for luciferase assays. In the experiments to define the relationship between hypoxia and Akt regulation of OPN expression, the constitutively active Akt (pWZLneo-Akt) (Kohn et al, 1996) and the PI3 kinase dominant negative mutant (Dp85) (Bedogni et al, 2004) were used.…”

Integrating BRAF/MEK inhibitors into combination therapy for melanoma

“…There is preclinical evidence to suggest that there is a synergistic anti-melanoma activity when MEK and PI3K/AKT are inhibited concomitantly. Thus, the topical application of U0126 and LY294002 led to the regression of xenografts in a TPRas-induced melanoma model (Bedogni et al, 2004) associated with increased apoptosis and a reduced angiogenic response. Other studies have shown that PI3K and MEK inhibitors synergise to reduce growth and survival of melanoma cell lines grown under 3D organotypic cell culture conditions Meier et al, 2007).…”