Effects of protein kinase C modulation by PEP005, a novel ingenol angelate, on mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling in cancer cells

Abstract

PEP005 (ingenol-3-angelate) is a novel anticancer agent extracted from Euphorbia peplus that was previously shown to modulate protein kinase C (PKC), resulting in antiproliferative and proapoptotic effects in several human cancer cell lines. In Colo205 colon cancer cells, exposure to PEP005 induced a time-and concentration-dependent decrease of cells in S phase of cell cycle and apoptosis. In Colo205 cells exposed to PEP005, a variety of signaling pathways were activated as shown by increased phosphorylation of PKCD, Raf1, extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (MAPK), c-Jun NH 2 -terminal kinase, p38 MAPK, and PTEN. PEP005-induced activation of PKCD was associated with its translocation from the cytosol to the nucleus and other cellular membranes. Interestingly, PEP005 treatment also resulted in reduced expression of PKCA and reduced levels of phosphorylated active form of AKT/protein kinase B. These data suggest that PEP005-induced activation of PKCD and reduced expression of PKCA resulted in apoptosis by mechanisms mediated by activation of Ras/Raf/MAPK and inhibition of the phosphatidylinositol 3-kinase/AKT signaling pathways. This study supports ongoing efforts targeting PKC isoforms in cancer therapy with PEP005 alone and in combination with other cytotoxic agents. [Mol Cancer Ther 2008;7(4):915 -22]

Antiproliferative activity of PEP005, a novel ingenol angelate that modulates PKC functions, alone and in combination with cytotoxic agents in human colon cancer cells

“…We first evaluated the expression of PKC isoforms a, b, d, and e in a panel of 10 human cancer cell lines representing common human cancers (breast, lung, colon, and ovarian cancer (Serova et al, 2008). As expected from our previous results, we observed that exposure of Colo205 cells to 3 mM PEP005 for 20 min increased the phosphorylation of PKCd and activated p38 ( Figure 2B).…”

“…In this study, we found no correlation between PKC isoforms expression and the antiproliferative effects of PEP005. We previously showed that MAPK and inhibition of PI3K/AKT pathways in Colo205 cells (Serova et al, 2008). In contrast, in the HT29 resistant cell line, no activation of PKCd, MAPK, or AKT was detectable.…”

“…In addition, PEP005 induced cell senescence (Cozzi et al, 2006). We have recently tested the antiproliferative effects of PEP005 in several human cancer cell lines and we have shown that PEP005 may induce apoptosis in colon cancer cell lines at clinically relevant concentrations (Serova et al, 2008). We found that the antiproliferative effects were related to cell cycle inhibition in the G1 phase as well as the induction of apoptosis.…”

“…PEP005 is currently being developed as a topical treatment for actinic keratoses and basal cell carcinoma (www.cancertrials.gov). In earlier studies, PEP005 Revised 4 August 2008; accepted 6 August 2008 was shown to modulate PKCs by activating PKCd in human myeloid leukaemia cancer cell lines, thereby inducing cellular apoptosis (Hampson et al, 2005) in melanoma models, inducing senescence through PKC-mediated activation of the MAPK pathway (Cozzi et al, 2006) and in colon cancer models, inducing apoptosis through the inhibition of the AKT signalling pathway (Serova et al, 2008). PEP005 appears to be selective for growth inhibition of cancer cells as it does not inhibit the growth of human neonatal fibroblasts (Cozzi et al, 2006) and does not induce apoptosis in normal CD34 þ cord blood myeloblasts (Hampson et al, 2005).…”

Epithelial-to-Mesenchymal Transition and Resistance to Ingenol 3-Angelate, a Novel Protein Kinase C Modulator, in Colon Cancer Cells

“…PEP005 (ingenol 3-angelate), a small molecule extracted from Euphorbia peplus (21), was initially developed as a topical treatment for actinic keratosis or basal cell skin carcinoma and was recently proposed for the treatment of acute myeloid leukemias. PEP005 was shown to inhibit PKCa and to activate PKCy translocation to cytoplasmic and nuclear membranes in leukemia (21,22) and in colon cancer models, inducing apoptosis through inhibition of the AKT signaling pathway (23).…”