Ingenol 3-Angelate

The seeds of Euphorbia lathyris L.

Ingenol Mebutate is an active ingredient in Euphorbia peplus, acts as a potent PKC modulator, with Kis of 0.3, 0.105, 0.162, 0.376, and 0.171 nM for PKC-α, PKC-β, PKC-γ, PKC-δ, and PKC-ε, respectively, and has antiinflammatory and antitumor activity.

In Vitro:Ingenol Mebutate (Ingenol 3-angelate) is an active ingredient in Euphorbia peplus, acting as a potent PKC activator, with Kis of 0.3, 0.105, 0.162, 0.376, and 0.171 nM for PKC-α, PKC-β, PKC-γ, PKC-δ, and PKC-ε, respectively. Ingenol Mebutate also EC50s of 13 ± 2.4 nM (PKC-α), 4.37 ± 0.4 nM (PKC-βI), 10.5 ± 2.2 nM (PKC-βII), 38.6 ± 2.9 nM (PKC-δ), 1.08 ± 0.01 nM (PKC-ε), 0.9 ± 0.13 nM (PKC-μ) in WEHI-231 cells, 198 ± 12.5 nM (PKC-α), 69.1 ± 8.2 nM (PKC-βI), 4.6 ± 0.4 nM (PKC-ε) and 1 nM (PKC-μ) in HOP-92 cells, 635 ± 245 nM (PKC-α), 146 ± 35 nM (PKC-βI), 4.7 ± 0.7 nM (PKC-δ), 1.1 ± 0.5 nM (PKC-ε), and 30 nM (PKC-μ) in Colo-205 cells. Ingenol Mebutate sensitizes WEHI-231 cells, HOP-92 and Colo-205 cells, with IC50s of 1.41 ± 0.255 nM, 3.24 ± 2.01 nM, and 11.9 ± 1.307 nM, respectively[1]. Ingenol Mebutate (PEP005; 20 nM) actions are PKC-δ dependent, induces apoptosis in primary AML marrow blasts but not in normal myeloblasts[2]. Ingenol Mebutate (PEP005) activates PKCδ and inhibits PKCα. Colo205-R cells (IC50: >10 μM) are >300-fold more resistant to Ingenol Mebutate than parental Colo205-S cells[3].

References:
[1]. Kedei N, et al. Characterization of the interaction of ingenol 3-angelate with protein kinase C. Cancer Res. 2004 May 1;64(9):3243-55. [2]. Hampson P, et al. PEP005, a selective small-molecule activator of protein kinase C, has potent antileukemic activity mediated via the delta isoform of PKC. Blood. 2005 Aug 15;106(4):1362-8. [3]. Ghoul A, et al. Epithelial-to-mesenchymal transition and resistance to ingenol 3-angelate, a novel protein kinase C modulator, in colon cancer cells. Cancer Res. 2009 May 15;69(10):4260-9.

Novel antileukemic compound ingenol 3-angelate inhibits T cell apoptosis by activating protein kinase Ctheta.[Pubmed:20472553]

J Biol Chem. 2010 Jul 30;285(31):23889-98.

Members of the protein kinase C (PKC) family of serine-threonine kinases are important regulators of immune cell survival. Ingenol 3-Angelate (PEP005) activates a broad range of PKC isoforms and induces apoptosis in acute myeloid leukemia cells by activating the PKC isoform PKCdelta. We show here that, in contrast to its effect on leukemic cells, PEP005 provides a strong survival signal to resting and activated human T cells. The antiapoptotic effect depends upon the activation of PKC. This PKC isoform is expressed in T cells but is absent in myeloid cells. Further studies of the mechanism involved in this process showed that PEP005 inhibited activated CD8(+) T cell apoptosis through the activation of NFkappaB downstream of PKC, leading to increased expression of the antiapoptotic proteins Mcl-1 and Bcl-x(L). Transfection of CD8(+) T cells with dominant-negative PKC diminished the prosurvival effect of PEP005 significantly. Ectopic expression of PKC in the acute myeloid leukemia cell line NB4 turned their response to PEP005 from an increased to decreased rate of apoptosis. Therefore, in contrast to myeloid leukemia cells, PEP005 provides a strong survival signal to T cells, and the expression of functional PKC influences whether PKC activation leads to an anti- or proapoptotic outcome in the cell types tested.

The skin cancer chemotherapeutic agent ingenol-3-angelate (PEP005) is a substrate for the epidermal multidrug transporter (ABCB1) and targets tumor vasculature.[Pubmed:20460505]

Cancer Res. 2010 Jun 1;70(11):4509-19.

Ingenol-3-angelate (Ing3A), extracted from Euphorbia peplus, is currently in clinical trials for eradicating basal cell carcinoma, actinic keratosis, and squamous cell carcinoma (SCC) in situ by topical application. Although structurally related to phorbol esters and a protein kinase C activator, topical Ing3A, but not phorbol 12-myristate 13-acetate (PMA), inhibited the growth of subcutaneous tumors derived from PAM212 (mouse SCC) and B16 (mouse melanoma). Ing3A and PMA both induced acute neutrophilic inflammation on mouse skin, but only Ing3A caused subcutaneous hemorrhage and vascular damage. Both Ing3A and PMA activated extracellular signal-regulated kinase 1/2 (ERK1/2) in epidermis, but Ing3A also activated ERK1/2 in skin dermal fibroblasts and endothelial cells. Pretreatment with topical cyclosporin A (CsA), verapamil, or XR9576, modulators of P-glycoprotein (P-gp), prevented Ing3A-induced hemorrhage but not neutrophil infiltration. CsA also impaired the anticancer activity of Ing3A, whereas the anti-inflammatory dexamethasone did not. Ing3A, but not PMA, blocked photoaffinity labeling of human P-gp with [(125)I]iodoaryazidoprazosin and inhibited P-gp-mediated drug resistance to HCT-15 cells. The intracellular levels of Ing3A were significantly lower in P-gp-expressing cells, and treatment with XR9576 increased the levels to those of cells that do not express P-gp, showing that Ing3A binds to and is transported by P-gp. Taken together, our results suggest that P-gp-mediated absorptive transport, dermal penetration, and vascular damage contribute to the anticancer activity of Ing3A in vivo.

Synergistic Reactivation of Latent HIV Expression by Ingenol-3-Angelate, PEP005, Targeted NF-kB Signaling in Combination with JQ1 Induced p-TEFb Activation.[Pubmed:26225771]

PLoS Pathog. 2015 Jul 30;11(7):e1005066.

Although anti-retroviral therapy (ART) is highly effective in suppressing HIV replication, it fails to eradicate the virus from HIV-infected individuals. Stable latent HIV reservoirs are rapidly established early after HIV infection. Therefore, effective strategies for eradication of the HIV reservoirs are urgently needed. We report that ingenol-3-angelate (PEP005), the only active component in a previously FDA approved drug (PICATO) for the topical treatment of precancerous actinic keratosis, can effectively reactivate latent HIV in vitro and ex vivo with relatively low cellular toxicity. Biochemical analysis showed that PEP005 reactivated latent HIV through the induction of the pS643/S676-PKCdelta/theta-IkappaBalpha/epsilon-NF-kappaB signaling pathway. Importantly, PEP005 alone was sufficient to induce expression of fully elongated and processed HIV RNAs in primary CD4+ T cells from HIV infected individuals receiving suppressive ART. Furthermore, PEP005 and the P-TEFb agonist, JQ1, exhibited synergism in reactivation of latent HIV with a combined effect that is 7.5-fold higher than the effect of PEP005 alone. Conversely, PEP005 suppressed HIV infection of primary CD4+ T cells through down-modulation of cell surface expression of HIV co-receptors. This anti-cancer compound is a potential candidate for advancing HIV eradication strategies.

Immunostimulatory cancer chemotherapy using local ingenol-3-angelate and synergy with immunotherapies.[Pubmed:19428919]

Vaccine. 2009 May 18;27(23):3053-62.

Ingenol-3-angelate is a new local chemotherapeutic agent in clinical trails that induces primary necrosis of tumour cells and transient local inflammation. Here we show that cure of subcutaneous tumours with ingenol-3-angelate (PEP005) resulted in the generation of anti-cancer CD8 T cells that could regress metastases. Furthermore, PEP005-mediated cure synergized with several CD8 T cell-based immunotherapies to regress further distant metastases. PEP005 was shown to have adjuvant properties, being able to upregulate CD80 and CD86 expression on dendritic cells in vivo, and to promote CD8 T cell induction when co-delivered with a protein antigen. PEP005 thus emerges as a unique local chemotherapeutic immunostimulatory debulking agent that could be used in conjunction with immunotherapies to promote regression of metastases.

Antiproliferative activity of PEP005, a novel ingenol angelate that modulates PKC functions, alone and in combination with cytotoxic agents in human colon cancer cells.[Pubmed:19034280]

Br J Cancer. 2008 Dec 2;99(11):1808-15.

PEP005 is a novel ingenol angelate that modulates protein kinases C (PKC) functions by activating PKC delta and inhibiting PKC alpha. This study assessed the antiproliferative effects of PEP005 alone and in combination with several other anticancer agents in a panel of 10 human cancer cell lines characterised for expression of several PKC isoforms. PEP005 displayed antiproliferative effects at clinically relevant concentrations with a unique cytotoxicity profile that differs from that of most other investigated cytotoxic agents, including staurosporine. In a subset of colon cancer cells, the IC(50) of PEP005 ranged from 0.01-140 microM. The antiproliferative effects of PEP005 were shown to be concentration- and time-dependent. In Colo205 cells, apoptosis induction was observed at concentrations ranging from 0.03 to 3 microM. Exposure to PEP005 also induced accumulation of cells in the G1 phase of the cell cycle. In addition, PEP005 increased the phosphorylation of PKC delta and p38. In Colo205 cells, combinations of PEP005 with several cytotoxic agents including oxaliplatin, SN38, 5FU, gemcitabine, doxorubicin, vinorelbine, and docetaxel yielded sequence-dependent antiproliferative effects. Cell cycle blockage induced by PEP005 in late G1 lasted for up to 24 h and therefore a 24 h lag-time between PEP005 and subsequent exposure to cytotoxics was required to optimise PEP005 combinations with several anticancer agents. These data support further evaluation of PEP005 as an anticancer agent and may help to optimise clinical trials with PEP005-based combinations in patients with solid tumours.

PEP005, a selective small-molecule activator of protein kinase C, has potent antileukemic activity mediated via the delta isoform of PKC.[Pubmed:15845901]

Blood. 2005 Aug 15;106(4):1362-8.

Ingenol 3-Angelate (PEP005) is a selective small molecule activator of protein kinase C (PKC) extracted from the plant Euphorbia peplus, whose sap has been used as a traditional medicine for the treatment of skin conditions including warts and cancer. We report here that PEP005 also has potent antileukemic effects, inducing apoptosis in myeloid leukemia cell lines and primary acute myeloid leukemia (AML) cells at nanomolar concentrations. Of importance, PEP005 did not induce apoptosis in normal CD34+ cord blood myeloblasts at up to 2-log concentrations higher than those required to induce cell death in primary AML cells. The effects of PEP005 were PKC dependent, and PEP005 efficacy correlated with expression of PKC-delta. The delta isoform of PKC plays a key role in apoptosis and is therefore a rational potential target for antileukemic therapies. Transfection of KG1a leukemia cells, which did not express PKC-delta or respond to PEP005, with enhanced green fluorescent protein (EGFP)-PKC-delta restored sensitivity to induction of apoptosis by PEP005. Our data therefore suggest that activation of PKC-delta provides a novel approach for treatment of acute myeloid leukemia and that screening for PKC-delta expression may identify patients for potential responsiveness to PEP005.

Ingenol Mebutate is an active ingredient in Euphorbia peplus, acts as a potent PKC modulator, with Kis of 0.3, 0.105, 0.162, 0.376, and 0.171 nM for PKC-α, PKC-β, PKC-γ, PKC-δ, and PKC-ε, respectively, and has antiinflammatory and antitumor activity.

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