15-deoxy-delta(12-14)-prostaglandin-j2 and Skin-Neoplasms

The effect of prostaglandins on the development of papillomas has been investigated in mice receiving prostaglandins E2 (PGE2) or the cyclopentenone 15-deoxy-delta(12,14)-PGJ2 (15dPGJ2) topically, using the 7,12-dimethylbenz[a]anthracene (DMBA)-induced tetradecanoylphorbol acetate (TPA)-promoted model of skin carcinogenesis. The presence of 15dPGJ2 during DMBA and TPA treatment inhibited apoptosis and increased the rate, number, size and vascularization of the papillomas, some of them progressing into carcinomas. Moreover, skin sections from mice treated for one week with DMBA and 15dPGJ2 showed a much reduced rate of apoptotic cells, and an enhanced expression of vascular epithelial growth factor when compared with animals receiving DMBA, with or without PGE2. The analysis of molecular events in the MCA3D keratinocyte cell line showed that 15dPGJ2 activated Ras and improved cell viability by inhibiting DMBA-dependent apoptosis. In addition to this, cell adhesion was impaired in MCA3D keratinocytes co-treated with 15dPGJ2 and DMBA, at the same time when the expression of cyclooxygenase-2 (COX-2) was observed under these conditions. These effects mediated by 15dPGJ2 might contribute to understand the role of COX-2 metabolites in carcinogenesis, leading to an increase of cell viability after mutagenic injury and therefore in the progression of tumors.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Administration, Topical; Animals; Apoptosis; Carcinogens; Cell Transformation, Neoplastic; Cyclooxygenase 2; Disease Progression; Drug Interactions; Female; Immunologic Factors; Keratinocytes; Mice; Papilloma; Prostaglandin D2; Skin Neoplasms

The novel synthetic oleanane triterpenoid CDDO (2-cyano-3, 12-dioxoolean-1, 9-dien-28-oic acid) can serve as a ligand for the peroxisome proliferator activator receptor-gamma (PPAR-gamma) and has been shown to inhibit cell proliferation, and to induce differentiation and apoptosis in tumor cell lines. Bexarotene is an RXR-selective retinoid that can induce apoptosis of mycosis fungoides (MF) and Sézary syndrome (SS) cells. Since the PPAR-gamma and RXR receptors can form heterodimers, we studied the effects of CDDO and its synergism with bexarotene on apoptosis in MF/SS cell lines (MJ, Hut78, and HH) and freshly isolated peripheral blood lymphocytes (PBL) from SS patients with circulating atypical T cells (CD4+CD26-). CDDO treatment at 1-5 microM for 48 h caused a concentration-dependent apoptosis in three MF/SS cell lines and patients' PBL compared to vehicle controls. Bexarotene augmented CDDO-induced apoptosis in these cells. PPAR-gamma was expressed but decreased by 47% in MJ, 42% in Hut78, and 77% in HH cells following CDDO treatment. The anti-apoptotic protein bcl-xL, but not bcl-2, was decreased by 69% in MJ, 31% in Hut78, and 59% in HH cells and caspase-3 was activated following CDDO treatment. Interestingly, the PPAR-gamma antagonist T007 did not block CDDO-induced apoptosis, and the more potent PPAR-gamma agonist rosiglitazone required much higher concentrations (>50 microM) than CDDO to induce apoptosis in MF/SS cells. In summary, CDDO induces apoptosis that is further enhanced by bexarotene and decreases the PPAR-gamma and bcl-xL proteins in MF/SS cells. CDDO's effects on MF/SS cells may be at least partly mediated through a PPAR-gamma-independent mechanism. Our findings suggest the rationale for further investigation of the clinical potential of CDDO, either alone or in combination with bexarotene for MF/SS patients.

Topics: Anticarcinogenic Agents; Apoptosis; Bexarotene; Cell Division; Cell Line, Tumor; Drug Synergism; Humans; Immunologic Factors; Ligands; Lymphocytes; Mycosis Fungoides; Nitric Oxide; Oleanolic Acid; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; Sezary Syndrome; Skin Neoplasms; Tetrahydronaphthalenes; Transcription Factors

Peroxisome proliferator-activated receptor gamma is a member of the nuclear receptor superfamily involved in adipocyte differentiation and glucose homeostasis. There is evidence that peroxisome proliferator-activated receptor gamma may also act as a tumor suppressor. Here, we demonstrate expression of peroxisome proliferator-activated receptor gamma in benign melanocytic naevi, different variants of primary cutaneous melanomas, and melanoma metastases. Peroxisome proliferator-activated receptor gamma protein and peroxisome proliferator-activated receptor gamma1 mRNA were also detected in human melanoma cell lines. The peroxisome proliferator-activated receptor gamma specific agonists 15-deoxy-Delta12,14-prostaglandin J2, troglitazone, and rosiglitazone dose-dependently inhibited cell proliferation in four melanoma cell lines, whereas a specific agonist of peroxisome proliferator-activated receptor alpha had no such effect. At a concentration of 50 microM rosiglitazone, the most potent peroxisome proliferator-activated receptor gamma agonist tested suppressed cell growth by approximately 90%. Apoptosis could be induced in melanoma cell lines by incubation with tumor-necrosis-factor-related apoptosis-inducing ligand. In contrast, the growth inhibitory effect of peroxisome proliferator-activated receptor gamma activation was independent of apoptosis and seemed to occur primarily through induction of cell cycle arrest. Our data indicate that melanoma cell growth may be modulated through peroxisome proliferator-activated receptor gamma.

Topics: Antineoplastic Agents; Apoptosis; Cell Division; Chromans; Dose-Response Relationship, Drug; Fibrinolytic Agents; Gene Expression Regulation, Neoplastic; Humans; Immunologic Factors; Melanoma; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Rosiglitazone; Skin Neoplasms; Thiazoles; Thiazolidinediones; Transcription Factors; Troglitazone; Tumor Cells, Cultured