SR 11302

SR 11302 is an inhibitor of activator protein-1 (AP-1) [1].AP-1 is a transcription factor that displays antitumor effects in vivo.
SR 11302 is an inhibitor of AP-1 but don’t activate RARs and RXR. SR11302 failed to inhibit the proliferation of F9 cells, the embryonal carcinoma cell line. While, it can inhibit the growth of breast cancer cell line T-47D, the lung cancer line Calu-6 and HeLa cells[1]. SR 11302 had very little effect on either the proliferation or the differentiation of HL-60, fresh APL and NB4 cells, which indicate that AP-1 may not be involved in the signaling pathway of proliferation and differentiation of HL-60, fresh APL and NB4 cells [2].
In an AP-1-luciferase transgenic mouse carcinogenesis model, SR11302 significantly inhibit both AP-1 activation in 7,12-dimethyl benz(a)anthracene-initiated mouse skin and 12-O-tetradecanoylphorbol-13-acetate-induced papilloma formation. While, SR11235, a retinoid with RARE transactivating activity, but lack of AP-1 inhibiting effect, didn’t inhibit papilloma formation and AP-1 activation. These results show that the antitumor effect of retinoids is mediated by blocking AP-1 activity in vivo [3].
References:
[1]. Fanjul A, Dawson MI, Hobbs PD, et al. A new class of retinoids with selective inhibition of AP-1 inhibits proliferation. Nature, 1994, 372(6501): 107-111.
[2]. Shiohara M, Dawson MI, Hobbs PD, et al. Effects of novel RAR- and RXR-selective retinoids on myeloid leukemic proliferation and differentiation in vitro. Blood, 1999, 93(6): 2057-2066.
[3]. Huang C, Ma WY, Dawson MI, et al. Blocking activator protein-1 activity, but not activating retinoic acid response element, is required for the antitumor promotion effect of retinoic acid. Proc Natl Acad Sci U S A, 1997, 94(11): 5826-5830.

AP-1 Inhibition by SR 11302 Protects Human Hepatoma HepG2 Cells from Bile Acid-Induced Cytotoxicity by Restoring the NOS-3 Expression.[Pubmed:27490694]

PLoS One. 2016 Aug 4;11(8):e0160525.

The harmful effects of bile acid accumulation occurring during cholestatic liver diseases have been associated with oxidative stress increase and endothelial nitric oxide synthase (NOS-3) expression decrease in liver cells. We have previously reported that glycochenodeoxycholic acid (GCDCA) down-regulates gene expression by increasing SP1 binding to the NOS-3 promoter in an oxidative stress dependent manner. In the present study, we aimed to investigate the role of transcription factor (TF) AP-1 on the NOS-3 deregulation during GCDCA-induced cholestasis. The cytotoxic response to GCDCA was characterized by 1) the increased expression and activation of TFs cJun and c-Fos; 2) a higher binding capability of these at position -666 of the NOS-3 promoter; 3) a decrease of the transcriptional activity of the promoter and the expression and activity of NOS-3; and 4) the expression increase of cyclin D1. Specific inhibition of AP-1 by the retinoid SR 11302 counteracted the cytotoxic effects induced by GCDCA while promoting NOS-3 expression recovery and cyclin D1 reduction. NOS activity inhibition by L-NAME inhibited the protective effect of SR 11302. Inducible NOS isoform was no detected in this experimental model of cholestasis. Our data provide direct evidence for the involvement of AP-1 in the NOS-3 expression regulation during cholestasis and define a critical role for NOS-3 in regulating the expression of cyclin D1 during the cell damage induced by bile acids. AP-1 appears as a potential therapeutic target in cholestatic liver diseases given its role as a transcriptional repressor of NOS-3.

Effects of novel RAR- and RXR-selective retinoids on myeloid leukemic proliferation and differentiation in vitro.[Pubmed:10068679]

Blood. 1999 Mar 15;93(6):2057-66.

Retinoids such as all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid (9-cis-RA) have an important role in many aspects of proliferation and differentiation of hematopoietic cells. They exert their effects by binding to retinoic acid receptors (RARs) and/or retinoid X receptors (RXRs). We studied the effects of novel retinoids on proliferation and differentiation of HL-60 and NB4 myeloid leukemic cells, as well as acute promyelocytic leukemia (APL) cells from patients. RXR-selective SR11345 (Retinoid C) had little ability to inhibit the clonal growth and to induce the differentiation of either HL-60 or NB4 cells. However, SR11276 (Retinoid E), which activated both the RAR and RXR classes, and SR11278 (Retinoid D), which activated the RAR subtypes alpha, beta, and gamma, could inhibit clonal growth of both cell types, as well as leukemic cells from APL patients. The combination of ATRA and either SR11276 or SR11278 additively inhibited APL cell proliferation. SR11302 (Retinoid A), with reported anti-AP-1 activity and no activation of RARs and RXR and SR11363 (Retinoid B), which selectively activated RARbeta and gamma, were inactive. The clonal proliferation of both HL-60 and NB4 cells that were pulse-exposed to 10(-9) mol/L ATRA, SR11276, SR11278, or SR11345 for 3 days, washed, and plated in methylcellulose culture were inhibited by 0%, 51%, 21%, and 1% for HL-60 cells and 43%, 41%, 35%, and 1% for NB4, respectively, compared with nontreated control cells. When the HL-60 cells were pulse-exposed to 10(-9) mol/L of either SR11278 or SR11276, plus 10(-9) mol/L ATRA for 3 days, colony numbers were reduced by 46% and 64%, respectively. Induction of leukemic cell differentiation as determined by the nitroblue tetrazolium (NBT) assay showed that the combination of 10(-7) mol/L of either SR11278 or SR11276 with 10(-7) mol/L ATRA had additive effects on HL-60 cells, NB4 cells, and fresh APL cells. Induction of CD11b expression on both HL-60 and NB4 cells occurs during their differentiation. Expression of this antigen was synergistically augmented by the combination of either 10(-7) to 10(-8) mol/L SR11278 or 10(-7) to 10(-9) mol/L SR11276 with 10(-9) mol/L ATRA compared with either analog alone in HL-60 cells. Expression of the novel myeloid specific transcription factor C/EBPepsilon was increased by SR11278 and SR11276 in both the HL-60 and NB4 cell lines. We conclude that retinoids or combination of retinoids with specificities for both RAR and RXR may markedly enhance the ability of ATRA to inhibit clonal growth and induce differentiation of HL-60 and NB4 leukemic cells. This occurs in the absence of continuous contact with retinoids.

A new class of retinoids with selective inhibition of AP-1 inhibits proliferation.[Pubmed:7969403]

Nature. 1994 Nov 3;372(6501):107-11.

Retinoids regulate many biological processes, including differentiation, morphogenesis and cell proliferation. They are also important therapeutic agents, but their clinical usefulness is limited because of side effects. Retinoid activities are mediated by specific nuclear receptors, the RARs and RXRs, which can induce transcriptional activation through specific DNA sites or by inhibiting the transcription factor AP-1 (refs 12-15), which usually mediates cell proliferation signals. Because the two types of receptor actions are mechanistically distinct, we investigated whether conformationally restricted retinoids, selective for each type of receptor action, could be identified. Here we describe a new class of retinoids that selectively inhibits AP-1 activity but does not activate transcription. These retinoids do not induce differentiation in F9 cells but inhibit effectively the proliferation of several tumour cell lines, and could thus serve as candidates for new retinoid therapeutic agents with reduced side effects.