Inhibition of Activator Protein-1 by Sulforaphane Involves Interaction with Cysteine in the cFos DNA-Binding Domain: Implications for Chemoprevention of UVB-Induced Skin Cancer

Abstract

Sulforaphane is an isothiocyanate derived from cruciferous vegetables that has been linked to decreased risk of certain cancers. Although the role of sulforaphane in the induction of the transcription factor Nrf2 has been studied extensively, there is also evidence that inhibition of the transcription factor activator protein-1 (AP-1) may contribute to the chemopreventive properties of this compound. In this study, we show for the first time that sulforaphane is effective at reducing the multiplicity and tumor burden of UVB-induced squamous cell carcinoma in a mouse model using cotreatment with the compound and the carcinogen. We also show that sulforaphane pretreatment is able to reduce the activity of AP-1 luciferase in the skin of transgenic mice after UVB. Chromatin immunoprecipitation analysis verified that a main constituent of the AP-1 dimer, cFos, is inhibited from binding to the AP-1 DNA binding site by sulforaphane. Electrophoretic mobility shift assay analysis of nuclear proteins also shows that sulforaphane and diamide, both known to react with cysteine amino acids, are effective at inhibiting AP-1 from binding to its response element. Using truncated recombinant cFos and cJun, we show that mutation of critical cysteines in the DNA-binding domain of these proteins (Cys 154 in cFos and Cys 272 in cJun) results in loss of sensitivity to both sulforaphane and diamide in electrophoretic mobility shift assay analysis. Together, these data indicate that inhibition of AP-1 activity may be an important molecular mechanism in chemoprevention of squamous cell carcinoma by sulforaphane. [Cancer Res 2009;69(17):7103-10]

Phytoconstituents as apoptosis inducing agents: strategy to combat cancer

“…Won et al (2004) reported anticancer effects of Parthenolide (major sesquiterpene lactone) found in Tanacetum parthenium and reported the suppression of AP-1 and mitogen-activated protein kinases (MAPK). Dickinson et al (2009) were first to report that Sulforaphane downregulates AP-1 activity in UVBinduced squamous cell carcinoma in mouse. Results pointed that inhibition of AP-1 activity by Sulforaphane can be used as a target for prevention of squamous cell carcinoma.…”

Nrf2 establishes a glutathione-mediated gradient of UVB cytoprotection in the epidermis

“…Vice versa, topical treatment of SKH-1 mouse back skin with broccoli sprout extracts that contain the Nrf2 activator sulforaphane protected against UVB-induced photocarcinogenesis (Dinkova-Kostova et al 2006). Since sulforaphane has multiple anti-carcinogenic effects independent of Nrf2 (Fimognari and Hrelia 2007;Dickinson et al 2009), the effect of Nrf2 activation in the UV response needs to be studied using genetic approaches. This will also allow the identification of the molecular and cellular mechanisms underlying the protective effect of Nrf2 in the UVB response, which are as yet unknown.…”

Evaluation of the Protective Effect of Brassica oleracea (L. var. acephala) in Rats with Surgically-Induced Gastroesophageal Reflux Disease

“…As shown here, treatment with B. oleracea extract decreased the severity of esophagitis without genotoxic and cytotoxic effects. The principal compound present in B. oleracea capable of attenuating inflammation is SF, as demonstrated in gastritis and skin inflammation studies (22)(23)(24)(25). These studies have shown that SF suppresses proinflammatory cytokines, such as tumor necrosis factor-α, interleukin-1β and interleukin-6 via nuclear factorerythroid-2-related factor and/or inhibition of the activator protein-1.…”