Transforming growth factor-β (TGF-β) responsiveness in cultured cells can be modulated by TGF-β partitioning between lipid raft/caveolae- and clathrin-mediated endocytosis pathways. Lipid rafts are plasma membrane microdomains with an important role in cell survival signaling, and cholesterol is necessary for the lipid rafts’ structure and function. Euphol is a euphane-type triterpene alcohol that is structurally similar to cholesterol and has a wide range of pharmacological properties, including anti-inflammatory and anti-cancer effects. In the present study, euphol suppressed TGF-β signaling by inducing TGF-β receptor movement into lipid-raft microdomains and degrading TGF-β receptors.

Pentabromophenol (PBP), a brominated flame retardant (BFR), is widely used in various consumerproducts. BFRs exert adverse health effects such as neurotoxic and endocrine-disrupting effects. In this study, we found that PBP suppressed TGF-β response by accelerating the turnover rate of TGF-β receptors. PBP suppressed TGF-β-mediated cell migration, PAI-1 promoter-driven reporter gene activation, and Smad2/3 phosphorylation in various cell types. Furthermore, PBP abolished TGF-β-mediated repression of E-cadherin expression, in addition to the induction of vimentin expression and N-cadherin and fibronectin upregulation, thus blocking TGF-β-induced epithelial-mesenchymal transition in A549 and NMuMG cells. However, this inhibition was not observed with other congeners such as tribromophenol and triiodophenol. TGF-β superfamily members play key roles in regulating various biological processes including cell proliferation and migration as well as cancer development and progression. The results of this in vitro study provide a basis for studies on the detailed relationship between PBP and modulation of TGF-β signalling. Because PBP is similar to other BFRs such as polybrominated diphenyl ethers (PBDEs), additional laboratory and mechanistic studies should be performed to examine BFRs as potential risk factors for tumorigenesis and other TGF-β-related diseases.Brominated flame retardant (BFR) phenols include pentabromophenol (PBP), 2,4,6-tribromophenol (TBP), 2,4-dibromophenol, and tetrabrominated bisphenol (TBBP). PBP, TBP, and TBBP are precursors of four nonphenolic derivatives that are also used as BFRs 1 . PBP and TBP are used for developing epoxy resins and vinyl aromatic polymers and as intermediates of polyester resins 2 . BFRs and their metabolites induce potential endocrine-disrupting effects in humans and animals 3 , in addition to being detected in human milk and blood 4 . BFRs are one of the most widely used but least understood organohalogen compounds. Molecular mechanisms underlying the toxic effects of BFRs are largely unknown. In vitro studies have shown that PBP and TBP and their brominated phenol congeners interact with transthyretin, a human thyroxine transport protein, competing with thyroid hormone thyroxine or with oestrogen on oestrogen receptors [5][6][7] . An in vitro study also revealed that TBP markedly enhanced aromatase activity, whereas 6-OH-BDE99 and 6-OH-BDE47 considerably reduced aromatase activity 8 . In the present study, we determined that PBP suppressed transforming growth factor-beta (TGF-β ) signalling by accelerating TGF-β receptor degradation through caveolae-mediated endocytosis.TGF-β superfamily proteins, including bone morphogenetic proteins, inhibins, activins, and TGF-β , regulate many physiological processes such as cell proliferation, development, and differentiation. Dysregulation of these proteins is associated with cancer development, vascular diseases, and fibrosis [9][10][11] . In a canonical pathway, binding of TGF-β to TGF-β receptors induces the assembly of type I ...

Our results suggest that cholest-4-en-3-one inhibits TGF-β signaling may be due, in part to the translocation of TGF-β receptor from non-lipid raft to lipid raft microdomain in plasma membranes. Our findings also implicate that cholest-4-en-3-one may be further explored for its potential role in colorectal cancer correlate to TGF-β deficiency.

The efficacy of chemotherapeutic drugs is often offset by severe side effects attributable to poor selectivity and toxicity to normal cells. Recently, the enzyme dipeptidyl peptidase IV (DPPIV) was considered as a potential target for the delivery of chemotherapeutic drugs. The purpose of this study was to investigate the feasibility of targeting chemotherapeutic drugs to DPPIV as a strategy to enhance their specificity. The expression profile of DPPIV was obtained for seven cancer cell lines using DNA microarray data from the DTP database, and was validated by RT-PCR. A prodrug was then synthesized by linking the cytotoxic drug melphalan to a proline-glycine dipeptide moiety, followed by hydrolysis studies in the seven cell lines with a standard substrate, as well as the glycyl-prolyl-melphalan (GP-Mel). Lastly, cell proliferation studies were carried out to demonstrate enzyme-dependent activation of the candidate prodrug. The relative RT-PCR expression levels of DPPIV in the cancer cell lines exhibited linear correlation with U95Av2 Affymetrix data (r2 = 0.94), and with specific activity of a standard substrate, glycine-proline-p-nitroanilide (r2 = 0.96). The significantly higher antiproliferative activity of GP-Mel in Caco-2 cells (GI50 = 261 μM) compared to that in SK-MEL-5 cells (GI50 = 807 μM) was consistent with the 9-fold higher specific activity of the prodrug in Caco-2 cells (5.14 pmol/min/μg protein) compared to SK-MEL-5 cells (0.68 pmol/min/μg protein) and with DPPIV expression levels in these cells. Our results demonstrate the great potential to exploit DPPIV as a prodrug activating enzyme for efficient chemotherapeutic drug targeting.