title: Cell death induced by N-(4-hydroxyphenyl)retinamide in human epidermal keratinocytes is modulated by TGF-beta and diminishes during the progression of squamous cell carcinoma.
abstract: It has been demonstrated that the chemopreventive agent N-(4-hydroxyphenyl)retinamide (4-HPR) induces apoptotic cell death, but recent data has suggested that late stage/recurrent tumours lose their response to 4-HPR-induced cell death by mechanisms that are unknown. Our study investigated the ability of 4-HPR to induce cell death in keratinocyte cell lines that represent different stages of carcinogenesis and the role of TGF-beta signalling in the induction of cell death by 4-HPR. We show that treatment of the immortalised keratinocyte cell line HaCaT with 10(-5) M 4-HPR induced cell death by apoptosis and caused an accumulation of cells in the G0/G1 phase of the cell cycle. Using a genetically related series of human skin keratinocytes derived from HaCaT that reflect tumour progression and metastasis in vivo, we demonstrate that 4-HPR-induced cell death and apoptosis is attenuated in the more aggressive tumour cell lines but that a reduced level of response is retained. Response to TGF-beta-induced growth inhibition was also reduced in the more aggressive cell lines. Treatment of HaCaT cells with 4-HPR induced TGF-beta2 expression and an increase in the amount of active TGF-beta in the culture medium. The inhibition of TGF-beta signalling attenuated 4-HPR-induced apoptosis and both TGF-beta1 and TGF-beta2 potentiated 4-HPR-induced apoptosis and enhanced 4-HPR-induced growth inhibition. Our results demonstrate that loss of response to 4-HPR correlates with a loss of response to the growth inhibitory effects of TGF-beta and that adjuvant therapies that upregulate TGF-beta may enhance the chemopreventive effects of 4-HPR.
authors.affiliation: Department of Oral and Dental Science, University of Bristol, Bristol, United Kingdom. maria.davies@bristol.ac.uk
authors.forename: Maria
authors.initials: M
authors.lastname: Davies
authors.forename: Ian C
authors.initials: IC
authors.lastname: Paterson
authors.forename: Anu
authors.initials: A
authors.lastname: Ganapathy
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Prime
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015152:Blotting, Northern; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D017313:Fenretinide / Q000494:pharmacology*; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D053781:Transforming Growth Factor beta2 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D017313:Fenretinide