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Chemical-Induced Skin Carcinogenesis Model Using Dimethylbenz[a]Anthracene and 12-O-Tetradecanoyl Phorbol-13-Acetate DMBA-TPA
Published on: December 19, 2019
DNA Methylome and Transcriptome Study of Triterpenoid CDDO in TPA-Mediated Skin Carcinogenesis Model
Hsiao-Chen Dina Kuo1,2, Renyi Wu1, Md Shahid Sarwar1
1Department of Pharmaceutics, Center for Phytochemical Epigenome Studies, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, NJ, 08854, Piscataway, USA.
Abstract:
Overexposure to ultraviolet radiation and environmental carcinogens drive skin cancer development through redox imbalance and gene mutation. Antioxidants such as triterpenoids have exhibited anti-oxidative and anti-inflammatory potentials to alleviate skin carcinogenesis. This study investigated the methylome and transcriptome altered by tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) or TPA with 2-cyano 2,3-dioxoolean-1,9-dien-28-oic acid (CDDO). The results show that CDDO blocks TPA-induced transformation dose dependently. Several differential expressed genes (DEGs) involved in skin cell transformation, while counteracted by CDDO, were revealed by differential expression analysis including Lyl1, Lad1, and Dennd2d. In CpG methylomic profiles, the differentially methylated regions (DMRs) in the promoter region altered by TPA while showing the opposite methylation status in the CDDO treatment group were identified. The correlation between DNA methylation and RNA expression has been established and DMRs showing inverse correlation were further studied as potential therapeutic targets. From the CpG methylome and transcriptome results, CDDO significantly restored gene expression of NAD(P)H:quinone oxidoreductase 1 (Nqo1) inhibited by TPA by decreasing their promoter CpG methylation. Ingenuity Pathways Analysis (IPA) shows that CDDO neutralized the effect of TPA through modulating cell cycles, cell migration, and inflammatory and immune response regulatory pathways. Notably, Tumor Necrosis Factor Receptor 2 (TNFR2) signaling was significantly downregulated by CDDO potentially contributing to prevention of TPA-induced cell transformation. Overall, incorporating the transcriptome, CpG methylome, and signaling pathway network, we reveal potential therapeutic targets and pathways by which CDDO could reverse TPA-induced carcinogenesis. The results could be useful for future human study and targets development for skin cancer.
Insights
This study shows the antioxidant CDDO reverses skin cancer development caused by TPA by altering gene expression and DNA methylation. CDDO offers potential therapeutic targets for skin cancer prevention.
Area of Science:
- Molecular Biology
- Epigenetics
- Cancer Research
Background:
- Skin cancer is driven by UV radiation and carcinogens, leading to redox imbalance and mutations.
- Antioxidants like triterpenoids show potential in mitigating skin carcinogenesis.
- 12-O-tetradecanoylphorbol-13-acetate (TPA) is a known tumor promoter in skin.
Purpose of the Study:
- To investigate the effects of CDDO on TPA-induced skin carcinogenesis at the methylome and transcriptome levels.
- To identify potential therapeutic targets and pathways for reversing TPA-induced skin cancer.
- To elucidate the mechanisms by which CDDO counteracts TPA's effects.
Main Methods:
- Differential gene expression analysis to identify key genes affected by TPA and CDDO.
- CpG methylomic profiling to identify differentially methylated regions (DMRs).
- Correlation analysis between DNA methylation and gene expression.
- Ingenuity Pathway Analysis (IPA) to understand affected signaling pathways.
Main Results:
- CDDO dose-dependently blocked TPA-induced skin cell transformation.
- Identified differentially expressed genes (DEGs) like Lyl1, Lad1, and Dennd2d, counteracted by CDDO.
- Discovered TPA-induced promoter CpG methylation changes reversed by CDDO, restoring Nqo1 expression.
- CDDO modulated cell cycle, migration, and inflammatory/immune pathways, downregulating TNFR2 signaling.
Conclusions:
- CDDO effectively reverses TPA-induced epigenetic and transcriptomic alterations in skin carcinogenesis.
- CDDO restores normal gene expression by decreasing promoter CpG methylation, notably for Nqo1.
- CDDO's modulation of key cellular pathways, including TNFR2 signaling, highlights its therapeutic potential for skin cancer.
