title: Pro-Oxidant Role of Silibinin in DMBA/TPA Induced Skin Cancer: 1H NMR Metabolomic and Biochemical Study.
abstract: Silibinin, a major bioactive flavonolignan in Silybum marianum, has received considerable attention in view of its anticarcinogenic activity. The present study examines its anticancer potential against 7, 12-dimethylbenz(a)anthracene (DMBA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) induced skin cancer. Male LACA mice were randomly segregated into 4 groups: Control, DMBA/TPA, Silibinin and Silibinin+DMBA/TPA. Tumors in DMBA/TPA and Silibinin+DMBA/TPA groups were histologically graded as squamous cell carcinoma. In the Silibinin+DMBA/TPA group, significant reduction in tumor incidence (23%), tumor volume (64.4%), and tumor burden (84.8%) was observed when compared to the DMBA/TPA group. The underlying protective mechanism of Silibinin action was studied at pre-initiation (2 weeks), post-initiation (10 weeks) and promotion (22 weeks) stages of the skin carcinogenesis. The antioxidant nature of Silibinin was evident at the end of 2 weeks of its treatment. However, towards the end of 10 and 22 weeks, elevated lipid peroxidation (LPO) levels indicate the pro-oxidative nature of Silibinin in the cancerous tissue. TUNEL assay revealed enhanced apoptosis in the Silibinin+DMBA/TPA group with respect to the DMBA/TPA group. Therefore, it may be suggested that raised LPO could be responsible for triggering apoptosis in the Silibinin+DMBA/TPA group. 1H Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the metabolic profile of the skin /skin tumors. Dimethylamine (DMA), glycerophosphocholine (GPC), glucose, lactic acid, taurine and guanine were identified as the major contributors for separation between the groups from the Principal Component Analysis (PCA) of the metabolite data. Enhanced DMA levels with no alteration in GPC, glucose and lactate levels reflect altered choline metabolism with no marked Warburg effect in skin tumors. However, elevated guanine levels with potent suppression of taurine and glucose levels in the Silibinin+DMBA/TPA group are suggestive of the pro-oxidative nature of Silibinin in regressing tumors. Thus, supporting the theory of augmented LPO levels resulting in increased apoptosis in the skin tumors treated with Silibinin.
authors.affiliation: Department of Biophysics, Basic Medical Sciences Block, Panjab University, Chandigarh, 160014, India.
authors.forename: Jasmine
authors.initials: J
authors.lastname: Sati
authors.affiliation: Department of Biophysics, Basic Medical Sciences Block, Panjab University, Chandigarh, 160014, India.
authors.forename: Biraja Prasad
authors.initials: BP
authors.lastname: Mohanty
authors.affiliation: Department of Biophysics, Basic Medical Sciences Block, Panjab University, Chandigarh, 160014, India.
authors.forename: Mohan Lal
authors.initials: ML
authors.lastname: Garg
authors.affiliation: Department of Biophysics, Basic Medical Sciences Block, Panjab University, Chandigarh, 160014, India.
authors.forename: Ashwani
authors.initials: A
authors.lastname: Koul
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002273:Carcinogens / Q000633:toxicity*; D002374:Catalase / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D055432:Metabolomics; D051379:Mice; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology*; D012878:Skin Neoplasms / Q000139:chemically induced* / Q000188:drug therapy / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity*
chemical_list: D000970:Antineoplastic Agents; D002273:Carcinogens; D017382:Reactive Oxygen Species; D012838:Silymarin; D000077385:Silybin; D015127:9,10-Dimethyl-1,2-benzanthracene; D002374:Catalase; D013482:Superoxide Dismutase; D013755:Tetradecanoylphorbol Acetate