Modulation of p53 in 7,12-dimethylbenz[a]anthracene-induced skin tumors by diallyl sulfide in Swiss albino mice
Authors: Yogeshwer Shukla
Annu Arora
Imtiaz A Siddiqui
Journal: Molecular Cancer Therapeutics (2004)
Discipline: CLINICAL MEDICINE
Keywords: Allium vegetables; Diallyl sulfide; cancer prevention; p53 expression; DMBA-induced skin tumors
Affiliations: Environmental Carcinogenesis Division, Industrial Toxicology Research Center, PO Box 80, MG Marg, Lucknow 226001, India.

Abstract:  Allium vegetables have been shown to have beneficial health effects against several chronic diseases including cancer. Diallyl sulfide (DAS), an organosulfur compound present in garlic, is well known for its chemopreventive properties in several tumor models. The pharmacologic role of DAS in prevention and treatment of cancer is well documented in the literature, but its molecular mechanism of action is not yet well defined. In the present study, modulation in p53 expression by topical application of DAS was recorded in 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin tumors in Swiss albino mice. Western blot analysis and immunohistochemical protein detection, combined with multivariable flow cytometry, show that DAS application induces the expression of the wild-type (wt) p53 and down-regulates the expression of mutant (mut) p53. Immunoblotting analysis of tumors showed significant increase in levels of wtp53 by DAS application, whereas for mutp53 the DMBA-induced levels of protein were found to reduce to near normal levels with DAS application. The quantitative analysis of immunostained skin/tumor sections using image analysis and quantitative stereology showed 66.6% and 54.2% increases in wtp53 levels and 53.4% and 44.3% decreases in mutp53 levels in animals where DAS was applied 1 hour prior to or 1 hour after DMBA application, respectively. Flow cytometric analysis further confirmed modulation of wtp53 and mutp53 protein in DAS-supplemented tumors. The increase in the expression of wt tumor suppressor gene protein p53 was accompanied by elevation of the levels of cyclin-dependent kinase inhibitor p21/waf1. The percentage increase in the levels of p21/waf1 was found to be 72.9% and 61.3%, respectively, in DAS-supplemented groups before and after administration. These results thus show that DAS is a potential chemopreventive agent capable of modulating and regulating the tumor suppressor p53 along with its downstream effective molecule, p21/waf1. Thus, DAS can be a potential chemopreventive agent against skin tumor development. 

Retracted: No

PubPeer comments:
 A. Untreated control for Mol Cancer Therap and E. ACE+DAS for Cancer Lett ![file] , 
 At left: Figure 1,  A, Western blot analysis of wtp53 in mouse skin tumors following DAS application. Skin tumor lysates were prepared as described in Materials and Methods and proteins (30-50 u03bcg) were employed for Western blots. An increased expression of wtp53 was recorded in the DMBA-induced tumors. DAS application was found to further elevate the wtp53 expression in mouse skin tumors. Lane 1, untreated; lane 2, DMBA; lane 3, DAS + DMBA; lane 4, DMBA + DAS; lane 5, DAS. At right:  Fig. 1. Showing changes in the expression levels of p21 ras mouse skin of various groups at **24**... h, respectively. Lane a: ACE, b: ACE+DAS, c: ACE+DMBA, d: DAS+DMBA, e: DMBA+DAS. , from [Arora c (2006)] . ![file] Could the authors clarify whether the control band comes from one experiment or two? The descriptions of the lanes do not seem to be compatible. , 
 Figure 4,  Western blot analysis of p21 waf1 in mouse skin tumors following DAS application . ![file] Compared with (at bottom) Fig. 3 from [Kalra et al. (2007)] .  Effect of TF treatment on p53 (a) and its downstream regulator Bax (b) and **Bcl-2 (c)** in LNCaP cells . , 
 Band cloned. ![file] , 
 Figure 1A: ![file] , 
 Having seen the comment https: pubpeer.com publications A5216BB8F4E05BB3A05E274F56618B#8, I noticed that **Fig. 6C** is simply a higher resolution image of an area of **Fig. 6D** ![file] , 
 Figure 5. FACS plot appears to have been hand-drawn. ![file] ,