Cancer Chemother Pharmacol (2010) 65:687–696 DOI 10.1007/s00280-009-1074-x 123 ORIGINAL ARTICLE Induction of apoptosis by [6]-gingerol associated with the modulation of p53 and involvement of mitochondrial signaling pathway in B[a]P-induced mouse skin tumorigenesis Nidhi Nigam · Jasmine George · Smita Srivastava · Preeti Roy · Kulpreet Bhui · Madhulika Singh · Yogeshwer Shukla Received: 14 March 2009 / Accepted: 8 July 2009 / Published online: 24 July 2009  Springer-Verlag 2009 Abstract Purpose To unravel the molecular mechanisms under- lying the chemopreventive potential of [6]-gingerol, a pungent ingredient of ginger rhizome (Zingiber oYcinale Roscoe, Zingiberaceae), against benzo[a]pyrene (B[a]P)- induced mouse skin tumorigenesis. Methods Topical treatment of [6]-gingerol (2.5 M/ani- mal) was given to the animals 30 min prior and post to B[a]P (5 g/animal) for 32 weeks. At the end of the study period, the skin tumors/tissues were dissected out and examined histopathologically. Flow cytometry was employed for cell cycle analysis. Further immunohistochemical local- ization of p53 and regulation of related apoptogenic proteins were determined by Western blotting. Results Chemopreventive properties of [6]-gingerol were reXected by delay in onset of tumorigenesis, reduced cumu- lative number of tumors, and reduction in tumor volume. Cell cycle analysis revealed that the appearance of sub-G1 peak was signiWcantly elevated in [6]-gingerol treated animals with post treatment showing higher eYcacy in preventing tumorigenesis induced by B[a]P. Moreover, elevated apoptotic propensity was observed in tumor tis- sues than the corresponding non-tumor tissues. Western blot analysis also showed the same pattern of chemopre- vention with [6]-gingerol treatment increasing the B[a]P suppressed p53 levels, also evident by immunohistochemis- try, and Bax while decreasing the expression of Bcl-2 and Survivin. Further, [6]-gingerol treatment resulted in release of Cytochrome c, Caspases activation, increase in apoptotic protease-activating factor-1 (Apaf-1) as mechanism of apoptosis induction. Conclusions On the basis of the results we conclude that [6]-gingerol possesses apoptotic potential in mouse skin tumors as mechanism of chemoprevention hence deserves further investigation. Keywords Mouse skin tumorigenesis · [6]-Gingerol · Benzo(a)pyrene · Chemoprevention · Apoptosis Introduction Developing novel strategies to prevent skin cancer repre- sents an urgent goal due to increasing rise in incidence of skin cancer patients throughout the world [1, 2]. Not sur- prisingly, more than one million new cases of basal cell and squamous cell carcinoma are diagnosed in the United States every year, accounting for 40% of all cancer cases [3, 4]. In Asian population, the incidence of skin cancer is compara- tively less. India is one of the low incidence regions of the world subjected to skin cancer. Cancer registries in India report that the age speciWc incidence rates for skin cancer are less than 0.5 per 1,000,000 [5]. However, because skin lesions are visible and easily accessible, skin cancers pro- vide us with an excellent in vivo model to study the devel- opment of cancers [6]. Naturally occurring phytochemicals present an active cancer preventive strategy to inhibit, delay, or reverse human carcinogenesis. Studies have indicated that certain daily-consumed dietary phytochemicals have cancer pro- tective eVects mediated by carcinogens. Ginger, the pow- dered rhizome of the herb Zingiber oYcinale, is widely N. Nigam · J. George · S. Srivastava · P. Roy · K. Bhui · M. Singh · Y. Shukla (&) Proteomics Laboratory, Indian Institute of Toxicology Research (CSIR), M.G. Marg, P.O. Box 80, Lucknow 226001, India e-mail: yogeshwer_shukla@hotmail.com; yshukla@iitr.res.in