Journal Article

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), isolated from <i>Plumbago zeylanica</i>, inhibits ultraviolet radiation-induced development of squamous cell carcinomas

Jordan M. Sand, Bilal Bin Hafeez, Mohammad Sarwar Jamal, Olya Witkowsky, Emily M. Siebers, Joseph Fischer and Ajit K. Verma

in Carcinogenesis

Volume 33, issue 1, pages 184-190
Published in print January 2012 | ISSN: 0143-3334
Published online November 2011 | e-ISSN: 1460-2180 | DOI:
Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), isolated from Plumbago zeylanica, inhibits ultraviolet radiation-induced development of squamous cell carcinomas

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Plumbagin (PL) (5-hydroxy-2-methyl-1,4-napthoquinone), a medicinal plant-derived naphthoquinone, was isolated from the roots of the Plumbago zeylanica L. (also known as Chitrak). The roots of P. zeylanica L. have been used in Indian medicine for >2500 years as an anti-atherogenic, cardiotonic, hepatoprotective and neuroprotective agent. We present here that topical application of non-toxic doses (100–500 nmol) of PL to skin elicits dose-dependent inhibition of ultraviolet radiation (UVR)-induced development of squamous cell carcinomas (SCC). In this experiment, FVB/N mice were exposed to UVR (2 kJ/m2) three times weekly from a bank of six Kodacel-filtered FS40 sunlamps (∼60% UVB and 40% UVA). Carcinoma incidence in mice treated with vehicle, 100, 200 or 500 nmol PL, at 44 weeks post-UVR, were 86, 80 (P = 0.67), 53 (P = 0.12) and 7% (P = 0.0075), respectively. Both vehicle and PL-treated mice gained weight and did not exhibit any signs of toxicity during the entire period of the experiment. Molecular mechanisms associated with inhibition of UVR-induced development of SCC involved induction of apoptosis and inhibition of cell proliferation. Specific findings are that PL treatment (i) inhibited UVR-induced DNA binding of activating protein-1, nuclear factor-kappaB, Stat3 transcription factors and Stat3-regulated molecules (cdc25A and Survivin); (ii) inhibited protein levels of pERK1/2, PI3K85, pAKTSer473, Bcl2, BclxL, proliferating cell nuclear antigen and cell cycle inhibitory proteins p27 and p21 and (iii) increased UVR-induced Fas-associated death domain expression, poly (ADP-ribose) polymerase protein cleavage and Bax/Bcl2 ratio. Taken together, our findings suggest that PL may be a novel agent for the prevention of skin cancer.

Journal Article.  3893 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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