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Carnosic acid (CA), a major polyphenolic diterpene present in Rosmarinus officinalis, has been reported to have multiple functions, including antitumor activity. The MTT assay, BrdU incorporation, wound healing, and colony formation were used to detect melanoma B16F10 cell growth and proliferation. Flow cytometry was used for cell cycle detection. p21 and p27 expression was detected by Western blotting. B16F10 cell xenograft model was established, and treated with CA, carmustine (BCNU), or lomustine (CCNU). The present study found that CA exhibits significant growth inhibition and cell cycle arrest in melanoma B16F10 cells. We also found that CA triggers cell cycle arrest at G0/G1 phase, and enhances p21 expression. Additionally, CA can enhance BCNU- and CCNU-mediated cytotoxicity and cell cycle arrest in B16F10 cells. Finally, we found that CA inhibits tumor growth, and reduces the values of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in vivo. The present study study concluded that CA may be safe and useful as a novel chemotherapeutic agent.

Hepatocellular carcinoma is the leading cause of male cancer death in Taiwan. We have found that the level of glucocorticoid receptor in hepatocellular carcinoma is significantly higher than that in the peritumoral tissue. In this study, we used a rat liver glucocorticoid receptor complementary DNA probe to examine the expression of glucocorticoid receptor gene in 15 paired samples of hepatocellular carcinoma and their peritumoral tissues. No differences in genomic DNA patterns of the glucocorticoid receptor gene were found between the tumor and peritumoral tissues. The amount of glucocorticoid receptor was found to be significantly higher in hepatoma samples than in peritumoral liver samples. The levels of glucocorticoid receptor messenger RNAs were increased in most tumors compared with their peritumoral samples. To examine the function of glucocorticoid receptors in hepatoma, we examined the expression of glucocorticoid receptor and its relation to cell-cycle progression in human HepG2 cells. Using specific monoclonal antibodies and flow cytometric study, we found glucocorticoid receptor to be expressed constitutively in all cell-cycle phases. In addition, hydrocortisone treatment of HepG2 cells resulted in increased expression of glucocorticoid receptors and increased secretion of alpha-fetoprotein. RU-486, a glucocorticoid antagonist, blocked the hydrocortisone effect, indicating that glucocorticoid receptors are functional in HepG2 cells. Taken together, our data suggest that glucocorticoids and their receptors play an important role in the growth of hepatoma.

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