Dietary restriction (DR) delays the incidence and decreases the growth of various types of tumors; however, the mechanisms responsible for DR-mediated antitumor effects have not been unequivocally identified. Here, we report that DR suppresses xenograft tumor growth by upregulating a novel signaling pathway. DR led to upregulated aldolase A (ALDOA) expression in xenograft tumors. ALDOA physically interacted with the catalytic subunit of DNA-dependent protein kinase (DNA-PK) and promoted DNA-PK activation. Activated DNA-PK phosphorylated p53 and increased its activity. Although ALDOA can function as an oncogene in cultured cells, it can also activate the tumor suppressor p53. Thus, ALDOA overexpression in the presence of p53 suppressed xenograft tumor growth; however, when p53 was suppressed, ALDOA overexpression promoted xenograft tumor growth. Moreover, we demonstrated that p53 suppression inhibited the antitumor effects of DR. Our results indicate that upregulation of the ALDOA/DNA-PK/p53 pathway is a mechanism accounting for the antitumor effects of DR.

This study investigated combined chemopreventive potential of curcumin and resveratrol during benzo(a)pyrene (BP)-induced lung carcinogenesis in mice. The mice were segregated into five groups that included normal control, BP-treated, BP + curcumin-treated, BP + resveratrol-treated, and BP + curcumin + resveratrol-treated groups. A statistically significant increase in the levels of lipid peroxidation (LPO) was observed in the lungs of mice after 22 weeks of single dose of benzo(a)pyrene. Further, BP treatment also resulted in a significant increase in the enzyme activities of aryl hydrocarbon hydroxylase as well as drug-metabolizing enzymes, namely cytocrome P450 and cytochrome b5. On the other hand, reduced glutathione (GSH) levels, the activities of superoxide dismutase (SOD), glutathione reductase (GR), and glutathione- S-transferase (GST) were found to be significantly decreased following BP treatment. Supplementation with curcumin and resveratrol to BP-treated mice significantly decreased the LPO levels, GSH levels, and enzyme activities of drug-metabolizing enzymes. Further, treatment of curcumin and resveratrol to BP-treated mice significantly elevated the activities of SOD, GR, and GST. Histoarchitectural studies showed well-differentiated signs of lung carcinogenesis following BP administration to mice. However, combined treatment with curcumin and resveratrol resulted in a noticeable improvement in the lung histoarchitecture. This study, therefore, concludes that curcumin and resveratrol when supplemented in combination regulate drug-metabolizing enzymes as well as antioxidant enzymes during lung carcinogenesis in mice.