Chloroquine is an established antimalarial agent that has been recently tested in clinical trials for its anticancer activity. The favorable effect of chloroquine appears to be due to its ability to sensitize cancerous cells to chemotherapy, radiation therapy, and induce apoptosis. The present study investigated the interaction of zinc ions with chloroquine in a human ovarian cancer cell line (A2780). Chloroquine enhanced zinc uptake by A2780 cells in a concentration-dependent manner, as assayed using a fluorescent zinc probe. This enhancement was attenuated by TPEN, a high affinity metal-binding compound, indicating the specificity of the zinc uptake. Furthermore, addition of copper or iron ions had no effect on chloroquine-induced zinc uptake. Fluorescent microscopic examination of intracellular zinc distribution demonstrated that free zinc ions are more concentrated in the lysosomes after addition of chloroquine, which is consistent with previous reports showing that chloroquine inhibits lysosome function. The combination of chloroquine with zinc enhanced chloroquine's cytotoxicity and induced apoptosis in A2780 cells. Thus chloroquine is a zinc ionophore, a property that may contribute to chloroquine's anticancer activity.

MicroRNAs (miRNAs), which regulate gene expression by partial complementarity to the 3' untranslated region of their target genes, have been implicated in cancer initiation and progression. However, the molecular mechanism underlying the regulation of miRNA expression during pancreatic tumorigenesis has not been extensively reported. In this study, we first compared the miRNA expression in human pancreatic cancers and adjacent normal tissues by miRNA array and identified 12 differentially expressed miRNAs. miR-132, which is downregulated in tumors, was further studied in greater detail. Decreased expression of miR-132 was confirmed in 16 of 20 pancreatic carcinomas (P < 0.0001), compared with their respective benign tissues by TaqMan miRNA assays. miR-132 expression was remarkably influenced by promoter methylation in PANC1 and SW1990 cells. Promoter hypermethylation was observed in tumor samples but not in the normal counterparts, and the expression of miR-132 negatively correlated with its methylation status (P = 0.013). miR-132 was transcribed by RNA polymerase II, and Sp1 played a major role in miR-132 transcription. The expression of Sp1 correlated with that of miR-132 in tissues. Moreover, cancerous tissues showed significantly lower Sp1-binding affinity to the miR-132 promoter, relative to non-tumor samples. Proliferation and colony formation of pancreatic cancer cells were suppressed in cells transfected with miR-132 mimics and enhanced in cells transfected with miR-132 inhibitor by negatively regulating the Akt-signaling pathway. Our present findings illustrate the mechanism driving miR-132 downregulation and the important role of miR-132 in pancreatic cancer development.

Background:The mechanisms of PPAR␣-mediated inhibition of tumor growth and angiogenesis remain unknown. Results: Activation of PPAR␣ suppresses hypoxia-induced HIF-1␣ signaling via promoting HIF-1␣ degradation and diminishes hypoxia-induced VEGF secretion from cancer cells and tube formation by endothelial cells. Conclusion: Activation of PPAR␣ suppresses the HIF-1␣ signaling pathway in cancer cells. Significance: The results support the development of PPAR␣ agonists as anticancer agents.

Radiation-induced skin injury is a common side effect of radiotherapy and can limit the duration and dose of radiotherapy. Most early work focused on elimination of reactive oxygen species (ROS) after radiation; however, less is known about the mechanisms underlying amplification of ROS and consequent skin injury by radiation. 5,6,7,8-Tetrahydrobiopterin (BH4) is an essential cofactor for all nitric oxide synthases. Inadequate availability of BH4 leads to uncoupling of nitric oxide synthases and production of highly oxidative radicals. In this study, we demonstrated that radiation disrupted BH4, which resulted in nitric oxide synthases uncoupling and augmented radiation-induced ROS. Overexpression of GTP cyclohydrolase I (GCH1), the rate-limiting enzyme for BH4 synthesis, restored cellular BH4 levels and nitric oxide production and decreased radiation-induced ROS. GCH1 also protected skin cells and rat skins against radiation-induced damage. We found that GCH1 was regulated by NF-E2-related factor 2, a key mediator of the cellular antioxidant response. Importantly, we identified GCH1 as a key effector for NF-E2-related factor 2-mediated protection against radiation-induced skin injury by inhibiting ROS production. Taken together, the findings of this study illustrate the key role of the NF-E2-related factor 2/GCH1/BH4 axis during radiation-induced skin damage.