Geraniol is a dietary monoterpene alcohol that is found in the essential oils of aromatic plants. To date, experimental evidence supports the therapeutic or preventive effects of geraniol on different types of cancer, such as breast, lung, colon, prostate, pancreatic, and hepatic cancer, and has revealed the mechanistic basis for its pharmacological actions. In addition, geraniol sensitizes tumor cells to commonly used chemotherapy agents. Geraniol controls a variety of signaling molecules and pathways that represent tumor hallmarks; these actions of geraniol constrain the ability of tumor cells to acquire adaptive resistance against anticancer drugs. In the present review, we emphasize that geraniol is a promising compound or chemical moiety for the development of a safe and effective multi-targeted anticancer agent. We summarize the current knowledge of the effects of geraniol on target molecules and pathways in cancer cells. Our review provides novel insight into the challenges and perspectives with regard to geraniol research and to its application in future clinical investigation.

Leptin is a pivotal regulator of energy and glucose homeostasis, and defects in leptin signaling result in obesity and diabetes. The ATP-sensitive potassium (K _ATP ) channels couple glucose metabolism to insulin secretion in pancreatic β-cells. In this study, we provide evidence that leptin modulates pancreatic β-cell functions by promoting K _ATP channel translocation to the plasma membrane via AMP-activated protein kinase (AMPK) signaling. K _ATP channels were localized mostly to intracellular compartments of pancreatic β-cells in the fed state and translocated to the plasma membrane in the fasted state. This process was defective in leptin-deficient ob /ob mice, but restored by leptin treatment. We discovered that the molecular mechanism of leptin-induced AMPK activation involves canonical transient receptor potential 4 and calcium/calmodulin-dependent protein kinase kinase β. AMPK activation was dependent on both leptin and glucose concentrations, so at optimal concentrations of leptin, AMPK was activated sufficiently to induce K _ATP channel trafficking and hyperpolarization of pancreatic β-cells in a physiological range of fasting glucose levels. There was a close correlation between phospho-AMPK levels and β-cell membrane potentials, suggesting that AMPK-dependent K _ATP channel trafficking is a key mechanism for regulating β-cell membrane potentials. Our results present a signaling pathway whereby leptin regulates glucose homeostasis by modulating β-cell excitability.

Transglutaminase2 (TG2) is a multi-functional protein involved in various cellular processes, including apoptosis, differentiation, wound healing, and angiogenesis. The malfunction of TG2 causes many human disease including inflammatory disease, celiac disease, neurodegenerative diseases, tissue fibrosis, and cancers. Protein cross-linking activity, which is representative of TG2, is activated by calcium ions and suppressed by GTP. Here, we elucidated the structure of TG2 in complex with its endogenous inhibitor, GTP. Our structure showed why GTP is the optimal nucleotide for interacting with and inhibiting TG2. In addition, sequence comparison provided information describing the evolutionary scenario of GTP usage for controlling the activity of TG2.

Geraniol, an acyclic dietary monoterpene, has been found to suppress cancer survival and growth. However, the molecular mechanism underlying the antitumor action of geraniol has not been investigated at the genome‐wide level. In this study, we analyzed the microarray data obtained from geraniol‐treated prostate cancer cells. Geraniol potently altered a gene expression profile and primarily down‐regulated cell cycle‐related gene signatures, compared to linalool, another structurally similar monoterpene that induces no apparent phenotypic changes. Master regulator analysis using the prostate cancer‐specific regulatory interactome identified that the transcription factor E2F8 as a specific target molecule regulates geraniol‐specific cell cycle signatures. Subsequent experiments confirmed that geraniol down‐regulated E2F8 expression and the knockdown of E2F8 was sufficient to suppress cell growth by inducing G₂/M arrest. Epidemiological analysis showed that E2F8 is up‐regulated in metastatic prostate cancer and associated with poor prognosis. These results indicate that E2F8 is a crucial transcription regulator controlling cell cycle and survival in prostate cancer cells. Therefore, our study provides insight into the role of E2F8 in prostate cancer biology and therapeutics.