ABSTRACT
BACKGROUND: A. oxyphylla extract is known to possess a wide range of pharmacological activites. However, the molecular mechanism of A. oxyphylla and its bioactive compound nootkatone in colorectal cancer is unknown. METHODS: Our study aims to examine the role of A. oxyphylla and its bioactive compound nootkatone, in tumor suppression using several in vitro assays. RESULTS: Both A. oxyphylla extract and nootkatone exhibited antiproliferative activity in colorectal cancer cells. A. oxyphylla displayed antioxidant activity in colorectal cancer cells, likely mediated via induction of HO-1. Furthermore, expression of pro-apoptotic protein NAG-1 and cell proliferative protein cyclin D1 were increased and decreased respectively in the presence of A. oxyphylla. When examined for anticancer activity, nootkatone treatment resulted in the reduction of colony and spheroid formation. Correspondingly, nootkatone also led to increased NAG-1 expression and decreased cyclin D1 expression. The mechanism by which nootkatone suppresses cyclin D1 involves protein level regulation, whereas nootkatone increases NAG-1 expression at the transcriptional level. In addition to having PPARγ binding activity, nootkatone also increases EGR-1 expression which ultimately results in enhanced NAG-1 promoter activity. CONCLUSION: In summary, our findings suggest that nootkatone is an anti-tumorigenic compound harboring antiproliferative and pro-apoptotic activity.
Subject(s)
Cell Proliferation/drug effects , Colorectal Neoplasms/drug therapy , Plant Extracts/pharmacology , Polycyclic Sesquiterpenes/pharmacology , Alpinia , Apoptosis/drug effects , Cell Line, Tumor , Colorectal Neoplasms/genetics , Colorectal Neoplasms/pathology , Cyclin D1/genetics , Early Growth Response Protein 1/genetics , Gene Expression Regulation, Neoplastic/drug effects , Growth Differentiation Factor 15/genetics , Heme Oxygenase-1/drug effects , Humans , PPAR gamma/genetics , Plant Extracts/chemistry , Polycyclic Sesquiterpenes/chemistry , Polycyclic Sesquiterpenes/isolation & purification , Promoter Regions, Genetic/drug effects , Sesquiterpenes/chemistry , Sesquiterpenes/pharmacologyABSTRACT
Non-steroidal anti-inflammatory drug activated gene-1 (NAG-1), also known as growth differentiation factor 15 (GDF15), is a TGF-ß (transforming growth factor beta) superfamily protein with a distinctive secretion pathway. NAG-1 is associated with multiple diseases including cancer, wherein it plays a role in both pro- and anti-cancer activities. We previously reported that NAG-1 is translocated to different subcellular compartments and its activity depends on its localization. In this paper, we report that the transfection of a novel peptide corresponding to the nuclear localization signal (NLS) of NAG-1 blocks its translocation to the nucleus. Further, accumulation of NAG-1 in the cytoplasm decreased mitochondrial membrane potential, thus implying apoptosis induction as a consequence. Overall, our results indicate that the novel peptide derived from NAG-1 NLS sequence is a promising tool for enhancing the anti-tumorigenic activity of NAG-1.
