title: Murraya koenigii leaf extract inhibits proteasome activity and induces cell death in breast cancer cells.
abstract: BACKGROUND
  Inhibition of the proteolytic activity of 26S proteasome, the protein-degrading machine, is now considered a novel and promising approach for cancer therapy. Interestingly, proteasome inhibitors have been demonstrated to selectively kill cancer cells and also enhance the sensitivity of tumor cells to chemotherapeutic agents. Recently, polyphenols/flavonoids have been reported to inhibit proteasome activity. Murraya koenigii Spreng, a medicinally important herb of Indian origin, has been used for centuries in the Ayurvedic system of medicine. Here we show that Murraya koenigii leaves (curry leaves), a rich source of polyphenols, inhibit the proteolytic activity of the cancer cell proteasome, and cause cell death.
  
  
  METHODS
  Hydro-methanolic extract of curry leaves (CLE) was prepared and its total phenolic content [TPC] determined by, the Folin-Ciocalteau's method. Two human breast carcinoma cell lines: MCF-7 and MDA-MB-231 and a normal human lung fibroblast cell line, WI-38 were used for the studies. Cytotoxicity of the CLE was assessed by the MTT assay. We studied the effect of CLE on growth kinetics using colony formation assay. Growth arrest was assessed by cell cycle analysis and apoptosis by Annexin-V binding using flow cytometry. Inhibition of the endogenous 26S proteasome was studied in intact cells and cell extracts using substrates specific to 20S proteasomal enzymes.
  
  
  RESULTS
  CLE decreased cell viability and altered the growth kinetics in both the breast cancer cell lines in a dose-dependent manner. It showed a significant arrest of cells in the S phase albeit in cancer cells only. Annexin V binding data suggests that cell death was via the apoptotic pathway in both the cancer cell lines. CLE treatment significantly decreased the activity of the 26S proteasome in the cancer but not normal cells.
  
  
  CONCLUSIONS
  Our study suggests M. koenigii leaves to be a potent source of proteasome inhibitors that lead to cancer cell death. Therefore, identification of active component(s) from the leaf extract could lead to the development of anti-cancer agents which could be useful in the treatment of different types of cancers.
authors.affiliation: Department of Endocrinology & Metabolism, National Institute of Nutrition, Hyderabad, India.
authors.forename: Bindu
authors.initials: B
authors.lastname: Noolu
authors.forename: Rajanna
authors.initials: R
authors.lastname: Ajumeera
authors.forename: Anitha
authors.initials: A
authors.lastname: Chauhan
authors.forename: Balakrishna
authors.initials: B
authors.lastname: Nagalla
authors.forename: Raghunath
authors.initials: R
authors.lastname: Manchala
authors.forename: Ayesha
authors.initials: A
authors.lastname: Ismail
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D032101:Murraya / Q000737:chemistry*; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use; D018515:Plant Leaves; D059808:Polyphenols / Q000494:pharmacology / Q000627:therapeutic use*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects*; D061988:Proteasome Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D016196:S Phase / Q000187:drug effects
chemical_list: D017304:Annexin A5; D000972:Antineoplastic Agents, Phytogenic; D010936:Plant Extracts; D059808:Polyphenols; D061988:Proteasome Inhibitors; D046988:Proteasome Endopeptidase Complex