title: Synergistic anticancer effects of a bioactive subfraction of Strobilanthes crispus and tamoxifen on MCF-7 and MDA-MB-231 human breast cancer cell lines.
abstract: BACKGROUND
  Development of tumour resistance to chemotherapeutic drugs and concerns over their toxic effects has led to the increased use of medicinal herbs or natural products by cancer patients. Strobilanthes crispus is a traditional remedy for many ailments including cancer. Its purported anticancer effects have led to the commercialization of the plant leaves as medicinal herbal tea, although the scientific basis for its use has not been established. We previously reported that a bioactive subfraction of Strobilanthes crispus leaves (SCS) exhibit potent cytotoxic activity against human breast cancer cell lines. The current study investigates the effect of this subfraction on cell death activities induced by the antiestrogen drug, tamoxifen, in estrogen receptor-responsive and nonresponsive breast cancer cells.
  
  
  METHODS
  Cytotoxic activity of SCS and tamoxifen in MCF-7 and MDA-MB-231 human breast cancer cells was determined using lactate dehydrogenase release assay and synergism was evaluated using the CalcuSyn software. Apoptosis was quantified by flow cytometry following Annexin V and propidium iodide staining. Cells were also stained with JC-1 dye to determine changes in the mitochondrial membrane potential. Fluorescence imaging using FAM-FLICA assay detects caspase-8 and caspase-9 activities. DNA damage in the non-malignant breast epithelial cell line, MCF-10A, was evaluated using Comet assay.
  
  
  RESULTS
  The combined SCS and tamoxifen treatment displayed strong synergistic inhibition of MCF-7 and MDA-MB-231 cell growth at low doses of the antiestrogen. SCS further promoted the tamoxifen-induced apoptosis that was associated with modulation of mitochondrial membrane potential and activation of caspase-8 and caspase-9, suggesting the involvement of intrinsic and extrinsic signaling pathways. Interestingly, the non-malignant MCF-10A cells displayed no cytotoxicity or DNA damage when treated with either SCS or SCS-tamoxifen combination.
  
  
  CONCLUSIONS
  The combined use of SCS and lower tamoxifen dose could potentially reduce the side effects/toxicity of the drug. However, further studies are needed to determine the effectiveness and safety of the combination treatment in vivo.
authors.affiliation: Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia. niksoriani@usm.my.
authors.forename: Nik Soriani
authors.initials: NS
authors.lastname: Yaacob
authors.forename: Nik Nursyazni Nik Mohamed
authors.initials: NN
authors.lastname: Kamal
authors.forename: Mohd Nor
authors.initials: MN
authors.lastname: Norazmi
mesh_terms: D027901:Acanthaceae / Q000737:chemistry*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D010936:Plant Extracts / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D013629:Tamoxifen / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D010936:Plant Extracts; D013629:Tamoxifen