title: Modulation of telomerase and signal transduction proteins by hexyl-ALA-photodynamic therapy (PDT) in human doxorubicin resistant cancer cell models.
abstract: OBJECTIVE
  This study employed a doxorubicin resistant (MES-SA-Dx5) human uterine sarcoma cell line and its counterpart (MES-SA), to elucidate the efficacy of aminolevulinic acid-hexylester (hexyl-ALA) mediated PDT at molecular and transcriptional levels.
  
  
  METHODS
  Hexyl-ALA generated protoporphyrin IX in both cells were determined by molecular probes using Confocal Laser Scanning Microscopy. The hexyl-ALA-PDT induced signal transduction proteins and mode of cell death were quantitated by CASE ELISA assays and DAPI staining. The modulation of hTERT mRNA expression and telomerase activity were investigated by TaqMan real-time PCR and ELISA respectively. Hexyl-ALA-PDT mediated cell migratory effect was determined by wound-healing assay.
  
  
  RESULTS
  The results demonstrated that mitochondria were the major target of hexyl-ALA. At LD(30), hexyl-ALA-PDT significantly provoked an up-regulation of phosphorylated p38MAPK and JNK proteins in both cells. Hexyl-ALA-PDT down-regulated hTERT (a catalytic subunit of telomerase) mRNA expression and showed a strong correlation with diminished telomerase activity in both cells (MES-SA: r(2) = 0.9932; MES-SA-Dx5: r(2) = 0.9775). The suppression of cell migratory effect in both cells was obtained after hexyl-ALA-PDT. Further, 50% and 30% of apoptotic cells were attained at LD(50), for wild-type and drug resistant cells respectively. Unlike the wild-type, a higher PDT dose was crucial to induce apoptosis in the drug resistant cells.
  
  
  CONCLUSIONS
  Our study provides the first evidence that p38MAPK and JNK kinases played a vital role in triggering hexyl-ALA-PDT-induced apoptosis, down-regulated hTERT mRNA expression and telomerase activity in both proposed cells. In vivo studies are worth examining for the benefit of clinical applications in drug resistant cancers and PDT development.
authors.affiliation: Medical Laboratory Science Section, Department of Health Technology & Informatics, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region, Kowloon.
authors.forename: Ellie S M
authors.initials: ES
authors.lastname: Chu
authors.forename: Christine M N
authors.initials: CM
authors.lastname: Yow
mesh_terms: D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D006801:Humans; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D015398:Signal Transduction / Q000187:drug effects*; D019098:Telomerase / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014594:Uterine Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology
chemical_list: D017319:Photosensitizing Agents; D014157:Transcription Factors; D004317:Doxorubicin; D000622:Aminolevulinic Acid; D019098:Telomerase; C419924:5-aminolevulinic acid hexyl ester