title: Combination of hepatocyte specific delivery and transformation dependent expression of shRNA inducing transcriptional gene silencing of c-Myc promoter in hepatocellular carcinoma cells.
abstract: BACKGROUND
  A specific targeting modality for hepatocellular carcinoma (HCC) could ideally encompass a liver cell specific delivery system of a transcriptional unit that is active only in neoplastic cells. Sendai virosomes, derived from Sendai viral envelopes, home to hepatocytes based on the liver specific expression of asialoglycoprotein receptors (ASGPRs) which are recognized by the Sendai virosomal fusion (F) proteins. As reported earlier by us and other groups, transcriptional gene silencing (TGS) does not require continuous presence of the effector siRNA/shRNA molecule and is heritable, involving epigenetic modifications, leading to long term transcriptional repression. This could be advantageous over conventional gene therapy approaches, since continuous c-Myc inactivation is required to suppress hepatocarcinoma cells.
  
  
  METHODS
  Exploiting such virosomal delivery, the alpha-fetoprotein (AFP) promoter, in combination with various tumour specific enhancers, was used to drive the expression of shRNA directed against ME1a1 binding site of the proto-oncogene c-Myc P2 promoter, in order to induce TGS in neoplastic liver cells.
  
  
  RESULTS
  The dual specificity achieved by the Sendai virosomal delivery system and the promoter/enhancer guided expression ensured that the shRNA inducing TGS was active only in liver cells that had undergone malignant transformation. Our results indicate that such a bimodal therapeutic system induced specific activation of apoptosis in hepatocarcinoma cells due to heterochromatization and increased DNA methylation of the CpG islands around the target loci.
  
  
  CONCLUSIONS
  The Sendai virosomal delivery system, combined with AFP promoter/enhancer expression machinery, could serve as a generalized mechanism for the expression of genes deleterious to transformed hepatocarcinoma cells. In this system, the epigenetic suppression of c-Myc could have an added advantage for inducing cell death in the targeted cells.
authors.forename: Mohammad Khalid
authors.initials: MK
authors.lastname: Zakaria
authors.forename: Imran
authors.initials: I
authors.lastname: Khan
authors.forename: Prashant
authors.initials: P
authors.lastname: Mani
authors.affiliation: Department of Biochemistry, All India Institute of Medical Sciences, New Delhi 110029, India. parthoaiims@hotmail.com.
authors.forename: Parthaprasad
authors.initials: P
authors.lastname: Chattopadhyay
authors.forename: Debi P
authors.initials: DP
authors.lastname: Sarkar
authors.forename: Subrata
authors.initials: S
authors.lastname: Sinha
mesh_terms: D000818:Animals; D016466:CHO Cells; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D018899:CpG Islands; D003412:Cricetulus; D019175:DNA Methylation; D020868:Gene Silencing; D015316:Genetic Therapy; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism* / Q000821:virology; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D029082:Sendai virus / Q000235:genetics; D022701:Virosomes; D000509:alpha-Fetoproteins / Q000235:genetics*
chemical_list: C000715470:MAS1 protein, human; C489427:MYC protein, human; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D022701:Virosomes; D000509:alpha-Fetoproteins
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