title: Cooperative antiproliferative effect of coordinated ectopic expression of DLC1 tumor suppressor protein and silencing of MYC oncogene expression in liver cancer cells: Therapeutic implications.
abstract: Human hepatocellular carcinoma (HCC) is one of the most common types of cancer and has a very poor prognosis; thus, the development of effective therapies for the treatment of advanced HCC is of high clinical priority. In the present study, the anti-oncogenic effect of combined knockdown of c-Myc expression and ectopic restoration of deleted in liver cancer 1 (DLC1) expression was investigated in human liver cancer cells. Expression of c-Myc in human HCC cells was knocked down by stable transfection with a Myc-specific short hairpin (sh) RNA vector. DLC1 expression in Huh7 cells was restored by adenovirus transduction, and the effects of DLC1 expression and c-Myc knockdown on Ras homolog gene family, member A (RhoA) levels, cell proliferation, soft agar colony formation and cell invasion were measured. Downregulation of c-Myc or re-expression of DLC1 led to a marked reduction in RhoA levels, which was associated with decreases in cell proliferation, soft agar colony formation and invasiveness; this inhibitory effect was augmented with a combination of DLC1 transduction and c-Myc suppression. To determine whether liver cell-specific delivery of DLC1 was able to enhance the inhibitory effect of c-Myc knockdown on tumor growthin vivo, DLC1 vector DNA complexed with galactosylated polyethylene glycol-linear polyethyleneimine was administered by tail vein injection to mice bearing subcutaneous xenografts of Huh7 cells transfected with shMyc or control shRNA. A cooperative inhibitory effect of DLC1 expression and c-Myc knockdown on the growth of Huh7-derived tumors was observed, suggesting that targeted liver cell delivery of DLC1 and c-Myc shRNA may serve as a possible gene therapy modality for the treatment of human HCC.
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 2089-4262, USA; Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Development, Bethesda, MD 2089-4262, USA.
authors.forename: Xuyu
authors.initials: X
authors.lastname: Yang
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 2089-4262, USA; Laboratory of Cancer Biology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD 2089-4262, USA.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Medicine, Richmond University Medical Center, Staten Island, NY 10310, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Tone
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 2089-4262, USA; Laboratory of Cellular Oncology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4262, USA.
authors.forename: Marian E
authors.initials: ME
authors.lastname: Durkin
authors.affiliation: Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 2089-4262, USA; Laboratory of Cellular Oncology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4262, USA.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Popescu
keywords: Ras homolog gene family guanosine triphosphatase; c-Myc; deleted in liver cancer 1; hepatocellular carcinoma; tumorigenesis