Gene therapy with E2F-1 up-regulates the protein kinase PKR and inhibits growth of leiomyosarcoma in vivo.
Overexpression of the transcription factor E2F-1 induces apoptosis in a variety of carcinoma cells and inactivates murine double minute protein 2, a factor associated with poor prognosis in soft tissue sarcomas. We have shown previously that the double-stranded RNA-activated protein kinase PKR plays an important role in mediating this apoptotic response in carcinoma cells to E2F-1. We sought to evaluate the potential of E2F-1 gene therapy in soft tissue sarcomas and to study the involvement of PKR in the response to E2F-1 overexpression in mesenchymal cells. A replication-deficient adenovirus carrying the E2F-1 gene (Ad5E2F) was used to induce E2F-1 overexpression in the p53 mutated leiomyosarcoma cell line, SKLMS-1. Western blot analysis confirmed E2F-1 overexpression and up-regulation of the antiapoptotic factor Bcl-2 48 hours following infection with Ad5E2F. Apoptosis in Ad5E2F-treated cells was confirmed by fluorescence-activated cell sorting analysis and by poly(ADP-ribose) polymerase cleavage and DNA fragmentation assays. Vector-dependent up-regulation of PKR correlated with the amount of Ad5E2F-induced apoptosis. In vivo treatment of SKLMS-1 tumor-bearing BALB/c mice with intratumoral injections of Ad5E2F at a dose of 2 x 10(10) viral particles resulted in significant inhibition in tumor growth compared with control-treated animals (P < 0.016). Complete disappearance of all tumors was seen in two of seven mice in the Ad5E2F-treated animals. Immunohistochemical analysis of tumor specimens showed overexpression of E2F-1 and up-regulation of PKR in Ad5E2F-treated tumors. These findings show that adenovirus-mediated overexpression of E2F-1 results in up-regulation of PKR and significant growth suppression of leiomyosarcomas in vivo. Taken together, these data suggest that E2F-1 gene therapy and PKR modulation might be a promising treatment strategy for these tumors that are highly resistant to conventional therapies.
Vorburger
Stephan A
SA
Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 444, Houston, Texas 77030-4009, USA.
Hetrakul
Nophadol
N
Xia
Weiya
W
Wilson-Heiner
Marcia
M
Mirza
Nadeem
N
Pollock
Raphael E
RE
Feig
Barry
B
Swisher
Stephen G
SG
Hunt
Kelly K
KK
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002469:Cell Separation; D053938:DNA Fragmentation; D050687:E2F1 Transcription Factor / Q000235:genetics* / Q000627:therapeutic use; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D007150:Immunohistochemistry; D007890:Leiomyosarcoma / Q000188:drug therapy* / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011379:Prognosis; D012330:RNA, Double-Stranded / Q000737:chemistry; D011994:Recombinant Proteins / Q000235:genetics; D012509:Sarcoma / Q000188:drug therapy; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D019892:eIF-2 Kinase / Q000096:biosynthesis*
D050687:E2F1 Transcription Factor; D012330:RNA, Double-Stranded; D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D011065:Poly(ADP-ribose) Polymerases; D019892:eIF-2 Kinase