Treatment of radioresistant stem-like esophageal cancer cells by an apoptotic gene-armed, telomerase-specific oncolytic adenovirus.
OBJECTIVE
Radioresistance may be caused by cancer stem cells (CSC). Because CSCs require telomerase to proliferate, a telomerase-specific oncolytic adenoviral vector carrying apoptotic tumor necrosis factor-related apoptosis-inducing ligand and E1A gene (Ad/TRAIL-E1) may preferentially target CSCs.


METHODS
We established two pairs of parental and radioresistant (R) esophageal carcinoma cell lines (Seg-1, Seg-1R and TE-2, TE-2R) by fractionated irradiation. Stem cell markers were measured by Western blotting and flow cytometry. Serial sorting was used to enrich stem-like side population cells. Telomerase activity, transgene expression, antitumor activity, apoptosis induction, and viral replication were determined in vitro and/or in vivo.


RESULTS
Expression of the stem cell markers beta-catenin, Oct3/4, and beta(1) integrin in Seg-1R cells was 29.4%, 27.5%, and 97.3%, respectively, compared with 4.8%, 14.9%, and 45.3% in Seg-1 cells (P < 0.05). SP levels in Seg-1R and TE-2R cells were 14.6% and 2.7%, respectively, compared with 3.4% and 0.3% in Seg-1 and TE-2 cells. Serial sorting of Seg-1R SP cells showed enrichment of the SP cells. Telomerase activities in Seg-1R, Seg-1R SP, and TE-2R cells were significantly higher than in Seg-1, Seg-1R non-SP, and TE-2 cells, respectively (P < 0.05). Seg-1R and TE-2R cells were more sensitive to Ad/TRAIL-E1 than parental cells. Increased Coxsackie-adenovirus receptor and elevated transgene expressions were found in the radioresistant cells. Ad/TRAIL-E1 resulted in significant tumor growth suppression and longer survival in Seg-1R-bearing mice (P < 0.05) with no significant toxicity.


CONCLUSIONS
Radioresistant cells established by fractionated irradiation display CSC-like cell properties. Ad/TRAIL-E1 preferentially targets radioresistant CSC-like cells.
Zhang
Xiaochun
X
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Komaki
Ritsuko
R
Wang
Li
L
Fang
Bingliang
B
Chang
Joe Y
JY
D000256:Adenoviridae / Q000235:genetics*; D017500:Adenovirus E1A Proteins / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D004938:Esophageal Neoplasms / Q000378:metabolism / Q000473:pathology / Q000628:therapy* / Q000821:virology; D005260:Female; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D039641:Integrin beta Chains / Q000378:metabolism; D051379:Mice; D014411:Neoplastic Stem Cells / Q000166:cytology; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D050130:Oncolytic Virotherapy; D050504:Oncolytic Viruses / Q000235:genetics*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics* / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
D017500:Adenovirus E1A Proteins; D039641:Integrin beta Chains; D050814:Octamer Transcription Factor-3; D053221:TNF-Related Apoptosis-Inducing Ligand; D051176:beta Catenin; D019098:Telomerase