Caspase Activation and Changes in Bcl-2 Family Member Protein Expression Associated with E2F-1-mediated Apoptosis in Human Esophageal Cancer Cells

• Published in: Clinical cancer research Vol. 6; no. 4; pp. 1579 - 1589
• Main Authors: Yang, H L, Dong, Y B, Elliott, M J, Liu, T J, McMasters, K M
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.04.2000
• Subjects: Adenoviridae - genetics; Apoptosis; bcl-X Protein; Biological and medical sciences; Carrier Proteins; Caspases - metabolism; Cell Cycle; Cell Cycle Proteins; Cell Death; Cell Division; Cell Survival; DNA, Recombinant - genetics; DNA-Binding Proteins; E2F Transcription Factors; E2F1 Transcription Factor; Enzyme Activation; Esophageal Neoplasms - genetics; Esophageal Neoplasms - metabolism; Esophageal Neoplasms - pathology; Esophagus; Gastroenterology. Liver. Pancreas. Abdomen; Gene Expression Regulation, Neoplastic; Genetic Vectors; Humans; Medical sciences; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins - biosynthesis; Proto-Oncogene Proteins c-bcl-2 - biosynthesis; Retinoblastoma Protein - biosynthesis; Retinoblastoma-Binding Protein 1; Transcription Factor DP1; Transcription Factors - genetics; Transcription Factors - physiology; Tumor Cells, Cultured; Tumor Suppressor Protein p53 - genetics; Tumors; Antineoplastic agent; Human; Cell proliferation; Adenoviridae; Enzyme; Cysteine endopeptidases; Esophageal disease; DNA binding protein; Gene overexpression; Malignant tumor; Gene expression; In vitro; Biological activity; Esophagus; Virus; Peptidases; Enzymatic activity; Established cell line; Digestive diseases; Hydrolases; Infected cell; Transcription factor; Mechanism of action; Apoptosis
• ISSN: 1078-0432; 1557-3265

The prognosis for patients with esophageal cancer remains poor, prompting the search for new treatment strategies. Overexpression of E2F-1 has been shown to induce apoptosis in several cancer cell types. In the present study, the effect of adenovirus-mediated E2F-1 overexpression on human esophageal cancer cell lines Yes-4 and Yes-6 was evaluated. Cells were treated by mock infection, infection with an adenoviral vector expressing β-galactosidase (Ad5CMV-LacZ), or E2F-1 (Ad5CMVE2F-1). Western blot analysis confirmed marked overexpression of E2F-1 in Ad5CMVE2F-1-infected cells. Overexpression of E2F-1 resulted in marked growth inhibition and rapid loss of cell viability due to apoptosis, although Yes-6 cells were somewhat more resistant to E2F-1-mediated growth inhibition than Yes-4 cells. Cell cycle analysis revealed that overexpression of E2F-1 led to G 2 arrest, followed by apoptotic cell death. p53 expression remained undetectable in both cell lines after E2F-1 overexpression. The apoptosis inhibitor proteins of the Bcl-2 gene family, Bcl-2, Mcl-1, and Bcl-XL, decreased at 48 h after infection in Yes-4 cells, but remained unchanged in Yes-6 cells. Levels of retinoblastoma gene product (pRb) declined at 48 h after E2F-1 infection in Yes-4 cells, at which apoptosis predominated, whereas pRb expression remained constant in Yes-6 cells. Expression of p14 ARF did not change after E2F-1 infection in either cell line. Involvement of caspase 3 and caspase 6 in E2F-1-mediated apoptosis was demonstrated by cleavage of caspase 3/CPP32 and poly-ADP-ribose polymerase, as well as fragmentation of the caspase 6 substrate, lamin B. These results indicate that the sensitivity of esophageal cancer cells to E2F-1-mediated apoptosis may be related to differential expression of Bcl-2 family member proteins and suggest that the adenovirus-mediated E2F-1 gene therapy may be a promising treatment strategy for the treatment of this disease.