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TPX2 in malignantly transformed human bronchial epithelial cells by anti-benzo[a]pyrene-7,8-diol-9,10-epoxide
Lijuan Zhang1, He Huang, Luyao Deng
1Department of Toxicology, School of Public Health, Peking University, PR China.
Abstract:
In order to elucidate the function of the targeting protein for Xenopus kinesin-like protein 2 (Xklp2) (TPX2) in the malignant transformation of human bronchial epithelial cells induced by anti-benzo[a]pyrene-trans-7, 8-dihydrodiol-9, 10-epoxide (anti-BPDE), TPX2 was characterized in cells at both the gene and the protein levels. TPX2 was present at higher levels in 16HBE-C cells than in 16HBE cells as demonstrated by two-dimensional gel electrophoresis, immunocytochemistry, Western blot analysis and RT-PCR. TPX2 was also detected in lung squamous-cell carcinoma tissues by immunohistochemistry, but not in normal lung tissues. Depression of TPX2 by RNA interference in 16HBE-C cells led to a decrease in cell proliferation, S-phase cell cycle arrest and cell apoptosis. Abnormal TPX2 tyrosine phosphorylation was detected in 16HBE-C cells, and this could be inhibited, to different degrees, by tyrosine kinase inhibitors. Inhibiting tyrosine phosphorylation in 16HBE-C cells by three selected tyrosine protein kinase inhibitors, tyrphostin 47, AG112 and AG555, caused G(0)/G(1)-phase cell cycle arrest. Our results suggest that anti-BPDE can cause the over-expression of TPX2 and its aberrant tyrosine phosphorylation. Misregulation of TPX2 affects the cell cycle state, proliferation rates and apoptosis.
Insights
Targeting protein for Xenopus kinesin-like protein 2 (TPX2) is overexpressed in lung cancer cells exposed to anti-benzo[a]pyrene-trans-7, 8-dihydrodiol-9, 10-epoxide (anti-BPDE). Inhibiting TPX2 reduces proliferation and induces apoptosis, suggesting its role in malignant transformation.
Area of Science:
- Cell Biology
- Molecular Oncology
- Carcinogenesis
Background:
- Benzo[a]pyrene diol epoxide (BPDE) is a carcinogen that induces malignant transformation in human bronchial epithelial cells.
- Targeting protein for Xenopus kinesin-like protein 2 (TPX2) is implicated in cell division and cancer progression.
Purpose of the Study:
- To investigate the role of TPX2 in the malignant transformation of human bronchial epithelial cells induced by anti-BPDE.
- To characterize TPX2 expression and phosphorylation in normal and cancerous lung cells.
Main Methods:
- Gene and protein expression analysis (RT-PCR, 2D-PAGE, Western blot, immunocytochemistry).
- RNA interference to suppress TPX2 levels.
- Treatment with tyrosine kinase inhibitors.
- Cell cycle analysis and apoptosis assays.
Main Results:
- TPX2 was upregulated in anti-BPDE-transformed cells (16HBE-C) and lung squamous-cell carcinoma tissues compared to normal cells/tissues.
- TPX2 knockdown reduced cell proliferation, induced S-phase arrest, and promoted apoptosis.
- Abnormal tyrosine phosphorylation of TPX2 was observed and could be inhibited by tyrosine kinase inhibitors, leading to G(0)/G(1) cell cycle arrest.
Conclusions:
- Anti-BPDE induces TPX2 overexpression and aberrant tyrosine phosphorylation in bronchial epithelial cells.
- Misregulation of TPX2 impacts cell cycle progression, proliferation, and apoptosis, contributing to lung carcinogenesis.
