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Expression of Wild-type and Mutant p16 in H460 Cell Line
1The Army Key laboratory of Medical Molecular Genetics, Second Military Medical University, Shanghai 200433, China.
Abstract:
Two p16 mutants, P48L and D74N, were obtained by site-directed mutagenesis using two step PCR method. Mutant p16 cDNA and wild-type p16 cDNA were colned into the mammalian expression vector pcDNA3 to construct p16 expression vector pCMV-p16, pCMV-p16P48L and pCMV-p16D74N, respectively. After the introduction of these expression vectors into human lung cancer cell line H460 in which endogenous p16 gene was homozygously deleted, exogenous p16 expression was detected in G418 resistant cells by Northern blotting and immunocytochemistry staining. The results of immunofluorescence and immunocytochemistry staining showed that the P16 protein was located in the cell cytoplasm. The p16 cDNAs amplificated from the genomic DNA of recombinant H460 cell lines indicated that the plasmid p16 cDNA was integrated into the chromosome of cell lines. That the over expression of wild-type p16 caused G1 arrest suggested the wild-type P16 protein expressed in H460 cell line to be a functional protein.
Insights
Researchers created p16 mutants to study its function in lung cancer. Overexpressing wild-type p16 in cancer cells caused cell cycle arrest, confirming its tumor suppressor activity.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- The p16 gene is a crucial tumor suppressor involved in cell cycle regulation.
- Homozygous deletion of the p16 gene is observed in various cancers, including lung cancer.
- Understanding p16 protein function is vital for developing targeted cancer therapies.
Purpose of the Study:
- To generate and characterize p16 mutants (P48L and D74N) using site-directed mutagenesis.
- To investigate the expression and localization of wild-type and mutant p16 proteins in a human lung cancer cell line (H460) with a deleted endogenous p16 gene.
- To assess the functional impact of wild-type p16 overexpression on cell cycle progression.
Main Methods:
- Site-directed mutagenesis and two-step PCR were employed to create p16 mutants.
- Mammalian expression vectors (pCMV-p16, pCMV-p16P48L, pCMV-p16D74N) were constructed.
- Transfection into H460 lung cancer cells, followed by G418 selection.
- Gene expression analysis using Northern blotting.
- Protein expression and localization determined by immunocytochemistry and immunofluorescence staining.
- Confirmation of plasmid integration into host cell chromosomes via PCR amplification.
Main Results:
- Exogenous wild-type and mutant p16 proteins were successfully expressed in H460 cells.
- Immunofluorescence and immunocytochemistry confirmed p16 protein localization in the cell cytoplasm.
- Northern blotting and PCR analysis verified successful gene expression and chromosomal integration of the p16 cDNA.
- Overexpression of wild-type p16 induced G1 phase cell cycle arrest in H460 cells.
Conclusions:
- The wild-type p16 protein, when expressed in H460 cells, demonstrates functional tumor suppressor activity by inducing cell cycle arrest.
- The generated p16 mutants provide tools for further investigation into structure-function relationships.
- These findings contribute to understanding p16's role in lung cancer pathogenesis and potential therapeutic strategies.