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Effects of adenovirus-mediated p16INK4A expression on cell cycle arrest are determined by endogenous p16 and Rb
1Medicine Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
We constructed an adenoviral vector containing human p16 cDNA in order to evaluate the cytotoxic effects of exogenous p16 expression on cancer cell proliferation and to explore the potential use of p16 in cancer gene therapy. Following infection of human breast (MCF-7, MDA-MB-231, and BT549), osteosarcoma (U-2 OS and Saos-2), cervical (C33a), and lung cancer (H358) cell lines with the recombinant adenovirus Adp16, high levels of p16 expression were observed in all cell lines. Cancer cell lines which were mutant or null for p16 but wild-type for the retinoblastoma gene product (pRb) (MCF-7, MDA-MB-231, BT549 and U-2 OS) were 7-22-fold more sensitive to the cytotoxic effects of Adp16 than to a control virus. In contrast, cancer cell lines which were wild-type for p16 but mutant or null for pRb (Saos-2, C33a and H358) were
Insights
Exogenous p16 expression via Adp16 effectively reduced cancer cell proliferation, particularly in cells lacking p16 but retaining functional retinoblastoma protein (pRb). This indicates p16’s potential in targeted cancer gene therapy for specific tumor types.
Area of Science:
- Molecular Biology
- Cancer Research
- Gene Therapy
Background:
- The p16 protein is a key cell cycle regulator often inactivated in human cancers.
- Adenoviral vectors offer a promising delivery system for gene-based cancer therapies.
- Understanding p16's interaction with the retinoblastoma protein (pRb) is crucial for cancer treatment strategies.
Purpose of the Study:
- To assess the cytotoxic impact of introducing exogenous p16 into various cancer cell lines.
- To explore the feasibility of using p16 gene therapy for cancer treatment.
- To determine the role of functional pRb in p16-mediated cancer cell death.
Main Methods:
- Construction of an adenoviral vector (Adp16) expressing human p16 cDNA.
- Infection of diverse human cancer cell lines (breast, osteosarcoma, cervical, lung) with Adp16.
- Analysis of cell proliferation, DNA synthesis (5-bromodeoxyuridine incorporation), and protein interactions (p16, cyclin-dependent kinase 4, pRb).
Main Results:
- High p16 expression was achieved in all infected cancer cell lines.
- Cells with p16 deficiency but functional pRb showed significantly higher sensitivity (7-22 fold) to Adp16-induced cytotoxicity.
- Cell cycle arrest at S phase and pRb dephosphorylation were observed in p16-deficient cells with functional pRb, linked to p16 binding to CDK4.
Conclusions:
- p16-mediated cytotoxicity is dependent on the presence of functional pRb.
- Cancer cells that are mutant or null for p16 are suitable candidates for Adp16-mediated gene therapy.
- This study highlights a targeted approach for cancer gene therapy based on tumor-specific genetic profiles.