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Suppression of cancer cell growth by adenovirus expressing p21(WAF1/CIP1) deficient in PCNA interaction
N S Prabhu1, M V Blagosklonny, Y X Zeng
1Howard Hughes Medical Institute, Laboratory of Molecular Oncology, Chicago, Illinois, USA.
Abstract:
p53 tumor suppression is deficient in the majority of human cancers. Efforts to understand this pathway have identified cyclin-dependent kinase (CDK) inhibitors and suggested a potential for their replacement in human cancer. In the present studies, expression of a C-terminal deletion mutant of the human p21(WAF1/CIP1) CDK inhibitor completely suppressed the growth of colon cancer cells, whereas full-length p21 only partially suppressed growth. We prepared a replication-deficient adenoviral recombinant which expresses the p21 C-terminal mutant (Ad-WAF1-341) and compared its tumor suppressive abilities with Ad-p53 and Ad-LacZ. Ad-WAF1-341- and Ad-p53-infected cancer cells, but not Ad-LacZ-infected cancer cells, expressed a nuclear protein recognized by anti-p21 antibody and were deficient in cell cycle progression. The exogenous p21 mutant interacted with CDK2 but not proliferating cell nuclear antigen following infection of p21-/- cancer cells. Ad-WAF1-341 was more potent than Ad-p53 in inhibiting DNA synthesis in human papillomavirus 16 E6-expressing cancer cells. Most importantly, the Ad-WAF1-341-infected E6-expressing cells died, whereas most of the Ad-p53-infected cells continued to proliferate. Endonucleolytic cleavage of DNA was observed in Ad-WAF1-341-infected cancer cells. These observations suggest that Ad-WAF1-341 should be evaluated in the treatment of human papillomavirus-associated neoplasia and other neoplasias resistant to p53.
Insights
A novel p21 C-terminal mutant, delivered via Ad-WAF1-341, shows potent cancer suppression by inhibiting cell cycle progression and inducing DNA damage. This mutant is more effective than p53 in certain human papillomavirus-associated cancers.
Area of Science:
- Oncology
- Molecular Biology
- Virology
Background:
- p53 tumor suppression is frequently lost in human cancers.
- Cyclin-dependent kinase (CDK) inhibitors are being explored as cancer therapeutics.
- Understanding p53 pathway deficiencies is crucial for developing new cancer treatments.
Purpose of the Study:
- To investigate the tumor suppressive potential of a C-terminal deletion mutant of p21(WAF1/CIP1).
- To compare the efficacy of a recombinant adenovirus expressing the p21 mutant (Ad-WAF1-341) against Ad-p53 and Ad-LacZ.
- To evaluate Ad-WAF1-341 in treating human papillomavirus (HPV)-associated cancers and p53-resistant neoplasias.
Main Methods:
- Preparation of a replication-deficient adenoviral recombinant expressing the p21 C-terminal mutant (Ad-WAF1-341).
- Infection of cancer cells with Ad-WAF1-341, Ad-p53, and Ad-LacZ.
- Assessment of protein expression, cell cycle progression, DNA synthesis inhibition, and DNA cleavage.
- Analysis of p21 mutant interaction with CDK2 and proliferating cell nuclear antigen (PCNA).
Main Results:
- The p21 C-terminal mutant completely suppressed colon cancer cell growth, outperforming full-length p21.
- Ad-WAF1-341 and Ad-p53 infected cells showed nuclear p21 expression and impaired cell cycle progression.
- The p21 mutant interacted with CDK2 but not PCNA in p21-/- cells.
- Ad-WAF1-341 was more potent than Ad-p53 in inhibiting DNA synthesis in HPV E6-expressing cells.
- Ad-WAF1-341 induced cell death and DNA cleavage in E6-expressing cells, unlike Ad-p53.
Conclusions:
- The p21 C-terminal mutant (Ad-WAF1-341) exhibits significant tumor suppressive activity, including inducing apoptosis.
- Ad-WAF1-341 demonstrates superior efficacy compared to Ad-p53 in HPV-associated cancer models.
- Ad-WAF1-341 warrants further investigation for treating HPV-associated neoplasias and p53-resistant cancers.