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p53 mutations associated with increased sensitivity to ionizing radiation in human head and neck cancer cell lines
K Servomaa1, A Kiuru, R Grénman
1Research Department, Finnish Centre for Radiation and Nuclear Safety, Helsinki, Finland.
Abstract:
The p53 tumour suppressor gene is activated following cellular exposure to DNA-damaging agents. The functions of wild-type p53 protein include transient blocking of cell cycle progression, direct or indirect stimulation of DNA repair machinery and triggering of apoptosis if DNA repair fails. Therefore, the status of p53 protein may be critically associated with tumour cell radiosensitivity. In the present study we examine the intrinsic radiosensitivity of 20 human carcinoma cell lines derived from 15 patients with different types of head and neck tumour. Radiosensitivities were measured in a 96-well plate clonogenic assay in terms of the mean inactivation dose, surviving fraction at 2 Gy, and constants alpha and beta in the linear quadratic survival curve. The p53 allele status was determined by amplifying exons 4-10 by the polymerase chain reaction (PCR), screening for mutations using single-strand conformation polymorphism (SSCP) analysis and determining the exact type and location of a mutation by direct sequencing. The results showed that prevalence of p53 mutations in squamous cell carcinoma (SCC) cell lines is high (80%), and that deletion of one or both wild-type alleles is common (75%). Intrinsic radiosensitivity of the cell lines varied greatly in terms of mean inactivation dose, from 1.4 +/- 0.1 to 2.6 +/- 0.2 Gy. Radiosensitivity correlated well with the p53 allele status so that cell lines carrying a wild-type p53 allele were significantly (P < 0.01) more radioresistant (mean inactivation dose 2.23 +/- 0.15 Gy) than cell lines which lacked a wild-type gene (1.82 +/- 0.24 Gy). Evaluation of our own results and those published in the literature lead us to conclude that absence of the wild-type p53 allele in human head and neck cancer cell lines is associated with increased radiosensitivity. However, the sensitivity is also strongly dependent on the exact type and location of the p53 mutation.
Insights
Head and neck cancer cells with a non-functional p53 gene show increased radiosensitivity. Loss of wild-type p53 alleles significantly impacts tumor cell radiosensitivity, though mutation type and location also play a role.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The p53 tumor suppressor gene plays a crucial role in cellular response to DNA damage.
- Wild-type p53 protein functions include cell cycle arrest, DNA repair promotion, and apoptosis induction.
- p53 status is potentially linked to tumor cell radiosensitivity, a key factor in head and neck cancer treatment.
Purpose of the Study:
- To investigate the intrinsic radiosensitivity of human head and neck carcinoma cell lines.
- To determine the association between p53 gene status and radiosensitivity in these cell lines.
Main Methods:
- Utilized 20 human head and neck carcinoma cell lines from 15 patients.
- Assessed radiosensitivity using a 96-well plate clonogenic assay, measuring mean inactivation dose and other parameters.
- Determined p53 allele status through polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP) analysis, and direct sequencing.
Main Results:
- High prevalence of p53 mutations (80%) and wild-type allele deletions (75%) observed in squamous cell carcinoma lines.
- Significant variation in intrinsic radiosensitivity among cell lines (mean inactivation dose 1.4–2.6 Gy).
- Cell lines lacking a wild-type p53 allele exhibited significantly higher radiosensitivity (mean inactivation dose 1.82 Gy) compared to those with a wild-type allele (2.23 Gy).
Conclusions:
- Absence of a wild-type p53 allele is associated with increased radiosensitivity in human head and neck cancer cell lines.
- The specific type and location of p53 mutations also influence radiosensitivity.
- Findings suggest p53 status is a critical determinant of radiosensitivity in head and neck cancers.