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(Arteriosclerosis, Thrombosis, and Vascular Biology. 1997;17:947-953.)
© 1997 American Heart Association, Inc.

Articles

Cellular Radiosensitivity, Radioresistant DNA Synthesis, and Defect in Radioinduction of p⁵³ in Fibroblasts From Atherosclerosis Patients

Nargis Nasrin; Layth A. Mimish; Pulicat S. Manogaran; Mohammed Kunhi; David Sigut; Sultan Al-Sedairy; ; Mohammed A. Hannan

From the Department of Biological and Medical Research (N.N., P.S.M., M.K., D.S., S.A.-S., M.A.H.), and the Department of Cardiovascular Diseases (L.A.M.), King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.

Correspondence to Dr Mohammed A. Hannan, Biological and Medical Research (MBC-03), King Faisal Specialist Hospital and Research Centre, PO Box 3354, Riyadh 11211, Saudi Arabia.

Abstract Earlier studies have suggested that both cancer and atherosclerosis may follow a common pathway in the early stage of development and share certain risk factors. One report indicated that the gene responsible for the radiosensitive, cancer-prone, multisystem disorder ataxia telangiectasia (AT) may increase the risk of developing ischemic heart disease. The present studies were carried out to find similarities, if any, between atherosclerosis patients and AT homozygotes or heterozygotes (ATHs) in their cellular/molecular response to ionizing radiation, which acts as a carcinogen as well as an atherogen. Fibroblast cell strains developed from healthy subjects and from AT homozygotes, ATHs, and atherosclerosis patients were compared for (1) survival, by the colony-forming assay and (2) DNA synthesis inhibition after irradiation, determined by [³H]thymidine incorporation, cell cycle distribution, and the expression of p⁵³ and p²¹ proteins, analyzed by flow cytometry. Fibroblasts from the atherosclerosis patients as a group, compared with the healthy subjects, showed enhanced sensitivity to chronic (low-dose-rate) irradiation. A majority of the cell strains representing atherosclerosis patients exhibited varying degrees of radioresistant DNA synthesis (RDS), with roughly 33% showing an AT-like and the rest an ATH-like response. All cell strains with an AT-like and one quarter with an ATH-like RDS were found to be defective in the radioinduction of both p⁵³ and p²¹ proteins, which are concerned with cell cycle regulation. An absence of G₁ arrest after irradiation was observed in cell strains lacking a radioinduced expression of p⁵³ and p²¹. Cellular/ molecular defects leading to increased radiosensitivity, reduced induction of p⁵³/p²¹, and cell cycle deregulation found to be associated with cancer-prone disorders such as AT may constitute important risk factors for atherosclerosis as well.

Key Words: atherosclerosis • radiosensitivity • cell cycle defect • radioresistant DNA synthesis • radioinduced p⁵³ and p²¹ proteins

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