Effects of gamma irradiation on cell cycle, apoptosis and telomerase activity in p53 wild‑type and deficient HCT116 colon cancer cell lines

Halacli,Sevil   Oskay; Canpinar,Hande; Cimen,Eren; Sunguroglu,Asuman

doi:10.3892/ol.2013.1441

Effects of gamma irradiation on cell cycle, apoptosis and telomerase activity in p53 wild‑type and deficient HCT116 colon cancer cell lines

Authors:
- Sevil Oskay Halacli
- Hande Canpinar
- Eren Cimen
- Asuman Sunguroglu
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Affiliations: Pediatric Immunology Unit, Institute of Children's Health, Hacettepe University, Sihhiye, Ankara 06100, Turkey, Department of Basic Oncology, Institute of Oncology, Hacettepe University, Sihhiye, Ankara 06100, Turkey, Pediatric Hematology Unit, Institute of Children's Health, Hacettepe University, Sihhiye, Ankara 06100, Turkey, Department of Medical Biology, Faculty of Medicine, Ankara University, Sihhiye, Ankara 06100, Turkey
Published online on: July 3, 2013 https://doi.org/10.3892/ol.2013.1441
Pages: 807-810

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Abstract

Radiotherapy serves as adjunctive treatment to chemotherapy and surgical resection of colorectal cancer. However, the cellular response to irradiation varies depending on the expression of tumor suppressor p53, which plays a significant role in the regulation of cell cycle arrest, apoptosis and telomerase activity in various cancers. The present study aimed to investigate cell cycle arrest, apoptosis and telomerase activity with respect to p53 expression in p53 wild‑type (+/+) and deficient (-/-) HCT116 colon cancer cell lines following 5 Gy γ‑irradiation. Cell cycle arrest and apoptosis were evaluated using flow cytometry. The telomerase activity was measured using a TRAP (telomerase repeat amplification protocol) assay. Following treatment with irradiation, G1/S cell cycle arrest occurred in the p53+/+ cells, whereas the p53-/- cells accumulated in the G2 phase. No differences were observed in the apoptotic ratios between the two cell lines following irradiation. Decreased telomerase activity was observed in the p53+/+ cells, whereas telomerase activity was increased in the p53-/- cells. The results showed that while telomerase activity and G1 cell cycle arrest were regulated depending on the p53 status, G2 arrest and the apoptotic response were promoted via a p53‑independent pathway.

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