J Korean Soc Ther Radiol Oncol.  2005 Mar;23(1):51-60.

The Modulation of Radiosensitivity by Combined Treatment of Selective COX-2 Inhibitor, NS 398 and EGF Receptor Blocker AG 1478 in HeLa Cell Line

• Youn SM
• Oh YK
• Kim JH
• Park MJ
• Seong IO
• Kang K
• Chai G

Abstract

PURPOSE: Selective inhibition of multiple molecular targets may improve the antitumor activity of radiation. Two specific inhibitors of selective cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) were combined with radiation on the HeLa cell line. To investigate cooperative mechanism with selective COX-2 inhibitor and EGFR blocker, in vitro experiments were done. MATERIASL AND METHODS: Antitumor effect was obtained by growth inhibition and apoptosis analysis by annexin V-Flous method. Radiation modulation effects were determined by the clonogenic cell survival assay. Surviving fractions at 2 Gy (SF2) and dose enhancement ratio at a surviving fraction of 0.25 were evaluated. To investigate the mechanism of the modulation of radiosensitivity, the cell cycle analyses were done by flow cytometry. The bcl-2 and bax expressions were analyzed by western blot.
RESULTS
A cooperative effect were observed on the apoptosis of the HeLa cell line when combination of the two drugs, AG 1478 and NS 398 with radiation at the lowest doses, apoptosis of 22.70% compare with combination of the one drug with radiation, apoptosis of 8.49 %. In cell cycle analysis, accumulation of cell on G0/G1 phase and decrement of S phase fraction was observed from 24 hours to 72 hours after treatment with radiation, AG 1478 and NS 398. The combination of NS 398 and AG 1478 enhanced radiosensitivity in a concentration-dependent manner in HeLa cells with dose enhancement ratios of 3.00 and SF2 of 0.12 but the combination of one drug with radiation was not enhanced radiosensitivity with dose enhancement ratios of 1.12 and SF2 of 0.68 (p=0.005). The expression levels of bcl-2 and bax were reduced when combined with AG 1478 and NS 398.
CONCLUSION
Our results indicate that the selective COX-2 inhibitor and EGFR blocker combined with radiation have potential additive or cooperative effects on radiation treatment and may act through various mechanisms including direct inhibition of tumor cell proliferation, suppression of tumor cell cycle progression and inhibition of anti-apoptotic proteins.

Keyword

Selective COX-2 inhibitor; EGFR blocker; Radiation; HeLa cell line

MeSH Terms

Apoptosis
Apoptosis Regulatory Proteins
Blotting, Western
Cell Cycle
Cell Proliferation
Cell Survival
Cyclooxygenase 2
Epidermal Growth Factor*
Flow Cytometry
HeLa Cells*
Humans
Radiation Tolerance*
Receptor, Epidermal Growth Factor*
S Phase
Apoptosis Regulatory Proteins
Cyclooxygenase 2
Epidermal Growth Factor
Receptor, Epidermal Growth Factor