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

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.

Mutations of the BRAF Gene in Papillary Thyroid Carcinoma in a Korean Population

The B-type Raf kinase (BRAF) protein is a serine/threonine kinase that has an important role in cellular proliferation, differentiation, and programmed cell death. The BRAF gene has been recently found to be mutated in human carcinomas, predominantly in malignant melanoma. The aim of this study was to investigate the frequency of the BRAF mutation in papillary thyroid carcinoma (PTC) of Koreans through direct DNA sequencing of the polymerase chain reaction (PCR) - amplified exon 15 with clinicopathological features. Seventy paraffin-embedded conventional papillary carcinomas in the thyroid gland were evaluated. The BRAF missense mutation at V599E was found in 58 of 70 PTCs (83%). The frequency of our series was much higher than the frequencies of other PTC series (36 - 69%). The frequency of nodal metastasis was also significantly higher in the BRAF mutation group (p= 0.048). These results suggest that the BRAF mutation is involved in the carcinogenesis in most conventional PTCs, especially those occurring in Koreans, and this is a potentially valuable marker for the evaluation of prognosis of patients with PTC. These findings support the specific inhibitors of BRAF being promising targets for the disease outcome.