Effect of ~(60)Co gamma ray fractionated irradiation on growth and proliferation of nasopharyngeal carcinoma cell line CNE-2

OBJECTIVE:To observe the effects of 60Co gamma ray with different fractionated doses on the growth,cell cycle distribution,expression of Cyclin D1 and proliferating cell nuclear antigen(PCNA) of nasopharyngeal carcinoma cell line CNE-2. METHODS:CNE-2 cells were fractionated by irradiated with 0,2.0,4.0 and 6.0 Gy of 60Co gamma ray,respectively,one time per day for 5 days. MTT test and flow cytometry were used to detect the cell cycle. The expressions of Cyclin D1 and PCNA were detected by RT-PCR. RESULTS:The growth inhibiting ratios were -17.05%,4.01%,15.52% after 2.0,4.0 and 6.0 Gy of 60Co gamma ray fractionated irradiattion one time per day for 5 days,respectively. In all the radiation groups,the fraction of G1 phase cell decreased,and the S phase and G2/M phases cells increased (χ2=16.53,P0.001). With the fractionated dose increased,the expression of Cyclin D1 decreased gradually until it cannot expressed (P values were 0.035,0.022 and 0.000 respectively). In the 4.0 or 6.0 Gy fractionated radiation group,the cell growth inhibition occured and PCNA expression decreased in the CNE-2 cells (P values were 0.028 and 0.016 respectively),but in the 2.0 Gy group,did not (P=0.471). CONCLUSIONS:CNE-2 cell growth and proliferation are inhibited after 4.0 or 6.0 Gy of 60Co gamma ray fractionated radiation,but are not after 2.0 Gy radiation. The expression levels of Cyclin D1 and PCNA are suppressed after the irradiation.