The Study Of Sister Chromatid Exchange Assay And Micronucleus Assay As Biomarkers For Evaluating Radiotherapy Induced Cytogenetic Damage Of Cervical Carcinoma Patients

Objective:To study the spontaneous frequency of sister chromatid exchange (SCE) and micronucleus (MN) in peripheral blood lymphocytes (PBL) of patients with cervical carcinoma; the variety of SCE frequency and MN frequency during radiotherapy; the applicability of SCE assay and MN assay as cytogenetic markers for evaluating in vivo radiation induced chromosome damage; the variety of MN frequency in bladder mucosa exfoliated cells during radiotherapy and the clinical applicability of MN assay in bladder mucosa exfoliated cells as a useful biomarker for evaluating radiotherapy induced bladder mucosa cell's chromosome damage. Methods:Collected 15 cervical carcinoma patients' peripheral blood before and during radiotherapy, the SCE assay and cytokinesis-blocked MN assay were applied. At the same day 5 of the 15 patients' second urine in the morning were collected and MN assay in bladder mucosa exfoliated cells was applied. Result:1 . Significant difference of spontaneous SCE frequency (7.12 + 2.16) and MN frequency (15.93 5.91%) were observed between the cervical carcinoma patients and healthy population (P<0.001) .2 . After the initiation of radiotherapy, the average SCE frequencysignificantly increased but no correlation was found between the SCE frequency and radiation dose. There was a statistical difference at dose of 20 Gy, 30 Gy and 50 Gy compared to 0 Gy (P<0.05). At the accumulated dose of 20 Gy, the SCE frequency achieved the max value; then the SCE frequency declined, at the accumulated dose of 40 Gy, there was not statistic difference compared to OGy; at the accumulated dose of 50Gy, the SCE frequency increased again.3 . The MN frequency in PBL increased linearly with the radiation dose as YMNF=66.917+3.016Xdose (r=0.976, PO.001); they had a significant correlation.4. After the initiation of radiotherapy, the SCE frequency and MN frequency differed with the radiation dose with different sensitivity. The MN frequency rose significantly at the accumulated dose of 10 Gy, but the SCE frequency did not raise until at the dose of 20 Gy.5. After the initiation of radiotherapy the mean MN frequency in bladder mucosa exfoliated cells increased but no statistical difference was found. Conclusions:1 . The spontaneous frequency of SCE and MN in PBL of patients with cervical carcinoma are significantly higher than that in normal individuals, the instability of chromosome of the cervical carcinoma patients is increased.2 . After the initiation of radiotherapy the average frequency of SCE and MN were significantly increased and a good dose-response relationship was observed between MN frequency and radiation dose.3 . Radiotherapy can induce DNA damage, sister chromatid exchange assay and cytokinesis-blocked micronucleus assay in peripheral blood lymphocytes are effective cytogenetic markers to evaluate the radiation induced chromosome damage, and micronucleus assay is more sensitive.4 . The clinical application of MN assay in bladder mucosa exfoliated cells as a useful biomarker for monitoring radiotherapy induced bladder mucosa cell'schromosome damage is not ideal.