DNA Strand Breaks In Peripheral Lymphocytes from Breast Cancer Patients before and after Chemotherapy.
aOncological Research Unit, bDepartment of Clinical Oncology, National Medical Center S-XXI- IMSS; Oncology Hospital, C.P. México, D.F, cNational Autonomus University of Mexico, México, D.F. email: luisbenbri@mexis.com
AIM: To asses the degree and type of DNA damage in peripheral lymphocytes (PL) from breast cancer patients before and after combined chemotherapy with a method that distinguishes single and doble-strand breaks. METHODS: Peripheral lymphocytes from thirty four patients with ductal carcinoma of the breast, clinical stage III were isolated from venous blood drawn before treatment and at the end of combined chemotherapy (Epirubicin, 5-fluorouracil and cyclophosphamide; four cycles every 21 days), and from 40 age-matched normal subjects. Lymphocytes were processed with a modified dried comet assay method at alkaline and neutral pH for identification of single-strand (ssb) and double-strand breaks (dsd) respectively. DNA from PL was subjected to agarose gel electrophoresis to detect laddering and cytological smears were stained with Giemsa for morphological identification of apoptosis. RESULTS: Cancer patients had significantly higher DNA damage before treatment. Comet tail moments for controls were: ssb 6.33 ± 1.74 and dsb 2.31 ± 1.09; for cases ssb 9.09 ± 1.3 and dsb 6.15 ± 1.9 (p < 0.001) respectively. After treatment tail moments increased significantly for ssb 10.6 ± 1.61 (p < 0.01) and for dsb 7.16 ± 1.4 (p <0.01). The percentage of cell comets had also a significant variation between cases and controls at baseline. However after treatment the number of cells with ssb showed a marked increase from 20.08 to 71.76 per cent. CONCLUSIONS: Peripheral lymphocytes from cancer patients contain a greater amount of double and single DNA strand breaks before treatment. After chemotherapy both types of strand breaks increase significantly but no signs of apoptosis could be detected.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 895 (Chemotherapy response).