BMC Cancer 2009, 9:398 http://www.biomedcentral.com/1471-2407/9/398 cFDaeiNtgllesuAdrceaduoa1smseeadsgbedyeint2e-nchtoenadn-sdbtyi2m4Cu-olhamteeetdotpaAonsdssiadPyeHatAtre-psaHttim>eun1lat3teatdtbhleo oinddi- DNA damage in non-stimulated and PHA-stimulated blood cells caused by 2-h and 24-h etoposide treat- ment at the indicated doses detected by Comet Assay at pH > 13. A) 2-h treatment; B) 24-h treatment. Each bar represents the mean value of three independent experiments. Data were analyzed using the Mann-Whitney U test. (*= p < 0.05, ** = p < 0.01, *** = p < 0.001 vs. control). age induction by etoposide in non-cycling cells. This dis- crepancy is most likely due to inherent differences between the cells used in the experiments. Olive and Banath used colon carcinoma cells (WiDr), while we used human lymphocytes from healthy donors. Lymphocytes, such as those used here, are normally arrested in the G0 phase and non-transformed. To asses the molecular processes involved in the etopo- side treatment-induced breaks, we compared the non- stimulated whole blood cells genotoxicity data generated cFDeaiNtgllesuAdrceaduoa2smseeadsgbedyeint2e-nchotenadn-sdbtiy2m4Cu-olhamteetedotpaAonsdssiadPyeHatAtre-psaHttim=eun1lat2t.ea3tdtbhleo oinddi- DNA damage in non-stimulated and PHA-stimulated blood cells caused by 2-h and 24-h etoposide treat- ment at the indicated doses detected by Comet Assay at pH = 12.3. A) 2-h treatment; B) 24-h treatment. Each bar represents the mean value of three independent experiments. Data were analyzed using the Mann-Whitney U test. (*= p < 0.05, *** = p < 0.001 vs. control). by the SCGE assay under both highly basic (= 12.3) and extremely basic (> 13) pH conditions and thus generated the ALS index values (see results section). This compari- son enables the presence of ALSs to be deduced indirectly because the oxidative response capable of generating apu- rinic or apyrimidic sites (AP sites) is pH-dependent [41,42]. The ALS index data indicated that ALSs, which can be generated by an oxidative stress [6,33], constituted the primary form of DNA damage induced by etoposide in whole blood cells. To asses whether oxidative stress was responsible for the DNA damage observed in the etoposide-treated non-stim- Page 5 of 9 (page number not for citation purposes)