Breast cancer is a cancer type which is seen most commonly among women all around the world (Beiki et al., 2012). It is a heterogeneous disease in terms of different morphologic characteristics and molecular profiles and also, in terms of clinical behavior and the response that they demonstrate to the treatment (Kwan et al., 2009; Boscha et al., 2010). The therapeutic effects of the DNA damage in the cancer treatment have been known for so long and this constitutes the basis of many successful cytotoxic chemotherapy and that of the radiotherapy. Cytotoxic chemotherapy has an important part of cancer treatment, however it imposes some restrictions. Targeting not only cancer cells but also healthy tissues generates many adverse effects that decrease the life quality of patient. Together with, the conventional chemotherapy applied to patients is palliative treatment as much as it is medical. For this purpose, it is aimed to investigate the antiproliferative effects of PARP inhibitors on the MCF-7 cell line derived from the human breast adenocarcinoma and the parameters of cell kinetics such as the analysis of mitochondrial dehydrogenase enzyme activity, mitotic index and apoptotic index were assessed. Also it is aimed to invesitgate the antiproliferative effects of HA14-1, which is an inhibitor of Bcl-2, on the cell lines of MDA-MB-231 as a triple negative breast cancer model, which is more difficult to treat than other types of breast cancer. According to the results, PARP inhibitor applied to MCF-7 cells in 100- micromolar concentration for 0-72 hours causes a decrease in mitotic index and increase in apoptotic index (p<0.05). Also mitotic index and apoptotic index among the cell kinetic parameters were evaluated by means of application of HA14-1 on MDA-MB-231, it has been observed that HA14-1 applied in 25 μg/ml concentration significantly decreases the cell reproduction rate and mitosis, but increases the apoptosis (p<0.05).