Ovarian cancer is among the most lethal cancers in women. The successful anticancer treatment depends on the effectiveness of cytotoxic effect of applied therapeutic procedures either alone or in combination with other treatments. Photodynamic therapy (PDT) is a relatively new method of anticancer therapy. Its dominant mechanism of action is the over-production of reactive oxygen species induced by oxidative stress in malignant cells, which attack lipid membranes, proteins and nucleic acids. One of the important mechanisms is induction of unfolded protein response, ubiquitin-proteasome pathway of protein degradation. The aim of this study was to evaluate the cytotoxic effect of various protective enzymes in ovarian carcinoma clear cell line in comparison to the model breast cell line after photodynamic reaction and photodynamic reaction with 2-methoxyestradiol (2-Me). Human malignant ovarian cell line (OvBH-1) was used and human breast adenocarcinoma cells (MCF-7) were used as a control. Photodynamic reaction (PDR) with Photofrin^®II and Ph^®II with 2-Me was performed. The expression of protective proteins by immunocytochemistry (HSP70 and iNOS) and western blot (Hsp27 and Hsp70) methods was evaluated directly, 3 and 6h after PDR. The changes in cells’ cytoskeleton were evaluated using immunofluorescence by confocal microscopy. The expression of iNOS was observed for both experiments with differential intensity and quantity. A higher expression of Hsp70 in MCF-7 cells was observed than in OvBh-1 cells. The reorganization of cytoskeleton and nucleus was observed after 3 and 6h after exposition to light.