['The outcome of chemotherapy in breast cancer is strongly influenced by multidrug resistance (MDR). Several surrogate markers of chemoresistance have been identified including - CD24 (cluster differentiation 24) expression, stem cell growth factor (SCF), B-cell lymphocyte protein 2 (Bcl-2) and annexin V. The present study aimed to examine the expression of CD24 in the sensitive breast cancer cell line MCF-7 (Michigan Foudation-7) and MCF-7/adriamycin resistant (MCF-7/AdrRes) cells, and, if minimal effective doses of the anthracycline drug adriamycin (0.579\u2009μM and 88.2\u2009μM) would be enhanced by the antibody to SCF (anti-SCF).', 'CD24 expression was analysed by flow cytometry. Both Bcl-2 and annexin V protein expression were quantitatively assessed by the enzyme-linked immunosorbent assay (ELISA).', 'In MCF-7/AdrRes cells the expression of CD24 was significantly higher compared to MCF-7 cells, 86.6% and 16.3% (p\u2009<\u20090.001), respectively. Bcl-2 expression was significantly increased in the presence of adriamycin and SCF (p\u2009<\u20090.038) and decreased in the presence of adriamycin and anti-SCF. When adriamycin, anti-SCF and SCF were combined or when adriamycin was used alone the decrease in Bcl-2 expression was insignificantly altered. In the presence of both adriamycin and SCF the expression of annexin V was decreased. However, it was significantly increased in the presence of adriamycin and anti-SCF (p\u2009<\u20090.042), as well as adriamycin, anti-SCF and SCF combined.In MCF-7 cells the effect of adriamycin alone or with either SCF, anti-SCF or anti-SCF or SCF combined, did not significantly alter the expression of Bcl-2. However, in the presence of both adriamycin and SCF the expression of annexin V was decreased, but was significantly increased in the presence of adriamycin and anti-SCF (p\u2009<\u20090.001), adriamycin, anti-SCF and SCF combined and adriamycin alone. Our results demonstrate that anti-SCF with low dose of adriamycin reduces Bcl-2 expression in MCF-7/AdrRes cells and increases annexin V expression in both MCF7/AdrRes and MCF-7 cells.'] Does the stem cell factor antibody enhance the chemotherapeutic effect of adriamycin on chemoresistant breast cancer cells?