Abstract
OBJECTIVE: Breast cancer represents the most prevalent type of tumor throughout the world. Considering the side effects caused by the available treatments, the resistance acquired by cells to cytotoxic agents, and metastasis, it is necessary to search for new sources of antitumor and antimetastatic therapies. Given the numerous antitumor studies involving the synthesis of substances derived from the naphthoquinone lapachol, we investigated the antineoplastic potential of a new synthetic substance (APO-3) derived from lapachol, alone and in combination with the chemotherapeutic agent paclitaxel (PTX), against 4T1 cells, a murine breast cancer cell line. METHODS/RESULTS: In MTT assay APO-3 and the APO-3/PTX combination were selectively cytotoxic to 4T1 cells, with APO-3/PTX being approximately 6.5 and 15 times more selective than PTX and APO-3, respectively. After zymography, APO-3/PTX was more effective in decreasing matrix metalloproteinase-9 (MMP-9) activity compared with APO-3 alone. In the clonogenic assay, APO-3/PTX reduced the number of colonies more effectively than APO-3 or PTX alone. APO-3/PTX also inhibited cell migration, as did PTX and APO-3 alone. The combination increased the expression of proteins involved in the intrinsic apoptotic pathway and induced cellular morphological changes characteristic of this type of cell death, acting similarly to PTX alone. APO-3 increased Receptor-interacting serine/threonine-protein kinase 1 (RIP1) and caused morphological changes characteristic of apoptosis and necroptosis in 4T1 cells. CONCLUSION: Taken together, APO-3 presented antitumor action against 4T1 cells, but the APO-3/PTX combination was more effective than either substance alone.