The present study successfully identified cancer-related proteins that undergo significant changes upon B. jararaca venom treatment of MCF7 and MDA-MB-231 cells, including SNX3, HEL-S-156an, UQCRC1, RPL36, and ATR identified in MCF7 cell line and H3C15/HIST2H3, HEL-S-132P, MTCH2, TFAM, KCTD12, RPL34, and RPL37A identified in MDA-MB-231 cell line, and histone H3F3B and LAP3 in both cell lines. This evidence concerns the gene ATR and cancer.