Update publication information. Although the inhibitor of apoptosis protein-like protein-2 (ILP-2) is regarded as a novel growth enhancer for breast cancer, its mechanism on breast cancer cell growth remains elusive and requires further study. In this study, isobaric tags were applied for relative and absolute quantification (iTRAQ) analysis on two groups of MCF-7 (Michigan Cancer Foundation-7) breast cancer cells, namely, siRNA-5 group (knocked down, KD group) and negative control (NC) group, to analyse the protein expression profiles correlated to ILP-2 during breast cancer cell growth. Western blot was applied to verify the iTRAQ data. The results indicated that a total of 4065 proteins were identified in breast cancer cells, and 241 of these proteins are differentially expressed (fold change ≥ 1.20 or ≤ 0.83 and P<0.05). A total of 156 up- and 85 down-regulated proteins are found in siRNA-5 group versus NC group. These differentially expressed proteins are principally correlated to the ECM (extracellular matrix) -receptor interaction, and the proteins from the top 10 biological processes are correlated to signal transduction, regulation of cell proliferation and immune system processes. The expression of AGA (N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase), MT1E (metallothionein-1E) and TDO2 (tryptophan 2,3-dioxygenase) increases when the protein expression of ILP-2 is knocked down. These results suggested that ILP-2 has an important role in breast cancer cell growth via protein interaction and provided comprehensive insights into biochemical pathways and regulation networks correlated to ILP-2.