Backgrounds Although 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. This study analysed the expression profiles of proteins with association to ILP-2 protein during Michigan Cancer Foundation-7 (MCF-7) breast cell growth for its mechanism on breast cancer cell growth.Methods Isobaric tags for relative and absolute quantification analysis (iTRAQ) was applied on siRNA-5 and negative control groups of MCF-7 breast cancer cells to analyse protein expression profile correlated to ILP-2 during MCF-7 cell growth. Verification of iTRAQ data was by done by Western blot.Results4065 proteins were identified in the MCF-7 cells, with 241 of differentially expressed proteins (DEPs) (fold change ≥ 1.20 or ≤ 0.83 and P<0.05). A total of 156 upregulated and 85 downregulated proteins were found in the siRNA-5 group versus negative control group. These DEPs were associated with the extracellular matrix receptor interaction. Proteins from the top 10 biological processes were associated with 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) increased when the protein expression of ILP-2 was knocked-down. ConclusionsThese results suggest that ILP-2 promotes MCF-7 cell growth by regulating cell proliferation, signal transduction, and immune system processes.

Inhibitor of apoptosis protein-related-like protein-2 (ILP-2), also known as BIRC-8, is a member of the inhibitor of apoptosis protein (IAPs) family, which mainly encodes the negative regulator of apoptosis. It is selectively overexpressed in a variety of human tumors and can help tumor cells evade apoptosis, promote tumor cell growth, increase tumor cell aggressiveness, and appears to be involved in tumor cell resistance to chemotherapeutic drugs. Several studies have shown that downregulation of ILP-2 expression increases apoptosis, inhibits metastasis, reduces cell growth potential, and sensitizes tumor cells to chemotherapeutic drugs. In addition, ILP-2 inhibits apoptosis in a unique manner; it does not directly inhibit the activity of caspases but induces apoptosis by cooperating with other apoptosis-related proteins. Here, we review the current understanding of the various roles of ILP-2 in the apoptotic cascade and explore the use of interfering ILP-2, and the combination of related anti-tumor agents, as a novel strategy for cancer therapy.

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