Antisense oligodeoxynucleotides directed against XIAP and Survivin, and Smac mimetics targeting IAPs, are in phase I and phase I II clinical trials. In breast cancer, most of the work on IAPs has focused on Survivin. There are only a few reports examining the other IAPs, and this is in a few cell lines. Studies have shown that inhibiting IAPs augments the apoptotic effect of chemotherapeutics. KOS 953 Few studies, however, have examined whether targeting IAPs can improve the efficacy of newer targeted therapies against oncogenic growth factor receptors in breast cancer. In the present study we examine IAP expression in 14 com monly used breast cancer cell lines compared with a nonma lignant control line.

We show that inhibiting IAPs either using siRNA directed against XIAP or using a Smac mimetic over comes the intrinsic resistance of some of the breast cancer cell lines to both TRAIL and targeted therapies against ErbB Inhibitors,Modulators,Libraries receptors. Inhibiting IAPs may be clinically relevant since the IAP expression profile is altered in tumour biopsy samples. Materials and methods Antibodies The following primary antibodies were used, cIAP2 and Desmoplakin, monoclonal XIAP and calnexin, Ki67 FITC, phospho Erk and oestrogen receptor alpha, Cytokeratin 8 18, Sur vivin, cleaved caspase 3, Erk, mouse monoclonal epi dermal growth factor receptor and rabbit polyclo nal EGFR, and Her2. Anti cIAP1 was a generous gift from J Silke. Cell culture HS578T cells, MDAMB468 cells, CAL51B cells, MDAMB231 cells, SKBR3 cells, MCF7 cells, Zr 75 1 cells, BT474 cells, BT20 cells and T47D cells were all grown in DMEM supplemented with 10% FCS, 2 mM glutamine, peni cillin streptomycin.

PMC42 cells were grown in RPMI with 10% FCS, 2 mM glutamine, penicillin streptomycin. The receptor status of the cell lines was confirmed by western blot ting. The MCF10 progression panel cells were grown in DMEM F12 media supplemented with 5% horse serum, 2 mM glutamine, penicillin streptomycin, Inhibitors,Modulators,Libraries with additional 5g ml hydrocortisone, 10g ml insulin, and 20 ng ml epidermal growth factor for the MCF10a cells, MCF10neoT cells, and MCF10AT1 cells. Tumour samples Approval to remove Inhibitors,Modulators,Libraries normal and tumorigenic human breast tis sues during reduction mammoplasty and from pathologic sam ples, respectively, was obtained Inhibitors,Modulators,Libraries from the Manchester Local Research Ethics Committees. Written informed consent was obtained from the patients before surgery.

The receptor status of the tumour samples Inhibitors,Modulators,Libraries was determined clinically. Frozen sections were diced with a clean razor blade before lysis in RIPA buffer and protein expression was analysed by immunoblotting. Cell lysis and immunoblotting Cells were routinely lysed at 80% confluency in RIPA buffer. Proteins were separated by SDS PAGE and transferred to nitrocellulose membranes, and were subsequently detected Oligomycin A msds using the relevant primary antibody and appropriate secondary antibody.