Jang et al. BMC Cancer 2010, 10:391 http://www.biomedcentral.com/1471-2407/10/391 present study revealed that ANT2 shRNA treatment led to simultaneous down-regulation of HER2 protein and phospho-Akt levels, which preceded the degradation of Akt protein. Therefore, we speculate that PI3K/Akt sig- naling could be efficiently inhibited by ANT2 shRNA in a HER2-overexpressing breast cancer through HER2 degradation in advance of Akt degradation. Tumor cell invasion is dependent on finely regulated extracellular proteolytic activity, which allows penetra- tion of tumor cells through ECM. Activated phospho- Akt enhanced expression of MT1-MMP and MMP2 is associated with cancer invasion and metastasis, as well as angiogenesis [41]. This study provides evidence that inactivation of PI3K/Akt signaling pathway by ANT2 shRNA down-regulates MT1-MMP, MMP2, and MMP9 expression and activity as well as VEGF expression in a HER2/neu-overexpressing breast cancer cell line. Conclusions In conclusion, the results of this study provide mechan- istic evidence that ANT2 shRNA suppresses induced migration and invasion by depletion of HER2/neu pro- tein and, in turn, suppression of HER2/PI3K/Akt path- way signaling and subsequent suppression of proteolytic activity by down-regulating MMPs. We propose that gene therapy using ANT2 shRNA may be a potentially effective therapeutic tool against HER2/neu-overexpres- sing breast cancers. List of abbreviations ANT: adenine nucleotide translocase; shRNA: short-hairpin RNA; siRNA: small interfering RNA; BSA: bovine serum albumin; DMEM: Dulbecco’s modified Eagle’s medium; FBS: fetal bovine serum; PBS: phosphate-buffered saline; RT: reverse transcription; PCR: polymerase chain reaction; PI3K: phosphoinositide- 3 kinase; HSP90: Heat shock protein 90; MT1-MMP: membrane-type 1 matrix metalloproteinase; VEGF: vascular endothelial growth factor; MMP2: matrix metalloproteinase 2; 17-AAG: 17-allylamino-17-demethoxygeldanamycin; ECM: extracellular matrix; VEGF: vascular endothelial growth factor. Acknowledgements This work was supported in part by grants from the Korean Cancer Research Center and the Korean Science & Engineering Foundation through the Tumor Immunity Medical Research Center at Seoul National University College of Medicine. Authors’ contributions J-YJ performed most of the experiments and was responsible for producing the results, and for data analysis. Y-KJ was responsible for data analysis and for writing the paper. C-WK contributed to the design of the project, to data analysis, and to writing of the paper. All authors reviewed and agreed on the final manuscript. Competing interests The authors have applied for a domestic patent and will apply for an international patent for utilization of ANT2 siRNA technology as a therapeutic method for use in cancer treatment. Seoul National University College of Medicine will retain the patent. The authors declare that they have no other competing interests. Received: 10 May 2010 Accepted: 23 July 2010 Published: 23 July 2010 Page 8 of 9 References 1. Greenle RT, Hill-Harmon MB, Thun M: Errata. CA Cancer J Clin 2001, 51:15-36. 2. Slamon D, Clark M, Wong S, Levin W, Ullrich A, McAuire W: Detection of c-erbB-2 amplification in breast cancer by in situ hybridization. Science 1987, 235:177-181. 3. Menard S, Tagliabue E, Campiglio M, Pupa SM: Role of HER2 gene overexpression in breast carcinoma. J Cell Physiol 2000, 182:150-162. 4. Fernández Val JF, Losada J, Arregui Murua MA, Sarría R: Cell proliferation, nuclear ploidy, and EGFR and HER2/neu tyrosine kinase oncoproteins in infiltrating ductal breast carcinoma. Cancer Genetics and Cytogenetics 2002, 138:69-72. 5. Prenzel N, Fischer OM, Streit S, Hart S, Ullrich A: The epidermal growth factor receptor family as a central element for cellular signal transduction and diversification. Endocr Relat Cancer 2001, 8:11-31. 6. Cobleigh MA, Vogel CL, Tripathy D, Robert NJ, Scholl S, Fahrenbacher L, Wolter JM, Paton V, Shak S, Lieberman G, et al: Multinational study of the efficacy and safety of humanized anti-Her2 monoclonal antibody in women who have Her2-overexpressing metastatic breast cancer that has progressed after chemotherapy for metastatic disease. J Clin Oncol 1999, 17:2639-2648. 7. Slamon DJ, Leyland-Jones B, Shak S, Fuchs H, Paton V, Bajamonde A, Fleming T, Eiermann W, Wolter J, Pegram M, et al: Use of chemotherapy plus a monoclonal antibody against HER2 for metastatic breast cancer that overexpresses HER2. N Engl J Med 2001, 344:783-792. 8. Pegram MD, Lipton A, Hayes DF, Weber BL, Baselga JM, Tripathy D, Baly D, Baughman SA, Twaddell T, Glaspy JA, et al: Phase II study of receptor- enhanced chemosensitivity using recombinant humanized anti- p185HER2/neu monoclonal antibody plus cisplatin in patients with HER2/neu-overexpressing metastatic breast cancer refractory to chemotherapy treatment. J Clin Oncol 1998, 16:2659-2671. 9. Baselga J, Tripathy D, Mendelsohn J, Baughman S, Benz CC, Dantis L, Sklarin NT, Seidman AD, Hudis CA, Moore J, et al: Phase II study of weekly intravenous recombinant humanized anti-p185HER2 monoclonal antibody in patients with HER2/neu-overexpressing metastatic breast cancer. J Clin Oncol 1996, 14:737-744. 10. Romond EH, Perez EA, Bryant J, Suman VJ, Geyer CE Jr, Davidson NE, Tan- Chiu E, Martino S, Paik S, Kaufman PA, et al: Trastuzumab plus chemotherapy for operable HER2-positive breast cancer. N Engl J Med 2005, 353:1673-1684. 11. Piccart-Gebhart MJ, Proctor M, Leyland-Jones B, Goldhirsch A, Untch M, Smith I, Gianni L, Baselga J, Bell R, Jackisch C, et al: Trastuzumab after adjuvant chemotherapy in HER2-positive breast cancer. N Engl J Med 2005, 353:1659-1672. 12. Clynes RA, Towers TL, Presta LG, Ravetch JV: Inhibitory Fc receptors modulates in vivo cytotoxicity against tumor targets. Nat Med 2000, 6:443-446. 13. Sreedhar AS, Kalmar E, Csermely P, Shen YF: Hsp90 isoforms: functions, expression and clinical importance. FEBS Lett 2004, 562:11-15. 14. Meares GP, Zmijewska AA, Jope RS: Heat shock protein-90 dampens and directs signaling stimulated by insulin-like growth factor-1 and insulin. FEBS Lett 2004, 574:181-186. 15. Citri A, Kochupurakkal BS, Yarden Y: The achilles heel of ErbB-2/HER2: Regulation by the Hsp90 chaperone machine and potential for pharmacological intervention. Cell Cycle 2004, 3:51-60. 16. Wolfgang HS, Obermann MJ, Russo AA, Pavletich NP, Hartl FU: In vivo function of Hsp90 is dependent on ATP binding and ATP hydrolysis. J Cell Biol 1998, 143:901-910. 17. Stirling PC, Bakhoum SF, Feigl AB, Leroux MR: Convergent evolution of clamp-like binding sites inn diverse chaperones. Nat Struct Mol Biol 2006, 13:865-870. 18. Fiore C, Tezeguet V, LeSaux A, Roux P, Schwimmer C, Dianoux AC, Noel F, Lauquin GJM, Brandolin G, Vignais PV: The mitochondrial ADP/ATP carrier: structural, physiological and pathological aspects. Biochimie 1998, 80:137-150. 19. Jang JY, Choi Y, Jeon YK, Kim CW: Suppression of adenine nucleotide translocase-2 by vector-based siRNA in human breast cancer cells induces apoptosis and inhibits tumor growth in vitro and in vivo. Breast Cancer Research 2008, 10:R11. 20. Rao J: Molecular mechanisms of glioma invasiveness: the role of proteases. Nat Rev Cancer 2003, 3:489-501.