Targeting p70S6K prevented lung metastasis in a breast cancer xenograft model

Ugur Akar, Bulent Ozpolat, Kapil Mehta, Gabriel Lopez-Berestein, Dongwei Zhang, Naoto T. Ueno, Gabriel N. Hortobagyi, Banu Arun

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Overexpression of p70S6K in breast cancer patients is associated with aggressive disease and poor prognosis. Recent studies showed that patients with breast cancer with increased p70S6K phosphorylation had poor survival and increased metastasis. The purpose of our study was to determine whether knockdown of p70S6K would inhibit cell growth, invasion, and metastasis in breast cancer. We therefore stably knocked down p70S6K expression in MDA-231, a highly metastatic breast cancer cell line, using a lentiviral short hairpin RNA (shRNA) based approach. Inhibition of p70S6K led to inhibition of cell growth, migration, and invasion in vitro. To determine the role of p70S6K in breast cancer tumorigenesis and metastasis, we used an MDA-231 orthotopic and metastatic animal model. In the orthotopic model, mice injected with MDA-231-p70S6K shRNA cells developed significantly smaller tumors than control mice injected with MDA-231 control shRNA cells (P < 0.01). No metastasis was observed in the p70S6K downregulated group, whereas lung metastasis was detected in all mice in the control group. To determine the role of p70S6K on growth and invasion, we tested downstream signaling targets by Western blot analysis. Knockdown of p70S6K inhibited phosphorylation of focal adhesion kinase, tissue transglutaminase 2, and cyclin D1 proteins, which promote cell growth, survival, and invasion. In addition, downregulation of p70S6K induced expression of PDCD4, a tumor-suppressor protein. In conclusion, we showed that p70S6K plays an important role in metastasis by regulating key proteins like cyclin D1, PDCD4, focal adhesion kinase, E-cadherin, β-catenin, and tissue transglutaminase 2, which are essential for cell attachment, survival, invasion, and metastasis in breast cancer.

Original languageEnglish (US)
Pages (from-to)1180-1187
Number of pages8
JournalMolecular Cancer Therapeutics
Issue number5
StatePublished - May 2010

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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