In vitro evaluation of pan-PI3-kinase inhibitor SF1126 in trastuzumab-sensitive and trastuzumab-resistant HER2-over-expressing breast cancer cells

Tuba Ozbay, Donald L. Durden, Tongrui Liu, Ruth M. O'Regan, Rita Nahta

Research output: Contribution to journalArticle

34 Scopus citations


Purpose: The purpose of the current study is to determine the in vitro cytotoxic effects of the novel pan-PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells. Methods: Cell proliferation and cytotoxicity were examined by MTS colorimetric assay, FACS analysis, colony formation assay, and immunoblotting. Phosphoinositol-3-kinase signaling was assessed by immunoblotting for phosphorylated Akt. Combination effects of trastuzumab and SF1126 were examined in resistant cells by MTS and soft agar assay. Results: SF1126 inhibited proliferation, and induced G1 arrest and apoptosis of SKBR3 and BT474 parental and trastuzumab-resistant HER2-over-expressing cells. Colony formation was inhibited by SF1126, caspase 3 and PARP proteins were cleaved, and survivin was down-regulated. Inhibition of PI3-kinase was confirmed by reduced phosphorylation of Akt. Finally, the combination of SF1126 and trastuzumab synergistically inhibited proliferation of resistant cells, with SF1126-treated cells showing reduced anchorage- independent growth. Conclusions: These results provide evidence that a clinically relevant pan-PI-3 kinase inhibitor can reverse trastuzumab resistance in breast cancer cells, and support further study of PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells, including those that have progressed on trastuzumab.

Original languageEnglish (US)
Pages (from-to)697-706
Number of pages10
JournalCancer Chemotherapy and Pharmacology
Issue number4
Publication statusPublished - Mar 1 2010



  • Drug resistance
  • Herceptin
  • PI3-kinase
  • Targeted therapy

ASJC Scopus subject areas

  • Oncology
  • Toxicology
  • Pharmacology
  • Cancer Research
  • Pharmacology (medical)

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