afimoxifene and perifosine

Endocrine resistance in breast cancer remains a major clinical problem and is caused by crosstalk mechanisms of growth factor receptor cascades, such as the erbB and PI3K/AKT pathways. The possibilities a single breast cancer cell has to achieve resistance are manifold. We developed a model of 4-hydroxy-tamoxifen (OHT)‑resistant human breast cancer cell lines and compared their different expression patterns, activation of growth factor receptor pathways and compared cells by genomic hybridization (CGH). We also tested a panel of selective inhibitors of the erbB and AKT/mTOR pathways to overcome OHT resistance. OHT‑resistant MCF-7-TR and T47D-TR cells showed increased expression of HER2 and activation of AKT. T47D-TR cells showed EGFR expression and activated MAPK (ERK-1/2), whereas in resistant MCF-7-TR cells activated AKT was due to loss of CTMP expression. CGH analyses revealed remarkable aberrations in resistant sublines, which were predominantly depletions. Gefitinib inhibited erbB signalling and restored OHT sensitivity in T47D-TR cells. The AKT inhibitor perifosine restored OHT sensitivity in MCF-7-TR cells. All cell lines showed expression of receptors for gonadotropin-releasing hormone (GnRH) I and II, and analogs of GnRH-I/II restored OHT sensitivity in both resistant cell lines by inhibition of erbB and AKT signalling. In conclusion, mechanisms to escape endocrine treatment in breast cancer share similarities in expression profiling but are based on substantially different genetic aberrations. Evaluation of activated mediators of growth factor receptor cascades is helpful to predict response to specific inhibitors. Expression of GnRH-I/II receptors provides multi-targeting treatment strategies.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Class I Phosphatidylinositol 3-Kinases; Comparative Genomic Hybridization; Drug Resistance, Neoplasm; Enzyme Activation; ErbB Receptors; Female; Gefitinib; Gene Expression Regulation, Neoplastic; Gonadotropin-Releasing Hormone; Humans; MCF-7 Cells; Phosphatidylinositol 3-Kinases; Phosphorylcholine; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Quinazolines; Receptors, LHRH; Signal Transduction; Tamoxifen; TOR Serine-Threonine Kinases

In patients with advanced estrogen-dependent type I endometrial cancer (EC), pharmacological treatment with progestins or antiestrogens is recommended, but primary and secondary resistance are common. The aim of our study was to investigate single-agent and dual-agent therapeutic strategies in estrogen receptor-positive human EC cells.. Human EC cells Ishikawa and HEC1A were cultivated under estrogen-reduced conditions and exposed to 4-hydroxytamoxifen (OHT), fulvestrant, gefitinib, everolimus, and the AKT inhibitor perifosine. Effects of drugs were analyzed by proliferation and apoptosis assays. Additionally, we analyzed expression of aromatase, phosphatase and tensin homolog (PTEN), AKT and pAKT and G protein-coupled receptor 30 (GPR30).. Neither OHT nor fulvestrant inhibited cell growth, nor did they induce apoptosis. Gefitinib, everolimus and perifosine inhibited proliferation in all cell lines. Only perifosine induced apoptosis. In PTEN-positive HEC1A cells, combined treatment of gefitinib plus OHT showed increased antiproliferative effects. In Ishikawa cells, combined treatment of everolimus plus gefitinib had synergistic antiproliferative effects. The most effective single-agent treatment and the only drug that induced apoptosis was perifosine. Activation of AKT had no predictive value for the effects perifosine. Due to mutation of PTEN, activated AKT was highly expressed in Ishikawa cells and scarcely detectable in HEC1A cells.. Under estrogen-reduced conditions, growth of ER-positive EC cells can be reduced by inhibitors of AKT, mTOR and the erbB pathway, whereas antiestrogens have no effects. In PTEN-positive HEC1A cells, the absence of estradiol probably restores OHT-induced ER-mediated repression of nuclear co-activators and increases susceptibility to inhibitors of the erbB pathway. In PTEN-negative Ishikawa cells, OHT in combination with any drug had no effects, but inhibition of the PI3K/AKT/mTOR pathway by everolimus in combination with gefitinib showed synergistic effects.

Topics: Apoptosis; Aromatase; Cell Line, Tumor; Cell Proliferation; Endometrial Neoplasms; Estrogen Antagonists; Female; Humans; Phosphorylcholine; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Receptors, Estrogen; Receptors, G-Protein-Coupled; Receptors, Growth Factor; Signal Transduction; Tamoxifen