epidermal-growth-factor and perifosine

Centrosome amplification, which is a characteristic of cancer cells, has been understood as a driving force of genetic instability in the development of cancer. In previous work, we demonstrated that TEIF (transcriptional element-interacting factor) distributes in the centrosomes and regulates centrosome status under both physiologic and pathologic conditions. Here we identify TEIF as a downstream effector in EGF/PI3K/Akt signaling. The addition of EGF or transfection of active Akt stimulates centrosome TEIF distribution, resulting in an increase of centrosome splitting and amplification, while inhibitors of either PI3K or Akt attenuate these changes in TEIF and the associated centrosome status. A consensus motif for Akt phosphorylation (RHRVLT) proved to be involved in centrosomal TEIF localization, and the 469-threonine of this motif may be phosphorylated by Akt both in vitro and in vivo. Elimination of this phosphorylated site on TEIF caused reduced centrosome distribution and centrosome splitting or amplification. Moreover, TEIF closely co-localized with C-NAP1 at the proximal ends of centrioles, and centriolar loading of TEIF stimulated by EGF/Akt could displace C-NAP1, resulting in centrosome splitting. These findings reveal linkage of the EGF/PI3K/Akt signaling pathway to regulation of centrosome status which may act as an oncogenic pathway and induce genetic instability in carcinogenesis.

Topics: Adaptor Proteins, Vesicular Transport; Amino Acid Sequence; Cell Line; Centrioles; Centrosome; DNA-Binding Proteins; Epidermal Growth Factor; Green Fluorescent Proteins; Humans; Molecular Sequence Data; Nuclear Proteins; Phosphatidylinositol 3-Kinases; Phosphorylation; Phosphorylcholine; Protein Transport; Proto-Oncogene Proteins c-akt; Signal Transduction; Transcription Factors

PTEN is a well-characterized tumor suppressor that negatively regulates cell growth and survival through the modulation of PI3K/Akt pathway.. In this paper, we investigated the effects of an PI3K/Akt inhibitor, perifosine, in human prostate cancer (PCa) cells analyzing cell proliferation, apoptosis, and the synergy with EGFR inhibitors.. Clinically achievable concentrations of perifosine, as well as Akt gene knockdown, induced a G0/G1 arrest and apoptosis in PTEN defective PCa cells. Although PTEN introduction was able to restore the control of Akt activity and to reduce cell proliferation, the manipulation of PTEN gene was not able alone to influence apoptosis. Perifosine induced apoptotic program also in PTEN positive cells when Akt activity was augmented by EGF suggesting the possibility that this drug could be used in combination with EGFR inhibitors. The combination treatment between erlotinib and pharmacological or molecular Akt knockdown, indeed, showed synergistic effects. This is the first demonstration that a pharmacological compound against Akt activity can restore the efficacy against EGFR inhibitors in PCa and has important therapeutic fallout since EGFR inhibitors have demonstrated very low effectiveness in PCa patients.. Taken together our data have an important clinical relevance in the treatment of advanced prostate tumors. However, further studies in the setting of combination therapies in advanced PCas are necessary.

Topics: Apoptosis; Blotting, Western; Caspases; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Chromones; Drug Synergism; Enzyme Activation; Epidermal Growth Factor; Erlotinib Hydrochloride; Flow Cytometry; Humans; Male; Morpholines; Neoplasms, Hormone-Dependent; Phosphorylcholine; Prostatic Neoplasms; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Quinazolines