Rapamycin and its analogues inhibit mTOR, which leads to decreased protein synthesis and decreased cancer cell proliferation in many experimental systems. Adenosine 5'- monophosphate-activated protein kinase (AMPK) activators such as metformin have similar actions, in keeping with the TSC2/1 pathway linking activation of AMPK to inhibition of mTOR. As mTOR inhibition by rapamycin is associated with attenuation of negative feedback to IRS-1, rapamycin is known to increase activation of AKT, which may reduce its anti-neoplastic activity. We observed that metformin exposure decreases AKT activation, an action opposite to that of rapamycin. We show that metformin (but not rapamycin) exposure leads to increased phosphorylation of IRS-1 at Ser(789), a site previously reported to inhibit downstream signaling and to be an AMPK substrate phosphorylated under conditions of cellular energy depletion. siRNA methods confirmed that reduction of AMPK levels attenuates both the IRS-1 Ser(789) phosphorylation and the inhibition of AKT activation associated with metformin exposure. Although both rapamycin and metformin inhibit mTOR (the former directly and the latter through AMPK signaling), our results demonstrate previously unrecognized differences between these agents. The data are consistent with the observation that maximal induction of apoptosis and inhibition of proliferation are greater for metformin than rapamycin.

BACKGROUND Although recent laboratory and population studies suggest that prostate cancer may be responsive to insulin, there is a gap in knowledge concerning the expression of insulin receptors on benign or malignant prostate tissue. METHODS We immunostained 644 cores on tissue microarrays prepared from 29 prostate tissue samples without malignancies, 78 Gleason grade 3 cancers, 21 Gleason grade 4 cancers and 33 Gleason grade 5 cancers with antibodies against the insulin‐like growth factor I receptor and the insulin receptor. RESULTS We observed immunoreactivity with both antibodies, which implies the presence of hybrid receptors as well as IGF‐I receptors and insulin receptors. Insulin receptor staining intensity was significantly (P < 0.001) higher on malignant than benign prostate epithelial cells. Analysis of information from public gene expression databases confirmed that co‐expression of insulin receptor mRNA and IGF‐I receptor mRNA is common in prostate cancer specimens. RT‐PCR methods provided evidence for the presence of mRNA for both IR‐A and IR‐B insulin receptor isoforms. CONCLUSION These observations document the presence of insulin receptors on primary human prostate cancers. The findings are relevant not only to ongoing clinical trials of drug candidates that target IGF‐I and/or insulin receptors, but also to the hypothesis that obesity‐associated hyperinsulinemia mediates the adverse effect of obesity on prostate cancer prognosis. Prostate 69: 33–40, 2009. © 2008 Wiley–Liss, Inc.

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This paper will focus on knowledge related to brain metastases from ovarian carcinoma. So far, less than 600 cases were documented in the literature with an incidence among ovarian carcinoma patients ranging from 0.29% to 11.6%. The ovarian carcinoma was usually an advanced-stage epithelial serous carcinoma, and the median interval between diagnosis of ovarian carcinoma and brain metastases was 2 years. Most often, brain metastases, affected the cerebrum, were multiple and part of a disseminated disease. Treatment of brain metastasis has evolved over the years from whole brain radiotherapy (WBRT) only to multimodal therapy including surgical resection or stereotactic radiosurgery followed by WBRT and/or chemotherapy. The median survival after diagnosis of brain metastases was 6 months; nevertheless, a significantly better survival was achieved with multimodal therapy compared to WBRT only. It is suggested that brain imaging studies should be included in the followup of patients after treatment for ovarian carcinoma.