Critical focus on mechanisms of resistance and toxicity of m-TOR inhibitors in pancreatic neuroendocrine tumors.

Pancreatic neuroendocrine tumors (pNETs) are rare neoplasms representing less than 2% of all pancreatic malignancies. The PI3K-AKT-mTOR pathway is often deregulated in pNETs and seems to play a key role in tumorigenesis. Everolimus, an inhibitor of the mTOR pathway, has demonstrated efficacy in the treatment of pNETs. Nevertheless de novo or acquired drug resistance is responsible for disease progression and represents a major obstacle to overcome by clinicians. Blocking the PI3K/AKT/mTOR pathway may cover the supposed main mechanisms of resistance to everolimus. Therefore, BEZ-235, a potent oral dual PI3K/mTOR inhibitor was investigated in clinical trials. Globally more than 250 patients with different types of solid tumors were treated. Two studies were conducted in pNETs with BEZ-235 as single agent. The former was a phase 2 trial conducted in pNETs resistant to everolimus while the latter a randomized trial comparing everolimus and BEZ-235. Unfortunately, both the studies disappointed the expectations and were prematurely halted mainly due to severe toxicity. On this basis we reviewed m-TOR inhibitors in pNETs, focusing on their mechanisms of resistance and toxicity.

Circulating endothelial progenitor cells in postmenopausal women with and without coronary artery disease.

BACKGROUND: Middle-aged women have a lower prevalence of coronary artery disease (CAD) compared with age-matched men, but mechanisms underlying this phenomenon remain controversial. To verify whether there is a link between circulating endothelial progenitor cells (EPCs) and gender-specific difference of CAD, we compared subpopulations of EPCs among postmenopausal normal women, patients with CAD, and age-matched men. METHODS: We studied 71 consecutive middle-aged patients with stable CAD (30 postmenopausal women and 41 men) and 40 middle-aged normal controls (20 postmenopausal women and 20 men). Blood samples were drawn at time of coronary angiography and subpopulations of EPCs were measured by flow cytometry. RESULTS: Women and men with CAD had similar age, risk factors, clinical presentation, left ventricular function, extension of CAD, and medical therapy at time of coronary angiography. Hematologic analysis showed that men and women with CAD had similar white cell count, mononuclear cells, and subpopulations of EPCs. Postmenopausal normal women, conversely, had significantly higher absolute numbers of CD34+, CD133+, CD105+ and CD14+ cells than other groups. CONCLUSIONS: Increased numbers of subpopulations of EPCs in normal postmenopausal women might contribute to the gender-specific difference of CAD in middle age. Lack of difference in EPCs between women and men with CAD suggests that stem cells become unable to play a protective role when the disease is clinically evident.