Targeting the PI3K/AKT/mTOR pathway in biliary tract cancers: A review of current evidences and future perspectives

Biliary tract cancers (BTCs) are a group of invasive neoplasms, with increasing incidence and dismal prognosis. In advanced disease, the standard of care is represented by first-line chemotherapy with cisplatin and gemcitabine. In subsequent lines, no clear recommendations are currently available, highlighting the need for novel therapeutic approaches.The PI3K/AKT/mTOR pathway is a core regulator of cell metabolism, growth and survival, and is involved in BTCs carcinogenesis and progression. Mutations, gene copy number alterations and aberrant protein phosphorylation of PI3K, AKT, mTOR and PTEN have been thoroughly described in BTCs and correlate with poor survival outcomes.Several pre-clinical evidences state the efficacy of PI3K/AKT/mTOR pathway inhibitors in BTCs, both in vitro and in vivo. In the clinical setting, initial studies with rapamycin analogs have shown interesting activity with an acceptable toxicity profile. Novel strategies evaluating AKT and PI3K inhibitors have risen serious safety concerns, pointing out the need for improved patient selection and increased target specificity for the clinical development of these agents, both alone and in combination with chemotherapy.This review extensively describes the role of the PI3K/AKT/mTOR pathway in BTCs and examines the rationale of its targeting in these tumors, with particular focus on clinical activity, toxicities and perspectives on further development of PI3K/AKT/mTOR pathway inhibitors.     

生酮饮食的抗癫(痫)机制研究进展

生酮饮食用于癫(痫)治疗已达90年之久,引进我国也已10余年.生酮饮食临床疗效已得到一致认可,但其抗癫(痫)机制至今仍不明确.该文从离子通道、神经递质、神经保护、腺苷及mTOR通路、免疫因素的角度来阐述其可能的抗癫(痫)机制.     

Effects of ketamine administration on mTOR and reticulum stress signaling pathways in the brain after the infusion of rapamycin into prefrontal cortex

Recent studies show that activation of the mTOR signaling pathway is required for the rapid antidepressant actions of glutamate N-methyl-D-aspartate (NMDA) receptor antagonists. A relationship between mTOR kinase and the endoplasmic reticulum (ER) stress pathway, also known as the unfolded protein response (UPR) has been shown. We evaluate the effects of ketamine administration on the mTOR signaling pathway and proteins of UPR in the prefrontal cortex (PFC), hippocampus, amygdala and nucleus accumbens, after the inhibiton of mTOR signaling in the PFC. Male adult Wistar rats received pharmacological mTOR inhibitor, rapamycin (0.2 nmol), or vehicle into the PFC and then a single dose of ketamine (15 mg/kg, i.p.). The immunocontent of mTOR, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), eukaryotic elongation factor 2 kinase (eEF2K) homologous protein (CHOP), PKR-like ER kinase (PERK) and inositol-requiring enzyme 1 (IRE1) – alpha were determined in the brain. The mTOR levels were reduced in the rapamycin group treated with saline and ketamine in the PFC; p4EBP1 levels were reduced in the rapamycin group treated with ketamine in the PFC and nucleus accumbens; the levels of peEF2K were increased in the PFC in the vehicle group treated with ketamine and reduced in the rapamycin group treated with ketamine. The PERK and IRE1-alpha levels were decreased in the PFC in the rapamycin group treated with ketamine. Our results suggest that mTOR signaling inhibition by rapamycin could be involved, at least in part, with the mechanism of action of ketamine; and the ketamine antidepressant on ER stress pathway could be also mediated by mTOR signaling pathway in certain brain structures.     

A phase Ib study investigating the combination of everolimus and dovitinib in vascular endothelial growth factor refractory clear cell renal cancer

BackgroundEverolimus (mammalian target of rapmaycin (mTOR) inhibitor) and dovitinib (vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF-2) inhibitor) demonstrate activity in metastatic clear cell renal cancer. The combination of these agents has a broad spectrum of relevant activity. The combination is explored in this phase Ib study.MethodsPatients with metastatic clear cell renal cancer who have failed VEGF targeted therapy were eligible. Up to four cohorts of three to six patients (3+3 design) were treated with escalating doses of everolimus and dovitinib. Dose-limiting toxicities (DLTs) were assessed to determine the maximum tolerated dose (MTD). An expansion cohort (n = 15) was investigated to obtain additional efficacy information. Sequential fluorodeoxyglucose positron emission tomography (FDG-PET) was used as a surrogate marker of response.ResultsOverall 18 patients were recruited into the study. Fifteen patients received the MTD, which was everolimus 5 mg orally (PO) once daily (OD) and dovitinib 200 mg PO day 1–5/7. The MTD was associated with toxicity, which included fatigue, mucositis and diarrhoea in 73%, 53% and 53% (Common Toxicity Criteria (CTC) grade 1–4) of patients, respectively. Frequent biochemical abnormalities occurred (such as hypertriglyceridaemia in 67%). Higher doses of the combination were not tolerable due to grade 3 fatigue in 2/3 patients and grade 3 nausea in 1/3 patients within 1 month of therapy. The response rate at the MDT was 1/15 (7%) while the progression free survival for the MTD was 7 months (95% confidence interval (CI) 2.2–11 months). Pharmacokinetic data at the MTD showed stable kinetics with time.ConclusionDovitinib and everolimus had modest activity, but did not meet all of the planned efficacy end-points. Fatigue was the dose limiting toxicity.     

First-Line Mammalian Target of Rapamycin Inhibition in Metastatic Renal Cell Carcinoma: An Analysis of Practice Patterns From the International Metastatic Renal Cell Carcinoma Database Consortium

Introduction/BackgroundApproval of the mTOR inhibitors for the treatment of mRCC was based on efficacy in poor-risk patients in the first-line setting for temsirolimus and in vascular endothelial growth factor inhibitor-refractory patients for everolimus. We strove to characterize temsirolimus and everolimus use and effectiveness in the first-line setting.Patients and MethodsWe performed a retrospective database analysis of mRCC patients who received mTOR inhibitors as first-line targeted therapy. The Kaplan-Meier product-limit method was used to estimate the distribution of progression-free survival (PFS) and overall survival (OS).ResultsWe identified 127 mRCC patients who had received a first-line mTOR inhibitor. Temsirolimus was administered in 93 patients (73%) and everolimus in 34 patients (27%). The main reasons for choice of temsirolimus were poor-risk disease (38%), non-clear cell histology (27%), and clinical trial availability (15%), whereas clinical trial (82%) and non-clear cell histology (6%) drove everolimus selection. Of the temsirolimus and everolimus patients, 58% and 32% were poor-risk according to the International mRCC Database Consortium criteria, respectively. The median PFS and OS were 3.4 and 12.5 months and 4.8 and 15.9 months with temsirolimus and everolimus, respectively. Although limited by small numbers, this study characterizes a real-world, international experience with the use of mTOR inhibition in treatment-naive mRCC patients.ConclusionPoor-risk RCC, non-clear cell histology, and clinical trials were the predominant reasons for mTOR inhibitor selection in the front-line setting. Because of the different patient populations in which they were administered, direct comparisons of the front-line efficacy of temsirolimus and everolimus cannot be made.