Prospects for mTOR inhibitor use in patients with polycystic kidney disease and hamartomatous diseases.
Mammalian target of rapamycin (mTOR) is the core component of two complexes, mTORC1 and mTORC2. mTORC1 is inhibited by rapamycin and analogues. mTORC2 is impeded only in some cell types by prolonged exposure to these compounds. mTOR activation is linked to tubular cell proliferation in animal models and human autosomal dominant polycystic kidney disease (ADPKD). mTOR inhibitors impede cell proliferation and cyst growth in polycystic kidney disease (PKD) models. After renal transplantation, two small retrospective studies suggested that mTOR was more effective than calcineurin inhibitor-based immunosuppression in limiting kidney and/or liver enlargement. By inhibiting vascular remodeling, angiogenesis, and fibrogenesis, mTOR inhibitors may attenuate nephroangiosclerosis, cyst growth, and interstitial fibrosis. Thus, they may benefit ADPKD at multiple levels. However, mTOR inhibition is not without risks and side effects, mostly dose-dependent. Under certain conditions, mTOR inhibition interferes with adaptive increases in renal proliferation necessary for recovery from injury. They restrict Akt activation, nitric oxide synthesis, and endothelial cell survival (downstream from mTORC2) and potentially increase the risk for glomerular and peritubular capillary loss, vasospasm, and hypertension. They impair podocyte integrity pathways and may predispose to glomerular injury. Administration of mTOR inhibitors is discontinued because of side effects in up to 40% of transplant recipients. Currently, treatment with mTOR inhibitors should not be recommended to treat ADPKD. Results of ongoing studies must be awaited and patients informed accordingly. If effective, lower dosages than those used to prevent rejection would minimize side effects. Combination therapy with other effective drugs could improve tolerability and results.
Torres
Vicente E
VE
Division of Nephrology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, Minnesota 55905, USA. torres.vicente@mayo.edu
Boletta
Alessandra
A
Chapman
Arlene
A
Gattone
Vincent
V
Pei
York
Y
Qian
Qi
Q
Wallace
Darren P
DP
Weimbs
Thomas
T
Wüthrich
Rudolf P
RP
D000818:Animals; D004195:Disease Models, Animal; D006222:Hamartoma / Q000188:drug therapy* / Q000201:enzymology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007690:Polycystic Kidney Diseases / Q000188:drug therapy* / Q000201:enzymology; D047428:Protein Kinase Inhibitors / Q000009:adverse effects / Q000627:therapeutic use*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018570:Risk Assessment; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D016896:Treatment Outcome
D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases