title: Novel withanolides target medullary thyroid cancer through inhibition of both RET phosphorylation and the mammalian target of rapamycin pathway.
abstract: BACKGROUND
  Despite development of current targeted therapies for medullary thyroid cancer (MTC), long-term survival remains unchanged. Recently isolated novel withanolide compounds from Solanaceae physalis are highly potent against MTCs. We hypothesize that these withanolides uniquely inhibit RET phosphorylation and the mammalian target of rapamycin (mTOR) pathway in MTC cells as a mechanism of antiproliferation and apoptosis.
  
  
  METHODS
  MTC cells were treated with novel withanolides and MTC-targeted drugs. In vitro studies assessed cell viability and proliferation (MTS; trypan blue assays), apoptosis (flow cytometry with Annexin V/PI staining; confirmed by Western blot analysis), long-term cytotoxic effects (clonogenic assay), and suppression of key regulatory proteins such as RET, Akt, and mTOR (by Western blot analysis).
  
  
  RESULTS
  The novel withanolides potently reduced MTC cell viability (half maximal inhibitory concentration [IC(50)], 270-2,850 nmol/L; 250-1,380 nmol/L for vandetanib; 360-1,640 nmol/L for cabozantinib) with induction of apoptosis at <1,000 nmol/L of drug. Unique from other targeted therapies, withanolides suppressed RET and Akt phosphorylation and protein expression (in a concentration- and time-dependent manner) as well as mTOR activity and translational activity of 4E-BP1 and protein synthesis mediated by p70S6kinase activation at IC(50) concentrations.
  
  
  CONCLUSIONS
  Novel withanolides from Physalis selectively and potently inhibit MTC cells in vitro. Unlike other MTC-targeted therapies, these compounds uniquely inhibit both RET kinase activity and the Akt/mTOR prosurvival pathway. Further translational studies are warranted to evaluate their clinical potential.
authors.affiliation: Department of Surgery, University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: Abbas K
authors.initials: AK
authors.lastname: Samadi
authors.forename: Joseph
authors.initials: J
authors.lastname: Bazzill
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhang
authors.forename: Rob
authors.initials: R
authors.lastname: Gallagher
authors.forename: Hauping
authors.initials: H
authors.lastname: Zhang
authors.forename: Rao
authors.initials: R
authors.lastname: Gollapudi
authors.forename: Kelly
authors.initials: K
authors.lastname: Kindscher
authors.forename: Barbara
authors.initials: B
authors.lastname: Timmermann
authors.forename: Mark S
authors.initials: MS
authors.lastname: Cohen
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D018278:Carcinoma, Neuroendocrine; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D014410:Tumor Stem Cell Assay; D054358:Withanolides / Q000627:therapeutic use*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D054358:Withanolides; C546842:MTOR protein, human; D051096:Proto-Oncogene Proteins c-ret; D058570:TOR Serine-Threonine Kinases