title: Preclinical in vivo evaluation of rapamycin in human malignant peripheral nerve sheath explant xenograft.
abstract: Neurofibromatosis type 1 (NF1) patients are prone to the development of malignant tumors, the most common being Malignant Peripheral Nerve Sheath Tumor (MPNST). NF1-MPNST patients have an overall poor survival due to systemic metastasis. Currently, the management of MPNSTs includes surgery and radiation; however, conventional chemotherapy is not very effective, underscoring the need for effective biologically-targeted therapies. Recently, the NF1 gene product, neurofibromin, was shown to negatively regulate the phosphoinositide-3-kinase (PI3K)/Protein Kinase-B (Akt)/mammalian Target Of Rapamycin (mTOR) pathway, with loss of neurofibromin expression in established human MPNST cell lines associated with high levels of mTOR activity. We developed and characterized a human NF1-MPNST explant grown subcutaneously in NOD-SCID mice, to evaluate the effect of the mTOR inhibitor rapamycin. We demonstrate that rapamycin significantly inhibited human NF1-MPNST mTOR pathway activation and explant growth in vivo at doses as low as 1.0 mg/kg/day, without systemic toxicities. While rapamycin was effective at reducing NF1-MPNST proliferation and angiogenesis, with decreased CyclinD1 and VEGF respectively, there was no increase in tumor apoptosis. Rapamycin effectively decreased activation of S6 downstream of mTOR, but there was accompanied increased Akt activation. This study demonstrates the therapeutic potential and limitations of rapamycin in NF1-associated, and likely sporadic, MPNSTs.
authors.affiliation: The Arthur and Sonia Labatt Brain Tumor Research Centre, Hospital for Sick Children, University of Toronto, Ontario, Canada.
authors.forename: Priya
authors.initials: P
authors.lastname: Bhola
authors.forename: Sutapa
authors.initials: S
authors.lastname: Banerjee
authors.forename: Joydeep
authors.initials: J
authors.lastname: Mukherjee
authors.forename: Anand
authors.initials: A
authors.lastname: Balasubramanium
authors.forename: Vedant
authors.initials: V
authors.lastname: Arun
authors.forename: Zia
authors.initials: Z
authors.lastname: Karim
authors.forename: Kelly
authors.initials: K
authors.lastname: Burrell
authors.forename: Sidney
authors.initials: S
authors.lastname: Croul
authors.forename: David H
authors.initials: DH
authors.lastname: Gutmann
authors.forename: Abhijit
authors.initials: A
authors.lastname: Guha
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D019938:Cyclin D1 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009456:Neurofibromatosis 1 / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010524:Peripheral Nervous System Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases; D047368:Tumor Burden / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D055815:Young Adult
chemical_list: D000903:Antibiotics, Antineoplastic; D042461:Vascular Endothelial Growth Factor A; D019938:Cyclin D1; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus