Morphoproteomic profiling of the mammalian target of rapamycin (mTOR) signaling pathway in desmoplastic small round cell tumor (EWS/WT1), Ewing's sarcoma (EWS/FLI1) and Wilms' tumor(WT1)
Authors: Vivek Subbiah, Robert E Brown, Yunyun Jiang, Jamie Buryanek, Andrea Hayes-Jordan, Razelle Kurzrock, Pete M Anderson
Journal: PLoS One (2013)
MeSH terms: Desmoplastic Small Round Cell Tumor / metabolism, Proteomics, Sarcoma, Ewing / metabolism, Signal Transduction, TOR Serine-Threonine Kinases / metabolism, Wilms Tumor / metabolism, Case Reports, Research Support, N.I.H., Extramural, Adolescent, Adult, Desmoplastic Small Round Cell Tumor / pathology, Female, Humans, Immunohistochemistry, Male, Mechanistic Target of Rapamycin Complex 1, Mechanistic Target of Rapamycin Complex 2, Multiprotein Complexes / metabolism, Oncogene Proteins, Fusion / metabolism, Proto-Oncogene Protein c-fli-1 / metabolism, RNA-Binding Protein EWS / metabolism, Sarcoma, Ewing / pathology, Somatomedins / metabolism, WT1 Proteins / metabolism, Wilms Tumor / pathology, Young Adult, EWS-FLI fusion protein, EWS1-WT1 fusion protein, human, Multiprotein Complexes, Oncogene Proteins, Fusion, Proto-Oncogene Protein c-fli-1, RNA-Binding Protein EWS, Somatomedins, WT1 Proteins, WT1 protein, human, MTOR protein, human, Mechanistic Target of Rapamycin Complex 1, Mechanistic Target of Rapamycin Complex 2, TOR Serine-Threonine Kinases

Background:
Desmoplastic small round cell tumor (DSRCT) is a rare sarcoma in adolescents and young adults. The hallmark of this disease is a EWS-WT1 translocation resulting from apposition of the Ewing's sarcoma (EWS) gene with the Wilms' tumor (WT1) gene. We performed morphoproteomic profiling of DSRCT (EWS-WT1), Ewing's sarcoma (EWS-FLI1) and Wilms' tumor (WT1) to better understand the signaling pathways for selecting future targeted therapies.
Methodology:
This pilot study assessed patients with DSRCT, Wilms' tumor and Ewing's sarcoma. Morphoproteomics and immunohistochemical probes were applied to detect: p-mTOR (Ser2448); p-Akt (Ser473); p-ERK1/2 (Thr202/Tyr204); p-STAT3 (Tyr 705); and cell cycle-related analytes along with their negative controls.
Principal findings:
In DSRCT the PI3K/Akt/mTOR pathway is constitutively activated by p-Akt (Ser 473) expression in the nuclear compartment of the tumor cells and p-mTOR phosphorylated on Ser 2448, suggesting mTORC2 (rictor+mTOR) as the dominant form. Ewing's sarcoma had upregulated p-Akt and p-mTOR, predominantly mTORC2. In Wilm's tumor, the mTOR pathway is also activated with most tumor cells moderately expressing p-mTOR (Ser 2448) in plasmalemmal and cytoplasmic compartments. This coincides with the constitutive activation of one of the downstream effectors of the mTORC1 signaling pathway, namely p-p70S6K (Thr 389). There was constitutive activation of the Ras/Raf/ERK pathway p-ERK 1/2 (Thr202/Tyr204) expression in the Wilms tumor and metastatic Ewing's sarcoma, but not in the DSRCT.
Conclusion:
MORPHOPROTEOMIC TUMOR ANALYSES REVEALED CONSTITUTIVE ACTIVATION OF THE MTOR PATHWAY AS EVIDENCED BY: (a) expression of phosphorylated (p)-mTOR, p-p70S6K; (b) mTORC 2 in EWS and DSRCT; (c) ERK signaling was seen in the advanced setting indicating these as resistance pathways to IGF1R related therapies. This is the first morphoproteomic study of such pathways in these rare malignancies and may have potential therapeutic implications. Further study using morphoproteomic assessments of these tumors are warranted.