[1755] Morphoproteomic Profiling of Choroid Plexus Carcinoma Reveals Constitutive Activation of the mTOR and ERK Pathways with Cell Cycle Progression

RE Brown, J Buryanek, JE Wolff. University of Texas-Medical School, Houston, TX; University of Texas-M.D.Anderson, Houston, TX

Background: Choroid plexus carcinoma (CPC) is a rare pediatric malignancy with a poor prognosis despite conventional therapies. Understanding its molecular biology should provide insight into targeted therapeutic options. To this end, we performed morphoproteomic profiling on two such cases.
Design: Sections of an original and recurrent CPC, were available for analysis. Immunohistochemical probes were applied to detect the following: 1. phosphorylated (p)-mammalian target of rapamycin (mTOR) [Ser 2448]; p-Akt (Ser 473); p-p70S6K (Thr 389); and p-extracellular signal-regulated kinase (ERK) 1/2 (Thr 202/Tyr 204); and 2. cell cycle-related proteins to include nuclear Ki-67(G1, S, G2 and M phases), S-phase kinase-associated protein (Skp)2 (promotes G1 to S), p53 (wild type regulates, mutant form permissive in G1 to S) and topoisomerase II alpha (facilitates S to G2/M). Quantification of the nuclear percentages was carried out, whenever possible, by an automated cellular imaging system (ACIS). Mitotic indices were calculated as an average of mitotic figures in the most mitotically active regions per sets of ten high power fields (h.p.f.'s).
Results: Constitutive activation of the Akt/mTOR and ras/Raf kinase/ERK pathways is evident in both cases with predominantly plasmalemmal and cytoplasmic expressions of p-Akt (Ser 473) and p-mTOR (Ser 2448), favoring the mTORC1 pathway, and with nuclear expression of p-p70S6K (Thr 389) and nuclear p-ERK 1 / 2 (Thr 202/Tyr 204). Correlative cell cycle progression was noted with mean nuclear expressions in each of the cases as follows: Ki-67 at 14.0 and 11.6%, Skp2 at ∼20% (visual quantification) and 7.8% and 28 and 27 mitotic figures per 10 h.p.f.'s, respectively. Nuclear topoisomerase II alpha at 96 and 52.1% and p53 at ∼30 and 63% (probably mutant form) were noted.
Conclusions: Morphorproteomic profiling reveals constitutive activation of the Akt/mTOR and ras /Raf kinase/ERK pathways, which appears to be the first report of its kind in CPC. Such activation coincides with downstream signal transduction from insulin-like growth factor (IGF) II/IGF-type 1 receptor and platelet-derived growth factor receptor, previously reported in CPC. Moreover, it accords with the cell cycle progression and provides opportunities to apply combinatorial therapies to target the mTORC1 pathway, cell cycle progression and topoisomerase II alpha in CPC.
Category: Pediatrics

Monday, March 22, 2010 11:30 AM

Platform Session: Section H 2, Monday Morning


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