Oncogenic Mutation Screening in Solitary Fibrous Tumors

1. Oncogenic Mutation Screening in Solitary Fibrous Tumors Elizabeth G. Demicco, KhalidaWani, Kenneth Aldape, Alexander J. Lazar, and Wei-Lien Wang

2. Solitary Fibrous Tumor (SFT)Background Phenotypic spectrum comprising classic solitary fibrous tumor (hypocellular variant) and hemangiopericytoma (hypercellular variant) Rarely metastasizing– Behavior can be difficult to predict

3. Solitary Fibrous Tumor (SFT)Background • Limited data on cytogenetic abnormalities. • Relatively simple genomic alterations • Few recurrent features • Limited data on genetic abnormalities • PDGFRB mutations, 2/88 pleural SFT • No mutations in DDR1 (n=8), ERBB2 (n=10), FGFR1 (n=15), PDGFRB (n=39) • TP53 one case, dedifferentiated SFT of nasal cavity

4. Purpose • Examine a large series of solitary fibrous tumors for common oncogenic mutations.

5. Screening Approach to Mutational Analysis (Sequenom MassArray) Detection method for single nucleotide polymorphisms (SNP) Step 1. PCR-based Allele (WT vs. mutant) specific probes Single nucleotide extension across site of SNP Different probe sizes allow for allele differentiation and multiplexed reaction Step 2. MALDI-TOF mass spectrometry Analyze primer extension product Time of flight mass spectrometry differentiates based on probe size

7. Tumor Characteristics 122 tumors (105 patients) 72 Primary 9 Local recurrence 41 Metastasis 13 Patients with multiple tumors tested 6 primary and metastasis(es) 5 multiple metastases 2 local recurrence(s) +/- metastasis

8. Patient Demographics

9. General Quality Control Indicators

10. Potential Mutations Identified by Sequenom * Mutation identified on forward probe, WT on reverse ** Problems with probes later reported – Determined to be WT by CAST-PCR

11. Characteristics of Tumors with Identified SNPs * Presence of SNP did not correlate with c-MET expression by IHC

12. MET C3029T (p.T1010I) and C2962T (p.R988C) Also designated as T992I and R970C Juxtamembrane domain Initially reported as rare somatic oncogenic mutations Identified in a wide range of tumors Frequency in involved cancers ~1-10% Later proposed to represent germline polymorphisms Seen in ~1% of individuals without cancer (1/96) Germline in several patients with cancer No evidence of transformation in cell models T1010I as cooperative germline oncogenic mutation? Identified in ~4.5% familial CRC Mutation proposed to indirectly activate c-MET via inhibition of inhibitor Not initiator, may promote progression

13. ALK T3733G (p.F1245V) Kinase-activating mutation Rare mutation Reported in neuroblastoma

14. KRAS C181A (p.Q61K) Activating mutation reported rarely in colonic and lung adenocarcinoma, misc. other carcinomas various sites Much more rare than the equivalent NRAS mutation

15. Summary We performed screening SNP analysis in a large series of SFT Confirmed that SFT have low frequency of mutations in oncogenes commonly reported in other malignancies 7/122 cases (5.7%) Abdominal location predominant Insufficient data on relevance to status, prognosis

16. Conclusions Mutations in commonly identified oncogenes do not appear to function in pathogenesis of SFT. Alternative mechanisms? Mutations in uncommon genes Imprinting miRNA regulation Studies are ongoing

17. Thank You.