Characterization of Gene Amplification-Driven AMACR Overexpression in Myxofibrosarcoma: Potential Implications in Tumor Progression and Therapeutics
Chien-Feng Li, Hsuan-Ying Huang. Chi-Mei Medical Center, Tainan, Taiwan; Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan
Background: Myxofibrosarcoma is genetically complex and remains obscure in molecular determinants of clinical aggressiveness. Despite 5p being frequently amplified in myxofibrosarcoma, the harbored candidate oncogenes remained to be characterized. In our pilot genomic profiling, AMACR gene at 5p13.3 was differentially overrepresented in myxofibrosarcomas.
Design: To evaluate clinical significance of AMACR gene status and protein expression, we performed immunohistochemical and FISH assays for 105 independent myxofibrosarcomas on tissue microarrays and correlated the results with clincopathological variables, disease-specific survival (DSS), and metastasis-free survival (MFS). AMACR mRNA expression folds were by quantified in available fresh samples. AMACR-amplified NMFH-1 and NMFH-2 myxofibrosarcoma cell lines were stably silenced with short-hairpin RNAs and evaluated by BrudU and soft agar assays.
Results: Present in 28/105 (27%) primary myxofibrosarcomas, AMACR overexpression was highly associated with higher grades (p<0.001) and gene amplification (p<0.001; 17/28, 61%). However, AMACR gene was non-amplified in 11/28 (39%) tumors overexpressing AMACR. Gene amplification was positively related to higher grades (p=0.002) and advanced stages (p=0.039). Besides higher grades, both AMACR overexpression (p<0.0001 for both endpoints) and gene amplification (DSS, p=0.0002; MFS, p=0.0062) univariately correlated with poor prognosis. However, only AMACR overexpression independently portended adverse outcomes (DSS, p=0.0071; MFS, p=0.0007). In vitro, stable AMACR-knockdown NMFH-1 and NMFH-2 lines showed suppressed cell proliferation and anchorage-independent growth of myxofibrosarcoma cells.
Conclusions: Driven mostly by gene amplification, AMACR overexpression is present in a significant subset and confers tumor aggressiveness in myxofibrosarcomas.
Category: Bone & Soft Tissue
Monday, March 19, 2012 1:00 PM
Poster Session II # 18, Monday Afternoon