AMACRAmplification in Myxofibrosarcomas: A Mechanism of Overexpression That Promotes Cell Proliferation with Therapeutic Relevance

Abstract

Purpose: Myxofibrosarcomas frequently display arm-level gains on 5p. We characterized the pathogenetic and therapeutic relevance of the a-methylacyl coenzyme A racemase (AMACR) at 5p13.3.Experimental Design: AMACR mRNA expression in myxofibrosarcomas was analyzed using the public transcriptome and laser-microdissected sarcoma cells. We performed florescence in situ hybridization (FISH) and immunohistochemistry in independent samples for clinical correlates. In AMACR-overexpressing myxofibrosarcoma cells and xenografts, we elucidated the biologic function of AMACR using RNA interference and explored the therapeutic effect and mechanism of an AMACR inhibitor, ebselen oxide.Results: AMACR protein overexpression and gene amplification were significantly associated with each other (P < 0.001), with higher tumor grades (both P 0.002), and univariately with worse metastasis-free survival (MFS; both P < 0.0001) and disease-specific survival (DSS; P ¼ 0.0002 for overexpression; P ¼ 0.0062 for amplification). AMACR protein overexpression also independently portended adverse outcome (DSS, P ¼ 0.007; MFS, P ¼ 0.001). However, 39% of AMACR-overexpression cases did not show gene amplification, implying alternative regulatory mechanisms. In myxofibrosarcoma cell lines, stable AMACR knockdown suppressed cell proliferation, anchorage-independent growth, and expression of cyclin D1 and cyclin T2. These growth-promoting attributes of AMACR were corroborated in the AMACR-silenced xenograft model and AMACR-underexpressed myxofibrosarcomas, showing decreased labeling for cyclin D1, cyclin T2, and Ki-67. Compared with fibroblasts, AMACR-expressing myxofibrosarcoma cells were more susceptible to ebselen oxide, which not only decreased viable cells, promoted proteasome-mediated degradation of AMACR protein, and induced cellular apoptosis in vitro, but also dose-dependently suppressed xenografted tumor growth in vivo.

Primary renal myxofibrosarcoma

“…Nuclear expression of bcl2 and p53 serves as a marker for cells with high proliferative potential, correlates with malignant transformation or progressive malignancy, and may indicate aggressive behavior [11,20,21]. Overexpressed AMACR in MFS can be amplification-driven and associated with tumor aggressiveness [22]. CD99 positivity has also been reported in MFS [19].…”

PTP4A3 Independently Predicts Metastasis and Survival in Upper Tract Urothelial Carcinoma Treated with Radical Nephroureterectomy

“…We measured mRNA abundance of PTP4A3 (Hs02341135_m1) with predesigned TaqManÒ assay reagents and an Applied Biosystems Ò StepOnePlusÔ System as previously described. 12 The expression fold of PTP4A3 relative to normal urothelium was calculated using the comparative threshold count method after normalization to POLR2A (Hs01108291_m1) as the internal control.…”

Integrin-α10 Dependency Identifies RAC and RICTOR as Therapeutic Targets in High-Grade Myxofibrosarcoma

“…The most common copy number gain/amplification was on 5p, occurring in 60% of myxofibrosarcomas (8). Among the genes in this amplicon, TRIO, SKP2 and AMACR were shown to be overexpressed and SKP2 and AMACR were found to be potential oncogenes in myxofibrosarcoma (11, 12). It remains unclear whether any other genes in the 5p amplicon serve as critical drivers in myxofibrosarcoma.…”