AMACR amplification in myxofibrosarcomas: a mechanism of overexpression that promotes cell proliferation with therapeutic relevance.
OBJECTIVE
Myxofibrosarcomas frequently display arm-level gains on 5p. We characterized the pathogenetic and therapeutic relevance of the α-methylacyl coenzyme A racemase (AMACR) at 5p13.3.


METHODS
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 = 0.0002 for overexpression; P = 0.0062 for amplification). AMACR protein overexpression also independently portended adverse outcome (DSS, P = 0.007; MFS, P = 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.


CONCLUSIONS
Overexpressed AMACR in myxofibrosarcomas can be amplification-driven, associated with tumor aggressiveness, and may be relevant as a druggable target.
Department of Pathology, Chi-Mei Medical Center, Tainan, Taiwan. Institute of Clinical Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan. Department of Biotechnology, Southern Taiwan University, Tainan, Taiwan.
Chien-Feng
CF
Li
Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Fu-Min
FM
Fang
Department of Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Jui
J
Lan
Department of Orthopedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Jun-Wen
JW
Wang
Institute of Molecular and Genomic Medicine, National Health Research Institutes, Tainan, Taiwan.
Hsing-Jien
HJ
Kung
National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan.
Li-Tzong
LT
Chen
Department of Pathology, Chi-Mei Medical Center, Tainan, Taiwan.
Tzu-Ju
TJ
Chen
Division of Oncology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Shau-Hsuan
SH
Li
Institute of Biosignal Transduction, National Cheng Kung University, Tainan, Taiwan.
Yu-Hui
YH
Wang
Department of Pathology, Changhua Christian Hospital, Changhua, Taiwan.
Hui-Chun
HC
Tai
Department of Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Shih-Chen
SC
Yu
Department of Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan. a120600310@yahoo.com.
Hsuan-Ying
HY
Huang
D000328:Adult; D000368:Aged; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002453:Cell Cycle / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016000:Cluster Analysis; D055028:Comparative Genomic Hybridization; D019938:Cyclin D1 / Q000235:genetics; D056906:Cyclin T / Q000235:genetics; D066264:Datasets as Topic; D004195:Disease Models, Animal; D005260:Female; D005354:Fibrosarcoma / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D005784:Gene Amplification; D018628:Gene Dosage; D015870:Gene Expression; D020869:Gene Expression Profiling; D064593:Heterografts; D006801:Humans; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D011379:Prognosis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D019998:Racemases and Epimerases / Q000235:genetics* / Q000378:metabolism; D047368:Tumor Burden / Q000235:genetics
D056906:Cyclin T; D012333:RNA, Messenger; D019938:Cyclin D1; D046988:Proteasome Endopeptidase Complex; D019998:Racemases and Epimerases; C108352:alpha-methylacyl-CoA racemase