Midkine enhances soft-tissue sarcoma growth: a possible novel therapeutic target.
OBJECTIVE
New therapeutic targets for soft-tissue sarcoma (STS) treatment are critically needed. Midkine (MK), a multifunctional cytokine, is expressed during midgestation but is highly restricted in normal adult tissues. Renewed MK expression was shown in several malignancies where protumorigenic properties were described. We evaluated the expression and function of MK in STS.


METHODS
Immunohistochemistry, reverse transcription-PCR, and Western blotting (WB) evaluated MK expression in human STS tissues and cell lines. WB and flow cytometry analyzed MK receptor expression. Cell growth assays evaluated the effect of MK on STS cell growth, and WB assessed MK downstream signaling. MK knock-in and knockout experiments further evaluated MK function. The growth of parental versus MK-transfected human fibrosarcoma cells was studied in vivo.


RESULTS
MK was found to be overexpressed in a variety of human STS histologies. Using a rhabdomyosarcoma (RMS) tissue microarray, cytoplasmic and nuclear MK was identified; nuclear MK expression was significantly increased in metastases. Similarly, several STS cell lines expressed and secreted MK; RMS cells exhibited nuclear MK. STS cells also expressed the MK receptors protein tyrosine phosphatase zeta and lipoprotein receptor-related protein. MK significantly enhanced STS cell growth potentially via the Src and extracellular signal-regulated kinase pathways. STS cells stably transfected with MK exhibited increased growth in vitro and in vivo. MK-expressing human STS xenografts showed increased tumor-associated vasculature. Furthermore, MK knockdown resulted in decreased STS cell growth, especially in RMS cells.


CONCLUSIONS
MK enhances STS tumor growth; our results support further investigation of MK and its receptors as therapeutic targets for human STS.
Jin
Zeming
Z
Department of Surgical Oncology, Division of Quantitative Sciences, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Lahat
Guy
G
Korchin
Borys
B
Nguyen
Theresa
T
Zhu
Quan-Sheng
QS
Wang
Xuemei
X
Lazar
Alexander J
AJ
Trent
Jonathan
J
Pollock
Raphael E
RE
Lev
Dina
D
D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000096:biosynthesis; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D008819:Mice, Nude; D000078792:Midkine; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis; D017978:Receptors, Growth Factor / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012509:Sarcoma / Q000378:metabolism* / Q000473:pathology*; D012983:Soft Tissue Neoplasms / Q000378:metabolism* / Q000473:pathology*; D046888:Tissue Array Analysis
D016207:Cytokines; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008562:Membrane Glycoproteins; D017978:Receptors, Growth Factor; C408049:midkine receptors; D000078792:Midkine; D017027:Protein Tyrosine Phosphatases