High WT1 expression is associated with very poor survival of patients with osteogenic sarcoma metastasis.
OBJECTIVE
Although metastasis is the primary determinant of poor survival of patients with osteogenic sarcoma, some patients live much longer than others, indicating metastatic heterogeneity underlying survival outcome. The purpose of the investigation was to identify genes underlying survival outcome of patients with osteogenic sarcoma metastasis.


METHODS
We have used microarray to first compare mRNA expression between normal bone and osteogenic sarcoma specimens, identified genes overexpressed in osteogenic sarcoma, and compared expression of the selected gene between a poorly metastatic (SAOS) and two highly metastatic cell lines (LM8 and 143B). Finally, expression of the selected gene was assessed by immunostaining of osteogenic sarcoma samples with known survival outcome.


RESULTS
Microarray analysis revealed 5.3-fold more expression of WT1 mRNA in osteogenic sarcoma compared with normal bone and >2-fold overexpression in 143B and LM8 cells compared with SAOS. Furthermore, WT1 mRNA was absent in normal bone (10 of 10) by reverse transcription-PCR but present in osteogenic sarcoma-derived cell lines (5 of 8). One hundred percent (42 of 42) of low-grade osteogenic sarcoma specimens expressed no WT1 as determined by immunostaining; however, 24% (12 of 49) of the high-grade specimens showed intense staining. Mean survival of patients with high-grade metastatic osteogenic sarcoma but low WT1 staining (27 of 37) was 96.5 +/- 129.3 months, whereas mean survival of patients with high-grade metastatic osteogenic sarcoma having intense staining (10 of 37) was 18.3 +/- 12.3 months (P > 0.0143). All splice variants of WT1 mRNA, including a hitherto unknown variant (lacking exons 4 and 5), were found to be expressed in osteogenic sarcoma.


CONCLUSIONS
WT1 seems to be associated with very poor survival of patients with osteogenic sarcoma metastasis.
Srivastava
Alok
A
Department of Orthopedics, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Fuchs
Bruno
B
Zhang
Kunbo
K
Ruan
Ming
M
Halder
Chandralekha
C
Mahlum
Eric
E
Weber
Kristin
K
Bolander
Mark E
ME
Sarkar
Gobinda
G
D001483:Base Sequence; D001859:Bone Neoplasms / Q000401:mortality* / Q000473:pathology*; D001842:Bone and Bones / Q000378:metabolism*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008969:Molecular Sequence Data; D009362:Neoplasm Metastasis; D020411:Oligonucleotide Array Sequence Analysis; D012516:Osteosarcoma / Q000401:mortality* / Q000473:pathology*; D011379:Prognosis; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016896:Treatment Outcome; D025721:WT1 Proteins / Q000096:biosynthesis* / Q000737:chemistry
D012333:RNA, Messenger; D025721:WT1 Proteins