Differential apoptosis gene expression in pediatric tumors of the kidney.
OBJECTIVE
Apoptosis, or programmed cell death, is essential in maintaining normal homeostasis of tissues. The process of apoptosis is controlled by numerous pro- and antiapoptotic factors. Variations in expression of such factors may account for some variations in tumor behavior. This study evaluates the expression of apoptotic mRNA species in pediatric renal tumors to determine whether a pattern of differential apoptosis gene expression correlates with tumor grade and type.


METHODS
Twenty-five frozen tissue specimens were obtained from patients undergoing biopsy or resection of pediatric renal tumors before chemotherapy: Wilms' tumor stage II (WT-II, n = 4); Wilms' tumor stage III/IV (WT-III/IV, n = 4); clear cell sarcoma of the kidney stage III (CCSK, n = 2); rhabdoid tumor of the kidney stage III/IV (RTK, n = 4); and normal kidney (NK, n = 11). An RNase Protection Assay (RPA) was performed for 19 pro- and antiapoptotic mRNA species to detect and quantify expression (percentage of GAPDH expressed). Expression of specific mRNAs of interest were confirmed by Western Blot (WB).


RESULTS
The expression of apoptotic mRNA species varied markedly between tumors. WT-II expressed greater amounts of proapoptotic receptor mRNA than CCSK or RTK. (Fas, 17.0+/-2.7% v. 2.5+/-0.5% v. 3.3+/-0.9%; P<.02; DR5, 77.0+/-8.8% v. 13.5+/-0.5% v. 27.0+/-4.8; P<.001; TNF-R, 71.3+/-17.0% v. 21.0+/-4.0% v. 29.0+/-5.0%; P<.07, respectively). Surprisingly, antiapoptotic factors (e.g., bcl-2 and bcl-xl) were not overexpressed in poor prognostic tumors (CCSK, RTK) compared with those with good prognosis (WT). Expression of TRAIL (a ligand for DR4 and DR5) was significantly lower in CCSK and RTK than in normal kidney (9.5+/-1.5% v. 56.1+/-10.1%; P = .01).


CONCLUSIONS
Proapoptotic receptors are expressed at greater levels in good prognostic tumors, and this finding is compatible with their clinical behavior. Knowledge of differential apoptotic gene expression is of potential value in predicting prognosis and treating such tumors with targeted ligands.
Takamizawa
S
S
Department of Surgery, University of Iowa Hospitals & Clinics, Iowa City 52242, USA.
Okamoto
S
S
Bishop
W
W
Wen
J
J
Kimura
K
K
Sandler
A
A
D017209:Apoptosis / Q000235:genetics*; D015153:Blotting, Western; D002648:Child; D015870:Gene Expression; D019254:Genes, bcl-2 / Q000502:physiology; D006684:HLA-DR Antigens / Q000502:physiology; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology; D009367:Neoplasm Staging; D009373:Neoplasms, Germ Cell and Embryonal / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism; D018335:Rhabdoid Tumor / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D009396:Wilms Tumor / Q000235:genetics / Q000473:pathology / Q000503:physiopathology
D006684:HLA-DR Antigens; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha