The equilibrium of XIAP and Smac/DIABLO expression is gradually deranged during the development and progression of testicular germ cell tumours.
Overexpression of the inhibitor of apoptosis protein (IAP) XIAP (BIRC4) and downregulation of its antagonist Smac/DIABLO (DIABLO) are associated with the onset and progression of various malignancies. In this study, real-time RT-PCR was used to quantify the mRNA expression of XIAP and Smac/DIABLO in normal testicular tissue (n = 19), testicular carcinoma in situ (CIS; n = 4), testicular seminomas (n = 64) and non-seminomatous germ cell tumours (NSGCT; n = 35). XIAP and Smac/DIABLO were commonly expressed in normal and malignant testicular tissue with no apparent differences in XIAP mRNA levels among the histologic subgroups. Smac/DIABLO levels, on the other hand, gradually decreased from normal testicular tissue to CIS and seminomas and finally to NSGCT (p < 0.001). An inverse trend was observed when calculating the XIAP-to-Smac/DIABLO ratio (p < 0.001). This ratio differed when comparing normal testicular tissue with CIS (p = 0.014), seminomas (p < 0.001) and NSGCT (p < 0.001) and when comparing seminomas with NSGCT (p = 0.002), whereas no such difference was observed between CIS and seminomas (p = 0.302). TGCT patients dichotomized by the overall median XIAP-to-Smac/DIABLO ratio were more likely to present with a high ratio in clinical stage (CS) III than in CS I or II (p = 0.034). These data indicate that the balance of mRNA expression between XIAP and Smac/DIABLO is altered in favour of antiapoptotic XIAP during the development and progression of TGCT. Thus the expression of proapoptotic Smac/DIABLO is lowest in NSGCT and stage III tumours.
Kempkensteffen
Carsten
C
Department of Urology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany. carsten.kempkenstefen@charite.de
Jäger
Tobias
T
Bub
Johannes
J
Weikert
Steffen
S
Hinz
Stefan
S
Christoph
Frank
F
Krause
Hans
H
Schostak
Martin
M
Miller
Kurt
K
Schrader
Mark
M
D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D017931:DNA Primers; D018450:Disease Progression; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009373:Neoplasms, Germ Cell and Embryonal / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013736:Testicular Neoplasms / Q000378:metabolism* / Q000473:pathology; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human