Role of P53 and MDM2 in treatment response of human germ cell tumors.
OBJECTIVE
Testicular germ cell tumors (TGCTs) of adolescents and adults are very sensitive to systemic treatment. The exquisite chemosensitivity of these cancers has been attributed to a high level of wild-type P53.


METHODS
To clarify the role of P53 in treatment sensitivity and resistance of TGCTs, we performed immunohistochemistry and Western blotting analysis on a series of 39 fresh-frozen primary TGCTs before therapy (unselected series). In a series of formalin-fixed paraffin-embedded TGCTs of patients with fully documented clinical course, including treatment-sensitive (n = 17) and -resistant (n = 18) tumors, P53 status was assessed by immunohistochemistry and mutation analysis. In addition, the involvement of MDM2, a P53 antagonist, was investigated by immunohistochemistry, reverse transcriptase polymerase chain reaction, and in situ hybridization.


RESULTS
Immunohistochemistry demonstrated absence of staining for P53 in 36%, 41%, and 17% of the unselected, responding, and nonresponding TGCTs, respectively. Of the positive TGCTs, most tumors, ie, 49%, 41%, and 33%, showed 1% to 10% positive nuclei. This overall low level of P53 was confirmed by Western blotting. Mutation analysis revealed only one silent P53 mutation in one of the responding patients. All embryonal carcinomas were homogeneously positive for MDM2, encoded by the full length mRNA, while a heterogeneous pattern was found for the other histologic components. Amplification of MDM2 was detected in one out of 12 embryonal carcinomas.


CONCLUSIONS
Although our results are in line with previous findings of the presence of wild-type P53 in TGCTs, they show that a high level of P53 does not relate directly to treatment sensitivity of these tumors, and inactivation of P53 is not a common event in the development of cisplatin resistance.
Kersemaekers
Anne-Marie F
AM
Department of Pathology/Laboratory for Experimental Patho-Oncology, University Hospital Rotterdam/Daniel, Josephine Nefkens Institute, Erasmus University Rotterdam, Rotterdam, The Netherlands.
Mayer
Frank
F
Molier
Michel
M
van Weeren
Pascale C
PC
Oosterhuis
J Wolter
JW
Bokemeyer
Carsten
C
Looijenga
Leendert H J
LH
D015153:Blotting, Western; D004252:DNA Mutational Analysis; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D009687:Nuclear Proteins; D018807:Polymorphism, Single-Stranded Conformational; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018239:Seminoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013736:Testicular Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2