Constitutive activation of hypoxia-inducible genes related to overexpression of hypoxia-inducible factor-1alpha in clear cell renal carcinomas.

The transcription factor hypoxia-inducible factor (HIF)-1 is an important mediator of hypoxic adaptation of tumor cells and controls several genes that have been implicated in tumor growth. Oxygen-dependent degradation of HIF-1alpha, the regulatory subunit, requires binding to the von Hippel Lindau (VHL) protein. Because functional inactivation of the VHL tumor suppressor gene occurs in up to 70% of clear cell renal carcinomas, we investigated whether this results in overexpression of HIF-1alpha and its target genes. Immunoblotting revealed increased expression of HIF-1alpha in 24 of 32 (75%) clear cell renal carcinomas but only 3 of 8 non-clear cell renal tumors. Somatic mutations of the VHL gene were detected only in clear cell renal carcinomas that overexpressed HIF-1alpha. None of the HIF-1alpha-negative tumors displayed a VHL mutation. The level of HIF-1alpha mRNA was not different between tumors and adjacent kidney tissue. Immunohistochemistry revealed distinct patterns of nuclear staining for HIF-1alpha, depending on histological type and overall abundance of HIF-1alpha. In those clear cell renal carcinomas that showed increased expression on immunoblots, HIF-1alpha was expressed in almost all cells. In the remaining clear cell and in non-clear cell tumors, staining was focal; these different patterns thus were compatible with genetic stabilization in contrast to microenvironmental stimulation of HIF-1alpha as the primary mechanism. The mRNA expression of two known target genes of HIF-1alpha, vascular endothelial growth factor and glucose transporter 1, increased progressively with increasing amounts of HIF-1alpha in tumor extracts. In addition, glucose transporter 1 protein levels correlated with HIF-1alpha abundance. In conclusion, the data provide in vivo evidence for a constitutive up-regulation of HIF-1alpha in the majority of clear cell renal carcinomas, which leads to more widespread accumulation of this transcription factor than hypoxic stimulation. These observations are most likely linked to functional inactivation of the VHL gene product. Increased expression of HIF-1alpha is associated with alterations in gene expression patterns that are likely to contribute to tumor phenotype and progression.

Cytomegalovirus infection in transplant recipients. The role of tumor necrosis factor.

Human cytomegalovirus (CMV) infection is an important cause of morbidity and mortality in transplant recipients. CMV infection commonly results from the reactivation of a latent infection. Using a set of monoclonal anti-CMV antibodies, we found CMV antigen expression in peripheral blood mononuclear cells (PBMNC), particularly in monocytes, in 312 of 816 samples from 190 allograft recipients. The detection of CMV-IE antigens and CMV-IE DNA in PBMNC indicates that positive cells may represent truly infected cells. The relation between increased cytokine plasma levels (particularly following treatment by pan-T cell antibodies) and the appearance of CMV antigens in PBMNC suggests that cytokines may play an important role in the reversal of CMV latency. This hypothesis is supported by our finding that tumor necrosis factor-alpha (TNF) is able to stimulate the activity of the CMV-IE enhancer/promoter region in the human monocytic cell line, HL-60. The interleukins 1, 2, 3, 4, 6, 8 and 10; transforming growth factor-beta; interferongamma; and granulocyte/macrophage colony-stimulating factor did not show any enhancing effect on the CMV promoter activity. Thus, TNF-alpha seems to play a key role in regulating the balance between latency and reactivation of CMV infection. Inhibition of TNF-alpha release or action may be an alternative strategy for preventing CMV-associated morbidity in allograft recipients.

[p53 in urogenital tumors:analysis of expression and mutation]. / p53 in urogenitalen Tumoren: Eine Expressions- und Mutationsanalyse.

DNA and paraffin material of more than 100 tumors of prostate, bladder and female genital organs were analyzed for p53 aberrations and compared with normal tissues by immunohistochemistry, PCR of p53 exons 5-8 and TGGE. While normal tissues, precancerous and borderline lesions, and well differentiated carcinomas usually showed wild type p53 and negative immunostaining, high grade and/or high stage carcinomas often revealed mutant p53 (rate of mutation in exon 8 >> 7 >> 6 >> 5) and/or p53 accumulation. Accumulation of p53 protein in the absence of detectable mutant p53 was recognized more often in prostate cancer than in any other tumor examined. Although p53 aberration probably represents a late molecular event in cancerogenesis, its detection may be of clinical interest as genetic footprint in recurrent and metastatic disease.