A specific gene expression signature characterizes metastatic potential in clear cell renal cell carcinoma.

PURPOSE: The discovery of metastasis markers in clear cell renal cell carcinoma is of critical importance to define individual metastatic risk and select patients for new targeted therapies. We identified potential biomarkers for metastatic clear cell renal cell carcinoma by gene expression analysis. MATERIALS AND METHODS: We performed transcriptional profiling of 16 primary metastatic and 18 nonmetastatic clear cell renal cell carcinomas with PIQOR™ microarrays. Differentially expressed genes were validated by quantitative real-time polymerase chain reaction. RESULTS: Genes discriminating between metastatic and nonmetastatic tumors were identified at q <0.001 by significance analysis of microarrays. The metastatic signature contained 127 transcripts. In metastatic samples a greater than 4-fold decrease in expression was detected for the genes CD151 and IKBA (t/F statistic p <0.0001) while the genes MMP16, B7-H1, BCL2L2 and FRA2 showed greater than 4-fold increase of expression in metastatic primary tumors (p <0.0001). Quantitative real-time polymerase chain reaction revealed significant differences in expression among all metastatic tumors, including synchronously and metachronously metastasized tumors, and nonmetastatic tumors for FRA2 (p = 0.032) and CD151 (p = 0.005). In addition, the genes B7-H1 (p = 0.040), FRA2 (p = 0.035), CD151 (p = 0.004) and BCL2L2 (p = 0.035) showed significantly higher expression in early metastasized than in nonmetastatic tumor samples. Different B7-H1 (p = 0.002) and BCL2L2 (p = 0.007) expression levels were found in samples with late metastasis compared to those in synchronously metastasized tumors. CONCLUSIONS: We determined a metastatic signature of clear cell renal cell carcinoma by microarray analysis. Our data provide the possibility of defining the metastatic potential of primary clear cell renal cell carcinoma based on a select number of genes even in a localized situation.

Entrainment elicits period aftereffects in Neurospora crassa.

Circadian clocks continue to oscillate in constant conditions with their own period (tau) and entrain to a cyclic environment by adjusting their intrinsic period to that of the zeitgeber. When circadian clocks are released from entrained to constant conditions, the tau of their initial free-run often depends on the nature of the prior zeitgeber. These postentrainment effects on period (tau-aftereffects) have predominantly been reported for animals but, so far, not fungi. The authors therefore investigated tau aftereffects in the classic circadian model system Neurospora crassa. The standard laboratory strain frq+, the short-period mutant frq(1), and the long-period mutant frq(7) were entrained to 11 different photoperiods in a 24-h day (2-22 h) and to zeitgebers with six different T (16-26 h), and then released to constant darkness. tau-Aftereffects in response to different photoperiods correlated weakly with prior photoperiod in frq+ and were unsystematic in both period mutant strains. Strength and direction of the tau-aftereffect in zeitgeber cycles with different T depended on their length and on the strain, showing a negative correlation with zeitgeber length in frq+ and positive correlations in frq(1) and frq(7). It has been proposed that tau-aftereffects are based on interactions of oscillators within a cellular network. The present findings in Neurospora, which grows as a syncytium, suggest that tau-aftereffects also exist in circadian systems based on multioscillatory networks organized at the molecular level.

Immune escape for renal cell carcinoma: CD70 mediates apoptosis in lymphocytes.

Tumors can escape immune recognition and destruction through the induction of apoptosis in lymphocytes. Although renal cell carcinoma (RCC) is able to prevent immune recognition, only a few genes (such as FasL) that are relevant for RCC immune escape have been identified so far. We have previously shown that some apoptosis-inducing genes are overexpressed in RCC. We hypothesized that these genes could be part of the immune-escape strategy of these tumors. Here we report that CD70, a cytokine overexpressed in RCC, promotes lymphocyte apoptosis through interaction with its receptor CD27 and with the intracellular receptor-binding protein SIVA. Apoptosis increased after cocultivating lymphocytes with the RCC cell lines A498 and CAKI2. The addition of recombinant soluble CD70 to both native lymphocytes and a T-cell cell line resulted in increased lymphocyte apoptosis as well. Furthermore, induced apoptosis could be partially blocked with anti-CD27 and anti-CD70 antibodies. Our results strongly indicate a role for CD70 and CD27 receptor in lymphocyte apoptosis within the tumor environment. Apoptosis mediated by exposure to the CD70 secreted by tumor cells may contribute to the failure of RCC patients to develop an effective lymphocyte-mediated antitumor response.

Comparative transcriptional and functional profiling of clear cell and papillary renal cell carcinoma.

Renal cell carcinoma (RCC) is known to effectively prevent immune recognition. However, little is known about the mechanisms that underlie this phenomenon. Thus, the identification of immunogenic molecules associated with RCC and the elucidation of the corresponding signaling pathways are crucial to the development of effective treatments. We performed transcriptional and functional profiling with cDNA microarrays (1070 cDNA probes) on a total of 17 RCCs, 11 clear cell and 6 papillary, and on corresponding normal tissue. Samples were clustered based on their expression profiles. We found a total of 45 genes to be regulated equally by both tumor types compared to the normal tissue. A set of 13 differentially expressed genes was identified between the examined tumor subtypes. Functional analysis was performed for both gene sets and showed a significant enrichment of cell surface genes regulated in both tumor subtypes. Within these we found five surface marker genes to be upregulated (TNFRSF10B, CD70, TNFR1, PDGFRB, and BAFF) which are involved in immune responses via the regulation of lymphocytes and can also induce apoptosis. Their overexpression in both tumor subtypes suggests a possible involvement in the immune escape strategies of RCC. The combination of transcriptional and functional profiling revealed potential target molecules for novel therapy strategies that must be studied in more detail.

Identification of CD70 as a diagnostic biomarker for clear cell renal cell carcinoma by gene expression profiling, real-time RT-PCR and immunohistochemistry.

The underlying molecular mechanisms of renal cell carcinoma (RCC) are poorly understood and more reliable markers for early diagnosis are needed. Hence, alternative strategies for biomarker discovery with appropriate validation technologies have to be performed. To elucidate genesis and progression of RCC we used high parallel chip based gene expression profiling comparing normal and tumour tissues. We compared corresponding control and tumour tissue samples from 10 patients with clear cell RCC. We isolated RNA from histologically well characterised tissue sections and performed reverse transcription, labelling and linear RNA amplification. Samples were hybridised on microarrays containing 642 human cDNAs. Of the 352 differentially expressed genes found, CD70 and FRA2 were selected for further evaluation by real-time RT-PCR. The analysis all showed a high potential to discriminate between normal and tumour tissue. Moreover, increased CD70 mRNA expression in tumour cells could be correlated to its expression at the protein level. Immunohistochemistry (IHC) showed very strong expression of CD70 in all tumour samples but no expression in adjacent normal kidney tissue. With our combined approach we were able to identify CD70 as a new marker for RCC, which may be useful in the future for improved immunohistochemical diagnosis.

CD70: a new tumor specific biomarker for renal cell carcinoma.

PURPOSE: To date there have been no specific tumor markers available for the differential diagnosis of renal cell carcinoma (RCC). In an earlier study we identified high RNA expression of CD70 in clear cell RCC. CD70 is a type II transmembrane protein belonging to the tumor necrosis factor family. It represents the ligand for CD27, a glycosylated transmembrane protein of the tumor necrosis factor receptor family. To our knowledge the function of CD70 in solid tumors is not known. In the current study we analyzed CD70 protein expression in different RCC subtypes. MATERIALS AND METHODS: A total of 68 tumor samples of different histopathological subtypes were investigated by immunochemistry, including 41 clear cell, 19 papillary and 5 chromophobe RCCs, and 3 oncocytomas as well as their normal tissue counterparts. Immunochemistry was performed on frozen tissue samples using monoclonal antibody against CD70. RESULTS: None of the normal kidney tissues showed CD70 expression. In contrast, all clear cell RCCs expressed CD70 at a high level. Positive immunostaining was observed in 1 papillary (5%) and in 1 chromophobe (20%) RCC. Five papillary tumor samples (26%) showed focal staining in less than 5% of cells. All other samples were negative for CD70. CONCLUSIONS: Our study identified CD70 as a new specific tumor marker for clear cell RCC. This new marker can be used for differential diagnosis in cases of uncertain histological classification. The function of this protein in tumorigenesis and its use as a diagnostic marker in serum and urine or as a therapeutic tool must be investigated in further studies.