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.

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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.

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.

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.