The ING tumor suppressor genes and their specific role in the pathogenesis of renal cell carcinoma

Abstract

10045 Background: The inhibitor of growth (ING) family of tumor suppressor genes is involved in cell cycle arrest, regulation of gene transcription as well as DNA repair. p33ING1b plays an important role in the pathogenesis of certain carcinomas by modulation of p53. We analyzed p33ING1b and p29ING4 gene expression together with specific immune responses in patients with renal cell carcinoma (n=50) at different tumor stages. Methods: Peripheral blood lymphocytes (PBMCs) from patients (Robson stage I-IV) were stimulated with pools of synthetic overlapping peptides of the p33ING1b or p29ING4 sequences encompassing the full length sequence of these two genes. PBMCs and tumor specimens were further characterized (ELISPOT, FACS, immunohistology, Real Time PCR). Results: T cells from stage I/II patients expressed higher IL-10 (n=5) than IFN-γ (n=5) levels in response to p29ING4 peptides. However, distinct residues of peptides were found that induced a Th2 type response (IL 10, n=5) in stage III/IV patients. Interestingly, distinct residues induced a Th1 (IFN-γ, n=5) response in the latter patients. Lymphocytes stimulated with p33ING1b peptide pools expressed IFN-γ as well as IL-10, independently from the tumor stage. Remarkably, immunohistochemical staining as well as Real Time PCR analysis of tumor specimens revealed higher numbers of CD4/CD8, CD4/CD25, CD4/Foxp3, CD4/CTLA-4, and NK cells as well as IL-10, IFN-γ, and Annexin V expression at the tumor site of stage I/II patients than later tumor stages. However, stronger staining and gene expression of p33ING1b as well as p29ING4 together with a reduced staining and expression of p53 was observed in stage III/IV patients. A correlation between the stage and the grading of the tumor was not present. Conclusions: In order to exert its function as a growth arrest and apoptosis inducing protein, p53 needs to interact with other tumor suppressor genes like the ING gene family. Subsequently, the loss of ING function may be a potential mechanism for the inactivation of p53 function in renal cell carcinoma. The results of this study may provide the basis for immune therapeutical strategies (induction of apoptosis or of a Th1 response using a vaccination protocol in particular with p29ING4 in the early stage of the disease) in renal cell carcinoma. No significant financial relationships to disclose.