Assessment of Residual VHL Function in Tumors - Can it Predict the Patients' Individual Course of Disease?

Overview

The investigators aim to analyze tumors from vHL patients who have different courses of disease and different types of VHL gene alterations to characterize which types of genetic alterations the tumors contain and how these alterations affect the tumor cells' behavior on a molecular level. The investigators will then compare these observations to vHL disease outcome in patients and families. It is already known that most vHL tumors develop when both copies of the VHL gene in a cell are inactivated. The first copy is inactivated in all the person's cells from birth ("first hit"), leaving just one functional copy. A tumor can develop from cells where the second copy is also inactivated ("second hit"). So far, only the molecular consequences of the first hit have been investigated. It is our hypothesis that both the first and second hits in combination have consequences for tumor development and clinical outcome. The investigators will include tumors from patients with different disease courses and different types of "first hits" and analyse the tumors' DNA in order to find correlations between the first and second hits and patients' and families' medical histories. The investigators hereby hope to give new insights into how vHL tumors grow and which genetic factors influence tumor development. These results will contribute to the current knowledge of vHL and help us get one step closer to be able to predict an individual's tumor risks and need for surveillance.

In vHL tumors from patients with different phenotypes and different genetic backgrounds, the investigators aim to assess both the nature of germline and somatic VHL mutations along with the total residual VHL protein (pVHL) activity in tumor cells and evaluate association to disease outcome in patients and families. vHL tumor development follows Knudson's "two-hit-mode": patients are born with a germline mutation in one copy of their VHL gene in all the cells of the body - "the first hit". Somatic mutation in the other copy of the VHL gene - "the second hit" - initiates tumor development. Pheno-genotype correlations are well known in vHL, but have so far been explained exclusively by the nature of the germline mutation (the first hit). It is the investigators' hypothesis that it is the total residual activity of the protein (pVHL) present in the tumor after both first and second hit, which decides each tumor's destiny. The investigators will apply Sanger sequencing, MLPA (and multiplex ligation dependent probe amplification), LOH (Loss of heterogeneity) analysis, methylation assays, FISH (Fluorescence In Situ Hybridization), and immunohistochemistry to characterize the germline and somatic mutations, determine presence of mRNA and pVHL, and assess residual VHL activity in each tumor. All these methods are already established in our laboratory. The results will give deeper insight to vHL tumorigenesis and pave the road to future individual prediction of each patient´s course of disease and need for surveillance.