[Genetic tests in oncology practice with emphasis on the RET oncogene and VHL tumor suppressor gene]

Molecular oncogenetics is the study of two distinct gene classes participating in the pathogenesis of malignant diseases: proto-oncogenes and tumour suppressors genes. Stepwise alterations in their structure are the basis of malignancy. Structural abnormalities range widely: gross genetic rearrangements including insertions, deletions, gene amplifications and single nucleotide deleotide deletions and substitutions. These gene alterations are determined by gene testing that increasingly are part of clinical diagnosis. Among many applications of oncogene testing is detection of hereditary forms of malignant disease with outstanding prophylactic and therapeutic importance. Along this line, gene testing provided for effective prevention of specific hereditary tumour types. Analysis of hereditary pheochromocytoma two gene tests are established: detection of multiple endocrine neoplasia type 2 (MEN 2) using mutational analysis of RET gene and detection of von Hippel-Lindau syndrome using mutational analysis of VHL gene. These genes were characterized about a decade ago and their structure determined in detail. Numerous studies focus on expression of these genes in different tissues and the function of respective proteins. In extensive epidemiology the following facts are established: hereditary mutations in the RET gene in > 92% of cases with MEN 2 syndrome while in patients with von Hippel-Lindau syndrome hereditary mutations were detected in VHL gene in > 95% of cases. Such a high genotype--phenotype correlation forms the basis for clinical applications. Gene testing in oncology offers numerous advantages. If a patient with pheochromocytoma presents with hereditary mutation in the RET or VHL gene, family gene testing is recommended. Family member with hereditary gene mutation is indicative of the risk level of nearly 100% for MEN 2 or von Hippel-Lindau syndrome. In such cases surgery is warranted (e.g. in MEN 2 total thyroidectomy by the age of (6). Negative findings in this type of gene testing relive family members from enormous psychological tension and provide them with normal family planning. There are many reasons to believe that this type of gene testing is the foundation of diagnosis for the 3rd millennium. Namely, results of gene testing may provide basis for effective prevention: mutations causative for a disease may be detected, presymptomatically and prenatally; the analysis requires only couple of mL of blood, and mutational status is determined only once in a lifetime.