Personalized medicine and development of targeted therapies: the upcoming challenge for diagnostic molecular pathology. A review

Abstract

Due to continuous technical developments and new insights into the high complexity of many diseases, molecular pathology is a rapidly growing field gaining center stage in the clinical management of tumors as well as in the pharmaceutical development of new anti-cancer drugs. The application of novel compounds in clinical trials has revealed promising results; however, the current diagnostic procedures available for determining which patients will primarily benefit from rational tumor therapy are insufficient. To read a patient's tissue as "deeply" as possible, in the future, gaining information on the morphology and on genetic, proteomic, and epigenetic alterations will be the upcoming task of surgical pathologists experienced in molecular diagnostics to provide the clinicians with information relevant for an individualized medicine. Among the different high-throughput technologies, DNA microarrays are now the first array approach close to enter routine diagnostics. Technically advanced and well-established microarray platforms can nowadays be evaluated by distinct bioinformatic tools capable of identifying both novel genes associated with disease development and clusters of genes predicting clinical outcome of an individual tumor. The automatic, highly parallel analysis of proteins and complex proteins lysates for early detection of cancers such as breast, prostate and ovary as proteomic patterns in the serum also appears at the horizon. In addition, an improved analysis of tumor samples via antibody or reverse-phase protein arrays is likely to provide the pathologist in the future with information about activated oncogenic signaling pathways and other cell functions, such as drug response or the potential to metastasize. While expression microarrays and proteomic analysis rely on relatively unstable material incompatible with paraffin-embedded tissue samples, an investigation of DNA methylation using specialized high-throughput platforms has revealed the potential of being used in future diagnostics. Each of these approaches on its own might not suffice to extract all information required for an efficient individualized diagnostics. Therefore, a "multiplex approach" combining the different biological levels DNA, RNA, and protein, may be necessary to functionally classify malignant tumors. This appears to become a major challenge for diagnostic pathologists.