Proteomics in human disease: Cancer, heart and infectious diseases

In recent years, genomics has increased the understanding of many diseases. Proteomics is a rapidly growing research area that encompasses both genetic and environmental factors. The protein composition represents the functional status of a biological compartment. The five approaches presented here resulted in the detection of disease‐associated proteins. Calgranulin B was upregulated in colorectal cancer, and hepatoma‐derived aldose reductase‐like protein was reexpressed in a rat model during hepatocarcinogenesis. In these two investigations, attention was focused on one protein, obviously differing in amount, directly after two‐dimensional electrophoresis (2‐DE). Additional methods, such as enzyme activity measurements and immunohistochemistry, confirmed the disease association of the two candidates resulting from 2‐DE subtractive analysis. The following three investigations take advantage of the holistic potential of the 2‐DE approach. The comparison of 2‐DE patterns from dilated cardiomyopathy patients with those of controls revealed 25 statistically significant intensity differences, from which 12 were identified by amino acid analysis, Edman degradation or matrix‐assisted laser desorption/ionization‐mass spectrometry (MALDI‐MS). A human myocardial 2‐DE database was constructed, containing 3300 protein spots and 150 identified protein species. The number of identified proteins was limited by the capacity of our group, rather than by the principle of feasibility. Another field where proteomics proves to be a valuable tool in identifying proteins of importance for diagnosis is proteome analysis of pathogenic microorganisms such as Borrelia burgdorferi (Lyme disease) and Toxoplasma gondii (toxoplasmosis). Sera from patients with early or late symptoms of Lyme borreliosis contained antibodies of various classes against about 80 antigens each, containing the already described antigens OspA, B and C, flagellin, p83/100, and p39. Similarly, antibody reactivity to seven different marker antigens of T. gondii allowed differentiation between acute and latent toxoplasmosis, an important diagnostic tool in both pregnancy and immunosuppressed patients.