RESUMO
BACKGROUND: Thermal stability signatures of complex molecular interactions in biological fluids can be measured using differential scanning calorimetry (DSC). Evaluating the thermal stability of plasma proteomes offers a method of producing a disease-specific "signature" (thermogram) in neoplastic and autoimmune diseases. OBJECTIVE: The authors describe the use of DSC with human brain tumor tissue to create unique thermograms for correlation with histological tumor classification. METHODS: Primary brain tumors were classified according to the World Health Organization classification. Tumor samples were digested and assayed by a DSC calorimeter. Experimental thermograms were background subtracted and normalized to the total area of transitions to exclude concentration effects. The resulting thermograms were analyzed by applying 2-state, scaled, Gaussian distributions. RESULTS: Differences in glioma-specific signatures are described by using calculated parameters at transitions that are characterized, in the equilibrium approximation, by a melting temperature (Tm), an apparent enthalpy change (ΔH), and a scaling factor related to the relative abundance of the materials denatured in the transition (Aw). Thermogram signatures of glioblastoma multiforme and low-grade astrocytomas were differentiated by calculated values of Aw3 and Tm4, those of glioblastoma multiforme and oligodendrogliomas were differentiated by Aw2, ΔH2, ΔH4, and Tm4, and those of low-grade astrocytomas and oligodendroglioma were differentiated by Aw4. CONCLUSION: Our preliminary results suggest that solid brain tumors exhibit specific thermogram profiles that are distinguishable among glioma grades. We anticipate that our results will form the conceptual base of a novel diagnostic assay based on tissue thermograms as a complement to currently used histological analysis.