Thermal Stability of M1 Sarcoma in Rat Tissue: A Differential Scanning Calorimetry Study

Abstract

Background: Clinical studies indicate that epithelial tissue is the source of over 90% of human cancers. Investigation of this phenomenon using the M1 rat sarcoma model and a new, rapid differential scanning calorimetry (DSC) method applied to milligram quantities of biopsied tissue enables further application of this approach for sarcoma diagnosis within 50-60 minutes. When used in combination with other diagnostic methods, this technique may facilitate timely diagnosis and improve treatment outcomes. Objectives: (i) To evaluate the contribution of collagen – the major structural protein – and collagen fibrils to tissue thermal stability using a rat M1 sarcoma model based on DSC measurements; (ii) To determine the degree of disease progression based on differences in the thermal stability of postoperative M1 sarcoma tissue at 10, 20, and 30 days after resection compared with healthy tissue obtained from areas distant from the sarcoma. Methods: In each experiment, tissue from three albino female rats was used (nine animals in total). Tumor tissue excised 10, 20, and 34 days after transplantation, together with healthy tissue obtained from sites distant from the tumor, was analyzed at 10-15 mg of fresh tissue using a highly sensitive differential scanning calorimeter (DSC). The instrument, designed for the study of complex biological systems, allows measurement of tissue denaturation with an accuracy of ±0.1 °C. This approach enables precise determination of temperature-induced structural transitions in biomacromolecules and their complexes. Results: Differential scanning calorimetry (DSC) was performed on fresh postoperative rat tissues collected 10, 20, and 34 days after M1 sarcoma transplantation. Tumor volumes at these time points were 1.0±0.25 cm³, 10.05±2.4 cm³, and 37.5±4.2 cm³, respectively. Tissue samples were obtained from dense regions of M1 sarcoma and from healthy skin at sites distant from the tumor. In addition, healthy tissue, sarcoma tissue, and collagen fibrils isolated from healthy tissue were analyzed at different water contents. Conclusions: DSC measurements showed that: The thermal stability of M1 sarcoma connective tissue was reduced by 2-3°C relative to normal tissue at early stages of the disease, increasing to approximately 5°C with further tumor growth. These findings suggest that such data may be used for tumor diagnosis at different stages of sarcoma progression, provided that sufficient experimental data are accumulated. Based on DSC measurements of native collagen fibrils isolated from healthy tissue, whole fresh healthy rat tissue, and fresh M1 sarcoma tissue at varying water contents, it is concluded that the reduced thermal stability of the connective tissue in M1 sarcoma compared with healthy tissue is associated with collagen.