Tykhonkova I. Search and characterization of tumor-associated antigens from thyroid cancer and melanoma

The repertoire of tumor associated antigens has been determined at human thyroid tumor and melanoma in the course of immunoscreening by SEREX method. Total of 55 immunopositive clones being the products of 33 genes was determined among which 29 in thyroid tumor and 4 in melanoma. The levels of autoantibodies against three of them - Ki-67 antigen, mitochondrial ATPase and repressor protein - are elevated in the patients with all cancer types investigated as it have been shown by heterological screening. This finding makes their perspective as markers of malignancies. Ki-67 fragment have been cloned and purified, in the course of ELISA screening it have been shown that in the sera of patients bearing melanoma, thyroid, breast and lung cancers levels of autoantibodies against this protein were increased compared to healthy donors. Functional investigations of Ki-67 fragment revealed its ability to interact with DNAs of pro- and eukaryotic origin in vitro. Poly- and monoclonal antibodies against Ki-67 fragment obtained in the present work may be used to distinguish phases of cell cycle as well as for determination of tissue mitotical indexes.