The role of soluble Her2 (sHer2) in Her2-dependent oncogenicity and in conditioning the response to HER2-mediated therapies has remained elusive. In such studies, the concentrations level of sHer2 and alternative splicing form(s) of Her2 in oncological patients are in the focus of attention. Both the oligomeric status of sHer2 generated by tumor cells and its possible prognostic value have not been examined so far. In this study we have tried to analyze the oligomeric status of sHer2 in breast cancer patients.
Recombinant human sHer2 produced by HEK 293 and sHer2 isolated from the supernatant of the primary tumor cell culture from breast cancer patients was used in the experiments. The oligomeric status was estimated using the method of gel-filtration chromatography and electrophoresis. The stability of Her2 was determined by the change in the protein secondary structure under variation of temperature and pH values by means of CD spectroscopy. The inhibitory activity of sHer2 was analyzed in tests with Her2-expressing cell cultures. The content of sHer2 in the supernatant of primary tumor cell cultures from breast cancer patients was determined using the sandwich ELISA. Amplification of the HER2 gene in the primary tumor cells was verified employing the FISH.
The electrophoretic and chromatographic analyses show that sHer2 is present mostly as a tetramer capable of inhibiting proliferation of Her2-expressing cell cultures. sHer2 is stable upon heating the solution to 50Â°C in the pH range from 7 to 9. It should be noted that the high level of sHer2 is found in supernatants of the primary tumor cell cultures from breast cancer patients not only with amplified Her, but also in triple negative breast cancer samples (ER - 0; PR - 0; Her-2/neu negative (0 + 1); Ki 67 - 27 - 87%).
In our opinion, the results obtained show that the oligomeric status of sHer2 can be regarded as a prognostic factor. This work was supported by the grant from Ministry of Education and Science of the Russian Federation (№ 14.604.21.0025, ID RFMEFI60414X0025).
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All authors have declared no conflicts of interest.