Biopolym. Cell. 2020; 36(3):210-228.
Genomics, Transcriptomics and Proteomics
Sensitivity of MCF-7 cells with differential expression of S6K1 isoforms to the regulatory impact of fibroblasts
1Hotsuliak N. Ya., 1, 2Kravchenko A. O., 1Kosach V. V., 1Tykhonkova I. O., 1Khoruzhenko A. I.
  1. Institute of Molecular Biology and Genetics, NAS of Ukraine
    150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03143
  2. Educational and Scientific Center "Institute of Biology and Medicine",
    Taras Shevchenko National University of Kyiv
    64/13, Volodymyrska Str., Kyiv, Ukraine, 01601


Aim. To investigate the involvement of mTOR/S6K1 cell signaling network, with focus on S6K, in response of tumor cells to regulatory impact of fibroblasts. Methods. Cell culture, including co-cultivation of fibroblasts and tumor cells, immunofluorescence analysis, Western blot analysis, assessment of cell migration by scratch test, and transformation of multicellular spheroid into monolayer cell colony. Results. The present work showed the positive effect of stromal cells on the phosphorylation level of the components of mTOR/S6K1 signaling cascade: p85S6K1, p70S6K1 and mTOR in human breast adenocarcinoma MCF-7 cells. To determine, which of the S6K1 isoforms, p85S6K1, p70S6K1, or p60S6K1, is the most sensitive to the extracellular environment, stable MCF-7 cell lines with edited expression of S6K1 isoforms were used. It was found that selective expression of p60S6K1 led to the changes in morphological features of tumor cells under both two- and three-dimensional culture conditions. These cells also exhibited high levels of focal adhesion kinase (FAK) phosphorylation and large protein content of Zo-1, CD29, CD44 compatible with their high migration potential in the scratch test. Besides, the cells, selectively expressing p60S6K1, were resistant to fibroblast-producing factors and rapamycin. It was also demonstrated that fibroblasts increased tumor cell motility in scratch test and spheroid outspreading assay under co-cultivation conditions in paracrine manner, whereas the direct contact of tumor spheroids with the fibroblast monolayer significantly reduced the velocity of spheroid outspreading. Conclusions. The data obtained indicate that not only the differential expression of S6K1 isoforms in MCF-7 cells but also their ratio are important signaling parameters determining cell survival and response to microenvironment factors.
Keywords: S6K1, migration, tumor microenvironment


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