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Browsing by Subject "cell proliferation"

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  • Metformin induces senescence-like proliferation arrest in MYC-high triple-negative breast cancer cell lines 
    Savelius, Mariel (2020)
    Breast cancer remains as the leading cause of cancer deaths among women. Triple-negative breast cancer (TNBC) is one of the most aggressive breast cancer subtypes and lacks targetable receptors, consequently, cannot be treated with current hormone of anti-HER2 targeting therapies. Thus, there is a need for discovering novel and well-tolerated therapies. MYC is a proto-oncogene and a transcription factor, that is frequently amplified and overexpressed in breast cancers. MYC is involved in many cellular processes promoting cell proliferation, however, overexpression of MYC can also sensitize cells to replicative stress and apoptotic cell death. In our previous studies we have shown that pharmacological activation of AMPK, a cellular energy sensor, synergises with Bcl-2 family inhibitors, such as navitoclax and venetoclax, and activates MYC-dependent apoptosis in breast cancer cell lines, transgenic mouse models of MYC-dependent mammary tumorigenesis and in MYC-high patient-derived explant cultures (PDECs). In subsequent study we observed, that indirect AMPK activator metformin alone inhibited tumor growth in vivo, but did not induce apoptosis in mouse tumors or in PDECs. Metformin, a type II diabetes mellitus drug, has shown anti-cancer effects in some population studies and is under investigation for a cancer therapies, however the whole mechanism of action in cancer is still not well-known. To elucidate metformin’s effects on MYC overexpressing triple-negative breast cancer cells, I will present, that metformin has anti-proliferative effects and show that long term metformin treatment induces senescence biomarkers in MYC-high TNBC breast cancer cell lines. To study metformin's short and long-term anti-proliferative activity, cell proliferation during and after drug treatment was investigated, which showed, that metformin’s effects do not seem to persist long after drug withdrawal. In conclusion, the key observation of this thesis was, that metformin does inhibit the proliferation of MYC overexpressing cancer cells and presents a senescence phenotype that possibly can be exploited to find new targeted therapies for triple-negative breast cancer patients.
  • The role of polarity proteins Par6B and Par6G in cell proliferation 
    Virkunen, Ekaterina (2018)
    The majority of cancers, such as breast cancer, originate from epithelial structures. Highly organized epithelial tissues are comprised of cells which manifest apico-basal polarization. Factors regulating apico-basal polarity and epithelial integrity are often observed deregulated in cancer cells and loss of polarity is often observed in tumors. However, the importance and the specific role of epithelial integrity regulators in tumorigenesis are still not fully defined. This study shows that the key regulators of epithelial cell polarity Par6B and Par6G proteins have a role in the restriction of cell proliferation in mammary epithelial cell lines. Using the shRNA silencing approach, downregulation of PARD6B and PARD6G in the cells lead to the impediment of the cell-cycle exit, verified in proliferation suppressive conditions in which cells normally would enter quiescence. Par6 proteins were shown to regulate cell proliferation via the canonical PI3K/Akt pathway, which is one of the most commonly deregulated cell proliferation promoting pathways in cancer cells. The results demonstrate the unknown function of Par6B and Par6G proteins as cell proliferation regulators and a previously unrecognized relation between Par6 proteins and PI3K/Akt pathway. However, the detailed interaction between Par6 proteins and the PI3K/Akt pathway ought to be investigated further. In addition, the results revealed that Par6 proteins have different effects on cell proliferation suggesting biological differences between Par6 proteins and that certainly bears further investigation. In conclusion, the study presents a previously unknown connection between epithelial integrity regulators and cancer-relevant cell proliferation promoting pathways, which may provide new targets for therapeutic intervention in the future.

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