Browsing by Author "Arcellana-Panlilio, Mayi Y."

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    Regulation of Epithelial Cell Plasticity by a SUMO-TGFβ Signaling Axis
    (2019-12) Chanda, Ayan; Bonni, Shirin; Moorhead, Greg B. G.; Morris, Don G.; Arcellana-Panlilio, Mayi Y.; Godbout, Roseline
    Background Protein post-translational modification by the small ubiquitin-like modifier (SUMO), or SUMOylation, can regulate the stability, subcellular localization or interactome of a protein substrate with key consequences for cellular processes including the Epithelial-Mesenchymal Transition (EMT). The secreted factor Transforming Growth Factor beta (TGFβ) is a potent inducer of EMT in development and homeostasis. Importantly, the ability of TGFβ to induce EMT has been implicated in promoting cancer invasion and metastasis, resistance to chemo/radio therapy and maintenance of cancer stem cells. Interestingly, TGFβ-induced EMT and the SUMO system intersect with important implications for cancer formation and progression, and novel therapeutics identification. The transcriptional coregulator Ski-related novel protein N (SnoN), a negative regulator of TGFβ signaling axis, is a SUMO substrate. Interestingly, Protein Inhibitor of Activated STAT 1 (PIAS1) and Transcriptional Intermediary Factor 1 gamma (TIF1γ) are two distinct SUMO E3 ligases that bind and promote the SUMOylation of SnoN to suppress TGFβ-induced EMT. PIAS1 has been shown to act in a SUMO E3 ligase-dependent manner to suppress the invasion and metastatic growth of breast cancer cells. These results raised the key questions of the significance of the role of the two distinct SUMO E3 ligases PIAS1 and TIF1γ in regulating SnoN SUMOylation and suppressing TGFβ-induced EMT in mammary non-transformed epithelial cells and breast carcinomas. Hypothesis I hypothesize that PIAS1 and TIF1γ cooperate to promote SnoN SUMOylation to suppress EMT by the TGFβ-Smad pathway with potential relevance for breast cancer metastasis and prognosis. Results In this thesis, evidence is provided suggesting that the protein abundance and nuclear localization of PIAS1 act as survival biomarkers in breast cancer patients in a tissue microarray analysis. Accordingly, further results indicate that PIAS1 acts via SUMOylation of SnoN to suppress the invasive growth of triple negative breast cancer cells in 3D-organoid culture. In other studies, findings are provided that support the idea that SnoN promotes the formation of PIAS1-SnoN-TIF1γ multiprotein complex, which promotes SnoN SUMOylation, and its ability to suppress TGFβ-induced EMT in breast epithelial and cancer cells in 3D. Mechanistic studies suggest that SUMOylation promotes SnoN binding to the epigenetic regulators histone deacetylase 1 (HDAC1) and histone acetylase p300 in such a manner that leads to the suppression of EMT induced by the TGFβ-Smad-pathway in non-transformed and cancerous mammary cell-derived 3D organoids. Conclusions The novel findings in this thesis reveal the importance of a SUMO E3 ligase complex comprising PIAS1 and TIF1γ that enhances the SUMOylation of SnoN with impact on specific epigenetic regulators that control EMT in normal and cancer cells. These findings can lead to the discovery of novel biomarkers and therapeutics in breast and potentially other epithelial cell-derived cancers.
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    The Transcription Factor TCF7L2 Acts in An Isoform-Specific Manner to Regulate Epithelial Cell Plasticity: Implications for Breast Cancer Cell Invasiveness and Metastasis
    (2020-06-05) Karve, Kunal; Bonni, Shirin; Riabowol, Karl T.; Senger, Donna L.; Arcellana-Panlilio, Mayi Y.; Goping, Ing Swie
    Alternative splicing of mRNA in a mammalian cell allows generation of complexity in the proteome. The consequences of splicing and its biological significance is poorly understood in development and disease conditions. The research described in thesis investigates the biological significance of alternative splicing of the pre-mRNA of the transcription factor Transcription Factor-7 Like-2 (TCF7L2) into the three major E, S and M isoforms in epithelial and carcinoma cells. Epithelial-mesenchymal transition (EMT) is a fundamental process in development and contributes to pathological conditions including cancer. EMT contributes to cellular plasticity, as it promotes epithelial cells to attain mesenchymal features. The protein TCF7L2 regulates the proliferation and differentiation of epithelial cells, however, whether TCF7L2 acts in an isoform-dependent manner to control EMT had remained largely to be elucidated. Transforming growth factor beta (TGFβ) signaling pathway is a potent inducer of EMT in normal and cancer conditions. How TGFβ-signaling-induced EMT is controlled is the subject of much investigations. The research carried out in this thesis tests the hypothesis that TCF7L2 acts in an isoform-specific manner to differentially regulate TGFβ-induced EMT in epithelial and carcinoma cells. Gain and loss of function studies were done to determine if alterations in the protein abundance of E, M, and S TCF7L2 isoforms affects EMT induction in cells grown in the context of a three-dimensional (3D) culturing system. Our data suggest that while TCF7L2E suppresses, TCF7L2M or S promotes TGFβ-induced EMT in 3D-multicellular structures derived from non-transformed epithelial cells or carcinoma cells. In other studies, we find that TGFβ signaling reduces the proportion of TCF7L2E to TCF7L2M/S protein in cells undergoing EMT. Mechanistically, we find that TCF7L2 operates via TGFβ-Smad signaling to regulate EMT. More recent studies have also identified a specific domain in the C-terminal end of TCF7LE isoforms to be required for its ability to suppress EMT. Collectively, our findings unveil novel isoform-specific functions for the transcription factor TCF7L2 and provide novel links between TCF7L2 and TGFβ signaling in the control of EMT and potentially cancer progression.