Titolo della tesi: Exploring the anti-cancer effect of FTO inhibition in Chronic Myeloid Leukemia
In the last decades, the study of RNA modifications has become one of the most interesting and fascinating topics in the field of molecular biology. Chemical modifications occurring in the RNA molecules play essential roles in gene expression regulation. Nowadays, more than 160 different RNA modifications have been described in coding and non-coding transcripts. Between all these modifications, N6-methyladenosine, or m6A, is the most prevalent internal chemical modification found in mRNAs. M6A is involved in the control of every aspect of the post-transcriptional regulation of these molecules, influencing processes such as pre-mRNA splicing, nuclear export, translation, and stability. Similar to other chemical modifications that occur in other molecules like DNA and proteins, m6A is a reversible and dynamic since it is deposited by writers, removed by erasers, and recognized by reader proteins. Therefore, alterations in global m6A levels in the transcriptome have been associated with multiple biological processes and human diseases. Particularly in cancer, changes in the m6A pattern are commonly associated with the altered expression of the proteins involved in cell metabolism, proliferation, and apoptosis, affecting relevant processes from the clinical point of view, like drug resistance in multiple cancer types.
Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm characterized by the accumulation of mature myeloid cells in the blood. The molecular signature that characterizes this disease is the fusion protein BCR-ABL1, a constitutively active tyrosine kinase that promotes growth and replication through different downstream signalling pathways. However, despite advances in our
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Dottorato di ricerca in Genetica e Biologia Molecolare
understanding of signal transduction, the role of m6A in CML is still not known in detail.
Here we investigated the role of FTO m6A demethylase in CML showing evidence that targeting FTO with a specific chemical inhibitor impacts different but interconnected layers of molecular regulation. We found that in CML, FTO localizes in the cytoplasm where it catalyses essentially m6A demethylation in mRNAs species. FTO cytoplasmic activity is essential for CML proliferation and cell cycle progression. We demonstrated that increasing m6A global levels in mRNAs by inhibiting FTO activity, impairs ER stress and downregulates the Unfolded Protein Response (UPR), which are biological processes essential for CML progression. In particular, FTO inhibition downregulates mRNA and protein levels of the master regulator of the UPR, HSPA5 (also known as BiP or GRP78). On the contrary, inhibition of the m6A methyltransferase METTL3 showed opposite effect in HSPA5 protein levels. Therein, our results open a new window to target UPR by modulating m6A. Moreover, we identified a global increase in the expression levels of the genes encoding for the four histone cores as well as for the histone linker upon FTO inhibition, showing a possible interconnection between m6A global changes and heterochromatin formation, hallmark of gene silencing. In conclusion, our work entails a starting point to elucidate the oncogenic role of FTO in CML opening new possibilities to fight CML and overcome TKI resistance.