Chromatin organization and transcription factor targeting in the establishment of oncogene-induced senescence and cancer progression.
Worldwide Cancer Research
Fondazione Centro San Raffaele
Background. Oncogene-induced senescence (OIS) acts as a powerful tumor suppressive mechanism by inducing quasi-irreversible cell-cycle arrest when cells experience oncogenic stress. Senescent cells, however, can still overcome OIS leading to cancer onset.  Senescence is caused by persistent DNA damage and it is characterized by massive chromatin reorganization and altered gene expression profiles, including the establishment of SASP, an inflammatory transcriptional program. Senescence can propagate to bystander cells, due to SASP-dependent paracrine and SASP-independent juxtacrine mechanisms. Key transcription factors (TFs) such as p53 and NF-kB mediate these processes but how chromatin impacts their activation and binding dynamics in OIS, in bystander senescence (BySen) and upon senescence overcome (SenOv) has been only marginally explored.  Objective. We will test an uncharted hypothesis on early tumorigenesis: the massive chromatin reorganization observed upon OIS induction shape the search mechanism and the activity of the key TFs implicated in OIS, BySen and SenOv. To this end, we will integrate genomic technologies with unique microscopy approaches that we developed to probe TF activity at the single-cell and single-molecule level.  Experimental Plan. We will model OIS – by oncogene induction - and SenOv – by histone demethylases overexpression - in human fibroblasts and melanocytes. We will analyze chromatin reorganization, TFs binding, and target gene expression in single cells using super-resolution and single-molecule microscopy to answer these questions: Does chromatin reorganization in OIS control the capability of TFs to find, bind and activate their targets? How does the further chromatin remodeling in BySen and SenOv affect TFs activity? How do paracrine signaling in modulate chromatin organization and TFs action?  Significance. We will picture with single-cell resolution the interplay between chromatin architecture, TFs activity and paracrine signaling in a tumorigenesis model, leading to fundamental insights about early cancer progression that could be translated into the identification of novel druggable targets.
2.1 Biological and endogenous factors