RAS causes hyperproliferation and S\phase\associated DNA damage response (DDR). function of class IIa HDACs in human being cells, and justify further efforts to discover and evaluate isoform\specific inhibitors of these epigenetic regulators from a restorative perspective. and studies have proved the oncogenic p-Cresol part of HDAC4 (Di Giorgio oncogenic transformation of normal cells represents an invaluable model to demonstrate tumor\suppressive or oncogenic functions of a specific gene (Funes transforming activities of the tested genes and their implications in human being cancers (Boehm and Hahn, 2005; Boehm generated transformed Hif1a p-Cresol cells can provide alternatives to expensive mouse models, as well as genetically defined environments for screening anticancer therapies (Balani nnnnnnnand and induction. In RAS\expressing cells this response was only obvious after 8?days of induction. 3.3. HDAC4\induced senescence depends on TP53 activation The induction of DNA damage in TM\expressing cells prompted us to investigate the contribution of TP53. Immunoblot analysis performed after 8?days of transgene induction demonstrated a p-Cresol strong up\rules of TP53 levels in TM cells (Fig.?3A). To investigate the contribution of TP53 in TM\induced senescence, we generated BJ\TERT cells expressing TP53 mutant R175H (Fig.?3B). This mutant is frequently found in human being cancers and functions as a dominating bad (TP53DN) (Gualberto and (Fig.?3C). Subsequently, we generated BJ\TERT/TP53 cells expressing HDAC4\TM, RAS or GFP as control. Immunoblot analysis confirmed the manifestation of the different transgenes and showed that Lamin B1 was not down\regulated in TM cells, therefore suggesting the escape from senescence (Fig.?3D). SA\\gal activity (Fig.?3E) and the family member quantitative analysis (Fig.?3F) confirmed the failure of TM in triggering senescence, once the TP53 response was blunted. In contrast, in RAS\expressing cells, suppression of TP53 activities was not adequate to block the event of senescence (Fig.?3E,F), as previously observed (Serrano nnnnnnnnnnnnnnntransformation process is less obvious (Christian em et?al /em ., 2012). Gene signatures specifically affected by HDAC4\TM are more heterogeneous and involve adaptation to hypoxia, adhesion, motility and differentiation processes. It is possible that RAS more potently suppresses the IFN reactions compared with HDAC4\TM, which instead represses additional pathways. The ability of HDAC4\TM to regulate genes involved in adhesion and motility was confirmed in the morphological analysis of p-Cresol smooth agar foci as well as with the results acquired with Matrigel invasion and evasion assays. These results indicate that HDAC4\expressing cells show a strong invasive phenotype, further supported by previous studies on the invasive, migrating and metastatic activities of class IIa HDACs (Cao em et?al /em ., 2017; Cernotta em et?al /em ., 2011; Di Giorgio em et?al /em ., 2013; Fabian em et?al /em ., 2016; Mottet em et?al /em ., 2007). Normal cells in response to oncogenic signals enter into senescence, a state of irreversible/long term growth arrest that helps prevent cells from undergoing further cell divisions, defined as OIS (Serrano em et?al /em ., 1997). Activation of OIS depends on the pRB and/or TP53 tumor suppressor pathways (Serrano em et?al /em ., 1997). We have proved that HDAC4\TM, in TERT\immortalized human being fibroblasts, p-Cresol can activate senescence. This senescent response can be also induced by additional class IIa HDACs such as HDAC7, when localized into the nucleus (Assisting Info Fig.?S1). Since the manifestation of HDAC4\TM in the opportune genetic environment (LT/ST co\manifestation) can transform cells, and since the senescent response is definitely p53\dependent, we can define senescence induced by HDAC4\TM as OIS. However, OIS induced by RAS cannot be reversed by simply obstructing TP53 activity, but requires the suppression of pRB, probably through the CDK inhibitor p16 (Serrano em et?al /em ., 1997). The difference between HDAC4\TM and RAS can be appreciated also at the earliest phases of their induction. RAS causes hyperproliferation and S\phase\connected DNA damage response (DDR). The oncogene\dependent increase in proliferation prospects to build up of incomplete replication intermediates,.