Oncogenes induce senescence with incomplete growth arrest and suppress the DNA damage response in immortalized cells

Abstract Abstract 3083 Poster Board III-20 Histone Deacetylase Inhibitors (HDACi) such as LBH589, which inhibit the zinc containing catalytic domain of HDAC of classes I, II, and IV, demonstrate activity against various malignancies, particularly lymphoid malignancies. SIRT1 is an NAD+ dependent class III histone deacetylase, which deacetylates histones as well as non-histone proteins and is not affected directly by HDACi such as LBH589. It remains controversial whether inhibition of SIRT1 or its activation is more efficacious in anticancer therapy. We have studied the activity of two novel SIRT1 activators, SRT501 and SRT2183, in Philadelphia chromosome negative acute lymphoblastic leukemia (ALL) cell lines. Both pre B (NALM-6, Reh) and T cell (MOLT-4) ALL lines were treated with either SRT501 or SRT2183, as well as in combination with LBH589 and evaluated for biological and gene expression responses. SRT501 induced growth arrest and apoptosis at doses ranging from 10-100 uM, with even the lowest doses inhibiting growth at 72 hours. SRT2183 is much more potent, with growth arrest and apoptosis induced at doses ranging from 1-20 uM. PCR array analysis revealed that SRT2183 treatment leads to increased mRNA levels of pro-apoptosis, growth arrest, and DNA damage response genes. We have previously demonstrated that the activity of LBH589 is mediated in part through upregulation or acetylation of proteins involved in the DNA damage response pathways. Quantitative real-time PCR confirms that the combination of LBH589 with SRT2183 leads to significantly higher expression of GADD45A and GADD45G than either agent alone. The combination of LBH589 plus SRT2183 showed enhanced inhibition of c-Myc protein levels, phosphorylation of H2A.X, and interestingly, increased acetylation of p53 (acetylation of p53 was not seen with SRT2183 alone). In summary, the novel SIRT1 activators SRT501 and SRT2183 show growth inhibitory and pro-apoptotic activity in Ph- ALL alone and enhanced activity in combination with LBH589. Clinical studies of these agents, particularly in combination with HDACi are warranted. Disclosures Kirschbaum: Novartis: Consultancy. Cermak:Sirtris: Employment. Atadja:Novartis: Employment.

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The dual role of the RETINOBLASTOMA-RELATED protein in the DNA damage response is spatio-temporally coordinated by the interaction with LXCXE-containing proteins.

10.1101/2021.12.22.473497 ◽

2021 ◽

Author(s):

Jorge Zamora-Zaragoza ◽

Katinka Klap ◽

Renze Heidstra ◽

Wenkun Zhou ◽

Ben Scheres

Keyword(s):

Dna Damage ◽

Cell Death ◽

Dna Repair ◽

Cell Division ◽

Dna Damage Response ◽

Growth Arrest ◽

Focus Formation ◽

Damage Response ◽

Nuclear Foci ◽

Lxcxe Motif

Living organisms face threats to genome integrity caused by environmental challenges or metabolic errors in proliferating cells. To avoid the spread of mutations, cell division is temporarily arrested while repair mechanisms deal with DNA lesions. Afterwards, cells either resume division or respond to unsuccessful repair by withdrawing from the cell cycle and undergoing cell death. How the success rate of DNA repair connects to the execution of cell death remains incompletely known, particularly in plants. Here we provide evidence that the Arabidopsis thaliana RETINOBLASTOMA-RELATED1 (RBR) protein, shown to play structural and transcriptional functions in the DNA damage response (DDR), coordinates these processes in time by successive interactions through its B-pocket sub-domain. Upon DNA damage induction, RBR forms nuclear foci; but the N849F substitution in the B-pocket, which specifically disrupts binding to LXCXE motif-containing proteins, abolishes RBR focus formation and leads to growth arrest. After RBR focus formation, the stress-responsive gene NAC044 arrests cell division. As RBR is released from nuclear foci, it can be bound by the conserved LXCXE motif in NAC044. RBR-mediated cell survival is inhibited by the interaction with NAC044. Disruption of NAC044-RBR interaction impairs the cell death response but is less important for NAC044 mediated growth arrest. Noteworthy, unlike many RBR interactors, NAC044 binds to RBR independent of RBR phosphorylation. Our findings suggest that the availability of the RBR B-pocket to interact with LXCXE-containing proteins couples the structural DNA repair functions and the transcriptional functions of RBR in the cell death program.

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Singular v Dual inhibition of SNF2L and its isoform, SNF2LT, have similar effects on DNA Damage but opposite effects on the DNA Damage Response, Cancer Cell Growth Arrest and Apoptosis

Oncotarget ◽

10.18632/oncotarget.479 ◽

2012 ◽

Vol 3 (4) ◽

pp. 475-489 ◽

Cited By ~ 4

Author(s):

Yin Ye ◽

Yi Xiao ◽

Wenting Wang ◽

Jian-Xin Gao ◽

Kurtis Yearsley ◽

...

Keyword(s):

Dna Damage ◽

Cell Growth ◽

Cancer Cell ◽

Dna Damage Response ◽

Growth Arrest ◽

Cancer Cell Growth ◽

Cell Growth Arrest ◽

Damage Response ◽

Dual Inhibition

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The novel histone deacetylase inhibitor, LBH589, induces expression of DNA damage response genes and apoptosis in Ph− acute lymphoblastic leukemia cells

Blood ◽

10.1182/blood-2007-10-117762 ◽

2008 ◽

Vol 111 (10) ◽

pp. 5093-5100 ◽

Cited By ~ 92

Author(s):

Anna Scuto ◽

Mark Kirschbaum ◽

Claudia Kowolik ◽

Leo Kretzner ◽

Agnes Juhasz ◽

...

Keyword(s):

Dna Damage ◽

Acute Lymphoblastic Leukemia ◽

Dna Damage Response ◽

Lymphoblastic Leukemia ◽

Philadelphia Chromosome ◽

Growth Arrest ◽

Clinical Activity ◽

Mrna Levels ◽

Damage Response ◽

Potent Growth

Abstract We investigated the mechanism of action of LBH589, a novel broad-spectrum HDAC inhibitor belonging to the hydroxamate class, in Philadelphia chromosome–negative (Ph−) acute lymphoblastic leukemia (ALL). Two model human Ph− ALL cell lines (T-cell MOLT-4 and pre–B-cell Reh) were treated with LBH589 and evaluated for biologic and gene expression responses. Low nanomolar concentrations (IC50: 5-20 nM) of LBH589 induced cell-cycle arrest, apoptosis, and histone (H3K9 and H4K8) hyperacetylation. LBH589 treatment increased mRNA levels of proapoptosis, growth arrest, and DNA damage repair genes including FANCG, FOXO3A, GADD45A, GADD45B, and GADD45G. The most dramatically expressed gene (up to 45-fold induction) observed after treatment with LBH589 is GADD45G. LBH589 treatment was associated with increased histone acetylation at the GADD45G promoter and phosphorylation of histone H2A.X. Furthermore, treatment with LBH589 was active against cultured primary Ph− ALL cells, including those from a relapsed patient, inducing loss of cell viability (up to 70%) and induction of GADD45G mRNA expression (up to 35-fold). Thus, LBH589 possesses potent growth inhibitory activity against including Ph− ALL cells associated with up-regulation of genes critical for DNA damage response and growth arrest. These findings provide a rationale for exploring the clinical activity of LBH589 in the treatment of patients with Ph− ALL.

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The DREAM complex represses growth in response to DNA damage in Arabidopsis

Life Science Alliance ◽

10.26508/lsa.202101141 ◽

2021 ◽

Vol 4 (12) ◽

pp. e202101141

Author(s):

Lucas Lang ◽

Aladár Pettkó-Szandtner ◽

Hasibe Tunçay Elbaşı ◽

Hirotomo Takatsuka ◽

Yuji Nomoto ◽

...

Keyword(s):

Cell Proliferation ◽

Dna Damage ◽

Dna Damage Response ◽

Double Mutant ◽

Growth Arrest ◽

Suppressor Gene ◽

Physiological Processes ◽

Damage Response ◽

Arabidopsis Homolog ◽

Close Homolog

The DNA of all organisms is constantly damaged by physiological processes and environmental conditions. Upon persistent damage, plant growth and cell proliferation are reduced. Based on previous findings that RBR1, the only Arabidopsis homolog of the mammalian tumor suppressor gene retinoblastoma, plays a key role in the DNA damage response in plants, we unravel here the network of RBR1 interactors under DNA stress conditions. This led to the identification of homologs of every DREAM component in Arabidopsis, including previously not recognized homologs of LIN52. Interestingly, we also discovered NAC044, a mediator of DNA damage response in plants and close homolog of the major DNA damage regulator SOG1, to directly interact with RBR1 and the DREAM component LIN37B. Consistently, not only mutants in NAC044 but also the double mutant of the two LIN37 homologs and mutants for the DREAM component E2FB showed reduced sensitivities to DNA-damaging conditions. Our work indicates the existence of multiple DREAM complexes that work in conjunction with NAC044 to mediate growth arrest after DNA damage.

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