Drosophila FMRP participates in the DNA damage response by regulating G2/M cell cycle checkpoint and apoptosis

ABSTRACT Activation of Akt, or protein kinase B, is frequently observed in human cancers. Here we report that Akt activation via overexpression of a constitutively active form or via the loss of PTEN can overcome a G2/M cell cycle checkpoint that is induced by DNA damage. Activated Akt also alleviates the reduction in CDC2 activity and mitotic index upon exposure to DNA damage. In addition, we found that PTEN null embryonic stem (ES) cells transit faster from the G2/M to the G1 phase of the cell cycle when compared to wild-type ES cells and that inhibition of phosphoinositol-3-kinase (PI3K) in HEK293 cells elicits G2 arrest that is alleviated by activated Akt. Furthermore, the transition from the G2/M to the G1 phase of the cell cycle in Akt1 null mouse embryo fibroblasts (MEFs) is attenuated when compared to that of wild-type MEFs. These results indicate that the PI3K/PTEN/Akt pathway plays a role in the regulation of G2/M transition. Thus, cells expressing activated Akt continue to divide, without being eliminated by apoptosis, in the presence of continuous exposure to mutagen and accumulate mutations, as measured by inactivation of an exogenously expressed herpes simplex virus thymidine kinase (HSV-tk) gene. This phenotype is independent of p53 status and cannot be reproduced by overexpression of Bcl-2 or Myc and Bcl-2 but seems to counteract a cell cycle checkpoint mediated by DNA mismatch repair (MMR). Accordingly, restoration of the G2/M cell cycle checkpoint and apoptosis in MMR-deficient cells, through reintroduction of the missing component of MMR, is alleviated by activated Akt. We suggest that this new activity of Akt in conjunction with its antiapoptotic activity may contribute to genetic instability and could explain its frequent activation in human cancers.

Download Full-text

The RNA polymerase I transcription inhibitor CX-5461 cooperates with topoisomerase 1 inhibition by enhancing the DNA damage response in homologous recombination-proficient high-grade serous ovarian cancer

British Journal of Cancer ◽

10.1038/s41416-020-01158-z ◽

2020 ◽

Author(s):

Shunfei Yan ◽

Jiachen Xuan ◽

Natalie Brajanovski ◽

Madeleine R. C. Tancock ◽

Piyush B. Madhamshettiwar ◽

...

Keyword(s):

Ovarian Cancer ◽

Dna Damage ◽

Homologous Recombination ◽

Dna Damage Response ◽

Cell Cycle Checkpoint ◽

Common Mechanism ◽

High Grade ◽

M Cell ◽

Topoisomerase 1 ◽

Damage Response

Abstract Background Intrinsic and acquired drug resistance represent fundamental barriers to the cure of high-grade serous ovarian carcinoma (HGSC), the most common histological subtype accounting for the majority of ovarian cancer deaths. Defects in homologous recombination (HR) DNA repair are key determinants of sensitivity to chemotherapy and poly-ADP ribose polymerase inhibitors. Restoration of HR is a common mechanism of acquired resistance that results in patient mortality, highlighting the need to identify new therapies targeting HR-proficient disease. We have shown promise for CX-5461, a cancer therapeutic in early phase clinical trials, in treating HR-deficient HGSC. Methods Herein, we screen the whole protein-coding genome to identify potential targets whose depletion cooperates with CX-5461 in HR-proficient HGSC. Results We demonstrate robust proliferation inhibition in cells depleted of DNA topoisomerase 1 (TOP1). Combining the clinically used TOP1 inhibitor topotecan with CX-5461 potentiates a G2/M cell cycle checkpoint arrest in multiple HR-proficient HGSC cell lines. The combination enhances a nucleolar DNA damage response and global replication stress without increasing DNA strand breakage, significantly reducing clonogenic survival and tumour growth in vivo. Conclusions Our findings highlight the possibility of exploiting TOP1 inhibition to be combined with CX-5461 as a non-genotoxic approach in targeting HR-proficient HGSC.

Download Full-text

Intersection of Two Checkpoints: Could Inhibiting the DNA Damage Response Checkpoint Rescue Immune Checkpoint-Refractory Cancer?

Cancers ◽

10.3390/cancers13143415 ◽

2021 ◽

Vol 13 (14) ◽

pp. 3415

Author(s):

Peter H. Goff ◽

Rashmi Bhakuni ◽

Thomas Pulliam ◽

Jung Hyun Lee ◽

Evan T. Hall ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Tumor Immunity ◽

Immune Checkpoint ◽

Ataxia Telangiectasia ◽

Management Strategies ◽

Adaptive Immune Response ◽

Cell Cycle Checkpoint ◽

Damage Response ◽

Cycle Checkpoint

Metastatic cancers resistant to immunotherapy require novel management strategies. DNA damage response (DDR) proteins, including ATR (ataxia telangiectasia and Rad3-related), ATM (ataxia telangiectasia mutated) and DNA-PK (DNA-dependent protein kinase), have been promising therapeutic targets for decades. Specific, potent DDR inhibitors (DDRi) recently entered clinical trials. Surprisingly, preclinical studies have now indicated that DDRi may stimulate anti-tumor immunity to augment immunotherapy. The mechanisms governing how DDRi could promote anti-tumor immunity are not well understood; however, early evidence suggests that they can potentiate immunogenic cell death to recruit and activate antigen-presenting cells to prime an adaptive immune response. Merkel cell carcinoma (MCC) is well suited to test these concepts. It is inherently immunogenic as ~50% of patients with advanced MCC persistently benefit from immunotherapy, making MCC one of the most responsive solid tumors. As is typical of neuroendocrine cancers, dysfunction of p53 and Rb with upregulation of Myc leads to the very rapid growth of MCC. This suggests high replication stress and susceptibility to DDRi and DNA-damaging agents. Indeed, MCC tumors are particularly radiosensitive. Given its inherent immunogenicity, cell cycle checkpoint deficiencies and sensitivity to DNA damage, MCC may be ideal for testing whether targeting the intersection of the DDR checkpoint and the immune checkpoint could help patients with immunotherapy-refractory cancers.

Download Full-text

Arabidopsis Casein Kinase 2 triggers Stem Cell Exhaustion under Al Toxicity and Phosphate Deficiency Through activation of the DNA Damage Response pathway

10.1101/2020.11.30.404459 ◽

2020 ◽

Author(s):

Wei Pengliang ◽

Manon Demulder ◽

Pascale David ◽

Thomas Eekhout ◽

Kaoru Okamoto Yoshiyama ◽

...

Keyword(s):

Dna Damage ◽

Stem Cell ◽

Dna Damage Response ◽

Stem Cell Niche ◽

Al Toxicity ◽

Cell Cycle Checkpoint ◽

Damage Response ◽

Cycle Checkpoint ◽

Cell Niche ◽

Dna Damage Response Pathway

Aluminum (Al) toxicity and inorganic phosphate (Pi) limitation are widespread chronic abiotic and mutually enhancing stresses that profoundly affect crop yield. Both stresses cause a strong inhibition of root growth, resulting from a progressive exhaustion of the stem cell niche. Here, we report on a casein kinase 2 (CK2) inhibitor identified by its capability to maintain a functional root stem cell niche under Al toxic conditions. CK2 operates through phosphorylation of the cell cycle checkpoint activator SUPPRESSOR OF GAMMA RADIATION1 (SOG1), priming its activity under DNA-damaging conditions. In addition to yielding Al tolerance, CK2 and SOG1 inactivation prevents meristem exhaustion under Pi starvation, revealing the existence of a low Pi-induced cell cycle checkpoint that depends on the DNA damage activator ATAXIA-TELANGIECTASIA MUTATED. Overall, our data reveal an important physiological role for the plant DNA damage response pathway under agriculturally limiting growth conditions, opening new avenues to cope with Pi limitation.

Download Full-text

An intimate alliance of DNA-damage response network with cell-cycle checkpoints amid events of uncontrolled cellular proliferation- a minireview

Endocrine Metabolic & Immune Disorders - Drug Targets ◽

10.2174/1871530320999200918143856 ◽

2020 ◽

Vol 20 ◽

Author(s):

Aroni Chatterjee ◽

Keshav Rajarshi ◽

Rajni Khan ◽

Hiya Ghosh ◽

Sonia Kapoor ◽

...

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Dna Damage Response ◽

Cellular Proliferation ◽

Cell Senescence ◽

Cell Cycle Checkpoint ◽

Effector Proteins ◽

Cell Cycle Checkpoints ◽

Response Network ◽

Damage Response

: There is close interdependence between cell survival, cell senescence, events of the cell cycle, apoptosis, malignancy development, and tumor responses to cancer treatment. Intensive studies and elaborate researches have been conducted on the functional aspects of oncogenes, tumor suppressor genes, apoptotic genes, and members guiding cell cycle regulation. These disquisitions have put forward the existence of a highly organized response pathway termed as a DNAdamage response network. The pathways detecting DNA damage and signaling are intensively linked to the events of cellcycle arrest, cell proliferation, apoptosis, and cell senescence. DNA damage responses are complex systems that incorporate specific "sensor" and "transducer" proteins, for assessment of damage and signal transmission, respectively. These signals are thereafter relayed upon various "effector" proteins involved in different cellular pathways. It may include those governing cell-cycle checkpoints, participating in DNA repair, cell senescence, and apoptosis. This review discusses about the role of tumour suppressor gene, oncogenes, cell cycle checkpoint regulators during DNA damage response and regulation.

Download Full-text

Deciphering the Genetic Aberrations in DNA Damage Response Genes and Their Possible Association with HNSCC

Journal of Pharmaceutical Research International ◽

10.9734/jpri/2020/v32i1530639 ◽

2020 ◽

pp. 156-169

Author(s):

L. Akshayaa ◽

A. S. Smiline Girija ◽

A. Paramasivam ◽

J. Vijayashree Priyadharsini

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Wide Spectrum ◽

Survival Curve ◽

Cell Cycle Checkpoint ◽

Single Nucleotide Variants ◽

Differential Expression Pattern ◽

Damage Response ◽

Cycle Checkpoint ◽

High Level

Head and neck squamous cell carcinoma (HNSCC) includes carcinomas in the oral cavity, pharynx and larynx. It is considered as the sixth most common form of cancer in the world. Several studies have confirmed that smoking and alcohol consumption are the major risk factors for HNSCC. DNA damage response genes play an important role in the maintenance of the genome. Defects in cell cycle checkpoint and DNA repair mechanisms, such as mutation or abnormalities, may lead to the wide spectrum of human diseases. The present study employs databases and computational tools to identify the genetic abnormalities associated with DNA damage related genes which might have a direct or indirect association with HNSCC. The demographic details of HNSCC patients was obtained from The Cancer Gene Atlas (TCGA, Firehose Legacy) dataset hosted by the cBioportal database. The oncoprint data analysis revealed the highest frequency of gene alteration in the ATR gene (15%), followed by ATM, BRCA2 and CHEK2 (5%). Other genes showed less than 5% alteration. The gene expression profile of ATR gene revealed its differential expression pattern in different grades of tumor relative to normal samples. The survival curve analysis using Kaplan-Meier method revealed that a high level expression of the ATR gene leads to poor survival rate in the female HNSCC patients when compared to males. Thus the present study has identified gross and single nucleotide variants in the ATR gene which could have a putative role in the development of tumor. Further experimental research is required to confirm this association.

Download Full-text