Background And Purpose: KRAS is frequently mutated, and the Y-box binding protein 1 (YB-1) is overexpressed in colorectal cancer (CRC). Mutant KRAS (KRAS) stimulates YB-1 through MAPK/RSK and PI3K/AKT, independent of epidermal growth factor receptor (EGFR). The p21-activated kinase (PAK) family is a switch-site upstream of AKT and RSK. The flavonoid compound fisetin inhibits RSK-mediated YB-1 signaling. We sought the most effective molecular targeting approach that interferes with DNA double strand break (DSB) repair and induces radiosensitivity of CRC cells, independent of KRAS mutation status.
Materials And Methods: KRAS activity and KRAS mutation were analyzed by Ras-GTP assay and NGS. Effect of dual targeting of RSK and AKT (DT), the effect of fisetin as well as targeting PAK by FRAX486 and EGFR by erlotinib on YB-1 activity was tested by Western blotting after irradiation in vitro and ex vivo. Additionally, the effect of DT and FRAX486 on DSB repair pathways was tested in cells expressing reporter constructs for the DSB repair pathways by flow cytometry analysis. Residual DSBs and clonogenicity were examined by γH2AX- and clonogenic assays, respectively.
Results: Erlotinib neither blocked DSB repair nor inhibited YB-1 phosphorylation under KRAS mutation condition in vitro and ex vivo. DT and FRAX486 effectively inhibited YB-1 phosphorylation independent of KRAS mutation status and diminished homologous recombination (HR) and alternative non-homologous end joining (NHEJ) repair. DT and FRAX486 inhibited DSB repair in CaCo2 but not in isogenic KRAS cells. Fisetin inhibited YB-1 phosphorylation, blocked DSB repair and increased radiosensitivity, independent of KRAS mutation status.
Conclusion: Combination of fisetin with radiotherapy may improve CRC radiation response, regardless of KRAS status.
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http://dx.doi.org/10.1016/j.radonc.2023.109867 | DOI Listing |
Exp Mol Med
January 2025
Section on DNA Repair, Laboratory of Genetics and Genomics, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
RecQ helicases, highly conserved proteins with pivotal roles in DNA replication, DNA repair and homologous recombination, are crucial for maintaining genomic integrity. Mutations in RECQL4 have been associated with various human diseases, including Rothmund-Thomson syndrome. RECQL4 is involved in regulating major DNA repair pathways, such as homologous recombination and nonhomologous end joining (NHEJ).
View Article and Find Full Text PDFCell Mol Life Sci
January 2025
Department of Clinical Laboratory, Harbin Medical University Cancer Hospital, 150 Haping Road, Harbin, 150081, China.
Non-small cell lung cancer (NSCLC) has emerged as one of the most prevalent malignancies worldwide. N6-methyladenosine (mA) methylation, a pervasive epigenetic modification in long noncoding RNAs (lncRNAs), plays a crucial role in NSCLC progression. Here, we report that mA modification and the expression of the lncRNA stem cell inhibitory RNA transcript (SCIRT) was significantly upregulated in NSCLC tissues and cells.
View Article and Find Full Text PDFDNA double strand breaks (DSBs) are widely considered the most cytotoxic DNA lesions occurring in cells because they physically disrupt the connectivity of the DNA double helix. Homologous recombination (HR) is a high-fidelity DSB repair pathway that copies the sequence spanning the DNA break from a homologous template, most commonly the sister chromatid. How both DNA ends, and the sister chromatid are held in close proximity during HR is unknown.
View Article and Find Full Text PDFJ Clin Immunol
January 2025
Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children´s Medical Center, Tehran University of Medical Sciences, 62 Qarib St., Keshavarz Blvd, Tehran, 14194, Iran.
Background: Ataxia telangiectasia mutated (ATM) kinase plays a critical role in DNA double-strand break (DSB) repair. Ataxia telangiectasia (A-T) patients exhibit abnormalities in immunoglobulin isotype expression and class switch recombination (CSR). This study investigates the role of residual ATM kinase expression and activity in the severity of A-T disease.
View Article and Find Full Text PDFDNA Repair (Amst)
January 2025
Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA. Electronic address:
Proper chromatin remodeling is crucial for many cellular physiological processes, including the repair of DNA double-strand break (DSB). While the mechanism of DSB repair is well understood, the connection between chromatin remodeling and DSB repair remains incompletely elucidated. In this review, we aim to highlight recent studies demonstrating the close relationship between chromatin remodeling and DSB repair.
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