Replication stress and FOXM1 drive radiation induced genomic instability and cell transformation

Abstract

In contrast to the vast majority of research that has focused on the immediate effects of ionizing radiation, this work concentrates on the molecular mechanism driving delayed effects that emerge in the progeny of the exposed cells. We employed functional protein arrays to identify molecular changes induced in a human bronchial epithelial cell line (HBEC3-KT) and osteosarcoma cell line (U2OS) and evaluated their impact on outcomes associated with radiation induced genomic instability (RIGI) at day 5 and 7 post-exposure to a 2Gy X-ray dose, which revealed replication stress in the context of increased FOXM1b expression. Irradiated cells had reduced DNA replication rate detected by the DNA fiber assay and increased DNA resection detected by RPA foci and phosphorylation. Irradiated cells increased utilization of homologous recombination-dependent repair detected by a gene conversion assay and DNA damage at mitosis reflected by RPA positive chromosomal bridges, micronuclei formation and 53BP1 positive bodies in G1, all known outcomes of replication stress. Interference with the function of FOXM1, a transcription factor widely expressed in cancer, employing an aptamer, decreased radiation-induced micronuclei formation and cell transformation while plasmid-driven overexpression of FOXM1b was sufficient to induce replication stress, micronuclei formation and cell transformation.

Co-regulation and function of FOXM1/RHNO1 bidirectional genes in cancer

“…FOXM1 and RHNO1 co-expression may increase tumor resiliency by allowing tumor cells to gain a fitness advantage of increased growth and proliferation without accumulating excessive DNA damage. Consistently, FOXM1-expressing tumors are highly enriched for biomarkers of RS ( Li et al, 2020 ). Therapeutic targeting of the FOXM1/RHNO1 bidirectional gene unit may be accomplished using inhibitors of FOXM1 and/or ATR/Chk1/WEE1.…”

“…Critical support for this model is provided by a recent study that demonstrated that FOXM1 expression induced RS and genomic instability in bronchial epithelial cells and U2OS cells ( Li et al, 2020 ). Additionally, the authors showed that FOXM1 expression correlates with RS biomarkers in The Cancer Protein Atlas data from several cancer types, including HGSC ( Li et al, 2020 ). We thus hypothesize that the mechanistic link between FOXM1 and RHNO1 centers around RS, in that RHNO1 may help to mitigate excessive RS driven by FOXM1 ( Figure 21 ).…”

“…Molecular features of this tumor type include ubiquitous TP53 mutations, defects in DNA homologous recombination repair (HR), BRCA gene mutations, and robust genomic instability characterized by widespread copy number alterations (CNAs) ( The Cancer Genome Atlas Research Network, 2011 ). Notably, FOXM1 pathway activation is a characteristic of >85% of HGSC cases and is linked to genomic instability ( Barger et al, 2019 ; The Cancer Genome Atlas Research Network, 2011 ; Barger et al, 2015 ; Li et al, 2020 ). FOXM1 overexpression in HGSC and other cancers is driven by several mechanisms, including copy number gains, loss of function of p53 and pRB, activation of SP1, E2F1, and cyclin E1, and YAP signaling ( Barger et al, 2019 ; Barger et al, 2015 ; Fan et al, 2015 ; Petrovic et al, 2010 ).…”

FOXM1: A Multifunctional Oncoprotein and Emerging Therapeutic Target in Ovarian Cancer

“…DNA replication stress (RS) is caused by extrinsic and intrinsic factors that disrupt replication fork dynamics, and critically, RS is a major driver of cancer genomic instability [ 307 , 308 ]. Notably, FOXM1 was recently reported to induce DNA replication stress in vitro and FOXM1 expression was observed to correlate with expression of RS biomarkers in several cancer types, including HGSC [ 309 ]. Our recent study also suggests a link between FOXM1 and RS.…”

Berberine Inhibits FoxM1 Dependent Transcriptional Regulation of POLE2 and Interferes with the Survival of Lung Adenocarcinoma

“…FoxM1 played an important role in DNA replication. FoxM1 was recently reported to induce DNA replication pressure in vitro, and FoxM1 expression was observed to be associated with the expression of DNA replication pressure biomarkers in several cancer types 30 . In order to evaluate the role of FoxM1 in DNA replication of lung adenocarcinoma cells, we further analyzed the transcriptional regulation of related differential genes in DNA replication pathway.…”