Knockdown of RAD54B expression reduces cell proliferation and induces apoptosis in lung cancer cells

RAD54B promotes gastric cancer cell migration and angiogenesis via the Wnt/β-catenin pathway

BACKGROUND

Gastric cancer is an epidemic malignancy that is commonly diagnosed at the late stage. Evidence has elucidated that RAD54B exerts a crucial role in the progress of various tumors, but its specific role and mechanism in gastric cancer remain gloomy.

MATERIALS AND METHODS

The level of RAD54B was detected by western blot. RAD54B expression was downregulated or upregulated in both MKN45 and AGS cells by the transfection of shRAD54B or overexpression plasmid, respectively. The role of RAD54B in the growth, migration, invasion and tube formation of gastric cancer was evaluated by Edu, colony formation, transwell and tube formation assays. In addition, the molecular mechanism of RAD54B in gastric cancer was also determined by western blot. Moreover, in vivo experiment was conducted in xenografted mice.

RESULTS

The expression of RAD54B was discovered to be upregulated in gastric cancer based on the ATGC and GEPIA databases, which was also confirmed in gastric cancer cell lines. Moreover, overexpression of RAD54B enhanced the growth, migration, invasion, tube formation and Wnt/β-catenin signaling axis in AGS and MKN45 cells. As expected, knockdown of RAD54B in AGS and MKN45 cells reversed these promotions. More importantly, in vivo assay also verified that RAD54B accelerated the growth of gastric cancer and Wnt/β-catenin signaling pathway.

CONCLUSIONS

Both loss-of-function and gain-of-function assays demonstrated that RAD54B facilitated gastric cancer cell progress and angiogenesis through the Wnt/β-catenin axis.

RAD54B inhibits vascular endothelial senescence via suppression of CHK1/p53/p21 pathway

RAD54B belongs to the SNF2/SWI2 superfamily, participating in homologous recombination repair. DNA damage is the central driver of aging, but there is no direct evidence of an association between RAD54B and vascular aging. The present study sought to investigate the role and mechanisms of RAD54B in endothelial senescence. In senescent animal models, including spontaneously hypertensive rats, normal aging mice, and D-gal-induced senescent mice, and senescent cell models induced by H2O2, D-gal, and culture, RAD54B was remarkably downregulated. Knockdown of RAD54B increased the expression of p53 and p21, increased the ratio of SA-β-gal-positive cells, and decreased the proportion of EdU-positive cells. Conversely, overexpression of RAD54B reversed the senescent phenotypes stimulated by H2O2 and delayed replicative endothelial senescence. Mechanistically, silencing RAD54B compensatorily increased the expression of RAD51/XRCC4, which remained unchanged in H2O2-induced senescence. RAD54B lacking the SNF2 domain could still reverse the increasing expression of p53/p21 induced by H2O2. RAD54B reduced γH2A.X expression and inhibited the expression and phosphorylation of CHK1. In conclusion, RAD54B exerts a direct protective effect against DNA damage through enhancing homologous recombination repair in endothelial senescence, resulting in inhibition of the downstream CHK1/p53/p21 pathway, suggesting that RAD54B may be a potential therapeutic target for vascular aging-associated diseases.

Large-scale phenogenomic analysis of human cancers uncovers frequent alterations affecting SMC5/6 complex components in breast cancer

Cancer cells often experience large-scale alterations in genome architecture because of DNA damage and replication stress. Whether mutations in core regulators of chromosome structure can also lead to cancer-promoting loss in genome stability is not fully understood. To address this question, we conducted a systematic analysis of mutations affecting a global regulator of chromosome biology -the SMC5/6 complex- in cancer genomics cohorts. Analysis of 64 959 cancer samples spanning 144 tissue types and 199 different cancer genome studies revealed that the SMC5/6 complex is frequently altered in breast cancer patients. Patient-derived mutations targeting this complex associate with strong phenotypic outcomes such as loss of ploidy control and reduced overall survival. Remarkably, the phenotypic impact of several patient mutations can be observed in a heterozygous context, hence providing an explanation for a prominent role of SMC5/6 mutations in breast cancer pathogenesis. Overall, our findings suggest that genes encoding global effectors of chromosome architecture can act as key contributors to cancer development in humans.

Impact of GTF2H1 and RAD54L2 polymorphisms on the risk of lung cancer in the Chinese Han population

Background

Repair pathway genes play an important role in the development of lung cancer. The study aimed to assess the correlation between single nucleotide polymorphisms (SNPs) in DNA repair gene (GTF2H1 and RAD54L2) and the risk of lung cancer.

Methods

Five SNPs in GTF2H1 and four SNPs in RAD54L2 in 506 patients with lung cancer and 510 age-and gender-matched healthy controls were genotyped via the Agena MassARRAY platform. The influence of GTF2H1 and RAD54L2 polymorphisms on lung cancer susceptibility was assessed using logistic regression analysis by calculating odds ratios (ORs) and their corresponding 95% confidence intervals (CIs).

Results

RAD54L2 rs9864693 GC genotype increased the risk of lung cancer (OR = 1.33, 95%CI: 1.01–1.77, p = 0.045). Stratified analysis found that associations of RAD54L2 rs11720298, RAD54L2 rs4687592, RAD54L2 rs9864693 and GTF2H1 rs4150667 with lung cancer risk were found in subjects aged ≤ 59 years. Precisely, a protective effect of RAD54L2 rs11720298 on the occurrence of lung cancer was observed in non-smokers and drinkers. GTF2H1 rs4150667 was associated with a decreased risk of lung cancer in subjects with BMI ≤ 24 kg/m2. RAD54L2 rs4687592 was associated with an increased risk of lung cancer in drinkers. In addition, GTF2H1 rs3802967 was associated with a reduced risk of lung squamous cell carcinoma.

Conclusion

Our study first revealed that RAD54L2 rs9864693 was associated with an increased risk of lung cancer in the Chinese Han population. This study may increase the understanding of the effect of RAD54L2 and GTF2H1 polymorphisms on lung cancer occurrence.

RAD54B mutations enhance the sensitivity of ovarian cancer cells to poly(ADP-ribose) polymerase (PARP) inhibitors

Synthetic lethal targeting of homologous recombination (HR)–deficient ovarian cancers (OvCas) with poly(ADP-ribose) polymerase inhibitors (PARPis) has attracted considerable attention. Olaparib was the first PARPi approved by the Food and Drug Administration, offering significant clinical benefits in BRCA1/2-deficient OvCas. However, only approximately 20% of OvCa patients harbor BRCA1/2 mutations. Given the shared roles that BRCA1/2 have with other HR regulators, alterations in HR genes may also contribute to “BRCAness profiles” in OvCas. RAD54B has been considered a key player in HR repair, although its roles and therapeutic potential in cancers need further investigation. Here, we identified 22 frequently mutated HR genes by whole-exome sequencing of OvCa tissues from 82 patients. To our surprise, 7.3% of patients were found to harbor mutations of RAD54B, the third-highest mutated gene among patients. We determined that RAD54B-mutated tumor tissues harbored more DNA double-strand breaks than normal tissues. Additionally, we found that RAD54B knockdown inhibited HR repair, enhanced sensitivities of OvCa cells with increased DNA double-strand breaks to olaparib, and induced apoptosis. Enhanced inhibitory effects of olaparib on the growth of ES2 xenograft tumors were further demonstrated by RAD54B knockdown. Finally, we show that restoration with wildtype RAD54B rather than RAD54B^N593S and RAD54B^H219Y, identified in patients, abolished the effects of RAD54B knockdown, indicating these RAD54B mutants probably malfunctioned in HR repair. Our investigations may offer insight into the contributions of RAD54B mutations to synthetic lethality with olaparib treatment in OvCas, enrich the gene list for “HR deficiency scoring,” and expand the applications of PARPis.

Overexpression of the lncRNA AC012213.3 Promotes Proliferation, Migration and Invasion of Breast Cancer via RAD54B/PI3K/AKT Axis and is Associated with Worse Patient Prognosis

Background

Long noncoding RNA (LncRNA) has been shown to mediate the development of human malignancies. However, data on its role in breast cancer remains scant. We aimed to evaluate the prognostic potential of lncRNAs in breast cancer.

Methods

We downloaded data on breast cancer patients from The Cancer Genome Atlas (TCGA) database. Tissues were obtained from The Fifth People's Hospital of Chengdu. We then used the DESeq2 package to profile the expression of the lncRNAs between the patients and normal samples. Besides, we performed prognosis and survival analysis using survival tools in R package. We then assayed the role of the differentially expressed lncRNAs, AC012213.3 (ENSG00000266289), in cancer cell lines. Quantitative real-time PCR and Western blot analysis were performed to evaluate the expression of the gene in the cell lines and then assessed its role in the progression of breast cancer using cell proliferation (CCK8 and colony formation assays), migration, invasion (transwell and wound-healing assays) and apoptotic (flow cytometry) assays.

Results

Our data showed high expression of lncRNA AC012213.3 in breast cancer tissues and cell lines. The high expression of the AC012213.3 was associated with the worse prognosis and clinical features. Besides, in vitro assays demonstrated that downregulation of AC012213.3 suppresses the proliferation and invasion of breast cancer cells. Further analysis showed that RAD54B is a downstream AC012213.3 target gene and was upregulated in breast cancer. Interestingly, RAD54B expression was associated with shorter survival in breast cancer. In addition, AC012213.3 was shown to facilitate breast cancer progression through the RAD54B/PI3K/AKT axis.

Conclusion

Taken together, our data demonstrated that lncRNA AC012213.3 is upregulated in breast cancer and could enhance breast cancer progression through RAD54B/PI3K/AKT axis.

Discrete roles for Rad54 and Rdh54 during homologous recombination

Rad54 and Rdh54 are Snf2 DNA motor proteins that function during maintenance of genomic integrity. Though highly related, Rad54 and Rdh54 have different biochemical and genetic functions during maintenance of genomic integrity. Rad54 functions primarily during the homology search and strand invasion steps of homologous recombination, while Rdh54 appears to play a minor role in these processes. More recently it has been shown that Rdh54 functions as a pathway branch point at HR intermediates, and as has a role in cell cycle recovery. Here we will explore recent advances that have improved our understanding of the role these two DNA motor proteins play during DNA repair.

Susceptibility to DNA damage caused by abrogation of Rad54 homolog B: A putative mechanism for chemically induced cleft palate

Exposure to environmental toxicants such as all-trans retinoic acid (atRA) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may cause cleft palate (CP), which process is related to DNA damage. Rad54B, an important DNA damage repaired protein, has been proved to be associated with non-syndromic cleft lip with palate (NSCLP). In the present study, we sought to clarify the role of Rad54B in palatal development and environment-induced CP. atRA (100 mg/kg) and TCDD (40 μg/kg) were used to induce CP in mice (C57BL/6 J mice). In this study, mouse embryonic heads were collected on embryonic day (E) 13.5∼16.5. The expression level of DNA repair protein Rad54 homolog B (Rad54B) was significantly decreased while those of the DNA double-strand breaks (DSBs) marker γ-H2A.X, apoptosis marker caspase-3 and p53 were significantly increased in the palatal shelves upon exposure to atRA and TCDD relative to the control. Primary mouse embryonic palatal mesenchymal cells (MEPMs) were cultured and transfected with siRNA or adenovirus in vitro to knock down or increase the level of Rad54B. Rad54B knockdown resulted in increased cellular S-phase arrest and apoptosis as well as decreased cell proliferation. Rad54B overexpression also increased apoptosis and reduced cell proliferation. Western blotting was used to detect the level of γ-H2A.X in transfected cells stimulated with etoposide (ETO, a DSBs inducer), and after 5 μM ETO stimulation of transfected MEPMs, the expression of γ-H2A.X was increased in Rad54B-knockdown cells. The expression of Mdm2, Mdmx and p53 with changes in Rad54B was also detected and coimmunoprecipitation was performed to analyze the combination of Mdm2 and p53 when Rad54B was changed in MEPMs. Knockdown of Rad54B inhibited the expression of Mdm2 and Mdmx, while the level of p53 increased. The coimmunoprecipitation results showed a decreased combination of Mdm2 and p53 when Rad54B was knocked down. Therefore, Rad54B can regulate the cell cycle, proliferation, and apoptosis of MEPMs. The loss of Rad54B increased the sensitivity of MEPMs to DSBs inducers, promoted apoptosis, and suppressed the proliferation of MEPMs by inhibiting the degradation of p53. Taken together, these findings suggest that Rad54B may play a key regulatory role in environment-induced CP.

A Comprehensive Analysis of Alterations in DNA Damage Repair Pathways Reveals a Potential Way to Enhance the Radio-Sensitivity of Esophageal Squamous Cell Cancer

Esophageal squamous cell cancer (ESCC) is a common malignancy with a poor 5-year overall survival in China. Altered DNA damage repair (DDR) pathways are associated with a predisposition to cancer and contribute to therapeutic response and resistance in cancers. However, alterations of DDR pathway genes in ESCC are still largely unknown. In this study, we employed genome sequencing data of 192 samples, comparative genomic hybridization data of 123 cases, and gene expression microarray data of 119 patients to firstly perform a comprehensive analysis of the gene alterations of 7 DDR pathways in ESCC. Gene mutations and copy number variations (CNVs) were observed in all 7 DDR pathways, and especially, CNVs were the dominant alteration types. Compared with other pathways, two DNA double-strand break (DSB) repair pathways homologous recombination (HR) and non-homologous end joining (NHEJ), carried significant gene mutations and CNVs especially gene amplifications. Most genes including RAD54B, NBS1, RAD51B, and PRKDC were significantly amplified and over-expressed in ESCC. Amplification and high expression of DSB repair pathway genes were associated with poorer overall survival. Gene set variation analysis further showed that DSB repair pathways were up-regulated in ESCC. Besides, we firstly demonstrated that combination of mirin and NU7441, two inhibitors for HR and NHEJ respectively, with ionizing radiation treatment significantly enhanced DSBs, reduced clonogenic cell survival, inhibited cell proliferation, and promoted cell apoptosis in ESCC cells with DSB pathway gene amplification. These findings suggest that DSB repair pathways were significantly altered in ESCC and inhibiting DSB repair pathways might enhance the radio-sensitivity of ESCC with DSB repair up-regulation.