Phosphorylation of H2A.XTyr39positively regulates DNA damage response and is linked to cancer progression

Polyploid giant cancer cells induced by Docetaxel exhibit a senescence phenotype with the expression of stem cell markers in ovarian cancer cells

Docetaxel (Doc) plays a crucial role in clinical antineoplastic practice. However, it is continuously documented that tumors frequently develop chemoresistance and relapse, which may be related to polyploid giant cancer cells (PGCCs). The aim of this study was investigate the formation mechanism and biological behavior of PGCCs induced by Doc. Ovarian cancer cells were treated with Doc, and then the effect of Doc on cellular viability was evaluated by MTT assay and microscopic imaging analysis. The biological properties of PGCCs were further evaluated by Hoechst 33342 staining, cell cycle and DNA content assay, DNA damage response (DDR) signaling detection, β-galactosidase staining, mitochondrial membrane potential detection, and reverse transcription-quantitative polymerase chain reaction. The results indicated that Doc reduced cellular viability; however, many cells were still alive, and were giant and polyploid. Doc increased the proportion of cells stayed in the G2/M phase and reduced the number of cells. In addition, the expression of γ-H2A.X was constantly increased after Doc treatment. PGCCs showed senescence-associated β-galactosidase activity and an increase in the monomeric form of JC-1. The mRNA level of octamer-binding transcription factor 4 (OCT4) and krüppel-like factor 4 (KLF4) was significantly increased in PGCCs. Taken together, our results suggest that Doc induces G2/M cell cycle arrest, inhibits the proliferation and activates persistent DDR signaling to promote the formation of PGCCs. Importantly, PGCCs exhibit a senescence phenotype and express stem cell markers.

Roles of Histone H2A Variants in Cancer Development, Prognosis, and Treatment

Histones are nuclear proteins essential for packaging genomic DNA and epigenetic gene regulation. Paralogs that can substitute core histones (H2A, H2B, H3, and H4), named histone variants, are constitutively expressed in a replication-independent manner throughout the cell cycle. With specific chaperones, they can be incorporated to chromatin to modify nucleosome stability by modulating interactions with nucleosomal DNA. This allows the regulation of essential fundamental cellular processes for instance, DNA damage repair, chromosomal segregation, and transcriptional regulation. Among all the histone families, histone H2A family has the largest number of histone variants reported to date. Each H2A variant has multiple functions apart from their primary role and some, even be further specialized to perform additional tasks in distinct lineages, such as testis specific shortH2A (sH2A). In the past decades, the discoveries of genetic alterations and mutations in genes encoding H2A variants in cancer had revealed variants' potentiality in driving carcinogenesis. In addition, there is growing evidence that H2A variants may act as novel prognostic indicators or biomarkers for both early cancer detection and therapeutic treatments. Nevertheless, no studies have ever concluded all identified variants in a single report. Here, in this review, we summarize the respective functions for all the 19 mammalian H2A variants and their roles in cancer biology whilst potentiality being used in clinical setting.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

Ubiquitin-Specific Protease 6 n-Terminal-like Protein (USP6NL) and the Epidermal Growth Factor Receptor (EGFR) Signaling Axis Regulates Ubiquitin-Mediated DNA Repair and Temozolomide-Resistance in Glioblastoma

Glioblastoma multiforme (GBM) is the most malignant glioma, with a 30–60% epidermal growth factor receptor (EGFR) mutation. This mutation is associated with unrestricted cell growth and increases the possibility of cancer invasion. Patients with EGFR-mutated GBM often develop resistance to the available treatment modalities and higher recurrence rates. The drug resistance observed is associated with multiple genetic or epigenetic factors. The ubiquitin-specific protease 6 N-terminal-like protein (USP6NL) is a GTPase-activating protein that functions as a deubiquitinating enzyme and regulates endocytosis and signal transduction. It is highly expressed in many cancer types and may promote the growth and proliferation of cancer cells. We hypothesized that USP6NL affects GBM chemoresistance and tumorigenesis, and that its inhibition may be a novel therapeutic strategy for GBM treatment. The USP6NL level, together with EGFR expression in human GBM tissue samples and cell lines associated with therapy resistance, tumor growth, and cancer invasion, were investigated. Its pivotal roles and potential mechanism in modulating tumor growth, and the key mechanism associated with therapy resistance of GBM cells, were studied, both in vitro and in vivo. Herein, we found that deubiquitinase USP6NL and growth factor receptor EGFR were strongly associated with the oncogenicity and resistance of GBM, both in vitro and in vivo, toward temozolomide, as evidenced by enhanced migration, invasion, and acquisition of a highly invasive and drug-resistant phenotype by the GBM cells. Furthermore, abrogation of USP6NL reversed the properties of GBM cells and resensitized them toward temozolomide by enhancing autophagy and reducing the DNA damage repair response. Our results provide novel insights into the probable mechanism through which USP6NL/EGFR signaling might suppress the anticancer therapeutic response, induce cancer invasiveness, and facilitate reduced sensitivity to temozolomide treatment in GBM in an autolysosome-dependent manner. Therefore, controlling the USP6NL may offer an alternative, but efficient, therapeutic strategy for targeting and eradicating otherwise resistant and recurrent phenotypes of aggressive GBM cells.

Acute aerobic exercise-conditioned serum reduces colon cancer cell proliferation through IL-6-induced regulation of DNA damage in vitro

Epidemiological evidence shows that regular physical activity is associated with reduced risk of primary and recurrent colon cancer. However, the underlying mechanisms of action are poorly understood. We evaluated the effects of stimulating a human colon cancer cell line (LoVo) with human serum collected before and after an acute exercise bout vs non-exercise control serum on cancer cell proliferation. We also measured exercise-induced changes in serum cytokines and intracellular protein expression to explore potential biological mechanisms. Blood samples were collected from 16 men with lifestyle risk factors for colon cancer (age ≥ 50 years; body mass index ≥25 kg/m² ; physically inactive) before and immediately after an acute bout of moderate-intensity aerobic interval exercise (6 x 5 min intervals at 60% heart rate reserve) and a non-exercise control condition. Stimulating LoVo cells with serum obtained immediately after exercise reduced cancer cell proliferation compared with control (-5.7%; P = 0.002). This was accompanied by a decrease in LoVo cell γ-H2AX expression (-24.6%; P = 0.029), indicating a reduction in DNA damage. Acute exercise also increased serum IL-6 (24.6%, P = 0.002). Furthermore, stimulating LoVo cells with recombinant IL-6 reduced γ-H2AX expression (β = -22.7%; P < 0.001) and cell proliferation (β = -5.3%; P < 0.001) in a linear dose-dependent manner, mimicking the effect of exercise. These findings suggest that the systemic responses to acute aerobic exercise inhibit colon cancer cell proliferation in vitro, and this may be driven by IL-6-induced regulation of DNA damage and repair. This mechanism of action may partly underlie epidemiological associations linking regular physical activity with reduced colon cancer risk. This article is protected by copyright. All rights reserved.

RBM6 splicing factor promotes homologous recombination repair of double-strand breaks and modulates sensitivity to chemotherapeutic drugs

RNA-binding proteins regulate mRNA processing and translation and are often aberrantly expressed in cancer. The RNA-binding motif protein 6, RBM6, is a known alternative splicing factor that harbors tumor suppressor activity and is frequently mutated in human cancer. Here, we identify RBM6 as a novel regulator of homologous recombination (HR) repair of DNA double-strand breaks (DSBs). Mechanistically, we show that RBM6 regulates alternative splicing-coupled nonstop-decay of a positive HR regulator, Fe65/APBB1. RBM6 knockdown leads to a severe reduction in Fe65 protein levels and consequently impairs HR of DSBs. Accordingly, RBM6-deficient cancer cells are vulnerable to ATM and PARP inhibition and show remarkable sensitivity to cisplatin. Concordantly, cisplatin administration inhibits the growth of breast tumor devoid of RBM6 in mouse xenograft model. Furthermore, we observe that RBM6 protein is significantly lost in metastatic breast tumors compared with primary tumors, thus suggesting RBM6 as a potential therapeutic target of advanced breast cancer. Collectively, our results elucidate the link between the multifaceted roles of RBM6 in regulating alternative splicing and HR of DSBs that may contribute to tumorigenesis, and pave the way for new avenues of therapy for RBM6-deficient tumors.

NTNG1 Modulates Cisplatin Resistance in Epithelial Ovarian Cancer Cells via the GAS6/AXL/Akt Pathway

Cisplatin resistance is a challenge in the treatment of epithelial ovarian cancer. Here, clinical data showed that the level of netrin-G1 (NTNG1) in cisplatin-resistant cancer was higher than that in cisplatin-sensitive cancer (2.2-fold, p = 0.005); patients with a high NTNG1 level in cancer tissues had shorter progression-free survival (11.0 vs. 25.0 months, p = 0.010) and platinum-free interval (5.0 vs. 20.0 months, p = 0.021) compared with patients with a low level. Category- or stage-adjusted analyses demonstrated that the association between the NTNG1 level and prognosis occurred in type II or FIGO III/IV cancer. The basal level of NTNG1 in SKOV3/DDP cells (a cisplatin-resistant subline) was higher than that in SKOV3 cells; therefore, NTNG1 was overexpressed in SKOV3 cells, or silenced in SKOV3/DDP cells. Knocking in NTNG1 reduced the action of cisplatin to decrease cell death and apoptosis of SKOV3 cells, accompanied by upregulation of p-AXL, p-Akt and RAD51; however, opposite effects were observed in SKOV3/DDP cells after knocking down NTNG1. Co-immunoprecipitation demonstrated that NTNG1 bound GAS6/AXL. Silencing NTNG1 enhanced cisplatin effects in vivo, decreasing tumor volume/mass. These data suggested that a high NTNG1 level can result in cisplatin resistance in ovarian cancer cells via the GAS6/AXL/Akt pathway and that NTNG1 may be a useful target to overcome resistance.

Effect of supersaturated oxygen emulsion treatment on chloropicrin-induced chemical injury in ex vivo rabbit cornea

With a possibility for the use of chemical weapons in battlefield or in terrorist activities, effective therapies against the devastating ocular injuries, from their exposure, are needed. Oxygen plays a vital role in ocular tissue preservation and wound repair. We tested the efficacy of supersaturated oxygen emulsion (SSOE) in reducing ex vivo corneal and keratocyte injury from chloropicrin (CP). CP, currently used as a pesticide, is a chemical threat agent like the vesicating mustard agents and causes severe corneal injury. Since our previous study in human corneal epithelial cells showed the treatment potential of SSOE (55 %), we further tested its efficacy in an ex vivo CP-induced rabbit corneal injury model. Corneas were exposed to CP (700 nmol) for 2 h, washed and cultured with or without SSOE for 24 h or 96 h. At 96 h post CP exposure, SSOE treatment presented a healing tendency of the corneal epithelial layer, and abrogated the CP-induced epithelial apoptotic cell death. SSOE treatment also reduced the CP induced DNA damage (H2A.X phosphorylation) and inflammatory markers (e.g. MMP9, IL-21, MIP-1β, TNFα). Further examination of the treatment efficacy of SSOE alone or in combination with other therapies in in vivo cornea injury models for CP and vesicants, is warranted.

Akt regulates RSK2 to alter phosphorylation level of H2A.X in breast cancer

Histone H2AX (H2A.X) is a variant of the histone H2A family. Phosphorylation of H2A.X is a marker of DNA strand breaks and the presence or absence of H2A.X is closely related to tumor susceptibility and drug resistance. The present study found that the activity of the serine/threonine kinase Akt was negatively associated with H2A.X phosphorylated at the Ser16 site (H2A.X S16ph), but the mechanism of the inverse relationship remains elusive. The aim of the present study was to elucidate the mechanism of action between Akt and H2A.X S16ph and the exact role of this mechanism. Western blot analysis was performed to detect the regulatory association between p-Akt and H2A.X S16ph/p-RSK2, and immunoprecipitation and chromatin immunoprecipitation were performed to prove that Akt, RSK2 and H2A.X combine and interact in human breast cancer cells. The changes of cellular proliferation and migration induced by the interaction of Akt, RSK2 and H2A.X was determined by MTT, soft agar colony formation and cell migration experiments. The effect of interaction of Akt, RSK2 and H2A.X on cancer-promoting genes, such as PSAT-1 was determined via reverse transcription-quantitative PCR analysis. The current study indicated that the serine/threonine kinase ribosomal S6 kinase 2 (RSK2) as a kinase of H2A.X could be phosphorylated by Akt at Ser19 site. Moreover, Akt positively regulated the phosphorylation of RSK2 to inhibit phosphorylation of H2A.X, thereby affecting the affinity between RSK2 and substrate histone, promoting the survival and migration of breast cancer cells. In conclusion, Akt-mediated phosphorylation of RSK2 regulated the phosphorylation of H2A.X, thereby promoting oncogenic activity. This finding provides new insights to understand the pathogenesis and treatment mechanisms of breast cancer.

Co‑expression of tissue kallikrein 1 and tissue inhibitor of matrix metalloproteinase 1 improves myocardial ischemia‑reperfusion injury by promoting angiogenesis and inhibiting oxidative stress

Myocardial ischemia/reperfusion (I/R) injury is a serious complication of reperfusion therapy for myocardial infarction. At present, there is not an effective treatment strategy available for myocardial I/R. The present study aimed to investigate the effects of human tissue kallikrein 1 (hTK1) and human tissue inhibitors of matrix metalloproteinase 1 (hTIMP1) gene co‑expression on myocardial I/R injury. A rat model of myocardial I/R injury and a cell model with hypoxia/reoxygenation (H/R) treatment in cardiac microvascular endothelial cells (CMVECs) were established, and treated with adenovirus (Ad)‑hTK1/hTIMP1. Following which, histological and triphenyl‑tetrazolium‑chloride staining assays were performed. Cardiac function was tested by echocardiographic measurement. The serum levels of oxidative stress biomarkers in rats and the intracellular reactive oxygen species (ROS) levels in CMVECs were measured. Additionally, experiments, including immunostaining, reverse transcription‑quantitative PCR, western blotting, and MTT, wound healing, Transwell and tube formation assays were also performed. The results of the present study demonstrated that Ad‑hTK1/hTIMP1 alleviated myocardial injury and improved cardiac function in myocardial I/R model rats. Ad‑hTK1/hTIMP1 also significantly enhanced microvessel formation, decreased matrix metalloproteinase (MMP)2 and MMP9 expression, and reduced oxidative stress in myocardial I/R model rats. Furthermore, Ad‑hTK1/hTIMP1 significantly enhanced proliferation, migration and tube formation in H/R‑treated CMVECs. Additionally, Ad‑hTK1/hTIMP1 significantly decreased intracellular ROS production and γ‑H2A.X variant histone expression levels in H/R‑treated CMVECs. In conclusion, the results of the present study demonstrated that co‑expression of hTK1 and hTIMP1 genes displayed significant protective effects on myocardial I/R injury by promoting angiogenesis and suppressing oxidative stress; therefore, co‑expression of hTK1 and hTIMP1 may serve as a potential therapeutic strategy for myocardial I/R injury.

Mechanisms of Action for Small Molecules Revealed by Structural Biology in Drug Discovery

Small-molecule drugs are organic compounds affecting molecular pathways by targeting important proteins. These compounds have a low molecular weight, making them penetrate cells easily. Small-molecule drugs can be developed from leads derived from rational drug design or isolated from natural resources. A target-based drug discovery project usually includes target identification, target validation, hit identification, hit to lead and lead optimization. Understanding molecular interactions between small molecules and their targets is critical in drug discovery. Although many biophysical and biochemical methods are able to elucidate molecular interactions of small molecules with their targets, structural biology is the most powerful tool to determine the mechanisms of action for both targets and the developed compounds. Herein, we reviewed the application of structural biology to investigate binding modes of orthosteric and allosteric inhibitors. It is exemplified that structural biology provides a clear view of the binding modes of protease inhibitors and phosphatase inhibitors. We also demonstrate that structural biology provides insights into the function of a target and identifies a druggable site for rational drug design.

KRas-ERK signalling promotes the onset and maintenance of uveal melanoma through regulating JMJD6-mediated H2A.X phosphorylation at tyrosine 39

Since DNA damage is a first incident occurred during a tumour attack, it is rational that histone H2A.X phosphorylation on tyrosine 39 (H2A.X^Y39ph) may act as a tumour-relevant factor. This study was aimed to test the authenticity of the hypothesis. Uveal melanoma MP65 cells were transfected for expression of KRas mutated. H2A.X phosphorylation and ERK1/2 was measured, and transwell experiment was performed to examine the consequents of H2A.X^Y39ph on MP65 cells developing and migration. Regulatory relationship between H2A.X^Y39ph and ERK1/2 downstream genes were measured. Moreover, whether JMJD6 and MDM2 are involved in H2A.X phosphorylation was studied. Mutation of Ras activated ERK1/2 signalling and inhibited H2A.X phosphorylation at Y39. Silence of H2A.X^Y39ph contributed to the regulation of MP65 cells growth, migration and transcription of ERK1/2 downstream genes, including CYR61, IGFBP3, WNT16B, NT5E, GDF15 and CARD16. The repressed H2A.X phosphorylation through Ras-ERK1/2 signalling might be through MDM2-mediated JMJD6 degradation. Our study suggested that Ras-ERK1/2 signalling inhibited H2A.X phosphorylation at Y39, which led to the uncontrolled developing and migration of uveal melanoma cells. In addition, H2A.X phosphorylation was mediated possibly through JMJD6 which could be degraded by MDM2.

Eya2 promotes cell cycle progression by regulating DNA damage response during vertebrate limb regeneration

How salamanders accomplish progenitor cell proliferation while faithfully maintaining genomic integrity and regenerative potential remains elusive. Here we found an innate DNA damage response mechanism that is evident during blastema proliferation (early- to late-bud) and studied its role during tissue regeneration by ablating the function of one of its components, Eyes absent 2. In eya2 mutant axolotls, we found that DNA damage signaling through the H2AX histone variant was deregulated, especially within the proliferating progenitors during limb regeneration. Ultimately, cell cycle progression was impaired at the G1/S and G2/M transitions and regeneration rate was reduced. Similar data were acquired using acute pharmacological inhibition of the Eya2 phosphatase activity and the DNA damage checkpoint kinases Chk1 and Chk2 in wild-type axolotls. Together, our data indicate that highly-regenerative animals employ a robust DNA damage response pathway which involves regulation of H2AX phosphorylation via Eya2 to facilitate proper cell cycle progression upon injury.

Jumonji domain-containing protein 6 protein and its role in cancer

The jumonji domain‐containing protein 6 (JMJD6) is a Fe(II)‐ and 2‐oxoglutarate (2OG)‐dependent oxygenase that catalyses lysine hydroxylation and arginine demethylation of histone and non‐histone peptides. Recently, the intrinsic tyrosine kinase activity of JMJD6 has also been reported. The JMJD6 has been implicated in embryonic development, cellular proliferation and migration, self‐tolerance induction in the thymus, and adipocyte differentiation. Not surprisingly, abnormal expression of JMJD6 may contribute to the development of many diseases, such as neuropathic pain, foot‐and‐mouth disease, gestational diabetes mellitus, hepatitis C and various types of cancer. In the present review, we summarized the structure and functions of JMJD6, with particular emphasis on the role of JMJD6 in cancer progression.

(S)-10-Hydroxycamptothecin Inhibits Esophageal Squamous Cell Carcinoma Growth In Vitro and In Vivo Via Decreasing Topoisomerase I Enzyme Activity

Topoisomerase (TOP) I plays a major role in the process of supercoiled DNA relaxation, thereby facilitating DNA replication and cell cycle progression. The expression and enzymatic activity of TOP I is positively correlated with tumor progression. Although the anticancer activity of (S)-10-Hydroxycamptothecin (HCPT), a TOP I specific inhibitor, has been reported in various cancers, the effect of HCPT on esophageal cancer is yet to be examined. In this study, we investigate the potential of HCPT to inhibit the growth of ESCC cells in vitro and verify its anti-tumor activity in vivo by using a patient-derived xenograft (PDX) tumor model in mice. Our study revealed the overexpression of TOP I in ESCC cells and treatment with HCPT inhibited TOP I enzymatic activity at 24 h and decreased expression at 48 h and 72 h. HCPT also induced DNA damage by increasing the expression of H2A.X^S139. HCPT significantly decreased the proliferation and anchorage-independent growth of ESCC cells (KYSE410, KYSE510, KYSE30, and KYSE450). Mechanistically, HCPT inhibited the G2/M phase cell cycle transition, decreased the expression of cyclin B1, and elevated p21 expression. In addition, HCPT stimulated ESCC cells apoptosis, which was associated with elevated expression of cleaved PARP, cleaved caspase-3, cleaved caspase-7, Bax, Bim, and inhibition of Bcl-2 expression. HCPT dramatically suppressed PDX tumor growth and decreased the expression of Ki-67 and TOP I and increased the level of cleaved caspase-3 and H2A.X^S139 expression. Taken together, our data suggested that HCPT inhibited ESCC growth, arrested cell cycle progression, and induced apoptosis both in vitro and in vivo via decreasing the expression and activity of TOP I enzyme.

Livin promotes colon cancer progression by regulation of H2A.XY39ph via JMJD6

Livin is an important member of the human inhibitor of apoptosis proteins (IAPs) family. IAPs are proteins with antiapoptotic abilities, and their functions are different from the Bcl-2 (B-cell lymphoma-2) family proteins. However, the precise role of Livin in colon cancer progression remains unclear. The purpose of this study is to assess the effect of overexpression Livin in colon cancer cells and to examine its molecular mechanism. We demonstrated that Livin induced a colon cancer phenotype, including proliferation and migration, by regulating H2A.X^Y39ph (histone family 2A variant (H2AX) phosphorylated on the 39th serine site). We elucidated that Livin degraded Jumonji-C domain-containing 6 protein (JMJD6), which was mediated by the proteasome murine double minute 2 (MDM2), thereby regulating H2A.X^Y39ph. Above all, the overexpression of JMJD6 recovered H2A.X^Y39ph in colon cancer cells with a high level of Livin, thus inhibiting colon cancer malignancy progression. These results reveal a previously unrecognized role for Livin in regulating the tumor-initiating capacity in colon cancer and provide a novel treatment strategy in cancer via the interruption of H2A.X^Y39ph function and the interaction between H2A.X^Y39ph and JMJD6.

Structural and Functional Analyses of an Allosteric EYA2 Phosphatase Inhibitor That Has On-Target Effects in Human Lung Cancer Cells

EYA proteins (EYA1-4) are critical developmental transcriptional cofactors that contain an EYA domain (ED) harboring Tyr phosphatase activity. EYA proteins are largely downregulated after embryogenesis but are reexpressed in cancers, and their Tyr phosphatase activity plays an important role in the DNA damage response and tumor progression. We previously identified a class of small-molecule allosteric inhibitors that specifically inhibit the Tyr phosphatase activity of EYA2. Herein, we determined the crystal structure of the EYA2 ED in complex with NCGC00249987 (a representative compound in this class), revealing that it binds to an induced pocket distant from the active site. NCGC00249987 binding leads to a conformational change of the active site that is unfavorable for Mg²⁺ binding, thereby inhibiting EYA2's Tyr phosphatase activity. We demonstrate, using genetic mutations, that migration, invadopodia formation, and invasion of lung adenocarcinoma cells are dependent on EYA2 Tyr phosphatase activity, whereas growth and survival are not. Further, we demonstrate that NCGC00249987 specifically targets migration, invadopodia formation, and invasion of lung cancer cells, but that it does not inhibit cell growth or survival. The compound has no effect on lung cancer cells carrying an EYA2 F290Y mutant that abolishes compound binding, indicating that NCGC00249987 is on target in lung cancer cells. These data suggest that the NCGC00249987 allosteric inhibitor can be used as a chemical probe to study the function of the EYA2 Tyr phosphatase activity in cells and may have the potential to be developed into an antimetastatic agent for cancers reliant on EYA2's Tyr phosphatase activity.

K-ras-ERK1/2 down-regulates H2A.XY142ph through WSTF to promote the progress of gastric cancer

Background

Histone H2AX phosphorylation at the site of Tyr-142 can participates in multiple biological progressions, which is including DNA repair. Ras pathway is closely involved in human cancers. Our study investigated the effects of Ras pathway via regulating H2AX.^Y142ph.

Methods

Gastric cancer cell line SNU-16 and MKN1 cells were transfected with Ras for G12D and T35S site mutation. The phosphorylation of H2A.X^Y142 and ERK1/2, WSTF and MDM2 was detected by western blot. Cell viability, cell colonies and migration was analyzed by MTT assay, soft-agar colony formation assay, and Transwell assay, respectively. The expression of Ras pathway related downstream factors, EYA3 and WSTF was detected by qRT-PCR. The relationship between Ras and downstream factors were detected by ChIP. The cell cycle progression was measured by flow cytometry.

Results

Ras^G12D/T35V transection decreased the phosphorylation of H2A.X^Y142 and activated phosphorylation of ERK-1/2. H2A.X^Y142 inhibited cell viability, colonies and migration. H2A.X^Y142ph altered the expression of Ras downstream factors. CHIP assay revealed that Ras^G12D/T35V could bind to the promoters of these Ras pathway downstream factors. Silence of EYA3 increased H2A.X^Y142ph and inhibited cell viability, migration and percent cells in S stage. Furthermore, silence of EYA3 also changed the downstream factors expression. WSTF and H2A.X^Y142ph revealed the similar trend and MDM2 on the opposite.

Conclusion

Ras/ERK signal pathway decreased H2A.X^Y142ph and promoted cell growth and metastasis. This Ras regulation process was down-regulated by the cascade of MDM2-WSTF-EYA3 to decrease H2A.X^Y142ph in SNU-16 cells.

JMJD6 regulates histone H2A.X phosphorylation and promotes autophagy in triple-negative breast cancer cells via a novel tyrosine kinase activity

Overexpression of Jumonji domain-containing 6 (JMJD6) has been reported to be associated with more aggressive breast cancer characteristics. However, the precise role of JMJD6 in breast cancer development remains unclear. Here, we demonstrate that JMJD6 has intrinsic tyrosine kinase activity and can utilize ATP and GTP as phosphate donors to phosphorylate Y39 of histone H2A.X (H2A.X^Y39ph). High JMJD6 levels promoted autophagy in triple negative breast cancer (TNBC) cells by regulating the expression of autophagy-related genes. The JMJD6-H2A.X^Y39ph axis promoted TNBC cell growth via the autophagy pathway. We show that combined inhibition of JMJD6 kinase activity and autophagy efficiently decreases TNBC growth. Together, these findings suggest an effective strategy for TNBC treatment.

Eyes absent homologue 2 predicts a favorable prognosis in colorectal cancer

Purpose

Eyes absent homologue 2 (EYA2), which functions as a transcription activator and phosphatase, plays an important role in several types of cancer. However, the impact of EYA2 in colorectal cancer (CRC) remains elusive.

Patients and methods

We evaluated the significance of EYA2 expression in the development and progression of CRC in a large cohort, including 922 CRC cases. EYA2 protein expression was determined via immunohistochemistry in colorectal tissues. The correlation between EYA2 expression and CRC occurrence was investigated in tumor tissue and the adjacent normal tissues. Factors contributing to CRC prognosis were evaluated using Kaplan–Meier and Cox model analyses.

Results

EYA2 expression was progressively lower in the adjacent normal tissue, adenomas, primary tumor and the metastatic CRC (all P<0.05). Furthermore, EYA2 expression had significant associations with disease stage, differentiation grade, and number of resected lymph nodes (all P<0.001). Compared with patients with EYA2-high tumors, those with EYA2-low tumors had shorter disease-free survival (hazard ratio [HR], 2.347; 95% CI, 1.665–3.308) and disease-specific survival (HR, 3.560; 95% CI, 2.055–6.167) in multivariate Cox analysis, after adjusting confounding factors such as tumor-node-metastasis stage and grade. In particular, patients with stage II or III EYA2-low CRC might be harmed by postoperative chemotherapy.

Conclusion

EYA2 expression was generally reduced in CRC. Higher EYA2 expression can predict a more favorable prognosis for CRC.

Low-dose decitabine enhances chidamide-induced apoptosis in adult acute lymphoblast leukemia, especially for p16-deleted patients through DNA damage

AIM

To investigate the combined action of decitabine (DAC) with chidamide (CS055) on acute lymphoblastic leukemia (ALL) cells.

MATERIALS & METHODS

ALL cell lines as well as primary cells from 17 ALL patients were subjected to different treatments and thereafter cell counting Kit-8 (CCK-8) assay, flow cytometry and western blot were employed to determine IC₅₀, apoptosis and checkpoint kinase 1 and γH2A.X expression.

RESULTS

Low-dose DAC combined with CS055 could effectively kill ALL cells by the reduction of cell viability and induction of apoptosis. This was also observed in primary cells from 17 ALL patients, especially for those with p16 gene deletion. Suppression of checkpoint kinase 1 phosphorylation and upregulation of γH2A.X expression was demonstrated to participate in DAC plus CS055-induced apoptosis.

CONCLUSION

Low-dose DAC could enhance chidamide-induced apoptosis in adult ALL, especially for patients with p16 gene deletion through DNA damage.