Minimal deletion regions in lung squamous cell carcinoma: Association with abnormality of the DNA double-strand break repair genes and their applications on gene identification and prognostic biomarkers

Gas7 attenuates hepatocellular carcinoma progression and chemoresistance through the PI3K/Akt signaling pathway

Growth arrest-specific gene 7 (Gas7) was involved in various cellular functions, although its specific roles and molecular mechanisms in hepatocellular carcinoma (HCC) remained unclear. So the current study was to investigate the role of Gas7 in HCC. Our findings revealed that Gas7 was downregulated in various HCC cell lines and low Gas7 expression was associated with decreased overall survival in patients with HCC. Additionally, our functional assays showed that Gas7 inhibited cell proliferation and migration, induced cell cycle arrest, apoptosis, and autophagy, and enhanced oxaliplatin sensitivity by inhibiting the PI3K/Akt signaling pathway. We also observed that transcription factorSp1 was responsible for inhibiting Gas7. These findings provide insights into the role and elucidated a potential mechanism of Gas7 in HCC progression and metastasis. It was also observed that the Sp1/Gas7/PI3K/Akt axis was critical for malignant phenotype and oxaliplatin sensitivity in HCC. Therefore, Gas7 can be considered as a prognostic predictor and therapeutic target for HCC.

miR-362-5p promotes cell proliferation and cell cycle progression by targeting GAS7 in acute myeloid leukemia

Recently, miR-362-5p has attracted special interest as a novel prognostic predictor in acute myeloid leukemia (AML). However, its biological function and underlying molecular mechanism in AML remain to be further defined. Herein, we found that a significant increase in miR-362-5p expression was observed in AML patients and cell lines using quantitative real-time PCR. The expression of miR-362-5p was altered in THP-1 and HL-60 cells by transfecting with miR-362-5p mimic or inhibitor. A series of experiments showed that inhibition of miR-362-5p expression significantly suppressed cell proliferation, induced G0/G1 phase arrest and attenuated tumor growth in vivo. On the contrary, ectopic expression of miR-362-5p resulted in enhanced cell proliferation, cell cycle progression and tumor growth. Moreover, growth arrest-specific 7 (GAS7) was confirmed as a direct target gene of miR-362-5p and was negatively modulated by miR-362-5p. GAS7 overexpression imitated the tumor suppressive effect of silenced miR-362-5p on THP-1 cells. Furthermore, miR-362-5p knockdown or GAS7 overexpression obviously down-regulated the expression levels of PCNA, CDK4 and cyclin D1, but up-regulated p21 expression. Collectively, our findings demonstrate that miR-362-5p exerts oncogenic effects in AML by directly targeting GAS7, which might provide a promising therapeutic target for AML.

Wild-type p53 upregulates an early onset breast cancer-associated gene GAS7 to suppress metastasis via GAS7-CYFIP1-mediated signaling pathway

The early onset breast cancer patients (age ≤ 40) often display higher incidence of axillary lymph node metastasis, and poorer five-year survival than the late-onset patients. To identify the genes and molecules associated with poor prognosis of early onset breast cancer, we examined gene expression profiles from paired breast normal/tumor tissues, and coupled with Gene Ontology and public data base analysis. Our data showed that the expression of GAS7b gene was lower in the early onset breast cancer patients as compared to the elder patients. We found that GAS7 was associated with CYFIP1 and WAVE2 complex to suppress breast cancer metastasis via blocking CYFIP1 and Rac1 protein interaction, actin polymerization, and β1-integrin/FAK/Src signaling. We further demonstrated that p53 directly regulated GAS7 gene expression, which was inversely correlated with p53 mutations in breast cancer specimens. Our study uncover a novel regulatory mechanism of p53 in early onset breast cancer progression through GAS7-CYFIP1-mediated signaling pathways.

MiR-181a contributes gefitinib resistance in non-small cell lung cancer cells by targeting GAS7

Tyrosine kinase inhibitors (TKIs) exert potent therapeutic efficacy in non-small cell lung cancers (NSCLC) harboring epidermal growth factor receptor (EGFR) activating mutations. However, a major impediment for the effective treatment is the development of drug resistance. Some evidence supports a role for miRNAs in modulating NSCLC TKIs resistance. Here we show that miR-181a is significantly up-regulated in gefitinib-resistant cells compared with gefitinib-sensitive cells. Upregulation of miR-181a caused resistance of gefitinib, whereas downregulation of miR-181a sensitized NSCLC cells to gefitinib. Furthermore, the miR-181a plasma levels were significantly increased in acquired gefitinib resistant NSCLC patients compared with the plasma levels prior to gefitinib treatment in each patient. Bioinformatics analysis and luciferase reporter assay showed that growth arrest-specific 7 (GAS7) was a direct target gene of miR-181a. A significant inverse correlation between the expression of miR-181a and GAS7 was identified in NSCLC tissues. Downregulation of GAS7 expression could antagonize gefitinib re-sensitivity in PC9GR mediated by knockdown of miR-181a via AKT/ERK pathways and epithelial-to-mesenchymal transition markers. Additionally, GAS7 expression was downregulated in a large cohort of NSCLC patients, and a high mRNA level of GAS7 was associated with improved overall survival. Collectively, our findings provide a novel basis for using miR-181a/GAS7-based therapeutic strategies to reverse gefitinib resistance in NSCLC.

Oxaliplatin inhibits proliferation and migration of human hepatocellular carcinoma cells via GAS7C and the N-WASP/FAK/F-actin pathway

The growth arrest-specific gene 7 (GAS7), a member of the growth-arrest-specific family, encodes three protein isoforms (GAS7A, GAS7B, and GAS7C) and plays a potential role in lung cancer as a tumor suppressor gene. In the present study, we found low endogenous expressions of GAS7C mRNA and protein in hepatocellular carcinoma (HCC) cell lines compared with normal liver cells, and that there was a distinct increase of GAS7C expression in HCC cells treated with oxaliplatin. CCK8, apoptosis, and Transwell migration assays showed that cell proliferation and motility of HepG2 and MHCC-97 H cells were inhibited by oxaliplatin, while apoptosis was increased. Interestingly, western blot analysis showed that treatment with oxaliplatin increased GAS7C and N-WASP protein levels and decreased the levels of proteins involved in the fibronectin/integrin/FAK pathway, such as FAK, in both HCC cell lines. In addition, ectopically overexpressed GAS7C obviously inhibited cell proliferation and cell motility. Flow cytometry results showed that overexpression of GAS7C induced apoptosis of HepG2 and MHCC-97 H cells. We further confirmed the correlation between GAS7C and the N-WASP/FAK/F-actin pathway by q-PCR and western blot analysis of in GAS7C-overexpressing HepG2 and MHCC-97 H cells. Inhibition of GAS7C substantially reversed the anti-cancer effect of oxaliplatin and blocked the activity of the N-WASP/FAK/F-actin pathway. Taken together, our results showed that oxaliplatin inhibits HCC cell proliferation and migration ability by up-regulating GAS7C and activating the N-WASP/FAK/F-actin pathway.

Growth-arrest-specific 7C protein inhibits tumor metastasis via the N-WASP/FAK/F-actin and hnRNP U/β-TrCP/β-catenin pathways in lung cancer

Growth-arrest-specific 7 (GAS7) belongs to a group of adaptor proteins that coordinate the actin cytoskeleton. Among human GAS7 isoforms, only GAS7C possesses a Src homology 3 domain. We report here that GAS7C acts as a migration suppressor and can serve as a prognostic biomarker in lung cancer. GAS7C overexpression reduces lung cancer migration, whereas GAS7C knockdown enhances cancer cell migration. Importantly, ectopically overexpressed GAS7C binds tightly with N-WASP thus inactivates the fibronectin/integrin/FAK pathway, which in turn leads to the suppression of F-actin dynamics. In addition, overexpression of GAS7C sequesters hnRNP U and thus decreases the level of β-catenin protein via the β-TrCP ubiquitin-degradation pathway. The anti-metastatic effect of GAS7C overexpression was also confirmed using lung cancer xenografts. Our clinical data indicated that 23.6% (25/106) of lung cancer patients showed low expression of GAS7C mRNA which correlated with a poorer overall survival. In addition, low GAS7C mRNA expression was detected in 60.0% of metastatic lung cancer patients, indicating an association between low GAS7C expression and cancer progression. A significant inverse correlation between mRNA expression and promoter hypermethylation was also found, which suggests that the low level of GAS7C expression was partly due to promoter hypermethylation. Our results provide novel evidence that low GAS7C correlates with poor prognosis and promotes metastasis in lung cancer. Low GAS7C increases cancer cell motility by promoting N-WASP/FAK/F-actin cytoskeleton dynamics. It also enhances β-catenin stability via hnRNP U/β-TrCP complex formation. Therefore, GAS7C acts as a metastasis suppressor in lung cancer.

Systems biology approach to stage-wise characterization of epigenetic genes in lung adenocarcinoma

Background

Epigenetics refers to the reversible functional modifications of the genome that do not correlate to changes in the DNA sequence. The aim of this study is to understand DNA methylation patterns across different stages of lung adenocarcinoma (LUAD).

Results

Our study identified 72, 93 and 170 significant DNA methylated genes in Stages I, II and III respectively. A set of common 34 significant DNA methylated genes located in the promoter section of the true CpG islands were found across stages, and these were: HOX genes, FOXG1, GRIK3, HAND2, PRKCB, etc. Of the total significant DNA methylated genes, 65 correlated with transcription function. The epigenetic analysis identified the following novel genes across all stages: PTGDR, TLX3, and POU4F2. The stage-wise analysis observed the appearance of NEUROG1 gene in Stage I and its re-appearance in Stage III. The analysis showed similar epigenetic pattern across Stage I and Stage III. Pathway analysis revealed important signaling and metabolic pathways of LUAD to correlate with epigenetics. Epigenetic subnetwork analysis identified a set of seven conserved genes across all stages: UBC, KRAS, PIK3CA, PIK3R3, RAF1, BRAF, and RAP1A. A detailed literature analysis elucidated epigenetic genes like FOXG1, HLA-G, and NKX6-2 to be known as prognostic targets.

Conclusion

Integrating epigenetic information for genes with expression data can be useful for comprehending in-depth disease mechanism and for the ultimate goal of better target identification.

[DNA repair pathways and non-small cell lung cancer: clinical perspectives]

The role of DNA repair pathways is to maintain cellular integrity. However, genetic instability is a driving force in the development of tumor cells and many tumors are characterized by the loss of functionality in one or several DNA repair pathways. However, if genetic instability trespasses a certain point, it will induce cell death. Therefore, the dysfunctionality of several DNA repair pathways could represent an Achille's heel for the tumor, if such pathways could be pharmacologically targeted. For instance, the inhibition of PARP1, a protein in the base excision repair pathway (BER) is sufficient to induce cell death in cancer cells bearing BRCA1 or BRCA2 mutations, which are essential proteins in the homologous recombination repair pathway (HR). This phenomenon called "synthetic letality" constitutes recent knowledge and we discuss here the possibility that this strategy might be applied to innovative treatment options in lung cancer. Further, several DNA repair proteins could be used in lung cancer as prognostic and/or predictive biomarkers of response to chemotherapy or radiation. Indeed, specific biomarkers of each DNA repair pathway do exist and could guide oncologists in therapeutic decisions (e.g. ERCC1 and cisplatin). Finally, pharmacologic modulation of DNA repair proteins might also be interesting as it might increase therapeutic efficacy of anticancer strategies (DNA-interacting chemotherapy and radiotherapy). Here, we will present the principal DNA repair pathways and associated biomarkers (ERCC1, MSH2, PARP1 and BRCA1/2), and discuss their status in non-small call lung cancer (NSCLC).

Role of the XRCC5/XRCC6 dimer in carcinogenesis and pharmacogenomics

Over the past few decades, the incidence of cancer has rapidly increased all over the world and cancer remains a major threat to public health. It is believed that cancer results from a series of genetic alterations that lead to the progressive disorder of the normal mechanisms controlling cell proliferation, differentiation, death and/or genomic stability. The response of the cell to genetic injury and its ability to maintain genomic stability by means of a variety of DNA repair mechanisms are therefore essential in preventing tumor initiation and progression. From the same viewpoint, the relative role of DNA repair as a biomarker for prognosis, predictor of drug and therapy responses or indeed as a target for novel gene therapy, is very promising. In this article, we have summarized the studies investigating the association between the XRCC5/XRCC6 dimer and the susceptibility to multiple cancers and discuss its role in carcinogenesis and its potential application to anticancer drug discovery.

Sonic hedgehog signaling protects human hepatocellular carcinoma cells against ionizing radiation in an autocrine manner

PURPOSE

Sonic hedgehog (Shh) signaling is critical to embryogenesis and resistance to chemotherapy. We aimed to examine the role of Shh signaling in the response to radiation of human hepatocellular carcinoma (HCC) cells.

METHODS AND MATERIALS

Response to ionizing radiation therapy (RT) was evaluated by clonogenic assay. Quantitative RT-polymerase chain reaction for patched-1 (PTCH-1) expression was performed. Cytosolic accumulation of Shh and nuclear translocation of Gli-1 were assessed by immunofluorescence. Gli-1 knockdown was done by RNA interference (RNAi). Immunoprecipitation was performed to detect Shh ligand in conditioned medium. Immunofluorescent stain for γ-H2AX was used as an index of DNA double strand breaks (DSB). Expression of proteins related to DNA damage repair was assessed by Western blotting.

RESULTS

We found that Shh ligand could protect human HCC HA22T and Sk-Hep1 cells against RT. In HA22T cells, Shh ligand activated the Shh signaling with upregulation of Shh, PTCH-1, and Gli-1 expression. The nuclear translocation of Gli-1 further supports the activation of Gli-1. The radioprotection by Shh ligand was partly blocked by Shh antibody neutralization and was abolished by Gli-1 RNAi, suggesting a critical role of Shh signaling in radiation resistance. Furthermore, we noted that soluble factors secreted into conditioned medium, either constitutively or responding to radiation, by HA22T or Sk-Hep1 cells protected subsequent culturing cells against RT. Immunoprecipitation shows the presence of Shh peptide in conditioned medium. Intriguingly, antibody neutralization of Shh ligand or knockdown of Gli-1 reversed the radioprotective effect of conditioned medium. Furthermore, Shh ligand reduced the RT-induced phosphorylation of checkpoint kinase 1 and impaired the repair of DNA DSB.

CONCLUSIONS

Activation of Shh signaling protects HCC cells against ionizing radiation in an autocrine manner. Impairment of DNA damage repair might involve mechanism of Shh-induced radioresistance. Targeting Shh signaling pathway may be a novel strategy to enhance the radioresponse of human HCC cells.

Knockdown of growth-arrest-specific gene 7b (gas7b) using short-hairpin RNA desensitizes neuroblastoma cells to cisplatin: Implications for preventing apoptosis of neurons

Efficient control of cell survival and cell proliferation is critical for the development of neuron cells. Earlier, we observed that growth arrest-specific gene 7 (Gas7) plays a role in controlling neuritogenesis in mammals. In the present study, we report that the Gas7b isoform is involved in controlling growth arrest and apoptosis of neuroblastoma cells in response to various stimuli. Accordingly, knockdown of Gas7b using small-hairpin RNA (shRNA) was shown to reduce apoptosis induced either by serum starvation or by the antineoplastic agents cisplatin and nocodazole in human neuroblastoma SH-SY5Y cells. Gas7b knockdown also enhanced the ability of the treated cells to form clones in response to cisplatin. On the other hand, forced expression of Gas7a or Gas7b isoform in mouse neuroblastoma Neuro2A cells, which express a defective Gas7 gene, rendered the cells proapoptotic and vulnerable to cisplatin-induced apoptosis. In addition, Neuro2A cells that overexpressed Gas7 showed a reduced ability to form clones. Overexpression of Gas7 produced similar but less extensive effects in nonneuronal HEK293 cells. Taken together, our observations suggest that Gas7b is involved not only in neuritogenesis but also in the regulation of neuronal cell death.

The relationship between the presence of chromosomal instability and prognosis of squamous cell carcinoma of the lung: fluorescence in situ hybridization analysis of paraffin-embedded tissue from 47 Korean patients

To evaluate the prognostic importance of chromosomal instability (CIN) in squamous cell carcinoma (SCC) of the lung, the relationship between CIN detected by fluorescence in situ hybridization (FISH) and survival in SCC patients was examined. Forty-seven surgical specimens of lung SCC were analyzed. To identify tumors with CIN, p16 and multi-target DNA FISH assays for c-myc, chromosome 6, EGFR, and chromosome 5 (LAVysion, Vysis) were performed on nuclei extracted from paraffin-embedded tumor tissues. Survival rates were compared in terms of age, T factor, N factor, CIN, and smoking status. A sample was defined as CIN-positive if at least four of the five chromosomes were positive. Among the 47 specimens, 9 (19%) were CIN-positive. The overall survival rate was 66%. Overall survival rates were estimated as 33.3% for CIN-positive patients and 76.7% for CIN-negative patients (Hazard ratio 3.47; 95% Confidence interval, 1.25-9.67; P=0.017). In multivariate analysis, the presence of CIN was a predictive factor for survival. CIN-positive based on FISH can be prognostic factor of lung SCC.

SLIT2 attenuation during lung cancer progression deregulates beta-catenin and E-cadherin and associates with poor prognosis

Chromosome 4p15.3 is frequently deleted in late-stage lung cancer. We investigated the significance of the SLIT2 gene located in this region to lung cancer progression. SLIT2 encodes an extracellular glycoprotein that can suppress breast cancer by regulating beta-catenin. In this study, we examined alterations in the structure or expression of SLIT2, its receptor ROBO1, and beta-catenin, along with the AKT/glycogen synthase kinase 3beta (GSK3beta)/beta-transducin repeat-containing protein (betaTrCP) pathway in lung cancer cell lines and patients. Low SLIT2 expression correlated with an upward trend of pathological stage and poorer survival in lung cancer patients. Importantly, SLIT2, betaTrCP, and beta-catenin expression levels predicted postoperative recurrence of lung cancer in patients. Stimulating SLIT2 expression by various methods increased the level of E-cadherin caused by attenuation of its transcriptional repressor SNAI1. Conversely, knocking down SLIT2 expression increased cell migration and reduced cell adhesion through coordinated deregulation of beta-catenin and E-cadherin/SNAI1 in the AKT/GSK3beta/betaTrCP pathway. Our findings indicate that SLIT2 suppresses lung cancer progression, defining it as a novel "theranostic" factor with potential as a therapeutic target and prognostic predictor in lung cancer. Cancer Res; 70(2); 543-51.

Distinct HIC1-SIRT1-p53 loop deregulation in lung squamous carcinoma and adenocarcinoma patients

A HIC1-SIRT1-p53 circular loop in which hypermethylation in cancer 1 (HIC1) represses the transcription of SIRT1 that deacetylates and inactivates p53 thus leading to HIC1 inactivation has been identified in cell and animal models. However, the alteration and prognostic effects of HIC1-SIRT1-p53 circular loop have never been demonstrated in human cancer patients. We examine the HIC1-SIRT1-p53 alterations in 118 lung cancer patients to define their etiological roles in tumorigenesis. We found that patients with lung squamous cell carcinoma with low p53 acetylation and SIRT1 expression mostly showed low HIC1 expression, confirming deregulation of HIC1-SIRT1-p53 circular loop in the clinical model. Interestingly, the expression of deleted in breast cancer 1 (DBC1), which blocks the interaction between SIRT1 deacetylase and p53, led to acetylated p53 in patients with lung adenocarcinoma. However, epigenetic alteration of HIC1 promoter by posttranslational modifications of histones and promoter hypermethylation favoring the compacted chromatin production attenuated the transcriptional induction by acetylated p53. Importantly, lung cancer patients with altered HIC1-SIRT1-p53 circular regulation showed poor prognosis. Our data show the first valid clinical evidence of the deregulation of HIC1-SIRT1-p53 loop in lung tumorigenesis and prognosis. Distinct status of p53 acetylation/deacetylation and HIC1 alteration mechanism result from different SIRT1-DBC1 control and epigenetic alteration in lung squamous cell carcinoma and lung adenocarcinoma.

Lung cancer susceptibility and prognosis associated with polymorphisms in the nonhomologous end-joining pathway genes: a multiple genotype-phenotype study

BACKGROUND

Nonsmall cell lung cancer (NSCLC) frequently exhibits genomic instability, such as high fractional allelic loss (FAL). Genomic instability may result from unrepaired or misrepaired double-strand breaks (DSBs). The authors of this report postulated that polymorphisms in genes of the nonhomologous end-joining (NHEJ) pathway, which is the major DSB repair pathway in mammalian cells, may modulate lung cancer susceptibility and prognosis.

METHODS

Patients with NSCLC (n = 152) and a group of appropriate age-matched and sex-matched controls (n = 162) were subjected to genotype analysis of the NHEJ pathway genes x-ray repair complementing defective repair in Chinese hamster cells 6 (Ku70) (reference single nucleotide polymorphism number [rs] 2267437), x-ray repair complementing defective repair in Chinese hamster cells 5 (Ku80) (rs3835), x-ray repair complementing defective repair in Chinese hamster cells 4 (XRCC4) (rs1805377), and DNA ligase IV (LIG4) (rs1805388). The gene-gene interaction (joint effect), genotype-environmental (ie, smoking) correlation, and genotype-phenotype (ie, FAL) correlation were examined. The Kaplan-Meier method and log-rank tests were used to assess the prognostic effect.

RESULTS

There was a significant association between the XRCC4 and LIG4 genotypes with NSCLC risk in an analysis of individual polymorphism associations, and the risk of NSCLC increased further in a combined analysis of multiple polymorphisms (adjusted odds ratio [OR], 8.74). The patients who had a homozygous variant guanine/guanine genotype of the XRCC4 gene had a poorer prognosis compared with other patients (P = .015). There was a significant difference between the patient smokers and controls for XRCC4 (adjusted OR, 2.67) and LIG4 (adjusted OR, 2.04). In addition, polymorphisms in XRCC4 and LIG4 were linked significantly with patients who had high FAL (adjusted OR, 2.03-3.84).

CONCLUSIONS

To the authors' knowledge, this is the first nested case-control study to demonstrate a significant association between the polymorphisms of genes in the NHEJ pathway and lung cancer susceptibility and prognosis. The results may be useful for risk assessment and disease monitoring of patients with NSCLC.