REC8 is a novel tumor suppressor gene epigenetically robustly targeted by the PI3K pathway in thyroid cancer

REC8 regulates neuroblastoma cell proliferation, migration, invasion, and angiogenesis via STAT3/VEGF signaling

BACKGROUND

Neuroblastoma, one of the most prevalent childhood cancers, is often treated with surgery, radiation, and chemotherapy. However, prognosis and survival are still dismal for children with neuroblastoma at high risk. Consequently, it is vital to identify new and effective treatment targets. As a component of the meiotic cohesion complex, REC8 is involved in a wide range of malignancies. The current work assessed the impact of REC8 knockdown on SH-SY5Y and SK-N-AS neuroblastoma cells and delved into the molecular mechanism behind this effect.

METHODS

Knockdown of REC8 using the small interfering (si) RNA technology, and the results were verified by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot. The Cell Counting Kit-8 (CCK-8) was used to examine cell proliferation, while flow cytometry was used to examine cell cycle progression and apoptosis. Analyses of angiogenesis included tube formation experiments. Transwell tests were used to examine cell migration and invasion.

RESULTS

The data showed that downregulation of the REC8 led to a substantial decrease in cell proliferation by stopping the cell cycle in the G1 phase. REC8 knockdown significantly reduced neuroblastoma cell proliferation, migration, invasion, angiogenesis, induced cell cycle arrest, and enhanced apoptosis. We also discovered that repressing REC8 expression in neuroblastoma cell lines SH-SY5Y and SK-N-AS reduced their ability to activate the STAT3/VEGF signaling pathway.

CONCLUSIONS

Neuroblastoma therapy may benefit from targeting REC8 and its downstream targets.

Promoter hypermethylation and comprehensive regulation of ncRNA lead to the down-regulation of ZNF880, providing a new insight for the therapeutics and research of colorectal cancer

The human genome encodes more than 350 kinds of Krüppel-associated box (KRAB) domain-containing zinc-finger proteins (KZFPs), KRAB-type ZNF transcription factor family (KZNF) plays a vital role in gene regulatory networks. The KZNF family members include a large number of highly homologous genes, gene subtypes and pseudogenes, and their expression has a high degree of tissue specificity and precision. Due to the high complexity of its regulatory network, the KZNF gene family has not been researched in sufficient, and the role of its members in the occurrence of cancer is mostly unexplored. In this study, ZNF880 was significantly associated with overall survival (OS) and disease-free survival (DFS) in colorectal carcinoma (CRC) patients. Low ZNF880 expression resulted in shorter OS and DFS. Combined with Colon adenocarcinoma (COAD) and Rectum adenocarcinoma (READ) data collection in the TCGA database, we found that ZNF880 was significantly down-regulated in CRC. Further analysis of the sequence variation of ZNF880 in CRC showed that ZNF880 accumulated a large number of SNV in the C2H2 domain and KRAB domain, while promoter region of ZNF880 also showed high methylation in COAD and READ. Combined with the Cbioportal and TIMER databases, the expression of mutant ZNF880 was significantly lower in COAD compared to the wild type. Simultaneously, the lncRNA-miRNA-ZNF880 ceRNA regulatory network was constructed through co-expression and miRNAs target gene prediction, demonstrating the precision of the ZNF880 regulatory network. In addition, the decreased expression of ZNF880 caused the significant immune infiltration decreases of CD8 + cells in COAD. In contrast, the immune infiltration of CD4 + cells and macrophages in COAD is positively correlated with ZNF880. Finally, through protein-protein interaction (PPI) network analysis and transcription factor target gene prediction, we screened out the genes most likely to be related to the function of ZNF880. CENPK, IFNGR2, REC8 and ZBTB17 were identified as the most closely functioning genes with ZNF880, which may indicate that ZNF880 has important links with the formation of cell centromere, tumor immunity, cell cycle and other pathways closely related to the occurrence of CRC. These studies show that the down-regulation of ZNF880 gene is closely related to CRC, and the targeted change of the expression of its regulatory molecules (miRNA and lncRNA) may be a new perspective for CRC treatment.

Ubiquitin-independent proteasomal degradation driven by C-degron pathways

Although most eukaryotic proteins are targeted for proteasomal degradation by ubiquitination, a subset have been demonstrated to undergo ubiquitin-independent proteasomal degradation (UbInPD). However, little is known about the molecular mechanisms driving UbInPD and the degrons involved. Utilizing the GPS-peptidome approach, a systematic method for degron discovery, we found thousands of sequences that promote UbInPD; thus, UbInPD is more prevalent than currently appreciated. Furthermore, mutagenesis experiments revealed specific C-terminal degrons required for UbInPD. Stability profiling of a genome-wide collection of human open reading frames identified 69 full-length proteins subject to UbInPD. These included REC8 and CDCA4, proteins which control proliferation and survival, as well as mislocalized secretory proteins, suggesting that UbInPD performs both regulatory and protein quality control functions. In the context of full-length proteins, C termini also play a role in promoting UbInPD. Finally, we found that Ubiquilin family proteins mediate the proteasomal targeting of a subset of UbInPD substrates.

Association of DNA Promoter Methylation and BRAF Mutation in Thyroid Cancer

The BRAF V600E mutation and DNA promoter methylation play important roles in the pathogenesis of thyroid cancer (TC). However, the association of these genetic and epigenetic alterations is not clear. In this study, using paired tumor and surrounding normal tissue from the same patients, on a genome-wide scale we tried to identify (a) any association between BRAF mutation and DNA promoter methylation, and (b) if the molecular findings may provide a basis for therapeutic intervention. We included 40 patients with TC (female = 28, male = 12) without distant metastasis. BRAF mutation was present in 18 cases. We identified groups of differentially methylated loci (DML) that are found in (a) both BRAF mutant and wild type, (b) only in BRAF mutant tumors, and (c) only in BRAF wild type. BRAF mutation-specific promoter loci were more frequently hypomethylated, whereas BRAF wild-type-specific loci were more frequently hypermethylated. Common DML were enriched in cancer-related pathways, including the mismatch repair pathway and Wnt-signaling pathway. Wild-type-specific DML were enriched in RAS signaling. Methylation status of checkpoint signaling genes, as well as the T-cell inflamed genes, indicated an opportunity for the potential use of PDL1 inhibitors in BRAF mutant TC. Our study shows an association between BRAF mutation and methylation in TC that may have biological significance.

Recent advancements to engineer mesenchymal stem cells and their extracellular vesicles for targeting and destroying tumors

Mesenchymal stem cells (MSCs) have the ability to migrate into tumor sites and release growth factors to modulate the tumor microenvironment. MSC therapy have shown a dual role in cancers, promoting or inhibiting. However, MSCs could be used as a carrier of anticancer agents for targeted tumor therapy. Recent technical improvements also allow engineering MSCs to improve tumor-targeting properties, protect anticancer agents, and decrease the cytotoxicity of drugs. While some of MSC functions are mediated through their secretome, MSCs-derived extracellular vesicles (EVs) are also proposed as a possible viechle for cancer therapy. EVs allow efficient loading of anticancer agents and have an intrinsic ability to target tumor cells, making them suitable for targeted therapy of tumors. In addition, the specificity and selectivity of EVs to the tumor sites could be enhanced by surface modification. In this review, we addressed the current approaches used for engineering MSCs and EVs to effectively target tumor sites and deliver anticancer agents.

Ectopic expression of meiotic cohesin generates chromosome instability in cancer cell line

This work originated from mining of cancer genome data and proceeded to analyze the effects of ectopic expression of meiotic cohesins in mitotic cells in culture. In the process, apart from conclusively answering the question on mechanisms for RAD21L toxicity and its underrepresentation in tumor transcriptomes, we found an association of meiotic cohesin binding with BORIS/CTCFL sites in the normal testis. We also elucidated the patterns and outcomes of meiotic cohesin binding to chromosomes in model cell lines. Furthermore, we uncovered that RAD21L-based meiotic cohesin possesses a self-contained chromosome restructuring activity able to trigger sustainable but imperfect mitotic arrest leading to chromosomal instability. The discovered epigenomic and genetic mechanisms can be relevant to chromosome instability in cancer.

Many tumors express meiotic genes that could potentially drive somatic chromosome instability. While germline cohesin subunits SMC1B, STAG3, and REC8 are widely expressed in many cancers, messenger RNA and protein for RAD21L subunit are expressed at very low levels. To elucidate the potential of meiotic cohesins to contribute to genome instability, their expression was investigated in human cell lines, predominately in DLD-1. While the induction of the REC8 complex resulted in a mild mitotic phenotype, the expression of the RAD21L complex produced an arrested but viable cell pool, thus providing a source of DNA damage, mitotic chromosome missegregation, sporadic polyteny, and altered gene expression. We also found that genomic binding profiles of ectopically expressed meiotic cohesin complexes were reminiscent of their corresponding specific binding patterns in testis. Furthermore, meiotic cohesins were found to localize to the same sites as BORIS/CTCFL, rather than CTCF sites normally associated with the somatic cohesin complex. These findings highlight the existence of a germline epigenomic memory that is conserved in cells that normally do not express meiotic genes. Our results reveal a mechanism of action by unduly expressed meiotic cohesins that potentially links them to aneuploidy and chromosomal mutations in affected cells.

REC8 inhibits proliferation, migration and invasion of breast cancer cells by targeting CDC20

Breast cancer is one of the most types of common malignant tumor in women. REC8 is a known tumor suppressor in several types of cancer; however, the role of REC8 in breast cancer remains unknown. The purpose of the present study was to investigate the effects and underlying mechanism of REC8 on the proliferation, migration and invasion of breast cancer cells. The expression of REC8 in normal and breast cancer cells was detected by reverse transcription‑quantitative PCR and western blotting. Stable REC8‑overexpressing breast cancer cells were constructed to modify the expression of REC8. The expression of cell division cycle 20 (CDC20) in breast cancer cells was altered using the CDC20 inhibitor apcin. Cell viability, proliferation, migration, invasion and apoptosis were determined by Cell Counting Kit‑8, colony formation, wound healing, Transwell and TUNEL assays, respectively. Western blotting was performed to measure the expression of matrix metalloproteinase‑2/9 and apoptosis‑associated proteins [Bcl‑2, caspase‑3, cleaved caspase‑3 and cleaved poly (ADP‑ribose) polymerase]. Compared with normal breast cells, the expression of REC8 was lower in breast cancer cells. Search Tool for the Retrieval of Interacting Genes/Proteins online database was used to predict the interaction between REC8 and CDC20. Overexpression of REC8 significantly inhibited the proliferation, migration and invasion of breast cancer cells in vitro; these changes were reversed by CDC20 overexpression. In conclusion, the present study demonstrated that REC8 decreased proliferation, migration and invasion of breast cancer cells by inhibiting CDC20.

REC8 enhances stemness and promotes metastasis of colorectal cancer through BTK/Akt/β-catenin signaling pathway

Cancer/testis antigens (CTAs) are often aberrantly expressed in cancer stem cells (CSCs) which are responsible for tumor metastasis. Rec8 meiotic recombination protein (REC8), a member of CTAs, shares distinct roles in various cancers, while its contribution to CSCs and colorectal cancer (CRC) remains unclear. We found that overexpression of REC8 facilitated the migration and invasion of CRC cells (DLD-1 and SW480 cells) in vitro and promoted the liver metastasis of CRC in vivo. Moreover, REC8 is highly expressed in CRC stem-like cells and is required for the maintenance of CSC stemness. Mechanistic studies suggested that REC8 mediated through the activation of Bruton tyrosine kinase (BTK). Inhibition of BTK by ibrutinib not only suppressed the migration and invasion-promoting ability, but also declined the increased expression of p-BTK, p-Akt, β-catenin, and CSC markers upon REC8 overexpression. Importantly, high expression of REC8 in cancerous tissues was related to advanced clinical stage and lymph node metastasis of 62 CRC patients, and REC8 was enriched in the cancerous cells positive for CSC markers. Collectively, our results indicate that REC8 promotes CRC metastasis by increasing cell stemness through BTK/Akt/β-catenin pathway.

Mesenchymal stem/stromal cells in cancer therapy

The multipotent mesenchymal stem/stromal cells (MSCs), initially discovered from bone marrow in 1976, have been identified in nearly all tissues of human body now. The multipotency of MSCs allows them to give rise to osteocytes, chondrocytes, adipocytes, and other lineages. Moreover, armed with the immunomodulation capacity and tumor-homing property, MSCs are of special relevance for cell-based therapies in the treatment of cancer. However, hampered by lack of knowledge about the controversial roles that MSC plays in the crosstalk with tumors, limited progress has been made with regard to translational medicine. Therefore, in this review, we discuss the prospects of MSC-associated anticancer strategies in light of therapeutic mechanisms and signal transduction pathways. In addition, the clinical trials designed to appraise the efficacy and safety of MSC-based anticancer therapies will be assessed according to published data.

Cancer testis antigens and genomic instability: More than immunology

Cancer testis antigens or genes (CTA, CTG) are predominantly expressed in adult testes while silenced in most or all somatic tissues with sporadic expression in many human cancers. Concerted misexpression of numerous CTA/CTGs is rarely observed. This finding argues against the germ cell theory of cancer. A surprising number of CTA/CTGs are involved in meiotic chromosome metabolism and specifically in meiotic recombination. Recent discoveries with a group of CTGs established that their misexpression in somatic cells results in genomic instability by interfering with homologous recombination (HR), a DNA repair pathway for complex DNA damage such as DNA double-stranded breaks, interstrand crosslinks, and single-stranded DNA gaps. HR-deficient tumors have specific vulnerabilities and show synthetic lethality with inhibition of polyADP-ribose polymerase, opening the possibility that expression of CTA/CTGs that result in an HR-defect could be used as an additional biomarker for HR status. Here, we review the repertoire of CTA/CTGs focusing on a cohort that functions in meiotic chromosome metabolism by interrogating relevant cancer databases and discussing recent discoveries.

REC8 promotes tumor migration, invasion and angiogenesis by targeting the PKA pathway in hepatocellular carcinoma

REC8 is a member of the cohesin family, and its abnormal activation has been detected in cancer cells. This study explored the role and possible mechanism of REC8 in hepatocellular carcinoma (HCC). A total of 40 pairs of HCC and adjacent tissues were collected, and the clinical significance of REC8 expression in HCC was evaluated. REC8 expression in human HCC tissues and HCC cell lines was investigated by quantitative real-time PCR, Western blotting, immunohistochemistry and immunofluorescence staining. The biological functions of REC8 in HCC cell lines were detected by wound-healing assay, Matrigel invasion assay and tube formation assay. The proteins interacting with REC8 were identified by mass spectrometry after immunoprecipitation screening. There was a correlation between the high expression of REC8 and positive alpha-fetoprotein levels. The expression level of REC8 protein in HCC tissues was higher than that in adjacent tissues. REC8 has mainly located in the nucleus of HCC tissue cells and HCC cell lines, but it was expressed in the cytoplasm of adjacent normal tissue cells and hepatocytes. The results of wound healing, transwell invasion and tubular formation assays indicated that the overexpression of REC8 accelerated the metastasis of HCC in vitro; however, metastasis was suppressed after REC8 was silenced by small interference RNA. A total of 57 differentially expressed proteins were identified by mass spectrometry, and it was found that REC8 and PKA RII-α staining was colocalized in the nucleus. The expression levels of MMP-9 and VEGF-C were decreased after treatment with the PKA inhibitor H89. Overall, REC8 promotes the migration, invasion and angiogenesis of HCC cells through the PKA pathway.

Differential gene expression in cisplatin-resistant and -sensitive testicular germ cell tumor cell lines

Testicular germ cell tumors (TGCTs) represent a well curable malignity due to their exceptional response to cisplatin (CDDP). Despite remarkable treatment results, approximately 5% of TGCT patients develop CDDP resistance and die. Exceptional curability makes TGCTs a highly valuable model system for studying the molecular mechanisms of CDDP sensitivity. Our study was aimed at revealing difference in gene expression between the CDDP-resistant and -sensitive TGCT cell lines, and hence at identifying candidate genes that could serve as potential biomarkers of CDDP response. Using gene expression array, we identified 281 genes that are differentially expressed in CDDP-resistant compared to -sensitive TGCT cell lines. The expression of 25 genes with the highest fold change was validated by RT-qPCR. Of them, DNMT3L, GAL, IGFBP2, IGFBP7, L1TD1, NANOG, NTF3, POU5F1, SOX2, WNT6, ZFP42, ID2, PCP4, SLC40A1 and TRIB3, displayed comparable expression change in gene expression array and RT-qPCR, when all CDDP-resistant TGCT cell lines were pairwise combined with all -sensitive ones. Products of the identified genes are pluripotency factors, or are involved in processes, such as cell metabolism, proliferation or migration. We propose that, after clinical validation, these genes could serve as prognostic biomarkers for early detection of CDDP response in TGCT patients.

REC8 suppresses tumor angiogenesis by inhibition of NF-κB-mediated vascular endothelial growth factor expression in gastric cancer cells

Background

Tumor angiogenesis is an essential event for tumor growth and metastasis. It has been showed that REC8, a component of the meiotic cohesion complex, played a vital role in Epithelial-Mesenchymal Transition (EMT) in gastric cancer. However, the role of REC8 in gastric cancer angiogenesis remains to be identified.

Results

Inhibition of REC8 expression in gastric cancer cells contributed to tumor angiogenesis in the gastric cancer microenvironment. The clinical analysis demonstrated that the loss of REC8 in gastric cancer with enrichment of MVD. Depletion of REC8 expression in gastric cancer cells significantly increased tube formation of human umbilical vein endothelial cells (HUVECs), which is attributed to enhancement of vascular endothelial growth factor (VEGF) secretion caused by REC8 slicing. While addition of neutralizing antibody targeted VEGF into supernatant drastically reversed the effect of REC8 loss in gastric cancer cells on tube formation. Mechanistic analyses indicated that ablation of REC8 promotes nuclear factor-κB (NF-κB) p65 activity and its downstream gene VEGF expression, leading to tube formation.

Conclusions

These results demonstrated a novel REC8 function that suppressed tumor angiogenesis and progression by attenuation of VEGF in gastric cancer microenvironment.

Electronic supplementary material

The online version of this article (10.1186/s40659-020-00307-1) contains supplementary material, which is available to authorized users.

Role of PI3K/AKT pathway in cancer: the framework of malignant behavior

Given that the PI3K/AKT pathway has manifested its compelling influence on multiple cellular process, we further review the roles of hyperactivation of PI3K/AKT pathway in various human cancers. We state the abnormalities of PI3K/AKT pathway in different cancers, which are closely related with tumorigenesis, proliferation, growth, apoptosis, invasion, metastasis, epithelial-mesenchymal transition, stem-like phenotype, immune microenvironment and drug resistance of cancer cells. In addition, we investigated the current clinical trials of inhibitors against PI3K/AKT pathway in cancers and found that the clinical efficacy of these inhibitors as monotherapy has so far been limited despite of the promising preclinical activity, which means combinations of targeted therapy may achieve better efficacies in cancers. In short, we hope to feature PI3K/AKT pathway in cancers to the clinic and bring the new promising to patients for targeted therapies.

The ectopic expression of meiCT genes promotes meiomitosis and may facilitate carcinogenesis

Cancer meiomitosis is defined as the concurrent activation of both mitotic and meiotic machineries in neoplastic cells that confer a selective advantage together with increased genomic instability. MeiCT (meiosis-specific cancer/testis) genes that perform specialized functions in the germline events required for the first meiotic division are ectopically expressed in several cancers. Here we describe the expression profiles of meiCT genes and proteins across a number of cancers and review the proposed mechanisms that increase aneuploidy and elicit reduction division in polyploid cells. These mechanisms are centered on the overexpression and function of meiCT proteins in cancers under various conditions that includes a response to genotoxic stress. Since meiCT genes are transcriptionally repressed in somatic cells, their target offers a promising therapeutic approach with limited toxicity to healthy tissues. Throughout the review, we provide a detailed description of the roles for each gene in the context of meiosis and we discuss proposed functions and outcomes resulting from their ectopic reactivation in cancer.

DNA methylation changes in infants between 6 and 52 weeks

Infants undergo extensive developments during their first year of life. Although the biological mechanisms involved are not yet fully understood, changes in the DNA methylation in mammals are believed to play a key role. This study was designed to investigate changes in infant DNA methylation that occurs between 6 and 52 weeks. A total of 214 infant saliva samples from 6 or 52 weeks were assessed using principal component analyses and t-distributed stochastic neighbor-embedding algorithms. Between the two time points, there were clear differences in DNA methylation. To further investigate these findings, paired two-sided student’s t-tests were performed. Differently methylated regions were defined as at least two consecutive probes that showed significant differences, with a q-value < 0.01 and a mean difference > 0.2. After correcting for false discovery rates, changes in the DNA methylation levels were found in 42 genes. Of these, 36 genes showed increased and six decreased DNA methylation. The overall DNA methylation changes indicated decreased gene expression. This was surprising because infants undergo such profound developments during their first year of life. The results were evaluated by taking into consideration the extensive development that occurs during pregnancy. During the first year of life, infants have an overall three-fold increase in weight, while the fetus develops from a single cell into a viable infant in 9 months, with an 875-million-fold increase in weight. It is possible that the findings represent a biological slowing mechanism in response to extensive fetal development. In conclusion, our study provides evidence of DNA methylation changes during the first year of life, representing a possible biological slowing mechanism. We encourage future studies of DNA methylation changes in infants to replicate the findings by using a repeated measures model and less stringent criteria to see if the same genes can be found, as well as investigating whether other genes are involved in development during this period.

Longitudinal study of leukocyte DNA methylation and biomarkers for cancer risk in older adults

Background

Changes in DNA methylation over the course of life may provide an indicator of risk for cancer. We explored longitudinal changes in CpG methylation from blood leukocytes, and likelihood of future cancer diagnosis.

Methods

Peripheral blood samples were obtained at baseline and at follow-up visit from 20 participants in the Health, Aging and Body Composition prospective cohort study. Genome-wide CpG methylation was assayed using the Illumina Infinium Human MethylationEPIC (HM850K) microarray.

Results

Global patterns in DNA methylation from CpG-based analyses showed extensive changes in cell composition over time in participants who developed cancer. By visit year 6, the proportion of CD8+ T-cells decreased (p-value = 0.02), while granulocytes cell levels increased (p-value = 0.04) among participants diagnosed with cancer compared to those who remained cancer-free (cancer-free vs. cancer-present: 0.03 ± 0.02 vs. 0.003 ± 0.005 for CD8+ T-cells; 0.52 ± 0.14 vs. 0.66 ± 0.09 for granulocytes). Epigenome-wide analysis identified three CpGs with suggestive p-values ≤10^− 5 for differential methylation between cancer-free and cancer-present groups, including a CpG located in MTA3, a gene linked with metastasis. At a lenient statistical threshold (p-value ≤3 × 10^− 5), the top 10 cancer-associated CpGs included a site near RPTOR that is involved in the mTOR pathway, and the candidate tumor suppressor genes REC8, KCNQ1, and ZSWIM5. However, only the CpG in RPTOR (cg08129331) was replicated in an independent data set. Analysis of within-individual change from baseline to Year 6 found significant correlations between the rates of change in methylation in RPTOR, REC8 and ZSWIM5, and time to cancer diagnosis.

Conclusion

The results show that changes in cellular composition explains much of the cross-sectional and longitudinal variation in CpG methylation. Additionally, differential methylation and longitudinal dynamics at specific CpGs could provide powerful indicators of cancer development and/or progression. In particular, we highlight CpG methylation in the RPTOR gene as a potential biomarker of cancer that awaits further validation.

Electronic supplementary material

The online version of this article (10.1186/s40364-019-0161-3) contains supplementary material, which is available to authorized users.

FANCM, RAD1, CHEK1 and TP53I3 act as BRCA-like tumor suppressors and are mutated in hereditary ovarian cancer

Although 25% of ovarian cancer cases are due to inherited factors, most of the genetic risk remains unexplained. We previously identified candidate genes through germline whole exome sequencing of BRCA1/BRCA2 negative ovarian cancer patients with familial risk. Here, we performed functional assessment to determine whether they act as BRCA-like tumor suppressors. Seven candidate risk genes were targeted by siRNA for mRNA depletion followed by functional assays for clonogenic survival, cytotoxicity to DNA damaging agents, and involvement in homologous recombination repair. BRCA1 and BRCA1 were targeted as standards for loss of function outcome. Knockdown of various candidate genes led to tumor suppressor phenotypes also observed in BRCA1/BRCA2 deficient cells. Deficiency of CHEK1, FANCM and TP53I3 led to reduced homologous recombination repair efficiency. Knockdown of RAD1, CHEK1 or FANCM led to a decrease in cellular viability and cells deficient in CHEK1, RAD1 or TP53I3 displayed increased sensitivity to cisplatin. Functional studies of candidate genes identified by whole exome sequencing complements bioinformatics techniques and aid the implication of novel risk loci. The results of this study suggest that genes found mutated in hereditary ovarian cancer, FANCM, RAD1, CHEK1 and TP53I3, act as BRCA-like tumor suppressors.

The epigenetic landscape of differentiated thyroid cancer

Differentiated thyroid carcinoma of follicular cell-derivation is the most common endocrine neoplasm with a rapidly increasing incidence. The majority represent papillary carcinomas; more rarely, they are follicular carcinomas. The vast majority have indolent behavior, however a significant proportion progress to develop lymph node metastases and a smaller proportion disseminate systemically. While common and frequent genetic events have been described to underlie the development of these neoplasms, the factors contributing to differing behaviors among tumors with similar genetic alterations remain unclear. This review focuses on epigenetic mechanisms targeting major signaling pathways that underlie the spectrum of biological behaviors and that may have potential diagnostic, prognostic and therapeutic value.

Epigenetic modifications in poorly differentiated and anaplastic thyroid cancer

Well-differentiated thyroid cancer accounts for the majority of endocrine malignancies and, in general, has an excellent prognosis. In contrast, the less common poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC) are two of the most aggressive human malignancies. Recently, there has been an increased focus on the epigenetic alterations underlying thyroid carcinogenesis, including those that drive PDTC and ATC. Dysregulated epigenetic candidates identified include the Aurora group, KMT2D, PTEN, RASSF1A, multiple non-coding RNAs (ncRNA), and the SWI/SNF chromatin-remodeling complex. A deeper understanding of the signaling pathways affected by epigenetic dysregulation may improve prognostic testing and support the advancement of thyroid-specific epigenetic therapies. This review outlines the current understanding of epigenetic alterations observed in PDTC and ATC and explores the potential for exploiting this understanding in developing novel therapeutic strategies.

REC8 inhibits EMT by downregulating EGR1 in gastric cancer cells

REC8 is a component of the meiotic cohesion complex that plays a critical role in chromosome dynamics during meiosis. However, the functional role of REC8 in gastric cancer has not been elucidated. In the present study, REC8 suppressed the growth and metastasis of gastric cancer cells in vitro. Whole Human Genome Oligo Microarray results revealed that a wide range of genes with broad function were targeted by REC8. Among them early growth response-1 (EGR1), a transcription factor and an epithelial-mesenchymal transition (EMT)-associated protein in the AGR-RAGE pathway was significantly downregulated when REC8 was overexpressed in gastric cancer cells. We hypothesized that REC8 inhibits EMT by downregulating EGR1 in gastric cancer cells. Consistent with our prediction, REC8 overexpression decreased EMT in gastric cancer cells, whereas the REC8 ablation reversed these effects. In addition, the phenotypes of EGR1 overexpressed cells were similar to the phenotypes of REC8 ablated cells. Furthermore, we determined that REC8 interacted with EGR1, and inhibited EMT in gastric cancer cells. We thus propose further studies of the pathways associated with REC8 and EGR1 to potentially find novel targets in the treatment for gastric cancer.

Tumor-suppressive function of UNC5D in papillary thyroid cancer

Background

Studies have shown an association of the UNC5D gene with kidney and bladder cancer and neuroblastoma. We investigated whether UNC5D acts as a tumor suppressor in papillary thyroid carcinoma (PTC).

Methods

Primary PTC tumors and matched normal thyroid tissues were obtained from 112 patients to detect UNC5D mRNA by real-time PCR. Genomic DNA sequencing was performed to detect BRAF mutation in PTC tumors. The association between UNC5D expression and clinicopathological data from PTC patients was reviewed retrospectively. PTC-derived cancer cell lines TPC-1 and K1 with stable transfection of UNC5D were used to investigate the functions of UNC5D. Flow cytometry, CCK-8, Transwell assay and scratch tests were used to examine cell cycle distribution, proliferation and migration.

Results

The expression of UNC5D was significantly decreased in PTC compared with adjacent normal thyroid tissues. Lower UNC5D expression was significantly associated with aggressive tumor behaviors, such as lymph node metastasis and BRAF mutation. Overexpression of UNC5D significantly suppressed malignant cell behaviors, including cell proliferation and migration, as well as tumor growth in vivo.

Conclusions

These findings suggest a potential tumor suppressor role of UNC5D in PTC progression; and provide insight into potential clinical relevance for the prognosis of PTC.

Epigenetic modulators of thyroid cancer

There are some well known factors involved in the etiology of thyroid cancer, including iodine deficiency, radiation exposure at early ages, or some genetic changes. However, epigenetic modulators that may contribute to development of these tumors and be helpful to for both their diagnosis and treatment have recently been discovered. The currently known changes in DNA methylation, histone modifications, and non-coding RNAs in each type of thyroid carcinoma are reviewed here.

REC8 functions as a tumor suppressor and is epigenetically downregulated in gastric cancer, especially in EBV-positive subtype

REC8 meiotic recombination protein (REC8) was found to be preferentially methylated in gastric cancer (GC) using promoter methylation array. We aimed to elucidate the epigenetic alteration and biological function of REC8 in GC. REC8 was downregulated in 100% (3/3) of Epstein–Barr virus (EBV)-positive and 80% (8/10) of EBV-negative GC cell lines by promoter methylation, but the expression could be restored through demethylation treatment. Protein expression of REC8 was significantly lower in human primary gastric tumors than in adjacent non-tumor tissues. A negative correlation between methylation and mRNA expression of REC8 was observed in 223 gastric samples of The Cancer Genome Atlas study (r=−0.7018, P<0.001). The methylation level (%) of the REC8 promoter was significantly higher in EBV-positive gastric tumors than in EBV-negative gastric tumors, as shown by bisulfite genomic sequencing (77.6 (69.3–80.5) vs 51.4 (39.5–62.3), median (interquartile range); P<0.001); methylation levels in both subtypes of tumors were significantly higher than in normal stomach tissues (14.8 (4.2–24.0)) (both P<0.001). Multivariate analysis revealed that REC8 methylation was an independent factor for poor survival in GC patients (hazard ratio=1.68, P<0.05). REC8 expression significantly suppressed cell viability, clonogenicity and cell cycle progression; it induced apoptosis and inhibited migration of AGS-EBV (EBV-positive) and BGC823 (EBV-negative) GC cells, and it suppressed tumorigenicity in nude mice. In contrast, knockdown of REC8 in gastric epithelial immortalized GES-1 cells significantly increased cell viability, clonogenicity and migration ability. The tumor-suppressive effect of REC8 is mediated at least in part by the downregulation of genes involved in cell growth (G6PD, SLC2A1, NOL3, MCM2, SNAI1 and SNAI2), and the upregulation of apoptosis/migration inhibitors (GADD45G and LDHA) and tumor suppressors (PinX1, IGFBP3 and ETS2). In conclusion, REC8 is a novel tumor suppressor that is commonly downregulated by promoter methylation in GC, especially in the EBV-associated subtype. Promoter methylation of REC8 is an independent risk factor for the shortened survival of GC patients.