CBX2 identified as driver of anoikis escape and dissemination in high grade serous ovarian cancer

Role of cell division cycle-associated proteins in regulating cell cycle and promoting tumor progression

The cell division cycle-associated protein (CDCA) family is important in regulating cell division. High CDCA expression is significantly linked to tumor development. This review summarizes clinical and basic studies on CDCAs conducted in recent decades. Furthermore, it systematically introduces the molecular expression and function, key mechanisms, cell cycle regulation, and roles of CDCAs in tumor development, cell proliferation, drug resistance, invasion, and metastasis. Additionally, it presents the latest research on tumor diagnosis, prognosis, and treatment targeting CDCAs. These findings are pivotal for further in-depth studies on the role of CDCAs in promoting tumor development and provide theoretical support for their application as new anti-tumor targets.

Deregulated circRNAs in Epithelial Ovarian Cancer With Activity in Preclinical In Vivo Models: Identification of Targets and New Modalities for Therapeutic Intervention

Epithelial ovarian cancer (EOC) is associated with a dismal prognosis due to development of resistance to chemotherapy and metastasis in the peritoneal cavity and distant organs. In order to identify new targets and treatment modalities we searched the literature for up- and and down-regulated circRNAs with efficacy in preclinical EOC-related in vivo systems. Our search yielded circRNAs falling into the following categories: cisplatin and paclitaxel resistance, transmembrane receptors, secreted factors, transcription factors, RNA splicing and processing factors, RAS pathway-related components, proteolysis and cell-cycle regulation, signaling-related proteins, and circRNAs regulating proteins in additional categories. These findings can be potentially translated by validation and manipulation of the corresponding targets, inhibition of circRNAs with antisense oligonucleotides (ASO), small interfering RNAs (siRNA) or small hairpin RNA (shRNA) or by reconstituting their activity.

CBX2 Deletion Suppresses Growth and Metastasis of Colorectal Cancer by Mettl3-p38/ERK MAPK Signalling Pathway

Colorectal cancer (CRC) seriously endangers human health owing to its high morbidity and mortality. Previous studies have suggested that high expression of CBX2 may be associated with poor prognosis in CRC patients. However, its functional role in CRC remains to be elucidated. Herein, we found that CBX2 overexpression in colorectal cancer tissue compared with adjacent tissues. Additionally, forest maps and the nomogram model indicated that elevated CBX2 expression was an independent prognostic factor in CRC. Moreover, we confirmed that the deletion of CBX2 markedly suppressed the proliferation and migration of CRC cells in vitro and in vivo. Furthermore, downregulation of CBX2 promotes CRC cell apoptosis and hinders the cell cycle. Mechanistically, our data demonstrated that deletion of CBX2 inhibited the MAPK signaling pathway by regulating the protein levels of Mettl3. In conclusion, our study demonstrated that CBX2 is a vital tumor suppressor in CRC and could be a promising anti-cancer therapeutic target.

Cuproptosis-related ceRNA axis triggers cell proliferation and cell cycle through CBX2 in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) has high morbidity and mortality. Despite substantial advances in treatment, the prognosis of patients with LUAD remains unfavorable. The ceRNA axis has been reported to play an important role in the pathogenesis of LUAD. In addition, cuproptosis is considered an important factor in tumorigenesis. The expression of CBX2 has been associated with the development of multiple tumors, including LUAD. However, the precise molecular mechanisms through which the cuproptosis-related ceRNA network regulates CBX2 remain unclear.

METHODS

The DEGs between tumor and normal samples of LUAD were identified in TCGA database. The "ConsensusClusterPlus" R package was used to perform consensus clustering based on the mRNA expression matrix and cuproptosis-related gene expression profile. Then, LASSO-COX regression analysis was performed to identify potential prognostic biomarkers associated with cuproptosis, and the ceRNA network was constructed. Finally, the mechanisms of ceRNA in LUAD was studied by cell experiments.

RESULTS

In this study, the AC144450.1/miR-424-5p axis was found to promote the progression of LUAD by acting on CBX2. The expression of AC144450.1 and miR-424-5p can be altered to regulate CBX2 and is correlated with cell proliferation and cell cycle of LUAD. Mechanistically, AC144450.1 affects the expression of CBX2 by acting as the ceRNA of miR-424-5p. In addition, a cuproptosis-related model were constructed in this study to predict the prognosis of LUAD.

CONCLUSIONS

This study is the first to demonstrate that the AC144450.1/miR-424-5p/CBX2 axis is involved in LUAD progression and may serve as a novel target for its diagnosis and treatment.

CASC4/GOLM2 drives high grade serous carcinoma anoikis resistance through the recycling of EGFR

Ovarian cancer is the deadliest gynecological malignancy, and accounts for over 150,000 deaths per year worldwide. The high grade serous ovarian carcinoma (HGSC) subtype accounts for almost 70% of ovarian cancers and is the deadliest. HGSC originates in the fimbria of the fallopian tube and disseminates through the peritoneal cavity. HGSC survival in peritoneal fluid requires cells to resist anoikis (anchorage-independent apoptosis). Most anoikis resistant mechanisms are dependent on microenvironment interactions with cell surface-associated proteins, such as integrins and receptor tyrosine kinases (RTKs). We previously identified the gene CASC4 as a driver of anoikis resistance. CASC4 is predicted to be a Golgi-associated protein that may regulate protein trafficking to the plasma membrane, but CASC4 is largely uncharacterized in literature; thus, we sought to determine how CASC4 confers anoikis resistance to HGSC cells. Mining of publicly available ovarian cancer datasets (TCGA) showed that CASC4 is associated with worse overall survival and increased resistance to platinum-based chemotherapies. For experiments, we cultured three human HGSC cell lines (PEO1, CaOV3, OVCAR3), and a murine HGSC cell line, (ID8) with shRNA-mediated CASC4 knockdowns (CASC4 KD) in suspension, to recapitulate the peritoneal fluid environment in vitro. CASC4 KD significantly inhibited cell proliferation and colony formation ability, and increased apoptosis. A Reverse Phase Protein Assay (RPPA) showed that CASC4 KD resulted in a broad re-programming of membrane-associated proteins. Specifically, CASC4 KD led to decreased protein levels of the RTK Epidermal Growth Factor Receptor (EGFR), an initiator of several oncogenic signaling pathways, leading us to hypothesize that CASC4 drives HGSC survival through mediating recycling and trafficking of EGFR. Indeed, loss of CASC4 led to a decrease in both EGFR membrane localization, reduced turnover of EGFR, and increased EGFR ubiquitination. Moreover, a syngeneic ID8 murine model of ovarian cancer showed that knocking down CASC4 leads to decreased tumor burden and dissemination.

The spatial structure of the tumor immune microenvironment can explain and predict patient response in high-grade serous carcinoma

Despite ovarian cancer being the deadliest gynecological malignancy, there has been little change to therapeutic options and mortality rates over the last three decades. Recent studies indicate that the composition of the tumor immune microenvironment (TIME) influences patient outcomes but are limited by a lack of spatial understanding. We performed multiplexed ion beam imaging (MIBI) on 83 human high-grade serous carcinoma tumors - one of the largest protein-based, spatially-intact, single-cell resolution tumor datasets assembled - and used statistical and machine learning approaches to connect features of the TIME spatial organization to patient outcomes. Along with traditional clinical/immunohistochemical attributes and indicators of TIME composition, we found that several features of TIME spatial organization had significant univariate correlations and/or high relative importance in high-dimensional predictive models. The top performing predictive model for patient progression-free survival (PFS) used a combination of TIME composition and spatial features. Results demonstrate the importance of spatial structure in understanding how the TIME contributes to treatment outcomes. Furthermore, the present study provides a generalizable roadmap for spatial analyses of the TIME in ovarian cancer research.

Anoikis related genes may be novel markers associated with prognosis for ovarian cancer

The aim of this study was to determine the prognostic significance of anoikis related genes (ARGs) in ovarian cancer (OC) and to develop a prognostic signature based on ARG expression. We analyzed cohorts of OC patients and used nonnegative matrix factorization (NMF) for clustering. Single-sample gene-set enrichment analysis (ssGSEA) was employed to quantify immune infiltration. Survival analyses were performed using the Kaplan-Meier method, and differences in survival were determined using the log-rank test. The extent of anoikis modification was quantified using a risk score generated from ARG expression. The analysis of single-cell sequencing data was performed by the Tumor Immune Single Cell Hub (TISCH). Our analyses revealed two distinct patterns of anoikis modification. The risk score was used to evaluate the anoikis modification patterns in individual tumors. Three hub-genes were screened using the LASSO (Least Absolute Shrinkage and Selection Operator) method and patients were classified into different risk groups based on their individual score and the median score. The low-risk subtype was characterized by decreased expression of hub-genes and better overall survival. The risk score, along with patient age and gender, were considered to identify the prognostic signature, which was visualized using a nomogram. Our findings suggest that ARGs may play a novel role in the prognosis of OC. Based on ARG expression, we have developed a prognostic signature for OC that can aid in patient stratification and treatment decision-making. Further studies are needed to validate these results and to explore the underlying mechanisms.

Ovarian cancer relies on the PDGFRβ-fibronectin axis for tumorsphere formation and metastatic spread

High-grade serous ovarian cancer (HGSOC) is the deadliest gynecological malignancy. The most common form of metastatic spread of HGSOC is transcoelomic dissemination. In this process, detached cells from the primary tumor aggregate as tumorspheres and promote the accumulation of peritoneal ascites. This represents an early event in HGSOC development and is indicative of poor prognosis. In this study, based on tumorspheres isolated from ascitic liquid samples from HGSOC patients, ovarian cancer spheroid 3D cultures, and in vivo models, we describe a key signal for tumorsphere formation in HGSOC. We report that platelet-derived growth factor receptor beta (PDGFRβ) is essential for fibronectin-mediated cell clustering of ovarian cancer cells into tumorspheres. This effect is mediated by the kinase NUAK family SNF1-like kinase 1 (NUAK1) and blocked by PDGFRβ pharmacological or genetic inhibition. In the absence of PDGFRβ, ovarian cancer cells can be provided with fibronectin by cancer-associated fibroblasts to generate chimeric spheroids. This work provides new insights that uncover potential targets to prevent peritoneal dissemination, the main cause of advanced disease in HGSOC patients.

miR‑149‑3p suppresses the proliferation and metastasis of glioma cells by targeting the CBX2/Wnt/β‑catenin pathway

The present study aimed to investigate the role of miR-149-3p/chromobox 2 (CBX2)/Wnt/β-catenin pathway in the proliferation and metastasis of glioma cells. The expression and clinical significance of miR-149-3p and CBX2 were analyzed using data from public databases. Cell Counting Kit-8 and colony formation assays were performed to measure cell proliferation. Transwell assays were used to assess cell invasion. The results showed that miR-149-3p was downregulated and CBX2 was upregulated in glioma, and that the downregulated expression of miR-149-3p promoted the proliferation and invasion of glioma cells. In addition, downregulated expression of CBX2 suppressed the proliferation and invasion of glioma cells. Dual-luciferase assay indicated that CBX2 is a target gene of miR149-3p. The possible molecular mechanism of CBX2 was probed by western blotting, which showed that it may further affect the Wnt/β-catenin pathway. These present findings demonstrated that miR-149-3p may function as a tumor suppressor miRNA by directly regulating CBX2 and serve important roles in the malignancy of glioma.

Phosphorylation of USP27X by GSK3β maintains the stability and oncogenic functions of CBX2

Chromobox protein homolog 2 (CBX2) exerts a multifaceted impact on the progression of aggressive cancers. The proteasome-dependent pathway is crucial for modulating CBX2 regulation, while the specific regulatory roles and mechanisms of deubiquitinating enzymes targeting CBX2 remain poorly understood. Mass spectrometry analysis identified ubiquitin-specific peptidase 27X (USP27X) as a deubiquitinating enzyme that targets CBX2. Overexpression of USP27X significantly enhances CBX2 levels by promoting deubiquitination, while deficiency of USP27X leads to CBX2 degradation, thereby inhibiting tumorigenesis. Furthermore, it has been revealed that glycogen synthase kinase 3 beta (GSK3β) can directly bind to and phosphorylate USP27X, thereby enhancing the interaction between USP27X and CBX2 and leading to further stabilization of the CBX2 protein. Clinically, the co-expression of high levels of USP27X and CBX2 in breast cancer tissues is indicative of a poor prognosis for patients with this disease. These findings collectively underscore the critical regulatory role played by USP27X in modulating CBX2, thereby establishing the GSK3β-USP27X-CBX2 axis as a pivotal driver of malignant progression in breast cancer.

Development of a prognostic model for anoikis and identifies hub genes in hepatocellular carcinoma

Considering the high fatality of hepatocellular carcinoma (HCC), current prognostic systems are insufficient to accurately forecast HCC patients' outcomes. In our study, nine anoikis‑related genes (PTRH2, ITGAV, ANXA5, BIRC5, BDNF, BSG, DAP3, SKP2, and EGF) were determined to establish a risk scoring model using LASSO regression, which could be validated in ICGC dataset. Kaplan-Meier curves and time-dependent receiver operating characteristic (ROC) curve analysis confirmed the risk score possessed an accurate predictive value for the prognosis of HCC patients. The high-risk group showed a higher infiltration of aDCs, macrophages, T-follicular helper cells, and Th2 cells. Besides, PD-L1 was significantly higher in the high-risk group compared to the low-risk group. Several anoikis‑related genes, such as ANX5, ITGAV, BDNF and SKP2, were associated with drug sensitivity in HCC. Finally, we identified BIRC5 and SKP2 as hub genes among the nine model genes using WGCNA analysis. BIRC5 and SKP2 were over-expressed in HCC tissues, and their over-expression was associated with poor prognosis, no matter in our cohort by immunohistochemical staining or in the TCGA cohort by mRNA-Seq. In our cohort, BIRC5 expression was highly associated with the T stage, pathologic stage, histologic grade and AFP of HCC patients. In general, our anoikis-related risk model can enhance the ability to predict the survival outcomes of HCC patients and provide a feasible therapeutic strategy for immunotherapy and drug resistance in HCC. BIRC5 and SKP2 are hub genes of anoikis‑related genes in HCC.

The anoikis-related gene signature predicts survival accurately in colon adenocarcinoma

Colon adenocarcinoma (COAD) is a serious public health problem, the third most common cancer and the second most deadly cancer in the world. About 9.4% of cancer-related deaths in 2020 were due to COAD. Anoikis is a specialized form of programmed cell death that plays an important role in tumor invasion and metastasis. The presence of anti-anoikis factors is associated with tumor aggressiveness and drug resistance. Various bioinformatic methods, such as differential expression analysis, and functional annotation analysis, machine learning, were used in this study. RNA-sequencing and clinical data from COAD patients were obtained from the Gene expression omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. Construction of a prognostic nomogram for predicting overall survival (OS) using multivariate analysis and Lasso-Cox regression. Immunohistochemistry (IHC) was our method of validating the expression of seven genes that are linked to anoikis in COAD. We identified seven anoikis-related genes as predictors of COAD survival and prognosis, and confirmed their accuracy in predicting colon adenocarcinoma prognosis by KM survival curves and ROC curves. A seven-gene risk score consisting of NAT1, CDC25C, ATP2A3, MMP3, EEF1A2, PBK, and TIMP1 showed strong prognostic value. Meanwhile, we made a nomogram to predict the survival rate of COAD patients. The immune infiltration assay showed T cells. CD4 memory. Rest and macrophages. M0 has a higher proportion in COAD, and 11 genes related to tumor immunity are important. GDSC2-based drug susceptibility analysis showed that 6 out of 198 drugs were significant in COAD. Anoikis-related genes have potential value in predicting the prognosis of COAD and provide clues for developing new therapeutic strategies for COAD. Immune infiltration and drug susceptibility results provide important clues for finding new personalized treatment options for COAD. These findings also suggest possible mechanisms that may affect prognosis. These results are the starting point for planning individualized treatment and managing patient outcomes.

Identification of molecular subtypes based on PANoptosis-related genes and construction of a signature for predicting the prognosis and response to immunotherapy response in hepatocellular carcinoma

Background

Previous studies have demonstrated that PANoptosis is strongly correlated with cancer immunity and progression. This study aimed to develop a PANoptosis-related signature (PANRS) to explore its potential value in predicting the prognosis and immunotherapy response of hepatocellular carcinoma (HCC).

Methods

Based on the expression of PANoptosis-related genes, three molecular subtypes were identified. To construct a signature, the differentially expressed genes between different molecular subtypes were subjected to multivariate least absolute shrinkage and selection operator Cox regression analyses. The risk scores of patients in the training set were calculated using the signature. The patients were classified into high-risk and low-risk groups based on the median risk scores. The predictive performance of the signature was evaluated using Kaplan-Meier plotter, receiving operating characteristic curves, nomogram, and calibration curve. The results were validated using external datasets. Additionally, the correlation of the signature with the immune landscape and drug sensitivity was examined. Furthermore, the effect of LPCAT1 knockdown on HCC cell behavior was verified using in vitro experiments.

Results

This study developed a PANRS. The risk score obtained by using the PANRS was an independent risk factor for the prognosis of patients with HCC and exhibited good prognostic predictive performance. The nomogram constructed based on the risk score and clinical information can accurately predicted the survival probability of patients with HCC. Patients with HCC in the high-risk groups have high immune scores and tend to generate an immunosuppressive microenvironment. They also exhibited a favorable response to immunotherapy, as evidenced by high tumor mutational burden, high immune checkpoint gene expression, high human leukocyte antigen gene expression, low tumor immune dysfunction and low exclusion scores. Additionally, the PANRS enabled the identification of 15 chemotherapeutic agents, including sorafenib, for patients with HCC with different risk levels, guiding clinical treatment. The signature gene LPCAT1 was upregulated in HCC cell lines. LPCAT1 knockdown markedly decreased HCC cell proliferation and migration.

Conclusion

PANRS can accurately predict the prognosis and immunotherapy response of patients with HCC and consequently guide individualized treatment.

Development of anoikis-related long non-coding RNA signature associated with prognosis and immune landscape in cutaneous melanoma patients

BACKGROUND

Anoikis is involved in many critical biological processes in tumors; however, function in CM is still unknown. In this study, the relevance between Anoikis-related lncRNAs (ARLs) and the clinicopathological characteristics of patients with CM was comprehensively assessed.

METHODS

Through analysis of TCGA dataset, ARLs were identified by using TCGA dataset. Based on the ARLs, a risk model was established to anticipate the prognosis of patients with CM, besides, the prediction accuracy of the model was evaluated. The immune infiltration landscape of patients with CM was assessed comprehensively, and the correlation between ARLs and immunity was elucidated. Immunotherapy and drug sensitivity analyses were applied to analyze the treatment response in patients with CM with diverse risk scores. Different subgroups were distinguished among the patients using consensus cluster analysis.

RESULTS

A risk model based on six ARLs was set up to obtain an accurate prediction of the prognosis of patients with CM. There were distinctions in the immune landscape among CM patients with diverse risk scores and subgroups. Six prognosis-related ARLs were highly correlated with the number of immune cells. Patients with CM with different risk scores have various sensitivities to immunotherapy and antitumor drug treatments.

CONCLUSION

Our newly risk model associated with ARLs has considerable prognostic value for patients with CM. Not only has the risk model high prediction accuracy but it also indicates the immune status of CM patients, which will provide a new direction for the individualized therapy of patients with CM.

Multi-Omics Data Analysis Identifies Prognostic Biomarkers across Cancers

Combining omics data from different layers using integrative methods provides a better understanding of the biology of a complex disease such as cancer. The discovery of biomarkers related to cancer development or prognosis helps to find more effective treatment options. This study integrates multi-omics data of different cancer types with a network-based approach to explore common gene modules among different tumors by running community detection methods on the integrated network. The common modules were evaluated by several biological metrics adapted to cancer. Then, a new prognostic scoring method was developed by weighting mRNA expression, methylation, and mutation status of genes. The survival analysis pointed out statistically significant results for GNG11, CBX2, CDKN3, ARHGEF10, CLN8, SEC61G and PTDSS1 genes. The literature search reveals that the identified biomarkers are associated with the same or different types of cancers. Our method does not only identify known cancer-specific biomarker genes, but also proposes new potential biomarkers. Thus, this study provides a rationale for identifying new gene targets and expanding treatment options across cancer types.

A signature based on anoikis-related genes for the evaluation of prognosis, immunoinfiltration, mutation, and therapeutic response in ovarian cancer

Background

Ovarian cancer (OC) is a highly lethal and aggressive gynecologic cancer, with an overall survival rate that has shown little improvement over the decades. Robust models are urgently needed to distinguish high-risk cases and predict reliable treatment options for OC. Although anoikis-related genes (ARGs) have been reported to contribute to tumor growth and metastasis, their prognostic value in OC remains unknown. The purpose of this study was to construct an ARG pair (ARGP)-based prognostic signature for patients with OC and elucidate the potential mechanism underlying the involvement of ARGs in OC progression.

Methods

The RNA-sequencing and clinical information data of OC patients were obtained from The Center Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. A novel algorithm based on pairwise comparison was utilized to select ARGPs, followed by the Least Absolute Shrinkage and Selection Operator Cox analysis to construct a prognostic signature. The predictive ability of the model was validated using an external dataset, a receiver operating characteristic curve, and stratification analysis. The immune microenvironment and the proportion of immune cells were analyzed in high- and low-risk OC cases using seven algorithms. Gene set enrichment analysis and weighted gene co-expression network analysis were performed to investigate the potential mechanisms of ARGs in OC occurrence and prognosis.

Results

The 19-ARGP signature was identified as an important prognostic predictor for 1-, 2-, and 3-year overall survival of patients with OC. Gene function enrichment analysis showed that the high-risk group was characterized by the infiltration of immunosuppressive cells and the enrichment of adherence-related signaling pathway, suggesting that ARGs were involved in OC progression by mediating immune escape and tumor metastasis.

Conclusion

We constructed a reliable ARGP prognostic signature of OC, and our findings suggested that ARGs exerted a vital interplay in OC immune microenvironment and therapeutic response. These insights provided valuable information regarding the molecular mechanisms underlying this disease and potential targeted therapies.

Novel chromobox 2 inhibitory peptide decreases tumor progression

BACKGROUND

The Polycomb Repressor Complex 1 (PRC1) is an epigenetic regulator of differentiation and development, consisting of multiple subunits including RING1, BMI1, and Chromobox. The composition of PRC1 dictates its function and aberrant expression of specific subunits contributes to several diseases including cancer. Specifically, the reader protein Chromobox2 (CBX2) recognizes the repressive modifications including histone H3 lysine 27 tri-methylation (H3K27me3) and H3 lysine 9 dimethylation (H3K9me2). CBX2 is overexpressed in several cancers compared to the non-transformed cell counterparts, it promotes both cancer progression and chemotherapy resistance. Thus, inhibiting the reader function of CBX2 is an attractive and unique anti-cancer approach.

RESEARCH DESIGN & METHODS

Compared with other CBX family members, CBX2 has a unique A/T-hook DNA binding domain that is juxtaposed to the chromodomain (CD). Using a computational approach, we constructed a homology model of CBX2 encompassing the CD and A/T hook domain. We used the model as a basis for peptide design and identified blocking peptides that are predicted to directly bind the CD and A/T-hook regions of CBX2. These peptides were tested in vitro and in vivo models.

CONCLUSION

The CBX2 blocking peptide significantly inhibited both 2D and 3D growth of ovarian cancer cells, downregulated a CBX2 target gene, and blunted tumor growth in vivo.

Loss of CBX2 causes genomic instability and Wnt activation in high grade serous ovarian carcinoma cells

High grade serous ovarian carcinoma (HGSOC) is lethal with insidious onset, rapid progression, poor prognosis, and limited treatment options. Polycomb repressor complexes (PRC) 1 and 2 are intimately involved in progression of many types of cancer including HGSOC. Unlike the consistent constitution of PRC2, PRC1 consists of diverse components whose clinical significance in HGSOC are not entirely clear. Here, prognosis-associated PRC1 components were identified through data-mining. CBX2 promoted proliferation and reduced apoptosis of HGSOC cell lines OVCAR4, OVCAR3, and CAOV3. Complete loss of CBX2 by CRISPR-cas9 editing (CBX2^KO ) destabilized genome stability with increased spontaneous chromosomal breaks and tendency to polyploidy accompanied by disrupted cell cycle especially stalled G2/M transition and caused severe cell death. Wnt/β-catenin/LEF1/TCF7L1 was activated in surviving OVCAR4-CBX2^KO clones to bypass the crisis caused by loss of CBX2. The relieve of TCF7L1 core-promoter region occupied by CBX2 might be one of the possible explanations to TCF7L1 increase in OVCAR4-CBX2^KO clones. Subcutaneous tumor model further validated that depletion of CBX2 repressed HGSOC cell line derived tumor growth. High immunohistochemistry score of CBX2 in primary ovarian cancer tissue associated with advanced clinical stage (p = 0.033), poor overall survival (HR = 3.056, 95% CI: 1.024-9.123), and progression free survival (HR = 4.455, 95% CI: 1.513-13.118) in HGSOC. Overall, our results suggested that CBX2 was a promising prognostic factor and therapeutic target in HGSOC.

Understanding and targeting anoikis in metastasis for cancer therapies

The development of effective treatments for cancers requires investigations for a more detailed and comprehensive understanding of the basic cellular mechanisms involved in carcinogenesis, cancer progression, and metastasis. One of those driving mechanisms is anoikis, a special type of apoptosis, which is induced by losing anchorage from the extracellular matrix (ECM). In other words, resisting death in detached cells (cells without ECM) forms an anoikis-resistant phenotype. Since the anoikis-resistance state compensates for the initial steps of cancer metastasis, this review aimed to discuss mechanisms of gaining anoikis/anoikis resistance phenotype in tumor cells. Finally, we highlighted the significance of anoikis in malignancies so as to provide clear insight into cancer diagnosis and therapy development.

Chromobox proteins in cancer: Multifaceted functions and strategies for modulation (Review)

Chromobox (CBX) proteins are important epigenetic regulatory proteins and are widely involved in biological processes, such as embryonic development, the maintenance of stem cell characteristics and the regulation of cell proliferation and apoptosis. Disorder and dysfunction of CBXs in cancer usually lead to the blockade or ectoptic activation of developmental pathways, promoting the occurrence, development and progression of cancer. In the present review, the characteristics and functions of CBXs were first introduced. Subsequently, the expression of CBXs in cancers and the relationship between CBXs and clinical characteristics (mainly cancer grade, stage, metastasis and relapse) and prognosis were discussed. Finally, it was described how CBXs regulate cell proliferation and self‑renewal, apoptosis and the acquisition of malignant phenotypes, such as invasion, migration and chemoresistance, through mechanisms involving epigenetic modification, nuclear translocation, noncoding RNA interactions, transcriptional regulation, posttranslational modifications, protein‑protein interactions, signal transduction and metabolic reprogramming. The study also focused on cancer therapies targeting CBXs. The present review provides new insight and a comprehensive basis for follow‑up research on CBXs and cancer.

Regulators CDCA8 as potential targets and biomarkers for the prognosis of human skin cutaneous melanoma

Cutaneous melanoma (CM) is considered as the most malignant skin tumor with high distant metastasis and poor prognosis. Cell division cycle-associated protein (CDCA) family has a role in regulating cell proliferation and modulating immune cell and tumor cell proliferation in the tumor microenvironment to regulate tumor oncogenesis, development and affect patient outcomes. However, the differential expression pattern and prognostic value of CDCA factors (CDCAs) have not been clarified. In this study, the role of CDCAs in CM was analyzed by using bioinformatics and found that the transcriptional expressions of CDCA1/2/3/5/6/8 were upregulating in CM samples than in normal compares. CM patients with downregulated of CDCA1/3/4/5/6/8 and high transcriptional levels of CDCA7 suggest a significantly better prognosis. Furthermore, the significant correlations among the expression of CDCAs and the infiltration of immune cells. In terms of the protein level, we found CDCA8 was upregulated in CM patients. In conclusion, CDCA8 is a powerful prognostic biomarker for CM and can be a novel target for immunotherapy.

Construction of a Novel Oxidative Stress Response-Related Gene Signature for Predicting the Prognosis and Therapeutic Responses in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly heterogeneous malignancy with poor outcomes, and the assessment of its prognosis as well as its response to therapy is still challenging. In this study, we aimed to construct an oxidative stress response-related genes-(OSRGs-) based gene signature for predicting prognosis and estimating treatment response in patients with HCC. We integrated the transcriptomic data and clinicopathological information of HCC patients from The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC) databases. LASSO Cox regression analysis was utilized to establish an integrated multigene signature in the TCGA cohort, and its prediction performance was validated in the ICGC cohort. The CIBERSORT algorithm was employed to evaluate immune cell infiltration. The response rate to immune checkpoint inhibition (ICI) therapy was assessed using a TIDE platform. Drug activity data from the Cancer Genome Project and NCI-60 human cancer cell lines were used to predict sensitivity to chemotherapy. We successfully established a gene signature comprising G6PD, MT3, CBX2, CDKN2B, CCNA2, MAPT, EZH2, and SLC7A11. The risk score of each patient, which was determined by the multigene signature, was identified as an independent prognostic marker. The immune cell infiltration patterns, response rates to ICI therapy, and the estimated sensitivity of 89 chemotherapeutic drugs were associated with risk scores. Individual prognostic genes were also associated with susceptibility to various FDA-approved drugs. Our study indicates that a comprehensive transcriptomic analysis of OSRGs can provide a reliable molecular model to predict prognosis and therapeutic response in patients with HCC.

Expression and Prognostic Value of Chromobox Family Proteins in Esophageal Cancer

Background: Esophageal cancer (EC) is one of the most common human malignant tumors worldwide. Chromobox (CBX) family proteins are significant components of epigenetic regulatory complexes. It is reported that CBXs play critical roles in the oncogenesis and development of various tumors. Nonetheless, their functions and specific roles in EC remain vague and obscure. Methods and Materials: We used multiple bioinformatics tools, including Oncomine, Gene Expression Profiling Interactive Analysis 2 (GEPIA2), UALCAN, Kaplan–Meier plotter, cBioPortal, Metascape, TIMER2 and TISIDB, to investigate the expression profile, gene alterations and prognostic roles of CBX family proteins, as well as their association with clinicopathologic parameters, immune cells and immune regulators. In addition, RT-qPCR, Western blot, CCK8, colony formation, wound healing and transwell assays were performed to investigate the biological functions of CBX3 in EC cells. Results: CBX3 and CBX5 were overexpressed in EC compared to normal tissues. Survival analysis revealed that high expression of CBX1 predicted worse disease-free survival (DFS) in EC patients. Functionally, CBXs might participate in mismatch repair, spliceosome, cell cycle, the Fanconi anemia pathway, tight junction, the mRNA surveillance pathway and the Hippo signaling pathway in EC development. Furthermore, CBXs were related to distinct immune cells infiltration and immune regulators. Additionally, depletion of CBX3 inhibited the proliferation, migration and invasion abilities of EC cells. Conclusions: Our study comprehensively investigated the expression pattern, prognostic value, and gene alterations of CBXs in EC, as well as their relationships with clinicopathologic variables, immune cells infiltration and immune regulators. These results suggested that CBX family proteins, especially CBX3, might be potential biomarkers in the progression of EC.

Critical Roles of Polycomb Repressive Complexes in Transcription and Cancer

Polycomp group (PcG) proteins are members of highly conserved multiprotein complexes, recognized as gene transcriptional repressors during development and shown to play a role in various physiological and pathological processes. PcG proteins consist of two Polycomb repressive complexes (PRCs) with different enzymatic activities: Polycomb repressive complexes 1 (PRC1), a ubiquitin ligase, and Polycomb repressive complexes 2 (PRC2), a histone methyltransferase. Traditionally, PRCs have been described to be associated with transcriptional repression of homeotic genes, as well as gene transcription activating effects. Particularly in cancer, PRCs have been found to misregulate gene expression, not only depending on the function of the whole PRCs, but also through their separate subunits. In this review, we focused especially on the recent findings in the transcriptional regulation of PRCs, the oncogenic and tumor-suppressive roles of PcG proteins, and the research progress of inhibitors targeting PRCs.

The Epigenetic Regulatory Protein CBX2 Promotes mTORC1 Signalling and Inhibits DREAM Complex Activity to Drive Breast Cancer Cell Growth

Chromobox 2 (CBX2) is a chromatin-binding component of polycomb repressive complex 1, which causes gene silencing. CBX2 expression is elevated in triple-negative breast cancer (TNBC), for which there are few therapeutic options. Here, we aimed to investigate the functional role of CBX2 in TNBC. CBX2 knockdown in TNBC models reduced cell numbers, which was rescued by ectopic expression of wild-type CBX2 but not a chromatin binding-deficient mutant. Blocking CBX2 chromatin interactions using the inhibitor SW2_152F also reduced cell growth, suggesting CBX2 chromatin binding is crucial for TNBC progression. RNA sequencing and gene set enrichment analysis of CBX2-depleted cells identified downregulation of oncogenic signalling pathways, including mTORC1 and E2F signalling. Subsequent analysis identified that CBX2 represses the expression of mTORC1 inhibitors and the tumour suppressor RBL2. RBL2 repression, in turn, inhibits DREAM complex activity. The DREAM complex inhibits E2F signalling, causing cell senescence; therefore, inhibition of the DREAM complex via CBX2 may be a key oncogenic driver. We observed similar effects in oestrogen receptor-positive breast cancer, and analysis of patient datasets suggested CBX2 inhibits RBL2 activity in other cancer types. Therapeutic inhibition of CBX2 could therefore repress mTORC1 activation and promote DREAM complex-mediated senescence in TNBC and could have similar effects in other cancer types.

Diverse Chromobox Family Members: Potential Prognostic Biomarkers and Therapeutic Targets in Head and Neck Squamous Cell Carcinoma

Background

The Chromobox (CBX) family members were involved in a variety of physiological and oncological processes through the regulation of the epigenetic modification of chromatin. However, the comprehensive analysis of the CBX family in head and neck squamous cell carcinoma (HNSC) is lacking.

Methods

In this work, we used multiple online databases and tools to investigate the roles of CBX family in aspects of gene expression, prognostic evaluation, genetic alteration, immune micro-environment of tumor, and status of methylation.

Results

The mRNA expression levels of CBX1, CBX3, and CBX5 were aberrantly increased in patients with HNSC, while CBX7 was aberrantly decreased. Higher expression of CBX7 was significantly associated with longer OS. Within the 5–11% of genetic alteration rate of CBXs, CBX3 ranked the highest and CBX5/7 ranked the lowest. SPRR1B, S100A7, CASP14, CDSN, LCE3D were the top 5 neighbor genes with the strongest association with CBXs in HNSC patients. Signaling pathways such as epidermal cell differentiation, cornification, and peptide cross-linking were demonstrated to have a strong association with CBX genes. The profiles of immune cell infiltration had high similarity for the group of HNSC patients stratified by expression of CBXs. The methylation levels of CBX1 and CBX5 significantly decreased, while that of CBX7 significantly increased in HNSC samples when compared with normal tissue.

Conclusion

In conclusion, the CBX family showed its valuation for further investigation in HNSC. Our research highlighted that CBX7 had the potential to be a novel diagnostic and prognostic biomarker for patients with HNSC.

Mechanisms of Polycomb group protein function in cancer

Cancer arises from a multitude of disorders resulting in loss of differentiation and a stem cell-like phenotype characterized by uncontrolled growth. Polycomb Group (PcG) proteins are members of multiprotein complexes that are highly conserved throughout evolution. Historically, they have been described as essential for maintaining epigenetic cellular memory by locking homeotic genes in a transcriptionally repressed state. What was initially thought to be a function restricted to a few target genes, subsequently turned out to be of much broader relevance, since the main role of PcG complexes is to ensure a dynamically choregraphed spatio-temporal regulation of their numerous target genes during development. Their ability to modify chromatin landscapes and refine the expression of master genes controlling major switches in cellular decisions under physiological conditions is often misregulated in tumors. Surprisingly, their functional implication in the initiation and progression of cancer may be either dependent on Polycomb complexes, or specific for a subunit that acts independently of other PcG members. In this review, we describe how misregulated Polycomb proteins play a pleiotropic role in cancer by altering a broad spectrum of biological processes such as the proliferation-differentiation balance, metabolism and the immune response, all of which are crucial in tumor progression. We also illustrate how interfering with PcG functions can provide a powerful strategy to counter tumor progression.

CBX2 Induces Glioma Cell Proliferation and Invasion Through the Akt/PI3K Pathway

Glioma is the most common primary intracranial tumor. Abnormal expression of CBX2 (ChromoBox2) is associated with tumorigenesis and tumor development. TCGA data in UALCAN showed that CBX2 was overexpressed in glioma tissue. To confirm the role of CBX2 in glioma, we regulated the level of CBX2 and conducted colony formation, Transwell, and CCK-8 assays to verify the effect of CBX2. The results showed that CBX2 knockdown reduced glioma cell proliferation and invasion and that the cells were less tumorigenic. CBX2 overexpression induced glioma cell proliferation and invasion and glioma stem cell self-renewal. The animal experiments showed that CBX2 knockdown inhibited glioma growth and improved survival time. CBX2 knockdown inhibited activation of the Akt/PI3K pathway. epidermal growth factor rescued the effects of CBX2. CBX2 could induce the growth and invasion of glioma cells via the Akt/PI3K pathway.

Circ_0061140 knockdown inhibits tumorigenesis and improves PTX sensitivity by regulating miR-136/CBX2 axis in ovarian cancer

Background

Ovarian cancer is an aggressive tumor in women with high mortality. Paclitaxel (PTX) can be used for the chemotherapy of ovarian cancer. Here, the roles of circular_0061140 (circ_0061140) in PTX sensitivity and malignant progression of ovarian cancer are unveiled.

Methods

The expressions of circ_0061140, microRNA-136 (miR-136) and chromobox 2 (CBX2) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Protein expression was determined by western blot. The half maximal inhibitory concentration (IC₅₀) of PTX was determined by 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was investigated by cell counting kit-8 (CCK-8) and colony formation assays. Cell apoptosis was demonstrated by flow cytometry analysis. Cell migration and invasion were evaluated by transwell assay. The binding relationship between miR-136 and circ_0061140 or CBX2 was predicted by interactome or starbase online database, and identified by dual-luciferase reporter assay. The effects of circ_0061140 on tumor formation and PTX sensitivity in vivo were disclosed by tumor formation assay.

Results

Circ_0061140 and CBX2 expressions were upregulated, while miR-136 expression was downregulated in PTX-resistant tissues and cells compared with control groups. Circ_0061140 knockdown repressed cell proliferation, migration and invasion, and promoted cell apoptosis and PTX sensitivity; however, these effects were restrained by miR-136 RNAi. Additionally, circ_0061140 was a sponge of miR-136, and miR-136 bound to CBX2. Furthermore, circ_0061140 knockdown inhibited tumor formation and improved PTX sensitivity in vivo.

Conclusions

Circ_0061140 silencing repressed the progression and PTX resistance of ovarian cancer by downregulating CBX2 expression via sponging miR-136, which provided novel insight into studying the therapy of ovarian cancer with PTX.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00888-9.

Polycomb group proteins in cancer: multifaceted functions and strategies for modulation

Polycomb repressive complexes (PRCs) are a heterogenous collection of dozens, if not hundreds, of protein complexes composed of various combinations of subunits. PRCs are transcriptional repressors important for cell-type specificity during development, and as such, are commonly mis-regulated in cancer. PRCs are broadly characterized as PRC1 with histone ubiquitin ligase activity, or PRC2 with histone methyltransferase activity; however, the mechanism by which individual PRCs, particularly the highly diverse set of PRC1s, alter gene expression has not always been clear. Here we review the current understanding of how PRCs act, both individually and together, to establish and maintain gene repression, the biochemical contribution of individual PRC subunits, the mis-regulation of PRC function in different cancers, and the current strategies for modulating PRC activity. Increased mechanistic understanding of PRC function, as well as cancer-specific roles for individual PRC subunits, will uncover better targets and strategies for cancer therapies.

Immunological and prognostic significance of CBX2 expression in hepatocellular carcinoma

BACKGROUND

The number of cases of hepatocellular carcinoma (HCC), the sixth most common malignancy and the third leading cause of cancer death worldwide, has risen from 1.6 to 4.6 per 100000 people worldwide over the past 30 years. Guangxi has a high incidence of HCC in China, and its death rate ranks first in the spectrum of causes of tumor death in Guangxi, accounting for about 40% of all deaths from malignant tumors. Exploring the role of chromobox homolog 2 (CBX2) in HCC immunity will provide potential value for the treatment of this malignancy.

AIM

To investigate the expression of CBX2 and analyze its immunological and prognostic significance in HCC.

METHODS

The expression of CBX2 in 75 cases of HCC and matched non-tumor tissues was detected by tissue microarray and immunohistochemistry. The relationship of CBX2 expression with the clinicopathologic features of HCC and survival prognosis was analyzed. Then, the differential expression of CBX2 between HCC and normal tissues was verified in The Cancer Genomic Atlas (TCGA). Next, we explored the association between CBX2 expression and immunocyte infiltration, determined the relationship between CBX2 expression and immunosuppressors and immunostimulators, and identified the immune events that CBX2 was involved in through relevant GO and KEGG pathway enrichment analyses. A multi-gene risk prediction model was developed using a COX regression model, thereby generating a risk score that is an independent predictor of survival prognosis. ROC analysis was performed to assess the predictive accuracy of the risk score. Finally, a prognostic model with a calibration curve was constructed to predict the patients' survival probability at 3 and 5 years.

RESULTS

The positive expression of CBX2 in HCC tissue was 66.7% (50/75), which was significantly higher than that in matched non-tumor tissues (25.3% (19/75); P < 0.01). The expression of CBX2 was associated with TNM stage and AFP status (P < 0.05). The survival time of patients in the CBX2 positive group was significantly lower than that of the CBX2 negative group, suggesting that CBX2 positive expression may be related to the prognosis of HCC patients. TCGA database verification reached the same conclusion. The expression of CBX2 was positively correlated with the infiltration levels of T helper 2 cells. CBX2 was identified to be associated with 10 immunosuppressors and 23 immunostimulators, and enriched analysis of related GO and KEGG pathways showed that CBX2 was associated with immune events such as intestinal immune network for immunoglobulin A production, cytokine-cytokine receptor interactions, cell adhesion molecules, and rheumatoid arthritis.

CONCLUSION

CBX2 positive expression may be a prognostic risk factor in HCC patients. Our findings provide evidence for the role of CBX2 in tumor immunity in HCC, suggesting that CBX2 may be a potential immunoprognostic marker for HCC.

Long Noncoding RNA MIR100HG Knockdown Attenuates Hepatocellular Carcinoma Progression by Regulating MicroRNA-146b-5p/Chromobox 6

Purpose

Hepatocellular carcinoma (HCC) accounts for approximately ninety percent of primary liver cancer. This study attempted to investigate the effects of the long noncoding RNA MIR100HG (MIR100HG) in HCC and the underlying molecular mechanism.

Materials and Methods

qRT-PCR was implemented to analyze the expression of MIR100HG, microRNA-146b-5p (miR-146b-5p), and Chromobox 6 (CBX6). The correlation between MIR100HG and clinicopathological features of HCC patients was assessed. Additionally, the effects of MIR100HG knockdown on HCC cell viability, migration, and invasion were explored. The interactions among MIR100HG, miR-146b-5p, and CBX6 were confirmed. Furthermore, rescue experiments were conducted to investigate whether MIR100HG knockdown modulates HCC cell behaviors through modulating the miR-146b-5p/CBX6 axis.

Results

The expression of MIR100HG and CBX6 was enhanced, while miR-146b-5p was inhibited in HCC cells. High MIR100HG expression was positively associated with the TNM tumor stage and Edmondson-Steiner grading in HCC patients. MIR100HG knockdown considerably reduced the HCC cell viability, migration, and invasion. In addition, MIR100HG directly targeted miR-146b-5p, and miR-146b-5p directly targeted CBX6 in HCC cells. Moreover, miR-146b-5p suppression or CBX6 elevation evidently rescued the suppressed viability, migration, and invasion of HCC cells caused by MIR100HG knockdown.

Conclusions

Knockdown of MIR100HG inhibited the viability, migration, and invasion of HCC cells by targeting the miR-146b-5p/CBX6 axis, offering a potential therapeutic target for HCC therapy.

A Potent, Selective CBX2 Chromodomain Ligand and Its Cellular Activity During Prostate Cancer Neuroendocrine Differentiation

Polycomb group (PcG) proteins are epigenetic regulators that facilitate both embryonic development and cancer progression. PcG proteins form Polycomb repressive complexes 1 and 2 (PRC1 and PRC2). PRC2 trimethylates histone H3 lysine 27 (H3K27me3), a histone mark recognized by the N-terminal chromodomain (ChD) of the CBX subunit of canonical PRC1. There are five PcG CBX paralogs in humans. CBX2 in particular is upregulated in a variety of cancers, particularly in advanced prostate cancers. Using CBX2 inhibitors to understand and target CBX2 in prostate cancer is highly desirable; however, high structural similarity among the CBX ChDs has been challenging for developing selective CBX ChD inhibitors. Here, we utilize selections of focused DNA encoded libraries (DELs) for the discovery of a selective CBX2 chromodomain probe, SW2_152F. SW2_152F binds to CBX2 ChD with a Kd of 80 nM and displays 24-1000-fold selectivity for CBX2 ChD over other CBX paralogs in vitro. SW2_152F is cell permeable, selectively inhibits CBX2 chromatin binding in cells, and blocks neuroendocrine differentiation of prostate cancer cell lines in response to androgen deprivation.

Inhibiting Wnt/beta-catenin in CTNNB1-mutated endometrial cancer

The role of β-catenin/TCF transcriptional activity in endometrial cancer (EC) recurrence is not well understood. We assessed the impact of Wnt/β-catenin inhibition in EC models. In an analysis of the Cancer Genome Atlas, we confirmed that CTNNB1 mutations are enriched in recurrent low-risk EC and showed that aberrant Wnt/β-catenin pathway activation is associated with recurrence. We studied CTNNB1-wildtype (HEC1B, Ishikawa) and CTNNB1-mutant (HEC108, HEC265, HEC1B-S33Y, Ishikawa-S33Y) EC cell lines. Dose response curves were determined for 5 Wnt/β-catenin pathway inhibitors (Wnt-C59, XAV-939, PyrPam, PRI-724, SM04690). XAV939, Wnt-C59 and PyrPam inhibited function upstream of β-catenin transcriptional activity and were ineffective at inhibiting cell viability. In contrast, PRI724 and SM04690 indirectly inhibited β-catenin transcriptional activity and significantly reduced cell viability in CTNNB1-mutant cell lines. Treatment with SM04690 reduced cell viability (Licor Cell stain) in all EC cell lines, but viability was significantly lower in CTNNB1-mutant cell lines (p < 0.01). Mechanistically, SM04690 significantly inhibited proliferation measured via 5'-bromo-2'-deoxyuridine incorporation and reduced T cell factor (TCF) transcriptional activity. HEC1B, HEC1B-S33Y and HEC265 tumor-bearing mice were treated with vehicle or SM04690. Tumors treated with SM04690 had smaller mean volumes than those treated with vehicle (p < 0.001, p = 0.014, p = 0.06). In HEC1B-S33Y and HEC265 tumors, SM04690 treatment significantly reduced Ki67 H-scores compared to vehicle (p = 0.035, p = 0.024). Targeting the Wnt/β-catenin pathway in CTNNB1-mutant EC effectively inhibited proliferation and β-catenin/TCF transcriptional activity and blunted tumor progression in in vivo models. These studies suggest β-catenin transcriptional inhibitors are effective in EC and particularly in CTNNB1-mutant EC, highlighting a potential therapeutic vulnerability for treatment of CTNNB1-mutant EC.

The roles of Polycomb repressive complexes in mammalian development and cancer

More than 80 years ago, the first Polycomb-related phenotype was identified in Drosophila melanogaster. Later, a group of diverse genes collectively called Polycomb group (PcG) genes were identified based on common mutant phenotypes. PcG proteins, which are well-conserved in animals, were originally characterized as negative regulators of gene transcription during development and subsequently shown to function in various biological processes; their deregulation is associated with diverse phenotypes in development and in disease, especially cancer. PcG proteins function on chromatin and can form two distinct complexes with different enzymatic activities: Polycomb repressive complex 1 (PRC1) is a histone ubiquitin ligase and PRC2 is a histone methyltransferase. Recent studies have revealed the existence of various mutually exclusive PRC1 and PRC2 variants. In this Review, we discuss new concepts concerning the biochemical and molecular functions of these new PcG complex variants, and how their epigenetic activities are involved in mammalian development and cancer.

Targeting the tumour microenvironment in platinum-resistant ovarian cancer

Ovarian cancer typically presents at an advanced stage, and although the majority of cases initially respond well to platinum-based therapies, chemoresistance almost always occurs leading to a poor long-term prognosis. While various cellular autonomous mechanisms contribute to intrinsic or acquired platinum resistance, the tumour microenvironment (TME) plays a central role in resistance to therapy and disease progression by providing cancer stem cell niches, promoting tumour cell metabolic reprogramming, reducing chemotherapy drug perfusion and promoting an immunosuppressive environment. As such, the TME is an attractive therapeutic target which has been the focus of intense research in recent years. This review provides an overview of the unique ovarian cancer TME and its role in disease progression and therapy resistance, highlighting some of the latest preclinical and clinical data on TME-targeted therapies. In particular, it focuses on strategies targeting cancer-associated fibroblasts, tumour-associated macrophages, cancer stem cells and cancer cell metabolic vulnerabilities.

Chromobox 2 Expression Predicts Prognosis After Curative Resection of Oesophageal Squamous Cell Carcinoma

BACKGROUND/AIM

To investigate the function of chromobox 2 (CBX2) in oesophageal squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

We used real-time quantitative reverse transcription PCR (qRT-PCR) and immunohistochemistry to determine CBX2 expression levels in 13 human OSCC cell lines and clinical specimens of two independent cohorts of patients with OSCC.

RESULTS

PCR array analysis revealed that CBX2 was co-ordinately expressed with WNT5B in OSCC cell lines. RT-qPCR analysis of clinical samples revealed a high tumour-specific CBX2 expression compared with normal oesophageal tissues. High CBX2 expression was significantly associated with shorter disease-specific survival, hematogenous recurrence, and overall recurrence. Analysis of tissue microarrays of one cohort revealed that patients with higher CBX2 levels tended to have a shorter disease-specific survival.

CONCLUSION

CBX2 overexpression in OSCC tissues may serve as a novel biomarker for predicting survival and hematogenous recurrence.

Chromobox 4 facilitates tumorigenesis of lung adenocarcinoma through the Wnt/β-catenin pathway

Chromobox 4 (CBX4) is a core component of polycomb-repressive complex 1 with important roles in cancer biology and tissue homeostasis. Aberrant expression of CBX4 has been implicated in several human malignancies. However, its role and underlying mechanisms in the tumorigenesis of lung adenocarcinoma (LUAD) have not been defined in vivo. Here, we found that expression of CBX4 was frequently up-regulated in human LUAD samples and correlated with poor patient survival. Importantly, genetic ablation of CBX4 greatly dampened lung tumor formation and improved survival in the Kras^G12D/P53^L/L (KP) autochthonous mouse model of LUAD. In addition, CBX4 depletion significantly inhibited proliferation and anchorage-independent growth of KP mouse embryonic fibroblasts. Moreover, ectopic CBX4 expression clearly promoted proliferation and anchorage-independent growth in both human and mouse LUAD cells, whereas silencing of CBX4 exerted opposite effects. Mechanistically, CBX4 promoted growth of LUAD cells through activation of the Wnt/β-catenin pathway. Furthermore, expression levels of CBX4 were positively correlated with β-catenin in human LUAD samples. In conclusion, our data suggest that CBX4 plays an oncogenic role via the Wnt/β-catenin pathway and could serve as a potential therapeutic target in LUAD.

CBX2 depletion inhibits the proliferation, invasion and migration of gastric cancer cells by inactivating the YAP/β-catenin pathway

Gastric cancer (GC) is the most common and fast-growing malignancy of the digestive system, which has a high mortality. Chromobox homolog 2 (CBX2) has been reported to be highly expressed in cancer tissues compared with adjacent normal tissues. It has also been established that CBX2 is upregulated in GC cell lines by searching the Cancer Cell Line Encyclopedia. The aim of the present study was to investigate the biomolecular role and underlying mechanism of CBX2 in the proliferation, invasion and migration of GC cells. Short hairpin RNA-CBX2 and yes-associated protein (YAP) overexpression plasmids were constructed to regulate CBX2 and YAP expression, respectively. Additionally, the expression of certain mRNAs and proteins involved in the YAP/β-catenin pathway and those associated with cell invasion were assessed by western blotting and reverse transcription-quantitative PCR, respectively. The cellular behaviors of MFC cells were analyzed using Cell Counting Kit-8, colony formation wound-healing and Transwell assays. The results of the present study revealed that increased CBX2 expression was observed in GC cell lines compared with normal gastric cells. In addition, CBX2 knockdown inhibited the nuclear cytoplasm translocation of YAP, inducing its phosphorylation, and suppressing the activation of the β-catenin signaling pathway. The results also demonstrated that CBX2 depletion inhibited the proliferation, migration and invasion of GC cells by inactivating the YAP/β-catenin pathway. It was determined that CBX2 promoted the proliferation, invasion and migration of GC cells by activating the YAP/β-catenin pathway, suggesting that CBX2 is involved in the pathogenesis of GC and may represent a novel target for the clinical treatment of GC.

RAD51AP1 promotes progression of ovarian cancer via TGF-β/Smad signalling pathway

Ovarian cancer (OC) is one of the leading causes of female deaths. However, the molecular pathogenesis of OC has still remained elusive. This study aimed to explore the potential genes associated with the progression of OC. In the current study, 3 data sets of OC were downloaded from the GEO database to identify hub gene. Somatic mutation data obtained from TCGA were used to analyse the mutation. Immune cells were used to estimate effect of the hub gene to the tumour microenvironment. RNA‐seq and clinical data of OC patients retrieved from TCGA were used to investigate the diagnostic and prognostic values of hub gene. A series of in vitro assays were performed to indicate the function of hub gene and its possible mechanisms in OC. As a result, RAD51AP1 was found as a hub gene, which expression higher was mainly associated with poor survival in OC patients. Up‐regulation of RAD51AP1 was closely associated with mutations. RAD51AP1 up‐regulation accompanied by accumulated Th2 cells, but reduced CD4 + T cells and CD8 + T cells. Nomogram demonstrated RAD51AP1 increased the accuracy of the model. Down‐regulation of RAD51AP1 suppressed proliferation, migration and invasion capabilities of OC cells in vitro. Additionally, scatter plots showed that RAD51AP1 was positively correlated with genes in TGF‐β/Smad pathway. The above‐mentioned results were validated by RT‐qPCR and Western blotting. In conclusion, up‐regulation of RAD51AP1 was closely associated with mutations in OC. RAD51AP1 might represent an indicator for predicting OS of OC patients. Besides, RAD51AP1 might accelerate progression of OC by TGF‐β/Smad signalling pathway.

Development of a macrophages-related 4-gene signature and nomogram for the overall survival prediction of hepatocellular carcinoma based on WGCNA and LASSO algorithm

BACKGROUND

Immune system instability and poor prognosis are the two major clinical performance of hepatocellular carcinoma (HCC). Abnormal expression of MiR-424-5p has been reported to accelerate the progression of liver cancer, but it mediated immune cell infiltration imbalance is still unknown. We aim to mine the immune-related genes (IRGs) targeted by miR-424-5p and construct a multi-gene signature to improve the prognostic prediction of HCC.

METHODS

The HCC-related data of the cancer genome atlas (TCGA) database and the GSE14520 dataset of the gene expression omnibus (GEO) database were downloaded as the discovery dataset and the validation dataset, respectively. Weighted gene co-expression network analysis (WGCNA), the deconvolution algorithm of CIBERSORT and LASSO algorithm participated in the identification of IRGs and the development of prognostic signature and nomogram.

RESULTS

Our study found that the abundance of macrophages M0, M1 and M2 are all drastically changed during the cancerous process. A total of 920 macrophages infiltration-related LRGs were identified and a novel 4-gene signature (CDCA8, CBX2, UCK2 and SOCS2) with superior prognostic independence was established. The prognostic signature based risk score has superior capability to identify high-risk patients and predict overall survival (p < 0.001; AUC = 0.798 for 1 year; AUC = 0.748 for 3 years; AUC = 0.721 for 5 years). And it (C-index = 0.726) has a better prognostic potential than the TNM stage (C-index = 0.619), which is widely adopted in clinical practice. Additionally, the nomogram formed by combining the risk score and TNM stage further improved the accuracy of survival prediction (C-index = 0.733).

CONCLUSION

In summary, the immune landscape with abnormal infiltration of macrophages may be one of the prelude to the cancerous process. The novel macrophages-related 4-gene signature is expected to become a potential prognostic marker in liver cancer.

Identification of the Roles of Chromobox Family Members in Gastric Cancer: A Study Based on Multiple Datasets

Background

As the important components in polycomb repressive complexes 1 (PRC1) and heterochromatin protein 1 (HP1), Chromobox (CBX) family members are involved in epigenetic regulatory function, transcriptional repression, and other cellular metabolisms. Increasing studies have indicated significant associations between CBX and tumorigenesis, which is a progression in different types of cancers. However, the information about the roles of each CBX in gastric cancer is extremely limited.

Methods

We explored CBX mRNA expression, corrections with clinicopathological parameters, protein expression, prognostic values, enrichment analysis with several databases including Oncomine, Human Protein Atlas, UALCAN, Kaplan-Meier plotter, cBioPortal, GeneMANIA, and Enrichr.

Results

In our study, comparing to the normal tissues, higher mRNA expression of CBX1/2/3/4/5/8 and lower mRNA expression of CBX7 were found in GC tissues while upregulations of CBX1/2/3/4/5/8 and downregulations of CBX7 were indicated to be significantly correlated to the nodal metastasis status and individual cancer stages in GC patients. As for protein level, the expression of CBX2/3/4/5/6 was higher and the expression of CBX7 was lower in the GC tissues than those in the normal. What is more, higher mRNA expression of CBX1/5/6/8 and lower mRNA expression of CBX7 were markedly correlated to poor outcomes of OS and FP in GC patients. Besides, high mutation rate of CBXs (42%) was observed in GC patients.

Conclusions

We suggest that CBX5/7 may serve as potential therapeutic targets for GC while CBX1/8 may serve as potential prognostic indicators for GC.

Bioinformatic analysis of the expression and prognostic value of chromobox family proteins in human breast cancer

Chromobox (CBX) family proteins control chromatin structure and gene expression. However, the functions of CBXs in cancer progression, especially breast cancer, are inadequately studied. We assessed the significance of eight CBX proteins in breast cancer. We performed immunohistochemistry and bioinformatic analysis of data from Oncomine, GEPIA Dataset, bcGenExMiner, Kaplan–Meier Plotter, and cBioPortal. We compared mRNA and protein expression levels of eight CBX proteins between breast tumor and normal tissue. The expression difference of CBX7 was the greatest, and CBX7 was downregulated in breast cancer tissues compared with normal breast tissues. The expression of CBX2 was strongly associated with tumor stage. We further analyzed the association between the eight CBX proteins and the following clinicopathological features: menopause age, estrogen receptor (ER), progesterone receptor (PR) and HER-2 receptor status, nodal status, P53 status, triple-negative status, and the Scarff–Bloom–Richardson grade (SBR) and Nottingham prognostic index (NPI). Survival analysis in the Kaplan–Meier Plotter database showed that the eight CBX proteins were significantly associated with prognosis. Moreover, CBX genes in breast cancer patients had a high net alteration frequency of 57%. There were significant co-expression correlations between the following CBX protein pairs: CBX4 positively with CBX8, CBX6 positively with CBX7, and CBX2 negatively with CBX7. We also analyzed the Gene Ontology enrichment of the CBX proteins, including biological processes, cellular components, and molecular functions. CBX 1/2/3/5/8 may be oncogenes for breast cancer, whereas CBX 6 and 7 may be tumor suppressors for breast cancer. All eight CBX proteins may be predictive for prognosis. Clinical trials are needed to confirm the significance of the eight CBX proteins in breast cancer.

Proteasomal degradation of polycomb-group protein CBX6 confers MMP-2 expression essential for mesothelioma invasion

The aggressive invasiveness of malignant mesothelioma limits cancer therapy, however, the molecular mechanisms underlying the invasiveness remain largely unknown. Here we found that the matrix metalloproteinase-2 (MMP-2) was required for the invasion of mesothelioma cells in the collagen matrix and the gene expression of MMP-2 was correlated with the invasive phenotype. The MMP-2 gene expression was regulated by DNA and histone methylation around the transcription start site, implicating the involvement of the polycomb repressive complex (PRC). Knockdown of PRC component chromobox 6 (CBX6) promoted MMP-2 expression and invasion of mesothelioma cells. Transcriptome analysis suggested that CBX6 regulates sets of genes involved in cancer cell migration and metastasis. In invasive but not non-invasive cells, CBX6 was constantly unstable owing to ubiquitination and protein degradation. In human tissues, CBX6 localized in the nuclei of normal mesothelium and benign mesothelioma, but the nuclear staining of CBX6 was lost in malignant mesothelioma. These results suggest involvement of proteasomal degradation of CBX6 in mesothelioma progression.

Comprehensive analysis of the prognosis for chromobox family in gastric cancer

Background

Chromobox (CBX) family proteins are a class of transcriptional repressors involved in epigenetic regulation and developmental processes of various tumors, including gastric cancer. However, the function and prognosis of different CBXs in gastric cancer remain unknown.

Methods

This study addresses this issue by synthesizing several mainstream databases (Oncomine, GEPIA2, cBioportal, and Kaplan-Meier plotter, among others) that currently contain many tumor samples and provide very reliable analysis results, investigating the role of CBXs in the prognosis of gastric cancer.

Results

The mRNA of CBX1/2/3/4/5/8 was highly expressed in gastric cancer, the mRNA of CBX7 was lowly expressed in gastric cancer, and the mRNA expression of CBX6 was not significantly different in CRC. Besides, high and low CBXs mRNA expression correlated with cancer stage, node metastasis status, H. pylori infection status, and tumor grade in CRC patients. We found that high mRNA expression of CBX4/5/6/7/8 was significantly associated with worse overall survival (OS), progression-free survival (FP), and post-progression survival (PPS) in a large number of CRC patients. High mRNA expression of CBX3 was significantly associated with better OS and FP. We also found that none of the eight CBXs family genes had a mutation rate of less than 5% in gastric cancer, and the highest mutation rate was in CBX3 (14%).

Conclusions

These results suggest that CBX3/4/5/6/7/8 could be a prognostic biomarker in gastric cancer patients.

LncRNA PCAT6 promotes the proliferation, migration and invasion of pancreatic ductal adenocarcinoma via regulating miR-185-5p/CBX2 axis

Emerging evidence has revealed markedly roles for long noncoding RNAs (lncRNAs) in various cancer processes. Prostate cancer associated transcript 6 (PCAT6) is a novel lncRNA which displays vital regulatory functions in multiple cancers. However, the functions of PCAT6 in pancreatic ductal adenocarcinoma (PDAC) remain unclear. Our study confirmed that PCAT6 expression was upregulated in PDAC and the expression of PCAT6 was related to TNM stage, lymph node invasion and overall survival of PDAC patients. PCAT6 might act as an effective tumor biomarker for PDAC patients. Moreover, knockdown of PCAT6 inhibited cell proliferation, migration and invasion of PDAC in vitro. For the mechanism, miR-185-5p expression was decreased and chromobox 2 (CBX2) expression was increased in PDAC, and further PCAT6 could upregulated the expression of oncogene CBX2 by sponging miR-185-5p. The results above suggested that PCAT6/miR-185-5p/CBX2 exerted crucial functions in tumorigenesis and progression of PDAC.

The Prognostic Value of the Chromobox Family in Human Ovarian Cancer

Ovarian cancer is one of the most lethal gynecologic tumors in women and has a poor prognosis. The purpose of our study was to identify new prognostic markers in ovarian cancer. We examined the prognostic roles of mRNA expression of the chromobox (CBX) family in patients with ovarian cancer utilizing the Kaplan-Meier plotter database. The prognostic values and expression levels of CBX members associated with prognosis were further evaluated using KM plotter in diverse subgroups and immunohistochemistry (IHC) analysis in ovarian carcinoma. The results revealed that elevated CBX1-3 mRNA expression may predict poor overall survival (OS) and progression-free survival (PFS) outcomes in patients with ovarian cancer. Notably, in women with ovarian cancer, increased CBX1 mRNA expression was linked to a short OS in all stages and in the grade II and grade III subgroups. Additionally, CBX2 and CBX3 were strongly related to short OS in stage III+IV patients, and a link between high CBX3 mRNA expression and unfavorable OS in grade II patients was observed. High expression levels of CBX1 and CBX3 were significantly associated with chemotherapy resistance in ovarian cancer patients. IHC staining showed that the CBX1-3 proteins were upregulated in serous ovarian carcinoma tissues compared with normal ovarian tissues. Therefore, our results indicated that CBX1-3 could be attractive biomarkers for predicting poor prognosis of ovarian cancer.

Targeting Fatty Acid Oxidation to Promote Anoikis and Inhibit Ovarian Cancer Progression

Epithelial-derived high-grade serous ovarian cancer (HGSOC) is the deadliest gynecologic malignancy. Roughly 80% of patients are diagnosed with late-stage disease, which is defined by wide-spread cancer dissemination throughout the pelvic and peritoneal cavities. HGSOC dissemination is dependent on tumor cells acquiring the ability to resist anoikis (apoptosis triggered by cell detachment). Epithelial cell detachment from the underlying basement membrane or extracellular matrix leads to cellular stress, including nutrient deprivation. In this report, we examined the contribution of fatty acid oxidation (FAO) in supporting anoikis resistance. We examined expression Carnitine Palmitoyltransferase 1A (CPT1A) in a panel of HGSOC cell lines cultured in adherent and suspension conditions. With CPT1A knockdown cells, we evaluated anoikis by caspase 3/7 activity, cleaved caspase 3 immunofluorescence, flow cytometry, and colony formation. We assessed CPT1A-dependent mitochondrial activity and tested the effect of exogenous oleic acid on anoikis and mitochondrial activity. In a patient-derived xenograft model, we administered etomoxir, an FAO inhibitor, and/or platinum-based chemotherapy. CPT1A is overexpressed in HGSOC, correlates with poor overall survival, and is upregulated in HGSOC cells cultured in suspension. CPT1A knockdown promoted anoikis and reduced viability of cells cultured in suspension. HGSOC cells in suspension culture are dependent on CPT1A for mitochondrial activity. In a patient-derived xenograft model of HGSOC, etomoxir significantly inhibited tumor progression. IMPLICATIONS: Targeting FAO in HGSOC to promote anoikis and attenuate dissemination is a potential approach to promote a more durable antitumor response and improve patient outcomes.

Unmasking Intra-tumoral Heterogeneity and Clonal Evolution in NF1-MPNST

Sarcomas are highly aggressive cancers that have a high propensity for metastasis, fail to respond to conventional therapies, and carry a poor 5-year survival rate. This is particularly true for patients with neurofibromatosis type 1 (NF1), in which 8%–13% of affected individuals will develop a malignant peripheral nerve sheath tumor (MPNST). Despite continued research, no effective therapies have emerged from recent clinical trials based on preclinical work. One explanation for these failures could be the lack of attention to intra-tumoral heterogeneity. Prior studies have relied on a single sample from these tumors, which may not be representative of all subclones present within the tumor. In the current study, samples were taken from three distinct areas within a single tumor from a patient with an NF1-MPNST. Whole exome sequencing, RNA sequencing, and copy number analysis were performed on each sample. A blood sample was obtained as a germline DNA control. Distinct mutational signatures were identified in different areas of the tumor as well as significant differences in gene expression among the spatially distinct areas, leading to an understanding of the clonal evolution within this patient. These data suggest that multi-regional sampling may be important for driver gene identification and biomarker development in the future.