Pseudogenes in Human Cancer

Coding, or non-coding, that is the question

The advent of high-throughput sequencing uncovered that our genome is pervasively transcribed into RNAs that are seemingly not translated into proteins. It was also found that non-coding RNA transcripts outnumber canonical protein-coding genes. This mindboggling discovery prompted a surge in non-coding RNA research that started unraveling the functional relevance of these new genetic units, shaking the classic definition of "gene". While the non-coding RNA revolution was still taking place, polysome/ribosome profiling and mass spectrometry analyses revealed that peptides can be translated from non-canonical open reading frames. Therefore, it is becoming evident that the coding vs non-coding dichotomy is way blurrier than anticipated. In this review, we focus on several examples in which the binary classification of coding vs non-coding genes is outdated, since the same bifunctional gene expresses both coding and non-coding products. We discuss the implications of this intricate usage of transcripts in terms of molecular mechanisms of gene expression and biological outputs, which are often concordant, but can also surprisingly be discordant. Finally, we discuss the methodological caveats that are associated with the study of bifunctional genes, and we highlight the opportunities and challenges of therapeutic exploitation of this intricacy towards the development of anticancer therapies.

PART1 facilitates tumorigenesis and inhibits ferroptosis by regulating the miR-490-3p/SLC7A11 axis in hepatocellular carcinoma

BACKGROUND

Ferroptosis is associated with cancer progression and has a promising application for treating hepatocellular carcinoma (HCC). Long non-coding RNA (lncRNA) participates widely in the regulation of ferroptosis, but the key lncRNA regulators implicated in ferroptosis and their molecular mechanisms remain to be identified.

METHODS

Bioinformatic analysis was performed in R based on The Cancer Genome Atlas Program (TCGA) public database. The relative expression of genes was detected by real-time quantitative PCR. Cell viability was assessed by the CCK8 assay. The cell cycle and apoptosis were detected by flow cytometry. Migration and invasion of HCC cells were detected by Transwell assay and wound healing assay. Expression of relevant proteins was detected by Western blotting. A dual-luciferase reporter assay was used to detect interactions between PART1 (or SLC7A11) and miR-490-3p.

RESULTS

The PART1/miR-490-3p/SLC7A11 axis was identified as a potential regulatory pathway of ferroptosis in HCC. PART1 silencing reduced HCC cell proliferation, migration, and metastasis and promoted apoptosis and erastin-reduced ferroptosis. Further investigation revealed that PART1 acted as a competitive endogenous RNA (ceRNA) for miR-490-3p to enhance SLC7A11 expression. Overexpression of miR-490-3p downregulated the expression of SLC7A11, inhibiting the proliferation, invasion, and metastasis of HCC cells while promoting apoptosis and erastin-induced ferroptosis. Knockdown of PART1 in HCC cells significantly improved the sensitivity of HCC cells to sorafenib.

CONCLUSION

Our results revealed that the PART1/miR-490-3p/SLC7A11 axis enhances HCC cell malignancy and suppresses ferroptosis, which provides a new perspective for understanding of the function of long chain non-coding RNAs in HCC. The PART1/miR-490-3p/SLC7A11 axis may be target for improving sorafenib sensitivity in HCC.

Prognostic significance of CHCHD2P9 and ZNF204P in breast cancer: exploring their expression patterns and associations with malignancy-related genes

BACKGROUND

Non-coding RNAs (ncRNAs) have a crucial impact on diverse cellular processes, influencing the progression of breast cancer (BC). The objective of this study was to identify novel ncRNAs in BC with potential effects on patient survival and disease progression.

METHODS

We utilized the cancer genome atlas data to identify ncRNAs associated with BC pathogenesis. We explored the association between these ncRNA expressions and survival rates. A risk model was developed using candidate ncRNA expression and beta coefficients obtained from a multivariate Cox regression analysis. Co-expression networks were constructed to determine potential relationships between these ncRNAs and molecular pathways. For validation, we employed BC samples and the RT-qPCR method.

RESULTS

Our findings revealed a noteworthy increase in the expression of AC093850.2 and CHCHD2P9 in BC, which was correlated with a poor prognosis. In contrast, ADAMTS9-AS1 and ZNF204P displayed significant downregulation and were associated with a favorable prognosis. The risk model, incorporating these four ncRNAs, robustly predicted patient survival. The co-expression network showed an effective association between levels of AC093850.2, CHCHD2P9, ADAMTS9-AS1, and ZNF204P and genes involved in pathways like metastasis, angiogenesis, metabolism, and DNA repair. The RT-qPCR results verified notable alterations in the expression of CHCHD2P9 and ZNF204P in BC samples. Pan-cancer analyses revealed alterations in the expression of these two ncRNAs across various cancer types.

CONCLUSION

This study presents a groundbreaking discovery, highlighting the substantial dysregulation of CHCHD2P9 and ZNF204P in BC and other cancers, with implications for patient survival.

Transforming 'Junk' DNA into Cancer Warriors: The Role of Pseudogenes in Hepatocellular Carcinoma

In the dynamic landscape of hepatocellular carcinoma (HCC) or the liver cancer research, pseudogenes have emerged from the shadows of genetic obscurity to become central figures, significantly influencing the disease molecular development and clinical trajectory. This review explores a transformative shift in perspective, recognizing pseudogenes not as genetic remnants without function, but as critical regulators in the molecular underpinnings of HCC. Engaging in complex interactions such as microRNA sponging, gene expression modulation, and signaling pathway disruptions, pseudogenes orchestrate a part of the molecular complexity driving tumor genesis, progression, and drug resistance in the liver cancer. Their unique expression patterns in hepatoma tissues herald new opportunities for early HCC detection, offering insights into patient prognosis, and identifying novel targets for therapeutic intervention of this disease. Such advancements underscore the importance of pseudogenes in enriching our understanding and management of HCC, paving the way for more effective diagnostic strategies and targeted therapies in the ongoing battle against this challenging malignancy.

Identification of potential pseudogenes for predicting the prognosis of hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) remains a highly deadly malignant tumor with high recurrence and metastasis rates. Cancer stem cells (CSCs) are involved in tumor metastasis, recurrence, and resistance to drugs, which have attracted widespread attention in recent years. Research has shown that pseudogenes may regulate stemness to promote the progression of HCC, but its specific mechanisms and impact on prognosis remain unclear.

METHODS

In this study, clinical prognosis information of HCC was first downloaded from The Cancer Genome Atlas (TCGA) database. Then we calculated the mRNA expression-based stemness index (mRNAsi) of HCC. We also screened the differentially expressed pseudogene (DEPs) and conducted univariate Cox regression analysis to investigate their effect on the prognosis of HCC. Further, genomic mutation frequency analysis and weighted gene co-expression network analysis (WGCNA) were performed to compare the role of pseudogenes and stemness in promoting the progression of HCC. Finally, we conducted the correlation analysis to examine the potential mechanism of pseudogenes regulating stemness to promote the progression of HCC and detected the possible pathways through the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis.

RESULTS

Herein, we revealed that the high stemness of HCC correlated with an unfavorable prognosis. We obtained 31 up-regulated and 8 down-regulated DEPs in HCC and screened CTB-63M22.1, a poor prognostic indicator of HCC. In addition, CTB-63M22.1 had a mutation frequency similar to mRNAsi and acted in a module similar to that of mRNAsi on HCC. We then screened two RNA-binding proteins (RBPs) LIN28B and NOP56 with the highest correlation with stemness. We also discovered that they were primarily enriched in the biological process as examples of mitotic nuclear division and cell cycle.

CONCLUSIONS

Collectively, these results revealed that pseudogenes CTB-63M22.1 may regulate cancer stemness by regulating RBPs, suggesting that CTB-63M22.1 may serve as an innovative therapeutic target and a reliable prognostic marker for HCC.

Pseudogenes in Cancer: State of the Art

Pseudogenes are duplicates of protein-coding genes that have accumulated multiple detrimental alterations, rendering them unable to produce the protein they encode. Initially disregarded as "junk DNA" due to their perceived lack of functionality, research on their biological roles has been hindered by this assumption. Nevertheless, recent focus has shifted towards these molecules due to their abnormal expression in cancer phenotypes. In this review, our objective is to provide a thorough overview of the current understanding of pseudogene formation, the mechanisms governing their expression, and the roles they may play in promoting tumorigenesis.

Finding miRNA-RNA Network Biomarkers for Predicting Metastasis and Prognosis in Cancer

Despite remarkable progress in cancer research and treatment over the past decades, cancer ranks as a leading cause of death worldwide. In particular, metastasis is the major cause of cancer deaths. After an extensive analysis of miRNAs and RNAs in tumor tissue samples, we derived miRNA-RNA pairs with substantially different correlations from those in normal tissue samples. Using the differential miRNA-RNA correlations, we constructed models for predicting metastasis. A comparison of our model to other models with the same data sets of solid cancer showed that our model is much better than the others in both lymph node metastasis and distant metastasis. The miRNA-RNA correlations were also used in finding prognostic network biomarkers in cancer patients. The results of our study showed that miRNA-RNA correlations and networks consisting of miRNA-RNA pairs were more powerful in predicting prognosis as well as metastasis. Our method and the biomarkers obtained using the method will be useful for predicting metastasis and prognosis, which in turn will help select treatment options for cancer patients and targets of anti-cancer drug discovery.

PA2G4P4 Promotes Glioma Cell Migration and Tumorigenesis through the PTEN/AKT/mTOR Signaling Pathway

Dysregulation of pseudogene expression is closely related to the progression of various cancers, including glioma. Proliferation-associated 2G4 pseudogene 4 (PA2G4P4) could affect cell viability and apoptosis of glioma cells. However, the specific regulatory mechanism of PA2G4P4 is not clear. In this paper, we found that PA2G4P4 overexpres-sion promoted glioma cell proliferation, migration and cell cycle progression, whereas PA2G4P4 knockdown inhibited cancer progression. Knockdown of PA2G4P4 also suppressed the tumorigenesis of glioma cells in vivo. Furthermore, knockdown of PA2G4 after overexpression of PA2G4P4 decreased the cell viability and migration ability to normal level. The protein level of a tumor suppressor gene phosphatase and tensing homolog (PTEN) was greatly decreased in U87 cells after PA2G4P4 overexpression, while increased after PA2G4 knockdown; on the contrary, the protein levels of P-AKT and P-S6 were obviously induced in U87 cells after PA2G4P4 overexpression, and decreased after PA2G4 knockdown. The cell ability, colony formation ability and cell migration ability were all recovered to normal level by adding an AKT inhibitor MK2206 to the glioma cells, which were induced by PA2G4P4 overexpression. Our results revealed that PA2G4P4 could regulate glioma cell proliferation and migration through PTEN/AKT/mTOR signaling pathway by targeting PA2G4 gene. PA2G4P4 may become a target for glioma treatment.

Analysis of regulatory sequences in exosomal DNA of NANOGP8

Exosomes participate in intercellular communication by transporting functionally active molecules. Such cargo from the original cells comprising proteins, micro-RNA, mRNA, single-stranded (ssDNA) and double-stranded DNA (dsDNA) molecules pleiotropically transforms the target cells. Although cancer cells secrete exosomes carrying a significant level of DNA capable of modulating oncogene expression in a recipient cell, the regulatory mechanism is unknown. We have previously reported that cancer cells produce exosomes containing NANOGP8 DNA. NANOGP8 is an oncogenic paralog of embryonic stem cell transcription factor NANOG and does not express in cells since it is a pseudogene. However, in this study, we evaluated NANOGP8 expression in glioblastoma multiforme (GBM) tissue from a surgically removed brain tumor of a patient. Significantly higher NANOGP8 transcription was observed in GBM cancer stem cells (CSCs) than in GBM cancer cells or neural stem cells (NSCs), despite identical sequences of NANOGP8-upstream genomic region in all the cell lines. This finding suggests that upstream genomic sequences of NANOGP8 may have environment-dependent promoter activity. We also found that the regulatory sequences upstream of exosomal NANOGP8 GBM DNA contain multiple core promoter elements, transcription factor binding sites, and segments of human viruses known for their oncogenic role. The exosomal sequence of NANOGP8-upstream GBM DNA is different from corresponding genomic sequences in CSCs, cancer cells, and NSCs as well as from the sequences reported by NCBI. These sequence dissimilarities suggest that exosomal NANOGP8 GBM DNA may not be a part of the genomic DNA. Exosomes possibly acquire this DNA from other sources where it is synthesized by an unknown mechanism. The significance of exosome-bestowed regulatory elements in the transcription of promoter-less retrogene such as NANOGP8 remains to be determined.

Inflammatory response to retrotransposons drives tumor drug resistance that can be prevented by reverse transcriptase inhibitors

Activation of endogenous retrotransposons frequently occurs in cancer cells and contributes to tumor genomic instability. To test whether inhibition of retrotranspositions has an anticancer effect, we used treatment with the nucleoside reverse transcriptase inhibitor (NRTI) stavudine (STV) in mouse cancer models, MMTV-HER2/Neu and Th-MYCN, that spontaneously develop breast cancer and neuroblastoma, respectively. In both cases, STV in drinking water did not affect tumor incidence nor demonstrate direct antitumor effects. However, STV dramatically extended progression-free survival in both models following an initial complete response to chemotherapy. To approach the mechanism underlying this phenomenon, we analyzed the effect of NRTI on the selection of treatment-resistant variants in tumor cells in culture. Cultivation of mouse breast carcinoma 4T1 in the presence of STV dramatically reduced the frequency of cells capable of surviving treatment with anticancer drugs. Global transcriptome analysis demonstrated that the acquisition of drug resistance by 4T1 cells was accompanied by an increase in the constitutive activity of interferon type I and NF-κB pathways and an elevated expression of LINE-1 elements, which are known to induce inflammatory responses via their products of reverse transcription. Treatment with NRTI reduced NF-κB activity and reverted drug resistance. Furthermore, the inducible expression of LINE-1 stimulated inflammatory response and increased the frequency of drug-resistant variants in a tumor cell population. These results indicate a mechanism by which retrotransposon desilencing can stimulate tumor cell survival during treatment and suggest reverse transcriptase inhibition as a potential therapeutic approach for targeting the development of drug-resistant cancers.

Sources of Cancer Neoantigens beyond Single-Nucleotide Variants

The success of checkpoint blockade therapy against cancer has unequivocally shown that cancer cells can be effectively recognized by the immune system and eliminated. However, the identity of the cancer antigens that elicit protective immunity remains to be fully explored. Over the last decade, most of the focus has been on somatic mutations derived from non-synonymous single-nucleotide variants (SNVs) and small insertion/deletion mutations (indels) that accumulate during cancer progression. Mutated peptides can be presented on MHC molecules and give rise to novel antigens or neoantigens, which have been shown to induce potent anti-tumor immune responses. A limitation with SNV-neoantigens is that they are patient-specific and their accurate prediction is critical for the development of effective immunotherapies. In addition, cancer types with low mutation burden may not display sufficient high-quality [SNV/small indels] neoantigens to alone stimulate effective T cell responses. Accumulating evidence suggests the existence of alternative sources of cancer neoantigens, such as gene fusions, alternative splicing variants, post-translational modifications, and transposable elements, which may be attractive novel targets for immunotherapy. In this review, we describe the recent technological advances in the identification of these novel sources of neoantigens, the experimental evidence for their presentation on MHC molecules and their immunogenicity, as well as the current clinical development stage of immunotherapy targeting these neoantigens.

Estrogen distinctly regulates transcription and translation of lncRNAs and pseudogenes in breast cancer cells

Estrogen drives key transcriptional changes in breast cancer and stimulates breast cancer cells' growth with multiple mechanisms to coordinate transcription and translation. In addition to protein-coding transcripts, estrogen can regulate long non-coding RNA (lncRNA) transcripts, plus diverse non-coding RNAs including antisense, enhancer, and intergenic. LncRNA genes comprise the majority of human genes. The accidental, or regulated, translation of their short open reading frames by ribosomes remains a controversial topic. Here we report for the first time an integrated analysis of RNA abundance and ribosome occupancy level, using Ribo-seq combined with RNA-Seq, in the estrogen-responsive, estrogen receptor α positive, human breast cancer cell model MCF7, before and after hormone treatment. Translational profiling can determine, in an unbiased manner, which fraction of the genome is actually translated into proteins, as well as resolving whether transcription and translation respond concurrently, or differentially, to estrogen treatment. Our data showed specific transcripts more robustly detected in RNA-Seq than in the ribosome-profiling data, and vice versa, suggesting distinct gene-specific estrogen responses at the transcriptional and the translational level, respectively. Here, we showed that estrogen stimulation affects the expression levels of numerous lncRNAs, but not their association with ribosomes, and that most lncRNAs are not ribosome-bound. For the first time, we also demonstrated the transcriptional and translational response of expressed pseudogenes to estrogen, pointing to new perspectives for drug-target development in breast cancer in the future.

Noncoding RNAs in Thyroid-Follicular-Cell-Derived Carcinomas

Simple Summary

Thyroid tumors represent the most common neoplastic pathology of the endocrine system. Mutations occurring in oncogenes and tumor suppressor genes are responsible for thyroid carcinogenesis; however, the complete mutational landscape characterizing these neoplasias has not been completely unveiled. It has been established that only the 2% of the human genome codes for proteins, suggesting that the vast majority of the genome has regulatory capabilities, which, if altered, could account for the onset of cancer. Hence, many scientific efforts are currently focused on the characterization of the heterogeneous class of noncoding RNAs, which represent an abundant part of the transcribed noncoding genome. In this review, we mainly focus on the involvement of microRNAs, long noncoding RNAs, and pseudogenes in thyroid cancer. The determination of the diagnosis, prognosis, and treatment of thyroid cancers based on the evaluation of the noncoding RNA network could allow the implementation of a more personalized approach to fighting these pathologies.

Abstract

Among the thyroid neoplasias originating from follicular cells, we can include well-differentiated carcinomas, papillary (PTC) and follicular (FTC) thyroid carcinomas, and the undifferentiated anaplastic (ATC) carcinomas. Several mutations in oncogenes and tumor suppressor genes have already been observed in these malignancies; however, we are still far from the comprehension of their full regulation-altered landscape. Even if only 2% of the human genome has the ability to code for proteins, most of the noncoding genome is transcribed, constituting the heterogeneous class of noncoding RNAs (ncRNAs), whose alterations are associated with the development of several human diseases, including cancer. Hence, many scientific efforts are currently focused on the elucidation of their biological role. In this review, we analyze the scientific literature regarding the involvement of microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and pseudogenes in FTC, PTC, and ATC. Recent findings emphasized the role of lncRNAs in all steps of cancer progression. In particular, lncRNAs may control progression steps by regulating the expression of genes and miRNAs involved in cell proliferation, apoptosis, epithelial–mesenchymal transition, and metastatization. In conclusion, the determination of the diagnosis, prognosis, and treatment of cancer based on the evaluation of the ncRNA network could allow the implementation of a more personalized approach to fighting thyroid tumors.

Identification of Type 2 Diabetes Biomarkers From Mixed Single-Cell Sequencing Data With Feature Selection Methods

Diabetes is the most common disease and a major threat to human health. Type 2 diabetes (T2D) makes up about 90% of all cases. With the development of high-throughput sequencing technologies, more and more fundamental pathogenesis of T2D at genetic and transcriptomic levels has been revealed. The recent single-cell sequencing can further reveal the cellular heterogenicity of complex diseases in an unprecedented way. With the expectation on the molecular essence of T2D across multiple cell types, we investigated the expression profiling of more than 1,600 single cells (949 cells from T2D patients and 651 cells from normal controls) and identified the differential expression profiling and characteristics at the transcriptomics level that can distinguish such two groups of cells at the single-cell level. The expression profile was analyzed by several machine learning algorithms, including Monte Carlo feature selection, support vector machine, and repeated incremental pruning to produce error reduction (RIPPER). On one hand, some T2D-associated genes (MTND4P24, MTND2P28, and LOC100128906) were discovered. On the other hand, we revealed novel potential pathogenic mechanisms in a rule manner. They are induced by newly recognized genes and neglected by traditional bulk sequencing techniques. Particularly, the newly identified T2D genes were shown to follow specific quantitative rules with diabetes prediction potentials, and such rules further indicated several potential functional crosstalks involved in T2D.

Dysregulation of PER3 clock gene and its only pseudogene in colorectal cancer and type 2 diabetes

The period (PER) family genes (PER1, PER2, and PER3) play a fundamental role in regulating the day/night cycle. PER3 has a pseudogene variant, PER3P1 or PER4, whose role and expression pattern is unclear in human health and diseases. This study was performed to evaluate the expression levels of normal PER family members and the PER3P1 pseudogene in colorectal cancer (CRC) and type 2 diabetes (T2D). Blood samples were taken from 50 diabetic patients and analyzed using real-time PCR for quantification of PER3 and PER3P1 expression. Colorectal tumor tissues of 50 individuals were also used to evaluate the expression of PER members. All PER members, including PER3P1, were found to be downregulated in colorectal tumor samples. Blood samples collected from diabetic subjects revealed an opposite expression pattern; both PER3 and its pseudogene were found to be upregulated when compared to the control group. Our results reveal coordination between the expression pattern of PER3P1 and normal PER family genes. Based on our findings and the pathological importance of this pseudogene, it can be suggested that PER3P1 may be one of the key regulators of the molecular clock network and PER family expression. This hypothesis needs to be confirmed by further studies.

The World of Pseudogenes: New Diagnostic and Therapeutic Targets in Cancers or Still Mystery Molecules?

Pseudogenes were once considered as “junk DNA”, due to loss of their functions as a result of the accumulation of mutations, such as frameshift and presence of premature stop-codons and relocation of genes to inactive heterochromatin regions of the genome. Pseudogenes are divided into two large groups, processed and unprocessed, according to their primary structure and origin. Only 10% of all pseudogenes are transcribed into RNAs and participate in the regulation of parental gene expression at both transcriptional and translational levels through senseRNA (sRNA) and antisense RNA (asRNA). In this review, about 150 pseudogenes in the different types of cancers were analyzed. Part of these pseudogenes seem to be useful in molecular diagnostics and can be detected in various types of biological material including tissue as well as biological fluids (liquid biopsy) using different detection methods. The number of pseudogenes, as well as their function in the human genome, is still unknown. However, thanks to the development of various technologies and bioinformatic tools, it was revealed so far that pseudogenes are involved in the development and progression of certain diseases, especially in cancer.

Branca RM, Lehtiö J, Sikanen TM, Cerullo V. PeptiCHIP: A Microfluidic Platform for Tumor Antigen Landscape Identification

Identification of HLA class I ligands from the tumor surface (ligandome or immunopeptidome) is essential for designing T-cell mediated cancer therapeutic approaches. However, the sensitivity of the process for isolating MHC-I restricted tumor-specific peptides has been the major limiting factor for reliable tumor antigen characterization, making clear the need for technical improvement. Here, we describe our work from the fabrication and development of a microfluidic-based chip (PeptiCHIP) and its use to identify and characterize tumor-specific ligands on clinically relevant human samples. Specifically, we assessed the potential of immobilizing a pan-HLA antibody on solid surfaces via well-characterized streptavidin-biotin chemistry, overcoming the limitations of the cross-linking chemistry used to prepare the affinity matrix with the desired antibodies in the immunopeptidomics workflow. Furthermore, to address the restrictions related to the handling and the limited availability of tumor samples, we further developed the concept toward the implementation of a microfluidic through-flow system. Thus, the biotinylated pan-HLA antibody was immobilized on streptavidin-functionalized surfaces, and immune-affinity purification (IP) was carried out on customized microfluidic pillar arrays made of thiol-ene polymer. Compared to the standard methods reported in the field, our methodology reduces the amount of antibody and the time required for peptide isolation. In this work, we carefully examined the specificity and robustness of our customized technology for immunopeptidomics workflows. We tested this platform by immunopurifying HLA-I complexes from 1 × 10⁶ cells both in a widely studied B-cell line and in patients-derived ex vivo cell cultures, instead of 5 × 10⁸ cells as required in the current technology. After the final elution in mild acid, HLA-I-presented peptides were identified by tandem mass spectrometry and further investigated by in vitro methods. These results highlight the potential to exploit microfluidics-based strategies in immunopeptidomics platforms and in personalized immunopeptidome analysis from cells isolated from individual tumor biopsies to design tailored cancer therapeutic vaccines. Moreover, the possibility to integrate multiple identical units on a single chip further improves the throughput and multiplexing of these assays with a view to clinical needs.

Long Non-coding RNA Small Nucleolar RNA Host Gene 14, a Promising Biomarker and Therapeutic Target in Malignancy

Small nucleolar RNA host gene 14 (SNHG14) is a long non-coding RNA found to be overexpressed in various types of cancers. Moreover, the expression level of SNHG14 was closely associated with multiple clinicopathological characteristics such as prognosis, tumor differentiation, TNM stage, and lymph node metastasis. Functionally, gain- and loss-of-function of SNHG14 revealed that overexpressed SNHG14 promoted cancer cell viability, invasion, and migration, whereas its down-regulation produced the opposite effect. Mechanistically, regulating its target gene expression by sponging distinct miRNAs might be the major mechanism underlying the oncogenic functions of SNHG14. Thus, SNHG14 might be a promising prognostic biomarker and therapeutic target for cancers. In this review, we discuss the expression profile, biological function, and molecular mechanisms of SNHG14 in cancers to provide a molecular basis for the clinical utility of SNHG14 in the future.

Pseudogene HSPA7 is a poor prognostic biomarker in Kidney Renal Clear Cell Carcinoma (KIRC) and correlated with immune infiltrates

Background

Pseudogenes played important roles in tumorigenesis, while there are nearly no reports about the expression and roles of HSPA7 in the cancer.

Methods

Firstly, we used Logistic regression, the KS test, the GEPIA database, UALCAN database and qRT-PCR to analyze the expression level of HSPA7 in KIRC, then we used the Cox regression and the Kaplan–Meier curve to analyze the overall survival (OS) of KIRC patients with different Clinico-pathological parameters. Thirdly, we used the multivariate Cox analysis of influencing factors to compare the correlation between the HSPA7 expression level and the clinical parameters. Finally, we used multi-GSEA analysis and the Tumor Immunoassay Resource (TIMER) database to explore the functional role of HSPA7 in KIRC

Results

The HSPA7 is highly expressed in KIRC tumor tissues, and its expression is related to clinico-pathological features and survival in KIRC patients. GSEA analysis displayed the high expression of HSPA7 in KIRC were related to several tumor-related and immune-related pathways. With the TIMER database analysis we showed that HSPA7 levels were correlated with the CD4⁺ T cells, neutrophils and Dendritic Cell.

Conclusions

Our study showed that HSPA7 is very important in the tumor progression and may act as a poor prognostic biomarker for KIRC tumor by modulating immune infiltrating cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02141-1.

Deletion of a pseudogene within a fragile site triggers the oncogenic expression of the mitotic CCSER1 gene

The oncogenic role of common fragile sites (CFS), focal and pervasive gaps in the cancer genome arising from replicative stress, remains controversial. Exploiting the TCGA dataset, we found that in most CFS the genes residing within the associated focal deletions are down-regulated, including proteins involved in tumour immune recognition. In a subset of CFS, however, the residing genes are surprisingly overexpressed. Within the most frequent CFS in this group, FRA4F, which is deleted in up to 18% of cancer cases and harbours the CCSER1 gene, we identified a region which includes an intronic, antisense pseudogene, TMSB4XP8. TMSB4XP8 focal ablation or transcriptional silencing elicits the overexpression of CCSER1, through a cis-acting mechanism. CCSER1 overexpression increases proliferation and triggers centrosome amplifications, multinuclearity, and aberrant mitoses. Accordingly, FRA4F is associated in patient samples to mitotic genes deregulation and genomic instability. As a result, cells overexpressing CCSER1 become sensitive to the treatment with aurora kinase inhibitors. Our findings point to a novel tumourigenic mechanism where focal deletions increase the expression of a new class of "dormant" oncogenes.

Prognostic Nomogram of Prognosis-Related Genes and Clinicopathological Characteristics to Predict the 5-Year Survival Rate of Colon Cancer Patients

Background: The Cancer Genome Atlas (TCGA) has established a genome-wide gene expression profile, increasing our understanding of the impact of tumor heredity on clinical outcomes. The aim of this study was to construct a nomogram using data from the TCGA regarding prognosis-related genes and clinicopathological characteristics to predict the 5-years survival rate of colon cancer (CC) patients. Methods: Kaplan-Meier and Cox regression analyses were used to identify genes associated with the 5-years survival rate of CC patients. Cox regression was used to analyze the relationship between the clinicopathological features and prognostic genes and overall survival rates in patients with CC and to identify independent risk factors for the prognosis of CC patients. A nomogram for predicting the 5-years survival rate of CC patients was constructed by R software. Results: A total of eight genes (KCNJ14, CILP2, ATP6V1G2, GABRD, RIMKLB, SIX2, PLEKHA8P1, and MPP2) related to the 5-years survival of rate CC patients were identified. Age, stage, and PLEKHA8P1 were independent risk factors for the 5-years survival rate in patients with CC. The accuracy, sensitivity and specificity of the nomogram model constructed by age, TNM staging, and PLEKHA8P1 for predicting the 5-years survival of rate CC patients were 83.3, 83.97, and 85.79%, respectively. Conclusion: The nomogram can correctly predict the 5-year survival rate of patients with CC, thus aiding the individualized decision-making process for patients with CC.

Pseudogene ANXA2P2 knockdown shows tumor-suppressive function by inhibition of the PI3K/PKB pathway in glioblastoma cells

The pseudogene annexin A2 pseudogene 2 (ANXA2P2) is highly expressed in glioblastoma (GBM). However, its role and mechanism involved in the progression of GBM remain poorly understood. ANXA2P2 messenger RNA expression was measured by quantitative reverse transcription-polymerase chain reaction. The protein levels were detected by Western blot. Cell viability was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase (LDH) release assays. Cell invasive ability was investigated by the transwell assay and by epithelial-mesenchymal transition (EMT). Cell apoptosis was examined by flow cytometry. The results showed that ANXA2P2 expression was increased in GBM tissues and cells. Silencing of ANXA2P2 inhibited the activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB) pathway in GBM cells. Knockdown of ANXA2P2 decreased cell viability, promoted LDH release, suppressed cell invasive ability, and EMT, and induced cell apoptosis in GBM cells. The addition of the PI3K/PKB activator 740Y-P abrogated the effects of ANXA2P2 knockdown on cell viability, LDH release, invasive ability, and apoptosis. In conclusion, knockdown of ANXA2P2 inhibited cell viability and invasion but promoted the apoptotic rate by suppressing the PI3K/PKB pathway in GBM cells. ANXA2P2 may represent a new target for the treatment of GBM.

Increased expression of peptides from non-coding genes in cancer proteomics datasets suggests potential tumor neoantigens

Neoantigen-based immunotherapy has yielded promising results in clinical trials. However, it is limited to tumor-specific mutations, and is often tailored to individual patients. Identifying suitable tumor-specific antigens is still a major challenge. Previous proteogenomics studies have identified peptides encoded by predicted non-coding sequences in human genome. To investigate whether tumors express specific peptides encoded by non-coding genes, we analyzed published proteomics data from five cancer types including 933 tumor samples and 275 matched normal samples and compared these to data from 31 different healthy human tissues. Our results reveal that many predicted non-coding genes such as DGCR9 and RHOXF1P3 encode peptides that are overexpressed in tumors compared to normal controls. Furthermore, from the non-coding genes-encoded peptides specifically detected in cancers, we predict a large number of “dark antigens” (neoantigens from non-coding genomic regions), which may provide an alternative source of neoantigens beyond standard tumor specific mutations.

Rong Xiang et al. analyze the expression of non-coding genes encoded peptides in publicly-available proteomics data from five cancer types and matched controls. They identify peptides from non-coding genes including DGCR9 and RHOXF1P3 that are upregulated in tumors compared to controls, suggesting that non-coding gene-encoded peptides may be a source of neoantigens in some cancers.

Circulating Biomarkers for Early Stage Non-Small Cell Lung Carcinoma Detection: Supplementation to Low-Dose Computed Tomography

Lung cancer is currently the leading cause of cancer death in both developing and developed countries. Given that lung cancer has poor prognosis in later stages, it is essential to achieve an early diagnosis to maximize patients’ overall survival. Non-small cell lung cancer (NSCLC) is the most common form of primary lung cancer in both smokers and non-smokers. The current standard screening method, low‐dose computed tomography (LDCT), is the only radiological method that demonstrates to have mortality benefits across multiple large randomized clinical trials (RCT). However, these RCTs also found LDCT to have a significant false positive rate that results in unnecessary invasive biopsies being performed. Due to the lack of both sensitive and specific screening methods for the early detection of lung cancer, there is an urgent need for alternative minimally or non-invasive biomarkers that may provide diagnostic, and/or prognostic information. This has led to the identification of circulating biomarkers that can be readily detectable in blood and have been extensively studied as prognosis markers. Circulating microRNA (miRNA) in particular has been investigated for these purposes as an augmentation to LDCT, or as direct diagnosis of lung cancer. There is, however, a lack of consensus across the studies on which miRNAs are the most clinically useful. Besides miRNA, other potential circulating biomarkers include circulating tumor cells (CTCs), circulating tumor DNA (ctDNAs) and non-coding RNAs (ncRNAs). In this review, we provide the current outlook of several of these biomarkers for the early diagnosis of NSCLC.

Higher Rates of Processed Pseudogene Acquisition in Humans and Three Great Apes Revealed by Long-Read Assemblies

LINE-1-mediated retrotransposition of protein-coding mRNAs is an active process in modern humans for both germline and somatic genomes. Prior works that surveyed human data mostly relied on detecting discordant mappings of paired-end short reads, or exon junctions contained in short reads. Moreover, there have been few genome-wide comparisons between gene retrocopies in great apes and humans. In this study, we introduced a more sensitive and accurate method to identify processed pseudogenes. Our method utilizes long-read assemblies, and more importantly, is able to provide full-length retrocopy sequences as well as flanking regions which are missed by short-read based methods. From 22 human individuals, we pinpointed 40 processed pseudogenes that are not present in the human reference genome GRCh38 and identified 17 pseudogenes that are in GRCh38 but absent from some input individuals. This represents a significantly higher discovery rate than previous reports (39 pseudogenes not in the reference genome out of 939 individuals). We also provided an overview of lineage-specific retrocopies in chimpanzee, gorilla, and orangutan genomes.

Prenatal detection of a 7q11.21 microdeletion (517-605 kb): A variant with normal characteristics at birth (STROBE)

In the literature, 7q11 deletion was reported with various abnormalities. However, there were other genetic conditions combined with 7q11.21. It is necessary to have sufficient pure 7q11.21 microdeletions for classifying the pathogenic categories of variation.Chromosomal karyotyping analysis was performed on cultured amniotic fluid cells. Eighteen pregnant women took chromosomal microarray using prenatal amniotic fluid samples at our center by Affymetrix CytoScan750K_Array. We followed the outcome of these pregnancies and determined postnatal health conditions.Cytogenetic studies delineated that all patients had normal karyotypes. The exception was P17, who had 47, XN. Single nucleotide polymorphism array results showed 517 to 605 kb deletions of 7q11.21 (chr7: 64543313-65196780) in these cases. The microarray results were pure or combined 7q11.21 microdeletions. In 11 pure 7q11.21 microdeletions and 7 combined cases, there was no apparent abnormal phenotype associated with partial 7q11.21. Among them, only mothers of P10 and P17 decided to terminate the pregnancies due to 18 trisomy or ultrasound abnormal fetal strephenopodia. In the follow-up survey, the newborns had no apparent abnormalities.In this study, we described 11 pure and 7 combined 7q11.21 microdeletions associating with no apparent postnatal phenotypic abnormalities. From this study, we can learn that the partial 7q11.21 deletion (chr7: 64543313-65196780) might be benign and have no association with human disorders.

Cancer, Retrogenes, and Evolution

This review summarizes the knowledge about retrogenes in the context of cancer and evolution. The retroposition, in which the processed mRNA from parental genes undergoes reverse transcription and the resulting cDNA is integrated back into the genome, results in additional copies of existing genes. Despite the initial misconception, retroposition-derived copies can become functional, and due to their role in the molecular evolution of genomes, they have been named the “seeds of evolution”. It is convincing that retrogenes, as important elements involved in the evolution of species, also take part in the evolution of neoplastic tumors at the cell and species levels. The occurrence of specific “resistance mechanisms” to neoplastic transformation in some species has been noted. This phenomenon has been related to additional gene copies, including retrogenes. In addition, the role of retrogenes in the evolution of tumors has been described. Retrogene expression correlates with the occurrence of specific cancer subtypes, their stages, and their response to therapy. Phylogenetic insights into retrogenes show that most cancer-related retrocopies arose in the lineage of primates, and the number of identified cancer-related retrogenes demonstrates that these duplicates are quite important players in human carcinogenesis.

Overexpression of FAM234B Predicts Poor Prognosis in Patients with Luminal Breast Cancer

Background

Family with sequence similarity 234 member B (FAM234B), a protein-coding gene, is mainly expressed in brain tissues. Its clinical significance and biological function in tumors, especially in breast cancer (BC), have not been elucidated.

Methods

We firstly investigated the expression pattern of FAM234B at the mRNA and protein levels using Oncomine, TCGA portal, GEPIA, TIMER, HPA, and UALCAN databases, then applied bc-GenExMiner to assess the associations between expression level of FAM234B and clinicopathological features of BC. Besides, we also verified the expression of FAM234B expression in clinical BC samples using qRT-PCR. Subsequently, GEPIA, bc-GenExMiner, and TIMER databases were used to analyze the prognostic significance of FAM234B in all BC and different molecular subtypes. Finally, we conducted co-expression analysis and gene set enrichment analysis (GSEA). Additionally, we explored the regulatory mechanism of FAM234B in BC.

Results

Both bioinformatics analysis and experimental verification confirmed that the FAM234B expression was significantly higher at the mRNA and protein levels in luminal BC tissues than in adjacent normal tissues. High FAM234B expression was significantly correlated with older age, estrogen receptor-positive, progesterone receptor-positive, human epidermal growth factor receptor 2-negative, wild-type p53, low Nottingham prognostic index, low Scarff-Bloom-Richardson grade, lymph node metastasis positivity, and high tumor stage. Moreover, survival analysis indicated that high FAM234B expression was significantly related to a worse prognosis in patients with luminal BC. GSEA indicated that FAM234B was positively related to membrane transport process and negatively associated with immune response function. Besides, mechanism exploration indicated that pseudogene HTR7P1 might act as endogenous RNA to compete with has-miR-1271-5p or has-miR-381-3p for binding to FAM234B, thereby upregulating the expression of FAM234B in luminal BC.

Conclusion

Our results suggest that FAM234B may be a candidate therapeutic target or prognostic marker for luminal breast cancer.

Overexpressed Pseudogene HLA-DPB2 Promotes Tumor Immune Infiltrates by Regulating HLA-DPB1 and Indicates a Better Prognosis in Breast Cancer

Immune checkpoint inhibitors (ICIs) have been successfully used for treating melanoma and non-small cell lung cancer. However, many patients with breast cancer (BC) show low response to ICIs due to the paucity of infiltrating immune cells. Pseudogenes, as a particular kind of long-chain noncoding RNA, play vital roles in tumorigenesis, but their potential roles in tumor immunology remain unclear. In this study that used data from online databases, the novel pseudogene HLA-DPB2 and its parental gene HLA-DPB1 were overexpressed and correlated with better prognosis in BC. Mechanistically, our results revealed that HLA-DPB2 might serve as an endogenous RNA to increase HLA-DPB1 expression by competitively binding with has-miR-370-3p. Functionally, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that the HLA-DPB2/HLA-DPB1 axis was strongly relevant to immune-related biological functions. Further analysis demonstrated that high expression levels of the HLA-DPB2 and HLA-DPB1 were significantly associated with high immune infiltration abundance of CD8+ T cells, CD4+ T cells, Tfh, Th1, and NK cells and with high expression of majority biomarkers of monocytes, NK cell, T cell, CD8+ T cell, and Th1 in BC and its subtype, indicating that HLA-DPB2 can increase the abundance of tumor-infiltrating lymphocytes in the BC microenvironment. Also, the HLA-DPB2 and HLA-DPB1 expression levels positively correlated with the expression levels of programmed cell death protein 1, programmed cell death ligand 1, and cytotoxic T-lymphocyte-associated antigen-4. Our findings suggest that pseudogene HLA-DPB2 can upregulate HLA-DPB1 through sponging has-miR-370-3p, thus exerting its antitumor effect by recruiting tumor-infiltrating immune cells into the breast tumor microenvironment, and that targeting the HLA-DPB2/HLA-DPB1 axis with ICIs may optimize the current immunotherapy for BC.

Comprehensive analysis of LDHAP5 pseudogene expression and potential pathogenesis in ovarian serous cystadenocarcinoma

Background

We aimed to identify differentially expressed pseudogenes and explore their potential functions in four types of common gynecological malignancies (e.g., cervical squamous cell carcinoma, ovarian serous cystadenocarcinoma, uterine corpus endometrial carcinoma, and uterine carcinosarcoma) using bioinformatics technology.

Materials and methods

We identified up-regulated and down-regulated pseudogenes and built a pseudogene-miRNA-mRNA regulatory network through public datasets to explore their potential functions in carcinogenesis and cancer prognosis.

Results

Among the 63 up-regulated pseudogenes identified, LDHAP5 demonstrated the greatest potential as a candidate pseudogene due to its significant association with poor overall survival in ovarian serous cystadenocarcinoma. KEGG pathway analysis revealed that LDHAP5 showed significant enrichment in MicroRNAs in cancer, Pathway in cancer and PI3K-AKT signaling pathway. Further analysis revealed that EGFR was the potential target mRNA of LDHAP5, which may play an important role in ovarian serous cystadenocarcinoma.

Conclusions

LDHAP5 was associated with the occurrence and prognosis of ovarian serous cystadenocarcinoma, and thus shows potential as a novel therapeutic target against such cancer.

Complex Analysis of Retroposed Genes' Contribution to Human Genome, Proteome and Transcriptome

Gene duplication is a major driver of organismal evolution. One of the main mechanisms of gene duplications is retroposition, a process in which mRNA is first transcribed into DNA and then reintegrated into the genome. Most gene retrocopies are depleted of the regulatory regions. Nevertheless, examples of functional retrogenes are rapidly increasing. These functions come from the gain of new spatio-temporal expression patterns, imposed by the content of the genomic sequence surrounding inserted cDNA and/or by selectively advantageous mutations, which may lead to the switch from protein coding to regulatory RNA. As recent studies have shown, these genes may lead to new protein domain formation through fusion with other genes, new regulatory RNAs or other regulatory elements. We utilized existing data from high-throughput technologies to create a complex description of retrogenes functionality. Our analysis led to the identification of human retroposed genes that substantially contributed to transcriptome and proteome. These retrocopies demonstrated the potential to encode proteins or short peptides, act as cis- and trans- Natural Antisense Transcripts (NATs), regulate their progenitors’ expression by competing for the same microRNAs, and provide a sequence to lncRNA and novel exons to existing protein-coding genes. Our study also revealed that retrocopies, similarly to retrotransposons, may act as recombination hot spots. To our best knowledge this is the first complex analysis of these functions of retrocopies.

Role of PA2G4P4 pseudogene in bladder cancer tumorigenesis

BACKGROUND

Many pseudogenes possess biological activities and play important roles in the pathogenesis of various types of cancer including bladder cancer (BlCa), which still lacks suitable molecular biomarkers. Recently, pseudogenes were found to be significantly enriched in a pan-cancer classification based on the Cancer Genome Atlas gene expression data. Among them, the top-ranking pseudogene was the proliferation-associated 2G4 pseudogene 4 (PA2G4P4).

METHODS

Genomic and transcript features of PA2G4P4 were determined by GeneBank database analysis followed by 5' RACE experiments. Therefore, we conducted a retrospective molecular study on a cohort of 45 patients of BlCa. PA2G4P4 expression was measured by RT-qPCR, whereas PA2G4P4 transcript distribution was analyzed by in situ hybridization on both normal and cancerous histological sections and compared to the immunolocalization of its parental PA2G4/EBP1 protein. Finally, we tested the effects of PA2G4P4 depletion on proliferation, migration, and death of BlCa cells.

RESULTS

We showed for the first time PA2G4P4 overexpression in BlCa tissues and in cell lines. PA2G4P4 distribution strictly overlaps PA2G4/EBP1 protein localization. Moreover, we showed that PA2G4P4 knockdown affects both proliferation and migration of BlCa cells, highlighting its potential oncogenic role.

CONCLUSIONS

PA2G4P4 may play a functional role as an oncogene in BlCa development, suggesting it as a good candidate for future investigation and new clinical applications.

Integrative analyses of noncoding RNAs reveal the potential mechanisms augmenting tumor malignancy in lung adenocarcinoma

Precise noncoding RNA (ncRNA)-based network prediction is necessary to reveal ncRNA functions and pathological mechanisms. Here, we established a systemic pipeline to identify prognostic ncRNAs, predict their functions and explore their pathological mechanisms in lung adenocarcinoma (LUAD). After in silico and experimental validation based on evaluations of prognostic value in multiple LUAD cohorts, we selected the PTTG3P pseudogene from among other prognostic ncRNAs (MIR497HG, HSP078, TBX5-AS1, LOC100506990 and C14orf64) for mechanistic studies. PTTG3P upregulation in LUAD cells shortens the metaphase to anaphase transition in mitosis, increases cell viability after cisplatin or paclitaxel treatment, facilitates tumor growth that leads to poor survival in orthotopic lung models, and is associated with a poor survival rate in LUAD patients in the TCGA cohort who received chemotherapy. Mechanistically, PTTG3P acts as an ncRNA that interacts with the transcription factor FOXM1 to regulate the transcriptional activation of the mitotic checkpoint kinase BUB1B, which augments tumor growth and chemoresistance and leads to poor outcomes for LUAD patients. Overall, we established a systematic strategy to uncover prognostic ncRNAs with functional prediction methods suitable for pan-cancer studies. Moreover, we revealed that PTTG3P, due to its upregulation of the PTTG3P/FOXM1/BUB1B axis, could be a therapeutic target for LUAD patients.

Deep Sequencing Analysis Reveals Distinctive Non-Coding RNAs When Comparing Tumor Multidrug-Resistant Cells and Extracellular Vesicles with Drug-Sensitive Counterparts

Multidrug resistance (MDR) is one of the main limitations of cancer treatment. The overexpression of drug-efflux pumps, such as P-glycoprotein (P-gp), is a major cause of MDR. Importantly, different studies have shown that extracellular vesicles (EVs) participate in the communication between MDR cells and drug-sensitive counterparts, promoting dissemination of the MDR phenotype. In the present work, we aimed to identify RNA species present in MDR cells and in EVs released by those cells, which may be associated with the MDR phenotype. The RNA content from two pairs (leukemia and lung cancer) of MDR (P-gp overexpressing) cells and their drug-sensitive counterparts, as well as from their EVs, was analyzed by deep sequencing. Our results showed distinctive transcripts for MDR cells and their EVs, when compared with their drug-sensitive counterparts. Remarkably, two pseudogenes (a novel pseudogene and RNA 5.8S ribosomal pseudogene 2) were found to be increased in EVs released by MDR cells in both leukemia and lung cancer models. Moreover, six miRs (miR-204-5p, miR-139-5p, miR-29c-5p, miR-551b-3p, miR-29b-2-5p, and miR-204-3p) exhibited altered levels in lung cancer MDR cells and their EVs. This study provides insights into the contribution of EVs to MDR.

World Workshop on Oral Medicine VII: Functional pathways involving differentially expressed lncRNAs in oral squamous cell carcinoma

Long non-coding RNAs (lncRNA) modulate gene expression at the epigenetic, transcriptional and post-transcriptional levels and are involved in tumorigenesis. They can form complex secondary and tertiary structures and have been shown to act as precursors, enhancers, reservoirs and decoys in the complex endogenous RNA network. They were first reported in relation to oral squamous cell carcinoma (OSCC) in 2013. Here, we summarise the functional roles and pathways of the most commonly studied lncRNAs in OSCC. Existing research demonstrates the involvement of lncRNA within pivotal pathways leading to the development and spread of OSCC, including interactions with key cancer-associated microRNAs such as miR-21. The number of studies on lncRNA and OSCC remains limited in this new field. As evidence grows, the tissue-specific expression patterns of lncRNAs should further advance our understanding of the altered regulatory networks in OSCC and possibly reveal new biomarkers and therapeutic targets.

Re-recognition of pseudogenes: From molecular to clinical applications

Pseudogenes were initially regarded as "nonfunctional" genomic elements that did not have protein-coding abilities due to several endogenous inactivating mutations. Although pseudogenes are widely expressed in prokaryotes and eukaryotes, for decades, they have been largely ignored and classified as gene "junk" or "relics". With the widespread availability of high-throughput sequencing analysis, especially omics technologies, knowledge concerning pseudogenes has substantially increased. Pseudogenes are evolutionarily conserved and derive primarily from a mutation or retrotransposon, conferring the pseudogene with a "gene repository" role to store and expand genetic information. In contrast to previous notions, pseudogenes have a variety of functions at the DNA, RNA and protein levels for broadly participating in gene regulation to influence the development and progression of certain diseases, especially cancer. Indeed, some pseudogenes have been proven to encode proteins, strongly contradicting their "trash" identification, and have been confirmed to have tissue-specific and disease subtype-specific expression, indicating their own value in disease diagnosis. Moreover, pseudogenes have been correlated with the life expectancy of patients and exhibit great potential for future use in disease treatment, suggesting that they are promising biomarkers and therapeutic targets for clinical applications. In this review, we summarize the natural properties, functions, disease involvement and clinical value of pseudogenes. Although our knowledge of pseudogenes remains nascent, this field deserves more attention and deeper exploration.

PseudoFuN: Deriving functional potentials of pseudogenes from integrative relationships with genes and microRNAs across 32 cancers

Background

Long thought “relics” of evolution, not until recently have pseudogenes been of medical interest regarding regulation in cancer. Often, these regulatory roles are a direct by-product of their close sequence homology to protein-coding genes. Novel pseudogene-gene (PGG) functional associations can be identified through the integration of biomedical data, such as sequence homology, functional pathways, gene expression, pseudogene expression, and microRNA expression. However, not all of the information has been integrated, and almost all previous pseudogene studies relied on 1:1 pseudogene–parent gene relationships without leveraging other homologous genes/pseudogenes.

Results

We produce PGG families that expand beyond the current 1:1 paradigm. First, we construct expansive PGG databases by (i) CUDAlign graphics processing unit (GPU) accelerated local alignment of all pseudogenes to gene families (totaling 1.6 billion individual local alignments and >40,000 GPU hours) and (ii) BLAST-based assignment of pseudogenes to gene families. Second, we create an open-source web application (PseudoFuN [Pseudogene Functional Networks]) to search for integrative functional relationships of sequence homology, microRNA expression, gene expression, pseudogene expression, and gene ontology. We produce four “flavors” of CUDAlign-based databases (>462,000,000 PGG pairwise alignments and 133,770 PGG families) that can be queried and downloaded using PseudoFuN. These databases are consistent with previous 1:1 PGG annotation and also are much more powerful including millions of de novo PGG associations. For example, we find multiple known (e.g., miR-20a-PTEN-PTENP1) and novel (e.g., miR-375-SOX15-PPP4R1L) microRNA-gene-pseudogene associations in prostate cancer. PseudoFuN provides a “one stop shop” for identifying and visualizing thousands of potential regulatory relationships related to pseudogenes in The Cancer Genome Atlas cancers.

Conclusions

Thousands of new PGG associations can be explored in the context of microRNA-gene-pseudogene co-expression and differential expression with a simple-to-use online tool by bioinformaticians and oncologists alike.

Paclitaxel Response Can Be Predicted With Interpretable Multi-Variate Classifiers Exploiting DNA-Methylation and miRNA Data

To address the problem of resistance to paclitaxel treatment, we have investigated to which extent is possible to predict Breast Cancer (BC) patient response to this drug. We carried out a large-scale tumor-based prediction analysis using data from the US National Cancer Institute’s Genomic Data Commons. These data sets comprise the responses of BC patients to paclitaxel along with six molecular profiles of their tumors. We assessed 10 Machine Learning (ML) algorithms on each of these profiles and evaluated the resulting 60 classifiers on the same BC patients. DNA methylation and miRNA profiles were the most informative overall. In combination with these two profiles, ML algorithms selecting the smallest subset of molecular features generated the most predictive classifiers: a complexity-optimized XGBoost classifier based on CpG island methylation extracted a subset of molecular factors relevant to predict paclitaxel response (AUC = 0.74). A CpG site methylation-based Decision Tree (DT) combining only 2 of the 22,941 considered CpG sites (AUC = 0.89) and a miRNA expression-based DT employing just 4 of the 337 analyzed mature miRNAs (AUC = 0.72) reveal the molecular types associated to paclitaxel-sensitive and resistant BC tumors. A literature review shows that features selected by these three classifiers have been individually linked to the cytotoxic-drug sensitivities and prognosis of BC patients. Our work leads to several molecular signatures, unearthed from methylome and miRNome, able to anticipate to some extent which BC tumors respond or not to paclitaxel. These results may provide insights to optimize paclitaxel-therapies in clinical practice.

dreamBase: DNA modification, RNA regulation and protein binding of expressed pseudogenes in human health and disease

Although thousands of pseudogenes have been annotated in the human genome, their transcriptional regulation, expression profiles and functional mechanisms are largely unknown. In this study, we developed dreamBase (http://rna.sysu.edu.cn/dreamBase) to facilitate the investigation of DNA modification, RNA regulation and protein binding of potential expressed pseudogenes from multidimensional high-throughput sequencing data. Based on ∼5500 ChIP-seq and DNase-seq datasets, we identified genome-wide binding profiles of various transcription-associated factors around pseudogene loci. By integrating ∼18 000 RNA-seq data, we analysed the expression profiles of pseudogenes and explored their co-expression patterns with their parent genes in 32 cancers and 31 normal tissues. By combining microRNA binding sites, we demonstrated complex post-transcriptional regulation networks involving 275 microRNAs and 1201 pseudogenes. We generated ceRNA networks to illustrate the crosstalk between pseudogenes and their parent genes through competitive binding of microRNAs. In addition, we studied transcriptome-wide interactions between RNA binding proteins (RBPs) and pseudogenes based on 458 CLIP-seq datasets. In conjunction with epitranscriptome sequencing data, we also mapped 1039 RNA modification sites onto 635 pseudogenes. This database will provide insights into the transcriptional regulation, expression, functions and mechanisms of pseudogenes as well as their roles in biological processes and diseases.

LncRNA PCNAP1 modulates hepatitis B virus replication and enhances tumor growth of liver cancer

Rationale: Hepatitis B virus (HBV) is a major risk factor for liver cancer, in which HBV covalently closed circular DNA (cccDNA) plays crucial roles. However, the effect of pseudogene-derived long noncoding RNAs (lncRNAs) acting as functional regulators of their ancestral gene expression on HBV replication and hepatocellular carcinoma (HCC) remains unclear. In this study, we speculated that the pseudogene-derived lncRNA PCNAP1 and its ancestor PCNA might modulate HBV replication and promote hepatocarcinogenesis.

Methods: We investigated the roles of lncRNA PCNAP1 in contribution of HBV replication through modulating miR-154/PCNA/HBV cccDNA signaling in hepatocarcinogenesis by using CRISPR/Cas9, Southern blot analysis, confocal assays, et al. in primary human hepatocytes (PHH), HepaRG cells, HepG2-NTCP cells, hepatoma carcinoma cells, human liver-chimeric mice model, transgenetic mice model, in vitro tumorigenicity and clinical patients.

Results: Interestingly, the expression levels of PCNAP1 and PCNA were significantly elevated in the liver of HBV-infectious human liver-chimeric mice. Clinically, the mRNA levels of PCNAP1 and PCNA were increased in the liver of HBV-positive/HBV cccDNA-positive HCC patients. Mechanistically, PCNA interacted with HBV cccDNA in a HBc-dependent manner. PCNAP1 enhanced PCNA through sponging miR-154 targeting PCNA mRNA 3′UTR. Functionally, PCNAP1 or PCNA remarkably enhanced HBV replication and accelerated the growth of HCC in vitro and in vivo.

Conclusion: We conclude that lncRNA PCNAP1 enhances the HBV replication through modulating miR-154/PCNA/HBV cccDNA signaling and the PCNAP1/PCNA signaling drives the hepatocarcinogenesis. Our finding provides new insights into the mechanism by which lncRNA PCNAP1 enhances HBV replication and hepatocarcinogenesis.

A benchmark study of scoring methods for non-coding mutations

Motivation

Detailed knowledge of coding sequences has led to different candidate models for pathogenic variant prioritization. Several deleteriousness scores have been proposed for the non-coding part of the genome, but no large-scale comparison has been realized to date to assess their performance.

Results

We compared the leading scoring tools (CADD, FATHMM-MKL, Funseq2 and GWAVA) and some recent competitors (DANN, SNP and SOM scores) for their ability to discriminate assumed pathogenic variants from assumed benign variants (using the ClinVar, COSMIC and 1000 genomes project databases). Using the ClinVar benchmark, CADD was the best tool for detecting the pathogenic variants that are mainly located in protein coding gene regions. Using the COSMIC benchmark, FATHMM-MKL, GWAVA and SOMliver outperformed the other tools for pathogenic variants that are typically located in lincRNAs, pseudogenes and other parts of the non-coding genome. However, all tools had low precision, which could potentially be improved by future non-coding genome feature discoveries. These results may have been influenced by the presence of potential benign variants in the COSMIC database. The development of a gold standard as consistent as ClinVar for these regions will be necessary to confirm our tool ranking.

Availability and implementation

The Snakemake, C++ and R codes are freely available from https://github.com/Oncostat/BenchmarkNCVTools and supported on Linux.

Contact

damien.drubay@gustaveroussy.fr or stefan.michiels@gustaveroussy.fr.

Supplementary information

Supplementary data are available at Bioinformatics online.

Deregulation of H19 is associated with cervical carcinoma

CACX is one of the most common cancer affecting women world-wide. Here, expression microarray analysis revealed 8 over-expressed transcribed pseudogenes (GBP1P1, HLA-DRB6, HLA-H, SLC6A10P, NAPSB, KRT16P2, PTTG3P and RNF126P1), down-regulated 7 lincRNAs (H19, MIR100HG, MEG3, DIO3OS, HOXA11-AS, CD27-AS1 and EPB41L4A-AS) and 6 snoRNAs (SNORD97, SNORD3A, SNORD3C, SNORD3D, SNORA12 and SCARNA9) as DEncGs (log2 fold-change ≥ ±1.0) in CACX. Consequently, down-regulation of lincRNA MEG3 and over-expression of pseudogenes, GBP1P1 and PTTG3P in the microarray analysis were found concordant with the real-time quantitative PCR results upon validation. Then, Ingenuity® Pathway analysis (IPA®) analysis with deregulated DEncGs identified functionally important gene, H19. Further, validation (n = 52) of expression confirmed frequent downregulation of H19 with significant association with its deletion (LOH) and promoter methylation (n = 128) in CACX. Moreover, clinicopathological analysis found Indian CACX patients (n = 26) with alterations of H19 by deletion or, promoter methylation with concomitant low expression have poor prognosis.

Pseudogene CHIAP2 inhibits proliferation and invasion of lung adenocarcinoma cells by means of the WNT pathway

Recently, pseudogenes have emerged as critical regulators in the onset of human neoplasia. Here, we present a comprehensive analysis of pseudogene alterations at transcriptional levels in lung adenocarcinoma (LUAD) from The Cancer Genome Atlas. By combinations of differential expression analysis, survival analysis, and univariate and multivariable Cox proportional hazards regression models, we identified four dysregulated pseudogenes, whose expression level was closely related to LUAD patients' prognosis and the four pseudogene signature could act as an independent prognostic indicator for LUAD patients. We further characterized CHIAP2, one of those four pseudogenes, whose expression level was the most closely linked to LUAD patients' prognosis. Consistent with our analysis, the expression of CHIAP2 was abnormally downregulated in LUAD tissues compared with that in normal tissues in our 50 pairs of clinical samples. Functional assays demonstrated that upregulation of CHIAP2 significantly impaired cell proliferation and invasion. After performing RNA sequencing (RNA-seq) and small RNA-seq between CHIAP2 overexpression and negative control LUAD cell lines, we identified differentially expressed messenger RNAs and microRNAs (miRNAs), among which six miRNAs were downregulated. Target genes of six downregulated miRNAs were predicted with online miRNA target prediction tools and significant pathways including the WNT signal pathway were identified with Gene Set Enrichment Analysis. By combining predictor genes of six downregulated miRNAs and dysregulated genes of the WNT pathway, we inferred that overexpression of CHAP2 may inhibit LUAD cell proliferation and invasion via modulation of NFATC2 or GSK3B (WNT signal pathway) targeted by miR-3614-5p or miR-873-3p.

DUXAP8, a pseudogene derived lncRNA, promotes growth of pancreatic carcinoma cells by epigenetically silencing CDKN1A and KLF2

BACKGROUND

Recent studies highlight pseudogene derived long non-coding RNAs (lncRNAs) as key regulators of cancer biology. However, few of them have been well characterized in pancreatic cancer. Here, we aimed to identify the association between pseudogene derived lncRNA DUXAP8 and growth of pancreatic cancer cells.

METHODS

We screened for pseudogene derived lncRNAs associated with human pancreatic cancer by comparative analysis of three independent datasets from GEO. Quantitative real-time reverse transcription polymerase chain reaction was used to assess the relative expression of DUXAP8 in pancreatic cancer tissues and cells. Loss-of-function approaches were used to investigate the potential functional roles of DUXAP8 in pancreatic cancer cell proliferation and apoptosis in vitro and in vivo. RNA immunoprecipitation, chromosome immunoprecipitation assay and rescue experiments were performed to analyze the association of DUXAP8 with target proteins and genes in pancreatic cancer cells.

RESULTS

Pancreatic cancer tissues had significantly higher DUXAP8 levels than paired adjacent normal tissues. High DUXAP8 expression was associated with a larger tumor size, advanced pathological stage and shorter overall survival of pancreatic cancer patients. Moreover, silencing DUXAP8 expression by siRNA or shRNA inhibited pancreatic cancer cell proliferation and promoted apoptosis in vitro and in vivo. Mechanistic analyses indicated that DUXAP8 regulates PC cell proliferation partly through downregulation of tumor suppressor CDKN1A and KLF2 expression.

CONCLUSION

Our results suggest that tumor expression of pseudogene derived lncRNA DUXAP8 plays an important role in pancreatic cancer progression. DUXAP8 may serve as a candidate biomarker and represent a novel therapeutic target of pancreatic cancer.

New insights into long noncoding RNAs and pseudogenes in prognosis of renal cell carcinoma

Background

Increasing evidence suggests a critical role for long noncoding RNAs (LncRNAs) and pseudogenes in cancer. Renal cell carcinoma (RCC), the most common primary renal neoplasm, is highly aggressive and difficult to treat because of its resistance to chemotherapy and radiotherapy. Despite many identified LncRNAs and pseudogenes, few have been clearly elucidated.

Methods

This study provides new insights into LncRNAs and pseudogenes in the prognosis of RCC. We searched an online database to interrogate alterations and clinical data on cBioPortal. We analysed LncRNA and pseudogene signatures to predict the prognosis of RCC based on a Cox model. We also found potential serum biomarkers of RCC and validated them in 32 RCC patients, as well as healthy controls.

Results

Alterations were found in 2553 LncRNAs and 8901 pseudogenes and occurred in up to 23% of all cases. Among these, 27 LncRNAs and 45 pseudogenes were closely related to prognosis. We also identified signatures of LncRNAs and pseudogenes that can predict overall survival and recurrence of RCC. We then validated the relative levels of these LncRNAs and pseudogenes in the serum of 32 patients. Six of these, including LINC00520, PIK3CD-AS1, LINC01559, CEACAM22P, MSL3P1 and TREML3P, could be non-invasive biomarkers of RCC. Finally, we selected PIK3CD-AS1 to determine its role in RCC and found that upregulation of PIK3CD-AS1 was closely associated with higher tumour stage and metastasis.

Conclusions

These signatures of LncRNAs and pseudogenes can predict overall survival and recurrence of RCC. LINC00520, PIK3CD-AS1, LINC01559, CEACAM22P, MSL3P1 and TREML3P could be non-invasive biomarkers of RCC. These data suggest the important roles of LncRNAs and pseudogenes in RCC, and therefore provides us new insights into the prognosis of RCC.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0652-6) contains supplementary material, which is available to authorized users.

Reduced PRC2 function alters male germline epigenetic programming and paternal inheritance

BACKGROUND

Defining the mechanisms that establish and regulate the transmission of epigenetic information from parent to offspring is critical for understanding disease heredity. Currently, the molecular pathways that regulate epigenetic information in the germline and its transmission to offspring are poorly understood.

RESULTS

Here we provide evidence that Polycomb Repressive Complex 2 (PRC2) regulates paternal inheritance. Reduced PRC2 function in mice resulted in male sub-fertility and altered epigenetic and transcriptional control of retrotransposed elements in foetal male germ cells. Males with reduced PRC2 function produced offspring that over-expressed retrotransposed pseudogenes and had altered preimplantation embryo cleavage rates and cell cycle control.

CONCLUSION

This study reveals a novel role for the histone-modifying complex, PRC2, in paternal intergenerational transmission of epigenetic effects on offspring, with important implications for understanding disease inheritance.

LncRNA DUXAP10 modulates cell proliferation in esophageal squamous cell carcinoma through epigenetically silencing p21

Esophageal Squamous Cell Carcinoma (ESCC) belongs to malignant tumor of human digestive system. It has greatly threatened human health both mentally and physically. Long non-coding RNAs have been discovered to be special molecular regulators in various cancers, including ESCC. LncRNA DUXAP10 is a newfound RNA, which is able to improve the progression of cancers ^1-3 . In this study, DUXAP10 was certified to be upregulated in ESCC tissues and cells. Besides, it was positively correlated with short survival time. Moreover, down-expression of DUXAP10 contributed to decreased cell proliferation and metastasis. Silenced DUXAP10 led to increased apoptosis rate and stagnation of cell cycle. Results of mechanism experiments suggested that DUXAP10 motivated ESCC progression through recruiting enhancer of zeste homolog 2 (EZH2) to the promoter of p21. Our findings suggested that the pseudogene-derived from lncRNA DUXAP10 drove the biological progression of ESCC. DUXAP10 was likely to be a potential therapeutic target for ESCC.

Role of Pseudogenes in Tumorigenesis

Functional genomics has provided evidence that the human genome transcribes a large number of non-coding genes in addition to protein-coding genes, including microRNAs and long non-coding RNAs (lncRNAs). Among the group of lncRNAs are pseudogenes that have not been paid attention in the past, compared to other members of lncRNAs. However, increasing evidence points the important role of pseudogenes in diverse cellular functions, and dysregulation of pseudogenes are often associated with various human diseases including cancer. Like other types of lncRNAs, pseudogenes can also function as master regulators for gene expression and thus, they can play a critical role in various aspects of tumorigenesis. In this review we discuss the latest developments in pseudogene research, focusing on how pseudogenes impact tumorigenesis through different gene regulation mechanisms. Given the high sequence homology with the corresponding parent genes, we also discuss challenges for pseudogene research.