Up-regulation and clinical relevance of novel helicase homologue DHX32 in colorectal cancer

Synthetic lethal interactions of DEAD/H-box helicases as targets for cancer therapy

DEAD/H-box helicases are implicated in virtually every aspect of RNA metabolism, including transcription, pre-mRNA splicing, ribosomes biogenesis, nuclear export, translation initiation, RNA degradation, and mRNA editing. Most of these helicases are upregulated in various cancers and mutations in some of them are associated with several malignancies. Lately, synthetic lethality (SL) and synthetic dosage lethality (SDL) approaches, where genetic interactions of cancer-related genes are exploited as therapeutic targets, are emerging as a leading area of cancer research. Several DEAD/H-box helicases, including DDX3, DDX9 (Dbp9), DDX10 (Dbp4), DDX11 (ChlR1), and DDX41 (Sacy-1), have been subjected to SL analyses in humans and different model organisms. It remains to be explored whether SDL can be utilized to identity druggable targets in DEAD/H-box helicase overexpressing cancers. In this review, we analyze gene expression data of a subset of DEAD/H-box helicases in multiple cancer types and discuss how their SL/SDL interactions can be used for therapeutic purposes. We also summarize the latest developments in clinical applications, apart from discussing some of the challenges in drug discovery in the context of targeting DEAD/H-box helicases.

DEAH-box polypeptide 32 promotes hepatocellular carcinoma progression via activating the β-catenin pathway

PURPOSE

Hepatocellular carcinoma (HCC) is refractory cancer with high morbidity and high mortality. DEAH-box polypeptide 32 (DHX32) was upregulated in several types of malignancies and predicted poor prognosis. Herein, we investigated the role of DHX32 in HCC progression.

METHODS

The expression of DHX32, β-catenin, and epithelial-mesenchymal transition (EMT)-related makers were determined by Western blot and quantitative real-time PCR assays. Cell proliferation was tested by EdU cell proliferation assay. The effect of DHX32 and β-catenin on cell migration and invasion were detected by wound-healing and Traswell invasion assays. Tumour xenografts were performed to determine the effect of DHX32 on HCC tumour growth.

RESULTS

High level of DHX32 expression was associated with reduced overall survival in HCC patients. DHX32 expression was upregulated in human HCC cells and ectopic expression of DHX32 induced EMT, promoted the mobility and proliferation of HCC cells, and enhanced tumour growth in vivo. Silencing DHX32 reversed EMT, inhibited the malignancy behaviors of HCC cells, and suppressed tumour growth. Mechanistically, silencing DHX32 decreased the expression of β-cateninin in nucleus and β-catenin siRNA abrogated DHX32-mediated HCC progression.

CONCLUSION

DHX32 was an attractive regulator of HCC progression and indicated DHX32 canserve as a potential biomarker and therapeutic target for HCC patients.

Ace2 and Tmprss2 Expressions Are Regulated by Dhx32 and Influence the Gastrointestinal Symptoms Caused by SARS-CoV-2

Studies showed that the gastrointestinal (GI) tract is one of the most important pathways for SARS-CoV-2 infection and coronavirus disease 2019 (COVID-19). As SARS-CoV-2 cellular entry depends on the ACE2 receptor and TMPRSS2 priming of the spike protein, it is important to understand the molecular mechanisms through which these two proteins and their cognate transcripts interact and influence the pathogenesis of COVID-19. In this study, we quantified the expression, associations, genetic modulators, and molecular pathways for Tmprss2 and Ace2 mRNA expressions in GI tissues using a systems genetics approach and the expanded family of highly diverse BXD mouse strains. The results showed that both Tmprss2 and Ace2 are highly expressed in GI tissues with significant covariation. We identified a significant expression quantitative trait locus on chromosome 7 that controls the expression of both Tmprss2 and Ace2. Dhx32 was found to be the strongest candidate in this interval. Co-expression network analysis demonstrated that both Tmprss2 and Ace2 were located at the same module that is significantly associated with other GI-related traits. Protein-protein interaction analysis indicated that hub genes in this module are linked to circadian rhythms. Collectively, our data suggested that genes with circadian rhythms of expression may have an impact on COVID-19 disease, with implications related to the timing and treatment of COVID-19.

The predictive value of RNA binding proteins in colon adenocarcinoma

Background

RNA binding proteins (RBPs) play an important role in regulating post-transcriptional gene expression and have been reported to be closely associated with the occurrence and development of tumors. However, the effect of RBPs in colon cancer remains unclear.

Methods

We downloaded clinical information and transcriptome data of colon adenocarcinoma (COAD) from The Cancer Genome Atlas database (TCGA) database. After combining this data, we identified differentially expressed RBPs in normal and cancer tissues and subsequently performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Prognosis-related RBPs were identified via Cox regression analysis. The samples were randomly divided into two groups; an experimental group and a control group. A predictive model was constructed by dividing the experimental group into high- and low-risk subgroups based on the scores of the prognostic-related RBPs, and the prognosis of samples in these two subgroups was compared. Then, this model was applied to the control group. Finally, the model results were verified based on an online survival database and the Human Protein Atlas (HPA) database.

Results

A total of 469 differentially expressed RBPs were identified in normal and cancer tissues. Ten prognosis-related RBPs were determined by Cox regression analysis. In the prognostic prediction model, the prognosis of high-risk patients in the experimental group was worse than that in the low-risk group, and the same result was obtained in the control group. In addition, the risk score in the Cox regression analysis showed that the model could be used as an independent prognostic factor (P<0.001). The results of the online survival analysis tool, HPA database, and the model were consistent.

Conclusions

Some specific RBPs are significantly associated with the prognosis of patients with COAD, and this finding may provide important information for the future diagnosis and treatment of patients with COAD.

Structure and function of DEAH-box helicase 32 and its role in cancer

DEAH-box helicase 32 (DHX32) is an RNA helicase with unique structural characteristics that is involved in numerous biological processes associated with RNA, including ribosome biosynthesis, transcription, mRNA splicing and translation. Increasing evidence suggests that abnormal DHX32 expression contributes to cancer initiation and development, due to dysregulated cell proliferation, differentiation, apoptosis and other processes. In the current review, the discovery, structure and function of DHX32, as well as the association between abnormal DHX32 expression and tumors are discussed. DHX32 expression is downregulated in acute lymphoblastic leukemia, but upregulated in solid tumors, including colorectal and breast cancer. Furthermore, DHX32 expression levels are associated with the pathological and clinical features of the cancer. Therefore, DHX32 may serve as a novel liquid biopsy marker for auxiliary diagnosis and prognosis screening, as well as a possible target for cancer therapy. The molecular mechanism underlying the contribution of DHX32 towards the initiation and development of cancer requires further investigation for the development of anticancer treatments based on manipulating DHX32 expression and function.

DHX32 Promotes Angiogenesis in Colorectal Cancer Through Augmenting β-catenin Signaling to Induce Expression of VEGFA

We previously reported that overexpression of DHX32 contributes to the growth and metastasis of colorectal cancer (CRC). However, the underlying mechanism is not largely characterized. Herein, we reported that DHX32 in CRC cells upregulated expression of vascular endothelial growth factor A (VEGFA) at the transcription level through interacting with and stabilizing β-catenin. This promoted the recruitment of host endothelial cells to the tumor, and therefore, formation of microvessel in the tumor. Xenograft model revealed that depletion of DHX32 in CRC cells significantly reduced the microvessel density in the grafts and suppressed the growth of grafts. Furthermore, the expression level of DHX32 was positively associated with microvessel density in human CRC and poor outcome of CRC patients. Therefore, the report demonstrates that DHX32 is a pro-angiogenic factor, that inhibition of DHX32-β-catenin pathway can provide a strategy for CRC treatment, and that the expression level of DHX32 has the potential to serve as a biomarker for CRC diagnosis and prognosis.

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DHX32 upregulates VEGFA expression through interacting with and stabilizing β-catenin.

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DHX32 promotes colorectal cancer cells to recruit endothelial cells and induces angiogenesis.

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DHX32 is associated with tumor angiogenesis and poor prognosis of colorectal cancer patients.

Tumor angiogenesis is required for cancer growth and metastasis. Understanding the molecular mechanism by which cancer cells promote angiogenesis is required to develop effective cancer treatment. In this study, we reported that DHX32 is a pro-angiogenic factor in colorectal cancer. Aberrantly expressed DHX32 promoted tumor angiogenesis by stabilizing β-catenin and increasing the expression of vascular endothelial growth factor. The results suggested that suppression of DHX32 can be of therapeutic value for colorectal cancer and that expression level of DHX32 has the potential to serve as a biomarker for colorectal cancer diagnosis and prognosis.

Wanted DEAD/H or Alive: Helicases Winding Up in Cancers

Cancer is one of the most studied areas of human biology over the past century. Despite having attracted much attention, hype, and investments, the search to find a cure for cancer remains an uphill battle. Recent discoveries that challenged the central dogma of molecular biology not only further increase the complexity but also demonstrate how various types of noncoding RNAs such as microRNA and long noncoding RNA, as well as their related processes such as RNA editing, are important in regulating gene expression. Parallel to this aspect, an increasing number of reports have focused on a family of proteins known as DEAD/H-box helicases involved in RNA metabolism, regulation of long and short noncoding RNAs, and novel roles as "editing helicases" and their association with cancers. This review summarizes recent findings on the roles of RNA helicases in various cancers, which are broadly classified into adult solid tumors, childhood solid tumors, leukemia, and cancer stem cells. The potential small molecule inhibitors of helicases and their therapeutic value are also discussed. In addition, analyzing next-generation sequencing data obtained from public portals and reviewing existing literature, we provide new insights on the potential of DEAD/H-box helicases to act as pharmacological drug targets in cancers.

DHX32 expression is an indicator of poor breast cancer prognosis

Emerging evidence suggests that DEAH-box polypeptide 32 (DHX32) serves an important role in the progression and metastasis of cancer. However, the role of DHX32 in breast cancer remains to be completely elucidated. The aim of the present study was to evaluate the expression and clinical significance of DHX32 in breast cancer. The reverse transcription-quantitative polymerase chain reaction was performed to analyze DHX32 messenger (m)RNA expression, and western blotting and immunohistochemistry were performed to examine DHX32 protein expression in breast cancer and adjacent non-cancerous tissues. The association in breast cancer between DHX32 expression, clinicopathological features and prognosis was analyzed using 193 breast cancer tissue samples. The results of the present study demonstrated that breast cancer tissues exhibited increased DHX32 mRNA and protein expression compared with adjacent non-cancerous tissues (P<0.001). In addition, DHX32 expression was significantly associated with breast cancer clinical stage (P=0.006), histological grade (P=0.029), lymph node metastasis (P<0.001) and expression of the proliferation marker Ki-67 (P=0.004). Kaplan-Meier estimator analysis indicated that increased DHX32 expression is associated with poor prognosis in patients with breast cancer. Furthermore, the Cox proportional hazards model indicated that DHX32 expression is an independent prognostic factor for decreased overall survival and disease-free survival in patients with breast cancer. In conclusion, the results of the present study suggest that DHX32 overexpression is an unfavorable prognostic biomarker in breast cancer and a potential therapeutic target of future breast cancer treatments.

Identification and in silico analysis of cattle DExH/D box RNA helicases

The helicases are motor proteins participating in a range of nucleic acid metabolisms. RNA helicase families are characterized by the presence of conserved motifs. This article reports a comprehensive in silico analysis of Bos taurus DExH/D helicase members. Bovine helicases were identified using the helicase domain sequences including 38 DDX (DEAD box) and 16 DHX (DEAH box) members. Signature motifs were used for the validation of these proteins. Putative sub cellular localization and phylogenetic relationship for these RNA helicases were established. Comparative analysis of these proteins with human DDX and DHX members was carried out. These bovine helicase have been assigned putative physiological functions. Present study of cattle DExH/D helicase will provides an invaluable source for the detailed biochemical and physiological research on these members.

Overexpression of DHX32 contributes to the growth and metastasis of colorectal cancer

Our previous work demonstrates that DHX32 is upregulated in colorectal cancer (CRC) compared to its adjacent normal tissues. However, how overexpressed DHX32 contributes to CRC remains largely unknown. In this study, we reported that DHX32 was overexpressed in human colon cancer cells. Overexpressed DHX32 promoted SW480 cancer cells proliferation, migration, and invasion, as well as decreased the susceptibility to chemotherapy agent 5-Fluorouracil. Furthermore, PCR array analyses revealed that depleting DHX32 in SW480 colon cancer cells suppressed expression of WISP1, MMP7 and VEGFA in the Wnt pathway, and anti-apoptotic gene BCL2 and CA9, however, elevated expression of pro-apoptotic gene ACSL5. The findings suggested that overexpressed DHX32 played an important role in CRC progression and metastasis and that DHX32 has the potential to serve as a biomarker and a novel therapeutic target for CRC.

Perturbations of RNA helicases in cancer

Helicases are implicated in most stages of the gene expression pathway, ranging from DNA replication, RNA transcription, splicing, RNA transport, ribosome biogenesis, mRNA translation, RNA storage and decay. These enzymes utilize energy derived from nucleotide triphosphate hydrolysis to remodel ribonucleoprotein complexes, RNA, or DNA and in this manner affect the information content or output of RNA. Several RNA helicases have been implicated in the oncogenic process--either through altered expression levels, mutations, or due to their role in pathways required for tumor initiation, progression, maintenance, or chemosensitivity. The purpose of this review is to highlight those RNA helicases for which there is significant evidence implicating them in cancer biology.

The landscape of alternative splicing in buccal mucosa squamous cell carcinoma

OBJECTIVES

Alternative splicing (AS) is a key regulatory mechanism in the process of protein synthesis generating transcriptome and proteome diversity. In this study, we attempted to identify alternative splicing in a pair of BMSCC cancer and adjacent normal tissue using RNAseq datasets and also assessed the potential of these datasets to provide quantitative measurements for alternative splicing levels.

MATERIALS AND METHODS

We performed high-throughput sequencing of buccal mucosal cancer and healthy tissue cDNA library which resulted in a transcriptome map of BMSCC cancer. RNAseq analysis was performed to assess alternative splicing complexity in cancer tissue and to search splice junction sequences that represent candidate 'new' splicing events. The splice junctions were predicted by SpliceMap software and putative assembled transcripts validated using the RT-PCR. We also analyzed the coding potential of alternative spliced candidate by HMMER.

RESULTS

We detected a total of 11 novel splice junctions derived mostly from alternate 5' splice site; including two of them which contained new translation initiation sites (TISs). We have identified novel IgG pseudogene and a fusion transcript of MEMO1 and RPS9, which were further confirmed by PCR from genomic DNA. We also found novel putative long non-coding RNA (lncRNA), which is antisense to SPINK5 gene. The coding potential of these AS variants revealed that alternative splicing caused premature termination, insertion/deletion of amino acid (s) or formation of novel N-terminus.

CONCLUSIONS

Differential splicing of these novel AS variants between cancer and adjacent normal tissue suggests their involvement in BMSCC cancer development and progression.