Hypoxia-induced hsa_circ_0000826 is linked to liver metastasis of colorectal cancer

Colon cancer transcriptome

Over the last four decades, methodological innovations have continuously changed transcriptome profiling. It is now feasible to sequence and quantify the transcriptional outputs of individual cells or thousands of samples using RNA sequencing (RNA-seq). These transcriptomes serve as a connection between cellular behaviors and their underlying molecular mechanisms, such as mutations. This relationship, in the context of cancer, provides a chance to unravel tumor complexity and heterogeneity and uncover novel biomarkers or treatment options. Since colon cancer is one of the most frequent malignancies, its prognosis and diagnosis seem to be critical. The transcriptome technology is developing for an earlier and more accurate diagnosis of cancer which can provide better protectivity and prognostic utility to medical teams and patients. A transcriptome is a whole set of expressed coding and non-coding RNAs in an individual or cell population. The cancer transcriptome includes RNA-based changes. The combined genome and transcriptome of a patient may provide a comprehensive picture of their cancer, and this information is beginning to affect treatment decision-making in real-time. A full assessment of the transcriptome of colon (colorectal) cancer has been assessed in this review paper based on risk factors such as age, obesity, gender, alcohol use, race, and also different stages of cancer, as well as non-coding RNAs like circRNAs, miRNAs, lncRNAs, and siRNAs. Similarly, they have been examined independently in the transcriptome study of colon cancer.

Hsa_Circ_0000826 inhibits the proliferation of colorectal cancer by targeting AUF1

Many circular RNAs (circRNAs) are reported to be abnormally expressed during the progression of various tumors, and these circRNAs can be used as anti-tumor targets. Therefore, it is important to identify circRNAs that can be used effectively for the clinical diagnosis and treatment of colorectal cancer (CRC). Here, we report that hsa_Circ_0000826 (Circ_0000826), a circRNA with significantly reduced expression level in CRC tissues, is associated with a poor prognosis in patients. The silencing of Circ_0000826 promotes the proliferation of CRC cells. Conversely, the overexpression of Circ_0000826 restricted CRC cell proliferation both in vitro and in vivo. Furthermore, Circ_0000826 could target AU-rich element RNA-binding protein 1 (AUF1). AUF1, known as heterogeneous nuclear ribonucleoprotein D (hnRNP D), could bind to the c-MYC 3'-UTR and promote c-MYC expression. When Circ_0000826 binds to AUF1, it competitively inhibits the binding of AUF1 to the c-MYC 3'-UTR, which inhibits the c-MYC expression and cell proliferation. These results provide novel insights into the functional mechanism of Circ_0000826 action in CRC progression and indicate its potential use as a therapeutic target in CRC.

Hypoxic Microenvironment-Induced Reduction in PTEN-L Secretion Promotes Non-Small Cell Lung Cancer Metastasis through PI3K/AKT Pathway

Objective

Lung cancer is the leading cause of cancer-related deaths worldwide. The aim of this study was to investigate the effects of hypoxic microenvironment on PTEN-L secretion and the effects of PTEN-L on the metastasis of non-small cell lung cancer (NSCLC) and the potential mechanisms.

Methods

The expression levels of PTEN-L in NSCLC tissues, cells, and cell culture media were detected. The transfection of PTEN-L overexpression construct or HIF-1α-siRNAs was conducted to manipulate the expression of PTEN-L or HIF-1α. NSCLC cells were introduced into 200 μM CoCl2 medium for 72 hours under 37°C to simulate hypoxia. The proliferation and apoptosis of the A549 cells were determined by the Cell Counting Kit-8 assay and Annexin V-FITC/PI-stained flow cytometry assay, respectively. Wound healing assay and transwell invasion assay were used to measure the migration and invasion of A549 cells. The protein expression of PTEN, PTEN-L, PI3K/AKT pathway-related proteins, and HIF-1α was detected by Western blot.

Results

PTEN and PTEN-L are downregulated in lung cancer tissues and cells. The protein expression of PTEN-L in the culture medium of lung cancer cell lines is decreased. The hypoxic microenvironment inhibits PTEN-L secretion. The low level of PTEN-L promotes cell proliferation, migration, and invasion, as well as inhibits apoptosis of A549 cells. The overexpression of PTEN-L attenuated the activation of the PI3K/AKT pathway by the hypoxic microenvironment. The knockdown of HIF-1α upregulates PTEN-L secretion under hypoxia.

Conclusions

The hypoxic microenvironment inhibits PTEN-L secretion and thus activates PI3K/AKT pathway to induce proliferation, migration, and invasion promotion, and apoptosis inhibition in NSCLC cells.

Colorectal liver metastasis: molecular mechanism and interventional therapy

Colorectal cancer (CRC) is one of the most frequently occurring malignancy tumors with a high morbidity additionally, CRC patients may develop liver metastasis, which is the major cause of death. Despite significant advances in diagnostic and therapeutic techniques, the survival rate of colorectal liver metastasis (CRLM) patients remains very low. CRLM, as a complex cascade reaction process involving multiple factors and procedures, has complex and diverse molecular mechanisms. In this review, we summarize the mechanisms/pathophysiology, diagnosis, treatment of CRLM. We also focus on an overview of the recent advances in understanding the molecular basis of CRLM with a special emphasis on tumor microenvironment and promise of newer targeted therapies for CRLM, further improving the prognosis of CRLM patients.

EWSR1-induced circNEIL3 promotes glioma progression and exosome-mediated macrophage immunosuppressive polarization via stabilizing IGF2BP3

Background

Gliomas are the most common malignant primary brain tumours with a highly immunosuppressive tumour microenvironment (TME) and poor prognosis. Circular RNAs (circRNA), a newly found type of endogenous noncoding RNA, characterized by high stability, abundance, conservation, have been shown to play an important role in the pathophysiological processes and TME remodelling of various tumours.

Methods

CircRNA sequencing analysis was performed to explore circRNA expression profiles in normal and glioma tissues. The biological function of a novel circRNA, namely, circNEIL3, in glioma development was confirmed both in vitro and in vivo. Mechanistically, RNA pull-down, mass spectrum, RNA immunoprecipitation (RIP), luciferase reporter, and co-immunoprecipitation assays were conducted.

Results

We identified circNEIL3, which could be cyclized by EWS RNA-binding protein 1(EWSR1), to be upregulated in glioma tissues and to correlate positively with glioma malignant progression. Functionally, we confirmed that circNEIL3 promotes tumorigenesis and carcinogenic progression of glioma in vitro and in vivo. Mechanistically, circNEIL3 stabilizes IGF2BP3 (insulin-like growth factor 2 mRNA binding protein 3) protein, a known oncogenic protein, by preventing HECTD4-mediated ubiquitination. Moreover, circNEIL3 overexpression glioma cells drives macrophage infiltration into the tumour microenvironment (TME). Finally, circNEIL3 is packaged into exosomes by hnRNPA2B1 and transmitted to infiltrated tumour associated macrophages (TAMs), enabling them to acquire immunosuppressive properties by stabilizing IGF2BP3 and in turn promoting glioma progression.

Conclusions

This work reveals that circNEIL3 plays a nonnegligible multifaceted role in promoting gliomagenesis, malignant progression and macrophage tumour-promoting phenotypes polarization, highlighting that circNEIL3 is a potential prognostic biomarker and therapeutic target in glioma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01485-6.

Exosomal circEIF3K from cancer-associated fibroblast promotes colorectal cancer (CRC) progression via miR-214/PD-L1 axis

Background

Tumor microenvironment (e.g., cancer-associated fibroblast) plays a key role in cancer tumorigenesis and metastasis. However, the detailed mechanism of whether hypoxia promotes CRC progression via tumor microenvironment remains unclear.

Methods

In this study, circEIF3K exosome was examined by NanoSight Tracking Analysis and RT-qPCR. We used cell colony formation assay, transwell assay and tube formation assay to determine proliferation, invasion and metastasis of HCT116 or SW620 cells. Xenograft tumor assay was employed to show in vivo tumor growth of HCT116 cells.

Results

We found that hypoxia could induce secretion of circEIF3K exosome. Conditioned medium (CM) and exosome from circEIF3K knockdown CAF significantly attenuated proliferation, invasion and tube formation of HCT116 or SW620 cells, which could be reverted by miR-214 under hypoxia treatment. Besides, we observed that circEIF3K knockdown evidently impaired tumor growth in mice. TCGA dataset analysis showed that low expression of circEIF3K was observed in normal tissues and associated with prolonged survival time. Finally, PD-L1 was confirmed as important target for miR-214 in CRC.

Conclusion

In conclusion, our study reveals that a novel axis circEIF3K/miR-214/PD-L1 mediates hypoxia-induced CRC progression via CAF, providing the rationale for developing new targeted therapeutics to treat CRC.

Cross-platform comparison of next-generation sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for detecting KRAS/NRAS/BRAF/PIK3CA mutations in cfDNA from metastatic colorectal cancer patients

Background

Examining tumor KRAS/NRAS/BRAF/PIK3CA status in metastatic colorectal cancer (mCRC) is essential for treatment selection and prognosis evaluation. Cell‐free DNA (cfDNA) in plasma is a feasible source for tumor gene analysis.

Methods

In this study, we recruited mCRC patients and analyzed their KRAS/NRAS/BRAF/PIK3CA status in cfDNA using two platforms, next‐generation sequencing (NGS) and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF). The performance between the two platforms and the concordance rate between cfDNA and tissue were analyzed. The relationship between cfDNA‐related variables and clinical variables was also assessed. Tumor mutations in cfDNA from patients receiving continuous treatments were monitored in the follow‐ups.

Results

Next‐generation sequencing and MALDI‐TOF had similar specificity (100.0% vs. 99.3%) and negative predictive value (99.9% vs. 99.4%), whereas NGS had higher sensitivity (97.1% vs. 85.3% of MALDI‐TOF) and positive predictive value (100% vs. 82.9% of MALDI‐TOF). The overall concordance rate of NGS and MALDI‐TOF was 98.6%. For the reportable types of mutations in both cfDNA and tissue, the concordance rate was 96.1%. Among 28 tissue‐positive patients, the allele frequencies of tumor mutations in cfDNA were higher in patients with primary tumor burden (p = 0.0141). Both CEA and CA 19‐9 were positively correlated with cfDNA concentration (r = 0.3278 and r = 0.3992). The allele frequencies of tumor mutations changed with disease progression.

Conclusions

Next‐generation sequencing showed slightly better performance in detecting cfDNA mutations and was more suitable for clinical practice. cfDNA‐related variables reflected the tumor status and showed a promising potential in monitoring disease progression.

Circ_0007031 Silencing Inhibits Cell Proliferation and Induces Cell Apoptosis via Downregulating MELK at a miR-485-3p-Dependent Way in Colorectal Cancer

Colorectal cancer (CRC) is a malignant cancer with an increasing incidence. Circular RNA (circRNA) is recently found to participate in the regulation of CRC progression. However, the role of circ_0007031 in CRC malignant progression remains elusive. 50 CRC patients were implicated in this study. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the RNA expression of circ_0007031, microRNA-485-3p (miR-485-3p) and maternal embryonic leucine zipper kinase (MELK). Western blot analysis was conducted to determine protein expression. Cell viability and proliferation were demonstrated by cell counting kit-8 and 5-Ethynyl-29-deoxyuridine (EdU) assays, respectively. Cell cycle and apoptosis were investigated by flow cytometry analysis. The interaction among circ_0007031, miR-485-3p and MELK was predicted by online databases, and identified by dual-luciferase reporter assay. Mouse model assay was conducted to reveal the effect of circ_0007031 on tumor formation in vivo. Circ_0007031 and MELK expression were obviously increased, while miR-485-3p expression was decreased in CRC tissues and cells compared with normal colorectal tissues or cells. Circ_0007031 knockdown repressed proliferation, whereas induced cell arrest at G0/G1 phase and apoptosis. On the opposite, circ_0007031 overexpression promoted cell proliferation and induced cell arrest at S phase. Additionally, miR-485-3p inhibitors attenuated circ_0007031 silencing-mediated CRC cell malignancy. MiR-485-3p was unveiled to regulate CRC cell processes via targeting MELK. Circ_0007031 controlled MELK expression via interacting with miR-485-3p. Furthermore, circ_0007031 contributed to tumor formation in vivo. Circ_0007031 knockdown repressed CRC malignant progression by reducing MELK expression through associating with miR-485-3p, suggesting that circ_0007031 was a potential target for the therapy of CRC.

Oncogenic Functions and Clinical Significance of Circular RNAs in Colorectal Cancer

Colorectal cancer (CRC) is ranked as the second most commonly diagnosed disease in females and the third in males worldwide. Therefore, the finding of new more reliable biomarkers for early diagnosis, for prediction of metastasis, and resistance to conventional therapies is an important challenge in overcoming the disease. The current review presents circular RNAs (circRNAs) with their unique features as potential prognostic and diagnostic biomarkers in CRC. The review highlights the mechanism of action and the role of circRNAs with oncogenic functions in the CRC as well as the association between their expression and clinicopathological characteristics of CRC patients. The comprehension of the role of oncogenic circRNAs in CRC pathogenesis is growing rapidly and the next step is using them as suitable new drug targets in the personalized treatment of CRC patients.

Plasma cell-free circRNAs panel act as fingerprint predicts the occurrence of laryngeal squamous cell carcinoma

Background: Circular RNAs (circRNAs) have recently emerged as a new class of RNAs, highly enriched in the human tissues and very stable within cells, exosomes and body fluids. In this study, we aimed to screen the plasma cell-free derived circRNAs in laryngeal squamous cell carcinoma (LSCC) and investigate whether these circRNAs could predicted LSCC as potential biomarkers.

Methods: The circRNA microarray was employed with three samples in each group to screen the dysregulated circRNAs isolated from plasma samples. The top 20 circRNAs were first selected as candidates with the upregulated level in the plasma of LSCC.

Results: Further validation found that only circ_0019201, circ_0011773 and circ_0122790 was consistent with training set. The ROC curve also revealed a high diagnostic ability an area under ROC curve value (AUC) for single circRNA and combined. The AUC for circ_0019201, circ_0011773 and circ_0122790 and the combined was 0.933, 0.908, 0.965 and 0.990 in training set. For the validation set, the AUC was 0.766, 0.864, 0.908 and 0.951. The three circRNAs were further investigated with stable expression in human plasma samples.

Conclusions: The plasma derived circ_0019201, circ_0011773 and circ_0122790 might be the potential biomarker for predicting the LSCC.

Emerging Mechanisms and Treatment Progress on Liver Metastasis of Colorectal Cancer

Colorectal cancer is currently the third largest malignant tumor in the world, with high new cases and high mortality. Metastasis is one of the most common causes of death of colorectal cancer, of which liver metastasis is the most fatal. Since the beginning of the Human Genome Project in 2001, people have gradually recognized the 3 billion base pairs that make up the human genome, of which only about 1.5% of the nucleic acid sequences are used for protein coding, including proto-oncogenes and tumor suppressor genes. A large number of differences in the expression of proto-oncogenes and tumor suppressor genes have also been found in the study of colorectal cancer, which proves that they are also actively involved in the progression of colorectal cancer and promote the occurrence of liver metastasis. Except for 1.5% of the coding sequence, the rest of the nucleic acid sequence does not encode any protein, which is called non-coding RNA. With the deepening of research, genome sequences without protein coding potential that were originally considered “junk sequences” may have important biological functions. Many years of studies have found that a large number of abnormal expression of ncRNA in colorectal cancer liver metastasis, indicating that ncRNA plays an important role in it. To explore the role and mechanism of these coding sequences and non-coding RNA in liver metastasis of colorectal cancer is very important for the early diagnosis and treatment of liver metastasis of colorectal cancer. This article reviews the coding genes and ncRNA that have been found in the study of liver metastasis of colorectal cancer in recent years, as well as the mechanisms that have been identified or are still under study, as well as the clinical treatment of liver metastasis of colorectal cancer.

Circular RNA in colorectal cancer

Circular RNA (circRNA) is a highly abundant type of single-stranded non-coding RNA. Novel research has discovered many roles of circRNA in colorectal cancer (CRC) including proliferation, metastasis and apoptosis. Furthermore, circRNAs also play a role in the development of drug resistance and have unique associations with tumour size, staging and overall survival in CRC that lend circRNAs the potential to serve as diagnostic and prognostic biomarkers. Among cancers worldwide, CRC ranks second in mortality and third in incidence. In order to have a better understanding of the influence of circRNA on CRC development and progression, this review summarizes the role of specific circRNAs in CRC and evaluates their potential value as therapeutic targets and biomarkers for CRC. We aim to provide insight in the development of therapy and clinical decision-making.

Comprehensive landscape and future perspectives of circular RNAs in colorectal cancer

Colorectal cancer (CRC) is a common hereditary tumor that is often fatal. Its pathogenesis involves multiple genes, including circular RNAs (circRNAs). Notably, circRNAs constitute a new class of noncoding RNAs (ncRNAs) with a covalently closed loop structure and have been characterized as stable, conserved molecules that are abundantly expressed in tissue/development-specific patterns in eukaryotes. Based on accumulating evidence, circRNAs are aberrantly expressed in CRC tissues, cells, exosomes, and blood from patients with CRC. Moreover, numerous circRNAs have been identified as either oncogenes or tumor suppressors that mediate tumorigenesis, metastasis and chemoradiation resistance in CRC. Although the regulatory mechanisms of circRNA biogenesis and functions remain fairly elusive, interesting results have been obtained in studies investigating CRC. In particular, the expression of circRNAs in CRC is comprehensively modulated by multiple factors, such as splicing factors, transcription factors, specific enzymes and cis-acting elements. More importantly, circRNAs exert pivotal effects on CRC through various mechanisms, including acting as miRNA sponges or decoys, interacting with RNA binding proteins, and even translating functional peptides. Finally, circRNAs may serve as promising diagnostic and prognostic biomarkers and potential therapeutic targets in the clinical practice of CRC. In this review, we discuss the dysregulation, functions and clinical significance of circRNAs in CRC and further discuss the molecular mechanisms by which circRNAs exert their functions and how their expression is regulated. Based on this review, we hope to reveal the functions of circRNAs in the initiation and progression of cancer and highlight the future perspectives on strategies targeting circRNAs in cancer research.

Hypoxia-induced hsa_circ_0000826 is linked to liver metastasis of colorectal cancer

Background

hsa_circ_0000826 has been previously linked to CRC through the competing endogenous RNA network; however, the upstream driver of hsa_circ_0000826 elevation remains unknown. In this study, we aim to elucidate the effect of hypoxia‐induced hsa_circ_0000826 on CRC tumorigenesis and metastasis.

Methods

RNA scope assay was used to evaluate the expression of hsa_circ_0000826 in CRC cells under hypoxia condition. The effects of hsa_circ_0000826 on phenotypes of CRC cells were evaluated through cell migration and invasion assay. The nude, AOM‐DSS model mice and APC^Min/+ mice were used to investigate the relationship between circ_0000826, hypoxia, and CRC in mice. A total of 100 CRC tissue samples, as well as the paired adjacent tissues, were collected, and qRT‐PCR assay was used to detect the expression of hsa_circ_0000826 in these samples.

Results

Hypoxia‐induced hsa_circ_0000826 overexpression can increase the malignant phenotypes, tumor formation, and metastasis capability of CRC cells in vitro. mmu_circ_0000826 levels were significantly increased in the CRC tissues from AOM‐DSS and APC mice model under hypoxia conditions. Further, the hypoxia‐induced upregulation of mmu_circ_0000826 can also promote CRC tumorigenesis and liver metastasis in vivo. The expression of hsa_circ_0000826 in serum was significantly increased in CRC tissues in 100‐pair of CRC and according to the adjacent normal tissues by qRT‐PCR assays. Moreover, the expression levels of hsa_circ_0000826 in serum of patient with liver metastasis were significantly increased than those without metastasis.

Conclusion

Our results suggested that hsa_circ_0000826 was induced by the hypoxia in CRC, which can be a potential biomarker of CRC liver metastasis.