Long Non-Coding RNA CASC9 And HIF-1α Form A Positive Feedback Loop To Facilitate Cell Proliferation And Metastasis In Lung Cancer

The strict regulation of HIF-1α by non-coding RNAs: new insight towards proliferation, metastasis, and therapeutic resistance strategies

The hypoxic environment is prominently witnessed in most solid tumors and is associated with the promotion of cell proliferation, epithelial-mesenchymal transition (EMT), angiogenesis, metabolic reprogramming, therapeutic resistance, and metastasis of tumor cells. All the effects are mediated by the expression of a transcription factor hypoxia-inducible factor-1α (HIF-1α). HIF-1α transcriptionally modulates the expression of genes responsible for all the aforementioned functions. The stability of HIF-1α is regulated by many proteins and non-coding RNAs (ncRNAs). In this article, we have critically discussed the crucial role of ncRNAs [such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), Piwi-interacting RNAs (piRNAs), and transfer RNA (tRNA)-derived small RNAs (tsRNAs)] in the regulation of stability and expression of HIF-1α. We have comprehensively discussed the molecular mechanisms and relationship of HIF-1α with each type of ncRNA in either promotion or repression of human cancers and therapeutic resistance. We have also elaborated on ncRNAs that are in clinical examination for the treatment of cancers. Overall, the majority of aspects concerning the relationship between HIF-1α and ncRNAs have been discussed in this article.

Regulating the Expression of HIF-1α or lncRNA: Potential Directions for Cancer Therapy

Previous studies have shown that tumors under a hypoxic environment can induce an important hypoxia-responsive element, hypoxia-induced factor-1α (HIF-1α), which can increase tumor migration, invasion, and metastatic ability by promoting epithelial-to-mesenchymal transition (EMT) in tumor cells. Currently, with the deeper knowledge of long noncoding RNAs (lncRNAs), more and more functions of lncRNAs have been discovered. HIF-1α can regulate hypoxia-responsive lncRNAs under hypoxic conditions, and changes in the expression level of lncRNAs can regulate the production of EMT transcription factors and signaling pathway transduction, thus promoting EMT progress. In conclusion, this review summarizes the regulation of the EMT process by HIF-1α and lncRNAs and discusses their relationship with tumorigenesis. Since HIF-1α plays an important role in tumor progression, we also summarize the current drugs that inhibit tumor progression by modulating HIF-1α.

The Epithelial-Mesenchymal Transition at the Crossroads between Metabolism and Tumor Progression

The transition between epithelial and mesenchymal phenotype is emerging as a key determinant of tumor cell invasion and metastasis. It is a plastic process in which epithelial cells first acquire the ability to invade the extracellular matrix and migrate into the bloodstream via transdifferentiation into mesenchymal cells, a phenomenon known as epithelial–mesenchymal transition (EMT), and then reacquire the epithelial phenotype, the reverse process called mesenchymal–epithelial transition (MET), to colonize a new organ. During all metastatic stages, metabolic changes, which give cancer cells the ability to adapt to increased energy demand and to withstand a hostile new environment, are also important determinants of successful cancer progression. In this review, we describe the complex interaction between EMT and metabolism during tumor progression. First, we outline the main connections between the two processes, with particular emphasis on the role of cancer stem cells and LncRNAs. Then, we focus on some specific cancers, such as breast, lung, and thyroid cancer.

MicroRNA-449a delays lung cancer development through inhibiting KDM3A/HIF-1α axis

Background

It has been established that microRNA (miR)-449a is anti-tumorigenic in cancers, including lung cancer. Therefore, this study further explored miR-449a-mediated mechanism in lung cancer, mainly focusing on lysine demethylase 3A/hypoxia-induced factor-1α (KDM3A/HIF-1α) axis.

Methods

miR-449a, KDM3A and HIF-1α levels in lung cancer tissues and cell lines (A549, H1299 and H460) were measured. Loss- and gain-of-function assays were performed and then cell proliferation, cell cycle, apoptosis, invasion and migration were traced. The relationship between KDM3A, miR-449a and HIF-1α was verified. Tumor growth in vivo was also monitored.

Results

Both lung cancer tissues and cells exhibited reduced miR-449a and raised KDM3A and HIF-1α levels. miR-449a interacted with KDM3A; HIF-1α could bind with KDM3A. Up-regulating miR-449a hindered while suppressing miR-449a induced lung cancer development via mediating HIF-1α. Elevating KDM3A promoted cellular aggression while down-regulating KDM3A had the opposite effects. Up-regulating KDM3A or HIF-1α negated up-regulated miR-449a-induced effects on cellular growth in lung cancer. Restoring miR-449a impaired tumorigenesis in vivo in lung cancer.

Conclusion

It is eventually concluded that miR-449a delays lung cancer development through suppressing KDM3A/HIF-1α axis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02881-8.

Cancer Susceptibility Candidate 9 (CASC9) Promotes Colorectal Cancer Carcinogenesis via mTOR-Dependent Autophagy and Epithelial-Mesenchymal Transition Pathways

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide. Many recent studies have demonstrated that different long non-coding RNAs (lncRNAs) are involved in the initiation, advancement, and metastasis of many cancers including CRC. Cancer susceptibility candidate 9 (CASC9) is an lncRNA that has been reported in many cancers, but its role in CRC is poorly understood. In this study, we aimed to examine the expression of CASC9 in CRC cell lines and to determine the mechanism of action of CASC9 in CRC carcinogenesis.

METHODS

The expression of CASC9 in CRC tissues was compared with normal samples from publicly available datasets in The Cancer Genome Atlas (TCGA) and The Encyclopedia of RNA Interactomes (ENCORI). CASC9 expression was further verified in four CRC cell lines (DLD1, HT-29, SW480, and HCT-116) and normal colorectal cell line (CCD-112CoN) by real-time quantitative polymerase chain reaction (RT-qPCR). After gene silencing in HCT-116 and SW480, Cell Counting Kit-8 assay, clonogenic assay, and wound healing assay were performed to evaluate cell proliferation, viability, and migration index of cells. Western blotting was used to explore the key pathways involved.

RESULTS

CASC9 was significantly upregulated as analyzed from both public datasets TCGA and ENCORI where its overexpression was associated with poor survival of CRC patients. Similarly, CASC9 was significantly overexpressed in the CRC cell lines compared with normal cells studied. The silencing of CASC9 in HCT-116 and SW480 attenuated cell proliferation and migration significantly. Furthermore, pathways investigations showed that silencing of CASC9 significantly induced autophagy, promoted AMP-activated protein kinase (AMPK) phosphorylation, inhibited mTOR and AKT signaling pathways, and altered epithelial-mesenchymal transition (EMT) marker protein expression.

CONCLUSION

We demonstrated that silencing of CASC9 contributes to the reduced CRC cell proliferation and migration by regulating autophagy and AKT/mTOR/EMT signaling. Therefore, CASC9 plays an important role in carcinogenesis, and its expression may act as a prognostic biomarker and a potential therapeutic target of CRC management.

Oncogenic LncRNA CASC9 in Cancer Progression

BACKGROUND

Long non-coding RNAs (LncRNAs), with the length of over 200 nucleotides, that originate from intergenic, antisense, or promoter-proximal regions, are a large family of RNAs that lack coding capacity. Emerging evidences illustrated that LncRNAs played significant roles in a variety of cellular functions and biological processes in profuse human diseases, especially in cancers. Cancer susceptibility candidate 9 (CASC9), as a member of the LncRNAs group, firstly found its oncogenic function in esophageal cancer. In the following recent studies, a growing amount of human malignancies are verified to be correlated with CASC9, most of which are derived from the squamous epithelium tissue. This present review attempts to highlight the latest insights into the expression, functional roles, and molecular mechanisms of CASC9 in different human malignancies.

METHODS

In this review, the latest findings related to the pathophysiological processes of CASC9 in human cancers were summarized and analyzed, and the associated studies collected in systematic retrieval of PubMed used lncRNA and CASA9 as keywords.

RESULTS

CASC9 expression is identified to be aberrantly elevated in a variety of malignancies. The over-expression of CASC9 has been suggested to accelerate cell proliferation, migration, cell growth and drug resistance of cancer cells, while depressing cell apoptosis, revealing its role as an oncogene. Moreover, the current review demonstrated CASC9 as closely related to the neoplastic transformation of squamous epithelial cells and squamous metaplasia in non-squamous epithelial tissues. Finally, we discuss the limitations and tremendous diagnostic/ therapeutic potential of CASC9 in various human cancers.

CONCLUSION

Long non-coding RNA CASC9 likely serve as useful disease biomarkers or therapeutic targets which be effectively applied in the treatment of different kinds of cancers.

Crosstalk of long non-coding RNAs and EMT: Searching the missing pieces of an incomplete puzzle for lung cancer therapy

BACKGROUND

Lung cancer is considered to be the first place among the cancer-related deaths worldwide and demands novel strategies in the treatment of this life-threatening disorder. The aim of this review is to explore regulation of epithelial-to-mesenchymal transition (EMT) by long non-coding RNAs (lncRNAs) in lung cancer.

INTRODUCTION

LncRNAs can be considered as potential factors for targeting in cancer therapy, since they regulate a bunch of biological processes, e.g. cell proliferation, differentiation and apoptosis. The abnormal expression of lncRNAs occurs in different cancer cells. On the other hand, epithelial-to-mesenchymal transition (EMT) is a critical mechanism participating in migration and metastasis of cancer cells.

METHOD

Different databases including Googlescholar, Pubmed and Sciencedirect were used for collecting articles using keywords such as "LncRNA", "EMT", and "Lung cancer".

RESULT

There are tumor-suppressing lncRNAs that can suppress EMT and metastasis of lung cancer cells. Expression of such lncRNAs undergoes down-regulation in lung cancer progression and restoring their expression is of importance in suppressing lung cancer migration. There are tumor-promoting lncRNAs triggering EMT in lung cancer and enhancing their migration.

CONCLUSION

LncRNAs are potential regulators of EMT in lung cancer, and targeting them, both pharmacologically and genetically, can be of importance in controlling migration of lung cancer cells.

Hypoxia-induced lncRNA CASC9 enhances glycolysis and the epithelial-mesenchymal transition of pancreatic cancer by a positive feedback loop with AKT/HIF-1α signaling

Increasing evidence indicates the dysregulations and pivotal roles of lncRNAs in the development and progression of various cancers, including pancreatic cancer. Enhanced glycolytic flux and epithelial-to-mesenchymal transition (EMT) have been considered as important factors in driving the malignance of pancreatic cancer. Here, we sought to evaluate the biological role and involved mechanism of lncRNA CASC9 (CASC9) in pancreatic cancer. Our present study showed that CASC9 was upregulated in various pancreatic cancer cell lines. Loss- and gain-of function of CASC9 demonstrated its critical roles in promoting the glycolysis and EMT phenotypes of pancreatic cancer. Moreover, knockdown of CASC9 inhibited the tumorigenicity and metastasis in vivo. Additionally, our findings showed that hypoxia induced the expression of CASC9 and enhanced the binding of HIF-1α to its promoter. We also demonstrated that the positive feedback loop of CASC9 and the AKT/HIF-1α signaling cascade partially mediated this biological process. Altogether, our results suggest that CASC9 promotes the glycolysis and EMT of pancreatic cancer by a positive feedback loop with AKT/HIF-1α signaling, which is synergistically enhanced by the tumor hypoxic niche. Our study will provide potential therapeutic targets for treating pancreatic cancer.

A Positive Feedback Loop of lncRNA DSCR8/miR-98-5p/STAT3/HIF-1α Plays a Role in the Progression of Ovarian Cancer

Background

Accumulating studies have revealed that long non-coding RNA (lncRNA) and microRNA (miRNA) contribute to ovarian cancer (OC). DSCR8 has been found to mediate hepatocellular carcinoma development, while its role in OC remains to be explored.

Methods

In this study, lncRNA DSCR8 and miR-98-5p expressions in OC tissues and adjacent non-cancer tissues were determined by reverse transcriptase polymerase chain reaction (RT-PCR). Besides, gain-of-function or loss-of-function assays of DSCR8 and miR-98-5p were conducted on OC cell lines SKOV-3 and A2780. Cell proliferation was detected with Cell Counting Kit (CCK)8 and colony formation assay, and western blot was used to test the apoptotic levels of OC cells. Transwell assay was conducted to examine cell invasion, and the epithelial–mesenchymal transition (EMT) of OC cells was tested by western blot. Moreover, luciferase activity assay and RNA immunoprecipitation (RIP) assay were conducted to verify the relationships between DSCR8 and miR-98-5p, miR-98-5p, and signal transducer and activator of transcription 3 (STAT3).

Results

DSCR8 was remarkedly increased in OC tissues and associated with poorer survival of OC patients. Overexpressing DSCR8 promoted cell proliferation, invasion, and EMT but inhibited apoptosis. On the other hand, miR-98-5p was downregulated in OC tissues and relieved the progression of OC. Moreover, overexpressed DSCR8 increased the levels of STAT3 and hypoxia inducible factor 1 alpha (HIF-1α) and dampened the functions of miR-98-5p on OC. Pharmaceutical intervention of STAT3 and HIF-1α significantly altered the expressions of DSCR8 and miR-98-5p.

Conclusion

The present results suggested a positive feedback loop of lncRNA DSCR8/miR-98-5p/STAT3/HIF-α axis in the progression of OC.

Long-Noncoding RNA (lncRNA) in the Regulation of Hypoxia-Inducible Factor (HIF) in Cancer

Hypoxia is dangerous for oxygen-dependent cells, therefore, physiological adaption to cellular hypoxic conditions is essential. The transcription factor hypoxia-inducible factor (HIF) is the main regulator of hypoxic metabolic adaption reducing oxygen consumption and is regulated by gradual von Hippel-Lindau (VHL)-dependent proteasomal degradation. Beyond physiology, hypoxia is frequently encountered within solid tumors and first drugs are in clinical trials to tackle this pathway in cancer. Besides hypoxia, cancer cells may promote HIF expression under normoxic conditions by altering various upstream regulators, cumulating in HIF upregulation and enhanced glycolysis and angiogenesis, altogether promoting tumor proliferation and progression. Therefore, understanding the underlying molecular mechanisms is crucial to discover potential future therapeutic targets to evolve cancer therapy. Long non-coding RNAs (lncRNA) are a class of non-protein coding RNA molecules with a length of over 200 nucleotides. They participate in cancer development and progression and might act as either oncogenic or tumor suppressive factors. Additionally, a growing body of evidence supports the role of lncRNAs in the hypoxic and normoxic regulation of HIF and its subunits HIF-1α and HIF-2α in cancer. This review provides a comprehensive update and overview of lncRNAs as regulators of HIFs expression and activation and discusses and highlights potential involved pathways.

Cancer Susceptibility Candidate 9 (CASC9): A Novel Targetable Long Noncoding RNA in Cancer Treatment

Based on epidemiological data provided by the World Health Organization (2018), cancer is the second most prevalent cause of death worldwide. Several factors are thought to contribute to the high mortality rate in cancer patients, including less-than-optimal diagnostic and therapeutic strategies. Thus, there is an urgent need to identify accurate biomarkers with diagnostic, prognostic, and potential therapeutic applications. In this regard, long noncoding RNAs (lncRNAs) hold immense potential due to their regulatory roles in cancer development and associated cancer hallmarks. Recently, CASC9 transcripts have attracted significant attention due to their altered expression during the pathogenesis of cancer and their apparent contributions to various cancer-associated phenotypes involving a broad spectrum of molecular mechanisms. Here, we have provided an in-depth review describing the known functions of the lncRNA CASC9 in cancer development and progression.