Hypoxia-induced lncRNA STEAP3-AS1 activates Wnt/β-catenin signaling to promote colorectal cancer progression by preventing m6A-mediated degradation of STEAP3 mRNA

Abstract

Background Hypoxia, a typical hallmark of solid tumors, exhibits an essential role in the progression of colorectal cancer (CRC), in which the dysregulation of long non-coding RNAs (lncRNAs) is frequently observed. However, the underlying mechanisms are not clearly defined. Methods The TCGA database was analyzed to identify differential lncRNA expression involved in hypoxia-induced CRC progression. qRT-PCR was conducted to validate the upregulation of lncRNA STEAP3-AS1 in CRC cell lines and tumor-bearing mouse and zebrafish models under hypoxia. ChIP-qRT-PCR was used to detect the transcriptional activation of STEAP3-AS1 mediated by HIF-1α. RNA-seq, fluorescent in situ hybridization, RNA pulldown, RNA immunoprecipitation, co-immunoprecipitation, immunofluorescence and immunoblot experiments were used to ascertain the involved mechanisms. Functional assays were performed in both in vitro and in vivo models to investigate the regulatory role of STEAP3-AS1/STEAP3/Wnt/β-catenin axis in CRC proliferation and metastasis. Results Here, we identified a hypoxia-induced antisense lncRNA STEAP3-AS1 that was highly expressed in clinical CRC tissues and positively correlated with poor prognosis of CRC patients. Upregulation of lncRNA STEAP3-AS1, which was induced by HIF-1α-mediated transcriptional activation, facilitated the proliferation and metastasis of CRC cells both in vitro and in vivo. Mechanistically, STEAP3-AS1 interacted competitively with the YTH domain-containing family protein 2 (YTHDF2), a N6-methyladenosine (m6A) reader, leading to the disassociation of YTHDF2 with STEAP3 mRNA. This effect protected STEAP3 mRNA from m6A-mediated degradation, enabling the high expression of STEAP3 protein and subsequent production of cellular ferrous iron (Fe2+). Increased Fe2+ levels elevated Ser 9 phosphorylation of glycogen synthase kinase 3 beta (GSK3β) and inhibited its kinase activity, thus releasing β-catenin for nuclear translocation and subsequent activation of Wnt signaling to support CRC progression. Conclusions Taken together, our study highlights the mechanisms of lncRNA STEAP3-AS1 in facilitating CRC progression involving the STEAP3-AS1/STEAP3/Wnt/β-catenin axis, which may provide novel diagnostic biomarkers or therapeutic targets to benefit CRC treatment. Graphical abstract Hypoxia-induced HIF-1α transcriptionally upregulates the expression of lncRNA STEAP3-AS1, which interacts competitively with YTHDF2, thus upregulating mRNA stability of STEAP3 and consequent STEAP3 protein expression. The enhanced STEAP3 expression results in production of cellular ferrous iron (Fe2+), which induces the Ser 9 phosphorylation and inactivation of GSK3β, releasing β-catenin for nuclear translocation and contributing to subsequent activation of Wnt signaling to promote CRC progression.

Effects of Long Non-Coding RNAs Induced by the Gut Microbiome on Regulating the Development of Colorectal Cancer

“…A growing body of evidence states that numerous lncRNAs with aberrant expression, including HOTAIR, CCAT1, and LINC0065, are found in CRC [ 24 , 25 , 26 ]. Based on the aforementioned complex biogenesis and molecular regulation mechanisms, the abnormally expressed lncRNAs play a significant role in regulating many signaling pathways, such as Wnt and NF-κB, thus affecting various aspects of CRC occurrence, development, diagnosis, and prognosis [ 8 , 27 ]. The various pathophysiological mechanisms of CRC mediated by aberrantly produced lncRNAs offer a fresh viewpoint for research on the disease.…”

“…SULF1 can remove sulfate groups from proteoglycans, and proteoglycan modifications are important for protein interactions and cytokine signaling [ 69 , 70 ]. The activation of the canonical Wnt pathway by SULF1 overexpression has been demonstrated to promote the proliferation and metastasis of CRC cells [ 8 , 71 ] ( Figure 3 ). In summary, ETBF can upregulate JMJD2B to induce lncRNA AERRIE expression and subsequently activate SULF1, thus contributing to CRC cell proliferation and metastasis.…”

“…Recent studies have revealed that abnormal expressions of long non-coding RNAs (lncRNAs), which are RNAs longer than 200 nucleotides and without the ability to code for proteins, are linked to the occurrence, progression, recurrence, metastasis, and chemoresistance of CRC, which can assist in diagnosis, determining prognosis, and providing therapeutic targets in CRC [ 7 , 8 , 9 , 10 ]. The lncRNAs are often expressed at lower levels but show more cell type-specific expression patterns than protein-coding genes [ 11 ].…”

“…One study found only low levels of overlap in the expressions of lncRNAs in the colon of mice colonized with specific different gut microbes compared to germ-free mice, and most of the changed lncRNAs were type-specific, revealing that the expression of lncRNAs was altered differently depending on the type of bacterial colonization [ 16 ]. This finding raised the possibility of the influence of the gut microbiome on the expressions of lncRNAs, which in turn can target their downstream genes and activate signaling pathways, like Wnt and nuclear factor kappa-B (NF-κB), thereby influencing the course of CRC development [ 8 , 17 ]. However, due to limited knowledge about the connections between the multiple distinct lncRNAs and the gut microbiota, it is difficult to study all potential pairwise regulatory interactions between lncRNAs and the gut microbiome.…”

LINC00491 Facilitates Tumor Progression of Lung Adenocarcinoma via Wnt/β-Catenin-Signaling Pathway by Regulating MTSS1 Ubiquitination

“…Numerous studies indicate that specific RNA-dependent protein interactions play a key role in tumor pathogenesis. For instance, lncRNA STEAP3-AS1 prevents the degradation of STEAP3 mRNA by mediating its m6A modification, which activates Wnt signaling to promote CRC progression [ 16 ]. Although various lncRNAs have been extensively studied in LUAD, discovering specific RNA-dependent protein interactions would further provide novel strategies for molecular therapy.…”