Structural mechanism of LIN28B nucleosome targeting by OCT4.

Pioneer transcription factors are essential for cell fate changes by targeting closed chromatin. OCT4 is a crucial pioneer factor that can induce cell reprogramming. However, the structural basis of how pioneer factors recognize the in vivo nucleosomal DNA targets is unknown. Here, we determine the high-resolution structures of the nucleosome containing human LIN28B DNA and its complexes with the OCT4 DNA binding region. Three OCT4s bind the pre-positioned nucleosome by recognizing non-canonical DNA sequences. Two use their POUS domains while the other uses the POUS-loop-POUHD region; POUHD serves as a wedge to unwrap ∼25 base pair DNA. Our analysis of previous genomic data and determination of the ESRRB-nucleosome-OCT4 structure confirmed the generality of these structural features. Moreover, biochemical studies suggest that multiple OCT4s cooperatively open the H1-condensed nucleosome array containing the LIN28B nucleosome. Thus, our study suggests a mechanism of how OCT4 can target the nucleosome and open closed chromatin.

The LIN28B-IMP1 post-transcriptional regulon has opposing effects on oncogenic signaling in the intestine.

RNA-binding proteins (RBPs) are expressed broadly during both development and malignant transformation, yet their mechanistic roles in epithelial homeostasis or as drivers of tumor initiation and progression are incompletely understood. Here we describe a novel interplay between RBPs LIN28B and IMP1 in intestinal epithelial cells. Ribosome profiling and RNA sequencing identified IMP1 as a principle node for gene expression regulation downstream from LIN28B In vitro and in vivo data demonstrate that epithelial IMP1 loss increases expression of WNT target genes and enhances LIN28B-mediated intestinal tumorigenesis, which was reversed when we overexpressed IMP1 independently in vivo. Furthermore, IMP1 loss in wild-type or LIN28B-overexpressing mice enhances the regenerative response to irradiation. Together, our data provide new evidence for the opposing effects of the LIN28B-IMP1 axis on post-transcriptional regulation of canonical WNT signaling, with implications in intestinal homeostasis, regeneration and tumorigenesis.

TRIM71 reactivation enhances the mitotic and hair cell-forming potential of cochlear supporting cells.

Cochlear hair cell loss is a leading cause of deafness in humans. Neighboring supporting cells have some capacity to regenerate hair cells. However, their regenerative potential sharply declines as supporting cells undergo maturation (postnatal day 5 in mice). We recently reported that reactivation of the RNA-binding protein LIN28B restores the hair cell-regenerative potential of P5 cochlear supporting cells. Here, we identify the LIN28B target Trim71 as a novel and equally potent enhancer of supporting cell plasticity. TRIM71 is a critical regulator of stem cell behavior and cell reprogramming; however, its role in cell regeneration is poorly understood. Employing an organoid-based assay, we show that TRIM71 re-expression increases the mitotic and hair cell-forming potential of P5 cochlear supporting cells by facilitating their de-differentiation into progenitor-like cells. Our mechanistic work indicates that TRIM71's RNA-binding activity is essential for such ability, and our transcriptomic analysis identifies gene modules that are linked to TRIM71 and LIN28B-mediated supporting cell reprogramming. Furthermore, our study uncovers that the TRIM71-LIN28B target Hmga2 is essential for supporting cell self-renewal and hair cell formation.

Developmental changes in the rules for B cell selection.

The autoimmune checkpoint during B cell maturation eliminates self-antigen reactive specificities from the mature B cell repertoire. However, an exception to this rule is illustrated by B-1 cells, an innate-like self-reactive B cell subset that is positively selected into the mature B cell pool in a self-antigen-driven fashion. The mechanisms by which B-1 cells escape central tolerance have puzzled the field for decades. A key clue comes from their restricted developmental window during fetal and neonatal life. Here we use B-1 cells as a prototypic early life derived B cell subset to explore developmental changes in the constraints of B cell selection. We discuss recent advancements in the understanding of the molecular program, centered around the RNA binding protein Lin28b, that licenses self-reactive B-1 cell output during ontogeny. Finally, we speculate on the possible link between the unique rules of early life B cell tolerance and the establishment of B cell - microbial mutualism to propose an integrated model for how developmental and environmental cues come together to create a protective layer of B cell memory involved in neonatal immune imprinting.

Exosomes derived from cancer-associated fibroblasts promote tumorigenesis, metastasis and chemoresistance of colorectal cancer by upregulating circ_0067557 to target Lin28.

BACKGROUND: Cancer associated fibroblasts (CAFs) can remodel tumor microenvironment by secreting exosomes. This study aimed to investigate the role of exosomes derived from cancer-associated fibroblasts in colorectal cancer (CRC) progression. METHODS: Circular RNA (circRNA) array was used to identify differentially expressed circRNAs in exosomes from normal fibroblasts (NFs) and CAFs, and confirmed one differentially expressed circRNA circ_0067557 by real-time PCR. The effect of circ_0067557 on proliferation, metastasis, chemoresistance and apoptosis was verified by wound heal, tranwell, CCK8, sphere-forming and flow cytometry assay. RESULTS: Circ_0067557 expression in exosomes from CAFs was higher than those from NFs. CAF-derived exosomes promoted the proliferation, migration, invasion and chemoresistance of CRC cells while suppressed apoptosis. Silencing of circ_0067557 inhibited malignant phenotypes of CRC cells by targeting Lin28A and Lin28B. Moreover, CAF-derived exosomes enhanced the growth of CRC xenograft tumors. CONCLUSION: Circ_0067557/Lin28A and Lin28B signal axis may be a potential therapy target for CRC.

Targeting Lin28 axis enhances glypican-3-CAR T cell efficacy against hepatic tumor initiating cell population.

Overexpression of Lin28 is detected in various cancers with involvement in the self-renewal process and cancer stem cell generation. In the present study, we evaluated how the Lin28 axis plays an immune-protective role for tumor-initiating cancer cells in hepatocellular carcinoma (HCC). Our result using HCC patient samples showed a positive correlation between indoleamine 2,3-dioxygenase-1 (IDO1), a kynurenine-producing enzyme with effects on tumor immune escape, and Lin28B. Using in silico prediction, we identified a Sox2/Oct4 transcriptional motif acting as an enhancer for IDO1. Knockdown of Lin28B reduced Sox2/Oct4 and downregulated IDO1 in tumor-initiating hepatic cancer cells. We further observed that inhibition of Lin28 by a small-molecule inhibitor (C1632) suppressed IDO1 expression. Suppression of IDO1 resulted in a decline in kynurenine production from tumor-initiating cells. Inhibition of the Lin28 axis also impaired PD-L1 expression in HCC cells. Consequently, modulating Lin28B enhanced in vitro cytotoxicity of glypican-3 (GPC3)-chimeric antigen receptor (CAR) T and NK cells. Next, we observed that GPC3-CAR T cell treatment together with C1632 in a HCC xenograft mouse model led to enhanced anti-tumor activity. In conclusion, our results suggest that inhibition of Lin28B reduces IDO1 and PD-L1 expression and enhances immunotherapeutic potential of GPC3-CART cells against HCC.

Alisol A inhibits the circ_0001831/miR-346/LIN28B pathway to ameliorate high glucose-induced injury of human renal mesangial cells.

BACKGROUND: Alisol A can ameliorate glucose metabolism disorders, however, there is no data regarding its role in diabetic nephropathy (DN). The present work evaluates the role of Alisol A in DN and the underlying mechanism. METHODS: RNA expression of circ_0001831, miR-346, and lin-28 homolog B (LIN28B) was detected by qRT-PCR. Cell viability and proliferation were investigated by MTT assay and EdU assay, respectively. The inflammatory cytokines were examined by ELISAs. Oxidative stress was evaluated by the commercial kits. Protein expression was detected by western blotting. The interactions among circ_0001831, miR-346, and LIN28B were identified by dual-luciferase reporter assay and RIP assay. DN mouse model assay was used to analyse the effect of Alisol A on renal injury of diabetic mice. RESULTS: HG treatment promoted HRMC proliferation, fibrosis, inflammation, and oxidative stress; however, these effects were reversed after Alisol A treatment. Alisol A treatment ameliorated STZ-induced renal injury of diabetic mice. Additionally, circ_0001831 or LIN28B overexpression or miR-346 downregulation relieved Alisol A-induced effects under HG conditions. Mechanistically, circ_0001831 acted as a miR-346 sponge, and LIN28B was identified as a target gene of miR-346. Further, the regulation of circ_0001831 in HG-induced HRMC dysfunction involved LIN28B. CONCLUSION: Alisol A ameliorated HG-induced HRMC fibrosis, inflammation, and oxidative stress and STZ-induced renal injury of diabetic mice by regulating the circ_0001831/miR-346/LIN28B pathway.

A Multi-Omics Approach Reveals Enrichment in Metabolites Involved in the Regulation of the Glutathione Pathway in LIN28B-Dependent Cancer Cells.

The RNA-binding protein LIN28B, identified as an independent risk factor in high-risk neuroblastoma patients, is implicated in adverse treatment outcomes linked to metastasis and chemoresistance. Despite its clinical significance, the impact of LIN28B on neuroblastoma cell metabolism remains unexplored. This study employs a multi-omics approach, integrating transcriptome and metabolome data, to elucidate the global metabolic program associated with varying LIN28B expression levels over time. Our findings reveal that escalating LIN28B expression induces a significant metabolic rewiring in neuroblastoma cells. Specifically, LIN28B prompts a time-dependent increase in the release rate of metabolites related to the glutathione and aminoacyl-tRNA biosynthetic pathways, concomitant with a reduction in glucose uptake. These results underscore the pivotal role of LIN28B in governing neuroblastoma cell metabolism and suggest a potential disruption in the redox balance of LIN28B-bearing cells. This study offers valuable insights into the molecular mechanisms underlying LIN28B-associated adverse outcomes in neuroblastoma, paving the way for targeted therapeutic interventions.

EGCG Disrupts the LIN28B/Let-7 Interaction and Reduces Neuroblastoma Aggressiveness.

Neuroblastoma (NB) is the most commonly diagnosed extracranial solid tumor in children, accounting for 15% of all childhood cancer deaths. Although the 5-year survival rate of patients with a high-risk disease has increased in recent decades, NB remains a challenge in pediatric oncology, and the identification of novel potential therapeutic targets and agents is an urgent clinical need. The RNA-binding protein LIN28B has been identified as an oncogene in NB and is associated with a poor prognosis. Given that LIN28B acts by negatively regulating the biogenesis of the tumor suppressor let-7 miRNAs, we reasoned that selective interference with the LIN28B/let-7 miRNA interaction would increase let-7 miRNA levels, ultimately leading to reduced NB aggressiveness. Here, we selected (-)-epigallocatechin 3-gallate (EGCG) out of 4959 molecules screened as the molecule with the best inhibitory activity on LIN28B/let-7 miRNA interaction and showed that treatment with PLC/PLGA-PEG nanoparticles containing EGCG (EGCG-NPs) led to an increase in mature let-7 miRNAs and a consequent inhibition of NB cell growth. In addition, EGCG-NP pretreatment reduced the tumorigenic potential of NB cells in vivo. These experiments suggest that the LIN28B/let-7 miRNA axis is a good therapeutic target in NB and that EGCG, which can interfere with this interaction, deserves further preclinical evaluation.

Innate and adaptive γδ T cells: How, when, and why.

γδ T cells comprise the third cell lineage of lymphocytes that use, like αß T cells and B cells, V(D)J gene rearrangement with the potential to generate a highly diverse T cell receptor (TCR) repertoire. There is no obvious conservation of γδ T cell subsets (based on TCR repertoire and/or function) between mice and human, leading to the notion that human and mouse γδ T cells are highly different. In this review, we focus on human γδ T cells, building on recent studies using high-throughput sequencing to analyze the TCR repertoire in various settings. We make then the comparison with mouse γδ T cell subsets highlighting the similarities and differences and describe the remarkable changes during lifespan of innate and adaptive γδ T cells. Finally, we propose mechanisms contributing to the generation of innate versus adaptive γδ T cells. We conclude that key elements related to the generation of the γδ TCR repertoire and γδ T cell activation/development are conserved between human and mice, highlighting the similarities between these two species.

Progress on the role of LIN28A/B in tumor development and progression.

LIN28A and its homolog LIN28B are highly conserved RNA-binding proteins that play important roles in early embryonic development, somatic cell reprogramming, metabolism and tumorigenesis. LIN28A/B are highly expressed in a variety of malignant tumors such as breast cancer. They play important roles in the initiation, maintenance, and metastasis of tumors and are associated with poor prognosis. Previous studies have shown that the main regulatory mechanisms of LIN28A/B include let-7s dependent ways and let-7s independent ways, such as directly targeting mRNA. In this review, we summarize the function and molecular regulatory mechanisms of LIN28A/B in malignant tumors such as liver cancer, breast cancer and colorectal cancer, in order to provide references for further exploring the function and mechanism of LIN28A/B and their possible roles in clinical applications.

LIN28 expression and function in medulloblastoma.

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Current treatment modalities are not completely effective and can lead to severe neurological and cognitive adverse effects. In addition to urgently needing better treatment approaches, new diagnostic and prognostic biomarkers are required to improve the therapy outcomes of MB patients. The RNA-binding proteins, LIN28A and LIN28B, are known to regulate invasive phenotypes in many different cancer types. However, the expression and function of these proteins in MB had not been studied to date. This study identified the expression of LIN28A and LIN28B in MB patient samples and cell lines and assessed the effect of LIN28 inhibition on MB cell growth, metabolism and stemness. LIN28B expression was significantly upregulated in MB tissues compared to normal brain tissues. This upregulation, which was not observed in other brain tumors, was specific for the aggressive MB subgroups and correlated with patient survival and metastasis rates. Functionally, pharmacological inhibition of LIN28 activity concentration-dependently reduced LIN28B expression, as well as the growth of D283 MB cells. While LIN28 inhibition did not affect the levels of intracellular ATP, it reduced the expression of the stemness marker CD133 in D283 cells and the sphere formation of CHLA-01R cells. LIN28B, which is highly expressed in the human cerebellum during the first few months after birth, subsequently decreased with age. The results of this study highlight the potential of LIN28B as a diagnostic and prognostic marker for MB and open the possibility to utilize LIN28 as a pharmacological target to suppress MB cell growth and stemness.

MCTS1 enhances the proliferation of laryngeal squamous cell carcinoma via promoting OTUD6B-1 mediated LIN28B deubiquitination.

The aberrant upregulation of MCTS1 Re-Initiation and Release Factor (also known as Malignant T-cell-amplified sequence 1, MCTS1) can promote laryngeal squamous cell carcinoma (LSCC). It might act as a binding partner of multiple proteins. In this study, we further explored the expression of potential interaction between MCTS1 and OTU domain-containing protein 6B (OTUD6B) and its influence on the ubiquitination and degradation of OTUD6B's substrate in LSCC. LSCC cell lines AMC-HN-8 and TU177 were utilized for assessing protein-protein interaction, protein degradation and tumor growth in vitro and in vivo. The results showed that MCTS1 interacts with OUTD6B isoform 1 (OTUD6B-1) in the cell lines. Higher OTUD6B-1 expression is associated with significantly shorter progression-free interval in LSCC patients. OTUD6B positively modulated the expression of cyclin D1, cyclin E1 and c-Myc and LSCC cell proliferation in vitro and in vivo. MCTS1 negatively modulated the degradation of LIN28B in G1/S cells, via enhancing OTUD6B-mediated cleaving of K48-branched ubiquitin chains from LIN28B. OTUD6B or LIN28B shRNA weakened MCTS1 overexpression-induced cyclin D1 and c-Myc protein expression and LSCC cell proliferation. In summary, this study revealed that MCTS1 could enhance LSCC proliferation partially via the OTUD6B-LIN28B axis.

The transposable element-derived transcript of LIN28B has a placental origin and is not specific to tumours.

Transposable elements (TEs) are genetic elements that have evolved as crucial regulators of human development and cancer, functioning as both genes and regulatory elements. When TEs become dysregulated in cancer cells, they can serve as alternate promoters to activate oncogenes, a process known as onco-exaptation. This study aimed to explore the expression and epigenetic regulation of onco-exaptation events in early human developmental tissues. We discovered co-expression of some TEs and oncogenes in human embryonic stem cells and first trimester and term placental tissues. Previous studies identified onco-exaptation events in various cancer types, including an AluJb SINE element-LIN28B interaction in lung cancer cells, and showed that the TE-derived LIN28B transcript is associated with poor patient prognosis in hepatocellular carcinoma. This study further characterized the AluJb-LIN28B transcript and confirmed that its expression is restricted to the placenta. Targeted DNA methylation analysis revealed differential methylation of the two LIN28B promoters between placenta and healthy somatic tissues, indicating that some TE-oncogene interactions are not cancer-specific but arise from the epigenetic reactivation of developmental TE-derived regulatory events. In conclusion, our findings provide evidence that some TE-oncogene interactions are not limited to cancer and may originate from the epigenetic reactivation of TE-derived regulatory events that are involved in early development. These insights broaden our understanding of the role of TEs in gene regulation and suggest the potential importance of targeting TEs in cancer therapy beyond their conventional use as cancer-specific markers.

LOC101929709 promotes gastric cancer progression by aiding LIN28B to stabilize c-MYC mRNA.

BACKGROUND: LIN28B plays a critical role in the Warburg effect. However, its underlying mechanism remains elusive. Recently, it has been reported that LIN28B could collaborate with IGF2BP3, which can bind to m6A-modified c-MYC transcripts. Therefore, this study investigated if LIN28B recognises methylated c-MYC mRNA to promote the Warburg effect in gastric cancer. METHODS: Effects of LIN28B on gastric cancer were confirmed in vitro and in vivo. On the basis of bioinformatics analysis, the association between LIN28B and c-MYC mRNA was shown using RNA immunoprecipitation (RIP) and luciferase reporter assays. The role of m6A was identified by RNA pull-down assays. We further performed RIP-seq to search for long non-coding RNAs (lncRNAs) participating in the LIN28B binding process. Chromatin immunoprecipitation was used to show the impact of c-MYC on transcription of LIN28B and lncRNAs. RESULTS: LIN28B was identified to stabilize c-MYC mRNA by recognizing m6A. Furthermore, the interaction between c-MYC mRNA and LIN28B is speculated to be supported by LOC101929709, which binds to both LIN28B and IGF2BP3. Functional experiments revealed that LOC101929709 promotes the proliferation, migration and glycolysis of gastric cancer. Mechanistically, LOC101929709 enriched in the cytoplasm helps LIN28B stabilize c-MYC mRNA. Moreover, c-MYC promoted the transcription of both LOC101929709 and LIN28B. Additionally, LOC101929709 also activated the PI3K/AKT pathway. CONCLUSIONS: The c-MYC/LOC101929709/LIN28B axis promotes aerobic glycolysis and tumour progression. Thus, LOC101929709 can be a novel potential target for gastric cancer treatment.

Association of the KISS1, LIN28B, VDR and ERα gene polymorphisms with early and fast puberty in Chinese girls.

OBJECTIVES: To explore the association of KISS1, LIN28B, vitamin D receptor (VDR), and estrogen receptor α (ERα) gene polymorphisms and the risk of early with fast puberty (EFP) risk, and with hormone levels in EFP cases, in Chinese girls. METHODS: The analysis was based on the data of 141 girls with EFP and 152 girls without EFP. Clinical features were documented, and all SNP genotyping was conducted using SNaPshot method. Statistical analysis was performed to assess the association of the SNPs with EFP risk, and with hormone levels in EFP cases. RESULTS: There was a significant association between rs7759938-C polymorphism in the LIN28B gene and the risk for EFP in the recessive (TT + CT vs. CC) model (p = 0.040). Remarkably, rs5780218-delA polymorphism in the KISS1 gene and rs2234693-C polymorphism in the ERα gene were significantly associated with peak LH (luteinizing hormone) levels (p = 0.008, 0.045) and peak LH/FSH (follicle-stimulating hormone) ratio (p = 0.007, 0.006). Additionally, on 7 of the 8 variant loci the alleles associated with increased levels of both peak LH levels and peak LH/FSH ratio in EFP cases were also associated with increased CPP risk. CONCLUSIONS: Our findings indicate that rs7759938-C polymorphism in the LIN28B gene might have a protective effect on EFP susceptibility. The most striking findings of this study is that, rs5780218-delA polymorphism in the KISS1 gene and rs2234693-C polymorphism in the ERα gene influenced levels of GnRH-stimulated peak LH and LH/FSH ratio, and in general CPP risk genes might also contributes to the abnormality of hormonal levels in EFP.

LIN28B regulates transcription and potentiates MYCN-induced neuroblastoma through binding to ZNF143 at target gene promotors.

LIN28B is highly expressed in neuroblastoma and promotes tumorigenesis, at least, in part, through inhibition of let-7 microRNA biogenesis. Here, we report that overexpression of either wild-type (WT) LIN28B or a LIN28B mutant that is unable to inhibit let-7 processing increases the penetrance of MYCN-induced neuroblastoma, potentiates the invasion and migration of transformed sympathetic neuroblasts, and drives distant metastases in vivo. Genome-wide chromatin immunoprecipitation coupled with massively parallel DNA sequencing (ChIP-seq) and coimmunoprecipitation experiments show that LIN28B binds active gene promoters in neuroblastoma cells through protein-protein interaction with the sequence-specific zinc-finger transcription factor ZNF143 and activates the expression of downstream targets, including transcription factors forming the adrenergic core regulatory circuitry that controls the malignant cell state in neuroblastoma as well as GSK3B and L1CAM that are involved in neuronal cell adhesion and migration. These findings reveal an unexpected let-7-independent function of LIN28B in transcriptional regulation during neuroblastoma pathogenesis.

Correlation between expression of Lin28B and C-myc in patients with laryngeal squamous cell carcinoma and clinicopathological features and prognosis. / Lin28B和C-mycè›‹ç™½åœ¨å–‰é³žç™Œä¸­çš„è¡¨è¾¾åŠå ¶ä¸Žä¸´åºŠç— ç†ç‰¹å¾å’Œé¢„åŽçš„ç›¸å ³æ€§.

OBJECTIVES: Laryngeal squamous cell carcinoma (LSCC) is a common malignant tumor of head and neck. Screening of target genes for malignant tumor therapy is one of the focuses of cancer research, with proto-oncogene and tumor suppressor gene as the breakthrough. It has become an urgent need to find the target gene related to the treatment and prognosis of LSCC.This study aims to explore the role of Lin28B and C-myc in LSCC by detecting the expressions of these two proteins and analyze the correlation between the expression of Lin28B and C-myc and clinicopathological features and prognosis of LSCC. METHODS: We detected the expression of Lin28B and C-myc proteins in 102 specimens of LSCC and 90 specimens of adjacent tissues by immunochemistry, and analyzed the correlation between Lin28B and C-myc protein expressions in LSCC as well as the correlation between the expressions of the two proteins and the clinicopathological features of LSCC. At the same time, the Kaplan-Meier method was used to analyze the relation between Lin28B and C-myc protein levels with the postoperative survival rate of LSCC patients. RESULTS: The protein levels of Lin28B and C-myc in the LSCC tissnes were significantly higher than those in the adjacent tissues (both P<0.05),and there was a positive correlation between the expression of Lin28B and C-myc in LSCC (r＝0.476, P<0.05). The expression of Lin28B protein was closely related to age, lymph node metastasis, clinical stage, tumor size, and pathological differentiation of LSCC patients (all P<0.05). while the expression of C-myc protein was closely related to lymph node metastasis, clinical stage, tumor size, and pathological differentiation of LSCC patients (all P<0.05). A relevant survival analysis showed that in patients with higher level of Lin28B (P＝0.001) or C-myc protein (P<0.001), the postoperative survival rate was relatively low. CONCLUSIONS: Lin28B and C-myc proteins are highly expressed in LSCC with a positive correlation. Furthermore, they are closely related to lymph node metastasis, clinical stage, tumor size, pathological differentiation and prognosis, suggesting that both Lin28B and C-myc might be involved in the occurrence and development of LSCC.

STAT3-mediated upregulation of LINC00520 contributed to temozolomide chemoresistance in glioblastoma by interacting with RNA-binding protein LIN28B.

A considerable number of glioblastoma (GBM) patients developed drug resistance to Temozolomide (TMZ) during chemotherapy, resulting in therapeutic failure and tumor recurrence. However, the exact mechanism of TMZ chemoresistance in GBM is still poorly clarified. As a novel identified lncRNA, LINC00520 was located on chromosome 14 and overexpressed in multiple human cancers. This study was designed and conducted to investigate the role and underlying mechanism of LINC00520 in GBM chemoresistance to TMZ. The qRT-PCR assay demonstrated that LINC00520 was significantly overexpressed in TMZ-sensitive and/or TMZ-resistant GBM cells (P < 0.001). The silencing of LINC00520 markedly reduced the cell viability, suppressed colony formation, induced cell apoptosis and G1/S phase arrest in TMZ-resistant cells (P < 0.001). In contrast, overexpression of LINC00520 conferred TMZ-resistant phenotype of GBM cells in vitro (P < 0.001). The orthotopic xenograft model was established and the results indicated that the volume of tumor xenografts in vivo was markedly inhibited by TMZ treatment after the silencing of LINC00520 (P < 0.001). Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay revealed a strong affinity of transcription factor STAT3 to the promoter regions of LINC00520, suggesting that STAT3 mediated the aberrant expression of LINC00520 in GBM. Further experiments demonstrated that LINC00520 could interact with RNA-binding protein LIN28B to inhibit autophagy and reduce DNA damage, thereby contributing to TMZ chemoresistance in GBM. These findings suggested that STAT3/LINC00520/LIN28B axis might be a promising target to improve TMZ chemoresistance of GBM.

RNF144A suppresses ovarian cancer stem cell properties and tumor progression through regulation of LIN28B degradation via the ubiquitin-proteasome pathway.

OBJECTIVE: Cancer stem cells (CSCs) are the main driving force of tumorigenesis, metastasis, recurrence, and drug resistance in epithelial ovarian cancer (EOC). The current study aimed to explore the regulatory effects of ring finger protein 144A (RNF144A), an E3 ubiquitin ligase, in the maintenance of CSC properties and tumor development in EOC. METHODS: The expressions of RNF144A in EOC tissue samples and cells were examined. The knockdown or overexpression of a target gene was achieved by transfecting EOC cells with short hairpin RNA or adenoviral vectors. A mouse xenograft model was constructed by inoculating nude mice with EOC cells. Co-immunoprecipitation was used to determine the interaction between RNF144A and LIN28B. RESULTS: Downregulated RNF144A expression was observed in ovarian tumor tissues and EOC cells. Low RNF144A expression was positively associated with poor survival of EOC patients. RNF144A knockdown significantly enhanced sphere formation and upregulated stem cell markers in EOC cells, while RNF144A overexpression prevented EOC cells from acquiring stem cell properties. Also, the upregulation of RNF144A inhibited ovarian tumor growth and aggressiveness in cell culture and mouse xenografts. Further analysis revealed that RNF144A induced LIN28B degradation through ubiquitination in EOC cells. LIN28B upregulation restored the expressions of stem cell pluripotency-associated transcription factors in EOC cells overexpressing RNF144A. CONCLUSION: Taken together, our findings highlight the therapeutic potential of restoring RNF144A expression and thereby suppressing LIN28B-associated oncogenic signaling for EOC treatment. • Ring finger protein 144A (RNF144A) is downregulated in epithelial ovarian cancer (EOC) tissues and cell lines. • The overexpression of RNF144A prevents EOC cells from acquiring stem cell properties and inhibits ovarian tumor growth. • RNF144A induces LIN28B degradation through ubiquitination in EOC cells. • LIN28B upregulation restores the expressions of stem cell pluripotency-associated transcription factors in EOC cells overexpressing RNF144A.