LncRNA HOTTIP regulates TLR4 promoter methylation by recruiting H3K4 methyltransferase MLL1 to affect apoptosis and inflammatory response of fibroblast-like synoviocyte in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, and the role of HOXA transcript at the distal tip (HOTTIP) in its pathogenesis remains underexplored. This study investigates the mechanism by which HOTTIP influences apoptosis and the inflammatory response of fibroblast-like synoviocytes (FLS). An RA mouse model was established, and clinical scores were analyzed. Pathological changes in synovial tissues, bone mineral density (BMD) of the paws, serum tartrate-resistant acid phosphatase (TRAP) activity, and TNF-α and IL-1β levels were assessed. FLS were transfected, and cell proliferation and apoptosis were examined. The RNA-pull-down assay determined HOTTIP's interaction with mixed-lineage leukemia 1 (MLL1), while RNA immunoprecipitation assay measured HOTTIP expression pulled down by MLL1. The levels of MLL1 and toll-like receptor 4 (TLR4) after MLL1 overexpression based on HOTTIP silencing were determined. Chromatin immunoprecipitation (ChIP) was performed with H3K4me3 as an antibody, followed by the evaluation of TLR4 expression. HOTTIP expression was elevated in RA mouse synovial tissues. Inhibition of HOTTIP led to reduced clinical scores, inflammatory infiltration, synovial hyperplasia, TRAP activity, and TNF-α and IL-1β levels, along with increased BMD. In vitro Interference with HOTTIP suppressed RA-FLS apoptosis and inflammation. HOTTIP upregulated TLR4 expression by recruiting MLL1 to facilitate TLR4 promoter methylation. MLL1 overexpression reversed HOTTIP silencing-mediated repression of RA-FLS apoptosis. Activation of H3K4 methylation counteracted HOTTIP knockout, ameliorating the inflammatory response. HOTTIP regulates TLR4 expression by recruiting MLL1, leading to TLR4 promoter methylation, thereby suppressing RA-FLS proliferation and inducing cell apoptosis and inflammatory response in RA.

The HOTTIP (HOXA transcript at the distal tip) lncRNA: Review of oncogenic roles in human

HOXA transcript at the distal tip (HOTTIP) is a 3764 nucleotide long non-coding RNA (lncRNA) encoded from a genomic region in the 5' tip of the HOXA locus. This lncRNA has a role in transmission of signals from higher order chromosomal configuration into chromatin codes. HOTTIP directly binds with the WDR5 protein and recruits the WDR5/MLL complexes across the HOXA locus which leads to H3K4 methylation and activation of the transcription of HOXA genes. This lncRNA has a prominent role in the pathogenesis of almost all kinds of cancers. Apart from a single study in glioma cells, all in vitro studies have emphasized on oncogenic roles of HOTTIP in different malignancies. In vivo studies also showed the effect of HOTTIP silencing in reduction of tumorigenicity in all cancer types except from glioma. Results of clinical studies mostly demonstrated up-regulation of this lncRNA in cancer samples compared with non-malignant tissues of the same origin and correlation between its expression levels and patients' outcome. Taken together, HOTTIP is regarded as an oncogenic lncRNA in almost all kinds of cancers and a putative biomarker and therapeutic target in human malignancies.

Long non-coding RNA HOTTIP enhances IL-6 expression to potentiate immune escape of ovarian cancer cells by upregulating the expression of PD-L1 in neutrophils

Background

Long non-coding RNA (lncRNA) HOXA transcript at the distal tip (HOTTIP), has been demonstrated to be a vital biomarker when evaluating the prognosis of multiple cancers. Nevertheless, the potential function of HOTTIP in ovarian cancer (OC), a prevalent cancer among women worldwide, remains elusive. Hence, the current study aimed to elucidate the functional relevance of HOTTIP in the development of OC.

Methods

Positive expression of PD-L1 and IL-6 was determined using immunohistochemical staining in the collected OC and normal tissues. The correlation of IL-6 and PD-L1 was analyzed using flow cytometry, Western blot analysis as well as Pearson’s correlation coefficient. The interaction among HOTTIP, c-jun and IL-6 was investigated with the use of RIP, ChIP and dual luciferase reporter gene assays. Finally, the effects of HOTTIP on T cell proliferation and infiltration were identified through gain- and loss-of-function studies in vitro and in vivo.

Results

HOTTIP, IL-6 and PD-L1 were all highly expressed in OC tissues. A positive correlation was observed between IL-6 and PD-L1 and that between HOTTIP and IL-6 in OC tissues. HOTTIP was noted to promote the expression of IL-6 by binding to c-jun, which resulted in a promoted PD-L1 expression in neutrophils and immune escape while inhibiting T cell proliferation as well as tumor immunotherapy.

Conclusion

Taken together, our study unveiled that HOTTIP could promote the secretion of IL-6, and consequently up-regulate the expression of PD-L1 in neutrophils, thus inhibiting the activity of T cells and ultimately accelerating immune escape of OC cells. Our study provides a potential therapeutic strategy by targeting HOTTIP in OC.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1394-6) contains supplementary material, which is available to authorized users.

Long noncoding RNA HOTTIP overexpression: A potential prognostic biomarker in prostate cancer

HOXA transcript at the distal tip (HOTTIP) is a long noncoding RNA (lncRNA), which is >200 nucleotides in length. HOTTIP expression has been demonstrated to play a crucial oncogenic role in cancer pathogenesis, and is said to be associated with poor human cancer prognosis. In prostate cancer, HOTTIP has been identified as an oncogene, but its clinicopathologic significance remains unclear. Array-based qRT-PCR was used to investigate lncRNA levels in 10 pairs of prostate cancer tissues and non-neoplastic parenchyma. Tissue microarray (TMA) was constructed using a total of 70 surgically resected prostatic adenocarcinoma tissues obtained from the Korea University Anam Hospital from 2009 to 2013. HOTTIP expression was determined by RNA in situ hybridization(ISH) and was correlated with clinicopathologic features. Increased HOTTIP expression was observed in all available prostate cancer tissue specimens compared with that in paired normal tissue. High HOTTIP expression was positively associated with bad clinicopathologic features, including higher pathologic T stage (p < 0.001), presence of extraprostatic extension (p < 0.001), seminal vesicle invasion (p < 0.001), perineural invasion (p < 0.001), and the tumor involvement of resection margin (p = 0.044). In particular, significantly increased HOTTIP expression was observed in specimens from patients in the high or very high-risk group, according to the 2018 National Comprehensive Cancer Network (NCCN) guidelines (p < 0.001). Also, patients with high HOTTIP expression showed poorer overall survival than those with low expression. In conclusion, we analytically validated the poor prognostic significance of HOTTIP overexpression and its association with bad clinicopathologic features, and present HOTTIP as a potential prognostic biomarker in prostate cancer.

Long non-coding RNA HOXA transcript at the distal tip as a biomarker for gastric cancer

A long non-coding RNA named HOXA transcript at the distal tip (HOTTIP) has been reported to be significantly increased in several cancers, including hepatocellular cancer, pancreatic cancer and lung cancer. However, the clinical value of HOTTIP expression in gastric cancer remains unknown. The present study aimed to investigate HOTTIP expression levels in gastric cancer and to elucidate its clinical significance. Reverse transcription polymerase chain reaction was used to assess the expression level of HOTTIP in gastric cancer cell lines and tissues. In a cohort of 94 patients with gastric cancer, HOTTIP expression was significantly lower in cancer tissues compared with the normal adjacent tissues. In addition, receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value of HOTTIP in gastric cancer, and the area under the ROC curve was 0.767. In conclusion, the results of the present study indicated that HOTTIP may be a predictive biomarker for gastric cancer.