Dataset Information

CircHMGCS1-016 reshapes immune environment by sponging miR-1236-3p to regulate CD73 and GAL-8 expression in intrahepatic cholangiocarcinoma.

ABSTRACT:

Background

Accumulating evidence indicates that circRNAs may serve as essential regulators in the progression of several human cancers, but the function and mechanism of circRNAs in intrahepatic cholangiocarcinoma (ICC) are largely unknown.

Methods

RNA-seq was used to assess differentially expressed circRNAs between 4 ICC and peritumor tissues. Quantitative RT-PCR and in situ hybridization were used to determine the circHMGCS1-016 expression in ICC tissues. The function and mechanism of circHMGCS1-016 were further identified via in vivo experiments. The clinical characteristics and prognostic significance of circHMGCS1-016 were analyzed by a retrospective study. The functions of circHMGCS1-016 were assessed via modifying circRNA expression in ICC cells. Moreover, the molecular mechanisms of circHMGCS1-016 in ICC cells were explored by circRNA precipitation, miRNA immunoprecipitation, SILAC and luciferase reporter assays.

Results

We identified that compared with peritumor tissues, ICC tissues expressed hsa_circ_0008621 (circHMGCS1-016) high by RNA-seq, which was further identified by qRT-PCR and in situ hybridization. Moreover, the expression of circHMGCS1-016 was revealed to be associated with survival and recurrence of ICC patients. By regulating circHMGCS1-016 expression, we found that elevated circHMGCS1-016 promoted ICC development both in vitro and in vivo. By SILAC and circRNA-pull down, we demonstrated that circHMGCS1-016 induced ICC cell invasion and reshaped the tumor immune microenvironment via the miR-1236-3p/CD73 and GAL-8 axis. In ICC tissues, we uncovered that a high level of circHMGCS1-016 was positively associated with CD73 and GAL-8 expression and negatively related to the CD8⁺ T cells infiltration, which was further validated by establishing a humanized mouse tumor model. Importantly, we displayed that ICC patients with high levels of circHMGCS1-016 in tumor tissues benefited less from anti-PD1 treatment compared to those with low levels of circHMGCS1-016.

Conclusions

CircHMGCS1-016 is a forceful contributor in ICC development and immune tolerance via miR-1236-3p/CD73 and GAL-8 axis. CircHMGCS1-016 can be explored as a new potential biomarker and therapeutic target for PD1-resistant ICC.

SUBMITTER: Xu YP

PROVIDER: S-EPMC8442376 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background & aimsIntrahepatic cholangiocarcinoma (iCCA) is a deadly cancer worldwide with an increasing incidence and limited therapeutic options. Therefore, there is an urgent need to open the field to new concepts for identifying clinically relevant therapeutic targets and biomarkers. Here, we explored the role and the clinical relevance of circular RNA (circRNA) circLTBP2 in iCCA.MethodsTransforming growth factor β (TGFβ)-regulated circRNAs were identified by dedicated microarrays in human HuCC-T1 iCCA cell line, and their clinical relevance was evaluated in independent cohorts of patients. Gain and loss of function of circLTBP2 combined with functional tests was performed in vitro and in vivo in mice. RNA pulldown, microRNA sequencing, and RNA immunoprecipitation were performed to explore the sponging activity of circLTBP2.ResultsCircLTBP2 (has_circ_0032603) was identified as a novel TGFβ-induced circRNA in several cholangiocarcinoma cell lines. CircLTBP2 promotes tumour cell proliferation, migration, and resistance to gemcitabine-induced apoptosis in vitro and tumour growth in vivo. Mechanistically, circLTBP2 acts as a competitive RNA regulating notably the activity of the tumour suppressor microRNA miR-338-3p, leading to the overexpression of its pro-metastatic targets. The restoration of miR-338-3p levels in iCCA cells reversed the pro-tumourigenic effects driven by circLTBP2, including the resistance to gemcitabine-induced apoptosis. In addition, circLTBP2 expression predicted a reduced survival, as detected in not only tumour tissues but also serum extracellular vesicles isolated from patients with iCCA.ConclusionsCircLTBP2 is a novel effector of the pro-tumourigenic arm of TGFβ and a clinically relevant biomarker easily detected from liquid biopsies in iCCA.Impact and implicationsIntrahepatic cholangiocarcinoma (iCCA) is an aggressive cancer with limited therapeutic options. Opening the field to new concepts is urgently needed to improve the survival of patients. Here, we evaluated the role and the clinical relevance of circular RNA. We report that TGFβ-induced circLTBP2 contributes to CCA carcinogenesis and may constitute a clinically relevant prognostic biomarker detected in liquid biopsies.