Hsa_circ_0136666 promotes the proliferation and invasion of colorectal cancer through miR-136/SH2B1 axis

Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. Currently, an increasing evidence showed that circular RNAs (circRNAs) play important roles in tumor progression. However, the effects and underlying mechanisms of circRNAs in CRC progression remain unclear. In the present study, through circRNA high-throughput sequencing and quantitative real-time polymerase chain reaction, we identified that hsa_circ_0136666 was significantly overexpressed in CRC tissues and cell lines. High hsa_circ_0136666 expression was associated with poor overall survival of patients with CRC. In vitro function assays showed that hsa_circ_0136666 inhibition suppressed CRC cell proliferation, migration, invasion, and arrested CRC cells in the G0/G1 phase. Furthermore, we showed that hsa_circ_0136666 inhibition reduced CRC cell growth in vivo. Mechanistically, we revealed that hsa_circ_0136666 could increase SH2B1 expression via competitively binding miR-136 in CRC cells. In addition, SH2B1 overexpression could reverse the effects of hsa_circ_0136666 inhibition on CRC cell progression. In conclusion, our data suggested that hsa_circ_0136666 could promote CRC cell progression via the miR-136/SH2B1 axis, elucidating a novel approach to improve the effectiveness of CRC treatment.     

PD-1/PD-L1-dependent immune response in colorectal cancer

Colorectal cancer (CRC) is still considered as the third most frequent cancer in the world. Microsatellite instability (MSI), inflammation, and microRNAs have been demonstrated as the main contributing factors in CRC. Subtype 1 CRC is defined by NK cells infiltration, induction of Th1 lymphocyte and cytotoxic T cell responses as well as upregulation of immune checkpoint proteins including programmed cell death-1 (PD-1). Based on the diverse features of CRC, such as the stage and localization of the tumor, several treatment approaches are available. However, the efficiency of these treatments may be decreased due to the development of diverse resistance mechanisms. It has been proven that monoclonal antibodies (mAbs) can increase the effectiveness of CRC treatments. Nowadays, several mAbs including nivolumab and pembrolizumab have been approved for the treatment of CRC. Immune checkpoint receptors including PD-1 can be inhibited by these antibodies. Combination therapy gives an opportunity for advanced treatment for CRC patients. In this review, an update has been provided on the molecular mechanisms involved in MSI colorectal cancer immune microenvironment by focusing on PD-ligand 1 (PD-L1) and treatment of patients with advanced immunotherapy, which were examined in the different clinical trial phases. Considering induced expression of PD-L1 by conventional chemotherapeutics, we have summarized the role of PD-L1 in CRC, the chemotherapy effects on the PD-1/PD-L1 axis and novel combined approaches to enhance immunotherapy of CRC by focusing on PD-L1.     

Histone deacetylase 2 knockout suppresses immune escape of triple-negative breast cancer cells via downregulating PD-L1 expression

The PD-L1 overexpression is an important event of immune escape and metastasis in triple-negative breast cancer (TNBC), but the molecular mechanism remains to be determined. Interferon gamma (IFNγ) represents a major driving force behind PD-L1 expression in tumor microenvironment, and histone deacetylase 2 (HDAC2) is required for IFN signaling. Here, we investigated the regulation of HDAC2 on the IFNγ-induced PD-L1 expression in TNBC cells. We found the HDAC2 and PD-L1 expression in TNBC was significantly higher than that in non-TNBC, and HDAC2 was positively correlated with PD-L1 expression. HDAC2 promoted PD-L1 induction by upregulating the phosphorylation of JAK1, JAK2, and STAT1, as well as the translocation of STAT1 to the nucleus and the recruitment of STAT1 to the PD-L1 promoter. Meanwhile, HDAC2 was recruited to the PD-L1 promoter by STAT1, and HDAC2 knockout compromised IFNγ-induced upregulation of H3K27, H3K9 acetylation, and the BRD4 recruitment in PD-L1 promoter. In addition, significant inhibition of proliferation, colony formation, migration, and cell cycle of TNBC cells were observed following knockout of HDAC2 in vitro. Furthermore, HDAC2 knockout reduced IFNγ-induced PD-L1 expression, lymphocyte infiltration, and retarded tumor growth and metastasis in the breast cancer mouse models. This study may provide evidence that HDAC2 promotes IFNγ-induced PD-L1 expression, suggesting a way for enhanced antitumor immunity when targeting the HDAC2 in TNBC.Subject terms: Breast cancer, Immune evasion     

Exosomes-delivered PD-L1 siRNA and CTLA-4 siRNA protect against growth and tumor immune escape in colorectal cancer

ObjectiveThis study aims to dissect impacts of exosomes-delivered PD-L1 and CTLA-4 siRNAs on colorectal cancer (CRC) progression and immune responses.MethodsExosomes containing PD-L1 siRNA and CTLA-4 siRNA were prepared and utilized to treat CRC cells to evaluate their effects. A tumor-bearing mouse model was established for verification.ResultsExosomes containing PD-L1 siRNA and CTLA-4 siRNA repressed malignant features of CRC cells and restrained tumor growth and activated tumor immune responses in vivo. Co-culture of CRC cells treated with exosomes containing PD-L1 siRNA and CTLA-4 siRNA with human CD8⁺ T cells increased the percentage of CD8⁺ T cells, decreased the apoptotic rate of CD8⁺ T cells, elevated IL-2, IFN-γ, and TNF-α expression in cell supernatants, reduced adherent density of CRC cells, augmented the positive rate of CRC cells, and subdued tumor immune escape.ConclusionExosomes containing PD-L1 siRNA and CTLA-4 siRNA suppressed CRC progression and enhanced tumor immune responses.     

CircRNA VIM silence synergizes with sevoflurane to inhibit immune escape and multiple oncogenic activities of esophageal cancer by simultaneously regulating miR-124/PD-L1 axis

Background

Circular RNA of vimentin (circ-VIM) is a predictor for poor prognosis of acute myeloid leukemia, but we had little information on its function in esophageal cancer (EC). Here we examined the effects of circ-VIM together with sevoflurane on immune escape and multiple oncogenic activities of EC.

Methods

Bioinformatic tools, luciferase assay, and RNA immunoprecipitation were used to examine regulations between circ-VIM, miR-124-3p (miR-124), and PD-L1. CCK-8, wound healing, and Transwell assays were used to measure cell proliferation, migration, and invasion, respectively. The impacts of EC cells on cytotoxicity, proliferation, and apoptosis of CD8⁺ T cells were examined using LDH assay, CFSE staining, and Annexin V/PI staining, respectively. The in vivo tumorigenesis and lung metastases were assessed using xenograft model and tail vein injection of EC cells.

Results

Significant upregulation of circ-VIM and PD-L1 and downregulation of miR-124 were detected in EC tissues or cells. Circ-VIM sponged miR-124 and released its suppression on the downstream target PD-L1. Sevoflurane, independent of circ-VIM, also upregulated miR-124 to lower PD-L1 expression. By modulating miR-124/PD-L1 axis, silencing circ-VIM and applying sevoflurane both inhibited immune escape and multiple oncogenic activities of EC in vitro, and suppressed xenograft growth and lung metastases in vivo. The inactivation of Ras/ERK signaling pathway was involved in suppression of malignant phenotypes by silencing circ-VIM and sevoflurane treatment.

Conclusions

Silencing circ-VIM and applying sevoflurane, by separately regulating miR-124/PD-L1 axis, presented synergistic effects in inhibiting immune escape and multiple malignant phenotypes of EC cells.

Graphical abstract

     

Hsa_circ_0003098 promotes bladder cancer progression via miR-377-5p/ACAT2 axis

Accumulating evidence has proven that circRNAs play vital roles in tumor progression. Nevertheless, the mechanisms underlying circRNAs in bladder cancer (BCa) remain largely unknown. The purpose of this study was to identify the role and investigate the potential molecular mechanisms of hsa_circ_0003098 in BCa. We confirmed that hsa_circ_0003098 expression was significantly upregulated in BCa tissues, of which expression was remarkably associated with poor prognosis. Functionally, overexpression of hsa_circ_0003098 promoted BCa cell proliferation, migration, and invasion in vitro as well as tumor growth in vivo. Mechanistically, hsa_circ_0003098 promoted upregulation of ACAT2 expression and induced cholesteryl ester accumulation via acting as a sponge for miR-377-5p. Thus, hsa_circ_0003098 plays an oncogenic role in BCa and may serve as a potential biomarker and therapeutic target for BCa.     

PD-1/PD-L1 immune checkpoint: Potential target for cancer therapy

Recent studies show that cancer cells are sometimes able to evade the host immunity in the tumor microenvironment. Cancer cells can express high levels of immune inhibitory signaling proteins. One of the most critical checkpoint pathways in this system is a tumor-induced immune suppression (immune checkpoint) mediated by the programmed cell death protein 1 (PD-1) and its ligand, programmed death ligand 1 (PD-L1). PD-1 is highly expressed by activated T cells, B cells, dendritic cells, and natural killer cells, whereas PD-L1 is expressed on several types of tumor cells. Many studies have shown that blocking the interaction between PD-1 and PD-L1 enhances the T-cell response and mediates antitumor activity. In this review, we highlight a brief overview of the molecular and biochemical events that are regulated by the PD-1 and PD-L1 interaction in various cancers.     

LncRNA SNHG1 regulates immune escape of renal cell carcinoma by targeting miR-129-3p to activate STAT3 and PD-L1

Immune escape of renal cell carcinoma (RCC) impacts patient survival. However, the molecular mechanism of long noncoding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) in RCC immune escape remains unclear. Quantitative real-time PCR and western blotting results revealed that the expression of lncRNA SNHG1 and STAT3 were upregulated in RCC tissues and cells and that the expression of miR-129-3p was downregulated. Enzyme-linked immunosorbent assay results revealed the increased levels of immune-related factors (interferon-γ, tumour necrosis factor α, and interleukin-2) in RCC tissues. SNHG1 knockdown or miR-129-3p overexpression inhibited the proliferation and invasion of A498 and 786-O cells, while the proliferation and cytotoxicity of CD8⁺ T cells increased, which promoted the secretion of immune-related factors. STAT3 overexpression decreased the protective effect of miR-129-3p overexpression on RCC cell immune escape. In addition, miR-129-3p knockdown and STAT3 overexpression decreased the protective effect of lncRNA SNHG1 knockdown on RCC cell immune escape. In addition, PD-L1 expression was downregulated after lncRNA SNHG1 knockdown but upregulated after miR-129-3p knockdown and STAT3 overexpression. Dual-luciferase assays showed that lncRNA SNHG1 targets miR-129-3p, and miR-129-3p targets STAT3. RNA pull-down and RNA immunoprecipitation assays verified the regulatory relationship between SNHG1 and STAT3. In vivo, shSNHG1 prolonged the overall survival of RCC tumour model mice and inhibited RCC tumour growth and immune escape but increased CD8⁺ T cell infiltration in mice. Our findings provide an experimental basis for elucidating the molecular mechanisms of immune escape by RCC and reveal a novel target to treat this disease.     

Hsa_circ_0092276 promotes doxorubicin resistance in breast cancer cells by regulating autophagy via miR-348/ATG7 axis

Previous study has confirmed that hsa_circ_0092276 is highly expressed in doxorubicin (DOX)-resistant breast cancer cells, indicating that hsa_circ_0092276 may be involved in regulating the chemotherapy resistance of breast cancer. Here we attempted to investigate the biological role of hsa_circ_0092276 in breast cancer. We first constructed DOX-resistant breast cancer cells (MCF-7/DOX and MDA-MB-468/DOX). The 50% inhibiting concentration of MCF-7/DOX and MDA-MB-468/DOX cells was significantly higher than that of their parental breast cancer cells, MCF-7 and MDA-MB-46. MCF-7/DOX and MDA-MB-468/DOX cells also exhibited an up-regulation of drug resistance-related protein MDR1. Compared with MCF-7 and MDA-MB-46 cells, hsa_circ_0092276 was highly expressed in MCF-7/DOX and MDA-MB-468/DOX cells. Hsa_circ_0092276 overexpression enhanced proliferation and the expression of LC3-II/LC3-I and Beclin-1, and repressed apoptosis of breast cancer cells. The effect of hsa_circ_0092276 up-regulation on breast cancer cells was abolished by 3-methyladenine (autophagy inhibitor). Hsa_circ_0092276 modulated autophagy-related gene 7 (ATG7) expression via sponging miR-384. Hsa_circ_0092276 up-regulation promoted autophagy and proliferation, and repressed apoptosis of breast cancer cells, which was abolished by miR-384 overexpression or ATG7 knockdown. In addition, LV-circ_0092276 transfected MCF-7 cell transplantation promoted autophagy and tumor growth of breast cancer in mice. In conclusion, our data demonstrate that hsa_circ_0092276 promotes autophagy and DOX resistance in breast cancer by regulating miR-348/ATG7 axis. Thus, this article highlights a novel competing endogenous RNA circuitry involved in DOX resistance in breast cancer.     

CLCA1 suppresses colorectal cancer aggressiveness via inhibition of the Wnt/beta-catenin signaling pathway

Background

Chloride channel accessory 1 (CLCA1) belongs to the calcium-sensitive chloride conductance protein family, which is mainly expressed in the colon, small intestine and appendix. This study was conducted to investigate the functions and mechanisms of CLCA1 in colorectal cancer (CRC).

Methods

The CLCA1 protein expression level in CRC patients was evaluated by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), and western blotting analysis. Using CRISPR/Cas9 technology, CLCA1-upregulated (CLCA1-ACT) and CLCA1-knockout cells (CLCA1-KO), as well as their respective negative controls (CLCA1-ACT-NC and CLCA1-KO-NC), were constructed from the SW620 cell line. Cell growth and metastatic ability were assessed both in vitro and in vivo. The association of CLCA1 with epithelial-mesenchymal transition (EMT) and other signaling pathways was determined by western blotting assays.

Results

The expression level of CLCA1 in CRC tissues was significantly decreased compared with that in adjacent normal tissue (P< 0.05). Meanwhile, the serum concentration of CLCA1 in CRC patients was also significantly lower when compared with that of healthy controls (1.48?±?1.06 ng/mL vs 1.06?±?0.73 ng/mL, P?=?0.0018). In addition, CLCA1 serum concentration and mRNA expression level in CRC tissues were inversely correlated with CRC metastasis and tumor stage. Upregulated CLCA1 suppressed CRC growth and metastasis in vitro and in vivo, whereas inhibition of CLCA1 led to the opposite results. Increased expression levels of CLCA1 could repress Wnt signaling and the EMT process in CRC cells.

Conclusions

Our findings suggest that increased expression levels of CLCA1 can suppress CRC aggressiveness. CLCA1 functions as a tumor suppressor possibly via inhibition of the Wnt/beta-catenin signaling pathway and the EMT process.

     

Circ-ERBB2 knockdown sensitized colorectal cancer cells to 5-FU via miR-181a-5p/PTEN/Akt pathway

Colorectal cancer (CRC) is the fourth most deadly cancer worldwide, drug resistance impedes treatment of CRC. It is still urgent to find new molecular targets to improve the sensitivity of chemotherapeutic drugs. In this study, circ-ERBB2 was upregulated in CRC cells. Upregulation of circ-ERBB2 promoted CRC cells proliferation and clone formation, but inhibited apoptosis. We identified miR-181a-5p as circ-ERBB2's target. The effect of miR-181a-5p on CRC cells was contrary to circ-ERBB2, miR-181a-5p downregulation abolished the function of circ-ERBB2 silencing in CRC cells. In addition, phosphatase and tensin homolog (PTEN) was verified as miR-181a-5p's downstream target, circ-ERBB2 activates the Akt pathway and inhibits cell apoptosis through modulating miR-181a-5p/PTEN. Circ-ERBB2 silencing significantly reduced CRC cell resistance to 5-FU. miR-181a-5p downregulation abolished the role of circ-ERBB2 knockdown in CRC cell resistance to 5-FU. In conclusion, upregulation of circ-ERBB2 promoted the malignancy of CRC and reduced CRC cell resistance to 5-FU. Besides, additional mechanism study provided a novel regulatory pathways that circ-ERBB2 knockdown promoted CRC cell sensitivity to 5-FU by regulating miR-181a-5p/PTEN/Akt pathway. This research indicated that circ-ERBB2 may be a valuable biomarker for the diagnosis and treatment of CRC.     

PD-1/PD-L1 pathway: Basic biology and role in cancer immunotherapy

Over the course of past few years, cancer immunotherapy has been accompanied with promising results. However, preliminary investigations with respect to immunotherapy concentrated mostly on targeting the immune checkpoints, nowadays, emerge as the most efficient strategy to raise beneficial antitumor immune responses. Programmed cell death protein 1 (PD-1) plays an important role in subsiding immune responses and promoting self-tolerance through suppressing the activity of T cells and promoting differentiation of regulatory T cells. PD-1 is considered as an immune checkpoint and protects against autoimmune responses through both induction of apoptosis in antigen-specific T cells and inhibiting apoptosis in regulatory T cells. Several clinical trials exerting PD-1 monoclonal antibodies as well as other immune-checkpoint blockades have had prosperous outcomes and opened new horizons in tumor immunotherapy. Nonetheless, a bulk of patients have failed to respond to these newly emerging immune-based approach and the survival rate was not satisfying. Additional strategies, especially combination therapies, has been initiated and been further promising. Attempts to identify novel and well-suited predictive biomarkers are also sensed. In this review, the promotion of cancer immunotherapy targeting PD-1 immunoinhibitory pathway is discussed.