Mechanisms of myeloid-derived suppressor cell-mediated immunosuppression in colorectal cancer and related therapies

Severe immunosuppression is a hallmark of colorectal cancer(CRC).Myeloid-derived suppressor cells(MDSCs),one of the most abundant components of the tumor stroma,play an important role in the invasion,metastasis,and immune escape of CRC.MDSCs create an immunosuppressive microenvironment by inhibiting the proliferation and activation of immunoreactive cells,including T and natural killer cells,as well as by inducing the proliferation of immunosuppressive cells,such as regulatory T cells and tumor-associated macrophages,which,in turn,promote the growth of cancer cells.Thus,MDSCs are key contributors to the emergence of an immunosup-pressive microenvironment in CRC and play an important role in the breakdown of antitumor immunity.In this narrative review,we explore the mechanisms through which MDSCs contribute to the immunosuppressive microenvironment,the current therapeutic approaches and technologies targeting MDSCs,and the therapeutic potential of modulating MDSCs in CRC treatment.This study provides ideas and methods to enhance survival rates in patients with CRC.

Qinggan Huoxue Recipe suppresses epithelial-tomesenchymal transition in alcoholic liver fibrosis through TGF-β1/Smad signaling pathway

AIM: To investigate the mechanism by which Qinggan Huoxue Recipe (QGHXR) inhibits epithelial-to-mesenchymal transition (EMT) in rats with alcoholic liver fibrosis (ALF).METHODS: A total of 75 male SD rats were used to induce ALF. Serum biochemical indicators, including alanine aminotransferase, aspartate aminotransferase, laminin and hyaluronidase, were measured. Liver histopathological changes were evaluated using hematoxylin-eosin and Sirius red staining. EMT was examined by analyzing the expression of the epithelial marker E-cadherin and the mesenchymal markers vimentin and fibronectin using RT-PCR and Western blot. The inhibitory effect of QGHXR on EMT markers, as well as its effect on molecules associated with the transforming growth factor (TGF)-β1/Smad signaling pathway, including TGF-β1, Smad3, snail, occludin, ZO-1 and claudin, was also examined.RESULTS: Compared with normal control rats, ALF rats exhibited a decrease in E-cadherin levels (mRNA: ALF 0.16 ± 0.05 vs control 1.00 ± 0.08; protein: ALF 0.09 ± 0.05 vs control 0.70 ± 0.17, P < 0.01) and an increase in vimentin and fibronectin levels (mRNA: 11.43 ± 0.39 vs 1.00 ± 0.19 and 9.91 ± 0.34 vs 1.00 ± 0.44, respectively, P < 0.01; protein: 1.13 ± 0.42 vs 0.09 ± 0.03 and 1.16 ± 0.43 vs 0.09 ± 0.00, respectively, P < 0.01). This indicates that EMT occurred in ALF rats. In addition, the TGF-β1/Smad signaling pathway was activated in ALF rats, as evidenced by the increase in TGF-β1 and snail levels (mRNA: 1.76 ± 0.12 vs 1.00 ± 0.05 and 6.98 ± 0.41 vs 1.00 ± 0.10, respectively, P < 0.01; protein: 1.43 ± 0.05 vs 0.12 ± 0.03 and 1.07 ± 0.29 vs 0.07 ± 0.02, respectively, P < 0.01) and the decrease in Smad3 levels (mRNA: 0.05 ± 0.01 vs 1.00 ± 0.12, P < 0.01; protein: 0.06 ± 0.05 vs 0.89 ± 0.12, P < 0.01). Furthermore, levels of the tight junction markers occludin, ZO-1 and claudin decreased in ALF rats compared with healthy control rats (mRNA: 0.60 ± 0.09 vs 1.00 ± 0.12, 0.11 ± 0.00 vs 1.00 ± 0.12 and 0.60 ± 0.01 vs 1.00 ± 0.08, respectively, P < 0.01; protein: 0.05 ± 0.01 vs 0.87 ± 0.40, 0.09 ± 0.05 vs 0.89 ± 0.18 and 0.04 ± 0.03 vs 0.95 ± 0.21, respectively, P < 0.01). In ALF rats treated with QGHXR, E-cadherin levels increased (mRNA: QGHXR 0.67 ± 0.04 vs ALF model 0.16 ± 0.05, P < 0.01; protein: QGHXR 0.66 ± 0.21 vs ALF model 0.09 ± 0.05, P < 0.01), and vimentin and fibronectin levels decreased (mRNA: 6.57 ± 1.05 vs 11.43 ± 0.39 and 1.45 ± 1.51 vs 9.91 ± 0.34, respectively, P < 0.01; protein: 0.09 ± 0.03 vs 1.13 ± 0.42 and 0.10 ± 0.01 vs 1.16 ± 0.43, respectively, P < 0.01). In addition, QGHXR inhibited the expression of TGF-β1 and increased the expression of Smad3 (mRNA: 1.03 ± 0.11 vs 1.76 ± 0.12, 0.70 ± 0.10 vs 0.05 ± 0.01, respectively, P < 0.05 and P < 0.01; protein: 0.12 ± 0.03 vs 1.43 ± 0.05 and 0.88 ± 0.20 vs 0.06 ± 0.05, respectively, P < 0.01). QGHXR treatment also reduced the levels of the EMT-inducing transcription factor snail (mRNA: 2.28 ± 0.33 vs 6.98 ± 0.41, P < 0.01; protein: 0.08 ± 0.02 vs 1.07 ± 0.29, P < 0.01) and increased the occludin, ZO-1 and claudin levels (mRNA: 0.73 ± 0.05 vs 0.60 ± 0.09, 0.57 ± 0.04 vs 0.11 ± 0.00 and 0.68 ± 0.03 vs 0.60 ± 0.01, respectively, P < 0.01, P < 0.01 and P < 0.05; protein: 0.92 ± 0.50 vs 0.05 ± 0.01, 0.94 ± 0.22 vs 0.09 ± 0.05 and 0.94 ± 0.29 vs 0.04 ± 0.03, respectively, P < 0.01). The effects of QGR and HXR on the TGF-β1/Smad signaling pathway were similar to that of QGHXR; however, the QGR- and HXR-induced changes in vimentin mRNA levels, the QGR-induced changes in fibronectin mRNA levels and the HXR-induced changes in snail and TGF-β1 mRNA levels were not significant.CONCLUSION: Qinggan Huoxue Recipe inhibits EMT in ALF rats by modulating the TGF-β1/Smad signaling pathway, suggesting that the mechanism underlying the amelioration of ALF induced by QGHXR is associated with this pathway.

Drug resistance and new therapies in colorectal cancer

Colorectal cancer(CRC) is often diagnosed at an advanced stage when tumor cell dissemination has taken place. Chemo-and targeted therapies provide only a limited increase of overall survival for these patients. The major reason for clinical outcome finds its origin in therapy resistance. Escape mechanisms to both chemo-and targeted therapy remain the main culprits. Here, we evaluate major resistant mechanisms and elaborate on potential new therapies. Amongst promising therapies is α-amanitin antibodydrug conjugate targeting hemizygous p53 loss. It becomes clear that a dynamic interaction with the tumor microenvironment exists and that this dictates therapeutic outcome. In addition, CRC displays a limited response to checkpoint inhibitors, as only a minority of patients with microsatellite instable high tumors is susceptible. In this review, we highlight new developments with clinical potentials to augment responses to checkpoint inhibitors.

CircRNA_0084927 promotes colorectal cancer progression by regulating miRNA-20b-3p/glutathione S-transferase mu 5 axis

BACKGROUND Colorectal cancer(CRC)is the third most common cancer and the second most common cause of cancer-related death worldwide.The 5-year survival rate of patients with early-stage CRC could reach 90%,but it is very low in patients with advanced-stage CRC.Recent studies have shown that circular RNAs play important roles in regulating the migration and invasion of CRC cells.AIM To elucidate the role of circRNA_0084927(circ_0084927)in the migration and invasion of CRC cells and its underlying mechanism.METHODS Clinical tissue samples and cells were collected,and the expression of circ_0084927 was detected by quantitative polymerase chain reaction(qPCR).The diagnostic performance of circ_0084927 was assessed by receiver operating characteristic curve analysis.The role of circ_0084927 in CRC cell proliferation,migration,and invasion was determined using cell counting kit-8 assay,wound healing assay,and transwell assay,respectively.The regulatory relationship among circ_0084927,miRNA-20b-3p(miR-20b-3p),and glutathione S-transferase mu 5(GSTM5)was identified using databases,luciferase reporter assay,qPCR,and Western blot analysis.AKT-mTOR signaling was also verified after circ_0084927 knockdown or miR-20b-3p mimic treatment.RESULTS The expression of circ_0084927 was significantly increased in CRC tissues and cells,and it was higher in advanced-stage CRC compared with early-stage CRC.The area under the curve(AUC)of circ_0084927 was 0.806[95%confidence interval(CI):0.683-0.896].In addition,the AUC was 0.874(95%CI:0.738-0.956)in patients with advanced-stage CRC and 0.713(95%CI:0.555-0.840)in those with early-stage CRC.Knockdown of circ_0084927 inhibited the migration and invasion of HCT116 cells.Moreover,circ_0084927 was found to act as a sponge of miR-20b-3p.MiR-20b-3p activation reduced the circ_0084927 level,whereas miR-20b-3p inhibition increased the circ_0084927 level.But the effect was not found after circ_0084927 mutation.In addition,miR-20b-3p expression in CRC patients was also reduced and negatively correlated with circ_0084927 expression.The function of circ_0084927 in HCT116 cells with circ_0084927 knockdown was rescued by miR-20b-3p.Moreover,GSTM5 expression was significantly decreased after overexpressing miR-20b-3p or inhibiting circ_0084927,but its expression was rescued when circ_0084927 and miR-20b-3p were both inhibited.Finally,AKTmTOR signaling was markedly regulated by circ_0084927 and miR-20b-3p.CONCLUSION The expression of circ_0084927 is significantly increased in CRC and higher in advanced-stage CRC than in early-stage CRC.Moreover,circ_0084927 potentially regulates CRC cell migration and invasion via the miR-20b-3p/GSTM5/AKT/mTOR pathway.

RNA-Seq profiling of circular RNAs in human colorectal cancer 5-fluorouracil resistance and potential biomarkers

BACKGROUND Colorectal cancer(CRC)is a commonly diagnosed cancer of the digestive system worldwide.Although chemotherapeutic agents and targeted therapeutic drugs are currently available for CRC treatment,drug resistance is a problem that cannot be ignored and needs to be solved.AIM To explore the relationship between circular RNA(circRNA)and CRC drug resistance.circRNA plays a key role in the occurrence and development of cancers,but its function in the process of drug resistance has not been widely revealed.METHODS To explore the role of circRNA in 5-fluorouracil(5-Fu)resistance,we performed the circRNA expression profile in two CRC cell lines and their homologous 5-Fu resistant cells by high-throughput sequencing.RESULTS We validated the differentially expressed circRNAs in other two paired CRC cells,confirmed that circ_0002813 and circ_0000236 could have a potential competitive endogenous RNA mechanism and be involved in the formation of 5-Fu resistance.And we combined the sequencing results of mRNA to construct the regulatory network of circRNA-miRNA-mRNA.CONCLUSION Our study revealed that circ_0002813 and circ_0000236 may as the biomarkers to predict the occurrence of 5-Fu resistance in CRC.

Macrophages play a role in inflammatory transformation of colorectal cancer

Colorectal cancer(CRC)is one of the most common and fatal cancers worldwide,and it is also a typical inflammatory cancer.The function of macrophages is very important in the tissue immune microenvironment during inflammatory and carcinogenic transformation.Here,we evaluated the function and mechanism of macrophages in intestinal physiology and in different pathological stages.Furthermore,the role of macrophages in the immune microenvironment of CRC and the influence of the intestinal population and hypoxic environment on macrophage function are summarized.In addition,in the era of tumor immunotherapy,CRC currently has a limited response rate to immune checkpoint inhibitors,and we summarize potential therapeutic strategies for targeting tumorassociated macrophages.