Background It has been well established that circular RNAs (circRNAs) play an important regulatory role during tumor progression. Recent studies have indicated that even though circRNAs generally regulate gene expression through miRNA sponges, they may encode small peptides in tumor pathogenesis. However, it remains largely unexplored whether circRNAs are involved in the tumorigenesis of colon cancer (CC). Methods The expression profiles of circRNAs in CC tissues were assessed by circRNA microarray. Quantitative real-time PCR, RNase R digestion assay and tissue microarray were used to confirm the existence and expression pattern of circPPP1R12A. The subcellular distribution of circPPP1R12A was analyzed by nuclear mass separation assay and fluorescence in situ hybridization (FISH). SDS-PAGE and LC/MS were employed to evaluate the protein-coding ability of circPPP1R12A. CC cells were stably transfected with lentivirus approach, and cell proliferation, migration and invasion, as well as tumorigenesis and metastasis in nude mice were assessed to clarify the functional roles of circPPP1R12A and its encoded protein circPPP1R12A-73aa. RNA-sequencing and Western blotting analysis were furthered employed to identify the critical signaling pathway regulated by circPPP1R12A-73aa. Results We firstly screened the expression profiles of human circRNAs in CC tissues and found that the expression of hsa_circ_0000423 (termed as circPPP1R12A) was significantly increased in CC tissues. We also found that circPPP1R12A was mostly localized in the cytoplasm of CC cells. Kaplan–Meier analysis showed that patients with higher levels of circPPP1R12A had a significantly shorter overall survival. By gain- and loss-of-function approaches, the results suggested that circPPP1R12A played a critical role in proliferation, migration and invasion of CC cells. Furthermore, we showed that circPPP1R12A carried an open reading frame (ORF), which encoded a functional protein (termed as circPPP1R12A-73aa). Next, we found that PPP1R12A-C, not circPPP1R12A, promoted the proliferation, migration and invasion abilities of CC in vitro and in vivo. Finally, we identified that circPPP1R12A-73aa promoted the growth and metastasis of CC via activating Hippo-YAP signaling pathway. In addition, the YAP specific inhibitor Peptide 17 dramatically alleviated the promotive effect of circPPP1R12A-73aa on CC cells. Conclusions In the present study, we illustrated the coding-potential of circRNA circPPP1R12A in the progression of CC. Moreover, we identified that circPPP1R12A-73aa promoted the tumor pathogenesis and metastasis of CC via activating Hippo-YAP signaling pathway. Our findings might provide valuable insights into the development of novel potential therapeutic targets for CC. Electronic supplementary material The online version of this article (10.1186/s12943-019-1010-6) contains supplementary material, which is available to auth...

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Cancer immunotherapy has shown great promise as a new standard cancer therapeutic modality. However, the response rates are limited for current approach that depends on enhancing spontaneous antitumor immune responses. Therefore, increasing tumor immunogenicity by expressing appropriate cytokines should further improve the current immunotherapy. Interleukin-33 is a member of the IL-1 family of cytokines and is released by necrotic epithelial cells or activated innate immune cells and is thus considered a “danger” signal. The role of IL-33 in promoting type 2 immune responses and tissue inflammation has been well established. However, whether IL-33 drives antitumor immune responses is controversial. Our previous work established that IL-33 promoted the function of CD8+ T cells. Here, we showed that the expression of IL-33 in two types of cancer cells potently inhibited tumor growth and metastasis. Mechanistically, IL-33 increased numbers and IFNγ production by CD8+ T and NK cells in tumor tissues, thereby inducing a tumor microenvironment favoring tumor eradication. Importantly, IL-33 greatly increased tumor-antigen-specific CD8+ T cells. Furthermore, both NK and CD8+ T cells were required for the antitumor effect of IL-33. Moreover, depletion of regulatory T cells (Treg) worked synergistically with IL-33 expression for tumor elimination. Our studies established “alarmin” IL-33 as a promising new cytokine for tumor immunotherapy through promoting cancer-eradicating type 1 immune responses.

Purpose Radiofrequency ablation (RFA) has been shown to elicit tumor-specific T cell immune responses but is not sufficient to prevent cancer progression. Here we investigated immune suppressive mechanisms limiting the efficacy of RFA. Experimental design We performed a retrospective case-controlled study on patients with synchronous colorectal cancer liver metastases who had received primary tumor resection with or without pre-operative RFA for liver metastases. Tumor infiltrating T cells and tumoral PD-L1 expression in human colorectal cancer tissues were analyzed by immunohistochemistry. T cell immune responses and PD-1/PD-L1 expression were also characterized in a RFA mouse model. In addition, the combined effect of RAF and PD-1 blockade was evaluated in the mouse RFA model. Results We found that RFA treatment of liver metastases increased not only T cell infiltration but also PD-L1 expression in primary human colorectal tumors. Using mouse tumor models, we demonstrated that RFA treatment of one tumor initially enhanced a strong T cell-mediated immune response in tumor. Nevertheless, tumor quickly overcame the immune responses by inhibiting the function of CD8+ and CD4+T cells, driving a shift to higher Treg to Teff ratio, and up-regulating of PD-L1/PD-1 expression. Furthermore, we established that the combined therapy of RFA and anti-PD-1 antibodies significantly enhanced T cell immune responses, resulting in stronger antitumor immunity and prolonged survival. Conclusions The PD-L1/PD-1 axis plays a critical role in dampening RFA-induced antitumor immune responses. And this study provides a strong rationale for combining RFA and the PD-L1/PD-1 blockade in the clinical setting.

Background/Aims: The role of Tumor-infiltrating lymphocytes (TILs) in the prognosis of patients with lung cancer is still controversial. We performed a meta-analysis to evaluate the prognostic role of TILs in lung cancer. Methods: Studies were recruited by searching PubMed, Embase and the Cochrane Library and assessed by further quality evaluation. The pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to investigate the association between TIL subsets and lung cancer patients' outcome. Results: A total of 29 articles including 8,600 patients were enrolled into the meta-analysis. Our results indicated that high level of CD8⁺ cells infiltration in tumor stroma (TS) or tumor nest (TN) was associated with better OS in lung cancer patients (HR = 0.76, 95% CI 0.62-0.93, P = 0.006; HR = 0.80, 95% CI 0.67-0.96; P = 0.018, respectively). Similar results could be also observed in CD3⁺ T cells infiltration. High CD4⁺ T lymphocytes infiltration in TS was explicitly accompanied by better OS (HR = 0.65, 95% CI 0.46-0.91; P = 0.013), rather than in TN. In contrast, high density of FOXP3⁺ T cells infiltration in TS showed a poor PFS (HR = 2.67, 95% CI, 1.74-4.08, P < 0.001). Conclusion: This meta-analysis clarified that high level of CD8⁺ and CD3⁺ T cells infiltration in TS or TN, and high CD4⁺ T lymphocytes infiltration in TS showed better OS in lung cancer patients, whereas high density of FOXP3⁺ T cells infiltration in TS could be recognized as a negative prognostic factor.