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.

Background: N‐acetyltransferase 10 ( NAT10 ) is the only enzyme known to mediate the N4‐acetylcytidine (ac4C) modification of mRNA and is crucial for mRNA stability and translation efficiency. However, its role in cancer development and prognosis has not yet been explored. This study aimed to examine the possible role of NAT10 in colon cancer. Methods: The expression levels of NAT10 were evaluated by immunohistochemical analyses with a colon cancer tissue microarray, and its prognostic value in patients was further analyzed. Quantitative real‐time polymerase chain reaction (qRT‐PCR) and Western blotting were performed to analyze NAT10 expression in harvested colon cancer tissues and cell lines. Stable NAT10 ‐knockdown and NAT10 ‐overexpressing colon cancer cell lines were constructed using lentivirus. The biological functions of NAT10 in colon cancer cell lines were analyzed in vitro by Cell Counting Kit‐8 (CCK‐8), wound healing, Transwell, cell cycle, and ferroptosis assays. Xenograft models were used to analyze the effect of NAT10 on the tumorigenesis and metastasis of colon cancer cells in vivo. Dot blotting, acetylated RNA immunoprecipitation‐qPCR, and RNA stability analyses were performed to explore the mechanism by which NAT10 functions in colon cancer progression. Results: NAT10 was upregulated in colon cancer tissues and various colon cancer cell lines. This increased NAT10 expression was associated with shorter patient survival. Knockdown of NAT10 in two colon cancer cell lines (HT‐29 and LoVo) impaired the proliferation, migration, invasion, tumor formation and metastasis of these cells, whereas overexpression of NAT10 promoted these abilities. Further analysis revealed that NAT10 exerted a strong effect on the mRNA stability and expression of ferroptosis suppressor protein 1 ( FSP1 ) in HT‐29 and LoVo cells. In these cells, FSP1 mRNA was found to be modified by ac4C acetylation, and this epigenetic modification was associated with the inhibition of ferroptosis. Conclusions: Our study revealed that NAT10 plays a critical role in colon cancer development by affecting FSP1 mRNA stability and ferroptosis, suggesting that NAT10 could be a novel prognostic and therapeutic target in colon cancer.

Nectin-4, also known as PVRL4 (poliovirus-receptor-like 4), is specifically expressed in the embryo and placenta. Recent studies have reported that the Nectin-4 is over-expressed in multiple human cancers, and such abnormal expression is associated with cancer progression and poor prognosis of the patients. In the present study, we aimed to characterize the expression pattern of Nectin-4 in human esophageal cancer (EC) tissues, and to investigate its clinical implications, prognostic value and regulatory effects on cellular functions of EC cells. In the present study, we first examined Nectin-4 expression in human EC tissues by using immunohistochemistry (IHC) assay and analyzed the clinical associations. Then the cellular studies in vitro and the nude mice tumor model in vivo were used to examine the regulatory role of Nectin-4 in the progression of EC. Our results demonstrated that over-expression of Nectin-4 in human EC tissues was significantly associated with tumor size, depth of tumor invasion, and poor prognosis of the patients. The intervention of Nectin-4 expression in EC cell lines showed that the increased Nectin-4 expression could significantly promote the cell viability, migration, invasion and tumor formation. Our present data unveiled that Nectin-4 played an important role in tumor biology and could serve as a useful prognostic predictor of human EC.

It is well known that human clear cell renal cell carcinoma (ccRCC) is a highly immunogenic and chemo-resistant tumor. Recently, emerging data suggest that the immune checkpoint blockade therapy is an important breakthrough in the treatment against ccRCC. HHLA2, a recently reported member of B7 family, is uniquely expressed in humans but not in mice, and it plays an important role in the functional inhibition of CD4 and CD8 T cells. Herein, we aimed to study the clinical implications of HHLA2 expression in human ccRCC and its potential regulatory role in the biological functions of the cancer cells. In the present study, we examined HHLA2 expression in human ccRCC tissues and analyzed the clinical implications as well as prognostic value. The intervention of HHLA2 in human ccRCC cell lines ACHN and 786-O was performed and its effect on the cellular function of the cells was also analyzed. We also identified the differentially expressed genes upon HHLA2 knockdown in ccRCC cell lines by using gene microarray analysis. We found that higher HHLA2 mRNA expression level in human ccRCC tissues compared with that in adjacent normal tissues based on TCGA data, and the HHLA2 expression at mRNA level was positively and significantly correlated with PD-L1, PD-L2, B7-H6, but negatively and significantly correlated with B7-H3. Moreover, our immunohistochemistry study showed that the staining intensity of HHLA2 in human ccRCC tissues was significantly higher than that in the adjacent normal tissues, and the overall survival rate of ccRCC patients with higher HHLA2 expression was significantly poorer than that of the patients with lower HHLA2 expression. Higher expression of HHLA2 in ccRCC tissues was positively and significantly associated with larger tumor size and advanced TNM stage. The COX model revealed that the parameters including patient’s age, TNM stage and HHLA2 expression level could be used as the independent risk factors respectively for the prognostic prediction of the patients. Our cellular study showed that upon knockdown of HHLA2 expression in human ccRCC cell lines, the cell viability, the migration and the invasion ability were significantly inhibited, while the cell cycle arrest at G1 phase was induced and the expressions of Cyclin D1, c-Myc and Cyclin E1 were decreased. In addition, according to the microarray data, the expressions of epithelia-to-mesenchymal transition markers, such as E-cadherin, N-cadherin and Vimentin, were significantly changed after knockdown of HHLA2 expression. Our findings indicated that HHLA2 was involved in the progression of human ccRCC and could be used as an important prognostic predictor for this malignancy.

T-cell immunoglobulin and mucin domain 1 (TIM-1) is an important co-stimulatory molecule which serves as a surface marker for T cell activation, especially for Th2 cells. Recently, many studies have also shown that TIM-1 can be abnormally expressed in human cancers and may have a potential role in promoting cancer progression. The immunohistochemistry was used to examine the TIM-1 expression in human non-small-cell lung carcinoma (NSCLC) tissues. The cellular studies were performed to investigate the role of TIM-1 in the regulation of biological functions of human lung cancer cell lines. We found that the TIM-1 expression was increased in human NSCLC tissues compared with the adjacent normal tissues, and the OS rate of NSCLC patients with higher TIM-1 expression was significantly lower compared with the ones with lower TIM-1 expression. The COX model showed that higher TIM-1 expression in lung cancer tissues could be used as an independent prognostic predictor for the patients. Furthermore, we depleted TIM-1 in NSCLC cell lines A549 and SK-MES-1, and the cellular functional studies also revealed that depletion of TIM-1 could significantly inhibit the cell viability as well as the abilities of migration and invasion. In addition, our microarray data showed that certain signaling pathways were altered and enriched after depletion of TIM-1. We subsequently verified that PI3K/Akt signaling pathway was involved in the TIM-1-mediated regulation of cellular functions in NSCLC cells. Our findings supported the notion that TIM-1 could serve as a potential therapeutic target for NSCLC.

Recent studies have suggested that B7-H6, a new member of the B7 family of ligands, not only is a crucial regulator of NK cell-mediated immune responses but also has important clinical implications due to its abnormal expression in many human cancers. We have previously reported that higher B7-H6 expression levels in ovarian cancer tissues are positively correlated with tumor metastasis and cancer progression. To date, the expression of B7-H6 in human hepatocellular carcinoma (HCC) and the clinical significance of B7-H6 expression still remain elusive. In the present study, the expression level of B7-H6 was examined in both HCC tissues and HCC cell lines (HepG2 and SMMC-7721). And the clinical significance of B7-H6 was analyzed as well. Our results revealed that B7-H6 was expressed abnormally in HCC tissues, which was greatly related to tumor size. The TCGA data also showed that the B7-H6 mRNA expression level was significantly negatively correlated with the survival of HCC patients. Next, to investigate the functions of B7-H6 in HCC, we successfully constructed B7-H6 knockdown expression human HCC cell lines using the RNA interference technology. Our studies showed that reduced expression of B7-H6 in HepG2 and SMMC-7721 cells significantly attenuated cell proliferation as well as cell migration and invasion. Besides, depletion of B7-H6 greatly induced cell cycle arrest at G1 phase. And also B7-H6 knockdown in HCC cell lines dramatically decreased the C-myc, C-fos and Cyclin-D1 expression. Our present findings suggested that B7-H6 played an important role in oncogenesis of HCC on cellular level, and B7-H6 could be employed to develop immunotherapeutic approaches targeting this malignancy.