Background: Colorectal cancer (CRC) is one of the most common aggressive malignancies. LACTB functions as a tumor suppressor, and previous findings have demonstrated that LACTB can inhibit epithelial-to-mesenchymal transition (EMT) and proliferation of breast cancer and CRC cells. However, few studies have investigated the roles of LACTB in autophagy and proliferation in CRC. The current study aimed to identify the roles of LACTB in EMT and proliferation associated with autophagy in CRC and to elucidate the probable molecular mechanisms through which LACTB are involved in these processes. Materials and Methods: Transwell invasion, MTT, transmission electron microscopy, RNA-seq, immunoprecipitation, immunohistochemistry and Western blotting assays were performed to evaluate the migratory, invasive, proliferative and autophagic abilities of CRC cells, and the levels of active molecules involved in PI3K/AKT signaling were examined through Western blotting analysis. In addition, the in vivo function of LACTB was assessed using a tumor xenograft model. Results: Weaker LACTB expression was found in CRC tissue samples than in nonmalignant tissue samples, and LACTB inhibited cell invasion, migration, and proliferation by promoting autophagy in vitro. Furthermore, the regulatory effects of LACTB on autophagy and EMT were partially attributed to the PI3K/AKT signaling pathway. The in vivo results also showed that LACTB modulated CRC tumorigenesis. Conclusion: LACTB can regulate the activity of PIK3R3 to influence the level of PI3K, and it also promotes autophagy and inhibits EMT and proliferation in part through the PI3K/AKT/mTOR signaling pathway.

Colorectal cancer (CRC) is one of the high incidences tumours and is ranked second in cancer-related mortality. Even though great progress has been made, there are no effective therapeutic strategies for late stage and metastatic CRC patients. Acidity is one characteristic of the tumour microenvironment. However, how cancer cells respond to this acidic environment surrounding them remains largely unknown, especially in colorectal cancer. Proton sensor receptor expression was analysed in GEO and TCGA datasets. The expression of GPR4 in CRC specimens was confirmed by western blotting and immunohistochemistry (IHC). The role of GPR4 in CRC progression was analysed both in vitro and in vivo. Pharmacological intervention, immunofluorescence and gene set enrichment analyses were performed to reveal the underlying molecular mechanisms of GPR4. We found that GPR4 was upregulated in CRC samples. In addition, its high expression correlated with late stage tumours and poor overall survival in patients. Furthermore, loss-of-function assays proved that GPR4 promoted CRC carcinogenesis and metastatic ability. Mechanistically, GPR4 was activated by extracellular protons in the tumour microenvironment and enhanced RhoA activation and F-actin rearrangement, leading to LATS activity inhibition, YAP1 nuclear translocation and oncogene transcription. The expression of GPR4 is upregulated in colorectal cancer and is associated with shorter overall survival time in CRC patients. These findings reveal the novel roles of GPR4 in CRC progression and suggest GPR4 might be a new therapeutic target for CRC treatment.

Background/Aims: ADAMTSs (A disintegrin and metalloprotease domains with thrombospondins motifs) are a family of extracellular proteases that have been related to both oncogenic and tumor-suppressive functions. The aim of the present study was to investigate: 1) the mutation, copy-number alterations, and expression profile of ADAMTSs in colorectal cancer and 2) whether ADAMTSs participate in colorectal cancer (CRC) progression and invasion. Methods: The mutation, copy-number alterations, and expression profile of ADAMTSs in CRC were analyzed in the TCGA cohort using cBioportal. ADAMTS4 expression in tumor tissues and cell lines were determined by immunostaining and real-time quantitative PCR. The role of ADAMTS-4 in CRC progression and the underlying mechanisms were studied by using short hairpin RNA-mediated knockdown of ADAMTS4. The effects of ADAMTS4 in cell proliferation and invasion were determined by clone formation assay and transwell migration assay, respectively. Macrophages were depleted by liposomal clodronate in immune-competent BALB/c mice and tumor growth was analyzed. Results: ADAMTS4 was differentially expressed in CRC and predicted a poor prognosis. Elevated ADAMTS4 expression was closely associated with larger tumor size, enhanced TNM stage, and a poor clinical outcome in patients with CRC. ADAMTS4 knockdown had no inhibitory implications on cell proliferation and invasion in vitro, but significantly attenuated tumor growth in vivo. Mechanistically, we revealed that ADAMTS4 was associated macrophages infiltration and polarization in the tumor microenvironment of CRC. Macrophage depletion largely abolished the promotive effect of ADAMTS4 on tumor growth in the immune competent BALB/c mice. Conclusion: ADAMTS4 seemed to be a promising prognostic indicator in CRC. The novel link between ADAMTS4 and macrophages mirrors the potential regulatory roles of ADAMTSs in the inflammatory microenvironment of cancers.

The G‐protein‐coupled receptor 126 (GPR126) may play an important role in tumor development, although its role remains poorly understood. We found that GPR126 had higher expression in most colorectal cancer cell lines than in normal colon epithelial cell lines, and higher expression levels in colorectal cancer tissues than in normal adjacent colon tissues. GPR126 knockdown induced by shRNA inhibited cell viability and colony formation in HT‐29, HCT116, and LoVo cells, decreased BrdU incorporation into newly synthesized proliferating HT‐29 cells, led to an arrest of cell cycle progression at the G1 phase in HCT‐116 and HT‐29 cells, and suppressed tumorigenesis of HT‐29, HCT116, and LoVo cells in nude mouse xenograft models. GPR126 knockdown engendered decreased transcription and translation of histone deacetylase 2 (HDAC2), previously implicated in the activation of GLI1 and GLI2 in the Hedgehog signaling pathway. Ectopic expression of HDAC2 in GPR126‐silenced cells restored cell viability and proliferation, GLI2 luciferase reporter activity, partially recovered GLI2 expression, and reduced the cell cycle arrest. HDAC2 regulated GLI2 expression and, along with GLI2, it bound to the PTCH1 promoter, as evidenced by a chip assay with HT‐29 cells. Purmorphamine, a hedgehog agonist, largely restored the cell viability and expression of GLI2 proteins in GPR126‐silenced HT‐29 cells, whereas GANT61, a hedgehog inhibitor, further enhanced the GPR126 knockdown‐induced inhibitory effects. Our findings demonstrate that GPR126 regulates colorectal cancer cell proliferation by mediating the expression of HDAC2 and GLI2, therefore it may represent a suitable therapeutic target for colorectal cancer treatment.