PAUF Induces Migration of Human Pancreatic Cancer Cells Exclusively via the TLR4/MyD88/NF-κB Signaling Pathway.

PAUF, a tumor-promoting protein secreted by cancer cells, exerts paracrine effects on immune cells through TLR4 receptors expressed on immune cell surfaces. This study aimed to investigate if PAUF elicits autocrine effects on pancreatic cancer (PC) cells through TLR4, a receptor that is overexpressed on PC cells. In this study, TLR4 expression was detected in PC cells only, but not normal pancreatic cells. The migration of TLR4 high-expressing PC cells (i.e., BxPC-3) was reduced by a selective TLR4 inhibitor, in a dose-dependent manner. Using TLR4 overexpressed and knockout PC cell lines, we observed direct PAUF-TLR4 binding on the PC cell surfaces, and that PAUF-induced cancer migration may be mediated exclusively through the TLR4 receptor. Further experiments showed that PAUF signaling was passed down through the TLR4/MyD88 pathway without the involvement of the TLR4/TRIF pathway. TLR4 knockout also downregulated PC membrane PD-L1 expression, which was not influenced by PAUF. To the best of our knowledge, TLR4 is the first receptor identified on cancer cells that mediates PAUF's migration-promoting effect. The results of this study enhanced our understanding of the mechanism of PAUF-induced tumor-promoting effects and suggests that TLR4 expression on cancer cells may be an important biomarker for anti-PAUF treatment.

Translocalization of enhanced PKM2 protein into the nucleus induced by cancer upregulated gene 2 confers cancer stem cell-like phenotypes.

Increased mRNA levels of cancer upregulated gene (CUG)2 have been detected in many different tumor tissues using Affymetrix microarray. Oncogenic capability of the CUG2 gene has been further reported. However, the mechanism by which CUG2 overexpression promotes cancer stem cell (CSC)-like phenotypes remains unknown. With recent studies showing that pyruvate kinase muscle 2 (PKM2) is overexpressed in clinical tissues from gastric, lung, and cervical cancer patients, we hypothesized that PKM2 might play an important role in CSC-like phenotypes caused by CUG2 overexpression. The present study revealed that PKM2 protein levels and translocation of PKM2 into the nucleus were enhanced in CUG2-overexpressing lung carcinoma A549 and immortalized bronchial BEAS-2B cells than in control cells. Expression levels of c-Myc, CyclinD1, and PKM2 were increased in CUG2-overexpressing cells than in control cells. Furthermore, EGFR and ERK inhibitors as well as suppression of Yap1 and NEK2 expression reduced PKM2 protein levels. Interestingly, knockdown of ß-catenin expression failed to reduce PKM2 protein levels. Furthermore, reduction of PKM2 expression with its siRNA hindered CSC-like phenotypes such as faster wound healing, aggressive transwell migration, and increased size/number of sphere formation. The introduction of mutant S37A PKM2-green fluorescence protein (GFP) into cells without ability to move to the nucleus did not confer CSC-like phenotypes, whereas forced expression of wild-type PKM2 promoted such phenotypes. Overall, CUG2-induced increase in the expression of nuclear PKM2 contributes to CSC-like phenotypes by upregulating c-Myc and CyclinD1 as a co-activator. [BMB Reports 2022;55(2): 98-103].

CGK062, a small chemical molecule, inhibits cancer upregulated gene 2­induced oncogenesis through NEK2 and ß­catenin.

The mechanisms through which cancer­upregulated gene 2 (CUG2), a novel oncogene, affects Wnt/ß­catenin signaling, essential for tumorigenesis, are unclear. In this study, we aimed to elucidate some of these mechanisms in A549 lung cancer cells. Under the overexpression of CUG2, the protein levels and activity of ß­catenin were evaluated by western blot analysis and luciferase assay. To examine a biological consequence of ß­catenin under CUG2 overexpression, cell migration, invasion and sphere formation assay were performed. The upregulation of ß­catenin induced by CUG2 overexpression was also accessed by xenotransplantation in mice. We first found that CUG2 overexpression increased ß­catenin expression and activity. The suppression of ß­catenin decreased cancer stem cell (CSC)­like phenotypes, indicating that ß­catenin is involved in CUG2­mediated CSC­like phenotypes. Notably, CUG2 overexpression increased the phosphorylation of ß­catenin at Ser33/Ser37, which is known to recruit E3 ligase for ß­catenin degradation. Moreover, CUG2 interacted with and enhanced the expression and kinase activity of never in mitosis gene A­related kinase 2 (NEK2). Recombinant NEK2 phosphorylated ß­catenin at Ser33/Ser37, while NEK2 knockdown decreased the phosphorylation of ß­catenin, suggesting that NEK2 is involved in the phosphorylation of ß­catenin at Ser33/Ser37. Treatment with CGK062, a small chemical molecule, which promotes the phosphorylation of ß­catenin at Ser33/Ser37 through protein kinase C (PKC)α to induce its degradation, reduced ß­catenin levels and inhibited the CUG2­induced features of malignant tumors, including increased cell migration, invasion and sphere formation. Furthermore, CGK062 treatment suppressed CUG2­mediated tumor formation in nude mice. Taken together, the findings of this study suggest that CUG2 enhances the phosphorylation of ß­catenin at Ser33/Ser37 by activating NEK2, thus stabilizing ß­catenin. CGK062 may thus have potential for use as a therapeutic drug against CUG2­overexpressing lung cancer cells.