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Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and treatment-resistant malignancy. The lack of pathway-informed biomarkers hampers the development of rational diagnostics or therapies. Recently, the protein abnormal spindle-like microcephaly-associated (ASPM) was identified as a novel Wnt and stemness regulator in PDAC, while the pathogenic roles of its protein isoforms remain unclarified. We developed novel isoform-specific antibodies and genetic knockdown (KD) of putative ASPM isoforms, whereby we uncovered that the levels of ASPM isoform 1 (iI) and ASPM-iII are variably upregulated in PDAC cells. ASPM isoforms show remarkably different subcellular locations; specifically, ASPM-iI is exclusively localized to the cortical cytoplasm of PDAC cells, while ASPM-iII is predominantly expressed in cell nuclei. Mechanistically, ASPM-iI co-localizes with disheveled-2 and active β-catenin as well as the stemness marker aldehyde dehydrogenase-1 (ALDH-1), and its expression is indispensable for the Wnt activity, stemness, and the tumorigenicity of PDAC cells. By contrast, ASPM-iII selectively regulates the expression level of cyclin E and cell cycle progression in PDAC cells. The expression of ASPM-iI and ASPM-iII displays considerable intratumoral heterogeneity in PDAC tissues and only that of ASPM-iI was prognostically significant; it outperformed ALDH-1 staining and clinico-pathological variables in a multivariant analysis. Collectively, the distinct expression patterns and biological functions of ASPM isoforms may illuminate novel molecular mechanisms and prognosticators in PDAC and may pave the way for the development of therapies targeting this novel oncoprotein. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland., (© 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.)

The cell cycle is a temporal program that regulates DNA synthesis and cell division. When we compared the codon usage of cell cycle-regulated genes with that of other genes, we discovered that there is a significant preference for non-optimal codons. Moreover, genes encoding proteins that cycle at the protein level exhibit non-optimal codon preferences. Remarkably, cell cycle-regulated genes expressed in different phases display different codon preferences. Here, we show empirically that transfer RNA (tRNA) expression is indeed highest in the G2 phase of the cell cycle, consistent with the non-optimal codon usage of genes expressed at this time, and lowest toward the end of G1, reflecting the optimal codon usage of G1 genes. Accordingly, protein levels of human glycyl-, threonyl-, and glutamyl-prolyl tRNA synthetases were found to oscillate, peaking in G2/M phase. In light of our findings, we propose that non-optimal (wobbly) matching codons influence protein synthesis during the cell cycle. We describe a new mathematical model that shows how codon usage can give rise to cell-cycle regulation. In summary, our data indicate that cells exploit wobbling to generate cell cycle-dependent dynamics of proteins.

Although abnormal increases in the level or activity of cyclin-dependent kinase 4 (CDK4) occur frequently in cancer, the underlying mechanism is not fully understood. Here, we show that methionyl-tRNA synthetase (MRS) specifically stabilizes CDK4 by enhancing the formation of the complex between CDK4 and a chaperone protein. Knockdown of MRS reduced the CDK4 level, resulting in G0/G1 cell cycle arrest. The effects of MRS on CDK4 stability were more prominent in the tumor suppressor p16INK4a-negative cancer cells because of the competitive relationship of the two proteins for binding to CDK4. Suppression of MRS reduced cell transformation and the tumorigenic ability of a p16INK4a-negative breast cancer cell line in vivo. Further, the MRS levels showed a positive correlation with those of CDK4 and the downstream signals at high frequency in p16INK4a-negative human breast cancer tissues. This work revealed an unexpected functional connection between the two enzymes involving protein synthesis and the cell cycle.

Genetic alterations in the cell cycle pathway are common in head and neck squamous cell carcinoma (HNSCC). We identified four novel HNSCC susceptibility loci (CDKN1C rs452338, CDK4 rs2072052, E2F2 rs3820028 and E2F2 rs2075993) through a two-stage matched case–control study. There was a combined effect among the four single nucleotide polymorphisms (SNPs), as the number of risk genotypes increased, the risk of HNSCC displayed an increasing trend (P trend < 0.001). And there were multiplicative interactions between rs452338 and rs2072052, rs2072052 and rs3820028, rs2072052 and rs2075993. Functional bioinformatics analysis and dual-luciferase reporter assay revealed that E2F2 rs2075993 T>C reduced the stability of E2F2 3'-UTR secondary structure and affected the binding of E2F2 to miR-940, which was up-regulated in HNSCC tumor tissues (P = 2.9e−8) and was correlated with poor overall survival of HNSCC (HR = 1.39, 95% CI = 1.02–1.90). In vitro assays, we discovered that the expression of miR-940 was regulated by METTL3 , and miR-940 promoted the proliferation, migration and invasion, and inhibited the senescence and autophagy of tumor cells. In terms of mechanism, compared with rs2075993 allele T, we found that the protective variant rs2075993 allele C interfered with the translational inhibition of E2F2 by miR-940, resulting in increased expression of E2F2 protein, which further reduced the proliferation, migration, invasion, and increased the senescence of tumor cells. [ABSTRACT FROM AUTHOR]

Background: Cancer subtype switching, which involves unclear cancer cell origin, cell fate decision, and transdifferentiation of cells within a confined tumor microenvironment, remains a major problem in pancreatic cancer (PDA). Results: By analyzing PDA subtypes in The Cancer Genome Atlas, we identified that epigenetic silencing of apoptosis-associated tyrosine kinase (AATK) inversely was correlated with mRNA expression and was enriched in the quasi-mesenchymal cancer subtype. By comparing early mouse pancreatic lesions, the non-invasive regions showed AATK co-expression in cells with acinar-to-ductal metaplasia, nuclear VAV1 localization, and cell cycle suppression; but the invasive lesions conversely revealed diminished AATK expression in those with poorly differentiated histology, cytosolic VAV1 localization, and co-expression of p63 and HNF1α. Transiently activated AATK initiates acinar differentiation into a ductal cell fate to establish apical-basal polarization in acinar-to-ductal metaplasia. Silenced AATK and ectopically expressed p63 and HNF1α allow the proliferation of ductal PanINs in mice. Conclusion: Epigenetic silencing of AATK regulates the cellular transdifferentiation, proliferation, and cell cycle progression in converting PDA-subtypes. [ABSTRACT FROM AUTHOR]

NT157, a small-molecule tyrosine kinase inhibitor, exhibits broad-spectrum anti-tumor activity. However, NT157-mediated inhibition against glioma has not been explored yet. Herein, the anticancer effects and underlying mechanism of NT157 against human giloma growth were evaluated. The results showed that NT157 alone significantly inhibited glioma cells growth in vitro by lunching cell cycle arrest through up-regulating p21 and p27, and down-regulating cell cycle-related factors. NT157 alone also induced significant glioma cells apoptosis, followed by PARP cleavage and caspase-3 activation. Our findings further revealed that NT157 triggered significant DNA damage and dysfunction of PI3K/AKT, MAPKs and EGFR-STAT3 signaling pathways. Addition of several kinases inhibitors effectively abrogated NT157-induced DR5 up-regulation, which further confirmed the significant role of DR5 pathway. Moreover, combined treatment of NT157 and TRAIL showed enhanced apoptosis against U251 and U87 cells. However, Knockdown of DR5 expression significantly attenuated combined treatment-induced PARP cleavage and caspase-3 activation. Importantly, combined administration of NT157 and TRAIL in vivo effectively inhibited glioma xenograft growth of nude mice by inhibiting cell proliferation and angiogenesis, and inducing DNA damage and apoptosis. Taken together, our findings validated the rational design that combined strategy of NT157 and TRAIL to trigger DNA damage and apoptosis by up-regulating DR5 could be a high efficient way to combat human glioma. [Display omitted] • NT157 induced glioma cell cycle arrest and apoptosis. • NT157 enhanced TRAIL's anticancer effect by activating ROS and DR5 expression. [ABSTRACT FROM AUTHOR]