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The developmental pluripotency-associated 4 (Dppa4) gene serves critical roles in cell self-renewal, as well as in cancer development and progression. However, the regulatory role of Dppa4 in non-small-cell lung cancer (NSCLC) and its underlying mechanisms remain elusive. The aim of the present study was to investigate the biological function of Dppa4 in NSCLC and its underlying mechanism of action. Dppa4 expression was measured in NSCLC tissue samples and cell lines, and its effect on cell proliferation and the expression of glycolytic enzymes was determined. In addition, the underlying mechanisms of Dppa4-induced alterations in glycolysis were analyzed. Univariate and multivariate analyses were also performed to analyze the prognostic significance of clinicopathological characteristics. Dppa4 was found to be highly expressed in NSCLC tissues and cell lines. Furthermore, it was observed that Dppa4 was correlated with the degree of tumor differentiation and TNM stage. Univariate and multivariate analyses identified Dppa4 expression and clinical stage as prognostic factors for NSCLC patients. Kaplan-Meier analysis further revealed that patients with lower Dppa4 expression exhibited a better prognosis. In NSCLC cells, Dppa4 knockdown inhibited cell proliferation, while Dppa4 overexpression enhanced cell proliferation, which was likely mediated by glycolysis promotion. Dppa4 knockdown had no evident effect on the majority of enzymes examined; however, glucose transporter type 4 (GLUT-4) and pyruvate kinase isozyme M2 were significantly upregulated, and hexokinase II (HK-II) and lactate dehydrogenase B (LDHB) were downregulated following Dppa4 knockdown. By contrast, Dppa4 overexpression resulted in downregulation of GLUT-4, and upregulation of HK-II, enolase and LDHB, whereas it had no effect on other enzymes. Since the most evident effect was observed on LDHB, further functional experiments demonstrated that this enzyme reversed the promoting effects of Dppa4 in NSCLC. In conclusion, Dppa4 promotes NSCLC progression, partly through glycolysis by LDHB. Thus, the Dppa4-LDHB axis critically contributes to glycolysis in NSCLC cells, thereby promoting NSCLC development and progression. more...

The D816X (X = V, H, Y or F) missense mutation constitutively activates c-Kit kinase in gastrointestinal stromal tumor (GIST) and has been observed to cause acquired resistance against first-line and second-line kinase inhibitors. In the present study, the allosteric mechanism of D816X-induced c-Kit conformational change is investigated at molecular level. The Asp816 residue is located at the activation loop (A-loop) of c-Kit and the mutation can eliminate a negative formal charge from the loop region by substituting the acidic asparagic acid residue with neutral valine, histidine, tyrosine or phenylalanine. Here, we classify the c-Kit kinase into four states in terms of its mutation (wild type or mutant) and conformation (DFG-in or DFG-out). The wild-type kinase is electrostatically stabilized in inactive DFG-out conformation, whereas the D816X mutation can promote the conformational conversion to active DFG-in and then activate the kinase. Structural analysis reveals that the Asp816 residue in DFG-out is surrounded by a number of polar and positively charged residues within its first and second shells of protein context, and kinase conformational change to DFG-in brings this residue into a negative electrostatic potential environment. Dynamics simulation characterizes that the c-Kit conformational conversion from DFG-out to DFG-in can cause local unfavorable effect to type-II inhibitor, while the mutation-induced global structural rearrangement would participate in the favorable interaction of c-Kit with type-I inhibitor. more...