Diagnostic utility of serum dipeptidyl peptidase (DPP- IV) /CD26 as a serum marker in Egyptian patients with colorectal cancer

Down-regulation of DPP4 by TGFβ1/miR29a-3p inhibited proliferation and promoted migration of ovarian cancer cells

OBJECTIVE

To explore the DPP4 expression changes and functions in ovarian cancer (OV), as well as the regulation mechanism for DDP4.

METHODS

GEPIA2, GSE18520, GSE26712 and UALCAN were used to analyze differences in DPP4 expression between OV tumors and control tissues. Serum DPP4 levels were measured by ELISA. The prognostic values of DPP4 were evaluated using a Kaplan-Meier (KM) plotter. Small interfering RNA was used for DPP4 knockdown in OVCAR-3 and SKOV-3 cells. CCK-8 and scratch healing assays were used to determine the cells' proliferation and migration abilities. Flow cytometry (FCM) was used to detect the cell cycle and apoptosis. A dual-luciferase assay was designed to confirm the regulatory effect of miR-29a-3p on DPP4.

RESULTS

The expressions of DPP4 mRNA and protein were decreased in OV tumor tissues. Serum DPP4 levels decreased in OV patients. KM plotter analysis showed correlation between high DPP4 expression and a poor prognosis in OV patients. By targeting knockdown of DPP4, we found that OVCAR-3 and SKOV-3 cells' proliferation was inhibited, while cell's migration ability was significantly promoted. FCM analysis showed that DPP4 knockdown induced a decrease in the S phase. Furthermore, DPP4 was shown to be downregulated by miR-29a-3p and TGFβ1 in OVCAR-3 cells, and miR-29a-3p expression was upregulated by TGFβ1. The effects of miR-29a-3p and TGFβ1 on OVCAR-3 cells' biological behaviors were consistent with DPP4 knockdown.

CONCLUSION

DPP4 was downregulated in OV patients. DPP4 knockdown significantly inhibited OVCAR-3 and SKOV-3 cell proliferation and promoted cell migration. DDP4 can be downregulated by TGFβ1 through the upregulation of miR-29a-3p in OV cells.

Research Progress on Dipeptidyl Peptidase Family: Structure, Function and Xenobiotic Metabolism

Prolyl-specific peptidases or proteases, including Dipeptidyl Peptidase 2, 4, 6, 8, 9, 10, Fibroblast Activation Protein, prolyl endopeptidase and prolyl carboxypeptidase, belong to the dipeptidyl peptidase family. In human physiology and anatomy, they have homology amino acid sequences, similarities in structure, but play distinct functions and roles. Some of them also play important roles in the metabolism of drugs containing endogenous peptides, xenobiotics containing peptides, and exogenous peptides. The major functions of these peptidases in both the metabolism of human health and bioactive peptides are of significant importance in the development of effective inhibitors to control the metabolism of endogenous bioactive peptides. The structural characteristics, distribution of tissue, endogenous substrates, and biological functions were summarized in this review. Furthermore, the xenobiotics metabolism of the dipeptidyl peptidase family is illustrated. All the evidence and information summarized in this review would be very useful for researchers to extend the understanding of the proteins of these families and offer advice and assistance in physiology and pathology studies.

Dipeptidyl peptidase IV is required for endometrial carcinoma cell proliferation and tumorigenesis via the IL-6/STAT3 pathway

AIM

To study the functions and signaling pathways controlled by dipeptidyl peptidase IV (DPPIV) in endometrial carcinoma (EC).

METHODS

DPPIV expression in EC cells was detected by flow cytometry, reverse transcription-polymerase chain reaction analysis and Western blot. Interleukin-6 (IL-6) expression in the supernatant was measured by enzyme-linked immunosorbent assay. The protein levels of signal transducers and activators of transcription-3 (STAT3), phosphorylate STAT3, cellular Myc, and vascular endothelial growth factor in EC cells were measured by Western blot. Colony formation assays were used to assess the clonogenicity of EC cells. Ki67 immunostaining and cell counting were used to test the proliferative ability of EC cells. Nude mouse tumorigenicity assay was used to confirm DPPIV promotes the tumorigenicity of EC cells. A cell counting kit-8 assay was used to determine the half-maximal inhibitory concentration of sitagliptin.

RESULTS

Overexpression of DPPIV in EC cells with low DPPIV expression promoted cell proliferation in vitro (p < 0.01) and enhanced tumorigenicity in vivo (p < 0.05). Conversely, knocking down DPPIV expression in EC cells with high DPPIV expression inhibited cell proliferation (p < 0.01) and in vivo tumorigenicity (p < 0.01). DPPIV promoted EC cell proliferation via activation of IL-6/STAT3 signaling pathway, and that IL-6 could trigger a positive feedback loop that increased DPPIV expression (p < 0.01). Furthermore, the DPPIV inhibitor reduced STAT3 expression (p < 0.01) and inhibited growth of EC cells (p < 0.001).

CONCLUSION

DPPIV enhances the properties that allow tumorigenesis in EC via IL-6 and STAT3 signaling.