Gastric tumour-derived ANGPT2 regulation by DARPP-32 promotes angiogenesis

Abstract

Objective Overexpression of dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32), and its truncated isoform (t-DARPP) are associated with gastric tumorigenesis. Herein, we investigated the role of DARPP-32 proteins in regulating angiopoietin 2 (ANGPT2) and promoting tumor angiogenesis. Design Quantitative real-time RT-PCR, immunoblotting, luciferase reporter, immunofluorescence, immunohistochemistry, and angiogenesis assays were applied to investigate the regulation of angiogenesis by DARPP-32 proteins. Results Overexpression of DARPP-32 significantly increased the mRNA and protein levels of ANGPT2 in gastric cancer cells. The overexpression of DARPP-32 T34A mutant or the N-terminal truncated isoform, t-DARPP, led to similar effects ruling out the T34-dependent regulation of protein phosphatase 1 activity in regulating ANGPT2. DARPP-32 proteins induced a secreted form of ANGPT2, which was detectable in the media, functionally active, and able to induce angiogenesis, measured by the HUVEC tube formation assay. Antibody blocking of the secreted ANGPT2 abrogated its function. To identify the mechanism by which DARPP-32 regulates ANGPT2, we examined the activities of NF-κB and STAT3, known regulators of angiogenesis. The results ruled out NF-κB and showed induction of STAT3 phosphorylation, activation, and nuclear localization. Inhibition or knockdown of STAT3 significantly attenuated the induction of ANGPT2 by DARPP-32 proteins. In vivo xenografts models demonstrated that overexpression of DARPP-32 promotes angiogenesis and tumor growth. Analyses of human gastric cancer tissues showed a strong correlation between DARPP-32 and ANGPT2. Conclusion Our novel findings establish the role of DARPP-32-STAT3 axis in regulating ANGPT2 in cancer cells to promote angiogenesis and tumorigenesis.

Integrated expression analysis identifies transcription networks in mouse and human gastric neoplasia

“…STAT3 is constitutively activated in several gastrointestinal malignancies that include colon cancer and GC . We have previously shown that STAT3 regulates angiogenesis, drug response, and cellular proliferation in GC . A number of studies have shown that STAT3 promotes stem‐like properties and maintenance of cancer cells providing resistance to several chemotherapeutic drugs .…”

Integrated molecular analysis reveals complex interactions between genomic and epigenomic alterations in esophageal adenocarcinomas

“…These growth factors are important in repair of reflux-induced esophageal injury and play important roles in cellular homoeostasis, angiogenesis, and gastrointestinal carcinogenesis50515253.…”

NF-κB mediated transcription of DARPP-32 preventsHelicobacter pylori-induced cell death

“…With respect to gastric cancer, DARPP-32 has been implicated in angiogenesis through induction of STAT3 and angiopoietin2,12 and cell invasion through induction of type 1 matrix metalloproteinase and the chemokine CXCR4 13. Reduced expression of DARPP-32 significantly decreases gastric cancer cell proliferation in vitro and decreases the growth of gastric tumour xenografts in nude mice by preventing AKT phosphorylation, which plays a critical role in resistance to EGFR tyrosine kinase inhibitors such as gefitinib 14.…”