Department of Surgery, University of Miami Miller School of Medicine, Miami, FL, USA.
Department of Veterans Affairs, Miami Healthcare System, Miami, FL, USA.
Oncogene. 2019 Jul;38(29):5805-5816. doi: 10.1038/s41388-019-0843-1. Epub 2019 Jun 24.
Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32), is frequently overexpressed in early stages of gastric cancers. We utilized in vitro assays, 3D gastric gland organoid cultures, mouse models, and human tissue samples to investigate the biological and molecular impact of DARPP-32 on activation of IGF1R and STAT3 signaling and gastric tumorigenesis. DARPP-32 enhanced phosphorylation of IGF1R (Y1135), a step that was critical for STAT3 phosphorylation at Y705, nuclear localization, and transcription activation. By using proximity ligation and co-immunoprecipitation assays, we found that IGF1R and DARPP-32 co-existed in the same protein complex. Binding of DARPP-32 to IGF1R promoted IGF1R phosphorylation with subsequent activation of downstream SRC and STAT3. Analysis of gastric tissues from the TFF1 knockout (KO) mouse model of gastric neoplasia, demonstrated phosphorylation of STAT3 in the early stages of gastric tumorigenesis. By crossing the TFF1 KO mice with DARPP-32 (DP) knockout (KO) mice, that have normal stomach, we obtained double knockout (TFF1 KO/DP KO). The gastric mucosa from the double KO mice did not show phosphorylation of IGF1R or STAT3. In addition, the TFF1 KO/DP KO mice had a significant delay in developing neoplastic gastric lesions. Analysis of human gastric cancer tissue microarrays, showed high levels of DARPP-32 and positive immunostaining for nuclear STAT3 in cancer tissues, as compared to non-cancer histologically normal tissues. In summary, the DARPP-32-IGF1R signaling axis plays a key role in regulating the STAT3 signaling, a critical step in gastric tumorigenesis.
多巴胺和 cAMP 调节的磷蛋白，Mr32000（DARPP-32），在胃癌的早期阶段经常过度表达。我们利用体外测定、3D 胃腺类器官培养、小鼠模型和人类组织样本，研究 DARPP-32 对 IGF1R 和 STAT3 信号激活以及胃肿瘤发生的生物学和分子影响。DARPP-32 增强了 IGF1R 的磷酸化（Y1135），这是 STAT3 在 Y705 磷酸化、核定位和转录激活的关键步骤。通过使用邻近连接和共免疫沉淀测定，我们发现 IGF1R 和 DARPP-32 存在于同一个蛋白质复合物中。DARPP-32 与 IGF1R 的结合促进了 IGF1R 的磷酸化，随后激活了下游 SRC 和 STAT3。对 TFF1 敲除（KO）小鼠胃肿瘤模型中胃组织的分析表明，在胃肿瘤发生的早期阶段存在 STAT3 的磷酸化。通过将 TFF1 KO 小鼠与具有正常胃的 DARPP-32（DP）敲除（KO）小鼠杂交，我们获得了双敲除（TFF1 KO/DP KO）。来自双 KO 小鼠的胃黏膜没有显示 IGF1R 或 STAT3 的磷酸化。此外，TFF1 KO/DP KO 小鼠在发生肿瘤性胃病变方面有明显的延迟。对人类胃癌组织微阵列的分析表明，与组织学正常的非癌组织相比，癌组织中 DARPP-32 水平较高，且核 STAT3 的免疫染色呈阳性。总之，DARPP-32-IGF1R 信号轴在调节 STAT3 信号中起着关键作用，这是胃肿瘤发生的一个关键步骤。
