The Hormel Institute, University of Minnesota, Austin, MN, USA.
Department of Molecular Medicine, Mayo Clinic, Rochester, MN, USA.
Br J Cancer. 2020 Sep;123(5):819-832. doi: 10.1038/s41416-020-0923-6. Epub 2020 Jun 5.
Small cell lung cancer (SCLC) is the most aggressive form of lung cancer, and new molecular insights are necessary for prognostic and therapeutic advances.
Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) and its N-terminally truncated splice variant, t-DARPP, were stably overexpressed or ablated in human DMS-53 and H1048 SCLC cells. Functional assays and immunoblotting were used to assess how DARPP-32 isoforms regulate SCLC cell growth, proliferation, and apoptosis. DARPP-32-modulated SCLC cells were orthotopically injected into the lungs of SCID mice to evaluate how DARPP-32 and t-DARPP regulate neuroendocrine tumour growth. Immunostaining for DARPP-32 proteins was performed in SCLC patient-derived specimens. Bioinformatics analysis and subsequent transcription assays were used to determine the mechanistic basis of DARPP-32-regulated SCLC growth.
We demonstrate in mice that DARPP-32 and t-DARPP promote SCLC growth through increased Akt/Erk-mediated proliferation and anti-apoptotic signalling. DARPP-32 isoforms are overexpressed in SCLC patient-derived tumour tissue, but undetectable in physiologically normal lung. Achaete-scute homologue 1 (ASCL1) transcriptionally activates DARPP-32 isoforms in human SCLC cells.
We reveal new regulatory mechanisms of SCLC oncogenesis that suggest DARPP-32 isoforms may represent a negative prognostic indicator for SCLC and serve as a potential target for the development of new therapies.
小细胞肺癌（SCLC）是最具侵袭性的肺癌类型，需要新的分子见解来促进预后和治疗进展。
多巴胺和 cAMP 调节磷蛋白，Mr32000（DARPP-32）及其 N 端截断的剪接变体 t-DARPP，在人 DMS-53 和 H1048 SCLC 细胞中稳定过表达或敲除。采用功能测定和免疫印迹法评估 DARPP-32 异构体如何调节 SCLC 细胞的生长、增殖和凋亡。将 DARPP-32 调节的 SCLC 细胞原位注射到 SCID 小鼠的肺部，以评估 DARPP-32 和 t-DARPP 如何调节神经内分泌肿瘤的生长。对 SCLC 患者来源标本进行 DARPP-32 蛋白的免疫染色。进行生物信息学分析和随后的转录测定，以确定 DARPP-32 调节 SCLC 生长的机制基础。
我们在小鼠中证明，DARPP-32 和 t-DARPP 通过增加 Akt/Erk 介导的增殖和抗凋亡信号促进 SCLC 生长。DARPP-32 异构体在 SCLC 患者来源的肿瘤组织中过度表达，但在生理正常的肺组织中无法检测到。achaete-scute 同源物 1（ASCL1）在人 SCLC 细胞中转录激活 DARPP-32 异构体。
我们揭示了 SCLC 发生的新调控机制，表明 DARPP-32 异构体可能是 SCLC 的一个负预后指标，并可能成为开发新疗法的潜在靶点。
