Purpose

Recent studies have reported important roles of dopamine receptors in the early development and progression of glioblastoma (GBM). Here, we tested the antitumor activity of a Dopamine receptor D1 (DRD1) agonist, either alone or in combination with temozolomide (TMZ) on GBM cells.

Methods

Immunofluorescence, immunohistochemistry and Western blotting were used to detect dopamine receptor expression in primary human GBM tissues. In addition, clinical data of GBM patients downloaded from The Cancer Genome Atlas (TCGA) were analyzed. Image-based tracking analysis of LC3 using a mCherry-eGFP-LC3 plasmid was utilized to monitor autophagic flux. Transmission electron microscopy (TEM) was used to visualize aggregation of autophagosomes/autolysosomes. Finally, DRD1 agonist (SKF83959)-induced inhibition of GBM growth was assessed in vitro and in vivo.

Results

Positive DRD1 expression was observed in human GBM tissues and found to be related with a good clinical outcome. DRD1 activation specifically inhibited GBM cell growth and significantly disrupted autophagic flux, which led to tumor cell death. Moreover, we found that DRD1 agonist treatment inhibited auto-lysosomal degradation in GBM cells and that this process was calcium overload dependent and related to inhibition of mammalian target of rapamycin (mTOR). Finally, we found that DRD1 agonist and TMZ co-treatment yielded a synergistic therapeutic effect both in vivo and in vitro.

Conclusions

From our data we conclude that DRD1 activation inhibits GBM cell growth and may serve as an alternative avenue for the design of future GBM therapies.

中文翻译：

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多巴胺受体 D1 的激活通过调节自噬活性抑制胶质母细胞瘤的致瘤性。

目的

最近的研究报告了多巴胺受体在胶质母细胞瘤 (GBM) 的早期发展和进展中的重要作用。在这里，我们测试了多巴胺受体 D1 (DRD1) 激动剂单独或与替莫唑胺 (TMZ) 组合对 GBM 细胞的抗肿瘤活性。

方法

免疫荧光、免疫组织化学和蛋白质印迹法用于检测原代人 GBM 组织中多巴胺受体的表达。此外，还分析了从癌症基因组图谱 (TCGA) 下载的 GBM 患者的临床数据。使用 mCherry-eGFP-LC3 质粒对 LC3 进行基于图像的跟踪分析来监测自噬通量。透射电子显微镜（TEM）用于观察自噬体/自体溶酶体的聚集。最后，在体外和体内评估了DRD1 激动剂 (SKF83959) 诱导的 GBM 生长抑制。

结果

在人类 GBM 组织中观察到阳性 DRD1 表达，发现与良好的临床结果相关。DRD1 激活特异性抑制 GBM 细胞生长并显着破坏自噬通量，从而导致肿瘤细胞死亡。此外，我们发现 DRD1 激动剂治疗抑制了 GBM 细胞中的自溶酶体降解，并且该过程是钙过载依赖性的，并且与哺乳动物雷帕霉素靶标 (mTOR) 的抑制有关。最后，我们发现 DRD1 激动剂和 TMZ 共同治疗在体内和体外产生了协同治疗效果。

结论

根据我们的数据，我们得出结论，DRD1 激活抑制 GBM 细胞生长，并可能作为设计未来 GBM 疗法的替代途径。