Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
Br J Pharmacol. 2011 Oct;164(3):1026-40. doi: 10.1111/j.1476-5381.2011.01384.x.
AM251 is an inverse agonist of the cannabinoid 1 receptor (CB(1)R) that can exert 'off-target' effects in vitro and in CB(1)R knock-out mice. AM251 is also potent at modulating tumour cell growth, suggesting that growth factor-mediated oncogenic signalling could be regulated by AM251. Since dysregulation of the EGF receptor has been associated with carcinogenesis, we examined AM251 regulation of EGF receptor (EGFR) expression and function.
The various biological functions of AM251 were measured in CB(1)R-negative human cancer cells. Pharmacological and genetic approaches were used to validate the data.
The mRNA levels for EGFR and its associated ligands, including HB-EGF, were induced several fold in PANC-1 and HCT116 cells in response to AM251. This event was associated with enhanced expression of EGFR on the cell surface with concomitant increase in EGF-induced cellular responses in AM251-treated cells. Exposure to XCT790, a synthetic inverse agonist of the orphan nuclear oestrogen-related receptor α (ERRα), also induced EGFR and HB-EGF expression to the same extent as AM251, whereas pretreatment with the ERRα-selective agonist, biochanin A, blunted AM251 actions. AM251 promoted the degradation of ERRα protein without loss of the corresponding mRNA. Knock-down of ERRα by siRNA-based approach led to constitutive induction of EGFR and HB-EGF levels, and eliminated the biological responses of AM251 and XCT790. Finally, AM251 displaced diethylstilbestrol prebound to the ligand-binding domain of ERRα.
AM251 up-regulates EGFR expression and signalling via a novel non-CB(1)R-mediated pathway involving destabilization of ERRα protein in selected cancer cell lines.
AM251 是大麻素 1 型受体（CB1R）的反向激动剂，在体外和 CB1R 敲除小鼠中具有“脱靶”作用。AM251 也能有效地调节肿瘤细胞的生长，这表明生长因子介导的致癌信号可能受到 AM251 的调节。由于表皮生长因子受体（EGFR）的失调与癌变有关，我们研究了 AM251 对 EGFR 表达和功能的调节作用。
在 CB1R 阴性的人类癌细胞中测量 AM251 的各种生物学功能。采用药理学和遗传学方法验证数据。
在 PANC-1 和 HCT116 细胞中，AM251 诱导 EGFR 及其相关配体（包括 HB-EGF）的 mRNA 水平数倍增加。这一事件与 EGFR 在细胞表面的表达增加有关，同时在 AM251 处理的细胞中，EGF 诱导的细胞反应也增加。暴露于 XCT790（孤儿核雌激素相关受体α（ERRα）的合成反向激动剂）也会诱导 EGFR 和 HB-EGF 的表达，与 AM251 相同程度，而用 ERRα 选择性激动剂生物chanin A 预处理则削弱了 AM251 的作用。AM251 促进 ERRα 蛋白的降解，而不丢失相应的 mRNA。通过 siRNA 方法敲低 ERRα 会导致 EGFR 和 HB-EGF 水平的持续诱导，并消除 AM251 和 XCT790 的生物学反应。最后，AM251 置换了与 ERRα 配体结合域结合的己烯雌酚。
在选定的癌细胞系中，AM251 通过一种新的非 CB1R 介导的途径上调 EGFR 表达和信号转导，该途径涉及 ERRα 蛋白的不稳定。
