Tulipano Giovanni, Faggi Lara, Cacciamali Andrea, Spinello Maurizio, Cocchi Daniela, Giustina Andrea
Unit of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy,
Pituitary. 2014 Jun;17(3):203-9. doi: 10.1007/s11102-013-0488-y.
Estrogen receptor α has a role in regulating rat somatolactotroph tumor cell growth (GH3 cells). AMP-activated protein kinase (AMPK) is a metabolic checkpoint which is able to negatively regulate intracellular signaling downstream of growth factors receptors in conditions increasing cellular AMP levels. We have recently reported on the role of AMPK activation in affecting viability and proliferation of GH3 cells. In the present study, we investigated the interplay between ER- and AMPK-pathways. Results can be regarded as relevant to the development of novel multi-targeted pharmacological therapies against pituitary tumors. We confirmed that estradiol (E2) and the ER antagonist fulvestrant exert stimulatory and inhibitory effects, respectively on GH3 cell growth in a competitive manner. The upstream kinase LKB1 is known to phosphorylate and activate AMPK. Here we showed that neither E2 nor fulvestrant caused a downregulation of LKB1 expression and phospho-AMPK levels in GH3 cells. Actually, fulvestrant strongly reduced the phosphorylation of ACC, which is a direct target of AMPK and a known index of AMPK activity. 2-deoxyglucose, a compound reducing glucose utilization, caused an increase in AMPK activity vs baseline and was able to hinder the stimulatory effect of E2 on cell viability, confirming that the exposure of GH3 cells to estrogens does not prevent them from being responsive to the inhibitory activity of compounds activating AMPK. Finally, the AMPK activator AICAR (AMP analog) did not cause further decrease in cell viability in the course of co-treatments with fulvestrant versus fulvestrant alone, in agreement with impaired phospho-AMPK activity in the presence of the anti-estrogen.
雌激素受体α在调节大鼠生长激素催乳素瘤细胞（GH3细胞）生长中发挥作用。AMP激活的蛋白激酶（AMPK）是一种代谢检查点，在细胞内AMP水平升高的情况下，能够负向调节生长因子受体下游的细胞内信号传导。我们最近报道了AMPK激活在影响GH3细胞活力和增殖方面的作用。在本研究中，我们调查了雌激素受体（ER）途径和AMPK途径之间的相互作用。研究结果可能与开发针对垂体肿瘤的新型多靶点药物治疗相关。我们证实，雌二醇（E2）和ER拮抗剂氟维司群分别以竞争性方式对GH3细胞生长发挥刺激和抑制作用。已知上游激酶LKB1可磷酸化并激活AMPK。在此我们表明，E2和氟维司群均未导致GH3细胞中LKB1表达和磷酸化AMPK水平下调。实际上，氟维司群强烈降低了乙酰辅酶A羧化酶（ACC）的磷酸化水平，ACC是AMPK的直接靶点，也是AMPK活性的一个已知指标。2-脱氧葡萄糖是一种降低葡萄糖利用的化合物，与基线相比，它可导致AMPK活性增加，并且能够阻碍E2对细胞活力的刺激作用，这证实了GH3细胞暴露于雌激素下并不妨碍它们对激活AMPK的化合物的抑制活性产生反应。最后，与单独使用氟维司群相比，在与氟维司群联合处理过程中，AMPK激活剂AICAR（AMP类似物）并未导致细胞活力进一步降低，这与存在抗雌激素时磷酸化AMPK活性受损一致。
