Staka Cindy M, Nicholson Robert I, Gee Julia M W
Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff, UK.
Endocr Relat Cancer. 2005 Jul;12 Suppl 1:S85-97. doi: 10.1677/erc.1.01006.
In vitro models of long-term oestrogen deprivation utilise increased oestrogen receptor (ER) and are oestrogen hypersensitive, with emerging evidence that growth factor signalling contributes and interacts with ER. However, such models are commonly derived in the presence of serum growth factors that may force the resistance mechanism. Our new in vitro model, MCF-7X, has thus been developed under conditions of both oestrogen and growth factor depletion. ER expression, serine 118 phosphorylation on this receptor and its transcriptional activity were modestly increased compared to the parental MCF-7 cells, although MCF-7X cells were not oestrogen hypersensitive. Faslodex (0.1 microM) partially decreased ER and its transcriptional activity, with associated decreases in serine 118 phosphorylation. Faslodex inhibited MCF-7X growth by 50% for 10 weeks. Classical growth factor receptors did not impact on MCF-7X growth and only a modest contribution for MAP kinase was revealed using PD98059 (25 microM; 35% inhibition for 3 weeks). However, the phosphatidylinositol-3-OH (PI3)-kinase inhibitor LY294002 (5 microM) inhibited MCF-7X growth by 65% for 10 weeks. In contrast to PD98059, LY294002 also partially-inhibited ER transcriptional activity and decreased serine 167 ER phosphorylation. Co-treatment with faslodex plus LY294002 to decrease activity of both serine 118 and 167 proved superior vs the single agents in decreasing ER transcriptional activity and MCF-7X growth (90% inhibition for 25 weeks). However, triple treatment including PD98059 was required to prevent resistance in MCF-7X, an event dependent on maximal depletion of serine 118 phosphorylation and ER transcriptional activity. Kinases clearly contribute in resistance to oestrogen deprivation, cross-talking with ER signalling via AF-1 phosphorylation. While inhibiting each pathway has potential to treat this state, combined therapy targeting all regulators of ER phosphorylation may be required to block subsequent emergence of resistance.
长期雌激素剥夺的体外模型使用增加的雌激素受体（ER），且对雌激素高度敏感，有新证据表明生长因子信号传导起作用并与ER相互作用。然而，此类模型通常是在可能促使产生耐药机制的血清生长因子存在的情况下构建的。因此，我们的新体外模型MCF-7X是在雌激素和生长因子均缺乏的条件下开发的。与亲代MCF-7细胞相比，ER表达、该受体上丝氨酸118磷酸化及其转录活性适度增加，尽管MCF-7X细胞对雌激素并不高度敏感。氟维司群（0.1微摩尔）部分降低了ER及其转录活性，同时丝氨酸118磷酸化也相应降低。氟维司群在10周内抑制MCF-7X生长达50%。经典生长因子受体对MCF-7X生长没有影响，使用PD98059（25微摩尔；3周内抑制35%）仅显示出丝裂原活化蛋白激酶有适度作用。然而，磷脂酰肌醇-3-羟基（PI3）激酶抑制剂LY294002（5微摩尔）在10周内抑制MCF-7X生长达65%。与PD98059不同，LY294002也部分抑制ER转录活性并降低丝氨酸167 ER磷酸化。氟维司群与LY294002联合处理以降低丝氨酸118和167的活性，在降低ER转录活性和MCF-7X生长方面比单一药物更有效（25周内抑制90%）。然而，需要包括PD98059的三联疗法来防止MCF-7X产生耐药性，这一事件取决于丝氨酸118磷酸化和ER转录活性的最大程度降低。激酶显然在雌激素剥夺耐药中起作用，通过AF-1磷酸化与ER信号通路相互作用。虽然抑制每条途径都有可能治疗这种状态，但可能需要针对ER磷酸化所有调节因子的联合疗法来阻止随后耐药性的出现。
