Lichtner R B, Menrad A, Sommer A, Klar U, Schneider M R
Research Laboratories of Schering AG, 13342 Berlin, Germany.
Cancer Res. 2001 Aug 1;61(15):5790-5.
Several inhibitors of EGF receptor (EGFR) tyrosine kinase activity have been developed that compete with ATP at its binding site such as the quinazolines PD 153035 and ZD 1839 or the 4,5-dianilino-phthalimides DAPH1 and DAPH2. When tested on human A431 cells, the quinazolines completely blocked EGF-induced receptor phosphorylation at 100 nM, whereas it was inhibited by DAPH1 and DAPH2 by only 20% at 3 microM. Quinazoline-treated A431 as well as tumor cells expressing less EGFR (A549, MDA MB 231, and T47D) bound 3- to 6-fold more (125)I-labeled EGF than untreated intact control cells. Scatchard analysis revealed the disappearance of low- and high-affinity EGFR on A431 cells upon PD 153035 treatment. A single receptor class of intermediate ligand binding affinity emerged and its number corresponded to the sum of the two classes. DAPH1 and DAPH2 did not change ligand binding properties of EGFR. PD 153035 exerted the most potent effects on EGF binding to A431 or on inhibiting EGF-stimulated growth of rat MTLn3 cells at low ligand concentrations. Cross-linking of EGFR on PD 153035-treated A431 cells indicated the formation of inactive dimers that further increased upon addition of EGF. Chemical cross-linking of (125)I-labeled EGF to PD 153035-treated A431 cells revealed increased binding to monomeric and dimeric EGFR. Thus, the quinazolines sequestered EGFR plus the ligand into inactive receptor/ligand complexes. This novel mode of action of quinazoline tyrosine kinase inhibitors may be the basis for their extraordinary potency especially in conditions when the ligand is present in limiting amounts.
已经开发出几种表皮生长因子受体（EGFR）酪氨酸激酶活性抑制剂，它们在ATP结合位点与ATP竞争，如喹唑啉类的PD 153035和ZD 1839，或4,5 - 二苯胺基邻苯二甲酰亚胺类的DAPH1和DAPH2。在人A431细胞上进行测试时，喹唑啉类在100 nM时完全阻断了表皮生长因子（EGF）诱导的受体磷酸化，而DAPH1和DAPH2在3 μM时仅抑制20%。用喹唑啉处理的A431细胞以及表达较少EGFR的肿瘤细胞（A549、MDA MB 231和T47D）与未处理的完整对照细胞相比，结合的（125）I标记的EGF多3至6倍。Scatchard分析显示，用PD 153035处理后，A431细胞上的低亲和力和高亲和力EGFR消失。出现了一类具有中等配体结合亲和力的单一受体，其数量相当于两类受体数量之和。DAPH1和DAPH2没有改变EGFR的配体结合特性。在低配体浓度下，PD 153035对EGF与A431细胞的结合或对抑制大鼠MTLn3细胞的EGF刺激生长具有最显著的作用。在PD 153035处理的A431细胞上对EGFR进行交联表明形成了无活性的二聚体，在加入EGF后进一步增加。将（125）I标记的EGF化学交联到PD 153035处理的A431细胞上显示与单体和二聚体EGFR的结合增加。因此，喹唑啉类将EGFR与配体隔离到无活性的受体/配体复合物中。喹唑啉酪氨酸激酶抑制剂的这种新作用模式可能是其非凡效力的基础，特别是在配体存在量有限的情况下。
