Zhou Hong, Kim Yeon-Shil, Peletier Aaron, McCall Wes, Earp H Shelton, Sartor Carolyn I
Department of Radiation Oncology, University of North Carolina School of Medicine and UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA.
Int J Radiat Oncol Biol Phys. 2004 Feb 1;58(2):344-52. doi: 10.1016/j.ijrobp.2003.09.046.
Two members of the epidermal growth factor receptor family, EGFR and HER2, have been implicated in radioresistance in breast cancer and other malignancies. To gauge the potential clinical utility of targeting both EGFR and HER2 to control growth and radiosensitize human breast cancers, we examined the effect of a dual EGFR/HER2 inhibitor, GW572016, on the proliferation and radiation response of either EGFR- or HER2-overexpressing human breast cancer cell lines.
Primary human breast cancer cell lines that endogenously overexpress EGFR or HER2 and luminal mammary epithelial H16N2 cells stably transfected with HER2 were evaluated for the effect of GW572016 on inhibition of ligand-induced or constitutive receptor phosphorylation, proliferation, radiosensitization, and inhibition of downstream signaling.
GW572016 inhibited constitutive and/or ligand-induced EGFR or HER2 tyrosine phosphorylation of all five cell lines, which correlated with the antiproliferative response in all but one cell line. GW572016 radiosensitized EGFR-overexpressing cell lines, but HER2-overexpressing cells were unable to form colonies after brief exposure to GW572016 even in the absence of radiation, and thus could not be evaluated for radiosensitization. One cell line was resistant to the antiproliferative and radiosensitizing effects of GW572016, despite receptor inhibition. Exploration of potential mechanisms of resistance in SUM185 cells revealed failure of GW572016 to inhibit downstream ERK and Akt activation, despite inhibition of HER2 phosphorylation. In contrast, sensitive HER2-overexpressing cell lines demonstrated inhibition of both ERK and Akt phosphorylation.
GW572016 potently inhibits receptor phosphorylation in either EGFR- or HER2-overexpressing cell lines and has both antiproliferative and radiosensitizing effects. Resistance to GW572016 was not due to a lack of receptor inhibition, but rather with a lack of inhibition of ERK and Akt, suggesting that measurement of inhibition of crucial signaling pathways may better predict response than inhibition of receptor phosphorylation. The SUM185 cell line provides a valuable model for studying mechanisms of resistance of EGFR/HER2 inhibitor therapy.
表皮生长因子受体家族的两个成员，即表皮生长因子受体（EGFR）和人表皮生长因子受体2（HER2），与乳腺癌及其他恶性肿瘤的放射抗性有关。为了评估同时靶向EGFR和HER2以控制人乳腺癌生长并使其对放疗敏感的潜在临床效用，我们检测了双靶点EGFR/HER2抑制剂GW572016对过表达EGFR或HER2的人乳腺癌细胞系增殖及辐射反应的影响。
评估了内源性过表达EGFR或HER2的原发性人乳腺癌细胞系，以及稳定转染HER2的管腔型乳腺上皮H16N2细胞，检测GW572016对配体诱导的或组成型受体磷酸化的抑制作用、增殖、放射增敏作用以及对下游信号传导的抑制作用。
GW572016抑制了所有5种细胞系组成型和/或配体诱导的EGFR或HER2酪氨酸磷酸化，除一个细胞系外，这与抗增殖反应相关。GW572016使过表达EGFR的细胞系对放疗增敏，但过表达HER2的细胞即使在无辐射情况下短暂暴露于GW572016后也无法形成集落，因此无法评估其放射增敏作用。尽管受体受到抑制，但有一个细胞系对GW572016的抗增殖和放射增敏作用具有抗性。对SUM185细胞系中潜在抗性机制的探索显示，尽管HER2磷酸化受到抑制，但GW572016未能抑制下游的细胞外信号调节激酶（ERK）和蛋白激酶B（Akt）激活。相比之下，敏感的过表达HER2的细胞系显示ERK和Akt磷酸化均受到抑制。
GW572016能有效抑制过表达EGFR或HER2的细胞系中的受体磷酸化，具有抗增殖和放射增敏作用。对GW572016的抗性并非由于缺乏受体抑制，而是由于缺乏对ERK和Akt的抑制，这表明检测关键信号通路的抑制作用可能比检测受体磷酸化的抑制作用能更好地预测反应。SUM185细胞系为研究EGFR/HER2抑制剂治疗的抗性机制提供了一个有价值的模型。
