Reconstitution of amphiregulin-epidermal growth factor receptor signaling in lung squamous cell carcinomas activates PTHrP gene expression and contributes to cancer-mediated diseases of the bone.
Reconstitution of amphiregulin-epidermal growth factor receptor signaling in lung squamous cell carcinomas activates PTHrP gene expression and contributes to cancer-mediated diseases of the bone.
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DOI：
10.1158/1541-7786.mcr-09-0131
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发表时间：
2009-10
期刊：
影响因子：
--
通讯作者：
Foley J
中科院分区：
文献类型：
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作者：
Gilmore JL;Gonterman RM;Menon K;Lorch G;Riese DJ 2nd;Robling A;Foley J
甲状旁腺激素相关蛋白(PTHrP)是恶性副肿瘤综合征体液高钙血症(HHM)的致病因子，也是肺鳞癌常见的溶骨性转移的致病因素。在HHM的两个肺鳞状细胞癌异种移植模型中，抑制自分泌EGFR信号已被证明降低了血浆钙和PTHrP浓度。本研究旨在探讨肺鳞癌细胞系(SCC)中EGFR被激活并刺激PTHrP基因表达的机制。AmphiRegin(AREG)是唯一能在SCC条件培养液中持续检测到的EGFR配体，通过siRNA或沉淀抗体降低其表达，与EGFR靶向抑制一样有效地降低PTHrP mRNA的表达。使用siRNA抑制或AREG释放的上游调节剂，包括TACE、Src/Lck和Gi/o，也可降低PTHrP mRNA的表达。我们确定，阻断自分泌的AREG-EGFR信号不会影响PTHrP mRNA的稳定性。在甲状旁腺激素受体的三个启动子(P1、P2、P3)中，EGFR抑制剂可使P1mRNA降低近100%，而表皮生长因子和三七总皂甙均可使P1mRNA的∼增加5倍。最后，在受体低但表达AREG的细胞系中异位表达EGFR在体外增加了PTHrP的mRNA水平，并诱导了在体内诱导HHM和快速溶骨生长的能力。综上所述，我们提供了AREG刺激EGFR导致高水平PTHrP基因表达的证据，有助于癌症相关的骨病理。
Parathyroid hormone-related protein (PTHrP) is the causative factor of the paraneoplastic syndrome humoral hypercalcemia of malignancy (HHM) and it also contributes to osteolytic metastases, both of which are common complications of squamous carcinomas of the lung. Inhibition of autocrine EGFR signaling has been shown to reduce plasma calcium and PTHrP concentrations in two lung squamous cell carcinoma xenograft models of HHM. The purpose of this study was to investigate the mechanism by which EGFR is activated and stimulates PTHrP gene expression in lung squamous carcinoma cell lines (SCC). Amphiregulin (AREG) was the only EGFR-ligand that could be consistently detected in conditioned media from the SCC lines and reduction of its expression either by siRNA or by precipitating antibodies reduced PTHrP mRNA expression as effectively as EGFR targeted inhibition. Using siRNA knockdown or inhibitors to upstream regulators of AREG shedding including TACE, Src/Lck and Gi/o, also reduced PTHrP mRNA expression. We determined that blockade of autocrine AREG-EGFR signaling does not affect PTHrP mRNA stability. Of the three PTHrP promoters (P1, P2, P3), P1 mRNA could be reduced by nearly 100% with an EGFR inhibitor, and both EGF and AREG stimulated P1 mRNA by ∼5-fold. Finally, ectopic expression of EGFR in a receptor-low but AREG expressing cell line increased PTHrP mRNA levels in vitro, and induced the capability to cause HHM and rapid osteolytic growth in vivo. Taken together, we provide evidence that AREG stimulation of EGFR results in high levels of PTHrP gene expression, contributing to cancer-associated bone pathology.