Signaling of ERBB receptor tyrosine kinases promotes neuroblastoma growth in vitro and in vivo

Abstract

BACKGROUND: ERBB receptor tyrosine kinases can mediate proliferation, migration, adhesion, differentiation, and survival in many types of cells and play critical roles in many malignancies. Recent reports suggest a role for EGFR signaling in proliferation and survival of neuroblastoma, a common form of pediatric cancer that often has an extremely poor outcome. METHODS: The authors examined ERBB family expression in neuroblastoma cell lines and patient samples by flow cytometry, western blot, and quantitative real time polymerase chain reaction (Q-PCR). Response to ERBB inhibition was assessed in vitro by cell-cycle analysis and western blot and in vivo by serial tumor-size measurements. RESULTS: A panel of neuroblastoma cell lines and primary patient tumors expressed EGFR, HER-3, and HER-4, with HER-2 in some tumors. HER-4 mRNA was expressed predominantly in cleavable isoforms. Whereas EGFR inhibition with erlotinib and pan-ERBB inhibition with CI-1033 inhibited EGFinduced phosphorylation of EGFR, AKT, and ERK1/2, only CI-1033 induced growth inhibition and dose-dependent apoptosis in vitro. Both CI-1033 and erlotinib treatment of neuroblastoma xenograft tumors resulted in decreased tumor growth in vivo, although CI-1033 was more effective. In vivo expression of EGFR was observed predominantly in vascular endothelial cells. CONCLUSIONS: Pan-ERBB inhibition is required for ERBB-related neuroblastoma apoptosis in vitro, although EGFR contributes indirectly to tumor growth in vivo. Inhibition of EGFR in endothelial cells may be an important aspect of erlotinib's impact on neuroblastoma growth in vivo. Our results suggest that non-EGFR ERBB family members contribute directly to neuroblastoma growth and survival, and pan-ERBB inhibition represents a potential therapeutic target for treating neuroblastoma.

Expression and significance of HER family receptors in neuroblastic tumors

“…They explained the lack of cell surface receptor in some cases by receptor recycling. They also suggested the influence of EGFR on tumor cells-stromal interactions and angiogenesis [19]. In our study, EGFR labeling was membranous in poorly differentiated NB, like in control fetal autonomic ganglia.…”

“…HER receptors, which control cell invasion and motility, are also involved in cancer metastasis [11,26]. EGFR expression in NT clinical samples was analyzed only in a few studies on rather small series [18,19,[27][28][29]. Up till now no clinicopathological correlations of EGFR expression have been described in NT [18,27].…”

“…Ho et al [18] found mRNA EGFR expression up to the level of fetal brain in majority of examined NB cell lines and in 18 tumor samples. Moreover, in several studies it was shown that EGFR mediated proliferation of NB cells can be selectively inhibited by gefitinib [18,19,28,29]. Recently, Richards and co-workers [19] revealed frequent EGFR expression based on western blot and by flow cytometry analyses.…”

“…Moreover, in several studies it was shown that EGFR mediated proliferation of NB cells can be selectively inhibited by gefitinib [18,19,28,29]. Recently, Richards and co-workers [19] revealed frequent EGFR expression based on western blot and by flow cytometry analyses. They explained the lack of cell surface receptor in some cases by receptor recycling.…”

“…The role of the HER family, which is involved in embryonic development of the sympathetic nervous system [14][15][16], is neither well explored nor understood in NT [18,19]. The associations between HERs expression with the characteristics of tumors and their prognostic significance remain not established.…”