TY - JOUR
T1 - Overexpression of epidermal growth factor receptor in urothelium elicits urothelial hyperplasia and promotes bladder tumor growth
AU - Cheng, Jin
AU - Huang, Hongying
AU - Zhang, Zhong Ting
AU - Shapiro, Ellen
AU - Pellicer, Angel
AU - Sun, Tung Tien
AU - Wu, Xue Ru
PY - 2002/7/15
Y1 - 2002/7/15
N2 - Although urothelium is constantly bathed in high concentrations of epidermal growth factor (EGF) and most urothelial carcinomas overexpress EGF receptor (EGFr), relatively little is known about the role of EGFr signaling pathway in urothelial growth and transformation. In the present study, we used the uroplakin II gene promoter to drive the urothelial overexpression of EGFr in transgenic mice. Three transgenic lines were established, all expressing a higher level of the EGFr mRNA and protein in the urothelium than the nontransgenic controls. The overexpressed EGFr was functionally active because it was autophosphorylated, and its downstream mitogen-activated protein kinases were highly activated. Phenotypically, the urinary bladders of all transgenic lines developed simple urothelial hyperplasia that was strongly positive for proliferative cell nuclear antigen and weakly positive for bromodeoxyuridine incorporation. When coexpressed with the activated Ha-ras oncogene in double transgenic mice, EGFr had no apparent tumor-enhancing effects over the urothelial hyperplastic phenotype induced by Ha-ras oncogene. However, when coexpressed with the SV40 large T antigen, EGFr accelerated tumor growth and converted the carcinoma in situ of the SV40T mice into high-grade bladder carcinomas, without triggering tumor invasion. Our studies indicate that urothelial overexpression of EGFr can induce urothelial proliferation but not frank carcinoma formation. Our results also suggest that, whereas EGFr and Ha-ras, both of which act in the same signal transduction cascade, stimulated urothelial hyperplasia, they were not synergistic in urothelial tumorigenesis, and EGFr overexpression can cooperate with p53 and pRB dysfunction (as occurring in SV40T transgenic mice) to promote bladder tumor growth.
AB - Although urothelium is constantly bathed in high concentrations of epidermal growth factor (EGF) and most urothelial carcinomas overexpress EGF receptor (EGFr), relatively little is known about the role of EGFr signaling pathway in urothelial growth and transformation. In the present study, we used the uroplakin II gene promoter to drive the urothelial overexpression of EGFr in transgenic mice. Three transgenic lines were established, all expressing a higher level of the EGFr mRNA and protein in the urothelium than the nontransgenic controls. The overexpressed EGFr was functionally active because it was autophosphorylated, and its downstream mitogen-activated protein kinases were highly activated. Phenotypically, the urinary bladders of all transgenic lines developed simple urothelial hyperplasia that was strongly positive for proliferative cell nuclear antigen and weakly positive for bromodeoxyuridine incorporation. When coexpressed with the activated Ha-ras oncogene in double transgenic mice, EGFr had no apparent tumor-enhancing effects over the urothelial hyperplastic phenotype induced by Ha-ras oncogene. However, when coexpressed with the SV40 large T antigen, EGFr accelerated tumor growth and converted the carcinoma in situ of the SV40T mice into high-grade bladder carcinomas, without triggering tumor invasion. Our studies indicate that urothelial overexpression of EGFr can induce urothelial proliferation but not frank carcinoma formation. Our results also suggest that, whereas EGFr and Ha-ras, both of which act in the same signal transduction cascade, stimulated urothelial hyperplasia, they were not synergistic in urothelial tumorigenesis, and EGFr overexpression can cooperate with p53 and pRB dysfunction (as occurring in SV40T transgenic mice) to promote bladder tumor growth.
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M3 - Article
C2 - 12124355
AN - SCOPUS:0037099540
SN - 0008-5472
VL - 62
SP - 4157
EP - 4163
JO - Cancer research
JF - Cancer research
IS - 14
ER -