Growth factors in progression of human esophageal and gastric carcinomas

Abstract

Human esophageal and gastric carcinomas express multi-autocrine growth factors and hormones including epidermal growth factor (EGF), transforming growth factor (TGF)-alpha and beta, platelet-derived growth factor (PDGF), insulin-like growth factor (IGF) and sex hormones. Overexpression of EGF, TGF-alpha and EGF receptor (EGFR) by tumor cells is closely correlated with the tumor invasion and patient prognosis. This is substantiated by the facts that EGF and TGF-alpha act as autocrine growth factors and then induce the expression of mRNAs for multi-growth factors and their receptors (EGF, TGF-alpha, EGFR, ERBB2, PDGF). Moreover, they stimulate the expression of metalloproteinase genes suggesting that EGF and TGF-alpha successively evoke cascade phenomena which are most convenient for tumor progression, invasion and metastasis. On the other hand, multiple oncogene alterations take place in the process of tumor progression. HST-1 and INT-2 genes which is a member of fibroblast growth factor gene family, are amplified in approximately 50% of primary tumors and all the metastatic tumors of esophageal carcinomas. The amplification of ERBB2 gene in metastatic gastric carcinomas is detected more frequently than in primary carcinomas. Overexpression of multi-growth factor-receptor systems might lead to genetical alterations. Scirrhous gastric carcinoma has vast fibrous stroma with rapid and extensive growth and exhibits high malignancy. Its fibrous stroma may account for synchronous overexpression of EGF, TGF-alpha, PDGF, IGF and TGF-beta by tumor cells. Most of well differentiated adenocarcinomas show overexpression of p 185ERBB2 and coexpression of p 185ERBB2, and EGFR evidently correlates with high malignancy. In conclusion, the accumulation and interaction of several growth factors produced by tumor cells are necessary for the progression of human esophageal and gastric carcinomas. They may be attributed to genetic changes including activation of oncogenes, inactivation and deletion of anti-oncogenes and transcriptional regulatory sequences.