Basement membrane and carcinogenesis: ultrastructural observations in the basement membrane of the bladder epithelium in rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)

Interstitial stroma and carcinogenesis: ultrastructural observations in the rat bladder treated with N-butyl-N-(4-hydroxybutyl)nitrosamine

This study describes ultrastructural alterations of the interstitial stroma in the rat bladder epithelium during N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced bladder carcinogenesis using scanning (SEM) and transmission (TEM) electron microscopy with NaOH treatment. The results obtained with SEM demonstrated the occurrence and development of stroma protrusions which exhibited pipe-like structures in the rat bladder epithelium following administration of BBN. Number and size of blood vessel sections also gradually increased both in the stroma and within the layer of the proliferated epithelial cells as examined by light microscopy (LM) and TEM. In this study stroma alterations were not only observed in malignant lesions of rat bladder, but hyperplastic lesions were also accompanied by stroma alterations. It is suggested that: (1) the interstitial stroma of the rat bladder epithelium may exhibit pathological changes in structure and these changes may correlate with the progression of epithelial cell proliferation following administration of BBN and (2) one of the most important alterations in the stroma is the occurrence of neovascularization, which may induce structural modification of the stroma in the processes of bladder tumor growth and development.

Enhanced gene expression of transforming growth factor-alpha and c-met in rat urinary bladder cancer

To investigate the roles of growth factors in bladder cancer, changes in the expression of messenger RNAs (mRNAs) for several growth factors and their receptors were examined during rat bladder carcinogenesis induced with N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN). Northern blot analysis showed that the contents of mRNAs for transforming growth factor-alpha (TGF-alpha) and c-met/hepatocyte growth factor (HGF) receptor increased with BBN treatment. Epidermal growth factor (EGF) receptor mRNA was hardly affected by the treatment; while mRNA for fibroblast growth factor (FGF) receptor 1 and transforming growth factor-beta (TGF-beta) type II receptor decreased with BBN treatment. A rat bladder tumor cell line, NBT-II, expressed both TGF-alpha and c-met mRNAs, and HGF showed apparent scattering and growth-stimulating effects on the cells. These results indicate the possibility that TGF-alpha produced by a bladder cancer, in addition to urinary EGF, plays a role in the development of bladder cancer, and that enhanced cell motility due to activation of the c-met/HGF receptor participates in the invasion and metastasis of the cancer cells.

Morphological changes of microvilli on different surfaces of epithelial cells in the rat bladder treated with N-butyl-N-(4-hydroxybutyl) nitrosamine

This study investigates morphological changes of microvilli occurring on different surfaces of epithelial cells, including luminal surfaces, intercellular surfaces, and basal cell surfaces adjacent to the basement membrane (BM), in the rat bladder treated with N-butyl-N(4-hydroxybutyl) nitrosamine (BBN) by transmission electron microscopy (TEM). The present results showed that the microvilli were observed not only on the luminal surfaces of epithelial cells but also on the intercellular surfaces and basal cell surfaces adjacent to the BM following administration of BBN. There were a variety of morphological changes of microvilli on the luminal surfaces, intercellular surfaces and basal cell surfaces adjacent to the BM, respectively. It is suggested that the microvilli occurring on the luminal surfaces may not represent characteristics of the microvilli occurring on the intercellular surfaces and on the basal cell surfaces adjacent to the BM, and that occurrence of the microvilli on the epithelial cell surfaces may reflect a higher metabolic activity of proliferative epithelial cells and may play an important role in the processes of tumor growth during bladder carcinogenesis.