Cellular changes in rat urinary bladder carcinomas induced by FANFT: a quantitative electron microscopic analysis

Conditional knockout of fibronectin abrogates mouse mammary gland lobuloalveolar differentiation

Fibronectin (Fn) plays an important part in the branching morphogenesis of salivary gland, lung, and kidney. Here, we examine the effect of the conditional knockout of Fn in the mammary epithelium [Fn(MEp-/-)] on postnatal mammary gland development, using Cre-loxP-mediated gene knockout technology. Our data show that Fn deletion causes a moderate retardation in outgrowth and branching of the ductal tree in 5-week-old mice. These defects are partially compensated in virgin 16-week-old mice. However, mammary glands consisting of Fn-deficient epithelial cells fail to undergo normal lobuloalveolar differentiation during pregnancy. The severity of lobuloalveolar impairment ranged from lobular hypoplasia to aplasia in some cases and was associated with the amount of Fn protein recovered from these glands. Decreased rates of mammary epithelial cell proliferation accounted for delayed ductal outgrowth in virgin and lack of alveologenesis in pregnant Fn(MEp-/-) mice. Concomitant decreased expression of integrin beta(1) (Itgb1) and lack of autophosphorylation of focal adhesion kinase (Fak) suggest that this pathology might, at least in part, be mediated by disruption of the Fn/Itgb1/Fak signaling pathway.

Development of bladder urothelial hyperplasia and carcinoma in portacaval shunted rats is not dependent upon urolithiasis

The pathogenesis of bladder tumors is poorly understood, possibly due to the lack of a suitable experimental model that is drug-free. The aim of the present study was to determine whether bladder tumors could be reproduced reliably in portacaval anastomosis (PCS) rats and whether induction is due to urolithiasis from the development of bladder stones. Eighteen male Sprague-Dawley rats were anaesthetised with isoflurane. Twelve were subjected to portacaval anastomosis and allowed to recover for 38 weeks and the remaining 6 underwent sham control procedures. They were then re-anaesthetised, the anastomosis checked for patency and the bladders and livers excised, fixed, block-mounted, sectioned and stained with haematoxylin and eosin staining for histological examination. None of the control rats developed bladder wall abnormalities of any recognisable nature. However, 5 (42%) of the PCS group had urothelial lesions and bladder stones present and a further 5 (42%) had urothelial lesions alone with no recognisable evidence of bladder stone formation. One PCS rat had bladder stones alone and the remaining PCS rat had an apparently normal bladder epithelium and no stones. Thus, 10 (83%) of the 12 PCS rats developed epithelial lesions and half of these did not display evidence of bladder stone formation. This represented a highly significant difference between the development of bladder stones and the occurrence of urothelial lesions in PCS rats (P > 1.0, chi(2) analysis). Urothelial lesions, therefore, can be reproduced in PCS rats. Their occurrence appears independent of bladder stone formation.

Loss of heterozygosity at 4p16.3 and mutation of FGFR3 in transitional cell carcinoma

4p16.3 has previously been identified as a region of non-random LOH in transitional cell carcinoma, suggesting the presence of a tumour suppressor gene. One candidate within this region is fibroblast growth factor receptor 3 (FGFR3). Germline mutations in FGFR3 are known to cause several autosomal dominant skeletal dysplasias, the severity of which depends on the position and nature of the mutation in the protein. We investigated the frequency and nature of FGFR3 mutations in a panel of transitional cell carcinomas and cell lines and studied the possible link between mutation and loss of heterozygosity (LOH) on 4p16.3. FGFR3 coding sequence from 63 transitional cell carcinomas (TCC) of various stages and grades, and 18 cell lines was analysed by fluorescent SSCP. Samples with abnormal migration patterns were sequenced to identify the mutation or polymorphism. Thirty-one of the 63 tumours had previously been assessed to have LOH at 4p16.3. Twenty-six of the 63 tumours (41%) and 4/18 (22%) of the cell lines had missense mutations in FGFR3. All mutations detected in our panel have been reported in the germline where all apart from one cause lethal conditions. One tumour contained K652Q which has recently been identified in less severe cases of skeletal dysplasia. Tumours with and without LOH at 4p16.3 had mutations in FGFR3 suggesting that these two events are not causally linked. The frequency of FGFR3 mutation indicates that this protein plays an important role in TCC.

Evaluation of human bladder tumors by ultrastructural morphometric techniques

To estimate the malignancy of the human urinary bladder tumors, various cellular components of normal and neoplastic bladder epithelial cells were examined using morphometric techniques at the electron microscopic level. Nuclear to cytoplasmic ratios were found to be 1:5 in normal epithelial cells, 1:4 in superficial grade 1 (G1) tumor cells, 1:3 in superficial grade 2 (G2) tumor cells and 1:2 in invasive grade 3 (G3) tumor cells. Nuclear volumes were largest in G3 tumor cells, but no differences were seen in cell volumes between normal epithelial and tumor cells. The volumes and surface areas of the rough-surfaced endoplasmic reticulum (rER) and lysosomes per cell decreased progressively from G1 to G3 tumor cells. The volume density of tonofilaments was increased in G1, but decreased in G2 and G3 tumor cells. The cisternal thickness of the rER and Golgi complex was also increased in G1 tumor cells. From these results, it was concluded that morphometric analysis may be useful in evaluating the degree of differentiation and invasive potential of human bladder tumor cells in the low and intermediate risk groups.