Malignant behaviour of three adenovirus-2-transformed brain cell lines and their methyl cellulose-selected sub-clones

The early appearance of fibronectin in the course of metastatic tumor growth in lymph nodes

In order to study structural changes in the lymph node architecture in the course of metastatic involvement by carcinoma, 70 axillary lymph nodes of 45 female patients affected by breast carcinoma were examined. The following growth pattern of the metastasis was observed: (1) Involvement of vasa afferentia and (marginal) sinuses; (2) lysis of sinus wall and infiltration, causing replacement and lysis of reticulin fibres; (3) appearance of fibrillary fibronectin (FN) as the first noticeable sign of tumor stroma; (4) immigration of fibroblasts along these fibres, appearance of argyrophilic fibres codistributed with fibrillary FN; (5) formation of the complete tumor stroma, neovessels included. The appearance of FN is thus the first step of stroma formation and is interpreted as an "in situ" precipitation of soluble plasma FN.

Lack of correlation between metastasis of human rectal carcinoma and the absence of stromal fibronectin

In a retrospective study we have used an immunoperoxidase procedure to localize the glycoprotein fibronectin in human rectal carcinomas, concentrating on tumour invading thick-walled extramural veins. Fibronectin was present in 29 out of 38 cases, in connective tissue stroma, and was not in direct association with the tumour cells, except in areas of necrosis. We found no correlation between the presence or absence of stromal fibronectin and (1) the degree of cellular differentiation within the tumour, (2) tumour progression (Dukes' classification) (3) the subsequent development of metastases and (4) patient longevity. OUr results do not support the conclusions from in vitro studies (Smith et al., 1979) that the metastatic potential of carcinomas may be partly determined by the ability of tumour cells to synthesize pericellular fibronectin.

Fibronectin in human solid tumors

Fibronectin in human solid tumors was studied by indirect immunofluorescence staining of biopsy material. Altogether 73 tumors were examined, comprising 12 sarcomas, 3 melanomas 1 reticulum cell sarcoma, 39 carcinomas, 6 benign soft-tissue tumors and 12 benign epithelial tumors. In all sarcomas the individual tumor cells were surrounded by a network of fibronectin which was continuous with the stroma. The distribution of fibronectin was similar in the benign soft-tissue tumors. In contrast, no fibronectin was detected in the individual carcinoma cells or in their periphery. However, the reactive connective tissue stroma of carcinomas was strongly connective tissue stroma of carcinomas was strongly positive for fibronectin. This was true also for the stroma of benign epithelial tumors. These results show that, contrary to the situation in cell culture, in vivo sarcoma cells and benign soft-tissue tumor cells contain fibronectin in their pericellular matrix. On the other hand, fibronectin can be used to distinguish carcinomas from sarcomas in vivo.

Tumorigenicity and in vitro characteristics of rat liver epithelial cells and their adenovirus-transformed derivatives

Cloned and uncloned epithelial cultures were established from the liver of a 3-week-old AS rat. These epithelial cultures were neither tumorigenic nor did they display anchorage-independent growth. One of the clones was cytogenetically normal after 53 in vitro passages (approximately 200 population doublings after cloning). Eight transformed lines were isolated from the liver epithelial cells after infection with adenovirus type 12 (Ad-12). Five of these produced typical Ad12 T-antigen, whereas three appeared to be T-antigen-negative. All were tumorigenic in newborn syngeneic rats. The T-antigen-positive transformed lines produced anaplastic-epithelial tumors, whereas the T-antigen-negative transformed lines produced adenocarcinomas. Although all the transformed lines were tumorigenic, some were fibronectin-positive while others produced no detectable fibronectin. The normal (untransformed) epithelial cells produced fibronectin. These results are interesting for two reasons: (1) there are relatively few reports of fibronectin on epithelial cells and (2) they emphasize the view that there is no absolute correlation between reduced fibronectin and tumorigenicity in transformed cells. The transformed lines displayed in vitro characteristics similar to those of transformants derived from embryonic and fibroblastic cell strains, notably, increased saturation density and changes in cellular morphology. Some of the transformed cell lines, but not all, displayed anchorage-independent growth. All the transformed cell lines were picked from multi-layered foci so that morphological criteria (i.e. piling-up focus) for isolating transformants from the epithelial cultures were similar as in embryonic and fibroblastic transforming cell systems. With the new cell system we have developed we can, using the same epithelial cell line (clone C3), study both virus transformation and virus mutagenesis.

Possible role of fibronectin in malignancy

Frozen sections of tumors induced by injecting virally transformed cells into animals were stained for fibronectin by immunofluorescence. Many tumor cell lines do not express fibronectin in tumors in situ even though some of them express fibronectin in culture. Cell shape and hormones appear to influence the expression of fibronectin in culture; however, it is unclear how fibronectin expression is regulated in vivo.