Microfilament bundles in transformed mouse CLID x transformed CHO cell hybrids. Correlation with tumorigenicity in nude mice

Malignancy-related characteristics of wild type and drug-resistant Chinese hamster ovary cells

Chinese hamster ovary (CHO) cell lines are a very popular cell model for a wide range of studies but are often misused experimentally as a substitute for normal cells. Although CHO was originally derived from normal tissue, the cell lines studied here, including the parental wild type, have many characteristics which indicate that they have undergone malignant transformation. Biological properties associated with malignancy were investigated in this study on wild type CHO cells and 4 drug resistant sublines, EOT, Col R-22, Pod R11-6, and Vin R-1. We report evidence of tumorigenicity in experimental animals, invasive capacity, in vivo and in vitro, protease release by 2 of the cell lines, features related to drug resistance in the mutant sublines, and numerical and structural chromosomal abnormalities.

Comparison of major cytoskeletons among normal human fibroblasts, immortal human fibroblasts transformed by exposure to Co-60 gamma rays, and the latter cells made tumorigenic by treatment with Harvey murine sarcoma virus

Immortally transformed human fibroblasts in general acquire an epithelial shape, while normal human fibroblasts demonstrate a spindle-shaped feature. In order to investigate this difference, three types of major cytoskeletal elements, namely, F-actin, tubulin, and vimentin of immortal human fibroblasts were morphologically compared with those of normal human fibroblasts. As a result, a significant difference was observed in the distribution and in the number of F-actin fibers between immortal and normal fibroblasts. The cells of three immortally transformed fibroblast lines, KMST-6, WI-38 VA-13, and SUSM-1, showed a striking reduction in the number, and an altered pattern of organization, of actin fibers. On the other hand, in the normal fibroblasts, actin fibers ran parallel to each other along the long axis of the cells. Tubulin and vimentin showed no significant difference between the immortal and normal cells. Our present data show that the morphological changes seen in the immortally transformed cells are due to the disorganization and the decrease in number of actin fibers. Interestingly, both the immortal cells (KMST-6), which were not tumorigenic, and the Harvey murine sarcoma virus-transformed KMST-6 cells, which were tumorigenic and demonstrated an enhanced expression of the ras gene, revealed an overall similarity in the organization pattern and the number of actin fibers. These findings seem to indicate that the immortally transformed cells have already acquired some cancer characteristics.

Aggregates of cytofilaments as the cause of the appearance of hyaline tumor cells

Cells resembling the hyaline cells of mixed salivary tumors have been identified in islet cell tumors, basal cell carcinoma, epithelioid leiomyoma, and an hepatic apudoma. Cytofilaments of intermediate size were present in these cells of electron microscopy and the distinctive hyaline appearance of cytoplasm is ascribed to large aggregates of these.