The influence of the presence of adenovirus 5 E1a and E1b sequences on the pathology of rat embryonic fibroblasts transfected with activated c-Ha-ras and v-ras

Metastasis of C1300 and TBJ murine neuroblastomas correlates with expression of matrix metalloproteinases

Because metalloproteinases, specifically type IV collagenases, may mediate metastasis, 72- and 92-kDa collagenase activities were evaluated in two murine neuroblastoma cell lines: non-metastatic C1300 and metastatic TBJ. Zymogram analysis demonstrated that 72- and 92-kDa collagenases were associated only with metastatic TBJ. Three human neuroblastoma cell lines were then evaluated by zymogram and Western blot analyses: 72-kDa collagenase was found in metastatic SK-N-SH and IMR-32, but not in SK-N-MC, which may be a peripheral neuroectodermal tumor and not a neuroblastoma. Therefore, 72- and 92-kDa collagenases may be markers of metastasis in neuroblastoma and may aid in differentiation from other small blue cell tumors.

Reduction of translation initiation factor 4E decreases the malignancy of ras-transformed cloned rat embryo fibroblasts

Expression of the T24ras oncogene induces malignancy (tumor growth, invasion and metastasis) in cloned rat embryo fibroblasts (CREF T24). In CREF T24, the rate of phosphorylation of eukaryotic translation initiation factor 4E (eIF-4E) is increased, resulting in increased protein synthesis rates. We have recently shown that reducing the protein levels of eIF-4E in CREF T24 (AS4E line) markedly decreases soft-agar colonization, increases tumor latency periods and increases tumor doubling times without significantly altering monolayer growth. In this study, cells with reduced eIF-4E had delayed and reduced invasiveness and decreased experimental metastasis. Furthermore, reduced eIF-4E levels correlated with decreased expression of the metastasis-associated 92-kDa collagenase type-IV and exon-6 variants of the CD44 adhesion molecule [CD44(6v)]. Reduced eIF-4E levels correlated inversely with increased levels of the putative metastasis-suppressor protein nm23. Cell lines established from AS4E tumors and lung metastases exhibited increased levels of eIF-4E protein and protein synthesis rates compared to the AS4E line. Tumor-derived AS4E had the shortened tumor latency periods of CREF T24 but displayed the slow tumor-growth rates of AS4E. Tumor-derived AS4E exhibited the metastatic capacity of CREF T24 controls. Furthermore, tumor- and lung-nodule-derived AS4E expressed levels of CD44 (6v) and the 92-kDa collagenase type IV comparable to CREF T24 and displayed reduced levels of nm23 relative to AS4E. These results demonstrate that eIF-4E is an important effector molecule involved in oncogenic p21ras-induced malignant transformation.

In vitro studies of deformation and adhesion properties of transformed cells

The micropipet aspiration technique and the parallel-plate flow chamber were used to investigate the deformation and detachment properties, respectively, of normal and transformed rat fibroblasts. The normal Cloned Rat Embryo Fibroblasts (CREF) cell line was transfected with the T24 ras oncogene to produce the transformed cell line CREF T24. The CREF T24 cell line was transfected with a Kirsten ras revertant gene (K-rev 1a suppressor) to produce the CT24HKB1 cells, which have the same morphological characteristics as the cells in the CREF line. The cells utilized in this investigation were derived from the parent cell line CREF, the only differences being the presence or absence of the T24 ras oncogene and the Kirsten ras revertant gene. The detachment and deformation properties, therefore, could be related to the metastatic phenotype of the cell rather than inherent differences between disparate cell lines. Results indicated that transfecting the CREF cell line with the ras oncogene greatly modified the detachment and deformation properties. The CREF T24 cells were more easily detached from normal cells and were 50% more deformable. Both CREF and CT24HKB1 showed similar detachment properties. Based on these results, it is speculated that K-rev 1a reversed ras-induced membrane alterations in these cells. Preliminary investigations have demonstrated that both CREF and CREF T24 cells in different phases of the cell cycle differed in morphological characteristics. However, the majority of the cells within a given cell line showed similar deformation characteristics. Current investigations are focusing on characterization of both detachment and deformation properties of these cells as a function of the cell cycle using synchronization techniques.