thymosin-beta(4) and Fibrosarcoma

Nanoparticles are prevalent in both commercial and medicinal products; however, the contribution of nanomaterials to carcinogenesis remains unclear. We therefore examined the effects of nano-sized titanium dioxide (TiO(2)) on poorly tumorigenic and nonmetastatic QR-32 fibrosarcoma cells. We found that mice that were cotransplanted subcutaneously with QR-32 cells and nano-sized TiO(2), either uncoated (TiO(2)-1, hydrophilic) or coated with stearic acid (TiO(2)-2, hydrophobic), did not form tumors. However, QR-32 cells became tumorigenic after injection into sites previously implanted with TiO(2)-1, but not TiO(2)-2, and these developing tumors acquired metastatic phenotypes. No differences were observed either histologically or in inflammatory cytokine mRNA expression between TiO(2)-1 and TiO(2)-2 treatments. However, TiO(2)-2, but not TiO(2)-1, generated high levels of reactive oxygen species (ROS) in cell-free conditions. Although both TiO(2)-1 and TiO(2)-2 resulted in intracellular ROS formation, TiO(2)-2 elicited a stronger response, resulting in cytotoxicity to the QR-32 cells. Moreover, TiO(2)-2, but not TiO(2)-1, led to the development of nuclear interstices and multinucleate cells. Cells that survived the TiO(2) toxicity acquired a tumorigenic phenotype. TiO(2)-induced ROS formation and its related cell injury were inhibited by the addition of antioxidant N-acetyl-l-cysteine. These results indicate that nano-sized TiO(2) has the potential to convert benign tumor cells into malignant ones through the generation of ROS in the target cells.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Cell Line, Tumor; Cell Transformation, Neoplastic; Cytokines; Deoxyguanosine; Dinoprostone; Female; Fibrosarcoma; Intercellular Signaling Peptides and Proteins; Mice; Mice, Inbred C57BL; Nanoparticles; Neoplasm Invasiveness; Particle Size; Reactive Oxygen Species; Thymosin; Titanium; Vascular Endothelial Growth Factor A

We identified a thymosin-beta4 gene overexpression in malignant mouse fibrosarcoma cells (QRsP-30) that were derived from clonal weakly tumorigenic and nonmetastatic QR-32 cells by using a differential display method. Thymosin-beta4 is known as a 4.9-kd polypeptide that interacts with G-actin and functions as a major actin-sequestering protein in cells. All of the six malignant fibrosarcoma cell lines that have been independently converted from QR-32 cells expressed high levels of thymosin-beta4 mRNA and its expression in tumor cells was correlated with tumorigenicity and metastatic potential. Up-regulation of thymosin-beta4 in QR-32 cells (32-S) transfected with sense thymosin-beta4 cDNA converted the cells to develop tumors and formed numerous lung metastases in syngeneic C57BL/6 mice. In contrast, antisense thymosin-beta4 cDNA-transfected QRsP-30 (30-AS) cells reduced thymosin-beta4 expression, and significantly lost tumor formation and metastases to distant organs. Vector-alone transfected cells (32-V or 30-V cells) behaved like their parental cells. We observed that tumor cell motility, cell shape, and F-actin organization is regulated in proportion to the level of thymosin-beta4 expression. These findings indicate that thymosin-beta4 molecule regulates fibrosarcoma cell tumorigenicity and metastasis through actin-based cytoskeletal organization.

Topics: Animals; Cell Movement; Fibrosarcoma; Gene Expression Regulation, Neoplastic; Lung Neoplasms; Mice; Mice, Inbred C57BL; Neoplasm Transplantation; Thymosin; Transfection; Tumor Cells, Cultured

We have shown the in vivo usefulness of a novel chimera tumor necrosis factor (TNF), called rTNF-STH, which was constituted with human thymosin beta 4 and recombinant human TNF-SAM1. Tumor necrosis was induced by intravenous injection of a smaller amount of rTNF-STH (1 x 10(3) U/mouse, 0.67 microgram/mouse) than rTNF-alpha or rTNF-S (1 x 10(4) U/mouse, 2.5-5 micrograms/mouse). Significant antitumor effects of rTNF-STH to Meth A fibrosarcoma, B16 melanoma, MH134 hepatoma, or Lewis lung carcinoma (3LL) were observed by systemic injection of rTNF-STH at the maximum tolerable dose of 1 x 10(4) U/mouse (6.7 micrograms/mouse); this dose did not cause regression of tumors by conventional rTNF-alpha. rTNF-STH showed a significant prolongation of its half-life in serum. The average calculated half-life of the chimera protein is about 110 min, which is 15 times longer than that of original TNF-SAM1 (7.5 min). On the basis of this prolongation of half-life of rTNF-STH and its efficient hemorrhagic necrotic activity, the antitumor effect of rTNF-STH--as compared with that of the known TNF species--is discussed. Findings indicate that use of the chimera protein to alter the N-terminal region of TNF may be a promising approach to obtain molecules that more favorably attack tumors and other diseases than conventional rTNFs.

Topics: Animals; Fibrosarcoma; Half-Life; Liver Neoplasms, Experimental; Lung Neoplasms; Melanoma, Experimental; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Mice, Inbred C57BL; Necrosis; Neoplasm Transplantation; Neoplasms, Experimental; Recombinant Fusion Proteins; Recombinant Proteins; Thymosin; Tumor Necrosis Factor-alpha