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Polyoma middle T-induced vascular tumor formation: the role of the plasminogen activator/plasmin system.

Sabapathy KT, Pepper MS, Kiefer F, Möhle-Steinlein U, Tacchini-Cottier F, Fetka I, Breier G, Risau W, Carmeliet P, Montesano R, Wagner EF - J. Cell Biol. (1997)

Bottom Line: In addition, the lack of either uPA or tissue-type PA (tPA) activity is not limiting for the establishment and proliferation of End. cells in vitro, although the combined loss of both PA activities leads to a marked reduction in proliferation rates.Furthermore, the in vitro morphogenetic properties of mutant End. cells in fibrin gels could only be correlated with an altered proteolytic status in cells lacking both uPA and tPA.Thus, genetic alterations in the PA/plasmin system affect vascular tumor development, indicating that this system is a causal component in PymTmediated oncogenesis.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Molecular Pathology, University of Vienna, A-1030 Vienna, Austria.

ABSTRACT
The middle T antigen of murine Polyomavirus (PymT) rapidly transforms endothelial cells, leading to the formation of vascular tumors in newborn mice. Transformed endothelial (End.) cell lines established from such tumors exhibit altered proteolytic activity as a result of increased expression of urokinase-type plasminogen activator (uPA) and are capable of inducing vascular tumors efficiently when injected into adult mice. In this study we have used mice lacking components of the PA/plasmin system to analyze the role of this system in the transformation process and in tumor growth. We found that the proteolytic status of the host is not a critical determinant for PymT-induced vascular tumor formation. In addition, the lack of either uPA or tissue-type PA (tPA) activity is not limiting for the establishment and proliferation of End. cells in vitro, although the combined loss of both PA activities leads to a marked reduction in proliferation rates. Furthermore, the in vitro morphogenetic properties of mutant End. cells in fibrin gels could only be correlated with an altered proteolytic status in cells lacking both uPA and tPA. However, in contrast with tumors induced by PymT itself, the tumorigenic potential of mutant and wild-type End. cell lines was found to be highly dependent on the proteolytic status of both the tumor cells and the host. Thus, genetic alterations in the PA/plasmin system affect vascular tumor development, indicating that this system is a causal component in PymTmediated oncogenesis.

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Incidence and latency of tumor formation. End. cell– induced tumor formation was investigated using mutant End.  cells in wild-type and nude mice (A), wild-type End. cells in mutant mice (B), and utPA−/− End. cells in mutant mice (C). All  mice were inbred for more than six generations and injected with  the following cell lines; the time taken for the onset of tumors  (days after injection) and the latency period for the formation of  125-mm2 tumors was recorded: wild-type, s1 (p35 and 40) and s2  (p23, 34 and 40); uPA−/−, u23 (p33) and u24 (p23); tPA−/−, t37  (p25 and 35) and t38 (p6 and 25); and utPA−/−, ut1(p20) and ut2  (p28 and 40). Observation period was for up to 60 d after injection. n, number of mice from at least two independent experiments.
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Figure 5: Incidence and latency of tumor formation. End. cell– induced tumor formation was investigated using mutant End. cells in wild-type and nude mice (A), wild-type End. cells in mutant mice (B), and utPA−/− End. cells in mutant mice (C). All mice were inbred for more than six generations and injected with the following cell lines; the time taken for the onset of tumors (days after injection) and the latency period for the formation of 125-mm2 tumors was recorded: wild-type, s1 (p35 and 40) and s2 (p23, 34 and 40); uPA−/−, u23 (p33) and u24 (p23); tPA−/−, t37 (p25 and 35) and t38 (p6 and 25); and utPA−/−, ut1(p20) and ut2 (p28 and 40). Observation period was for up to 60 d after injection. n, number of mice from at least two independent experiments.

Mentions: To define a causal role for the PAs in End. cell–induced vascular tumors, we have used cells lacking uPA, tPA, and both uPA and tPA (utPA) for tumor formation studies in adult wild-type mice. We have used immunologically competent adult mice in these studies to avoid variability that may arise from the use of newborn mice with a developing immune system. Tumors were visible as small outgrowths in all mice injected with wild-type End. cells between day 4 and 7 and grew in size to 125 mm2 by 11–18 d (Fig. 5 A). Histologically, these tumors consisted of a central hemorrhagic/necrotic core surrounded by an intense inflammatory cell infiltrate with neovascularization and very little fibrin deposition (Fig. 6, A and B). Similar results were obtained in mice injected with tPA-deficient End. cells, and there was no significant delay in either the onset or growth rates of these tumors. In contrast, tumor induction with uPA−/− End. cells showed incomplete penetrance and a delay in formation (Fig. 5 A). Only 50% of the mice developed tumors by days 11–14, and it took between 18 and 25 d for these tumors to reach maximum size. The remaining mice did not develop tumors for the entire 60-d observation period. Similarly, about two-thirds of the mice injected with End. cells deficient in both uPA and tPA developed tumors at an extremely slow rate (Fig. 5 A). Tumors were visible between 19 and 24 d after injection, and it took between 40 and 60 d to form tumors of maximum size. The remaining mice did not develop tumors. Histologically, these tumors were similar to those induced by wild-type cells, with the notable exception that extensive fibrin deposition was observed with the Lendrum and PTAH staining techniques (Fig. 6, E and F; data not shown). These results indicate that End. cell lines lacking only tPA activity are not inhibited in their capacity to form tumors. However, cell lines lacking uPA activity (both uPA−/− and utPA−/−) display a reduced efficiency in tumor formation in wild-type mice; when tumors do arise, their growth rate is significantly retarded, indicating that uPA activity of tumor cells is critical for efficient tumor growth.


Polyoma middle T-induced vascular tumor formation: the role of the plasminogen activator/plasmin system.

Sabapathy KT, Pepper MS, Kiefer F, Möhle-Steinlein U, Tacchini-Cottier F, Fetka I, Breier G, Risau W, Carmeliet P, Montesano R, Wagner EF - J. Cell Biol. (1997)

Incidence and latency of tumor formation. End. cell– induced tumor formation was investigated using mutant End.  cells in wild-type and nude mice (A), wild-type End. cells in mutant mice (B), and utPA−/− End. cells in mutant mice (C). All  mice were inbred for more than six generations and injected with  the following cell lines; the time taken for the onset of tumors  (days after injection) and the latency period for the formation of  125-mm2 tumors was recorded: wild-type, s1 (p35 and 40) and s2  (p23, 34 and 40); uPA−/−, u23 (p33) and u24 (p23); tPA−/−, t37  (p25 and 35) and t38 (p6 and 25); and utPA−/−, ut1(p20) and ut2  (p28 and 40). Observation period was for up to 60 d after injection. n, number of mice from at least two independent experiments.
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Figure 5: Incidence and latency of tumor formation. End. cell– induced tumor formation was investigated using mutant End. cells in wild-type and nude mice (A), wild-type End. cells in mutant mice (B), and utPA−/− End. cells in mutant mice (C). All mice were inbred for more than six generations and injected with the following cell lines; the time taken for the onset of tumors (days after injection) and the latency period for the formation of 125-mm2 tumors was recorded: wild-type, s1 (p35 and 40) and s2 (p23, 34 and 40); uPA−/−, u23 (p33) and u24 (p23); tPA−/−, t37 (p25 and 35) and t38 (p6 and 25); and utPA−/−, ut1(p20) and ut2 (p28 and 40). Observation period was for up to 60 d after injection. n, number of mice from at least two independent experiments.
Mentions: To define a causal role for the PAs in End. cell–induced vascular tumors, we have used cells lacking uPA, tPA, and both uPA and tPA (utPA) for tumor formation studies in adult wild-type mice. We have used immunologically competent adult mice in these studies to avoid variability that may arise from the use of newborn mice with a developing immune system. Tumors were visible as small outgrowths in all mice injected with wild-type End. cells between day 4 and 7 and grew in size to 125 mm2 by 11–18 d (Fig. 5 A). Histologically, these tumors consisted of a central hemorrhagic/necrotic core surrounded by an intense inflammatory cell infiltrate with neovascularization and very little fibrin deposition (Fig. 6, A and B). Similar results were obtained in mice injected with tPA-deficient End. cells, and there was no significant delay in either the onset or growth rates of these tumors. In contrast, tumor induction with uPA−/− End. cells showed incomplete penetrance and a delay in formation (Fig. 5 A). Only 50% of the mice developed tumors by days 11–14, and it took between 18 and 25 d for these tumors to reach maximum size. The remaining mice did not develop tumors for the entire 60-d observation period. Similarly, about two-thirds of the mice injected with End. cells deficient in both uPA and tPA developed tumors at an extremely slow rate (Fig. 5 A). Tumors were visible between 19 and 24 d after injection, and it took between 40 and 60 d to form tumors of maximum size. The remaining mice did not develop tumors. Histologically, these tumors were similar to those induced by wild-type cells, with the notable exception that extensive fibrin deposition was observed with the Lendrum and PTAH staining techniques (Fig. 6, E and F; data not shown). These results indicate that End. cell lines lacking only tPA activity are not inhibited in their capacity to form tumors. However, cell lines lacking uPA activity (both uPA−/− and utPA−/−) display a reduced efficiency in tumor formation in wild-type mice; when tumors do arise, their growth rate is significantly retarded, indicating that uPA activity of tumor cells is critical for efficient tumor growth.

Bottom Line: In addition, the lack of either uPA or tissue-type PA (tPA) activity is not limiting for the establishment and proliferation of End. cells in vitro, although the combined loss of both PA activities leads to a marked reduction in proliferation rates.Furthermore, the in vitro morphogenetic properties of mutant End. cells in fibrin gels could only be correlated with an altered proteolytic status in cells lacking both uPA and tPA.Thus, genetic alterations in the PA/plasmin system affect vascular tumor development, indicating that this system is a causal component in PymTmediated oncogenesis.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Molecular Pathology, University of Vienna, A-1030 Vienna, Austria.

ABSTRACT
The middle T antigen of murine Polyomavirus (PymT) rapidly transforms endothelial cells, leading to the formation of vascular tumors in newborn mice. Transformed endothelial (End.) cell lines established from such tumors exhibit altered proteolytic activity as a result of increased expression of urokinase-type plasminogen activator (uPA) and are capable of inducing vascular tumors efficiently when injected into adult mice. In this study we have used mice lacking components of the PA/plasmin system to analyze the role of this system in the transformation process and in tumor growth. We found that the proteolytic status of the host is not a critical determinant for PymT-induced vascular tumor formation. In addition, the lack of either uPA or tissue-type PA (tPA) activity is not limiting for the establishment and proliferation of End. cells in vitro, although the combined loss of both PA activities leads to a marked reduction in proliferation rates. Furthermore, the in vitro morphogenetic properties of mutant End. cells in fibrin gels could only be correlated with an altered proteolytic status in cells lacking both uPA and tPA. However, in contrast with tumors induced by PymT itself, the tumorigenic potential of mutant and wild-type End. cell lines was found to be highly dependent on the proteolytic status of both the tumor cells and the host. Thus, genetic alterations in the PA/plasmin system affect vascular tumor development, indicating that this system is a causal component in PymTmediated oncogenesis.

Show MeSH
Related in: MedlinePlus