A cell mutant that exhibits temperature-dependent sensitivity to transformation by various oncogenes

Isolation of transformation suppressor genes by cDNA subtraction: lumican suppresses transformation induced by v-src and v-K-ras

We have reported that suppressive factors for transformation by viral oncogenes are expressed in primary rat embryo fibroblasts (REFs). To identify such transformation suppressor genes, we prepared a subtracted cDNA library by using REFs and a rat normal fibroblast cell line, F2408, and isolated 30 different cDNA clones whose mRNA expression was markedly reduced in F2408 cells relative to that in REFs. We referred to these as TRIF (transcript reduced in F2408) clones. Among these genes, we initially tested the suppressor activity for transformation on three TRIF genes, TRIF1 (neuronatin), TRIF2 (heparin-binding growth-associated molecule), and TRIF3 (lumican) by focus formation assay and found that lumican inhibited focus formation induced by activated H-ras in F2408 cells. Colony formation in soft agar induced by v-K-ras or v-src was also suppressed in F2408 clones stably expressing exogenous lumican without disturbing cell proliferation. Tumorigenicity in nude mice induced by these oncogenes was also suppressed in these lumican-expressing clones. These results indicate that lumican has the ability to suppress transformation by v-src and v-K-ras.

Raf-1 protein kinase is an integral component of the oncogenic signal cascade shared by epidermal growth factor and platelet-derived growth factor

Our recent studies with cell mutants indicate that a cascade shared by the epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) signals exists in NRK cells and mediates oncogenic signals induced by many oncogenes (A. Masuda, S. Kizaka-Kondoh, H. Miwatani, Y. Terada, H. Nojima, and H. Okayama, New Biol. 4:489-503, 1992). We have employed the antisense RNA technique to investigate possible involvement of Raf-1 kinase in this signal transduction cascade. NRK cell clones highly reduced in the Raf-1 production are generated by the expression of a c-raf-1 antisense RNA. They have no apparent growth defects and retain proper mitotic responses to growth factors but are refractory to transformation by EGF or PDGF plus transforming growth factor beta, v-erbB, v-fms, v-K-ras, v-mos, v-fos, v-src, simian virus 40 large T, and polyomavirus middle T but not by v-raf or adenovirus E1A. These results not only support our model for the oncogenic signal cascade but also lead to the conclusion that Raf-1 protein kinase is a downstream component of this oncogenic signal cascade shared by EGF and PDGF.

Raf-1 protein kinase is an integral component of the oncogenic signal cascade shared by epidermal growth factor and platelet-derived growth factor

Our recent studies with cell mutants indicate that a cascade shared by the epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) signals exists in NRK cells and mediates oncogenic signals induced by many oncogenes (A. Masuda, S. Kizaka-Kondoh, H. Miwatani, Y. Terada, H. Nojima, and H. Okayama, New Biol. 4:489-503, 1992). We have employed the antisense RNA technique to investigate possible involvement of Raf-1 kinase in this signal transduction cascade. NRK cell clones highly reduced in the Raf-1 production are generated by the expression of a c-raf-1 antisense RNA. They have no apparent growth defects and retain proper mitotic responses to growth factors but are refractory to transformation by EGF or PDGF plus transforming growth factor beta, v-erbB, v-fms, v-K-ras, v-mos, v-fos, v-src, simian virus 40 large T, and polyomavirus middle T but not by v-raf or adenovirus E1A. These results not only support our model for the oncogenic signal cascade but also lead to the conclusion that Raf-1 protein kinase is a downstream component of this oncogenic signal cascade shared by EGF and PDGF.

bcr/abl and src but not myc and ras replace v-abl in lymphoid transformation

Lymphoid cells transformed by temperature-sensitive Abelson virus die at the nonpermissive temperature. This property was exploited to show that bcr/abl and v-src but not myc and ras can replace the transforming signal of v-abl, a result suggesting that the former but not the latter oncogenes transform lymphoid cells via a similar pathway.

bcr/abl and src but not myc and ras replace v-abl in lymphoid transformation

Lymphoid cells transformed by temperature-sensitive Abelson virus die at the nonpermissive temperature. This property was exploited to show that bcr/abl and v-src but not myc and ras can replace the transforming signal of v-abl, a result suggesting that the former but not the latter oncogenes transform lymphoid cells via a similar pathway.