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 oncog enes are expressed in primary rat embryo fibroblasts (REFs). To identify su ch transformation suppressor genes, we prepared a subtracted cDNA library b y using REFs and a rat normal fibroblast cell line, F2408, and isolated 30 different cDNA clones whose mRNA expression was markedly reduced in F2408 c ells relative to that in REFs. We referred to these as TRIF (transcript red uced in F2408) clones. Among these genes, eve initially tested the suppress or activity for transformation on three TRIF genes, TRIF1 (neuronatin), TRI F2 (heparin-binding growth-associated molecule), and TRIF3 (lumican) by foc us formation assay and found that lumican inhibited focus formation induced by activated H-ras in F2408 cells. Colony formation in soft agar induced b y v-K-ras or v-src was also suppressed in F2408 clones stably expressing ex ogenous lumican without disturbing cell proliferation. Tumorigenicity in nu de mice induced by these oncogenes was also suppressed in these lumican-exp ressing clones. These results indicate that lumican has the ability to supp ress transformation by v-src and v-K-ras.