Detection of c-sis proto-oncogene transcripts by direct enzyme-labeled cDNA probes and in situ hybridization

Using in situ hybridization and platelet-derived growth factor (PDGF) cDNA probes labeled with horseradish peroxidase, PDGF-A and -B (c-cis proto- oncogene) mRNA transcripts were identified and localized in proliferating cultures. A human retinal pigment epithelial (RPE) cell line and a glial cell line were treated with either transforming growth factor beta-1 (TGFB₁), phorbol-12-myristate-13-acetate (PMA), or thrombin from human plasma and compared for their ability to stimulate the production of PDGF-A and -B. Expression of both PDGF-A and -B transcripts were found to be localized predominantly in the cytoplasm of TGFB₁-treated RPE cells, with a portion of these cells displaying a hybridization response in the nuclear region. When compared to PMA- and thrombin-treated cells, TGFB₁ stimulated the RPE cell line to yield the greatest amount of detectable PDGF mRNA. In addition, the hybridization response observed in TGFB₁-treated cells was shown to be RNA dependent.