Expression ofc-sis and other cellular proto-oncogenes in human sarcoma cell lines and biopsies

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Abstract
Six biopsies (4 of human fibrosarcomas, I of a B‐cell lymphoma and I of a normal lymph node from a melanoma patient) and 6 cell lines (derived from 5 different human osteosarcomas and from I rhabdomyosarcoma), together with control cells, were examined for the expression of c‐sis, c‐fosand c‐myc. The expression of c‐sis/PDGF‐B‐related proteins was also examined in cultured cells (not in biopsies). In situ hybridization studies further showed that the occurrence and level of expression of c‐sis mRNA and c‐sis/PDGF‐B‐related proteins were significant in the tumor cells. Expression of c‐fos and c‐myc mRNA did not correlate with c‐sis expression. Southern blot analysis of c‐sis, c‐fos and c‐myc of 20 DNAs of cell lines derived from human sarcoma or biopsies showed an identical pattern for BamHI and EcoRI restriction fragments of c‐sis(except for I fibrosarcoma biopsy), implicating no gene rearrangement as a cause of enhanced proto‐oncogene expression. The nucleotide sequence of c‐sis is highly homologous to that of the viral v‐sis oncogene which is capable of transforming infected cells. We conclude that enhanced expression of c‐sis in the sarcomas we have examined is involved in the initiation and/or maintenance of the cell transformed state.