Transforming growth factor-beta (TGF-beta) is produced by a number of
tumor cell types including human malignant mesothelioma (MM), but its
role as a direct or indirect factor in tumorigenesis is incompletely u
nderstood. We have investigated the expression of TGF-beta isoforms by
human and murine MM cells and have analysed the effects of inducible
antisense RNA-mediated inhibition of TGF-beta expression on murine MM
in vitro and in vivo. The results showed that (a) TGF-beta 1 and -beta
2 were produced by both human and mouse MM cells, (b) antisense RNA a
gainst either TGF-beta 1 or -beta 2 cross-inhibited both TGF-beta 1 an
d -beta 2 expression, (c) inhibition of TGF-beta expression reduced th
e anchorage-independent growth of MM cells in vitro and the tumorigeni
city of MM cells in vivo, and (d) inhibition of TGF-beta expression le
d to increased T lymphocyte infiltration into tumors. The data suggest
that TGF-beta has multiple tumor-enhancing effects in MM.