Carcinogen-induced transformation in Syrian hamster embryo (SHE) cells
is a multistage process characterized by specific genetic alterations
at each stage in the transformation process. Loss of H19 gene express
ion is one of the earliest events observed, occurring in approximately
75% of the morphologically transformed cells and the subsequently der
ived tumorigenic cells. To investigate the effect the loss of H19 expr
ession has on SHE cell tumorigenicity, H19 expression was reestablishe
d in a tumorigenic SHE cell lineage that lacked H19 expression. H19 re
expression had little effect on cellular growth in vitro but did retar
d tumor growth in nude mice. Analysis of the tumors that did develop f
rom cells containing the H19 gene indicated that loss of exogenous H19
gene expression was probably due to changes in DNA methylation. These
results demonstrate that alterations in H19 gene expression play an i
mportant role in SHE cell tumorigenicity. (C) 1997 Wiley-Liss, Inc.