Several
peptide hormones have been shown to influence growth and function in
pancreatic carcinoma and have given evidence for an autocrine feedback loop governing the proliferation of these malignant cells. Conversely,
steroid hormones including
glucocorticoids have been shown to inhibit the growth of
pancreatic cancer cells; however, the prevalence of the
glucocorticoid receptor or its mechanism of growth suppression in these
tumors is unknown. The ability of
growth factors thought to be active in this autocrine loop to reverse the
glucocorticoid-induced growth inhibition was studied in vitro in a human pancreatic
adenocarcinoma (HPAC) cell line with a well-characterized
glucocorticoid receptor (GR). The
glucocorticoid dexamethasone (DEX) inhibited growth in a dose-dependent manner as measured by a [3H]
thymidine incorporation assay as well as an MTT cell proliferation assay. Maximal effects were seen within 48 hr at a concentration of 100 nM DEX, suppressing growth to approximately 18% of control. When the maximally suppressed DEX-treated cells were exposed to exogenous
growth factors, they rapidly attained or exceeded the growth rate of control cells:
insulin-like growth factor = 106%,
transforming growth factor-alpha = 134%,
insulin = 151%, and
epidermal growth factor = 187% (all P < 0.05, Student's t test). In order to determine the frequency of the GR in
pancreatic cancer and the clinical relevance of our findings, immunohistochemical staining for the GR was performed on 20 human
tumors. Twelve (60%) of all
cancers, as well as all normal pancreatic tissues (n = 4), stained positively for cytoplasmic and/or nuclear GR with expression correlating highly with degree of
tumor differentiation (Kruskal-Wallis test, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)