Molecular and Cellular Biology, December 2001, p. 8471-8482, Vol. 21, No. 24
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.24.8471-8482.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Department of Microbiology and Cancer Center, University of Virginia School of Medicine, Charlottesville, Virginia
Received 14 December 2000/Returned for modification 30 January 2001/Accepted 14 September 2001
Neuroendocrine (NE) differentiation in prostatic
adenocarcinomas has been reported to be an early marker for
development of androgen independence. Secretion of mitogenic peptides
from nondividing NE cells is thought to contribute to a more aggressive
disease by promoting the proliferation of surrounding tumor cells. We undertook studies to determine whether the prostate cancer cell line
LNCaP could be induced to acquire NE characteristics by
treatment with agents that are found in the complex environment in
which progression of prostate cancer towards androgen independence
occurs. We found that cotreatment of LNCaP cells with agents
that signal through cyclic AMP-dependent protein kinase (PKA), such as
epinephrine and forskolin, and with the cytokine interleukin-6 (IL-6)
promoted the acquisition of an NE morphological phenotype above that
seen with single agents. Convergent IL-6 and PKA signaling also
resulted in potentiated mitogen-activated protein kinase (MAPK)
activation without affecting the level of signal transducer and
activator of transcription or PKA activation observed with these agents alone. Cotreatment with epinephrine and IL-6 synergistically increased c-fos transcription as well as transcription from the
4
nicotinic acetylcholine receptor subunit promoter. Potentiated
transcription from these elements was shown to be dependent on the MAPK
pathway. Most importantly, cotreatment with PKA activators and IL-6
resulted in increased secretion of mitogenic neuropeptides. These
results indicate that PKA and IL-6 signaling participates in gene
transcriptional changes that reflect acquisition of an NE phenotype by
LNCaP cells and suggest that similar signaling mechanisms,
particularly at sites of metastasis, may be responsible for the
increased NE content of many advanced prostate carcinomas.
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