Abstract:
Cholangiocarcinoma (CCA) in Thai patients is closely associated with liver fluke
infection and chronic inflammation. TNF-α is a cytokine that has been shown to be
involved in immunity and inflammation by eliciting a broad spectrum of responses,
including cell motility, proliferation, apoptosis and MMP secretion.
This study investigated if, and how, TNF-α is involved in controlling the
invasiveness of cholangiocarcinoma using RMCCA-1 cell line that was established as
a model. A cholangiocarcinoma cell line was successfully established from a Thai
patient, named RMCCA-1. The cell line expressed general characteristics of biliary
epithelium and retained some characteristics of the original tumor including
overexpression of the tumor marker CA19-9. It also exhibited a high degree of in
vitro motility, although the invasiveness was low. The RMCCA-1 cell expressed a
TNFRII receptor as determined by RT-PCR. It remains unproven whether RMCCA-1
expressed TNFRI, as an aberrant-sized PCR product was amplified when primers
specific for TNFRI receptor were used.
To understand the role of TNF-α in regulating the invasiveness of
cholangiocarcinoma, the RMCCA-1 cells were treated with various doses of TNF- α
and assayed for in vitro invasiveness. In vitro invasion of RMCCA-1 increased dosedependently
with TNF-α treatment while cell proliferation was virtually unaltered.
MMP-9 activity in the conditioned medium increased in response to TNF-α, although
independent of the dosage applied. Enhancement of in vitro invasion and MMP-9
activity was significantly reduced by inhibitors of ERK1/2, PI3-kinase and NF-kB,
suggesting that the TNF-α-activated phenotypes were mediated by these molecular
signaling pathways. Involvement of ERK1/2, PI3-kinase and NF-kB-mediated
signaling was confirmed by a Western Blot. Furthermore, LY294002 and U0126
suppressed phospho-S6 ribosomal protein and phospho-42/44 MAPK, but not NF-kB
translocation which was, instead, blocked by PSI. Proteomics analysis of RMCCA-1
cells treated with 100 ng/ml TNF-α demonstrated a significant up-regulation of
CDC42, correlating with enhancement of in vitro invasiveness by TNF-α.