Unlike normal cells,
cancer cells undergo unlimited growth and multiplication, causing them to require massive amounts of
amino acid to support their continuous metabolism. Among the
amino acid transporters expressed on the plasma membrane, l-type
amino acid transporter-1, a
Na+-independent neutral amino acid transporter, is highly expressed in many types of human
cancer including
cholangiocarcinoma. Our previous study reported that l-type
amino acid transporter-1 and its co-functional
protein CD98 were highly expressed and implicated in
cholangiocarcinoma progression and
carcinogenesis. Therefore, this study determined the effect of
JPH203, a selective inhibitor of l-type
amino acid transporter-1 activity, on
cholangiocarcinoma cell inhibition both in vitro and in vivo.
JPH203 dramatically suppressed [14C]
l-leucine uptake as well as cell growth in
cholangiocarcinoma cell lines along with altering the expression of l-type
amino acid transporter-1 and CD98 in response to
amino acid depletion. We also demonstrated that
JPH203 induced both G2/M and G0/G1 cell cycle arrest, as well as reduced the S phase accompanied by altered expression of the
proteins in cell cycle progression:
cyclin D1, CDK4, and CDK6. There was also cell cycle arrest of the related
proteins, P21 and P27, in KKU-055 and KKU-213
cholangiocarcinoma cells. Apoptosis induction, detected by an increase in
trypan blue-stained cells along with a cleaved
caspase-3/
caspase-3 ratio, occurred in JPH203-treated
cholangiocarcinoma cells at the highest concentration tested (100 µM). As expected, daily
intravenous administration of
JPH203 (12.5 and 25 mg/kg) significantly inhibited
tumor growth in KKU-213
cholangiocarcinoma cell xenografts in the nude mice model in a dose-dependent manner with no statistically significant change in the animal's
body weight and with no differences in the histology and appearance of the internal organs compared with the control group. Our study demonstrates that suppression of l-type
amino acid transporter-1 activity using
JPH203 might be used as a new therapeutic strategy for
cholangiocarcinoma treatment.