Lipid metabolism is often elevated in
cancer cells and plays an important role in their growth and
malignancy.
Acyl-CoA synthetase (ACS), which converts long-chain
fatty acids to
acyl-CoA, is overexpressed in various types of
cancer. However, the role of ACS in
cancer remains unknown. Here, we found that ACS
enzyme activity is required for
cancer cell survival. Namely, the ACS inhibitor
Triacsin c induced massive apoptosis in
glioma cells while this cell death was completely suppressed by overexpression of ACSL5, the
Triacsin c-resistant ACS
isozyme, but not by overexpression of a catalytically inactive ACSL5 mutant. ACS inhibition by
Triacsin c markedly potentiated the Bax-induced intrinsic apoptotic pathway by promoting
cytochrome c release and subsequent
caspase activation. These effects were abrogated by ACSL5 overexpression. Correspondingly, ACS inhibition synergistically potentiated the
glioma cell death induced by
etoposide, a well-known activator of apoptosis. Furthermore, in a nude mouse xenograft model,
Triacsin c at a non-toxic dose enhanced the antitumor efficacy of a low-dose
chemotherapy with
etoposide. These results indicate that ACS is an apoptosis suppressor and that ACS inhibition could be a rational strategy to amplify the antitumor effect of
etoposide.