Polyisoprenylated methylated protein methyl esterase is both sensitive to curcumin and overexpressed in colorectal cancer: implications for chemoprevention and treatment.
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ABSTRACT: Inhibition of PMPMEase, a key enzyme in the polyisoprenylation pathway, induces cancer cell death. In this study, purified PMPMEase was inhibited by the chemopreventive agent, curcumin, with a K(i) of 0.3 ?M (IC50 = 12.4 ?M). Preincubation of PMPMEase with 1 mM curcumin followed by gel-filtration chromatography resulted in recovery of the enzyme activity, indicative of reversible inhibition. Kinetics analysis with N-para-nitrobenzoyl-S-trans,trans-farnesylcysteine methyl ester substrate yielded K M values of 23.6 ± 2.7 and 85.3 ± 15.3 ?M in the absence or presence of 20 ?M curcumin, respectively. Treatment of colorectal cancer (Caco2) cells with curcumin resulted in concentration-dependent cell death with an EC50 of 22.0 ?g/mL. PMPMEase activity in the curcumin-treated cell lysate followed a similar concentration-dependent profile with IC50 of 22.6 ?g/mL. In colorectal cancer tissue microarray studies, PMPMEase immunoreactivity was significantly higher in 88.6% of cases compared to normal colon tissues (P < 0.0001). The mean scores ± SEM were 91.7 ± 11.4 (normal), 75.0 ± 14.4 (normal adjacent), 294.8 ± 7.8 (adenocarcinoma), and 310.0 ± 22.6 (mucinous adenocarcinoma), respectively. PMPMEase overexpression in colorectal cancer and cancer cell death stemming from its inhibition is an indication of its possible role in cancer progression and a target for chemopreventive agents.
SUBMITTER: Amissah F
PROVIDER: S-EPMC3713324 | biostudies-literature | 2013
REPOSITORIES: biostudies-literature
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