Fig. 7

HCAR1 and MCT activity is required for the L- and D-lactate-mediated enhancement of DNA repair and cell survival. a, b γ-H2AX foci resolution kinetics in control and HCAR1 shRNA-expressing HeLa cells incubated in the presence or absence of (a) 20 mM L-lactate or (b) 20 mM D-lactate for 24 h and then treated with 2nM NCS for 30 min.; drug alone (white circles), lactate + drug (black circles). c The relative mRNA level of MCT1, MCT2 and MCT4 in control (white column) and HCAR1 shRNA-expressing HeLa cells (black column). d, e Pretreatment of HeLa cells with the MCT inhibitor α-CHCA abolishes the modulatory effect of lactate. d HeLa cells were pretreated with 2 mM α-CHCA for 1 h before incubation in the presence or absence of L-lactate (20 mM) or D-lactate (20 mM) for 24 h. Then, the cells were exposed to NCS (5 nM) for 30 min and allowed to recover for 2 h before harvesting for the neutral comet assay. The basal OTM was subtracted, and the value observed at 0 h was set to 100 %. The graph shows the mean OTM ± SEM from three independent experiments; cells treated with vehicle (white columns), cells treated with α-CHCA (black columns). e The clonogenic survival of HeLa cells pretreated with 2 mM α-CHCA for 1 h before incubation in the presence or absence of L-lactate (20 mM) or D-lactate (20 mM) for 24 h. Then, the cells were exposed to NCS (5 nM) for the next 24 h and seeded for colony formation in drug-free medium; cells treated with vehicle (white columns), cells treated with α-CHCA (black columns). Statistical significance was evaluated using Student’s t-test. *P < 0.05 and **P < 0.01 indicate significant differences compared to the corresponding counterparts. The results are expressed as the means ± SEM of three independent experiments