Figure 3. Caloric restriction improves protection against heat shock through increased expression of Hsp70. (A) B16F10 melanoma cells stably transfected with a plasmid encoding GFP-tagged Hsp70 construct were maintained in medium supplemented with 10% serum from AL- or CR-fed rats and then subjected or not to heat shock stress for 45 min. Bars represent fluorescence intensity per 105 cells. Cell culture experiments were performed as three or more replicates. (B) B16F10 tumor xenografts from mice fed either AL or CR diet were subjected to heat shock stress for 45 min and sacrificed after 4h. Bars represent fluorescence intensity per mg of tumor proteins; n=10 per group. Data, obtained by fluorimetery, are represented as the means ± SEM. *, p <0.05 vs. AL group; #, p<0.05 vs. CR group. (C) Images of B16F10 cells and (D) tumor cells depicting GFP fluorescence were detected by confocal microscopy. White bar, 20 μm.