Franny Jongbloed

61 3 PROTECTION OF FASTING ON IRINOTECAN TOXICITY variability. A shift on both the PC1 and PC2 axes could be detected between the AL vehicle and AL irinotecan groups, while the fasting comparison diverged more on the PC1 axis in an opposite direction but converging with the AL irinotecan group. Both irinotecan-treated groups showed high overlap and no clear clustering of groups. The data derived from these PCA plots show a heterogeneous response in tumor tissue treated with irinotecan, and this response could not be altered by three days of fasting. Expression profiles Calculation of the number of DEPS in the tumor groups was done similarly as in the liver. The comparison of AL vehicle and AL irinotecan showed 610 DEPS, of which 321 were downregulated and 289 upregulated (Figure 3B). The number of regulated DEPS between fasting vehicle and fasting irinotecan was 3,093, of which 1,922 were upregulated and 1,171 downregulated. A total of 138 DEPS overlapped between the AL vehicle vs. AL irinotecan and the fasting vehicle vs. fasting irinotecan comparison, corresponding to 23% of the DEPS in the AL groups and only 5% of the fasting groups (Figure 3C). All DEPS considered, only 17% had the same directionality in both comparisons, while the other DEPS had opposite directionalities (Figure 3D), contrasting sharply to the 83% similar directionality found in the liver (Figure 2D). Pathway analyses Similarly as done in the liver, pathway analyses were performed in tumor tissue using the DEPS of the AL comparison and the fasting comparison groups. The 610 DEPS as found between the AL vehicle and AL irinotecan group, revealed 11 pathways. Of these pathways, three were upregulated: PTEN Signaling, P53 Signaling and Apoptotic Signaling (Table 2A). The majority of the eight downregulated pathways was involved in inhibition of neurotransmitter signaling. Comparing the fasting groups, 72 pathways were differentially regulated of which 18 were significantly upregulated and one downregulated (Table 2B). Eight overly expressed pathways were involved in cell cycle, cell growth or apoptosis, others mainly regulated cellular growth and the immune response. The tumor AL and tumor fasting groups showed one pathway in common, Huntington’s Disease Signaling , which was oppositely regulated.