Franny Jongbloed

69 3 PROTECTION OF FASTING ON IRINOTECAN TOXICITY would likely improve our understanding of the results we obtained. In addition, in this experimental model we compare healthy liver tissue and C26 colon cancer cells induced by subcutaneous injection. Other models might provide more information about the effects of fasting on various cancer tissues. Finally, this study only partially explains how fasting changes irinotecan metabolism and how it protects the organism, but not the tumor, against irinotecan exposure. Addressing the impact of fasting on posttranscriptional level will likely improve our understanding of the mechanisms of fasting-induced chemoprotection. In conclusion, we show that three days of fasting results in protection against the side effects of irinotecan treatment and activates a protective stress response in healthy liver, but not in tumor tissue. Although fasting leads to an increase in differentially regulated pathways following irinotecan treatment in tumor tissue, it does not abrogate its antitumor efficacy. These results further strengthen the oncologic safety of DR in cancer patients, where short- term fasting could improve both efficacy of treatment and quality of life in patients with colorectal cancer treated with irinotecan. MATERIALS AND METHODS Animals Male BALB/c mice of 6-8 weeks old, weighing approximately 25 grams, were obtained from Charles River, Maastricht, the Netherlands. Upon arrival, animals were housed at random in individually ventilated cages (n=4 animals per cage) in a licensed biomedical facility at Erasmus University Medical Center, Rotterdam, the Netherlands. Standard laboratory conditions were maintained, i.e. temperature ~22ºC, humidity ~50%, and a 12 h light/12 h dark cycle. All mice had free access to water and food (Special Diet Services, Witham, UK) unless mentioned otherwise. Animals were allowed to acclimatize for one week before the start of the experiments. The experimental protocol was approved by the Animal Experiments Committee under the Dutch National Experiments on Animals Act, and complied with the 1986 directive 86/609/EC of the Council of Europe. C26 colon carcinoma cells The murine colon carcinoma cell line C26 originally derived from the BALB/c mouse and was cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) (Sigma Aldrich, St. Louis, MO), supplemented with 10% fetal calf serum (Lonza, Verviers, Belgium), penicillin (100 units/ml) and streptomycin (100 units/ml) (Invitrogen, Auckland, NZ) at 37 degrees Celsius in a 5% carbon dioxide environment. Cells were harvested by brief trypsinization (0.05% trypsin in 0.02% ethylenediamine tetra-acetic acid (EDTA)). For subcutaneous injection,