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During cancer therapy with DNA-damaging drug-agents, the development of secondary resistance to apoptosis can be observed. In the search for novel therapeutic approaches that can be used in these cases, we monitored chemotherapy-induced apoptosis resistance in a syngenic mouse tumor model. For this, syngenic murine colorectal carcinoma cells, which stably expressed a FRET-based caspase-3 activity sensor, were introduced into animals to induce peritoneal carcinomatosis or disseminated hepatic metastases. This syngenic system allowed in vitro, in vivo and ex vivo analysis of chemotherapy induced apoptosis induction by optically monitoring the caspase-3 sensor state in the tumor cells. Tumor tissue analysis of 5-FU treated mice showed the selection of 5-FU-induced apoptosis resistant tumor cells. These and chemo-naive fluorescent tumor cells could be re-isolated from treated and untreated mice and propagated in cell culture. Re-exposure to 5-FU and second line treatment modalities in this ex-vivo setting showed that 5-FU induced apoptosis resistance could be alleviated by imatinib mesylate (Gleevec). We thus show that syngenic mouse systems that stably express a FRET-based caspase-3 sensor can be employed to analyse the therapeutic efficiency of apoptosis inducing chemotherapy.

We investigated the therapeutic efficiency of sulfonate-modified polyvinyl alcohol beads loaded with doxorubicin, irinotecan or mitoxantrone in vitro and in vivo in a model of experimental peritoneal carcinomatosis (PC). In vitro, cell proliferation was efficiently impaired by doxorubicin drug eluting bead (DEB) treatment while mitoxantrone DEBs were less effective than. Irinotecan showed little effect for both DEBs and free drug. Apoptosis was not different between free mitoxantrone and the DEB form while more apoptosis induction was observed in cells incubated with free doxorubicin and irinotecan. Experimental PC was produced in mice. The therapeutic efficiency of either mitoxantrone and doxorubicin DEB or free drugs were compared. Mice were treated either once on day 12 or by 3 repetitive applications on days 7, 10 and 12. Mice treated by DEBs showed less weight loss and mortality. Therapeutic effect was determined by measuring tumor volume and tumor load on the day 15 after tumor inoculation. For the single application on the day 12, an advantage could be observed for the free drugs. After 3 repeated injections of both free and mitoxantrone DEB no difference in tumor load or tumor volume could be observed. Least tumor load and tumor volume was observed in mice that received 3 repeated injections of doxorubicin DEB. No animal survived 3 injections of free doxorubicin. We conclude that bead encapsulation of chemotherapeutic drugs may show the advantage of less toxicity in peritoneal spread of colorectal cancer.