Protective properties of anthocyanins during chemotherapy

In Western countries colorectal cancer is the second most frequent malignancy of top five causes for cancer related death. A major obstacle in colon cancer treatment with the chemo-therapeutic irinotecan, even in combination with 5-fluorouracil, is the induction of severe diarrhea and damage of the intestinal barrier. Irinotecan is used as a pro-drug, which is metabolized to the highly cytotoxic metabolite SN-38, which is postulated as a potential reason for diarrhea. Anthocyanins are a class of colored plant pigments, present in many fruits and vegetables, such as bilberries, grapes or red cabbage. A multitude of positive health effects have been ascribed to these food constituents in particular protection from oxidants, toxins and tumor development. Due to these beneficial health effects a variety of anthocyanin-based food supplements are available on the market promising health improving effects. Protective effects against chemotherapy- induced side effects have recently been reported in mice, indicating that bilberry extract suppresses myelotoxicity of 5-fluorouracil. Also, anthocyanins and anthocyanin-rich preparations have been shown to act as topoisomerase inhibitors, modulating the effect of topoisomerase poisons in vitro. Recent in vivo data of our group (project leader: D. Marko) indicate that anthocyanins suppress the effects of irinotecan on topoisomerase poisoning and DNA damage, its major mode of action, in the colon of rats. These results raise the question as to the potential impact and advantages but also risks of an intake of anthocyanin-rich preparations during chemo therapy. The proposal basically will clarify three important questions: 1) Does the oral intake of anthocyanin-rich berry extract/s compromise the efficacy of chemotherapy? 2) Can the epithelium of the gastro-intestinal tract be protected during chemotherapy by intake of anthocyanin-rich preparations without interfering with the therapeutic outcome? 3) Does the intake of anthocyanin-rich berry extract/s have an impact on the intestinal microbiome and vice versa, thus contributing to protective and/ or unwanted effects? The central piece of the proposal represent in vivo studies with tumor-bearing Balb/c and Balb/c- SCID (murine allograft model) mice (W. Berger). Since it was reported that the immune competence has a strong impact on certain chemotherapeutics, the intention of the proposal is a comparison of the effects between immune-competent and non-competent mice. A well characterized (analytical profiling) and most potent berry extract regarding DNA- and cyto- protection will be identified in vitro and investigated in depth in vivo. By applying state-of-the-art methods the impact on DNA integrity, morphology of gut epithelia; changes in kinetics of irinotecan degradation; modulation of immune response and composition of the intestinal microbiome will be investigated. By linking diet, chemotherapy and the intestinal microbiome in a unique way, we aim towards a better understanding of the complex processes in anticancer drug response.

Anthocyanins are red to blue-violet pigments that naturally give color to a variety of plant-based foods, such as different berries. Reports of potential positive health effects have led to great interest in anthocyanin-rich preparations and supplements. However, not every effect of anthocyanins can be considered entirely unproblematic. In cell culture systems, we have shown that anthocyanins, at higher concentrations, can act as inhibitors of topoisomerases. Topoisomerases are enzymes that regulate DNA topology and are increasingly required in rapidly dividing cells, such as tumor cells. Persistent inhibition of topoisomerases leads to DNA damage and, with intense damage, also to cell death. This principle is utilized in a range of chemotherapeutics. Pharmaceutical topoisomerase inhibitors, such as irinotecan, are used in the treatment of colon tumors. However, in cell culture, the simultaneous administration of anthocyanins and irinotecan weakens the effect of the chemotherapy in terms of inhibiting tumor cell growth. This has raised the question of whether the combination of anthocyanin-rich preparations with chemotherapy may affect the success of therapy in vivo. To investigate this, extracts from fresh fruit material were made from blackberry, blueberry, black currant, and elderberry. These extracts were comprehensively characterized in terms of their anthocyanin profile and further polyphenols. In cell culture, the effects of these extracts in combination with irinotecan were intensively studied in different models. Based on the cell culture experiments, elderberry extract was selected for further studies in tumor-bearing mice to clarify whether there is an interaction between food ingredients and chemotherapy in vivo as well. During therapy with irinotecan, elderberry extract was administered to the animals via gavage. This highlighted the particular role of the immune system. In animals with an intact immune system (Balb/c), a reduction in the therapy's effectiveness was observed when combining the chemotherapy with the elderberry extract. In contrast, immune-deficient mice (SCID) showed an enhancement of the therapeutic effect. Immune-deficient mouse models are used when, for example, human tumors are to be implanted in the animals. In recent years, findings have increasingly shown that the immune system plays a crucial role in fighting tumors. Therefore, in this project, we deliberately selected a mouse colon carcinoma (CT26) instead of a human tumor. This allowed us to carry out the studies on the combinatory effects of anthocyanin-rich extracts and chemotherapy in both immune-competent and immune-deficient animals. The immune-competent mouse model clearly holds more relevance for humans. The results of this animal study show that the oral intake of anthocyanin-rich extracts, such as those consumed in dietary supplements, can reduce the therapeutic success of irinotecan in the treatment of colon tumors. Therefore, it is strongly advised not to consume such supplements during chemotherapy.