Effects of Irinotecan on Tumor Vasculature and Oxygenation: An in vivo Study on Colorectal Cancer Model

The effects of chemotherapy on the tumor microenvironment remain poorly investigated, although these are crucial for the drug delivery and anti-tumor activity and can modify physiological behavior of cancer cells. Optical coherence angiography and phosphorescence lifetime spectroscopy are promising optical methods to characterize both tumor vasculature and its oxygenation, respectively. In this study, we used these methods to explore the influence of irinotecan, a widely used chemotherapeutic agent, on tumor angiogenesis and oxygen content in a mouse model of colorectal cancer in vivo . For the first time, it was shown that irinotecan at conventional dosing reduces tumor oxygenation and blood perfusion via antiangiogenic mechanism of action. Immunohistochemistry for hypoxia and for the endothelial cell marker CD31 verified the in vivo findings. These data show the prospects of the optical techniques to monitor tumor microenvironment in the course of chemotherapy, which can help to optimize and individualize the treatment.