Abstract
Abstract The tumor microenvironment plays a critical role in the efficacy of chemotherapy. The disorganized vasculature within solid tumors leads to decreased drug delivery to the tumor and poor penetration of drugs from blood vessels to the tumor cells. Our laboratory has shown limited distribution of the auto-fluorescent drugs doxorubicin and mitoxantrone using quantitative immunohistochemistry. However, most anti-cancer drugs are not fluorescent and do not have antibodies that recognize them. The aim of the present study is to characterize the spatial distribution within solid tumors of biomarkers of drug effect: cleaved caspase 3 (a marker of apoptosis), γH2aX (a marker of DNA damage) and Ki67 (a marker of cell proliferation) in relation to blood vessels (recognized by an antibody to CD31). We have quantified the time-dependent distribution of these biomarkers in two models: human breast cancer MDA-MB-231 xenografts and murine mammary EMT6 syngeneic tumors following treatment with doxorubicin and melphalan respectively. Biomarker distributions have been compared to distributions of doxorubicin fluorescence. Melphalan's distribution within a solid tumor has been assessed for the first time with the use of a melphalan-DNA adduct recognizing monoclonal antibody. These studies are designed to provide a basis for selecting biomarkers to reflect the distribution of other non-fluorescent agents. The distribution of doxorubicin decreases exponentially with increasing distance from blood vessels, and is similar to the distribution of γH2aX at 10 minutes after drug injection. The activation of cleaved caspase 3 (indicating apoptosis) at 24 and 48 hours following treatment also mirrors the distribution of doxorubicin. The analysis of biomarker distributions in EMT6 tumors following treatment with melphalan in relation to tumor blood vessels is in progress. The results of these studies will be applied to quantify the intratumoral distribution of other non-fluorescent anticancer drugs (hypoxia-activated pro-drugs). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 560. doi:10.1158/1538-7445.AM2011-560
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