P2-10-03: Non-Invasive In Vivo Characterization of Cancer-Cell Proliferation & Angiogenesis in Cancer-Cell-Surrounding Stromal Microenvironment In-Vivo Using Diffuse Optical Tomography.

Abstract

Abstract Background: Cancer cell proliferation and stromal microenvironment changes have been shown to indicate tumor growth (Orimo, Weinberg et al., Cell, 2005, Coussens and Werb, Nature, 2002). However, most studies were performed using excised tissue samples or cultured cells. In-vivo characterization of these properties in human breast cancer could magnify the importance of recent findings from in-vitro tissues. Diffuse Optical Tomography (DOT) provides quantitative three-dimensional (3D) images of the physiological and pathological properties of breast cancer tissues in vivo. In this study, we investigate the relationship between DOT measured physiological parameters, such as hemoglobin & tissue oxygenation that differentiate malignant, benign and normal breast tissues (Choe, Yodh et al. JBO, 2009), and histologically quantified Ki67 expression in cancer cell nuclei and vasculature in the stromal microenvironment surrounding breast cancer cells. Methods: DOT was employed to measure 20 infiltrating ductal carcinoma patients. DOT utilizes non-ionizing low power near infrared light to examine a subject laying in the prone position on a bed with her breasts inside a breast box. DOT quantifies oxy- and deoxy-hemoglobin concentration and tissue oxygenation. Cancer proliferation was quantified by calculating Ki67 stained nuclei percent and vascular area (calculated by detecting CD34 stained vascular structure using automated RGB based software). Results: The ratio of Ki67 expression in cancer cells to surrounding normal cells was correlated with DOT-measured tumor-to-normal ratio of volume-averaged oxy-hemoglobin and tissue oxygen saturation (R=0.72, p-value: 0.0197 and R=0.68, p-value: 0.0293, respectively, N=10). The vascular area (μm2) the surrounding stroma was correlated with total hemoglobin concentration and oxy-hemoglobin (R=0.49, p-value: 0.1238 and R=0.43, p-value: 0.1819, respectively, N=11). Additionally, cancer-to-normal ratio of nuclei compactness and cancer micro-vessel density was correlated with tumor-to-normal ratio of oxy-hemoglobin concentration (R=0.43, p-value: 0.056 and R=0.43, p-value:0.058, respectively, N=20). Discussion: The positive correlations between Ki67 cancer-proliferation-marker and tissue oxy-hemoglobin concentration indicate that DOT detects increased oxygenated environment for proliferating cells. The observation that nuclei compactness increases with oxy-hemoglobin concentration also supports the statement above, and, the correlation between hemoglobin concentration and vascular area in surrounding stroma suggests that DOT measures tumor growth stimulated by stromal micro-environment changes. The difference between the field of view needed to calculate a parameter value (i.e., macroscopic (cm3) for DOT and microscopic (|im3) for histology) likely lowers the correlation between the two technologies. However, the results of this study clearly suggest that DOT measures tumor growth due to proliferation of cancer cells and angiogenesis in cancer-cell-surrounding stroma. This work was supported by NIH and the Susan G. Komen for the Cure foundation. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-10-03.