Identification of macrophages in breast tumor microenvironment using label-free multiphoton microscopy

Abstract

Macrophages are at the center of the invasion and play a protumoral role in the tumor microenvironment. They can facilitate angiogenesis, extracellular matrix remodeling, invasion and migration of cancer cells, while inhibit the antitumoral immune surveillance. Tumor-associated macrophages are a major component of malignant tumors, which can stimulate the progress of tumors. In many human cancers, the presence of macrophages in tumor microenvironment has been correlated with unfavorable prognosis. Therefore, visual diagnosis of macrophages in tumor microenvironment is great significance for us to comprehend the occurrence and progress of tumor. Multiphoton microscopy (MPM) with subcellular resolution based on second harmonic generation (SHG) and two-photon excited fluorescence (TPEF) is very suitable for real-time detecting morphological and structural changes in biological tissues without tissue staining and exogenous probe molecule. In this study, we describe the use of label-free MPM for analyzing the intratumoral distribution and morphological changes of macrophages in breast tumor microenvironment. Our results indicated that MPM can accurately identify macrophages in breast tumor tissues. MPM images were well consistent hematoxylin and eosin (H&E) stained images. This work would provide the basis for further quantifying these changes using MPM. With the development of miniaturized imaging devices, MPM may be a promising imaging technique for clinicians to study various structural features in tumor microenvironment.