Heterogeneity of macrophage infiltration and therapeutic response in lung carcinoma revealed by 3D organ imaging

Abstract

Involvement of the immune system in tumour progression is at the forefront of cancer research. Analysis of the tumour immune microenvironment has yielded a wealth of information on tumour biology, and alterations in some immune subtypes, such as tumour-associated macrophages (TAM), can be strong prognostic indicators. Here, we use optical tissue clearing and a TAM-targeting injectable fluorescent nanoparticle (NP) to examine three-dimensional TAM composition, tumour-to-tumour heterogeneity, response to colony-stimulating factor 1 receptor (CSF-1R) blockade and nanoparticle-based drug delivery in murine pulmonary carcinoma. The method allows for rapid tumour volume assessment and spatial information on TAM infiltration at the cellular level in entire lungs. This method reveals that TAM density was heterogeneous across tumours in the same animal, overall TAM density is different among separate pulmonary tumour models, nanotherapeutic drug delivery correlated with TAM heterogeneity, and successful response to CSF-1R blockade is characterized by enhanced TAM penetration throughout and within tumours.

Imaging macrophage distribution and density in mammary tumors and lung metastases using fluorine‐19 MRI cell tracking

“…The observation of 19 F signal in 4T1 lung metastases was heterogeneous; not every lung metastasis visible in the proton images had 19 F signal. Heterogeneous TAM recruitment to metastases has been reported before in a different model of lung carcinoma for which MAMs were identified using confocal microscopy (41). The resolution of our 19 F imaging technique is relatively low and does not permit detection of very low numbers of PFC-labeled cells.…”

“…Cuccarese et al showed that macrophages surrounded early-stage tumors in a mouse model of lung metastases. Using optical tissue clearing and 3D confocal microscopy, they found significant TAM infiltration-associated with as few as 16 individual tumor cells within a single nascent nodule (41). Our future work will look more closely at the timing of accumulation of MAMs in lung metastases.…”

Intracellular and extracellular TGF-β signaling in cancer: some recent topics

“…The development of novel techniques, including intravital imaging, has helped demonstrate the roles of the epithelial plasticity program in cancer. More recently, tissue-clearing based 3D imaging strategies have been applied to cancer models, and these techniques have enabled the visualization of cancer micrometastases throughout the body [112,113]. One of the tissue-clearing protocols, clear unobstructed brain/body imaging cocktails (CUBIC)-based cancer analysis, allowed spatiotemporal visualization and quantification of the metastatic cancer cells at single cell resolution [113].…”

Wide-field dynamic monitoring of immune cell trafficking in murine models of glioblastoma

“…[4][5][6] Furthermore, TAMs have been shown to respond to and influence the efficacy of radiation, 7 immunotherapy, 5,8 and other cancer treatment strategies. 4,9,10 In this context, medical imaging technologies have proven indispensible to the exploration of TAM behaviors in vivo and their therapeutic potential and limitations. An especially useful strategy has been to exploit the robust phagocytic capacity of TAMs to accumulate nanoparticles that produce strong magnetic or fluorescent contrast, after which labeled cells can be detected in vivo using magnetic resonance imaging (MRI) or intravital microscopy (IVM).…”

“…An especially useful strategy has been to exploit the robust phagocytic capacity of TAMs to accumulate nanoparticles that produce strong magnetic or fluorescent contrast, after which labeled cells can be detected in vivo using magnetic resonance imaging (MRI) or intravital microscopy (IVM). 4,[9][10][11][12] MRI and IVM respectively provide favorable imaging depth and sub-cellular resolution, however the physical detection limits of each method impede the simultaneous achievement of these properties. Optical Coherence Tomography (OCT) 13 has been demonstrated as an alterative method for studying glioblastoma vasculature and infiltration at highresolution, 14,15 however this technique has not yet been adapted for detecting specific cell populations.…”