Vascular response patterns to targeted therapies in murine breast cancer models with divergent degrees of malignancy

Abstract

Background Response assessment of targeted cancer therapies is becoming increasingly challenging, as it is not adequately assessable with conventional morphological and volumetric analyses of tumor lesions. The tumor microenvironment is particularly constituted by tumor vasculature which is altered by various targeted therapies. The aim of this study was to noninvasively assess changes in tumor perfusion and vessel permeability after targeted therapy in murine models of breast cancer with divergent degrees of malignancy. Methods Low malignant 67NR or highly malignant 4T1 tumor-bearing mice were treated with either the multi-kinase inhibitor sorafenib or immune checkpoint inhibitors (ICI, combination of anti-PD1 and anti-CTLA4). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with i.v. injection of albumin-binding gadofosveset was conducted on a 9.4 T small animal MRI. Ex vivo validation of MRI results was achieved by transmission electron microscopy, immunohistochemistry and laser ablation-inductively coupled plasma-mass spectrometry. Results Therapy-induced changes in tumor vasculature differed between low and highly malignant tumors. Sorafenib treatment led to decreased tumor perfusion and endothelial permeability in low malignant 67NR tumors. In contrast, highly malignant 4T1 tumors demonstrated characteristics of a transient window of vascular normalization with an increase in tumor perfusion and permeability early after therapy initiation, followed by decreased perfusion and permeability parameters. In the low malignant 67NR model, ICI treatment also mediated vessel-stabilizing effects with decreased tumor perfusion and permeability, while ICI-treated 4T1 tumors exhibited increasing tumor perfusion with excessive vascular leakage. Conclusion DCE-MRI enables noninvasive assessment of early changes in tumor vasculature after targeted therapies, revealing different response patterns between tumors with divergent degrees of malignancy. DCE-derived tumor perfusion and permeability parameters may serve as vascular biomarkers that allow for repetitive examination of response to antiangiogenic treatment or immunotherapy.

Intratumoral heterogeneity after targeted therapy in murine cancer models with differing degrees of malignancy

“…In comparison, both ICI combination treatment and sorafenib led to a decrease in size of 67NR tumors ( Figs. 3 b, 5 b) [ 10 , 8 ]. Mean values, standard deviation, as well as statistics for all results can be found in Supplementary Tables 1–5.…”

“…Mean values, standard deviation, as well as statistics for all results can be found in Supplementary Tables 1–5. Data of three-dimensional tumor volumes of the 4T1 model have been published before [ 10 , 8 ].…”

“…In highly malignant 4T1 tumors, sorafenib did not cause a reduction in tumor growth. This effect was only visible in low malignant 67NR tumors [ 8 , 10 ]. The increase in tumor size for 4T1 tumors after ICI treatment was visually mainly due to extensive intratumoral hemorrhage, visible in HE staining, while sizes of 67NR tumors were decreased after ICI treatment in comparison to untreated control tumors.…”

“…1. This study analyzes a variety of MRI sequences that have been acquired in a larger study, with some results, especially regarding three-dimensional tumor volume, already published [ 10 , 8 ].…”

“…This study emphasizes the applicability of such an imaging approach to highly and low malignant variants of murine breast cancer. Treatment effects especially of anti-angiogenic therapies differ between the two tumor models, as highly malignant tumors have immature, distorted vessels, whereas low malignant tumors show more organized tumor vessels, with features closer to physiological vasculature [8] .…”