Imaging glioma cell invasion in vivo reveals mechanisms of dissemination and peritumoral angiogenesis

Abstract

Infiltration of cancer cells into normal tissue is a hallmark of malignant gliomas and compromises treatment options. A lack of appropriate models limits the study of this invasion in vivo, which makes it difficult to fully understand its anatomy and the role of dynamic interactions with structures of the normal brain. We developed a novel methodology by utilizing multiphoton laser scanning microscopy (MPLSM) to image the movement of glioma cells deep within the normal brain of live mice in real time. This allowed us to track the invasion of individual RFP-expressing GL261 cells in relation to perfused vasculature or GFP-labeled endothelial cells repetitively over days, up to a depth of 0.5 mm. Glioma cells moved faster and more efficiently when the abluminal site of a blood vessel was utilized for invasion. Cells that invaded perivascularly were frequently found next to (a) multiple capillary structures where microvessels run parallel to each other, (b) capillary loops or glomeruloid-like bodies, and (c) dilated capillaries. Dynamic MPLSM for more than 48 h revealed that single invasive glioma cells induced intussusceptive microvascular growth and capillary loop formation, specifically at the microvascular site with which they had contact. As the main tumor grew by cooption of existing brain vessels, these peritumoral vascular changes may create a beneficial environment for glioma growth. In conclusion, our study revealed new mechanisms of peritumoral angiogenesis and invasion in gliomas, providing an explanation for their interdependence.

TNF-α respecifies human mesenchymal stem cells to a neural fate and promotes migration toward experimental glioma

“…(b) Semiquantitative visual analysis of spheroid infiltration after 42 h (day 2) of confrontation under the above described conditions allows for noninvasive serial detection of brain tumors and metastasis on a cellular resolution in vivo. 23,24 Using this experimental approach, we now showed hMSC tropism toward experimental glioma in mice, which is in accordance to previous results. 5 Importantly, pretreatment of hMSCs with TNF-a potentiates the glioma-specific recruitment of hMSCs applied by intravenous injection.…”

“…To address this, we compared the extent with which hMSCs and hMSCs preincubated with TNF-a were able to selectively integrate into intracranial human glioma xenografts in nude mice using a chronic cranial window and in vivo multiphoton laser scanning microscopy (MPLSM). 23,24 Microscopic images of representative tumor regions acquired 24 h after intravenous injection of quantum dot-labeled hMSCs revealed that hMSCs had infiltrated the growing glioma (Figure 6a). Importantly, preincubation with TNF-a massively increased the number of hMSCs recruited to the tumor (Figure 6b).…”

Optical Barcoding for Single-Clone Tracking to Study Tumor Heterogeneity

“…33 This could be of relevance for analysis of stem cell populations that reside in defined anatomical spaces (e.g., as defined by hypoxia or vascular proximity), thereby enabling evaluation of their functional properties in their anatomical context. 34,35 Taken together, we have demonstrated that optical barcoding is a powerful tool that allows identification, quantification, tracking, and sorting of clonal subpopulations, as well as their functional assessment in vitro and in vivo. Complex heterogeneous systems are the result of the expansion of specific subpopulations driven by endogenous growth advantages, signaling networks, and selective pressure of the microenvironment.…”

Coculture System with an Organotypic Brain Slice and 3D Spheroid of Carcinoma Cells

“…Despite these observations, however, up to now there is no suitable in vivo/in vitro model available to directly visualize glial reactions during cerebral metastasis formation, in particular by bright field microscopy. Recent in vivo live imaging of carcinoma cells demonstrated their cerebral colonization behavior 8 . However, this method is very laborious, costly and technically complex.…”

“…Furthermore, in vivo imaging is thus far limited to the visualization of the carcinoma cells, whereas interactions with resident cells have not yet been illustrated. Finally, investigations of human carcinoma cells within immunocompetent animals are impossible 8 .…”