A murine model of targeted infusion for intracranial tumors

Abstract

Historically, intra-arterial (IA) drug administration for malignant brain tumors including glioblastoma multiforme (GBM) was performed as an attempt to improve drug delivery. With the advent of percutaneous neuorovascular techniques and modern microcatheters, intracranial drug delivery is readily feasible; however, the question remains whether IA administration is safe and more effective compared to other delivery modalities such as intravenous (IV) or oral administrations. Preclinical large animal models allow for comparisons between treatment routes and to test novel agents, but can be expensive and difficult to generate large numbers and rapid results. Accordingly, we developed a murine model of IA drug delivery for GBM that is reproducible with clear readouts of tumor response and neurotoxicities. Herein, we describe a novel mouse model of IA drug delivery accessing the internal carotid artery to treat ipsilateral implanted GBM tumors that is consistent and reproducible with minimal experience. The intent of establishing this unique platform is to efficiently interrogate targeted anti-tumor agents that may be designed to take advantage of a directed, regional therapy approach for brain tumors.

Keywords: GBM; Glioblastoma multiforme; Infusion; Intra-arterial; Mouse; Regional cancer therapy.

Fig. 1

The necessary instruments needed to perform ICA infusions are commonly available in most labs including a light source, dissecting microscope, a hotplate, and a peristaltic pump (a). Following either inhaled or injected anesthesia, neck hyperextension is required for exposure of the carotid triangle (b). Schematic representation of each step of the ICA infusion in the carotid triangle containing CCA (black arrow), IJV (white arrowhead), and vagus nerve (black arrowhead) including catheter placement and eventual CCA ligation (c). Photomicrograph via a dissecting microscope (magnification, 6.5X to 35X) shows CCA (black arrow), IJV (white arrowhead) and vagus nerve (black arrowhead) (d). CCA was anchored with 5-0 black silk (white asterisk) (e). CCA was visualized as ICA (black arrow) and ECA (white arrow) diverged (f). A small arteriotomy (arrow) was made in the CCA with microscissors after applying 5-0 black silk (white asterisk) and a vascular clip (black asterisk) (g). A microcatheter (arrow) was cannulated through the arteriotomy (h) and secured with black silk ties (i). Two black silk ties (white asterisk) were permanently applied after removing the catheter (j).

Fig. 2

Representative photomicrograph of gross examination of brain after infusion with 2% Evans Blue dye demonstrates selective delivery with ICA infusion. The infused left hemispheric vessels were intact and stained predominantly in the ventral (a) and dorsal views (b) compared to the right hemisphere. (n=2 mice)

Fig. 3

Orthotopic U87MG xenografts were assessed by gross (a), H&E (b), and Giemsa staining (c). Tumors (asterisk) were large and well established in the left hemisphere and measured 3.4 x 5 mm in maximum diameters in perpendicular axes (c, d). Striatum destruction and cortex compression were detected microscopically with DAPI staining (e).

Fig. 4

Similar to human GBM, GFAP (red) with DAPI (blue) counterstaining demonstrated the diffuse distribution of astrocytes with a well-defined border and scattered GFAP positive cells throughout the tumor (a) and typical branched cell morphology at higher magnification (inset). Bizarre mitotic figures are visualized throughout the tumor including a tripolar mitotic figure (b) magnified in inset. Reflectinig toxicity, vacuolated nuclei were noted with Giemsa staining after melphalan ICA infusion (c). Background DAPI staining of tumor nuclei (blue), Ki67 staining of tumor cells (red) shows a high level of mitotic activity and no response to melphalan (d), which corresponded to minimal apoptotic tumor cells (red) detected by TUNEL staining (e).