A Human Glioblastoma Organotypic Slice Culture Model for Study of Tumor Cell Migration and Patient-specific Effects of Anti-Invasive Drugs

Summary

Current ex vivo models of glioblastoma (GBM) are not optimized for physiologically relevant study of human tumor invasion. Here, we present a protocol for generation and maintenance of organotypic slice cultures from fresh human GBM tissue. A description of time-lapse microscopy and quantitative cell migration analysis techniques is provided.

Abstract

Glioblastoma (GBM) continues to carry an extremely poor clinical prognosis despite surgical, chemotherapeutic, and radiation therapy. Progressive tumor invasion into surrounding brain parenchyma represents an enduring therapeutic challenge. To develop anti-migration therapies for GBM, model systems that provide a physiologically relevant background for controlled experimentation are essential. Here, we present a protocol for generating slice cultures from human GBM tissue obtained during surgical resection. These cultures allow for ex vivo experimentation without passaging through animal xenografts or single cell cultures. Further, we describe the use of time-lapse laser scanning confocal microscopy in conjunction with cell tracking to quantitatively study the migratory behavior of tumor cells and associated response to therapeutics. Slices are reproducibly generated within 90 min of surgical tissue acquisition. Retrovirally-mediated fluorescent cell labeling, confocal imaging, and tumor cell migration analyses are subsequently completed within two weeks of culture. We have successfully used these slice cultures to uncover genetic factors associated with increased migratory behavior in human GBM. Further, we have validated the model's ability to detect patient-specific variation in response to anti-migration therapies. Moving forward, human GBM slice cultures are an attractive platform for rapid ex vivo assessment of tumor sensitivity to therapeutic agents, in order to advance personalized neuro-oncologic therapy.

Introduction

The laboratory study of glioblastoma (GBM), is hindered by a lack of models that faithfully recapitulate the requisite pathologic characteristics of the human disease, namely tumor cell migration and invasion. Comparative studies of 2D and 3D in vitro invasion assays as well as 3D rodent slice culture models have uncovered mechanistically disparate cellular migration programs in these two contexts, potentially limiting the translatability of findings from 2D systems to the human disease^1,2,3. The organotypic tumor slice culture and imaging paradigm described here all....

Protocol

Before collection of patient tissue samples is initiated, informed consent must be obtained from each patient under an approved Institutional Review Board (IRB) protocol. The authors of this protocol received consent for the work described under approved IRB protocols at the University of Colorado Hospital and Inova Fairfax Hospital. Data collected from these slice cultures were not used to direct patient care decisions.

1. Pre-slicing Preparation

1. Prepare "tissue processing" media and "slice culture maintenance" media the day before planned tumor resection and tissue collection (or utilize previously generated me....

Results

Our group has successfully generated slice cultures from over 50 patients undergoing initial GBM resection. This slice generation, culture, retroviral-labeling, imaging, and migration analysis protocol has been streamlined into a reproducible workflow (Figure 1). Critically, these organotypic GBM slices demonstrate concordance with originating tumor tissue throughout culture, including maintenance of pathologic hallmarks and microglia up to 15 days in culture (Fig.......

Discussion

Organotypic slice cultures from human cancer tissue provide an attractive and underutilized platform for pre-clinical translational experimentation. Understanding of population-level behaviors of tumor cells with regards to migration, proliferation, and cell death in the native tumor microenvironment is lacking. Critically, studying tumor response to therapy in a dynamic, time-resolved fashion at the level of cell behavior may shed light on novel mechanisms of treatment resistance. Human tumor slice cultures provide a li.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
DMEM High Glucose	Invitrogen (Gibco)	11960-044
Neurobasal-A Medium, minus phenol red	Invitrogen (Gibco)	12349-015
B-27 Supplement (50x), serum free	Invitrogen (Gibco)	17504-044
Penicillin-Streptomycin (10,000 U/mL)	Invitrogen (Gibco)	15140-122
GlutaMAX Supplement	Invitrogen (Gibco)	35050-061
L-Glutamine (200 mM)	Invitrogen (Gibco)	25030-081
HEPES (1 M)	Invitrogen (Gibco)	15630-080
Nystatin Suspension	Sigma-Aldrich	N1638-20ML	10,000 unit/mL in DPBS, aseptically processed, BioReagent, suitable for cell culture
UltraPure Low Melting Point Agarose	Invitrogen (Gibco)	16520-050	Melts at 65.5 °C, Remains fluid at 37 °C, and sets rapidly below 25 °C.
Isolectin GS-IB4 from Griffonia simplicifolia, Alexa Fluor 647 Conjugate	Thermo Fisher (Molecular Probes)	I32450	Used in media to label Microglia/Macrophages
pRetroX-IRES-ZsGreen1 Vector	Clonetech	632520
Retro-X Concentrator	Clonetech	31455	Binding resin for non-ultracentrifugation concentration of viral supernatants
pVSG-G Vector	Clonetech	631530	part of the Retro-X Universal Retroviral Expression System
GP2-293 Viral packaging cells	Clonetech	631530	part of the Retro-X Universal Retroviral Expression System
Cyanoacrylate Glue (Super Glue)	Sigma-Aldrich	Z105899	Medium-viscosity
Equipment
Peel-A-Way Embedding Mold (Square - S22)	Polysciences, Inc.	18646A-1	Molds for tumor sample embedding
Stainless Steel Micro Spatulas	Fisher Scientific	S50823	Bend instrument 45 degrees at the neck of the spoon blade
Curved Fisherbrand Dissecting Fine-Pointed Forceps	Fisher Scientific	08-875
Single Edge Razor Blade (American Safety Razors)	Fisher Scientific	17-989-001	Blade edge is 0.009" thick. Crimped blunt-edge cover is removed before loading onto vibratome.
Leica VT1000 S Vibratome	Leica Biosystems	VT1000 S
Hydrophilic PTFE cell culture insert	EMD Millipore	PICM0RG50	30 mm, hydrophilic PTFE, 0.4 µm pore size
35 mm Glass Bottom Dishes	MatTek	P35G-1.5-20-C Sleeve	20 mm glass diameter. Coverslip glass thickness 1.5 mm
LSM 510 Confocal Micoscope	Zeiss	LSM 510	10x Air Objective (c-Apochromat NA 0.45)
PECON Stagetop Incubator	PeCON Germany	(Discontinued)	Incubator PM 2000 RBT is a comprable product designed for use with Zeiss Microscopes.