Organotypic Slice Cultures as Preclinical Models of Tumor Microenvironment in Primary Pancreatic Cancer and Metastasis

Summary

This protocol describes the preparation of organotypic slice cultures (OTSCs). This technique facilitates the ex vivo cultivation of intact multicellular tissue. OTSCs can be used immediately to test for their respective response to drugs in a multicellular environment.

Abstract

Realistic preclinical models of primary pancreatic cancer and metastasis are urgently needed to test the therapy response ex vivo and facilitate personalized patient treatment. However, the absence of tumor-specific microenvironment in currently used models, e.g., patient-derived cell lines and xenografts, only allows limited predictive insights. Organotypic slice cultures (OTSCs) comprise intact multicellular tissue, which can be rapidly used for the spatially resolved drug response testing.

This protocol describes the generation and cultivation of viable tumor slices of pancreatic cancer and its metastasis. Briefly, tissue is casted in low melt agarose and stored in cold isotonic buffer. Next, tissue slices of 300 µm thickness are generated with a vibratome. After preparation, slices are cultured at an air-liquid interface using cell culture inserts and an appropriate cultivation medium. During cultivation, changes in cell differentiation and viability can be monitored. Additionally, this technique enables the application of treatment to viable human tumor tissue ex vivo and subsequent downstream analyses, such as transcriptome and proteome profiling.

OTSCs provide a unique opportunity to test the individual treatment response ex vivo and identify individual transcriptomic and proteomic profiles associated with the respective response of distinct slices of a tumor. OTSCs can be further explored to identify therapeutic strategies to personalize treatment of primary pancreatic cancer and metastasis.

Introduction

Existing preclinical models of pancreatic ductal adenocarcinoma (PDAC) and respective metastases are poor predictors of response to treatment in patients which is a major drawback in drug development and the identification of predictive biomarkers¹. Although models such as patient-derived organoids and patient-derived xenografts are promising, their use remains limited². Major limitations of these in vitro models are the lack of the tumor microenvironment and xenografting in non-human immunocompromised species. Especially in PDAC and its metastases, the tumor microenvironment has considerably gained interest ove....

Protocol

Tissue specimens were collected and processed after approval by the local ethics committee of the University of Lübeck (# 16-281).

1. Fresh tissue collection and handling

NOTE: Every unfixed human tissue specimen should be handled with caution to prevent the risk of infection from blood-borne pathogens. All patients should be tested to be negative for HIV, HBV, and HCV prior to tissue processing. Wear a protective coat and handle human tissue specimens with glove.......

Discussion

OTSCs of fresh tumor samples are a close approximation of the tumor in situ. They maintain their baseline morphology, proliferative activity, and microenvironment during the cultivation for a defined, tissue-dependent period^11,12,13. This technique enables the immediate application of treatment to viable human tumor tissue ex vivo and subsequent downstream analyses, such as profiling of the transcriptome and pr.......

Materials

Name	Company	Catalog Number	Comments
Advanced DMEM/F-12 Medium	Gibco	12634028
Agarose Low Melt	Roth	6351.2	8% in Ringer solution
Antibody Diluent, Background Reducing	Dako	S3022
AquaTex	Merck	108562
Bioethanol (99%, denatured)	CHEMSolute	2,21,19,010
Citric Acid monohydrate	Sigma Aldrich	C7129
Cleaved Caspase-3 (Asp175) (5A1E) Rabbit mAb	Cell Signalling Technology	9664	1:400 dilution
Derby Extra Double Edge Safety Razor Blades	Derby Tokai
Embedding cassettes	Roth	H579.1
Eosin Y-solution 0,5% aqueous	Merck	10,98,44,100
Eukitt Quick hardening mounting medium	Sigma-Aldrich	3989
Fetal bovine serum	Gibco	10270106
Formaldehyde solution 4,5%, buffered	Büfa Chemikalien	B211101000
Hem alum solution acid acc. to Mayer	Roth	T865
Human EGF	Milteniy Biotec	130-097-794
Hydrocortisone	Sigma Aldrich (Merck)	H0888
Hydrogen peroxide 30%	Merck	1,08,59,71,000
Insulin human	Sigma Aldrich (Merck)	12643
Liquid DAB+ Substrate Chromogen System	Dako	K3468
MACS Tissue Storage Solution	Milteniy Biotech	130-100-008
Methanol	Merck	############
Microscope Slides Superfrost Plus	Thermo Scientific	J1800AMNZ
Millicell Cell Culture Insert, 30 mm, hydrophilic PTFE, 0.4 µm	Millipore (Merck)	PICM0RG50
Monoclonal mouse anti-human  Cytokeratin 7 (Clone OV-TL 12/30)	Dako	M7018	1:200 dilution
Monoclonal mouse anti-human Ki67 Clone MIB-1	Dako	M7240	1:200 dilution
Monoclonal mouse Anti-vimentin (Clone V9)	Dako	M0725	1:200 dilution
Negative control Mouse IgG2a	Dako	X0943	1:200 dilution
Negative control Mouse IgG1	Dako	X093101-2	1:200 dilution
Paraffin (melting temperature 56°- 58°)	Merck	10,73,37,100
Penicillin-Streptomycin (10.000 U/ml)	Gibco	15140122
PBS pH 7,4 (1x) Flow Cytometry Grade	Gibco	A12860301
Resazurin sodium salt; 10 mg/ml in PBS	Sigma Aldrich	R7017	1:250 dilution
Ringer's solution	Fresenius Kabi	2610813
RPMI-1640 Medium	Sigma Aldrich (Merck)	R8758
Tissue culture testplate 6	TPP	92006
Triton X-100	Sigma Aldrich	9002-93-1
VECTASTAIN Elite ABC-Peroxidase Kit	Vector Laboratories	PK-6200
Xylene (extra pure)	J.T.Baker	8,11,85,000
Equipment
ClarioStar Microplate Reader	BMG Labtech
Paraffin Embedding Center E61110	Leica
Rotary Microtome Microm HM355S	Thermo Scientific
Section Transfer System Microm STS	Thermo Scientific
VT 1200S Vibratom	Leica