Molecular and Immunologic Techniques in a Genetically Engineered Mouse Model of Gastrointestinal Stromal Tumor

Summary

The goal of this manuscript is to describe the Kit^V558Δ/+ mouse model and techniques for successful dissection and processing of mouse specimens.

Abstract

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and is typically driven by a single mutation in the KIT receptor. Across tumor types, numerous mouse models have been developed in order to investigate the next generation of cancer therapies. However, in GIST, most in vivo studies use xenograft mouse models which have inherent limitations. Here, we describe an immunocompetent, genetically engineered mouse model of gastrointestinal stromal tumor harboring a Kit^V558Δ/+ mutation. In this model, mutant KIT, the oncogene responsible for most GISTs, is driven by its endogenous promoter leading to a GIST which mimics the histological appearance and immune infiltrate seen in human GISTs. Furthermore, this model has been used successfully to investigate both targeted molecular and immune therapies. Here, we describe the breeding and maintenance of a Kit^V558Δ/+ mouse colony. Additionally, this paper details the treatment and procurement of GIST, draining mesenteric lymph node, and adjacent cecum in Kit^V558Δ/+ mice, as well as sample preparation for molecular and immunologic analyses.

Introduction

GIST is the most common sarcoma in humans with an incidence of about 6,000 cases in the United States of America¹. GIST appears to originate from the gastrointestinal pacemaker cells named the interstitial cells of Cajal, and is typically driven by a single mutation in the tyrosine kinase KIT or PDGFRA². Surgery is the mainstay of treatment for GIST and can be curative, but patients with advanced disease may be treated with the tyrosine kinase inhibitor (TKI), imatinib. Since its introduction over 20 years ago, imatinib has transformed the treatment paradigm in GIST, improving the survival in advanc....

Protocol

All mice were housed under pathogen-free conditions at the University of Pennsylvania according to NIH guidelines and with approval of the University of Pennsylvania IACUC. Euthanasia was performed following the University of Pennsylvania Laboratory Animal Resources standard operating procedures.

1. Kit^V558Δ/+ mouse breeding

1. Backcross the Kit^V558Δ/+ mice more than 10 times onto a C57BL/6J background using C57BL/6J mice. To do this, breed the male Kit^V558Δ/+ mice with female C57BL/6J mice at a 1:2 ratio.

Results

The Kit^V558Δ/+ mouse model allows for the investigation of therapeutics in an immunocompetent mouse model. Kit^V558Δ/+ mice have an average lifespan of 8 months due to progressive bowel obstruction (Figure 4). Tumors from Kit^V558Δ/+ mice express canonical markers of GIST including the tyrosine kinase KIT and the transmembrane channel DOG1 (Figure 5

Discussion

The Kit^V558Δ/+ mouse model is a powerful research tool in the molecular and immunologic analysis of GIST. Although the breeding strategy requires a single cross, using Kit^V558Δ/+ mouse cohorts in experiments analyzing tumor response requires extensive breeding. Mice should be age- and sex-matched to ensure similar tumor weights, and 10% of mice die before 8 weeks of age when tumors are established. Less extensive breeding strategies are possible if using advanced ima.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
100 micron filter	EMSCO	1194-2360
1x RBC lysis buffer	Life Technologies	00-4333-57
3mL syringe	Thermo Fisher Scientific/BD Biosciences	14823435
4–15% Mini-PROTEAN TGX Precast Protein Gels, 10-well, 30 µl	Bio-Rad	4561083
4% Paraformaldehyde Solution	Thermo Fisher Scientific	AAJ19943K2
40 micron filter	EMSCO	1194-2340
5M NaCl	Sigma Aldrich	S6546
70 micron filter	EMSCO	1194-2350
AKT antibody (C67E7)	Cell Signaling	4691
C57BL/6J mice	The Jackson Laboratory
Collagenase IV	Sigma Aldrich	C5138
Complete mini edta free protease inhibitor	Thomas Scientific	C852A34
Countess II Automated Cell Counter	Thermo Fisher Scientific
Disposable Scalpels	Thermo Fisher Scientific/Exel International	14-840-00
Dnase I	Thomas Scientific	C756V81
Dog1 antibody	abcam	ab64085
EDTA	Sigma Aldrich	E9884
ERK antibody (p44/42)	Cell Signaling	9102
FBS	Thomas Scientific	C788U23
FIJI software	FIJI		https://imagej.net/software/fiji
Fisherbrand 850 Homogenizer	Thermo Fisher Scientific	15-340-169
HBSS	University of Pennsylvania Cell Center
Imatinib mesylate	Selleck Chemicals	S1026
KIT antibody (D13A2)	Cell Signaling	3074
KitV558Δ/+ Genotyping	Transnetyx
Microcentrifuge tubes (1.5mL)	Thermo Fisher Scientific	05-408-129
Mouse on Mouse Immunodetection Kit, Basic	Vector Laboratories	BMK-2202
Nitrocellulose Membrane, Precut, 0.45 µm	Rio-Rad	1620145
Nonfat Dry Milk	Thermo Fisher Scientific	NC9121673
Nonidet P 40 Substitute	Sigma Aldrich	74385
p-AKT antibody (S473)	Cell Signaling	4060
p-ERK antibody (p44/42)	Cell Signaling	9101
p-KIT antibody (Y719)	Cell Signaling	3391
PMSF Protease Inhibitor	Thermo Fisher Scientific	36978
Proeinase K	Thermo Fisher Scientific	BP170050
Round-Bottom Polystyrene Test (FACS) Tubes	Falcon/Thermo Fisher Scientific	14-959-2A
RPMI	University of Pennsylvania Cell Center
Sodium fluoride (NaF)	Sigma Aldrich	201154
Sodium orthovanadate (Na3VO4)	Sigma Aldrich	S6508
SuperSignal West Dura Extended Duration Substrate	Thermo Fisher Scientific	34076
TBS buffer (10x)	University of Pennsylvania Cell Center
Tissue culture dish (100mm2)	Thermo Fisher Scientific/Falcon	08-772E
TrisHCL	Thermo Fisher Scientific	BP1757500
Tween 20	Rio-Rad	1706531
vivaCT 80 platform	Scanco medical