Dissociation of Human and Mouse Tumor Tissue Samples for Single-cell RNA Sequencing

Summary

This protocol outlines the procedure for rapidly dissociating human and mouse tumor samples for single-cell RNA sequencing.

Abstract

Human tumor samples hold a plethora of information about their microenvironment and immune repertoire. Effective dissociation of human tissue samples into viable cell suspensions is a required input for the single-cell RNA sequencing (scRNAseq) pipeline. Unlike bulk RNA sequencing approaches, scRNAseq enables us to infer the transcriptional heterogeneity in tumor specimens at the single-cell level. Incorporating this approach in recent years has led to many discoveries, such as identifying immune and tumor cellular states and programs associated with clinical responses to immunotherapies and other types of treatments. Moreover, single-cell technologies applied to dissociated tissues can be used to identify accessible chromatin regions T and B cell receptor repertoire, and the expression of proteins, using DNA barcoded antibodies (CITEseq).

The viability and quality of the dissociated sample are critical variables when using these technologies, as these can dramatically affect the cross-contamination of single cells with ambient RNA, the quality of the data, and interpretation. Moreover, long dissociation protocols can lead to the elimination of sensitive cell populations and the upregulation of a stress response gene signature. To overcome these limitations, we devised a rapid universal dissociation protocol, which has been validated on multiple types of human and murine tumors. The process begins with mechanical and enzymatic dissociation, followed by filtration, red blood lysis, and live dead enrichment, suitable for samples with a low input of cells (e.g., needle core biopsies). This protocol ensures a clean and viable single-cell suspension paramount to the successful generation of Gel Bead-In Emulsions (GEMs), barcoding, and sequencing.

Introduction

Although many advancements in cancer research have led to the development and FDA approval of agents targeting inhibitory receptors expressed on immune and tumor cells, known as checkpoint blockade inhibitors, therapy resistance and identifying mechanisms that drive patient response remain challenging¹. The complex challenge of characterizing tumor heterogeneity on its molecular diversity and the intricate interplay between tumor cells and the immune microenvironment necessitates new approaches to dissect this complex ecosystem at the single-cell resolution. Understanding the molecular intricacies within tumors and their microenvironments is pi....

Protocol

This study complied with all institutional guidelines regarding human tissue sampling. Informed consent was received from patients, and identifiable sample data was anonymized. Samples are collected in the operation room, placed in a solution of RPMI, saline, or PBS, and confirmed cancerous via the pathology department before use in research. All steps, except when indicated, should be carried out at 4 °C or on ice. Work inside a biosafety hood when processing human tissue. See the Table of Materials

Discussion

This protocol describes human or murine tumor samples dissociation into a single-cell suspension for scRNA sequencing using the 10x Genomics microfluidic system. In processing tissues that often come from rare cancers or are part of ongoing clinical trials or long experiments for murine tumors, the sample must be optimally and carefully preserved between all steps. All steps should be carried out rapidly on ice or at 4 ˚C to keep the native cellular RNA profiles and prevent degradation, as working at room temperatur.......

Materials

Name	Company	Catalog Number	Comments
1x PBS	Corning	21-040-CV
10 mL serological pipette	Corning	357551
1000 μL low-retention pipette tips	Rainin	30389213
1000 μL low-retention wide pipette tips	Rainin	30389218
1000 μL pipette tips	Rainin	30389212
10x Magnetic Separator	10x Genomics	120250
15 mL conical tubes	Corning	430052
2 mL aspirating pipette	Corning	357558
20 μL low-retention pipette tips	Rainin	30389226
20 μL pipette tips	Rainin	30389225
200 μL low-retention pipette tips	Rainin	30389240
200 μL pipette tips	Rainin	30389239
50 mL Polypropylene Conical Tube	Falcon	352098
60 x 15 mm Tissue Culture Dish	Falcon	353004
ACK Lysing Buffer	Gibco	A10492-1
BD 1 mL syringe	Becton, Dickinson and Company	3090659
Bright-Line Hemocytometer	Hausser Scientific	551660
Calcium Chloride Solution	Sigma Aldrich	2115-100ML
Cell Ranger	10x Genomics	N/A	https://www.10xgenomics.com/support/software/cell-ranger/latest
Cell counting slides for TC20 cell counter	Bio-Rad	1450015
CellTrics 30μm sterile disposable filters	Sysmex	04-004-2326
CellTrics 50μm sterile disposable filters	Sysmex	04-004-2327
Dead Cell removal Kit	Miltenyi Biotec	130-090-101	Store at -20 °C; kit 2
Dissecting Forceps, Fine Tip	VWR	82027-386
DNA LoBind Microcentrifuge tubes, 1.5 mL	Eppendorf	22431021
EasySepTM Dead Cell Removal (Annexin V) Kit	STEMCELL Technologies	17899	Store at 4 °C; Kit 1
Eppendorf centrifuge 5425R	Eppendorf	5406000640
Eppendorf centrifuge 5910R	Eppendorf	2231000657
Eppendorf Easypet 3 Electronic Pipette controller	Eppendorf	EP4430000018
Eppendorf Thermomixer F1.5 Model 5384	Eppendorf	EP5384000012
FBS	Gibco	26140-079	Store at 4 °C, use in a Biological hood
German Stainless Scissors	Fine Science Tools	14568-12
Leica Dmi1 Microscope	Leica Microsystems	454793
LS Column	Miltenyi Biotec	130-042-401
MACS Multistand	Miltenyi Biotec	130-042-303
Pipet-Lite LTS Pipette L-1000XLS+	Rainin	17014382
Pipet-Lite LTS Pipette L-200XLS+	Rainin	17014391
Pipet-Lite LTS Pipette L-20XLS+	Rainin	17014392
Quadro MACS Magnet	Miltenyi Biotec	130-091-051
RPMI Medium 1640 (1x)	Gibco	21870-076	Store at 4 °C
TempAssure 0.2 mL PCR 8-Tube strips	USA Scientific	1402-4700
Trypan blue stain 0.4%	Thermo Fisher Scientific	T10282
Tumor Dissociation Kit, Human	Miltenyi Biotec	130-095-929	Store at -20 °C, prepare enzymes according to kit instructions: Reconstitute lyophilized Enzyme H vial in 3 mL of RPMI 1640 Reconstitute lyophilized Enzyme R vial in 2.7 mL of RPMI 1640 Reconstitute lyophilized Enzyme A vial in 1 mL of Buffer A supplied with the kit.
Tumor Dissociation Kit, Mouse	Miltenyi Biotec	130-096-730	Store at -20 °C, prepare enzymes according to kit instructions: Reconstitute lyophilized Enzyme D vial in 3 mL of RPMI 1640 Reconstitute lyophilized Enzyme R vial in 2.7 mL of RPMI 1640 Reconstitute lyophilized Enzyme A vial in 1 mL of Buffer A supplied with the kit.
UltraPure Distilled Water	Invitrogen	10977-015	Store at 4 °C