Microfluidic Co-Culture Models for Dissecting the Immune Response in in vitro Tumor Microenvironments

Summary

In the age of immunotherapy and single-cell genomic profiling, cancer biology requires novel in vitro and computational tools for investigating the tumor-immune interface in a proper spatiotemporal context. We describe protocols to exploit tumor-immune microfluidic co-cultures in 2D and 3D settings, compatible with dynamic, multiparametric monitoring of cellular functions.

Abstract

Complex disease models demand cutting-edge tools able to deliver physiologically and pathologically relevant, actionable insights, and unveil otherwise invisible processes. Advanced cell assays closely mimicking in vivo scenery are establishing themselves as novel ways to visualize and measure the bidirectional tumor-host interplay influencing the progression of cancer. Here we describe two versatile protocols to recreate highly controllable 2D and 3D co-cultures in microdevices, mimicking the complexity of the tumor microenvironment (TME), under natural and therapy-induced immunosurveillance. In section 1, an experimental setting is provided to monitor crosstalk between adherent tumor cells and floating immune populations, by bright field time-lapse microscopy. As an applicative scenario, we analyze the effects of anti-cancer treatments, such as the so-called immunogenic cancer cell death inducers on the recruitment and activation of immune cells. In section 2, 3D tumor-immune microenvironments are assembled in a competitive layout. Differential immune infiltration is monitored by fluorescence snapshots up to 72 h, to evaluate combination therapeutic strategies. In both settings, image processing steps are illustrated to extract a plethora of immune cell parameters (e.g., immune cell migration and interaction, response to therapeutic agents). These simple and powerful methods can be further tailored to simulate the complexity of the TME encompassing the heterogeneity and plasticity of cancer, stromal and immune cells subtypes, as well as their reciprocal interactions as drivers of cancer evolution. The compliance of these rapidly evolving technologies with live-cell high-content imaging can lead to the generation of large informative datasets, bringing forth new challenges. Indeed, the triangle ''co-cultures/microscopy/advanced data analysis" sets the path towards a precise problem parametrization that may assist tailor-made therapeutic protocols. We expect that future integration of cancer-immune on-a-chip with artificial intelligence for high-throughput processing will synergize a large step forward in leveraging the capabilities as predictive and preclinical tools for precision and personalized oncology.

Introduction

The evolution of different branches of medicine as experimental disciplines has depended on the ability to manipulate cell population and organ functions under controlled conditions¹. Such ability has its roots in the availability of measurable models able to recapitulate processes happening in our body.

In the age of immunotherapy and single-cell genomic profiling², cancer biology needs to take advantage of emerging in vitro and computational models for investigating the tumor-immune interface in a proper spatiotemporal context^2,3.

Protocol

1. Chip design for adherent and floating cells 2D co-cultures

NOTE: The 2D co-culture layout (Figure 1A-C) is characterized by three chambers (100 µm high) interconnected by two sets of microchannel arrays (500 x 12 x 10 µm³, L×W×H). The intermediate chamber forms two closed dead-end compartments which block floating immune cells overflowing into the tumor site during the loading step 2.5. This device type is useful for real-time bidimensional measurements of single-cell (either adherent or floating) ....

Results

Tumor immune infiltration is a parameter of the host anti-tumor response. Tumors are heterogeneous in the composition, density, location, and functional state of infiltrating leukocytes which interactions with cancer cells can underlie clinically relevant information to predict disease course and response to therapy. In this sense, microfluidic technologies could be used as complementary and privileged in vitro tools to explore the immune contexture of tumors, as well as to monitor the response to anticancer therapies. T.......

Discussion

The described methods try to design a general approach to recapitulate, with modulable degree of complexity, two significant aspects in the field of onco-immunology, which can benefit from the adoption of more relevant in vitro models. The first one involves the tumor cell population side, where tackling single cell characteristics may lead to a better description of heterogeneity and correlated biological and clinical significance including resistance to therapy, propension to metastasis, stem cell and differentiation g.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cell culture materials
50 mL tubes	Corning-Sigma Aldrich, St. Louis, MO	CLS430828	centrifuge tubes
5-aza-2'-deoxycytidine DAC	Millipore-Sigma; St. Louis, MO	A3656	DNA-hypomethylating agent
6-well plates	Corning-Sigma Aldrich, St. Louis, MO	CLS3506	culture dishes
75 cm2 cell culture treated flask	Corning, New York, NY	430641U	culture flasks
A365M	American Type Culture Collection (ATCC), Manassas, VA	CVCL_B222	human melanoma cell line
Doxorubicin hydrochloride	Millipore-Sigma; St. Louis, MO	D1515	anthracycline antibiotic
Dulbecco's Modified Eagle Medium DMEM	EuroClone Spa, Milan, Italy	ECM0728L	Culture medium for SK-MEL-28  cells
Dulbecco's Phosphate Buffer Saline w/o Calcium w/o Magnesium	EuroClone Spa, Milan, Italy	ECB4004L	saline buffer solution
Fetal Bovine Serum	EuroClone Spa, Milan, Italy	ECS0180L	ancillary for cell culture
Ficoll	GE-Heathcare	17-1440-02	separation of mononuclear cells from human blood.
hemocytometer	Neubauer		Cell counter
Heparinized vials	Thermo Fisher Scientific Inc., Waltham, MA		Vials for venous blood collection
interferon alpha-2b	Millipore-Sigma; St. Louis, MO	SRP4595	recombinant human cytokine
L-Glutamine 100X	EuroClone Spa, Milan, Italy	ECB3000D	ancillary for cell culture
Liquid nitrogen
Lympholyte cell separation media	Cedarlane Labs, Burlington, Canada		Separation of lymphocytes by density gradient centrifugation
Lymphoprep	Axis-Shield PoC AS, Oslo, Norway
Matrigel	Corning, New York, NY	354230	growth factor reduced basement membrane matrix
MDA-MB-231	American Type Culture Collection (ATCC), Manassas, VA	HTB-26	human breast cancer cell line
Penicillin/ Streptomycin 100X	EuroClone Spa, Milan, Italy	ECB3001D	ancillary for cell culture
Pipet aid	Drummond Scientific Co., Broomall, PA	4-000-201	Liquid handling
PKH26 Red Fluorescent cell linker	Millipore-Sigma; St. Louis, MO	PKH26GL	red fluorescent cell dye
PKH67 Green fluorescent cell linker	Millipore-Sigma; St. Louis, MO	PKH67GL	green fluorescent cell dye
RPMI-1640	EuroClone Spa, Milan, Italy	ECM2001L	Culture medium for MDA-MB-231 cells
serological pipettes (2 mL, 5 mL, 10 mL, 25 mL, 50 mL)	Corning- Millipore-Sigma; St. Louis, MO	CLS4486; CLS4487; CLS4488; CLS4489; CLS4490	Liquid handling
sterile tips (1-10 μL, 10-20 μL, 20-200 μL, 1000 μL)	EuroClone Spa, Milan, Italy	ECTD00010; ECTD00020; ECTD00200; ECTD01005	tips for micropipette
Timer
Trypan Blue solution	Thermo Fisher Scientific Inc., Waltham, MA	15250061	cell stain to assess cell viability
Trypsin	EuroClone Spa, Milan, Italy	ECM0920D	dissociation reagent for adherent cells
Cell culture equipment
EVOS-FL fluorescence microscope	Thermo Fisher Scientific Inc., Waltham, MA		Fluorescent microscope for living cells
Humified cell culture incubator	Thermo Fisher Scientific Inc., Waltham, MA	311 Forma Direct Heat COIncubator; TC 230	Incubation of cell cultures at 37 °C, 5% CO2
Juli Microscope	Nanoentek
Laboratory refrigerator (4 °C)	FDM
Laboratory Safety Cabinet (Class II)	Steril VBH 72 MP		Laminar flow hood
Optical microscope	Zeiss
Refrigerable centrifuge	Beckman Coulter
Thermostatic bath
Microfabrication materials
3-Aminopropyl)triethoxysilane (Aptes)	Sigma Aldrich	A3648	silanizing agent for bonding PDMS to plastic coverslip
Chromium quartz masks / 4"x4", HRC / No AZ	MB W&A,  Germany		optical masks for photolithography
Glass coverslip, D 263 M Schott glass,  (170 ± 5 µm)	Ibidi, Germany	10812
Hydrogen Peroxide solution 30%	Carlo Erba Reagents	412081	reagents for piranha solution
Methyl isobutyl ketone	Carlo Erba Reagents	461945	PMMA e-beam resist developer
Microscope Glass Slides (Pack of 50 slides) 76.2 mm x 25.4 mm	Sail Brand	7101	substrates for bonding chips
Miltex Biopsy Punch with Plunger, ID 1.0mm	Tedpella		dermal biopsy punches for chip reservoirs
PMMA  950 kDa	Allresist,Germany	AR-P. 679.04	Positive electronic resists for patterning optical masks
Polymer untreated coverslips	Ibidi, Germany	10813	substrates for bonding chips
Prime CZ-Si Wafer,  4”, (100), Boron Doped	Gambetti Xenologia Srl, Italy	30255
Propan-2-ol	Carlo Erba Reagents	415238
Propylene glycol monomethyl ether acetate (PGMEA)	Sigma Aldrich	484431-4L	SU-8 resists developer
SU-8 3005	Micro resist technology,Germany	C1.02.003-0001	Negative Photoresists
SU-8 3050	Micro resist technology,Germany	C1.02.003-0005	Negative Photoresists
Suite of Biopunch, ID 4.0 mm, 6.0 mm, 8.0 mm	Tedpella	15111-40, 15111-60, 15111-80	dermal biopsy punches for chip reservoirs
Sulfuric acid 96%	Carlo Erba Reagents	410381	reagents for piranha solution
SYLGARD 184 Silicone Elastomer Kit	Dowsil, Dow Corning	11-3184-01	Silicone Elastomer (PDMS)
Trimethylchlorosilane (TMCS)	Sigma Aldrich	92360-100ML	silanizing agent for SU-8 patterned masters
Microfabrication equipment
100 kV e-beam litography	Raith-Vistec EBPG 5HR
hotplate
Optical litography system	EV-420 double-face contact mask-aligner
Reactive Ion Etching system	Oxford plasmalab 80 plus system
Vacuum dessicator