Natural Killer (NK) and CAR-NK Cell Expansion Method using Membrane Bound-IL-21-Modified B Cell Line
February 8th, 2022
Here, we present a method to expand peripheral blood natural killer (PBNK), NK cells from liver tissues, and chimeric antigen receptor (CAR)-NK cells derived from peripheral blood mononuclear cells (PBMCs) or cord blood (CB). This protocol demonstrates the expansion of NK and CAR-NK cells using 221-mIL-21 feeder cells in addition to the optimized purity of expanded NK cells.
Overview
This article presents a robust and reproducible protocol for the ex vivo expansion of functional, non-exhaustive, memory-like natural killer (NK) cells and chimeric antigen receptor (CAR)-modified NK cells. The method utilizes an Epstein-Barr virus (EBV)-transformed B cell line expressing a membrane-bound form of interleukin-21 (IL-21) as feeder cells, enabling the generation of large numbers of high-purity NK and CAR-NK cells from cord blood, peripheral blood, and solid organ tissues. This approach addresses a key bottleneck in the clinical development of CAR-NK immunotherapy by providing a scalable, 'off-the-shelf' cell source.
Key Study Components
Area of Science
- Immunotherapy
- Cellular engineering
- Cancer research
Background
- CAR-modified immune cell therapy is an emerging treatment for cancers and infectious diseases.
- NK-based immunotherapy, especially CAR-NK cells, offers promising 'off-the-shelf' therapeutic potential with reduced toxicity.
- Obtaining sufficient numbers of non-exhaustive, long-lived CAR-NK cells from third-party sources remains a challenge.
- Existing expansion protocols often require complex feeder cell systems and NK cell isolation steps.
Purpose of Study
- To develop a simplified, efficient protocol for expanding NK and CAR-NK cells ex vivo.
- To utilize a genetically modified EBV-transformed B cell line expressing membrane-bound IL-21 as feeder cells.
- To enable the production of clinically relevant quantities of functional NK and CAR-NK cells from various tissue sources.
Methods Used
- Preparation and sectioning of viable tissue to isolate lymphocytes.
- Enzymatic dissociation and density gradient centrifugation to obtain tissue-infiltrating lymphocytes.
- Coculture of peripheral blood mononuclear cells (PBMCs) with gamma-irradiated 221-mIL-21 feeder cells in media supplemented with IL-2 and IL-15.
- Retroviral transduction of expanded NK cells with CAR constructs using retronectin-coated plates and 293T-derived viral supernatant.
- Flow cytometry to assess NK cell purity and CAR transduction efficiency throughout expansion.
Main Results
- The protocol yields highly functional, non-exhaustive, memory-like NK cells with improved expansion compared to other feeder systems.
- NK cell purity is maintained at approximately 85% over a 21-day expansion period.
- CAR transduction efficiency reaches approximately 70% by Day 7 of culture.
- The expansion system is robust and reproducible, with up to 50,000-fold expansion of NK cells observed.
- The method is applicable to cells derived from cord blood, peripheral blood, and solid organ tissues, and can be adapted for other species.
Conclusions
- This protocol enables efficient, large-scale expansion of functional NK and CAR-NK cells suitable for immunotherapy applications.
- The use of 221-mIL-21 feeder cells simplifies the process by eliminating the need for prior NK cell isolation.
- The approach supports the clinical development of 'off-the-shelf' CAR-NK therapies for cancer and other diseases.
Frequently Asked Questions
Executive Industry Relevance
Achieving robust, scalable expansion of functional, non-exhaustive NK and CAR-NK cells is a critical inflection point for advancing 'off-the-shelf' immunotherapies in oncology and infectious disease pipelines. This membrane-bound IL-21-modified B cell feeder system addresses a key bottleneck by enabling high-yield, high-purity NK and CAR-NK cell production from diverse tissue sources. The method supports predictive confidence and portfolio progression by standardizing cell expansion for translational and preclinical applications.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables interrogation of NK cell-mediated cytotoxicity and functional target engagement in disease-relevant systems.
- Supports biological de-risking by generating memory-like, non-exhaustive NK cells for mechanistic studies.
- Facilitates predictive confidence in target validation through reproducible expansion and phenotypic consistency.
Screening & Assay Development
- Provides a standardized source of high-purity NK and CAR-NK cells for downstream cytotoxicity and functional assays.
- Improves assay reproducibility and scalability by eliminating the need for prior NK cell isolation.
- Enables quantitative assessment of cell expansion rates, purity, and CAR transduction efficiency for screening readiness.
Translational & Preclinical Research
- Aligns with translational biomarker strategies by supporting in vitro and in vivo functional validation of NK and CAR-NK cells.
- Ensures continuity from discovery through preclinical validation by providing consistent cell populations across studies.
- Reduces biological risk in preclinical advancement decisions through robust, reproducible expansion outputs.
Pipeline & Workflow Integration
This expansion protocol integrates from early discovery through preclinical research, supporting lead identification and translational continuity for cell-based immunotherapies.
- Discovery Biology: Enables hypothesis testing and pathway clarification using functional NK and CAR-NK cells.
- Screening: Delivers reproducible, quantitative outputs for assay development and compound evaluation.
- Analytics: Provides flow cytometry-based measurements of cell purity and CAR transduction efficiency for comparative analysis.
- Translational Research: Supports preclinical model development and biomarker alignment with scalable cell sources.
- Enterprise Reuse: Establishes a reusable, standardized expansion platform adaptable to multiple tissue sources and species.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in NK cell-based therapeutic development.
- Operational Value: Streamlines workflows through standardization, reproducibility, and elimination of NK cell isolation steps.
- Strategic Value: Enables better go/no-go decisions and capital efficiency by providing reliable, high-yield cell expansion.
- Portfolio Impact: Supports risk-adjusted prioritization and advancement of cell therapy candidates.
Implementation Considerations
- Requires expertise in cell culture, flow cytometry, and viral transduction techniques.
- Needs access to specialized instrumentation for tissue dissociation, cell sorting, and analytical validation.
- Demands cross-team standardization of expansion protocols and analytical endpoints.
- Adaptable to various tissue sources and potentially other species with protocol optimization.
- Dependent on quality of starting materials and careful handling to maintain reproducibility.
Biopharma FAQs
Chapters in this video
0:04
introduction
0:54
Natural Killer (NK) Cell Expansion from Liver Tissues: Day 0
3:14
Primary Natural Killer (NK) Cell Expansion from Peripheral Blood Mononuclear Cells (PBMCs): Day 0
4:34
Attachment of 293T Cells (Day 2) and Retrovirus Transfection (Day 3)
5:58
Retronectin Plate-Coating (Day 3) and Transduction (Day 4)
8:18
CAR-NK Cells Collection (Day 6 or 7)
9:04
Results: Expansion of PBNK Cells and Flow Cytometric Analysis of CAR-NK Cells
10:22
Conclusion
