Development of Genetically Engineered Feeder Cells for Natural Killer Cell Expansion

BACKGROUND/AIM

To obtain sufficient numbers of high-quality natural killer (NK) cells, we developed feeder cells using synthetic biology techniques.

MATERIALS AND METHODS

K562 cells were engineered to express membrane bound interleukin-2 (mbIL2) or interleukin-13 (mbIL13).

RESULTS

The incubation of human primary NK cells isolated from peripheral blood mononuclear cells (PBMCs) with these feeder cells significantly increased the number of activated NK cells compared to K562 parental cells. Fluorescence-activated cell sorting (FACS) analysis demonstrated that NKG2D activating receptors were abundant on the surface of NK cells expanded by K562-mbIL2 or mbIL13 cells. NK cells expanded on K562-mbIL2 or mbIL13 lysed cancer cells more effectively than those cultured with normal K562 cells. Using NK cells incubated with our feeder cells, we developed anti-CD19 chimeric antigen receptor (CAR)-NK cells. They showed robust cytotoxic effect against CD19 positive cancer cell line.

CONCLUSION

Our newly developed feeder cells could provide useful tools for NK cell therapy.

A simple culture method for liver and intestinal tissue-resident macrophages from neonatal mice

The liver and intestine contain a remarkably large portion of tissue-resident macrophage cells representing a phenotype that downregulates inflammation and initiates tissue repair. Here, liver and intestinal tissues obtained from neonatal mice were minced, enzymatically digested, and incubated in RPMI1640-based media. In a 2-wk culture, spherical floating cells emerged on a fibroblastic sheet. These cells showed phagocytic activity and F4/80⁺-CD11b⁺-CD206⁺-Arg1⁺-iNOS^--CD209a^- phenotype, suggesting that these cells are tissue-resident macrophages. These macrophages proliferated in the co-culture system in the presence of fibroblastic feeder cell layer and absence of supplemental cytokines; the co-culture system did not cause a significant change in the phenotype of cells grown in a 4-wk culture. On the feeder cells, macrophage density was approximately 1.5 × 10⁴/cm² and the doubling time was approximately 70 h. Based on these observations, we present a simple method for the isolation and propagation of tissue-resident macrophages resembling M2 macrophage from neonatal mice, and this method provides a useful platform for in vitro studies of tissue-resident macrophages.

Rat-derived feeder cells immortalized by expression of mutant CDK4, cyclin D, and telomerase can support stem cell growth

The maintenance of stem cells often requires the support of feeder cells. Primary mouse embryonic fibroblasts (MEFs) have traditionally been used as feeder cells, and although these MEF-derived feeder cells have exhibited a reasonable performance, they require repeated cell isolation, since MEFs cannot expand indefinitely. To overcome this limitation, immortalized cells, such as STO cells, have been used. However, one major disadvantage is that previously reported immortalized cells can only support stem cell cultures for a relatively short period, typically 4 to 7 days. In this study, we found that our newly established rat-derived fibroblasts immortalized by the expression of mutant cyclin-dependent kinase 4, cyclin D, and telomerase reverse transcriptase, can function as feeder cells for relatively long cell culture periods of approximately 14 days. The rat-derived immortalized cells developed in this study should be a useful source of feeder cells to support stem cell research.

Copanlisib, a novel phosphoinositide 3-kinase inhibitor, combined with carfilzomib inhibits multiple myeloma cell proliferation

Multiple myeloma (MM) is a uniformly fatal disorder of B cells characterized by the accumulation of abnormal plasma cells. Phosphoinositide 3-kinase (PI3K) signaling pathways play a critical regulatory role in MM pathology. Copanlisib, also known as BAY80-6946, is a potent PI3Kα and δ inhibitor. In this study, we investigated the efficacy of copanlisib and a proteasome inhibitor using MM cell lines and primary samples. The p110α and δ catalytic subunits of the class PI3K increased, and carfilzomib activity reduced in the presence of a supernatant from the feeder cell line, HS-5. Phosphorylation of Akt and activation of caspase 3 and poly (ADP-ribose) polymerase (PARP) partially reduced upon carfilzomib treatment in the presence of HS-5. Apoptosis also decreased. Copanlisib treatment for 72 h inhibited growth in MM cell lines and induced apoptosis. Combination treatment of MM cells with carfilzomib and copanlisib caused greater cytotoxicity than that caused by either drug alone and increased apoptosis. Caspase 3 activity increased while that of Akt decreased after combination treatment with copanlisib and carfilzomib. Further, copanlisib inhibited vascular endothelial growth factor (VEGF)-mediated angiogenesis in vitro and in vivo. It also inhibited C-X-C motif chemokine 12 (CXCL12)-mediated chemotaxis. The data suggest that administration of the PI3K inhibitor, copanlisib, may be a powerful strategy against stroma-associated drug resistance of MM cells and can enhance the cytotoxic effects of proteasome inhibitors in such residual MM cells.

Human gingival fibroblast feeder cells promote maturation of induced pluripotent stem cells into cardiomyocytes

The use of human induced pluripotent stem (iPS) cells has been investigated in multiple regenerative medicine studies. However, although methods for efficient differentiation of iPS cells into heart tissues have been devised, it remains difficult to obtain cardiac tissue with high contractility. Herein, we established a method for differentiating iPS cells into highly contractile cardiomyocytes (CMs), and demonstrate that the use of human gingival fibroblasts (HGFs) as a feeder cells promotes maturation of iPS-derived CMs (iPS-CMs) in vitro. After CM differentiation of iPS cells, iPS-CMs showed increased mRNA expression of the CM specific maker cardiac troponin T (cTnT) in the absence and presence (on-feeder condition) of cocultured HGFs, and decreased expression of pluripotent markers was observed under both conditions. Protein expression of cTnT was also observed in immunocytochemical analyses, although on-feeder CMs showed comparatively robust sarcomere structure and significantly stronger contractility than feederless cardiomyocytes, suggesting that HGF feeder cells facilitate CM differentiation of iPS cells.

Effects of Feeder Cell Types on Culture of Mouse Embryonic Stem Cell In Vitro

The suitable feeder cell layer is important for culture of embryonic stem (ES) cells. In this study, we investigated the effect of two kinds of the feeder cell, MEF cells and STO cells, layer to mouse ES (mES) cell culture for maintenance of stemness. We compare the colony formations, alkaline phosphatase (AP) activities, expression of pluripotency marker genes and proteins of D3 cell colonies cultured on MEF feeder cell layer (D3/MEF) or STO cell layers (D3/STO) compared to feeder free condition (D3/-) as a control group. Although there were no differences to colony formations and AP activities, interestingly, the transcripts level of pluripotency marker genes, Pou5f1 and Nanog were highly expressed in D3/MEF (79 and 93) than D3/STO (61and 77) or D3/- (65 and 81). Also, pluripotency marker proteins, NANOG and SOX-2, were more synthesized in D3/MEF (72.8±7.69 and 81.2±3.56) than D3/STO (32.0±4.30 and 56.0±4.90) or D3/- (55.0±4.64 and 62.0±6.20). These results suggest that MEF feeder cell layer is more suitable to mES cell culture.

Choice of Feeders Is Important When First Establishing iPSCs Derived From Primarily Cultured Human Deciduous Tooth Dental Pulp Cells

Feeder cells are generally required to maintain embryonic stem cells (ESCs)/induced pluripotent stem cells (iPSCs). Mouse embryonic fibroblasts (MEFs) isolated from fetuses and STO mouse stromal cell line are the most widely used feeder cells. The aim of this study was to determine which cells are suitable for establishing iPSCs from human deciduous tooth dental pulp cells (HDDPCs). Primary cultures of HDDPCs were cotransfected with three plasmids containing human OCT3/4, SOX2/KLF4, or LMYC/LIN28 and pmaxGFP by using a novel electroporation method, and then cultured in an ESC qualified medium for 15 days. Emerging colonies were reseeded onto mitomycin C-treated MEFs or STO cells. The colonies were serially passaged for up to 26 passages. During this period, colony morphology was assessed to determine whether cells exhibited ESC-like morphology and alkaline phosphatase activity to evaluate the state of cellular reprogramming. HDDPCs maintained on MEFs were successfully reprogrammed into iPSCs, whereas those maintained on STO cells were not. Once established, the iPSCs were maintained on STO cells without loss of pluripotency. Our results indicate that MEFs are better feeder cells than STO cells for establishing iPSCs. Feeder choice is a key factor enabling efficient generation of iPSCs.

Development of NK cell expansion methods using feeder cells from human myelogenous leukemia cell line

Background

Natural killer (NK) cells constantly survey surrounding tissues and remove newly generated cancer cells, independent of cancer antigen recognition. Although there have been a number of attempts to apply NK cells for cancer therapy, clinical application has been somewhat limited because of the difficulty in preparing a sufficient number of NK cells. Therefore, ex vivo NK cell expansion is one of the important steps for developing NK cell therapeutics.

Methods

CD3⁺ depleted lymphocytes were cocultured with IL-2 and with feeder cells (peripheral blood mononuclear cells [PBMCs], K562, and Jurkat) for 15 days. Expanded NK cells were tested for cytotoxicity against cancer cell lines.

Results

We compared feeder activities of three different cells-PBMC, K562, and Jurkat. K562 expanded NK cells by almost 20 fold and also showed powerful cytotoxic activity against cancer cells. K562-NK cells remarkably expressed the NK cell activation receptors, NKG2D, and DNAM-1. K562-NK cells exhibited more than two-fold production of cytotoxic granules compared with Jurkat-NK cells, producing more perforin and granzyme B than naïve NK cells.

Conclusion

Our findings suggest that K562 are more efficient feeder cells than Jurkat or PBMCs. K562 feeder cells expanded NK cells by almost 20 fold and showed powerful cytotoxic activity against cancer cells. We herein propose an intriguing approach for a design of NK cell expansion.