Engineering T cell receptor fusion proteins using nonviral CRISPR/Cas9 genome editing for cancer immunotherapy

Manufacture of chimeric antigen receptor (CAR)-T cells usually involves the use of viral delivery systems to achieve high transgene expression. However, it can be costly and may result in random integration of the CAR into the genome, creating several disadvantages including variation in transgene expression, functional gene silencing and potential oncogenic transformation. Here, we optimized the method of nonviral, CRISPR/Cas9 genome editing using large donor DNA delivery, knocked-in an anti-tumor single chain variable fragment (scFv) into the N-terminus of CD3ε and efficiently generated fusion protein (FP) T cells. These cells displayed FP integration within the TCR/CD3 complex, lower variability in gene expression compared to CAR-T cells and good cell expansion after transfection. CD3ε FP T cells were predominantly CD8+ effector memory T cells, and exhibited anti-tumor activity in vitro and in vivo. Dual targeting FP T cells were also generated through the incorporation of scFvs into other CD3 subunits and CD28. Compared to viral-based methods, this method serves as an alternative and versatile way of generating T cells with tumor-targeting receptors for cancer immunotherapy.

'Off-the-Shelf' Immunotherapy: Manufacture of CD8+ T Cells Derived from Hematopoietic Stem Cells

Cellular immunotherapy is revolutionizing cancer treatment. However, autologous transplants are complex, costly, and limited by the number and quality of T cells that can be isolated from and expanded for re-infusion into each patient. This paper demonstrates a stromal support cell-free in vitro method for the differentiation of T cells from umbilical cord blood hematopoietic stem cells (HSCs). For each single HSC cell input, approximately 5 × 104 T cells were created with an initial five days of HSC expansion and subsequent T cell differentiation over 49 days. When the induced in vitro differentiated T cells were activated by cytokines and anti-CD3/CD28 beads, CD8+ T cell receptor (TCR) γδ+ T cells were preferentially generated and elicited cytotoxic function against ovarian cancer cells in vitro. This process of inducing de novo functional T cells offers a possible strategy to increase T cell yields, simplify manufacturing, and reduce costs with application potential for conversion into chimeric antigen receptor (CAR)-T cells for cancer immunotherapy and for allogeneic transplantation to restore immune competence.

Enhancing a Natural Killer: Modification of NK Cells for Cancer Immunotherapy

Natural killer (NK) cells are potent innate immune system effector lymphocytes armed with multiple mechanisms for killing cancer cells. Given the dynamic roles of NK cells in tumor surveillance, they are fast becoming a next-generation tool for adoptive immunotherapy. Many strategies are being employed to increase their number and improve their ability to overcome cancer resistance and the immunosuppressive tumor microenvironment. These include the use of cytokines and synthetic compounds to bolster propagation and killing capacity, targeting immune-function checkpoints, addition of chimeric antigen receptors (CARs) to provide cancer specificity and genetic ablation of inhibitory molecules. The next generation of NK cell products will ideally be readily available as an “off-the-shelf” product and stem cell derived to enable potentially unlimited supply. However, several considerations regarding NK cell source, genetic modification and scale up first need addressing. Understanding NK cell biology and interaction within specific tumor contexts will help identify necessary NK cell modifications and relevant choice of NK cell source. Further enhancement of manufacturing processes will allow for off-the-shelf NK cell immunotherapies to become key components of multifaceted therapeutic strategies for cancer.

Abstract 3023: The characterisation of hyaluronan-related enzymes in breast cancer cell subpopulations

Background:Hyaluronan (HA) has been associated with various facets of tumor biology where it provides structural integrity, maintains hydration homeostasis, and in conjunction with its metabolic receptor, CD44, has been implicated in tumor cell proliferation and migration. There is a direct correlation between treatment-resistant breast carcinomas and the increased synthesis of HA via the over-expression of the HA anabolic enzyme, HA synthase (HAS). It is becoming generally accepted that the failure of cancer treatments can be due to a small subpopulation of slow growing, invasive and drug resistant cells known as cancer stem cells (CSCs) which are often characterized by the presence of CD44. As CD44 is the sole HA metabolic receptor within the tumor microenvironment, this study aimed to characterize the role of HA metabolism in the breast CSC subpopulation and its potential contribution to the persistence of treatment-resistant cancer.

Methodology:HA metabolic enzymes [HAS 1-3 and hyaluronidase 1-2 (Hyal)] in breast cancer cell subpopulations were characterised in five cancer cell lines after FACS separation into putative CSC (CD44+/CD24-) and non-stem cell (CD44-/CD24+) subpopulations using quantitative real time PCR. Cell subpopulations were further characterised for cell-growth kinetics and resistance to chemotherapy using an Excelligence proliferation assay. The most highly expressed HAS isoform, HAS2, was knocked down or inserted in different cell lines using stable transfection and the resultant changes in proliferation, invasive and migratory potential and the direct effect on the CSC subpopulation was investigated both in vitro and in vivo.

Results:HAS2 and Hyal2 were determined to be preferentially expressed in invasive breast cancer cell lines, where the chemotherapy-resistant CSC subpopulations (CD44+/CD24-) expressed the highest level of these HAS and Hyal isoforms. Transfection-induced attenuation of HAS2 mediated a reduction in the CSC subpopulation while over-expression of HAS2 increased the size of the CD44+/CD24- subpopulation. Both in vitro and in vivo HAS 2 over-expression increased HA production with a concomitant increase in tumorigenesis and metastasis while the counter-effect was observed in HAS2 knock-down breast cancer cells.

Conclusions:These preliminary data suggest that HA metabolism is a tightly regulated process and a key component within breast cancer subpopulations and the CSC niche. The direct relationship between increased HAS expression, HA production and enlargement of the CD44+/CD24- subpopulation highlights HA metabolic enzymes as potential therapeutic targets in treatment-resistant breast cancer.

Citation Format: Vera Evtimov, Tracey Brown. The characterisation of hyaluronan-related enzymes in breast cancer cell subpopulations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3023. doi:10.1158/1538-7445.AM2014-3023