Novel immunologic tolerance of human cancer cell xenotransplants in zebrafish

Abstract

Immune deficiency or suppression in host animals is an essential precondition for the success of cancer cell xenotransplantation because the host immune system has a tendency to reject implanted cells. However, in such animals, the typical tumor microenvironment seen in cancer subjects does not form because of the lack of normal immunity. Here, we developed a novel zebrafish (Danio rerio) model based on 2 rounds of cancer cell xenotransplantation that achieved cancer-specific immunologic tolerance without immunosuppression. We irradiated human cancer cells (PC-3, K562 and HepG2) to abolish their proliferative abilities and implanted them into zebrafish larvae. These cells survived for 2 weeks in the developing host. Three months after the first implantation, the zebrafish were implanted with the same, but nonirradiated, cell lines. These cancer cells proliferated and exhibited metastasis without immune suppression. To reveal the transcriptional mechanism of this immune tolerance, we conducted dual RNA-seq of the tumor with its surrounding tissues and identified several regulatory zebrafish genes that are involved in immunity; the expression of plasminogen activator, urokinase, and forkhead box P3 was altered in response to immunologic tolerance. In conclusion, this xenograft method has potential as a platform for zebrafish-based anticancer drug discovery because it can closely mimic human clinical cancers without inducing immune suppression.

Zebrafish xenograft models of cancer and metastasis for drug discovery

“…Although transplantation of cancer cells has been successfully applied in zebrafish at later stages of development (such as juvenile or adult fish), this is technically challenging especially to image. Published studies have applied this to approach to studying the behaviour of human leukemia, prostate, liver [39,40], breast cancer, fibrosarcoma and melanoma cells [41,42]. An interesting hybrid approach has been applied successfully by inducing melanoma in zebrafish, which are then cultured and re-injected into both adults and embryos.…”

“…In addition, the growing interest in immune-targeted anti-cancer treatments highlights the importance of using immunocompetent models for cancer research. A novel xenotransplantation model has been developed to circumvent these issues in the adult zebrafish through sequential injection of irradiated then viable tumour cells to induce immune tolerance [39]. This results in an adaptation of the immune system allowing tumour growth and metastasis.…”

Zebrafish: Speeding Up the Cancer Drug Discovery Process

“…Zhang and colleagues developed a novel tumor cell transplantation strategy without immunosuppression requirement. This method consists of transplanting irradiated human tumor cells into a zebrafish embryo and retransplanting nonirradiated cells into the same zebrafish 3 months later (42).…”

Zebrafish Xenograft: An Evolutionary Experiment in Tumour Biology

“…The communication between cancer cells and the host of origin's immune system builds over the lifespan of the tumour. A novel alternative being developed in zebrafish is to preseed the host with irradiated cancer cells in order to promote immune tolerance early in development, then doing grafts later in the host's life, where the cancer cells will not immediately raise a humoral immune response [96]. Zebrafish are an ideal model for this work, as they can easily be injected during embryonic stages before the humoral immune system has full developed, and pigment-free strains allow easy imaging [97,98].…”