Zebrafish (Danio rerio) have emerged as an important vertebrate model due to
their high genetic homology to humans and the transparency of their embryos,
and they are increasingly being applied to the study of developmental processes,
microbehost interactions, human diseases, drug screening, and so on. The
zebrafish cancer metastasis models developed may give an alternative to the
limitations of rodent models.
In the clinic, overt cancer metastasis is comprised of a sequence of complicated
and multi-step processes known as the “metastatic cascade.” The cascade has
been thoroughly studied and may be broken down into the following steps: local
invasion, intravasation, dispersion, arrest, extravasation, and colonization.
Robust host models of cancer cell spread are required for a better understanding
of the pathophysiology of cancer metastasis and the development of possible in
vivo therapeutic methods. Rodent models are well established and frequently
used to evaluate metastasis, however they have low efficiency, ethical
restrictions, and are expensive as a front-line model to test if a particular
treatment may influence the metastatic phenotype. Other efficient, dependable,
and low-cost models are required to rapidly assess the possible impacts of
(epi)genetic alterations or pharmacological substances. Zebrafish (Daniorerio)
have emerged as an important vertebrate model due to their high genetic
homology to humans and the transparency of their embryos, and they are
increasingly being applied to the study of developmental processes, microbehost
interactions, human diseases, drug screening, and so on.
Although spontaneous neoplasia is uncommon in wild zebrafish, there are
numerous long-established methods for inducing the desired malignancy in
zebrafish. Carcinogen-induced gene mutations or signalling pathway activation
can histologically and molecularly simulate carcinogenesis in zebrafish
resembling human disease. (Transgenic) zebrafish have also permitted
prospective investigations of cancer genesis and maintenance by taking use of
different forward and reverse genetic alterations of oncogenes or tumour
suppressors. Induced cancer models in zebrafish include digestive, reproductive,
blood, nervous system, and epithelial cancers. The use of zebrafish in cancer
research has lately increased due to the development of human tumour cell
xenograft models in this creature. This was originally described in 200511, with
human metastatic melanoma cells effectively engrafted in zebrafish embryos at
the blastula stage. Several independent laboratories have verified the viability of
this ground-breaking study by implanting a wide variety of human cancer cell
lines into zebrafish at various locations and developmental stages5. Injections
near the blastodisc and blastocyst of the blastula stage, for example; injections
into the yolk sac, Injections into the peritoneal cavity of 30-day-old
immunosuppressed larvae have been conducted, as well as injections into the
perivitelline space, duct of Cuvier (Doc), and posterior cardinal vein of 6-h- to
5-day-old embryos. Allogeneic tumour transplantations in zebrafish have also
been described. One of the most significant benefits of utilising xenografts is
that the engrafted cancer cells may be readily fluorescently tagged and
differentiated from normal cells. As a result, research into the dynamic
behaviours of microtumor forms, cell invasion and metastasis, tumor-induced
angiogenesis, and interactions between cancer cells and host factors may be
vividly observed in the live fish body.
The feasibility of xenograft models using human breast cancer cells injected
into zebrafish embryos. Under the microscope, fluorescent proteins or
chemically labelled human breast cancer cells are implanted into transgenic
zebrafish embryos, Tg (fli:EGFP), 48 hours after fertilisation, in the
perivitelline space or duct of Cuvier (Doc).Soon after, the temporal-spatial
process of cancer cell invasion began. A fluorescent microscope is used to
observe the spread and metastasis of cancer in the body of a living fish. The
models employing various injection locations, such as perivitelline space or
Doc, are complimentary, illustrating the early (intravasation step) and late
(extravasation step) stages of the multistep metastatic cascade of events.
Furthermore, peritumoral and intratumoral angiogenesis can be seen with
injections into the perivitelline region. The duration of the trial is no more than 8
days.These two models combine cell labelling, micro-transplantation, and
fluorescence imaging methods to allow for fast assessment of cancer spread in
response to genetic and pharmacological changes.
It has also been seen that inhibiting the TGF- pathway via various techniques –
and at various stages of the system – resulted in a significant decrease in breast
cancer cell invasion and metastasis Only breast cancer cells with metastatic
potential showed invasion and micrometastasis. Interestingly,that M2 and M4
cells produced clusters of invasive cells primarily in the CHT area, where they
may proliferate. TGF- (transforming growth factor beta) signalling is known to
influence human breast cancer invasion and metastasis. T.hat the zebrafish
xenograft test is a reliable animal model for studying the impact of
pharmacological modulators and genetic alterations in TGF- signalling in breast
cancer cells from humans, TGF- (transforming growth factor beta) signalling is
known to influence human breast cancer invasion and metastasis. that the
zebrafish xenograft test is a reliable animal model for studying the impact of
pharmacological modulators and genetic alterations in TGF- signalling in breast
cancer cells from humans. According to in vitro and in vivo mice investigations,
breast cancer cells with varying levels of malignancy exhibited invasive and
metastatic characteristics within the embryonic zebrafish model, which well
matched with their differential tumorigenicity in mouse models. Interestingly,
MCF10A M2 and M4 cells invaded the caudal hematopoietic tissue and
appeared as a cluster of cells, whereas MDA MB 231 cells infiltrated the tail fin
and appeared as individual cells. The zebrafish-embryonic breast cancer
xenograft model may be used for mechanistic understanding, screening, and
development of anti-TGF- medicines for the treatment of metastatic breast
cancer in a timely and cost-effective way.