The spread of cancer cells from a primary tumors to secondary sites within the
body, known as metastasis, is the leading cause of cancer-related death. Animal
models have proven to be an invaluable resource for studying the complex
interactions between cancer cells and the tumour microenvironment during the
metastatic cascade. The zebrafish (Danio rerio) has emerged as a potent
vertebrate model for studying in vivo metastatic events. ws for embryonic
manipulation, and optically transparent tissues, which allow for real-time
imaging of fluorescently labelled cells.
Metastasis is a multifaceted process that involves multiple genetic, epigenetic,
biochemical, and physical changes in cancer cells and their surrounding
microenvironments. Although metastasis is responsible for the majority of
cancer-related deaths, new evidence suggests that the majority of metastasis is
caused by circulating tumour cell (CTC) clusters rather than individual tumour
cells. These CTC clusters have a greater ability to: 1) spread throughout the
body, 2) withstand hemodynamic forces in the bloodstream, and 3) proliferate
once they extravasate at distant sites.
Furthermore, studies have revealed that cell clusters exit circulation via
angiopellosis, a recently discovered extravasation mechanism in which blood
vessels actively remodel, allowing the clusters to exit while retaining their
multicellularity. Maintaining this multicellularity has been shown to provide
distinct survival and proliferative benefits, and it has previously been proposed
that CTC clusters may be responsible for the majority of cancer metastasis. this
system to create a model to better identify and understand the molecular drivers
of extravasation in metastatic osteosarcoma. Osteosarcoma (OS) is a rare but
deadly primary bone cancer that primarily affects children and young adults. It
is the most common primary bone cancer, and the 5-year survival rate for
patients with metastatic disease is only 30%.To test the hypothesis that CTC
clusters would exhibit unique molecular profiles associated with their ability to
migrate to distant sites and extravasate, researchers used a zebrafish model of
metastasis to infuse fluorescent canine OS cells into Tg zebrafish with
fluorescent blood vessels. The vasculature of zebrafish has previously been
shown to be a suitable model system for understanding the vascular
environments of mammals, including humans. The development of this model
can be used to identify and study additional targets or markers involved in the
extravasation process. More research is needed to determine whether other noncancerous cells use a similar gene dysregulation during angiopellosis.
CTCs extravasating as clusters were observed using intravital imaging. RNASeq was used to isolate, expand, and characterise these clusters. These efforts
identified several key pathways that are commonly enriched in human and
canine OS extravasated clusters, including KRAS signalling downregulation,
interferon gamma response and other immune pathways, and extracellular
matrix remodelling. CTCs’ ability to survive in circulation, extravasate at distant
sites, and form new tumours is extremely rare; however, when these events
occur, they frequently represent the precursors to a deadly disease. CTCs must
endure harsh conditions during dissemination, such as novel
microenvironments, exposure to different cell types and signals, immune
targeting, anchorage-independent growth, and shear force from circulation.
According to research, when CTCs form clusters, their ability to survive the
metastatic process and seed distant sites increases significantly. Some argue that
these clusters, rather than individual CTCs, cause the majority of cancer
metastases. The mechanisms by which these CTC clusters extravasate are still
being studied.
Melanoma and cervical CTC clusters, have been observed to extravasate out of
blood vessels via angiopellosis, a process in which endothelial cells remodel the
vessel architecture around the CTC clusters. CTC clusters are able to maintain
their multicellular phenotype as a result of this. The development of relevant
models to identify and investigate specific problems.Extravasation markers are
scarce, but this zebrafish model serves as a one-of-a-kind way to capitalise on
one’s ability to perform. To investigate this, intravital imaging and subsequent
cell isolation were used more thorough procedure. The ability of tumour cells
from various species and cancer types to undergo angiopellosis suggests that
this extravasation mechanism may be a common feature of CTC clusters. Prior
research has shown that non-tumor cells and cell membranecoated
microparticles can undergo angiopellosis, implying that this phenomenon is not
unique to CTCs but may be used by CTCs during the metastasis process. data
have identified potential molecular drivers of extravasation, such as
downregulation of proliferative signals (e.g., KRAS signalling), immune
evasion, and versican-mediated ECM dysregulation during metastasis.
Angiopellosis, like cancer-mediated necrosis of endothelial cells and
transmigratory cup formation in neutrophil extravasation, may be a
physiological mechanism hijacked by specific types of cancer cells, allowing
for extravasation. More research is needed to determine whether other noncancerous cells use a similar gene dysregulation during angiopellosis.
establishes the zebrafish intravital imaging model as a means of further
investigating the specific steps of the extravasation process, as well as identifies
key pathway alterations that may drive extravasation during metastasis.
These pathways could be novel therapeutic targets for preventing CTC cluster
formation, migration, and metastatic potential. Together, these findings 1)
establish a useful model to provide key insights into the biology of CTCs,
extravasation, and metastasis, and 2) highlight an important link between
phenotypic features of CTCs, such as their ability to extravasate as multicellular
clusters, and unique molecular features that may lead to metastasis .