Metastasis accounts for the majority of all cancer deaths, yet the process remains poorly understood. A pivotal step in the metastasis process is the exiting of tumor cells from the circulation, a process known as extravasation. However, it is unclear how tumor cells extravasate and whether multicellular clusters of tumor cells possess the ability to exit as a whole or must first disassociate. In this study, we use in vivo zebrafish and mouse models to elucidate the mechanism tumor cells use to extravasate. We found that circulating tumor cells exit the circulation using the recently identified extravasation mechanism, angiopellosis, and do so as both clusters and individual cells. We further show that when melanoma and cervical cancer cells utilize this extravasation method to exit as clusters, they exhibit an increased ability to form tumors at distant sites through the expression of unique genetic profiles. Collectively, we present a new model for tumor cell extravasation of both individual and multicellular circulating tumor cells. This article has an associated First Person interview with the first author of the paper.
Introduction Accumulating data suggests metastatic primary tumor cells can travel through the circulation and form secondary tumors as multicellular clusters. However, whether these clusters must first dissociate into single cells prior to exiting of blood vessels remains largely unknown. Of late, researchers have identified a mechanism of cell extravasation (exiting blood vessel), termed angiopellosis (Allen 2016). However, whether tumor cell clusters possess the ability to exit vessles using the angiopellosis method is unstudied. We hypothesized that circulating tumor cell (CTC) clusters could exit blood vessels while maintaining a multicellular phenotype, through angiopellosis. Methodology To test this, we used an in vivo zebrafish larvae model using the tg(fli1a:egfp) line, in which blood vessels exclusively fluoresce. First, we infused fluorescent human melanoma (A375), mouse melanoma (B16F10), and human cervical (HeLa) cells into the circulation of the larvae. Next, we used lightsheet microscopy to observe the method the tumor cells used to exit blood vessels. Additionally, mouse melanoma (B16F10) cells were intravenously infused into the circulation of C57BL/6J mice as either tumor clusters or individual cells. The mice were imaged for metastatic lung foci, to determine cluster extravasation potential. Experimental results The intravital lightsheet microscopy allowed us to determine that tumor cells can utilize angiopellosis to exit blood vessels in the zebrafish model, both as individual CTCs and CTC clusters. Extravasating CTCs exited blood vessels through angiopellosis at 94%, with only 6% exiting through the diapedesis method (n=30). CTCs which exited as a cluster through angiopellosis were observed to form tumor masses at an 88% higher rate compared to individual tumor cells in vivo, over the course of 96 hours. In the murine model, CTCs clusters which were infused via tail vein (n=4) showed significantly higher metastatic lung foci in comparison to individual CTCs that were infused (n=3). Following isolation and analysis of metastatic CTCs, multiple genes were shown to be differentially expressed in CTC clusters in both the zebrafish and murine models. Discussion Here, we show circulating tumor cell clusters possess the ability to exit blood vessels through the recently identified angiopellosis. We determined tumor cell clusters exhibit an augmented ability to proliferate in vivo, while individually tumor cells are more prone to dormancy. Our results challenge the belief that circulating tumor cell clusters must first disassociate to exit the circulation, and posits an alternative model. We propose tumor cells both travel and exit the circulation while maintaining a multicellular phenotype, using angiopellosis, stimulating proliferation-augmenting genetic/molecular alterations. This has been termed the Cancer Exodus Hypothesis. Citation Format: Tyler Allen, Emmanuel Amu, Dana Asad, Ke Cheng. Metastatic melanoma and cervical tumor cell clusters can exit blood vessels through angiopellosis augmenting tumor formation ability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 90.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.