2023 FDA Science Forum
A Model to Test and Understand Cancer Cells that are Circulating in the Body
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Contributing OfficeCenter for Drug Evaluation and Research
Abstract
Circulating cancer stem cells (cCSCs) are a subset of circulating tumor cells (CTCs) that are released from primary tumors into the bloodstream, allowing them to spread to other parts of the body and evade the body's immune system. CTCs and cCSCs have the potential to be used as a non-invasive liquid biopsy to monitor a patient's disease progression or response to treatment but isolating and characterizing this rare and heterogenous population within the blood is difficult.
In this study, we have created an in vitro model of breast cancer CTCs. We cultured breast cancer cell lines in a non-adherent suspension condition to mimic the circulation of blood and a monolayer to mimic the primary tumor. We then used flow cytometry and immunoblotting to identify cell lines with upregulated cancer stem cell surface markers following suspension condition. We analyzed gene expression in the suspension-induced CSC cell lines and found changes in cell metabolism, reduced adhesion-related gene expression, and stimulated hypoxia-regulated genes. We also found that the hypoxia-regulated gene carbonic anhydrase IX (CAIX) was upregulated in a panel of suspension cultured cell lines and correlated with cells that expressed CD44, a known CSC marker. When we inhibited CAIX activity, we noted a decrease in the population of CSCs within the suspension cultured cells. Since CAIX is only expressed in highly hypoxic conditions, it may be a potential target for isolating cCSCs and furthering their use as a surrogate biomarker for monitoring treatment responses.
