Measuring kinetics and metastatic propensity of CTCs by blood exchange between mice

Bashar Hamza,Emily M King,Kelsey L Degouveia,Robert A Weinberg,Sheng Rong Ng,William A Freed-Pastor,Max A Stockslager ,Christina L Bray ,Grissel C Jaramillo,M Burger ,Nolawit Mulugeta,Christopher R Chin,Lara Meier,Tyler Jacks,Haley Strouf,F Candela Rodriguez ,Arnold Miller ,Alex K Shalek,Nicholas L Calistri,Lin Lin,Scott R Manalis

doi:10.1038/s41467-021-25917-5

Abstract

Existing preclinical methods for acquiring dissemination kinetics of rare circulating tumor cells (CTCs) en route to forming metastases have not been capable of providing a direct measure of CTC intravasation rate and subsequent half-life in the circulation. Here, we demonstrate an approach for measuring endogenous CTC kinetics by continuously exchanging CTC-containing blood over several hours between un-anesthetized, tumor-bearing mice and healthy, tumor-free counterparts. By tracking CTC transfer rates, we extrapolated half-life times in the circulation of between 40 and 260 s and intravasation rates between 60 and 107,000 CTCs/hour in mouse models of small-cell lung cancer (SCLC), pancreatic ductal adenocarcinoma (PDAC), and non-small cell lung cancer (NSCLC). Additionally, direct transfer of only 1−2% of daily-shed CTCs using our blood-exchange technique from late-stage, SCLC-bearing mice generated macrometastases in healthy recipient mice. We envision that our technique will help further elucidate the role of CTCs and the rate-limiting steps in metastasis.

Highlights

Existing preclinical methods for acquiring dissemination kinetics of rare circulating tumor cells (CTCs) en route to forming metastases have not been capable of providing a direct measure of CTC intravasation rate and subsequent half-life in the circulation
We apply our method to an autochthonous, genetically engineered mouse model (GEMM) of small-cell lung cancer (SCLC), which is characterized by high CTC levels in the blood, in addition to a GEMM of non-small-cell lung cancer (NSCLC) and various models of pancreatic ductal adenocarcinoma (PDAC), which are characterized by significantly lower CTC levels
SCLC tumor-bearing mouse (TBM) survive for approximately six months post tumor initiation, with detectable primary and metastatic tumors starting at approximately five months post tumor initiation

Summary

Introduction

Existing preclinical methods for acquiring dissemination kinetics of rare circulating tumor cells (CTCs) en route to forming metastases have not been capable of providing a direct measure of CTC intravasation rate and subsequent half-life in the circulation. Circulating tumor cells (CTCs)—cells shed into the bloodstream from primary and metastatic tumor deposits— represent the intermediary component of the metastatic cascade Measuring their intravasation rate and half-life time in the circulatory system, which together govern their blood levels, has been an important step towards elucidating the kinetics of their seeding of distant tissues and the subsequent outgrowth of metastatic colonies. The intravenously injected cells seemed to arrest in the capillaries of the first organs they encountered almost immediately after injection, but their subsequent proliferation into secondary lesions was influenced by host-tumor cell interactions operating within specific organs These studies established the basis of the “seed and soil” hypothesis[6,7,8], these methods have not been amenable to the study of endogenouslygenerated CTCs that originate from solid primary tumors, which would be expected to exhibit different physiology than CTCs derived from established cell lines. The blood-exchange method we describe here enables a series of experiments that can answer fundamental questions about the relationship between CTC characteristics and metastasis

Methods

Results

Conclusion