Role for Putative Hepatocellular Carcinoma Stem Cell Subpopulations in Biological Response to Incomplete Thermal Ablation: In Vitro and In Vivo Pilot Study

Scott M. Thompson, Matthew R. Callstrom, Kim A. Butters, Shari L. Sutor, Bruce Knudsen, Joseph P. Grande, Lewis R. Roberts, David A. Woodrum

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Purpose: To investigate the potential role for CD44+ and CD90+ hepatocellular carcinoma (HCC) cellular subpopulations in biological response to thermal ablation-induced heat stress.

Methods: This study was approved by the institutional animal care committee. The N1S1 rat HCC cell line was subjected to sublethal heat stress (45 °C) or control (37 °C) for 10 min, costained with fluorescent-labeled antibodies against CD44, CD90, and 7-AAD after a 48-h recovery and analyzed by flow cytometry to assess the percentage of live CD44+ and CD90+ HCC cells (n = 4). Experiments were repeated with pretreatment of N1S1 cells with a dose titration of the dual PI3K-mTOR inhibitor BEZ235 or vehicle control (n = 3). Rats bearing orthotopic N1S1 tumors were subjected to ultrasound-guided partial laser ablation (n = 5) or sham ablation (n = 3), euthanized 24 h after ablation, and liver/tumor analyzed for immunohistochemical staining of CD44 and CD90. Differences between groups were compared with an unpaired t test.

Results: Sublethal heat stress induced a significant increase in the relative proportion of live CD44+ and CD90+ HCC cells compared to the control group: CD44+CD90 (5.3-fold; p = 0.0001), CD44CD90+ (2.4-fold; p = 0.003), and CD44+CD90+ (22.0-fold; p < 0.03). Inhibition of PI3K-mTOR prevented heat stress-induced enrichment of the population of live CD44+ HCC cells (p < 0.01), but not CD90+ cells (p > 0.10). Immunohistochemical analysis demonstrated preferential localization of clusters of CD44+ cells at both the tumor margin and ablation margin.

Conclusion: These studies provide experimental evidence supporting a role for HCC cells expressing the putative stem cell marker CD44 in HCC response to heat stress.

Original languageEnglish (US)
Pages (from-to)1343-1351
Number of pages9
JournalCardiovascular and Interventional Radiology
Volume37
Issue number5
DOIs
StatePublished - 2014

Keywords

  • CD44
  • Cancer stem cell
  • Hepatocellular carcinoma
  • Thermal ablation

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Cardiology and Cardiovascular Medicine

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