Examining the relationship between Cu-ATSM hypoxia selectivity and fatty acid synthase expression in human prostate cancer cell lines☆

Abstract 

Introduction

Positron emission tomography (PET) imaging with copper (II)-diacetyl-bis(N⁴-Methylthiosemicarbazone)(Cu-ATSM) for delineating hypoxia has provided valuable clinical information, but investigations in animal models of prostate cancer have shown some inconsistencies. As a defense mechanism in prostate cancer cells, the fatty acid synthesis pathway harnesses its oxidizing power for improving the redox balance despite conditions of extreme hypoxia, potentially altering Cu-ATSM hypoxia selectivity.

Methods

Human prostate tumor-cultured cell lines (PC-3, 22Rv1, LNCaP and LAPC-4), were treated with a fatty acid synthase (FAS) inhibitor (C75, 100 μM) under anoxia. The ⁶⁴Cu-ATSM uptake in these treated cells and nontreated anoxic cells was then examined. Fatty acid synthase expression level in each cell line was subsequently quantified by ELISA. An additional study was performed in PC-3 cells to examine the relationship between the restoration of ⁶⁴Cu-ATSM hypoxia selectivity and the concentration of C75 (100, 20, 4 or 0.8 μM) administered to the cells.

Results

Inhibition of fatty acid synthesis with C75 resulted in a significant increase in ⁶⁴Cu-ATSM retention in prostate tumor cells in vitro under anoxia over 60 min. Inhibition studies demonstrated higher uptake values of 20.9±3.27%, 103.0±32.6%, 144.2±32.3% and 200.1±79.3% at 15 min over control values for LAPC-4, PC-3, LNCaP and 22Rv1 cells, respectively. A correlation was seen (R²=.911) with FAS expression plotted against percentage change in ⁶⁴Cu-ATSM uptake with C75 treatment.

Conclusions

Although Cu-ATSM has clinical relevance in the PET imaging of hypoxia in many tumor types, its translation to the imaging of prostate cancer may be limited by the overexpression of FAS associated with prostatic malignancies.

Keywords: Fatty acid synthase, Cu-ATSM, PET, Prostate cancer