TITLE:
Detection of Estrogen Responsive Breast Cancer Circulating Tumor Cells: Assay Development for Anti-Hormone Therapy Resistance
AUTHORS:
Sally A. Litherland, Louis Barr, Robert Reynolds, Elizabeth Griffith, Ryan Sause, Tiffany Encarnacion, Alvin J. O. Almodovar, Xiang Zhu, Stephanie Dickstein, Yai-Ping Shao, Na’im Fanaian, David A. Decker
KEYWORDS:
Epigenetics, Breast Cancer, Estrogen Receptor, Histone Acetylation, Anti-Hormone Therapy
JOURNAL NAME:
Journal of Cancer Therapy,
Vol.6 No.9,
August
24,
2015
ABSTRACT: Recent clinical trials with histone deacetylase inhibitors (HDACi) have
shown increased progression free survival by re-sensitizing resistant estrogen
receptor positive (ER+) breast cancer cells to hormone suppressive therapies
(HT). However, these trials lacked a sensitive, specific assay to identify and
monitor HDACi/HT sensitive or resistant tumors. We tested detection of ER expression
and histone acetylation of chromatin at the growth regulation by estrogen in
breast cancer 1 (GREB1) gene, an estrogen-responsive gene involved in ER expression, in
circulating tumor cell (CTC) as potential candidate assays for HDACi/HT
sensitivity. ER+ and ER- CTC were detected and isolated from breast cancer
patient peripheral blood by high speed fluorescence activated cell sorting
(FACS) for use in mRNA analysis and anti-acetylated histone-mediated Chromatin
Immunoprecipitation (ChIP). cDNA from mRNA and DNA extracted from the ChIP
isolates were quantified by real-time PCR for GREB1. CTC isolates from
patients who had an ER+ breast cancer primary contained both ER+ and ER- cells.
More ER+ than ER- CTC was found in HT sensitive patients compared to HT
resistant patients (p = 0.0559). GREB1 was found in acetylated histone
chromatin from both ER+ and ER- CTC. The number of ER+ and ER- CTC found in
peripheral blood appears to parallel patient outcomes as to their sensitivity
to HT. Acetylated histone analysis can detect chromatin containing GREB1 in CTC, suggesting it may be
useful as a more specific measure of HDACi effects on breast tumor cells. A larger, longitudinal data set
following patients through HT/HDACi trials is needed to confirm these
observations and their development for clinical use.