Evaluation of STAT3 signaling in ALDH+ and ALDH+/CD44+/CD24- subpopulations of breast cancer cells

• Published in: PloS one 2013-12, Vol.8 (12), p.e82821-e82821
• Main Authors: Lin, Li, Hutzen, Brian, Lee, Hsiu-Fang, Peng, Zhengang, Wang, Wenlong, Zhao, Chongqiang, Lin, Huey-Jen, Sun, Duxin, Li, Pui-Kai, Li, Chenglong, Korkaya, Hasan, Wicha, Max S, Lin, Jiayuh
• Format: Article
• Language: English
• Subjects: Activation; Animal models; Animals; Anthraquinones - pharmacology; Apoptosis; Apoptosis - drug effects; Breast cancer; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cancer; Cancer cells; Cancer therapies; Cancer treatment; Cardiology; CD24 Antigen - metabolism; CD44 antigen; Cell Line, Tumor; Cell proliferation; Cell Proliferation - drug effects; Cell Separation; Cell surface; Cell Survival - drug effects; Chemotherapy; Comparative analysis; Cyclic S-Oxides - pharmacology; Developmental biology; Diagnosis; Female; Fibroblasts; Flow Cytometry; Gene expression; Humans; Hyaluronan Receptors - metabolism; Inhibition; Internal medicine; Isoenzymes - metabolism; Medical prognosis; Medical technology; Medicine; Metastasis; Mice, SCID; Pediatrics; Pharmaceutical sciences; Pharmacology; Pharmacy; Phosphorylation; Retinal Dehydrogenase - metabolism; RNA, Small Interfering - metabolism; Signal Transduction - drug effects; Signaling; Small Molecule Libraries - pharmacology; Stat3 protein; STAT3 Transcription Factor - metabolism; Stem cells; Subpopulations; Sulfonamides - pharmacology; Tissues; Tumors; Xenograft Model Antitumor Assays; Xenografts
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0082821

STAT3 activation is frequently detected in breast cancer and this pathway has emerged as an attractive molecular target for cancer treatment. Recent experimental evidence suggests ALDH-positive (ALDH(+)), or cell surface molecule CD44-positive (CD44(+)) but CD24-negative (CD24(-)) breast cancer cells have cancer stem cell properties. However, the role of STAT3 signaling in ALDH(+) and ALDH(+)/CD44(+)/CD24(-) subpopulations of breast cancer cells is unknown. We examined STAT3 activation in ALDH(+) and ALDH(+)/CD44(+)/CD24(-) subpopulations of breast cancer cells by sorting with flow cytometer. We observed ALDH-positive (ALDH(+)) cells expressed higher levels of phosphorylated STAT3 compared to ALDH-negative (ALDH(-)) cells. There was a significant correlation between the nuclear staining of phosphorylated STAT3 and the expression of ALDH1 in breast cancer tissues. These results suggest that STAT3 is activated in ALDH(+) subpopulations of breast cancer cells. STAT3 inhibitors Stattic and LLL12 inhibited STAT3 phosphorylation, reduced the ALDH(+) subpopulation, inhibited breast cancer stem-like cell viability, and retarded tumorisphere-forming capacity in vitro. Similar inhibition of STAT3 phosphorylation, and breast cancer stem cell viability were observed using STAT3 ShRNA. In addition, LLL12 inhibited STAT3 downstream target gene expression and induced apoptosis in ALDH(+) subpopulations of breast cancer cells. Furthermore, LLL12 inhibited STAT3 phosphorylation and tumor cell proliferation, induced apoptosis, and suppressed tumor growth in xenograft and mammary fat pad mouse models from ALDH(+) breast cancer cells. Similar in vitro and tumor growth in vivo results were obtained when ALDH(+) cells were further selected for the stem cell markers CD44(+) and CD24(-). These studies demonstrate an important role for STAT3 signaling in ALDH(+) and ALDH(+)/CD44(+)/CD24(-) subpopulations of breast cancer cells which may have cancer stem cell properties and suggest that pharmacologic inhibition of STAT3 represents an effective strategy to selectively target the cancer stem cell-like subpopulation.