Activation of STAT3/HIF-1α/Hes-1 axis promotes trastuzumab resistance in HER2-overexpressing breast cancer cells via down-regulation of PTEN

• Published in: Biochimica et biophysica acta. General subjects Vol. 1861; no. 8; pp. 1970 - 1980
• Main Authors: Aghazadeh, Safiyeh, Yazdanparast, Razieh
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2017
• Subjects: antibodies; Antineoplastic Agents - pharmacology; apoptosis; biomarkers; breast neoplasms; Breast Neoplasms - chemistry; Breast Neoplasms - drug therapy; Cell Line, Tumor; cell viability; chemosensitization; Down-Regulation; Drug Resistance, Neoplasm; Female; gene expression regulation; HIF-1α; Humans; hypoxia-inducible factor 1; Hypoxia-Inducible Factor 1, alpha Subunit - physiology; neoplasm cells; precipitin tests; PTEN; PTEN Phosphohydrolase - physiology; Receptor, ErbB-2 - analysis; small interfering RNA; STAT3; STAT3 Transcription Factor - physiology; Transcription Factor HES-1 - physiology; transfection; Trastuzumab - pharmacology; Trastuzumab resistance; Western blotting; PTEN; Trastuzumab resistance; HIF-1α; STAT3
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2017.05.009

Resistance to the HER2-targeted antibody trastuzumab remains to be a major clinical challenge in the treatment of HER2-positive breast cancer. Hyper-activation of STAT3 is proposed to be a predictive biomarker of trastuzumab resistance. However, the precise mechanism(s) remains poorly defined. Evidence is emerging that HIF-1α, a central downstream element of STAT3 pathway, serves a pivotal role in the complex signaling network with subsequent diverse cellular events. We have established trastuzumab resistant SKBR3 cells (SKBR3-TR). The cell viability, apoptosis as well as western blot, siRNA transfection and co-immunoprecipitation assays were performed to evaluate the involvement of STAT3/HIF-1α in modulation of trastuzumab resistance. We found that in SKBR3-TR cells and conditioned medium-treated parental cells, constitutive phosphorylated STAT3 coincided with prominent up-regulation of HIF-1α which was accompanied with PTEN attenuation. Moreover, the inhibition of STAT3 activation by Stattic and/or genetically STAT3 knocking down decreased HIF-1α level in SKBR3-TR cells. Additionally, treatment with Stattic and/or STAT3 siRNA engendered the up-regulation of PTEN protein in STAT3-inhibited resistant cells. Restoration of PTEN was also observed following siRNA-mediated silencing of HIF-1α expression. Moreover, down-regulation of HIF-1α caused a reduction in the HES-1 content. Further study with HES-1 specific siRNA revealed the elevation of PTEN expression in HES-1 knock-down trastuzumab resistant cells. The impairment of STAT3-HIF-1α-HES-1 pathway restored trastuzumab sensitivity through up-regulation of PTEN protein. These findings highlighted the signal integrator role of HIF-1α in STAT3-mediated trastuzumab resistance induction which would be valuable in designing more efficient chemosensitization strategies. [Display omitted] •Trastuzumab resistant cells exhibit a high level of active STAT3 and subsequent HIF-1α expression.•Inhibition of STAT3 enhanced PTEN expression in trastuzumab resistant cells.•HIF-1α is a co-operator of STAT3 in trastuzumab resistance development