Down-Regulation of Toll-Like Receptor 5 (TLR5) Increased VEGFR Expression in Triple Negative Breast Cancer (TNBC) Based on Radionuclide Imaging

Abstract

In this study, GFP-tagged TNBC 4T1 cells with down-regulated TLR5 expression (TLR5− 4T1) and normal TLR5 expression (TLR5+ 4T1) were constructed, respectively. RT-PCR and Western blot studies showed that down-regulation of TLR5 obviously increased the expression of VEGFR in 4T1 cells. Highly stable radio-probes 125I-anti-TLR5 mAb/125I-VEGF/125I-IgG were obtained with labeling rates over 85% and radiochemical purities above 90%. Among these three probes, 125I−anti−TLR5 mAb and 125I-VEGF were used for specifically imaging TNBC, while 125I-IgG was used for comparison. Whole-body phosphorus autoradiography showed clear imaging at 48 h after injection of 125I-anti-TLR5 mAb and 125I-VEGF also provided clear imaging at 24 h. Biodistribution study demonstrated a higher tumor uptake of 125I-anti-TLR5 mAb in TLR5+ group compared with that in TLR5− group (P < 0.05), whereas tumor uptake of 125I-VEGF in TLR5+ group was lower than that in the TLR5− group (P < 0.05). Immunohistochemical staining suggested that the expression of TLR5 was lower, whereas the expression of VEGFR, CD31, and MVD (microvessel density) was higher in TLR5− tumor-bearing mice. In summary, the down-regulation of TLR5 in TNBC promoted the VEGFR expression and angiogenesis, resulting in the proliferation of TNBC cells. TLR5/VEGF might be a better indicator for monitoring the development of TNBC.

Toll‐like receptors in health and disease

“…Breast cancer ↑Tumor cell invasion through migration (epithelial-mesenchymal transition) [264][265][266] Colorectal cancer ↑Proinflammatory cytokines (TNF-α) 271 Gastric cancer ↑Tumor cell malignancy induction 275 Colitis ↑Proinflammatory cytokines 132,133 TLR7 Oral squamous cell carcinoma ↑Tumor cell cisplatin resistance 276 Colorectal cancer ↓Tumor cell apoptosis 286…”

“…263 Downregulation of TLR5 in TNBC promoted vascular endothelial growth factor receptor expression and angiogenesis, leading to the proliferation of TNBC cells through the TRAF6 and SOX2 pathways to increase tumor aggressiveness and EMT expression. [264][265][266] CRC patients exhibit increased TLR5 expression from normal mucosa to adenoma or adenocarcinoma. 267 Higher TLR5 expression in tumor tissue was linked to a better prognosis for patients with CRC.…”

“…TLR5 overexpression had a positive correlation with lymph node metastasis and a negative correlation with histological grade 263 . Downregulation of TLR5 in TNBC promoted vascular endothelial growth factor receptor expression and angiogenesis, leading to the proliferation of TNBC cells through the TRAF6 and SOX2 pathways to increase tumor aggressiveness and EMT expression 264–266 …”

“… 263 Downregulation of TLR5 in TNBC promoted vascular endothelial growth factor receptor expression and angiogenesis, leading to the proliferation of TNBC cells through the TRAF6 and SOX2 pathways to increase tumor aggressiveness and EMT expression. 264 , 265 , 266 …”

Toll-like receptor-targeted anti-tumor therapies: Advances and challenges

“…TLR5 can be activated by bacterial flagellin and plays a key role in the immune homeostasis of pathogen-host interactions ( 272 , 273 ). In addition, TLR5 is associated with decreased tumor cell proliferation, invasion, and metastasis ( 274 , 275 ). Several drugs targeting TLR5 are under investigation.…”