Streptavidin peroxidase immunohistochemical kit

NP tissues were fixed in 4% paraformaldehyde for 24 h, embedded in paraffin and cut serially at 5 μm for IHC staining. The IHC staining procedure was performed using a streptavidin-peroxidase immunohistochemical kit (Wuhan Boster Biological Technology, Ltd., Wuhan, China) according to the manufacturer's protocol. Briefly, the tissue sections were incubated with 0.125% trypsin for 30 min at 37°C for antigen retrieval and then incubated with primary rabbit monoclonal antibodies against SDF-1 (1:100; Abcam, Cambridge, UK) and CXCR4 (1:100; Abcam; cat. no. ab124824) overnight at 4°C to stain target protein expression, and immunoglobulin G (Wuhan Boster Biological Technology, Ltd) was used as a negative control. Finally, sections were incubated in 3–3′-diaminoben-zidine (Wuhan Boster Biological Technology, Ltd) to visualize immunoreactivity. Positively stained cells in three different areas were counted under a light microscope (Nikon TS100; Nikon Corporation, Tokyo, Japan).