Tetramethylpyrazine downregulates transcription of the CXC receptor 4 (CXCR4) via nuclear respiratory factor‑1 (Nrf‑1) in WERI‑Rb1 retinoblastoma cells.

Tetramethylpyrazine (TMP; an extract of the Chinese herbal medicine, Chuanxiong) has been shown to exert remarkable antiretinoblastoma (RB) effects. Based on our previous study, the target gene was found to be C‑X‑C chemokine receptor type 4 (CXCR4). CXCR4 is a prognostic marker in various types of cancer, but the exact mechanisms underlying the regulation of CXCR4 expression by TMP in WERI‑Rb1 cells have yet to be fully elucidated. In the present study, it was revealed that TMP significantly downregulated CXCR4 expression and inhibited CXCR4 promoter activity in WERI‑Rb1 cells, indicating that TMP inhibits CXCR4 expression in WERI‑Rb1 cells through transcriptional regulatory mechanisms. Among the numerous transcription factors involved in CXCR4 function, including Yin Yang 1 (YY1), nuclear respiratory factor‑1 (Nrf‑1), Krüppel‑like Factor 2 (KLF2), specificity protein 1 (SP1), and nuclear factor‑κB subunit 1 (NF‑κB1), only TMP led to a significant downregulation of Nrf‑1 expression. Chromatin immunoprecipitation assays further indicated that Nrf‑1 directly binds to the promoter region of CXCR4, and silencing Nrf‑1 via siRNA transfection notably inhibited CXCR4 expression in WERI‑Rb1 cells. In addition, the expression levels of both Nrf‑1 and CXCR4 increased concomitantly with WERI‑Rb1 cell density. Furthermore, the downregulation of Nrf‑1 and CXCR4 expression in RB by TMP was confirmed in vivo. Taken together, the results of the present study have uncovered a novel mechanism in which CXCR4 expression is regulated by Nrf‑1 in WERI‑Rb1 cells, thereby identifying novel potential targets for the treatment of RB, and providing evidence for the clinical application of TMP in adjuvant retinoblastoma therapy.