Abstract: Abstract: Objective To analyze the regulation of estrogen receptor α (ERα) on truncated neurokinin- 1 receptor (NK1R-Tr), and the influence of this regulation on cell proliferation in estrogen receptor-positive breast cancer cell lines. Methods The chromatin immune coprecipitation (CHIP) was used to observe the transcriptional regulation function of ERα on NK1R- Tr in breast cancer cells. Luciferase reporter gene assay was used to verify whether ERα played a positive regulatory role in the expression of NK1R-Tr. Western blot assay and real-time-PCR were used to detect the expression of ERα and NK1R-Tr in breast cancer cells, MCF-7 and T47D, as well as the expression of NK1R-Tr protein and mRNA level. NK1R- Tr levels were also detected after using estradiol (E2, ERα agonist) and small interfering RNA (knock out ERα). CCK- 8 and clone formation experimen were used to detect the proliferation ability of breast cancer cells after knocking out NK1R-Tr with small interfering RNAs. Results CHIP test and Luciferase reporter gene assay proved that ERα can positively regulate the expression of NK1R- Tr via the ERα sequences in the upstream of the NK1R- Tr gene promoter. The expression of NK1R-Tr at both protein level and mRNA level dropped in the estrogen receptor-positive breast cancer cell line MCF-7 upon knocking out ERα. After knocking out NK1R-Tr, the proliferation ability of estrogen receptor- positive breast cancer cells was lower than that of the control group. Conclusion The ERα positively regulates the expression of NK1R-Tr, resulting in the increased cell proliferation in estrogen positive breast cancer cells.

Key words: breast neoplasms, cell line, tumor, estrogen receptor alpha, receptors, neurokinin- 1, RNA, small interfering, chromatin immunoprecipitation, cell proliferation, luciferase reporter