Tyrosine hydroxylase as a therapeutic target: insights from adrenergic nerve and TNBC cell interactions

The sympathetic adrenergic nerves (SAN) play a significant role in the malignant transformation of breast cancer cells through the activity of norepinephrine (NE). However, the role of tyrosine hydroxylase (TH), a key enzyme of the NE synthesis, in the interaction between the SAN and triple-negative breast cancer (TNBC) cells has not been sufficiently explored, and whether TH can be a therapeutic target for TNBC has not been reported. TH expression in TNBC was examined by analyzing data from an online database and immunohistochemical analysis of our clinical samples. Cell proliferation and drug sensitivity were assessed upon coculture with fluorescently labeled cells using IncuCyte. Changes in the expression of DNA damage and apoptosis-associated proteins were assessed by western blotting. TH expression and NE synthesis in PC12 cells after their coculture with TNBC cells were measured by RT-qPCR, immunofluorescence, and ELISA. RNA sequencing was conducted on the cells before and after coculture. TH expression was relatively high in TNBC tumor tissues and closely associated with prognosis. SAN promoted TNBC cell proliferation through NE and reduced TNBC cell sensitivity to chemotherapeutic agents. Additionally, tumor cells induced TH expression in PC12 cells through nerve growth factor (NGF) secretion. Knocking down TH and using TH inhibitors effectively reversed the proliferation-promoting and drug sensitivity-reducing effects of SAN in TNBC cells. TH may be a central molecule in the positive feedback loop between TNBC cells and SAN. TH is a potential prognostic biomarker and can also serve as a therapeutic target for TNBC. KEY MESSAGES: The overexpression of the sympathetic nerve biomarker tyrosine hydroxylase (TH) in triple-negative breast cancer (TNBC) is an indicator for clinical staging, prognosis, and targeted therapy. There is a feedback loop where TH in nerves produces NE, worsening TNBC and reducing chemotherapy effectiveness. TNBC cell then increases TH expression, further boosting NE production. Furthermore, blocking the activity of TH could effectively inhibit this phenotype.