ECRG4 suppressed the progression of breast cancer via modulating NFIC/PTEN and SHP2/PI3K/SP1 signaling.

[OBJECTIVE] This study aims to investigate the molecular mechanisms by which ECRG4 regulates breast cancer progression, with a focus on its tumor-suppressive effects mediated through the NFIC/PTEN and SHP2/PI3K/SP1 signaling pathways.

[METHODS] Bioinformatics analysis was used to identify genes associated with ECRG4. Subcutaneous tumor transplantation experiments in nude mice were conducted to assess breast cancer progression; immunohistochemical staining was used to detect the expression of p-SHP2, ECRG4, and NFIC in tumor tissues; Western blot analysis was employed to assess the expression levels of relevant proteins. Scratch assays, Transwell assays, and plate colony formation assays were conducted to evaluate the migration and invasion capabilities of human breast cancer cell line MCF-7, while flow cytometry was used to analyze the cell cycle and apoptosis status of MCF-7 cells.

[RESULTS] Bioinformatics analysis revealed significant associations between ECRG4 and the NFIC/PTEN and SHP2/PI3K/SP1 pathways. Under hypoxic and low-serum conditions, p-SHP2 activates the PI3K/AKT pathway and induces SP1 expression, thereby upregulating the DNA methyltransferase DNMT1 and suppressing the expression of the tumor suppressor gene ECRG4. ECRG4 positively regulates the transcription factor NFIC, leading to increased expression of its downstream target gene PTEN. PTEN negatively feeds back to inhibit the activity of the PI3K/AKT pathway. The activated PI3K/AKT pathway phosphorylates the transcription factor CREB, driving the expression of the E3 ubiquitin ligase SKP2, thereby promoting cell survival. Meanwhile, the pro-apoptotic factors FOXO1/FOXO3a and SKP2 form a bidirectional antagonistic interaction: SKP2 mediates the ubiquitination and degradation of FOXO1/FOXO3a, while FOXO1/FOXO3a can transcriptionally inhibit SKP2 expression, jointly regulating the dynamic balance between apoptosis and survival.

[CONCLUSION] ECRG4 inhibits breast cancer progression by positively regulating NFIC/PTEN to suppress the SHP2/PI3K/SP1 signaling pathway. Targeting this signaling axis may provide a new strategy for breast cancer treatment.