ANXA4 Activates JAK-STAT3 Signaling by Interacting with ANXA1 in Basal-Like Breast Cancer

Annexin A4 (encoded by theANXA4gene) is a calcium ion (Ca2+)- and phospholipid-binding protein of the Annexin family. In this study, we checked the expression profile ofANXA4in basal-like breast cancer (BLBC) and its association with survival outcomes using pan-cancer data from The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) project. Then, using MDA-MB-231 and MDA-MB-468 cells, we explored the functional role of ANXA4 in regulating a cancer-related signaling pathway and identified potential partners of ANXA4. The results showed that expression of totalANXA4and the two dominant ANXA4 protein-coding transcripts (ENST00000409920.5 and ENST00000394295.4) was consistently upregulated in tumor tissues compared with normal breast tissues. BLBC patients with highANXA4expression had significantly worse overall survival, progression-free survival, and disease-free survival than those with lowANXA4expression. ANXA4 could positively modulate cyclin D1 expression and G1/S progression in the two cell lines. Anin vivotumor model showed thatANXA4inhibition significantly slowed the growth of tumors derived from the two BLBC cell lines. ANXA4 could increase JAK1 expression and STAT3 phosphorylation (Y705). ANXA4 colocalized with ANXA1 in some MDA-MB-231 cells. A co-immunoprecipitation assay confirmed direct binding between ANXA4 and ANXA1. Knockdown ofANXA1reduced JAK1 expression and STAT3 phosphorylation and impaired ANXA4-induced upregulation of JAK1 and p-STAT3. In conclusion, this study revealed that aberrantANXA4upregulation is associated with poor survival in BLBC. ANXA4 could activate JAK-STAT3 signaling by elevating the expression of JAK1 and p-STAT3, which was mediated by direct interaction with ANXA1.