ANXA2 (annexin A2) is crucial to ATG7-mediated autophagy, leading to tumor aggressiveness in triple-negative breast cancer cells.

Triple-negative breast cancer (TNBC) is associated with a poor prognosis and metastatic growth. TNBC cells frequently undergo macroautophagy/autophagy, contributing to tumor progression and chemotherapeutic resistance. ANXA2 (annexin A2), a potential therapeutic target for TNBC, has been reported to stimulate autophagy. In this study, we investigated the role of ANXA2 in autophagic processes in TNBC cells. TNBC patients exhibited high levels of ANXA2, which correlated with poor outcomes. ANXA2 increased LC3B-II levels following bafilomycin A1 treatment and enhanced autophagic flux in TNBC cells. Notably, ANXA2 upregulated the phosphorylation of HSF1 (heat shock transcription factor 1), resulting in the transcriptional activation of ATG7 (autophagy related 7). The mechanistic target of rapamycin kinase complex 2 (MTORC2) played an important role in ANXA2-mediated ATG7 transcription by HSF1. MTORC2 did not affect the mRNA level of ANXA2, but it was involved in the protein stability of ANXA2. HSPA (heat shock protein family A (Hsp70)) was a potential interacting protein with ANXA2, which may protect ANXA2 from lysosomal proteolysis. ANXA2 knockdown significantly increased sensitivity to doxorubicin, the first-line chemotherapeutic regimen for TNBC treatment, suggesting that the inhibition of autophagy by ANXA2 knockdown may overcome doxorubicin resistance. In a TNBC xenograft mouse model, we demonstrated that ANXA2 knockdown combined with doxorubicin administration significantly inhibited tumor growth compared to doxorubicin treatment alone, offering a promising avenue to enhance the effectiveness of chemotherapy. In summary, our study elucidated the molecular mechanism by which ANXA2 modulates autophagy, suggesting a potential therapeutic approach for TNBC treatment.Abbreviation: ATG: autophagy related; ChIP: chromatin-immunoprecipitation; HBSS: Hanks' balanced salt solution; HSF1: heat shock transcription factor 1; MTOR: mechanistic target of rapamycin kinase; TNBC: triple-negative breast cancer; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3.

Discoidin domain receptor 1 is a novel transcriptional target of ZEB1 in breast epithelial cells undergoing H-Ras-induced epithelial to mesenchymal transition.

The epithelial-to-mesenchymal transition (EMT) process allows carcinoma cells to dissociate from the primary tumor thereby facilitating tumor cell invasion and metastasis. Ras-dependent hyperactive signaling is commonly associated with tumorigenesis, invasion, EMT, and metastasis. However, the downstream effectors by which Ras regulates EMT remain ill defined. In this study, we show that the H-Ras pathway leads to mesenchymal-like phenotypic changes in human breast epithelial cells by controlling the ZEB1/microRNA-200c axis. Moreover, H-Ras suppresses the expression of the discoidin domain receptor 1 (DDR1), a collagen receptor tyrosine kinase, via ZEB1, thus identifying ZEB1 as a novel transcriptional repressor of DDR1. Mutation studies on the putative promoter of the DDR1 gene revealed that bipartite Z- and E-box elements play a key role in transcriptional repression of DDR1 in Hs578T and MDA-MB-231 breast carcinoma cell lines by ZEB1. Furthermore, we found an inverse correlation between ZEB1 and DDR1 expression in various cancer cell lines and in human breast carcinoma tissues. Consistently, overexpression of DDR1 reduced the invasive phenotype of mesenchymal-like triple-negative breast cancer cells in 3D cultures and in vivo. Thus, ZEB1's role in maintenance of EMT in breast carcinoma cells is mediated in part by its ability to suppress DDR1 expression and consequently contribute to the activation of the invasive phenotype. Taken together, our results unveil a novel H-Ras/ZEB1/DDR1 network that contributes to breast cancer progression in triple-negative breast cancers.