Autophagy Blockade by Ai Du Qing Formula Promotes Chemosensitivity of Breast Cancer Stem Cells Via GRP78/β-Catenin/ABCG2 Axis.

Accumulating evidence suggests that the root of drug chemoresistance in breast cancer is tightly associated with subpopulations of cancer stem cells (CSCs), whose activation is largely dependent on taxol-promoting autophagy. Our pilot study identified GRP78 as a specific marker for chemoresistance potential of breast CSCs by regulating Wnt/β-catenin signaling. Ai Du Qing (ADQ) is a traditional Chinese medicine formula that has been utilized in the treatment cancer, particularly during the consolidation phase. In the present study, we investigated the regulatory effects and molecular mechanisms of ADQ in promoting autophagy-related breast cancer chemosensitivity. ADQ with taxol decreasing the cell proliferation and colony formation of breast cancer cells, which was accompanied by suppressed breast CSC ratio, limited self-renewal capability, as well as attenuated multi-differentiation. Furthermore, autophagy in ADQ-treated breast CSCs was blocked by taxol via regulation of β-catenin/ABCG2 signaling. We also validated that autophagy suppression and chemosensitizing activity of this formula was GRP78-dependent. In addition, GRP78 overexpression promoted autophagy-inducing chemoresistance in breast cancer cells by stabilizing β-catenin, while ADQ treatment downregulated GRP78, activated the Akt/GSK3β-mediated proteasome degradation of β-catenin via ubiquitination activation, and consequently attenuated the chemoresistance-promoted effect of GRP78. In addition, both mouse breast cancer xenograft and zebrafish xenotransplantation models demonstrated that ADQ inhibited mammary tumor growth, and the breast CSC subpopulation showed obscure adverse effects. Collectively, this study not only reveals the chemosensitizating mechanism of ADQ in breast CSCs, but also highlights the importance of GRP78 in mediating autophagy-promoting drug resistance via β-catenin/ABCG2 signaling.

Liao M ，Wang C ，Yang B ，Huang D ，Zheng Y ，Wang S ，Wang X ，Zhang J ，Tang C ，Xu Z ，He Y ，Huang R ，Zhang F ，Wang Z ，Wang N ... -  《Frontiers in Pharmacology》

Dietary compound isoliquiritigenin targets GRP78 to chemosensitize breast cancer stem cells via β-catenin/ABCG2 signaling.

Accumulating evidence suggests that β-catenin signaling in breast cancer stem cells (CSCs) is closely correlated to chemoresistance and adenosine triphosphate (ATP)-binding cassette subfamily G2 (ABCG2) expression. Targeting the aberrant β-catenin signaling in CSCs has become a promising strategy to improve chemosensitivity in cancer treatment. In a pilot screening study, we found that the natural compound isoliquiritigenin (ISL) blocked β-catenin transcription activity with the highest inhibition ratio. Here, we investigated the chemosensitizing effects of ISL on breast CSCs and the underlying mechanisms regulating the β-catenin pathway. ISL could have synergistic effects with chemotherapeutic drugs to inhibit breast cancer cell proliferation and colony formation. In addition, ISL could significantly limit the side population and CSC ratios in breast cancer cells, accompanied by inhibited self-renewal and multidifferentiation abilities. A mechanistic study revealed that ISL could inhibit β-catenin/ABCG2 signaling by activating the proteasome degradation pathway. The drug affinity responsive target stability strategy further identified GRP78 as the direct target of ISL. Subsequent molecular docking analysis and functional studies demonstrated that ISL could dock into the ATP domain of GRP78 and thereby inhibit its ATPase activity, resulting in its dissociation from β-catenin. An in vivo study also suggested that ISL could chemosensitize breast CSCs via the GRP78/β-catenin/ABCG2 pathway, with little toxicity in normal tissues and mammary stem cells. Taken together, the data from this study not only suggest ISL as a natural candidate to enhance breast CSC chemosensitivity but also highlight the significance of GRP78 in mediating cancer drug resistance and β-catenin signaling in CSCs.

Wang N ，Wang Z ，Peng C ，You J ，Shen J ，Han S ，Chen J ... -  《-》

Corrigendum: Autophagy Blockade by Ai Du Qing Formula Promotes Chemosensitivity of Breast Cancer Stem Cells Via GRP78/β-Catenin/ABCG2 Axis.

[This corrects the article DOI: 10.3389/fphar.2021.659297.].

Liao M ，Wang C ，Yang B ，Huang D ，Zheng Y ，Wang S ，Wang X ，Zhang J ，Tang C ，Xu Z ，He Y ，Huang R ，Zhang F ，Wang Z ，Wang N ... -  《-》

Caveolin-1 mediates chemoresistance in breast cancer stem cells via β-catenin/ABCG2 signaling pathway.

Accumulating evidence has suggested that cancer stem cells (CSCs) are at the root of drug resistance, and recent studies have indicated that caveolin-1, a membrane transporter protein, is involved in the regulation of cancer chemoresistance and stem cell signaling. However, the current understanding of the role of caveolin-1 in breast cancer development remains controversial. Herein, we demonstrate that caveolin-1 expression was upregulated after breast cancer chemotherapy in vitro and in vivo, accompanied by co-overexpression of β-catenin and ATP-binding cassette subfamily G member 2 (ABCG2) signaling. Additionally, breast CSCs were enriched for caveolin-1 expression. Caveolin-1 silencing sensitized breast CSCs by limiting their self-renewal ability but promoting the differentiation process. β-catenin silencing prevented the enhanced chemoresistance of CSCs induced by caveolin-1 overexpression, indicating that β-catenin is an essential molecule responsible for caveolin-1-mediated action. Further mechanistic investigation revealed that caveolin-1 silencing could downregulate the β-catenin/ABCG2 pathway through glycogen synthase kinase 3 beta activation and Akt inhibition, resulting in increased β-catenin phosphorylation and proteasomal degradation. Clinical investigation also revealed a close correlation between caveolin-1 and β-catenin/ABCG2 signaling in breast cancer samples. Notably, caveolin-1 was highly elevated in triple-negative breast cancer, and caveolin-1 silencing significantly impaired the tumorigenicity and chemoresistance of breast CSCs in in vivo models. Overall, our study not only highlights the role of caveolin-1 in mediating the chemoresistance of breast CSCs via β-catenin/ABCG2 regulation but also provides novel approaches for future therapies targeting CSCs.

Wang Z ，Wang N ，Li W ，Liu P ，Chen Q ，Situ H ，Zhong S ，Guo L ，Lin Y ，Shen J ，Chen J ... -  《-》

Aiduqing formula suppresses breast cancer metastasis via inhibiting CXCL1-mediated autophagy.

Metastasis is the most common lethal cause of breast cancer-related death. Recent studies have implied that autophagy is closely implicated in cancer metastasis. Therefore, it is of great significance to explore autophagy-related molecular targets involved in breast cancer metastasis and to develop therapeutic drugs. This study was designed to investigate the anti-metastatic effects and autophagy regulatory mechanisms of Aiduqing (ADQ) formula on breast cancer. Multiple cellular and molecular experiments were conducted to investigate the inhibitory effects of ADQ formula on autophagy and metastasis of breast cancer cells in vitro. Meanwhile, autophagic activator/inhibitor as well as CXCL1 overexpression or interference plasmids were used to investigate the underlying mechanisms of ADQ formula in modulating autophagy-mediated metastasis. Furthermore, the zebrafish xenotransplantation model and mouse xenografts were applied to validate the inhibitory effect of ADQ formula on autophagy-mediated metastasis in breast cancer in vivo. ADQ formula significantly inhibited the proliferation, migration, invasion and autophagy but induced apoptosis of high-metastatic breast cancer cells in vitro. Similar results were also observed in starvation-induced breast cancer cells which exhibited elevated metastatic ability and autophagy activity. Mechanism investigations further approved that either CXCL1 overexpression or autophagic activator rapamycin can significantly abrogated the anti-metastatic effects of ADQ formula, suggesting that CXCL1-mediated autophagy may be the crucial pathway of ADQ formula in suppressing breast cancer metastasis. More importantly, ADQ formula suppressed breast cancer growth, autophagy, and metastasis in both the zebrafish xenotransplantation model and the mouse xenografts. Our study not only revealed the novel function of CXCL1 in mediating autophagy-mediated metastasis but also suggested ADQ formula as a candidate drug for the treatment of metastatic breast cancer.

Yang B ，Peng F ，Zhang Y ，Wang X ，Wang S ，Zheng Y ，Zhang J ，Zeng Y ，Wang N ，Peng C ，Wang Z ... -  《-》