Stem-Like Tumor Cells Involved in Heterogeneous Vasculogenesis in Breast Cancer: A Possible Reason for the Poor Curative Effects of Antiangiogenic Therapy

Background: Potent angiogenesis inhibitor Sorafenib has been proved invalid in breast cancer clinical trial due to its limited effects on heterogeneous vasculatures, but the mechanism remains unclear. Methods: Here we isolated ALDH1 and ALDH1- MDA-MB-231 cells by a FACS sorter and cultured them in a 3D matrix to examined tube formation ability. Triple-negative breast cancer (TNBC) tissues and xenograft animal model tissue paraffin sections were pretreated as for IHC. We also applied various molecular biological methods combining with cell model, animal model and patients’ tissue to approach to this question. Findings: We found that breast cancer stem-like cells (BCSLCs, ALDH1 cells) are involved in vascular mimicry and mosaic vessels in triple-negative breast cancer tissues. Further, only ALDH1 BCSLCs sorted from MDA-MB-231 could exhibit the tube formation and angiogenesis ability. Sorafenib could inhibit vascularization from endothelial cells rather than that from ALDH1 cells. α-SMA was identified as a key molecule in vascular formation of BCSLCs. Mechanistically, HIF-1α enhanced the mRNA and protein levels of α-SMA by binding to the HRE element in the promoter directly and meanwhile increased the BCSLCs population. Interestingly, Pigment Epithelium-Derived Factor (PEDF), could inhibit both endothelial cell-derived and tumor cell-derived angiogenesis by down-regulating HIF-1α in breast cancer. Interpretation: Our finding clarified the possible reason for the poor outcome of anti-angiogenesis therapy and PEDF may have the therapeutic potential. Funding Statement: This study was supported by National Nature Science Foundation of China, Grant Number: 81872165, 81572342, 81770808, 81471033, 81600641, 81370945, 81570871, 81570764,81701414,81871211,81502507; National Key Sci-Tech Special Project of China, Grant Number:2013ZX09102-053, 2015GKS-355; Key Project of Nature Science Foundation of Guangdong Province, China, Grant Number: 2015A030311043, 2016A030311035. Guangdong Natural Science Fund, Grant Number: 2014A020212023, 2014A030313073, 2015A030313029, 2015A030313103; Guangdong Science Technology Project, Grant Number: 2017A020215075; Initiate Research Funds for the Central Universities of China (Youth Program), Grant Number: 13ykpy06, 14ykpy05, 16ykpy24. Key Sci-tech Research Project of Guangzhou Municipality, China, Grant Number: 201508020033, 201510010052, 201707010084, 201803010017; Pearl River Nova Program of Guangzhou Municipality, China, Grant number: 201610010186; 2017 Milstein Medical Asian American Partnership Foundation Research Project Award in Translational Medicine. Declaration of Interests: The authors have declared that no conflict of interest exists. Ethics Approval Statement: This study was approved by the medical ethics committee of Sun Yat-sen University for Medical Sciences, Guangzhou.