Tumor-Associated Endothelial Cells Promote Tumor Metastasis by Chaperoning Circulating Tumor Cells and Protecting Them from Anoikis.
Tumor metastasis is a highly inefficient biological process as millions of tumor cells are released in circulation each day and only a few of them are able to successfully form distal metastatic nodules. This could be due to the fact that most of the epithelial origin cancer cells are anchorage-dependent and undergo rapid anoikis in harsh circulating conditions. A number of studies have shown that in addition to tumor cells, activated endothelial cells are also released into the blood circulation from the primary tumors. However, the precise role of these activated circulating endothelial cells (CECs) in tumor metastasis process is not known. Therefore, we performed a series of experiments to examine if CECs promoted tumor metastasis by chaperoning the tumor cells to distal sites. Our results demonstrate that blood samples from head and neck cancer patients contain significantly higher Bcl-2-positive CECs as compared to healthy volunteers. Technically, it is challenging to know the origin of CECs in patient blood samples, therefore we used an orthotopic SCID mouse model and co-implanted GFP-labeled endothelial cells along with tumor cells. Our results suggest that activated CECs (Bcl-2-positive) were released from primary tumors and they co-migrated with tumor cells to distal sites. Bcl-2 overexpression in endothelial cells (EC-Bcl-2) significantly enhanced adhesion molecule expression and tumor cell binding that was predominantly mediated by E-selectin. In addition, tumor cells bound to EC-Bcl-2 showed a significantly higher anoikis resistance via the activation of Src-FAK pathway. In our in vivo experiments, we observed significantly higher lung metastasis when tumor cells were co-injected with EC-Bcl-2 as compared to EC-VC. E-selectin knockdown in EC-Bcl-2 cells or FAK/FUT3 knockdown in tumor cells significantly reversed EC-Bcl-2-mediated tumor metastasis. Taken together, our results suggest a novel role for CECs in protecting the tumor cells in circulation and chaperoning them to distal sites.
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, 43210, United States of America.
Arti
A
Yadav
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, 43210, United States of America; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, Ohio, 43210, United States of America.
Bhavna
B
Kumar
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, 43210, United States of America.
Jun-Ge
JG
Yu
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, 43210, United States of America; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, Ohio, 43210, United States of America.
Matthew
M
Old
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, 43210, United States of America; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, Ohio, 43210, United States of America.
Theodoros N
TN
Teknos
The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, 43210, United States of America; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, Ohio, 43210, United States of America.
Pawan
P
Kumar
D000818:Animals; D023102:Anoikis; D002450:Cell Communication; D002478:Cells, Cultured; D018920:Coculture Techniques; D004195:Disease Models, Animal; D019040:E-Selectin / Q000235:genetics / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D015870:Gene Expression; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000473:pathology; D064593:Heterografts; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000556:secondary; D051379:Mice; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009360:Neoplastic Cells, Circulating / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism
D019040:E-Selectin; D019253:Proto-Oncogene Proteins c-bcl-2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases