The role of CCL21/CCR7 chemokine axis in breast cancer-induced lymphangiogenesis.
BACKGROUND
Tumor-induced lymphangiogenesis facilitates breast cancer progression by generating new lymphatic vessels that serve as conduits for tumor dissemination to lymph nodes and beyond. Given the recent evidence suggesting the implication of C-C chemokine ligand 21/chemokine receptor 7 (CCL21/CCR7) in lymph node metastasis, the aim of our study was to define the role of this chemokine pair in breast cancer-associated lymphangiogenesis.


METHODS
The expression analysis of CCL21/CCR7 pair and lymphatic endothelial cell (LEC) markers in breast cancer specimens was performed by means of quantitative real-time PCR. By utilizing CCR7 and CCL21 gene manipulated breast cancer cell implants into orthotopic sites of nude mice, lymphatic vessel formation was assessed through quantitative real-time PCR, immunohistochemistry and immunofluorescence assays. Finally, the lymphangiogenic potential of CCL21/CCR7 was assessed in vitro with primary LECs through separate functional assays, each attempting to mimic different stages of the lymphangiogenic process.


RESULTS
We found that CCR7 mRNA expression in human breast cancer tissues positively correlates with the expression of lymphatic endothelial markers LYVE-1, podoplanin, Prox-1, and vascular endothelial growth factor-C (VEGF-C). We demonstrated that the expression of CCL21/CCR7 by breast cancer cells has the ability to promote tumor-induced lymph-vascular recruitment in vivo. In vitro, CCL21/CCR7 chemokine axis regulates the expression and secretion of lymphangiogenic factor VEGF-C and thereby promotes proliferation, migration, as well as tube formation of the primary human LECs. Finally, we showed that protein kinase B (AKT) signaling pathway is the intracellular mechanism of CCR7-mediated VEGF-C secretion by human breast cancer cells.


CONCLUSIONS
These results reveal that CCR7 and VEGF-C display a significant crosstalk and suggest a novel role of the CCL21/CCR7 chemokine axis in the promotion of breast cancer-induced lymphangiogenesis.
Department of Anatomy & Cell Biology, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St, London, ON, N6A 5C1, Canada. etutunea@uwo.ca.
Elena
E
Tutunea-Fatan
Department of Anatomy & Cell Biology, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St, London, ON, N6A 5C1, Canada. mmajumde@uwo.ca.
Mousumi
M
Majumder
Department of Anatomy & Cell Biology, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St, London, ON, N6A 5C1, Canada. xiping.xin@schulich.uwo.ca.
Xiping
X
Xin
Department of Anatomy & Cell Biology, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St, London, ON, N6A 5C1, Canada. pklala@uwo.ca.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, 790 Commissioners Rd. E, London, ON, N6A 4L6, Canada. pklala@uwo.ca.|Children's Health Research Institute, 800 Commissioners Rd. E, London, ON, N6C 2V5, Canada. pklala@uwo.ca.
Peeyush K
PK
Lala
D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D054421:Chemokine CCL21 / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D042583:Lymphangiogenesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D054400:Receptors, CCR7 / Q000378:metabolism*; D015398:Signal Transduction; D042582:Vascular Endothelial Growth Factor C / Q000235:genetics / Q000378:metabolism
D054421:Chemokine CCL21; D054400:Receptors, CCR7; D042582:Vascular Endothelial Growth Factor C; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt