Doxycycline attenuates breast cancer related inflammation by decreasing plasma lysophosphatidate concentrations and inhibiting NF-κB activation.
We previously discovered that tetracyclines increase the expression of lipid phosphate phosphatases at the surface of cells. These enzymes degrade circulating lysophosphatidate and therefore doxycycline increases the turnover of plasma lysophosphatidate and decreases its concentration. Extracellular lysophosphatidate signals through six G protein-coupled receptors and it is a potent promoter of tumor growth, metastasis and chemo-resistance. These effects depend partly on the stimulation of inflammation that lysophosphatidate produces.



In this work, we used a syngeneic orthotopic mouse model of breast cancer to determine the impact of doxycycline on circulating lysophosphatidate concentrations and tumor growth. Cytokine/chemokine concentrations in tumor tissue and plasma were measured by multiplexing laser bead technology. Leukocyte infiltration in tumors was analyzed by immunohistochemistry. The expression of IL-6 in breast cancer cell lines was determined by RT-PCR. Cell growth was measured in Matrigel™ 3D culture. The effects of doxycycline on NF-κB-dependent signaling were analyzed by Western blotting.



Doxycycline decreased plasma lysophosphatidate concentrations, delayed tumor growth and decreased the concentrations of several cytokines/chemokines (IL-1β, IL-6, IL-9, CCL2, CCL11, CXCL1, CXCL2, CXCL9, G-CSF, LIF, VEGF) in the tumor. These results were compatible with the effects of doxycycline in decreasing the numbers of F4/80+macrophages and CD31+blood vessel endothelial cells in the tumor. Doxycycline also decreased the lysophosphatidate-induced growth of breast cancer cells in three-dimensional culture. Lysophosphatidate-induced Ki-67 expression was inhibited by doxycycline. NF-κB activity in HEK293 cells transiently expressing a NF-κB-luciferase reporter vectors was also inhibited by doxycycline. Treatment of breast cancer cells with doxycycline also decreased the translocation of NF-κB to the nucleus and the mRNA levels for IL-6 in the presence or absence of lysophosphatidate.



These results contribute a new dimension for understanding the anti-inflammatory effects of tetracyclines, which make them potential candidates for adjuvant therapy of cancers and other inflammatory diseases.
Department of Biochemistry, Signal Transduction Research Group, University of Alberta, Edmonton, AB, T6G 2S2, Canada.
Xiaoyun
X
Tang
Department of Biochemistry, Signal Transduction Research Group, University of Alberta, Edmonton, AB, T6G 2S2, Canada.
Xianyan
X
Wang
Department of Agricultural, Food and Nutritional Science, University of Alberta, 410 Agriculture/Forestry Centre, 3-60D South Academic Building, Edmonton, AB, T6G 2P5, Canada.
Yuan Y
YY
Zhao
Department of Agricultural, Food and Nutritional Science, University of Alberta, 410 Agriculture/Forestry Centre, 3-60D South Academic Building, Edmonton, AB, T6G 2P5, Canada.
Jonathan M
JM
Curtis
Department of Biochemistry, Signal Transduction Research Group, University of Alberta, Edmonton, AB, T6G 2S2, Canada. david.brindley@ualberta.ca.|Department of Biochemistry, 357 Heritage Medical Research Centre, University of Alberta, Edmonton, AB, T6G 2S2, Canada. david.brindley@ualberta.ca.
David N
DN
Brindley
D000818:Animals; D001943:Breast Neoplasms / Q000097:blood / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D016207:Cytokines / Q000097:blood / Q000378:metabolism; D004195:Disease Models, Animal; D004318:Doxycycline / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology*; D018836:Inflammation Mediators / Q000097:blood / Q000378:metabolism; D008246:Lysophospholipids / Q000097:blood*; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D047368:Tumor Burden; D023041:Xenograft Model Antitumor Assays
D016207:Cytokines; D018836:Inflammation Mediators; D008246:Lysophospholipids; D016328:NF-kappa B; D004318:Doxycycline; C032881:lysophosphatidic acid
Autotaxin; Inflammatory cyotokines; Macrophage infiltration; Peripheral blood mononuclear cells; Tetracyclines