Bladder cancer cells re-educate TAMs through lactate shuttling in the microfluidic cancer microenvironment
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Yang Zhao1,*, Degui Wang2,*, Ting Xu3,*, Pengfei Liu1, Yanwei Cao4, Yonghua Wang4, Xuecheng Yang4, Xiaodong Xu4, Xinsheng Wang4, Haitao Niu4
1Department of Surgery, Affiliated Hospital of Qingdao University, Qingdao, China
2Department of Anatomy, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
3Department of Geratology, The 401st Hospital of PLA, Qingdao, China
4Department of Urology, Affiliated Hospital of Qingdao University, Key Laboratory of Urinary System Diseases, Qingdao, China
*These authors have contributed equally to this work
Haitao Niu, e-mail: Niuht0532@126.com
Xinsheng Wang, e-mail: firstname.lastname@example.org
Keywords: bladder cancer, lactate, microfluidic chips, tumor-associated macrophage, re-education
Received: April 21, 2015 Accepted: October 02, 2015 Published: October 13, 2015
Background: In the present study, we aimed to investigate the influence of lactate shuttling on the functional polarization and spatial distribution of transitional cell carcinoma of the bladder (TCCB) cells and macrophages.
Methods: We designed a microfluidic coculture chip for real-time integrative assays. The effect of lactate shuttling on the re-education of macrophages by TCCB cells was explored by measuring the levels of NO using a total NO assay kit and by evaluating the protein expression of iNOS, p-NFkB-p65, Arg-1 and HIF-1α via cell immunofluorescence and western blotting. Additionally, we examined TCCB cell viability using acridine orange/ethidium bromide (AO/EB) and MitoTracker staining. Moreover, the concentration distributions of lactate and large signaling proteins in the culture chambers were measured using 4′,6-diamidino-2-phenylindole (DAPI) and fluorescein isothiocyanate-dextran (FITC-dextran). Furthermore, the recruitment of macrophages and the influence of macrophages on BC metastasis were observed via light microscopy.
Results: We confirmed that TCCB cells reprogrammed macrophages into an M2 phenotype. Moreover, lactate inhibited M1 polarization and induced M2 polarization of macrophages, but blockade of cancer cell-macrophage lactate flux significantly inhibited the re-education of macrophages by TCCB cells. In addition, lactate diffused faster and deeper than large signaling proteins in the microfluidic tumor microenvironment. Furthermore, lactate alone induced the migration of macrophages, and M1, but not M2, macrophages reduced the motility of TCCB cells.
Conclusions: TCCB cells reprogrammed macrophages into an M2 phenotype in a manner that depended on cancer cell-TAM lactate flux. Furthermore, the lactate shuttle may be a determinant of the density of TAMs in tumor tissue.
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