Abstract
Previous studies have known that radiotherapy could course the aggregation of macrophages in hypoxia areas. We hypothesize that the tumor-homing ability of tumor-associated macrophages (TAM) rendered it as a potential cellular carrier. To investigate this hypothesis, we used an established pre-clinical recurring prostate tumor (TRAMP-C1) model to study the infiltration pattern of bone marrow derived cells (BMDCs). 24 hours before the irradiation, 2×106 BMDCs or differentiated monocytes- expressing EGFP were injected i.v. The peripheral bloods and tumor microenvironment were analyzed by the flow cytometry and immunofluorescence staining. The results show that the largest number of BMDCs and monocytes infiltrated into tumor microenvironment occurred 1 week after cell injection, which was more notable in irradiated tumor, but not found at hypoxia regions. To investigate the hypoxic effect for migrated ability of monocytes, monocytes were differentiated in hypoxia conditions (2% O2) for the duration of 24, 48 or 72 hours. The results show that the migration rate of monocyts was restrained under hypoxia conditions, and the degrees of hypoxia condition have different effects on monocytes differentiation. The significant recruitment of monocytes into irradiated tumor microenvironment suggests that monocytes could be a potential cellular carrier for target therapy to enhance the efficiency of radiotherapy.