Abstract
Tumor hypoxic regions are more resistant to chemo- and radiation- therapy due to the ineficiency of drug delivery or unfixable DNA damages resulted from low concentration of oxygen. Therefore, therapeutic strategy improvements are desperately needed to treat these tumor microenvironments. Murine prostate cancer, TRAMP-C1, was used as a research model. A vector of six-tandem repeats of bidirectional enhancers, hypoxia response element (HRE), inserted with murine interleukin-3 (mIL-3) as a working gene at one arm was used to create a new cell line named TRAMP-C1-HRE-IL3, in order to regulate the secretion of IL-3 within hypoxic regions for monitoring changes in the tumor micrenvironments and macrophage aggregation.ELISA and RT-PCR results showed that the expression of IL-3 was induced after Deferoxamine (DFX) treatment or hypoxia-mimic environment incubation (1% O2、5% CO2、94% N2). The tumor growth and microenvironment changes in three different cancer cell lines, TRAMP-C1, TRAMP-C1-IL3 and TRAMP-C1-HRE-IL3, on C57BL/6J mice were compared. The data showed that TRAMP-C1- HRE-IL3 tumors can enhance the migration of macrophages toward hypoxia regions to as high as 1.7 folds comparing with the other two types of control tumors, and have the similar aggregation patterns in the pre-IR tumor model. Further experiments proved that this migration enhancement is directly related to IL-3 secretion from cancer cells. Additionally, spleen enlargement, a side effect from original IL-3 gene therapy, is greatly reduced by using TRAMP-C1-HRE-IL3. To sum up, the side effects of using IL-3 were lowered by regulating its secretion with HRE, and at the same time, a macrophage migration and aggregation favorable environment was created within the tumor hypoxic regions. In combination with monocyte-macrophage drug delivery system and radiation-therapy, it is hoped that it will resulted as a better anti-cancer strategy.