Effect of oxidized multiwalled carbon nanotubes and hyperthermia treatment on EMT6 tumor microenvironment

Abstract

Tumor microenvironment has been identified as a crucial player in influencing anti-tumor immune response in breast cancer. Alternative treatment using combination of carbon nanotubes (CNTs) with hyperthermia (HT) has been reported to reduce tumor burden. However, its immunological mechanisms in tumor microenvironment is not yet fully understood. Hence, this study was conducted to investigate the effect of combination of ox-MWCNT and hyperthermia treatment on immune responses in tumor microenvironment. In this study, EMT6 breast cancer cells were inoculated subcutaneously into right flank of female Balb/c mice. At day 7 post-inoculation, ox-MWCNT were injected intratumorally in CNT and combined groups. Then, mice in combined and HT were subjected to local HT for three consecutive days. Mice for control group was left untreated. Mice were euthanized 10 days post-inoculation and their lymph nodes were harvested for flow cytometric (FACS) analysis while the tumors were subjected for immunohistochemistry (IHC) analysis. In another experiment, mice were euthanized 21 days post-inoculation and tumors were harvested for FACS analysis. Results from this study demonstrated that the infiltration and maturation of DCs in lymph nodes increased in combined treated groups. In addition, FACS analysis of tumor cells showed that combined treatment significantly increased the infiltration of CD8+ and CD4+ T cells, natural killer (NK) cells and macrophages. Furthermore, combined and HT alone has shown to drastically decrease Tregs population in tumor. On the other hand, data from the IHC studies indicated that angiogenesis activity increased in combination therapy but had less influence on inducing tumor progression. Data presented in this study highlights the potential therapeutic use of ox-MWCNT with HT treatment against breast cancer. Information gained from this research may contribute to understand on the effect of combined treatment on tumor microenvironment and may have implications in breast cancer management in clinical setting.