Tumor-Treating Fields Induce RAW264.7 Macrophage Activation Via NK-?B/MAPK Signaling Pathways

Park, Jeong-In; Song, Kyung-Hee; Jung, Seung-Youn; Ahn, Jiyeon; Hwang, Sang-Gu; Kim, Joon; Kim, Eun Ho; Song, Jie-Young

To investigate the signaling pathways involved in the activation of RAW 264.7 cells by TTFs, mitogen-activated protein kinase (MAPK) and nuclear factor-kB (NF-kB) signaling pathways, which are vital targets for regulating inflammatory responses, were examined using Western blot analysis. The expression of 3 MAP kinase family members, namely, ERK, JNK, and p38 MAPK, was determined. The phosphorylation levels of p38 MAPK were significantly increased in TTFsadministered RAW 264.7 cells at 24 hours after treatment. However, activation of MAPK in LPS-treated RAW 264.7 cells was not observed at that time point as LPS treatment activated RAW 264.7 cells more quickly and much more strongly than TTFs treatment. Under normal cell conditions, NF-kB exists as an inactive cytoplasmic complex with its inhibitor IkB-a. 17 Tumor-treating fields-administered RAW 264.7 cells showed increased phosphorylation of IkB-a and p65, indicating that the p65 subunit of NF-kB was released from IkB-a, allowing for its translocation to the nucleus to regulate the transcription of many genes that activate macrophages (Figure 4 ).