Signal transducer and activator of transcription 3 downregulation in J774A.1 cell line as a model of M2 macrophages in tumor microenvironment.

Aim: Tumor-associated macrophages (TAMs) play a decisive role in the regulation of tumor progression by manipulating tumor oncogenesis, angiogenesis, and immune functions within tumor microenvironments. Tumor progression is frequently associated with a phenotypic switch from M1 to M2 in TAM. Activation of signal transducer and activator of transcription 3 (STAT3) in TAM lead to tumor-induced immunosuppression. STAT3 is usually constitutively activated in a variety of malignancies. Consequently, STAT3 has emerged as a promising target for cancer immunotherapy.

Materials And Methods: In this study, J774A.1 cell line which is an M2 macrophage and overexpress STAT3 was cultured in Dulbecco's Modified Eagle Medium supplemented by fetal bovine serum. Then, the STAT3 silencing was evaluated by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) using oligofectamine containing STAT3 short interfering RNA (siRNA). Oligofectamine containing STAT3 siRNA and control siRNA were added at a final concentration of 100 nM siRNA. The untransfected cells were considered as control group.

Results: The semi-quantitative RT-PCR studies showed that J774A.1 cells express a high level of STAT3. Incubation of J774A.1 cells with oligofectamine containing STAT3 siRNA knockdown the STAT3 expression significantly both in 48 and 72 h study; however, the effect was more pronounced in 72 h study.

Conclusion: The expression of STAT3 in J774A.1 cells confirmed that these cells are M2 macrophage. Moreover, silencing of STAT3 by siRNA delivery using oligofectamine delivery suggests that siRNA delivery using vehicles like nanoliposome could be a useful therapeutic agent in M2 macrophage therapy and its switch to M1 macrophages. This approach could be considered as a novel therapeutic agent for the treatment of all cancers.