IL-32θ inhibits monocytic differentiation of leukemia cells by attenuating expression of transcription factor PU.1.
PU.1 is a key transcription factor regulating the myeloid differentiation. PU.1-induced monocytic differentiation into macrophage is also important for blood cancer development. Therefore, we chose THP-1 monocytic leukemia cells to investigate the function of a recently discovered IL-32θ. Genetic analyses identified differences in the sequences of IL-32θ and IL-32β. Using previously established cell lines that stably express IL-32θ and IL-32β and cell lines transiently expressing IL-32θ, we observed that expression of IL-32θ inhibited phorbol 12-myristate 13-acetate (PMA)-induced monocytic differentiation in both THP-1 and HL-60 cells. IL-32θ also suppressed expression of the macrophage cell surface markers, CD11b, CD18, and CD36. Interestingly, expression of IL-32β or IL-32θ had no effect on the expression levels of cell cycle related factors. As a result, we concluded that these isoforms did not contribute to PMA-induced cell cycle arrest. IL-32θ was found to modulate expression of PU.1, a transcription factor necessary for myeloid lineage commitment. Transient expression of PU.1 in THP-1/IL-32θ cells rescued the observed differentiation defect. Additionally, transient expression of both CCAAT-enhancer-binding protein α (C/EBPα) and PU.1 in THP-1/IL-32θ cells exhibited synergistic effects in rescuing the differentiation defect. These observations indicate that intracellular IL-32θ inhibits the differentiation of monocytes into macrophages by attenuating PU.1 expression.
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Man Sub
MS
Kim
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Jeong-Woo
JW
Kang
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Yun Sun
YS
Park
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Dong Hun
DH
Lee
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Yesol
Y
Bak
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Taeho
T
Kwon
Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea.
Do-Young
DY
Yoon
D002454:Cell Differentiation / Q000502:physiology*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D007378:Interleukins / Q000378:metabolism*; D007938:Leukemia / Q000473:pathology*; D009000:Monocytes / Q000473:pathology*; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D060888:Real-Time Polymerase Chain Reaction; D015534:Trans-Activators / Q000096:biosynthesis*; D014162:Transfection; D000099232:Proto-Oncogene Protein Spi-1
D007378:Interleukins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; C496971:IL32 protein, human