DPP4 and leukemia: Ikeda et al. demonstrated that the binding of soluble DPP4 to human monocytes and THP-1 cells (a human leukemia monocytic cell line) enhanced the LPS-induced IL6 and TNFα mRNA and protein expression and the upregulation of ERK in the cytosol and c-fos, NF-κB p65/p50, and CUX1 transcription factors in the nucleus.