Myeloid neoplasm-related gene abnormalities differentially affect dendritic cell differentiation from murine...

Dendritic cells (DCs) play important roles in tumor immunology. Leukemic cells in patients with myeloid neoplasms can differentiate into DCs in vivo (referred to as in vivo leukemic DCs), which are postulated to affect anti-leukemia immune responses. We established a reproducible culture system of in vitro FLT3 ligand-mediated DC (FL-DC) differentiation from murine lineage(-) Sca-1(+) c-Kit(high) cells (LSKs), which made it possible to analyse the effects of target genes on steady-state DC differentiation from hematopoietic stem/progenitor cells. Using this system, we analysed the effects of various myeloid neoplasm-related gene abnormalities, termed class I and class II mutations, on FL-DC differentiation from LSKs. All class II mutations uniformly impaired FL-DC differentiation maintaining a plasmacytoid DC (pDC)/conventional DC (cDC) ratio comparable to the control cells. In contrast, class I mutations differentially affected FL-DC differentiation from LSKs. FLT3-ITD and a constitutively active form of Ras (CA-N-Ras) yielded more FL-DCs than the control, whereas the other class I mutations tested yielded less FL-DCs. Both FLT3-ITD and FLT3-tyrosine kinase domain (TKD) mutation showed a comparable pDC/cDC ratio as the control. CA-N-Ras, c-Kit-TKD, TEL/PDGFRβ, and FIP1L1/PDGFRα showed a severe decrease in the pDC/cDC ratio. CA-STAT5 and CA-MEK1 severely inhibited pDC differentiation. FLT3-ITD, CA-N-Ras, and TEL/PDGFRβ aberrantly induced programmed death ligand-1 (PD-L1)-expressing DCs. In conclusion, we have established a simple, efficient, and reproducible in vitro FL-DC differentiation system from LSKs. This system could uncover novel findings on how myeloid neoplasm-related gene abnormalities differentially affect FL-DC differentiation from murine hematopoietic stem/progenitor cells in a gene-specific manner.