Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, United States.
Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY, United States.
Front Immunol. 2024 Mar 1;15:1297338. doi: 10.3389/fimmu.2024.1297338. eCollection 2024.
Dendritic cells (DC) are mediators between innate and adaptive immune responses to pathogens and tumors. DC development is determined by signaling through the receptor tyrosine kinase Fms-like tyrosine kinase 3 (FLT3) in bone marrow myeloid progenitors. Recently the naming conventions for DC phenotypes have been updated to distinguish between "Conventional" DCs (cDCs) and plasmacytoid DCs (pDCs). Activating mutations of FLT3, including Internal Tandem Duplication (FLT3-ITD), are associated with poor prognosis for acute myeloid leukemia (AML) patients. Having a shared myeloid lineage it can be difficult to distinguish DCs from AML tumor cells. To date, there is little information on the effects of FLT3-ITD in DC biology. To further elucidate this relationship we utilized CITE-seq technology in combination with flow cytometry and multiplex immunoassays to measure changes to DCs in human and mouse tissues. We examined the cDC phenotype and frequency in bone marrow aspirates from patients with AML to understand the changes to cDCs associated with FLT3-ITD. When compared to healthy donor (HD) we found that a subset of FLT3-ITD+ AML patient samples have overrepresented populations of cDCs and disrupted phenotypes. Using a mouse model of FLT3-ITD+ AML, we found that cDCs were increased in percentage and number compared to control wild-type (WT) mice. Single cell RNA-seq identified FLT3-ITD+ cDCs as skewed towards a cDC2 T-bet phenotype, previously shown to promote Th17 T cells. We assessed the phenotypes of CD4 T cells in the AML mice and found significant enrichment of both Treg and Th17 CD4 T cells in the bone marrow and spleen compartments. stimulation of CD4 T cells also showed increased Th17 phenotype in AML mice. Moreover, co-culture of AML mouse-derived DCs and naïve OT-II cells preferentially skewed T cells into a Th17 phenotype. Together, our data suggests that FLT3-ITD+ leukemia-associated cDCs polarize CD4 T cells into Th17 subsets, a population that has been shown to be negatively associated with survival in solid tumor contexts. This illustrates the complex tumor microenvironment of AML and highlights the need for further investigation into the effects of FLT3-ITD mutations on DC phenotypes and their downstream effects on Th polarization.
树突状细胞(DC)是先天免疫和适应性免疫对病原体和肿瘤反应的中介。DC 的发育取决于骨髓髓样前体中受体酪氨酸激酶 Fms 样酪氨酸激酶 3(FLT3)的信号转导。最近,DC 表型的命名约定已更新,以区分“常规”DC(cDC)和浆细胞样 DC(pDC)。FLT3 的激活突变,包括内部串联重复(FLT3-ITD),与急性髓系白血病(AML)患者的预后不良相关。由于具有共同的髓系谱系,因此很难将 DC 与 AML 肿瘤细胞区分开来。迄今为止,关于 FLT3-ITD 对 DC 生物学的影响的信息很少。为了进一步阐明这种关系,我们利用 CITE-seq 技术结合流式细胞术和多重免疫测定法,测量人类和小鼠组织中 DC 的变化。我们检查了来自 AML 患者的骨髓抽吸物中的 cDC 表型和频率,以了解与 FLT3-ITD 相关的 cDC 变化。与健康供体(HD)相比,我们发现一部分 FLT3-ITD+AML 患者样本中 cDC 的代表性群体和表型发生了破坏。使用 FLT3-ITD+AML 的小鼠模型,我们发现与对照野生型(WT)小鼠相比,cDC 的百分比和数量增加。单细胞 RNA-seq 鉴定出 FLT3-ITD+cDC 偏向于 cDC2 T-bet 表型,先前已证明该表型可促进 Th17 T 细胞。我们评估了 AML 小鼠中 CD4 T 细胞的表型,发现骨髓和脾脏中 CD4 T 细胞的 Treg 和 Th17 均明显富集。AML 小鼠中 CD4 T 细胞的刺激也显示出 Th17 表型增加。此外,AML 小鼠来源的 DC 和幼稚 OT-II 细胞的共培养优先将 T 细胞偏向 Th17 表型。总的来说,我们的数据表明,FLT3-ITD+白血病相关 cDC 将 CD4 T 细胞极化为 Th17 亚群,先前已证明该亚群与实体瘤环境中的生存呈负相关。这说明了 AML 的复杂肿瘤微环境,并强调了需要进一步研究 FLT3-ITD 突变对 DC 表型的影响及其对 Th 极化的下游影响。