Hairy cell leukaemia (HCL) is a rare CD20+ B cell malignancy characterised by rare “hairy” B cells and extensive bone marrow (BM) infiltration. Frontline treatment with the purine analogue cladribine (CDA) results in a highly variable response duration. We hypothesised that analysis of the BM tumour microenvironment would identify prognostic biomarkers of response to CDA. HCL BM immunology pre and post CDA treatment and healthy controls were analysed using Digital Spatial Profiling to assess the expression of 57 proteins using an immunology panel. A bioinformatics pipeline was developed to accommodate the more complex experimental design of a spatially resolved study. Treatment with CDA was associated with the reduction in expression of HCL tumour markers (CD20, CD11c) and increased expression of myeloid markers (CD14, CD68, CD66b, ARG1). Expression of HLA-DR, STING, CTLA4, VISTA, OX40L were dysregulated pre- and post-CDA. Duration of response to treatment was associated with greater reduction in tumour burden and infiltration by CD8 T cells into the BM post-CDA. This is the first study to provide a high multiplex analysis of HCL BM microenvironment demonstrating significant immune dysregulation and identify biomarkers of response to CDA. With validation in future studies, prospective application of these biomarkers could allow early identification and increased monitoring in patients at increased relapse risk post CDA.

毛细胞白血病 (HCL) 是一种罕见的 CD20+ B 细胞恶性肿瘤，其特征是罕见的“毛状”B 细胞和广泛的骨髓 (BM) 浸润。嘌呤类似物克拉屈滨 (CDA) 的一线治疗会导致反应持续时间高度可变。我们假设对 BM 肿瘤微环境的分析将确定 CDA 反应的预后生物标志物。使用数字空间分析对 CDA 治疗前后的 HCL BM 免疫学和健康对照进行分析，以使用免疫学面板评估 57 种蛋白质的表达。开发了生物信息学流程，以适应空间解析研究的更复杂的实验设计。 CDA 治疗与 HCL 肿瘤标志物（CD20、CD11c）表达减少和骨髓标志物（CD14、CD68、CD66b、ARG1）表达增加相关。 CDA前后HLA-DR、STING、CTLA4、VISTA、OX40L的表达失调。治疗反应的持续时间与 CDA 后肿瘤负荷的更大减少以及 CD8 T 细胞向 BM 的浸润有关。这是第一项对 HCL BM 微环境进行高度多重分析的研究，证明了显着的免疫失调，并确定了 CDA 反应的生物标志物。通过未来研究的验证，这些生物标志物的前瞻性应用可以对 CDA 后复发风险增加的患者进行早期识别和加强监测。