Leukemic stem cell–niche interaction through CLEC2-podoplanin axis confers drug resistance in acute myeloid leukemia

Background: Acute myeloid leukemia (AML) progression and therapy resistance are strongly influenced by the bone marrow microenvironment (BMME). Although recent genomic studies have advanced our understanding of AML pathogenesis, how leukemic stem cells (LSCs) adapt to and exploit niche interactions remains incompletely defined. Methods: We established an in vivo–selected subline of the human AML cell line KG-1a by serial xenografting into NOD/SCID mice (rKG-1a). Phenotypic, transcriptional, and functional assays, including flow cytometry and cDNA microarray were performed. C-type lectin-like receptor 2 (CLEC2) expression in primary AML LSCs (CD34+CD38-) was assessed in 8 patient samples and these cells were co-cultured with stromal MS5 cells engineered to express podoplanin (Pdpn). Chemosensitivity was evaluated using cytarabine (Ara-C) and venetoclax (VEN). Results: Compared with parental KG-1a, rKG-1a exhibited enhanced engraftment anaggressiveness in vivo despite slower proliferation in vitro. rKG-1a demonstrated downregulation of HLA class II and CD31, and upregulation of CD44, CD51, and CD62L. Microarray analysis identified CLEC2 as a top upregulated surface molecule, validated at both mRNA and protein levels. In patient-derived AML LSCs, CLEC2 expression was heterogeneous but significantly higher than in healthy HSCs. Functionally, CLEC2high LSCs displayed resistance to Ara-C when co-cultured with Pdpn-expressing stroma, whereas CLEC2low LSCs did not. Across 8 cases, CLEC2high status consistently associated with greater protection indices, although absolute CLEC2 intensity did not correlate linearly with chemoprotection. Conclusions: Our findings establish CLEC2-Pdpn signaling as a novel axis of LSC–niche interaction that confers chemoresistance in AML. Targeting this pathway may provide therapeutic opportunities to eradicate resistant LSC subsets.