Downregulating LKB1 in bone marrow mesenchymal stem cells could inhibit CD4+ T cell proliferation via the PD-1/PD-L1 signaling pathway

Background

Our previous research has shown that LKB1 in amniotic mesenchymal stem cells (MSCs) serves as a vital regulator of regulatory T cell differentiation and T cell proliferation, which may have a similar role in bone marrow MSCs (BMMSCs). Therefore, we investigated the role of LKB1 in BMMSCs for regulating CD4⁺ T cell proliferation in the bone micro-environment of AML.

Methods

RT-PCR was used to assessed LKB1 expression in BMMSCs derived from AML patients and healthy controls. Subsequently, LKB1 was knocked down in the BMMSCs line HS-5 (HS-5-LKB1^KD). Co-cultures in vitro were established to analyze the effect of HS-5-LKB1^KD on CD4⁺ T cell. Flow cytometry was employed to measure PD-L1 and CD4⁺ T cell proliferation levels. Western blot was utilized to detect related proteins.

Results

The expression of LKB1 in BMMSCs derived from AML patients was decreased. Knockdown of LKB1 in HS-5 resulted in upregulation of PD-L1 expression. Co-culture of peripheral blood CD4⁺ T cell with HS-5-LKB1^KD exhibited reduced CD4⁺ T cell proliferation compared to co-culture with HS-5-LKB1^con. Furthermore, blocking PD-L1 in the co-culture conditions could restore the reduced CD4⁺ T cell proliferation. Additionally, it was found that upregulation of the Wnt signaling pathway-related proteins following LKB1 knockdown in HS-5, indicating that downregulating LKB1 could promote PD-L1 expression through activation of the Wnt signaling pathway.

Conclusions

The decreased expression of LKB1 in BMMSCs may activate the Wnt signaling pathway, leading to increased PD-L1 expression. This inhibited CD4⁺ T cell proliferation, which might lead to impaired anti-tumor immunity in AML patients and promote AML progression.