TGFβ-mediated overexpression of podoplanin serves as a potential diagnostic biomarker in acute promyelocytic leukemia.

Abstract

264 Background: Early diagnosis of acute promyelocytic leukemia (APL), driven by PMLRARA oncoprotein, is vital for survival, as delays can cause fatal coagulopathy without prompt all-trans retinoic acid and arsenic trioxide therapy. Although APL is diagnosed using microscopy, immunophenotyping, and FISH/PCR for PML-RARA, morphological overlap with AML-M5 and AML-M2 complicates identification. In resource-limited settings, unavailability or delays in FISH/PCR increase the risk of missed or late diagnosis with fatal outcomes. Podoplanin (PDPN), a glycoprotein overexpressed in APL cells, interacts with platelets to mediate thrombosis. Methods: We evaluated PDPN expression using RQ-PCR and flow cytometry in APL versus non-APL AML samples, validated with TCGA-LAML and BEATAML1.0 datasets. Transcriptional regulation was investigated through in silico promoter analysis and validated through chromatin immunoprecipitation (ChIP-qPCR), TGF-β1 stimulation, and pharmacological inhibition using luspatercept. Serum TGF-β1 levels were measured by ELISA. Results: PDPN mRNA and surface protein were significantly higher in APL than non-APL AML (p<0.0001). Diagnostic sensitivity and specificity were 80.7% and 71.43% by RQ-PCR, and 92.86% and 100% by flow cytometry, respectively. ChIP-qPCR confirmed SMAD binding to PDPN promoter, and TGF-β1 stimulation upregulated PDPN expression. Luspatercept reduced SMAD phosphorylation and PDPN expression, indicating TGF-β/SMAD transcriptionally regulates PDPN. APL patients exhibited significantly elevated serum TGF-β1 levels compared to non-APL AML (p<0.0001). Conclusions: PDPN overexpression results from TGF-β/SMAD signaling and represents a promising diagnostic biomarker for APL, particularly valuable where molecular testing is unavailable or delayed. Keywords: Acute Promyelocytic Leukemia (APL), Coagulopathy, Podoplanin, RQPCR, Flow cytometry, TGF-β.