TGFβ-Mediated Overexpression of Podoplanin Serves as a Potential Diagnostic Biomarker in Acute Promyelocytic Leukemia.

Early diagnosis of acute promyelocytic leukemia (APL), driven by PML-RARA oncoprotein, is vital for survival, as delays can cause fatal coagulopathy without prompt therapeutic intervention of all-trans retinoic acid and arsenic trioxide. Although APL is diagnosed using microscopy, immunophenotyping, and FISH/PCR for PML-RARA, morphological overlap with acute myeloid leukemia (AML) -M5 and AML-M2 complicates identification. In resource-limited settings, unavailability of real time -quantitiative PCR (RQ-PCR) or delays in FISH/qualitative RT-PCR results 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. We evaluated PDPN expression, regulation, and diagnostic potential in APL. PDPN mRNA (RQ-PCR) and surface protein (flow cytometry) were significantly higher in APL than non-APL AML (p < 0.0001), consistent with TCGA-LAML and BEATAML1.0 datasets. Sensitivity and specificity were 80.7% and 71.43% by RQ-PCR, and 92.86% and 100% by flow cytometry, respectively. Chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR) and TGF- β1 stimulation confirmed SMAD binding and PDPN upregulation. Pharmacological inhibition of TGF-β1 ligand using luspatercept reduced SMAD phosphorylation and PDPN expression, indicating TGF-β/SMAD transcriptionally regulates PDPN. Additionally, ELISA-based serum profiling showed significantly elevated TGF-β1 levels in APL patients compared to non-APL AML (p < 0.0001). These findings identify PDPN overexpression as a downstream consequence of TGF-β/SMAD signaling and highlight its potential as a diagnostic biomarker for APL.