CD26 expression on circulating CD34+/CD38- progenitor population is a specific and reliable tool for the rapid flow cytometric diagnosis of chronic myeloid leukemia-A single-center validation study

Background: Recently, CD26 have been identified as one of the promising and specific marker for the identification of leukemic stem cells (LSCs) in chronic myeloid leukemia (CML).

Methods: This was a prospective, observational validation study. Peripheral blood (PB) samples from suspected cases of CML and other hematolymphoid neoplasm were evaluated for the expression of CD26 on stem cells (SC) (CD45 dim/CD34+/CD38-) fraction by flow cytometry (FCM) using a single tube four-color antibodies cocktail: CD45-V500 /CD26-PE/CD34-PerCPcy5.5/CD38-APC-H7. The diagnosis of CML was confirmed using cytogenetics and/or molecular studies. Additionally, 12 paired PB and bone marrow (BM) samples of CML cases were compared for the proportion of CD26+ LSCs.

Results: Expression of CD26 on the SC fraction was invariably noted in all cases (116/116) of CML, irrespective of the disease phase and transcript type. None of other neoplasm (0/26), including the Ph + ALLs expressed CD26. Proportion of SCs expressing CD26 was variable with a median (range) proportion being 61.3% (7.6%-98.6%). Evaluation of paired PB and BM samples showed similar proportion of CD26 + LSCs (R² : 0.969).

Conclusion: We confirmed that FCM evaluation of CD26 expression in the PB LSCs is a rapid and specific tool for CML diagnosis. Its utility as a marker for residual disease evaluation can also be explored in the future.