CD146 MOLECULE EXPRESSION IN B CELLS ACUTE LYMPHOBLASTIC LEUKEMIA (B-ALLs): A FLOW- CYTOMETRIC MARKER FOR AN ACCURATE DIAGNOSTIC WORK-UP

Abstract

Background: B-lineage acute lymphoblastic leukemias (B-ALL) harboring the t(9;22)(q34;q11)/BCR::ABL1rearrangement, represent a category with previously dismal prognosis whose management and outcome dramatically changed thanks to the use of tyrosine kinase inhibitors (TKIs) usage and more recently full chemo-free approaches. The prompt identification of these cases represents an important clinical need.

Objectives: We sought to identify an optimized cytofluorimetric diagnostic panel to predict the presence of Philadelphia chromosome (Ph) in B-ALLs cases by the introduction of CD146 in our multiparametric flow cytometry (MFC) panels. 

Methods: We prospectively evaluated a total of 245 cases of newly diagnosed B-ALLs with a CD146 positivity threshold >10% referred to the Division of Hematology of ‘Sapienza’ University of Rome. We compared results of CD146 expression percentage and its mean fluorescence intensity (MFI) between Ph+ ALLs, Ph-like ALLs and molecularly negative ALLs.

Results: Seventy-nine of the 245 B-ALL cases (32%) did not present mutations at molecular testing, with 144/245 (59%) resulted Ph+ ALL and 19/245 (8%) Ph-like ALLs. Comparing the 3 groups we found that: Ph+ B-ALL were characterized by higher expression percentage of myeloid markers such as CD13, CD33 and CD66c and low expression of CD38; Ph+ B-ALL showed a higher CD146 expression percentage  and MFI when compared with both molecular negative B-ALL and Ph-like ALLs; neither the mean percentage of CD146 expression neither CD146 MFI were statically different between molecular negative B-ALL and Ph-like ALLs.

Conclusions: Our data demonstrate the association between CD146 expression and Ph+ B-ALLs. CD146 along with myeloid markers may help to identify a distinctive immunophenotypic pattern, useful for rapid identification in diagnostic routine of this subtype of B-ALLs that benefits from a specific therapeutic approach.