Quantification of NG2‐positivity for the precise prediction of KMT2A gene rearrangements in childhood acute leukemia

Abstract

It has long been known that there is a link between neuron glial antigen 2 (NG2) surface expression and KMT2A gene rearrangements in acute leukemia (AL). However, the exact levels of NG2 positivity that predict the presence of KMT2A rearrangement are not known. The current study focuses on a cohort of 505 pediatric AL patients who showed any level of positive NG2 expression (greater than 1% of cells) for whom comprehensive genetic data were available. NG2 expression was measured as either the percentage of positive cells or the number of molecules on the cell surface. KMT2A gene rearrangements were identified by FISH. The fusion partner was detected with RT‐PCR, LDI‐PCR or anchored multiplex PCR followed by high‐throughput sequencing. KMT2A‐positive samples comprised a substantial proportion of the NG2‐positive cohort (180 of 505, 36%), with a total of 19 different types of translocation. Despite its occurrence in other AL genetic subgroups, NG2 expression was significantly increased in AL patients with KMT2A rearrangements in terms of both the cell percentage and number of molecules per cell. The threshold levels (TL) for NG2‐positivity were established by ROC analysis of the whole cohort and separately for children less than 1 years old and older with lymphoblastic (ALL) and myeloid (AML) leukemia. The lowest TL was defined in infants with ALL (7%), while in older children, the threshold was higher (12%). In AML patients, the situation was reversed, with 28% NG2‐positivity in infants and 14% in patients >1 year old. The defined TLs resulted in improved diagnostic performance compared to the conventional thresholds of 10% and 20% for all patient groups.

Molecular Heterogeneity of Pediatric AML with Atypical Promyelocytes Accumulation in Children—A Single Center Experience

“…On the other hand, they exhibited typical features of KMT2A -rearranged AML, such as very bright expression of CD33 and HLA-DR and expression of CD4 and CD56, which have been noted [ 58 ]. NG2 expression, which is considered very specific for aberrations involving KMT2A [ 59 , 60 ], was not found on the tumor cells. Thus, being not typically promyelocytic by immunophenotype, the leukemia described did not represent all characteristic KMT2A -rearrangement antigen profiles as well.…”

Flow cytometry in acute leukemia diagnostics. Guidelines of Russian-Belarusian multicenter group for pediatric leukemia studies

“…• включение комбинаций маркеров, применяемых для мониторинга МОБ. К основным маркерам могут быть добавлены дополнительно антигены, ассоциированные с прогностически важными генетическими аберрациями (например, CD123 при гипердиплоидии [21] или NG2 при перестройках с участием гена KMT2A [22]) или являющиеся потенциальными мишенями для таргетной или иммунобиологической терапии. Используемые антитела для диагностики ОЛЛ у детей представлены в таблице 1.…”

Correlation of the surface expression of thymic stromal lymphopoietin receptor with the presence of CRLF2 gene rearrangements in children with B‐lineage acute lymphoblastic leukemia

“…Analysis of the antigen expression profile of tumor cells by multicolor flow cytometry is an essential part of the contemporary diagnostic work‐up in acute lymphoblastic leukemia (ALL) 1,2 . In addition to routinely distinguishing B‐cell precursor ALL (BCP‐ALL) from T‐lineage ALL and further subclassifying the disease according to immunophenotype, 3 flow cytometry can provide significant information for predicting the presence of clinically relevant genetic aberrations, as many such aberrations display characteristic immunophenotypic signatures 4–10 . These peculiarities of the antigen expression profile are usually suggestive, 6,7 although in some cases they are rather specific 8–10 …”

“…1,2 In addition to routinely distinguishing B-cell precursor ALL (BCP-ALL) from T-lineage ALL and further subclassifying the disease according to immunophenotype, 3 flow cytometry can provide significant information for predicting the presence of clinically relevant genetic aberrations, as many such aberrations display characteristic immunophenotypic signatures. [4][5][6][7][8][9][10] These peculiarities of the antigen expression profile are usually suggestive, 6,7 although in some cases they are rather specific. [8][9][10] BCP-ALL with high expression of the CRLF2 gene is one of the recently described leukemia subtypes.…”

“…[4][5][6][7][8][9][10] These peculiarities of the antigen expression profile are usually suggestive, 6,7 although in some cases they are rather specific. [8][9][10] BCP-ALL with high expression of the CRLF2 gene is one of the recently described leukemia subtypes. 11 Despite its rarity, this group of BCP-ALL is considered to have poor outcomes both in children and in adults.…”