[Detection of activating mutations in RAS/RAF/MEK/ERK and JAK/STAT signaling pathways]

The study of activating mutations (NRAS,KRAS,FLT3,JAK2,CRLF2genes) of RAS/RAF/MEK/ERK and JAK/STAT signaling pathways in B-cell acute lymphoblastic leukemia (B-ALL) in adult patients which are included in Russian multicenter clinical trials.

Within the multicenter study there were 119 adult patients included withde novoB-ALL. The study was considered as prospective and retrospective. The group withBCR-ABL1-negative B-ALL consisted of up to 93 patients (45 male and 48 female, at the age of 17 to 59, the median age 31), they were treated according to the protocols ALL-2009, ALL-2016. The median follow-up lasted for 19 months (1119). The group withBCR-ABL1-positive B-ALL with up to 26 patients (10 male and 16 female, at the age of 23 to 78, the median age 34 years) was included in the study as well. The treatment was carried out according to the protocols ALL-2009 and ALL-2012 in combination with tyrosine kinase inhibitors. The median follow-up lasted for 23 months (4120). The molecular analysis of activating mutations inNRAS,KRASgenes (RAS/RAF/MEK/ERK signaling pathway) andJAK2,CRLF2genes (JAK/STAT signaling cascade) was performed via Sanger sequencing. The internal tandem duplications (ITDs) inFLT3gene were studied by fragment analysis. The evaluation of CRLF2 expression was fulfilled via flow cytometry.

Activating mutations inNRAS,KRAS,FLT3genes were found in 22 (23.6%) patients withBCR-ABL1-negative B-ALL. In total, 23 mutations were revealed in theNRAS(n=9),KRAS(n=12), andFLT3(n=2) genes, according to statistics that was significantly more frequent than withBCR-ABL1-positive B-ALL, these genes mutations were not identified in patients (p=0.007). The frequency of mutations detection inKRASandNRASgenes in patients withBCR-ABL1-negative B-ALL was comparable as 12.9% (12 of 93) to 9.7% (9 of 93), respectively (p=0.488). One patient was simultaneously revealed 2 mutations in theKRASgene (in codons 13 and 61).FLT3-ITD mutations were detected in 3.5% (2 of 57) cases ofBCR-ABL1-negative B-ALL. In patients withBCR-ABL1-positive B-ALLFLT3-ITD mutations were not assessed. Violations in the JAK/STAT signaling cascade were detected in 4 (4.3%) patients withBCR-ABL1-negative B-ALL. They were represented by the missense mutations ofJAK2gene (n=3) and the overexpression of CRLF2 (n=2); in one patient were detected the overexpression of CRLF2 and a mutation inJAK2gene simultaneously. No mutations were found inCRLF2gene. In patients withBCR-ABL1-positive B-ALL noJAK2mutations were detected. As long as analyzing demographic and clinical laboratory parameters between groups of patients with and without mutations, there were no statistically significant differences obtained. In the analyzed groups of patients, long-term therapy results did not differentiate according to the mutations presence inNRAS,KRAS,FLT3,JAK2genes. Also, substantive differences were not shown in the rate of the negative status achievement of the minimum residual disease between patients with and without activating mutations in the control points of the protocol (on the 70th, 133rd and 190th days).

NRAS,KRAS,FLT3,JAK2activating mutations do not affect the long-term results of the therapy and the rate of the negative status achievement of the minimum residual disease in patients withBCR-ABL1-negative B-ALL treated by the Russian multicenter clinical trials.