Evaluation of posttransplant relapse risk in patients with acute leukemia using the gene expression markers
Alena I. Shakirova1, Ildar M. Barkhatov1, Olga I. Shakirova2, Dmitry S. Romanyuk1, Alexei V. Evdokimov1,
Sergey N. Bondarenko1, Ludmila S. Zubarovskaya1, Boris V. Afanasyev1
1 R. M. Gorbacheva Memorial Institute of Children Oncology, Hematology and Transplantation, First St. Petersburg State
I. Pavlov Medical University
2 St. Petersburg State Polytechnic University, St. Petersburg, Russian Federation
It is known that up to 50 percent of cases of acute myeloid leukemia (AML) do not have informative genetic markers. At the same time, the studies of donor chimerism do not fully indicate the degree of tumor cells elimination and not always allows to estimate the risk of post-transplant relapse. Thus, finding of universal markers allowing for adequate therapy in post-transplant period, is quite important. WT1, BAALC, EVI1 and PRAME gene expression analysis is one of the possible approaches is this field.
Patients and methods
Our study included 63 patients with AML (1 to 60 years old) (M0-2pts, M1-11pts, M2-13pts, M3-2pts, M4-21pts, M5-11pts, M6-1pt, M7-2pts ) who underwent allogeneic transplantation of hematopoietic stem cells (allo-HSCT). In 24 patients myeloablative conditioning regimen were used, 39 – received reduced toxicity protocols. Assessing the levels of WT1, BAALC, EVI1, PRAME gene expression and the level of chimeric transcripts was performed by means of RQ-PCR with normalization for ABL gene expression. For the donor chimerism monitoring a panel of STR-markers was used.
As based on gene expression in healthy donors, we have established cut-off overexpression (gene exp. / ABL exp. X100) values for the genes: WT1 – 250, EVI1-10, BAALC – 20, PRAME – 200. For the present patient setting, we found no statistically significant differences in WT1, BAALC, EVI1, PRAME genes expression between the patients with different FAB variants of AML. However we were able to identify a trend to higher values of PRAME and BAALC gene expression in patients with M1 variant, and WT1 gene values among patients with M4 variant of AML. In patients who underwent transplantation in relapse state, we have noted a significant overexpression of EVI1 (p=0,006), WT1 (p<0,001), BAALC (p<0,001). A similar trend was observed for PRAME gene (p=0,08). EVI1 gene overexpression was revealed for 6 patients (33%), WT1 in 13 cases (72%), BAALC in 10 patients (55%) and PRAME in 4 patients (22%). When comparing the data on chimeric transcripts expression, we detected a correlation between expression levels of the studied genes and chimeric transcripts (PML-RARa and RUNX1-RUNX1T1, p<0,05) as well as with donor chimerism levels. At the same time, we did not find this relationship, when comparing with data about of expression of a CBFB-MYH11 chimeric gene. When evaluating the test sensitivity and specificity analysis we revealed a bellow-cutoff value of the expressed genes in presence of the chimeric transcript less than 2%.
Evaluation of universal gene marker expression is an attractive approach for assessing efficiency of therapy in patients with AML. Thus, their use in early diagnostics of relapse in post-transplant period is quite promising. However, due to low specificity caused by basal expression in normal cells, futrher application of these markers is limited, when detecting minimal residual disease levels.
Minimal residual disease, acute myeloid leukemia, baalc, wt1, prame, evi1, relapse diagnostics