Quantitative Detection Of Minimal Residual Leukemia Cells In Peripheral Blood And Clinical Application

Current chemotherapy treatment and hemopoiesic stem cell transplantation of acute leukemia leads to cure in the majority of patients with the disease.It seems certain,however,that some patients eventually relapse after induction of remission,usually due to presence of minimal residual leukemia cells.Minimal residual leukemia is one of the main factors which indicate remission, prognosis and relapse.It has important clinical significance of guiding treatment,evaluating therapy,predicting outcome and detecting relapse to use common gene marker in leukemia cells and to establish a feasible method for quantitative detection of minimal residual leukemia cells. The method for detecting minimal residual leukemia cells should have high sensitivity. Polymerase chain reaction is being the most chief method for detecting minimal residual leukemia, because of the advantages of quickness, sensitivity, simplicity and peculiarity. It is limited to predict relapse if merely detecting the existance of minimal residual leukemia cells. However, quantitative analysis of minimal residual leukemia cells helps to carry out individualization of treatment and improve the value of predict relapse through continous observation to the level change. Limiting dilution quantitative assay has the advantages of simplicity, effectiveness and high sensitivity, it could reflect the change of leukemia cells number. Thus, limiting dilution quantitative PCR is selected as the method for detecting minimal residual leukemia cells in acute leukemia. Another key to detect minimal residual leukemia cells is to determine leukemia-specific gene marker. It is important to select common gene marker in different leukemia cells for diagnosing and monitoring minimal residual leukemia. Flt3 gene has high expression rate in acute leukemia, including in acute myelogenous leukemia and in acute lymphoblastic leukemia. The high level of Flt3 gene in primary leukemia blasts would gradually decreased with complete remission. Thus, Flt3 gene is determined to detect minimal residual leukemia as common symbolic gene. Using Flt3 as gene marker, and PCR amplification of quantitative method of limited dilution, the Flt3 gene was detected in blast cells of peripheral blood from 25 newly diagnosed cases of acute leukemia. The sensitivity was 10 copies. Our results show that: ①The positive rate of Flt3 gene in acute leukemia sample was 80% (20/25). 15(88.2%) of 17 AML, 5 (62.5%) of 8 ALL was detected. ②Quantitative detection for leukemia blasts was approached in 20 cases of acute leukemia which Flt3 gene detection was positive. The mean DNA content in peripheral blood in newly diagnosed group was (2.36±1.25)×108pg/μl,being equal to (18.66±8.79)×106 leukemia cells in every microliter peripheral blood. After one course of chemotherapy treatment, 1 case in non-remission group, the DNA content in peripheral blood was 1.69×107pg/μl, being equal to 1.01×106 leukemia cells in every microliter peripheral blood.3 cases in partial remission group, the mean DNA content in peripheral blood was (0.57±0.24) ×106pg/μl,being equal to (1.82±0.19)×103 leukemia cells in every microliter peripheral blood. 7 cases in complete remission group which Flt3 detection was positive, the mean...