OCT-1 Protein Expression Detected by Flow Cytometry Provided Valuable Information in CML Patients Treated with Imatinib MesylateÃ, FHigher hOCT-1 Expression Predict Better Outcome.

The human organic cation transporter-1(hOCT-1) is the major active influx protein responsible for the transport of imatinib into cells. The functional activity of the hOCT-1 protein using ^14-C detected by others demonstrated a link between CML molecular response and hOCT-1 activity. However, ^14-C labeled detection is not convenient in routine clinical practice. Hence, we use flow cytometry to detect hOCT-1 protein expression level in CML patient and try to find some relation between hOCT-1 expression and imatinib response.

In this study, 64 CML CP patients and 31 healthy donors were enrolled. Totally, there are 78 patient' peripheral blood (PB) or bone marrow (BM) samples and 31 donor PB samples were measured. The hOCT-1 protein expression levels were detected by indirect immunofluorescent flow cytometry. The hOCT-1 levels were expressed as mean fluorescent intensity (MFI). In avoided to systematic error, lymphocytes which had little hOCT-1 expression were used as internal negative control.

‡@ Assessing PB hOCT-1 expressing in patients with donors, hOCT-1 level is higher in healthy donors than in CML patient (mean±standard deviation 9.11±6.04,5.60±3.74,P=0.005). ‡AThe hOCT-1 level was compared with molecular response in patients. Of 39 patients achieved optimal molecular response, the hOCT-1 level was 6.49±3.83, versus 3.86±2.91 in 20 patients with non-optimal response(P=0.009). Comparing 39 optimal responders with 16 sub-optimal responders, hOCT-1 level were 6.49±3.83, versus 3.98±1.23(P=0.025. ‡B Assessing CML stages with hOCT-1 expression, there is no significant difference in chronic stage and advanced stage(5.93±3.87, 3.49±1.64, P=0.085).

hOCT-1 expression level measured by flow cytometry is very convenient and clinically available. The hOCT-1 expression level can be an important predictor in CML patients treated with imatinib mesylate.

No relevant conflicts of interest to declare.