Abstract
CXC chemokine receptor 4 (CXCR4) is the receptor for stromal derived factor (SDF-1 or CXCL12) and plays a crucial role in the homing of leukemia cells within the marrow microenvironment. Adhesion to marrow stromal cells is essential for the survival and proliferation of acute myelogenous leukemia (AML) cells, and protect AML cells from chemotherapy-induced apoptosis. In the same way, heat shock proteins (HSP) act as molecular chaperones and are involved in signalling pathways for cell proliferation and survival. HSP have a role in the modulation of apoptosis and are implicated in the resistance of leukemia cells to therapeutic drugs. The aim of this work was to assess the prognostic impact of CXCR4, adhesion molecules such as Very Late Antigen-4 (VLA-4) and Focal Adhesion Kinase (FAK), and HSP expression (HSP 27, HSP 70, HSP 90). In this study, we retrospectively analysed, by flow cytometry, the “adhesive” phenotype and the HSP expression in AML cells from 36 patients treated between 04/1998 and 03/2002. These patients presented de novo AML, and favourable, intermediate and adverse cytogenetics were observed in 7, 19 and 10 patients respectively. Study of the adhesive phenotype was repeated for 10 patients at time of relapse and compared to adhesive phenotype at diagnosis. The flow cytometry analysis was performed with a FACS Canto: conjugated antibodies were used in combination with anti-CD34-FITC and anti-CD45-APC. Twenty-eight of the 36 patients achieved complete remission (CR) whereas seven patients were refractory to the chemotherapy and one patient died from toxicity during aplasia. Median overall survival (OS) was 19.4 months (95% CI: 0.25–102 months). In univariate analysis, the two main prognostic factors in terms of CR achievement were lower CXCR4 and VLA-4 expression on leukemia cell surface (p = 0.03 and p = 0.05 respectively). Overall survival (OS) was negatively influenced by higher CXCR4 expression (p = 0.01), higher VLA-4 expression (p = 0.01), higher FAK expression (p = 0.04) and higher HSP90 expression (p = 0.04) by leukemia cells at diagnosis. Patients were secondarily distributed in two prognostic groups: - Group A including 26 patients presenting overexpression of 0, 1 or 2 factors within CXCR4, VLA-4, FAK, HSP 90 - Group B including 10 patients with overexpression of 3 or 4 factors.
Group B is associated with significantly shorter OS. In multivariate analysis, FAK overexpression and HSP90 overexpression remained of prognostic value for OS (p = 0.01 and p = 0.03 respectively). Moreover, when comparing the adhesive phenotype for 10 patients between diagnosis and relapse, we noted that CXCR4 and VLA-4 are overexpressed at time of relapse (91% positive cells versus 26% at diagnosis for CXCR4 (p = 0.008), and 88% versus 21% for VLA-4 (p = 0.008)). In conclusion, CXCR4, adhesion molecules and HSP90 are new phenotypic prognostic markers. These data indicate that it should be interesting to determine CXCR4, VLA-4, FAK and HSP 90 in the routine flow cytometry diagnostic of AML in order to establish risk-stratified therapeutic strategies. A prospective study with a larger series of patients may lead to confirm the prognostic value of these markers.
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