Potential Role of CD9 and Implication of Motility Process in Pathogenesis of TEL/ALM1-positive ALL Relapses (LAL TEL/ALM1 and CD9).

• Assess of the impact of CD9 expression level on motility assays (migration and adhesion) We have initiated motility assays (fibronectin adhesion experiments and CXCL12 chemoattracted migration tests with modified Boyden chamber technique) using the CD9 positive TEL/AML1-positive cell line REH and the CD9 negative cell line RAJI (wild or transfected with CD9 cDNA). Data will be analyzed in combination with blocking antibodies and chemical antagonist according to the level of CD9 (transcript and protein) and of CXCR4. Protein quantifications will be performed by flow cytometry and Western Blot. Interactions will be explored by confocal microscopy and biological pathways by immunoblot.

Adhesion results will be validated on patient samples of B-ALL.

• Post-transcriptional regulation of CD9 in TEL/AML1-positive ALL To identify miRNAs that are potentially deregulated in TEL/AML1-positive acute lymphoblastic leukaemia and especially to screen for CD9 -targeted miRNAs, we will use a TaqMan ®MicroRNA Arrays approach allowing the simultaneous measurement of about 760 human miRNA.

Small RNA will be extracted from bone marrow samples of twenty childhood B-ALL to screen miRNAs which are differentially expressed between CD9-positive and CD9-negative ALL and further compared with miRNAs which were predicted to target CD9 in databases. Validation of the selection will be performed by single Q-PCR for selected miRNAs using a novel cohort of ten bone marrow samples. Transfection assays and luciferase assays will be further realized to confirm that the differential miRNAs really target and affect CD9 expression .

Inclusion criteria

• patients > 1 year and ≤18 years
• with B-ALL diagnosis
• registered in Rennes for treatment
• written informed consent signed by all patients or their parents or legal guardian

Exclusion criteria

• Refusal to participate
• Inherited cytogenetic abnormalities