Análise do perfil de expressão de genes relacionados à resistência a quimioterápicos na leucemia linfóide aguda da criança e do adolescente

SILVEIRA, V. S. Expression profile of genes related to chemotherapy resistance in childhood acute lymphoblastic leukemia. 2009. 131f. Doctoral Thesis – School of Medicine of Ribeirao Preto, University of São Paulo, Ribeirao Preto, SP, Brazil. Major improvements have been made in the ALL treatment, which achieved successful rates of approximately 80% of long-terms survival. Despite the significant percentage of success, the remaining 20 % still presents treatment failure and the molecular mechanisms involved in the resistance process remains unclear. The present study was undertaken to analyze and validate the gene expression pattern of the previously described genes related to prednisolone (F8A, CDK2AP1, BLVRB, CD69), vincristine (RPLP2, CD44, TCFL5, KCNN1, TRIM24), daunorubicin (MAP3K12, SHOC2, PDCH9, EGR1, KCNN4) and Lasparaginase (GPR56, MAN1A1, CLEC11A, IGFBP7, GATA3) in order to better inderstand these mechanisms. Bone marrow samples of ALL patients, obtained at diagnosis, in four oncology centers and treated according to the Brazilian protocol (GBTLI-99). The relative mRNA expression levels were quantified using real-time PCR analysis. Amplification of the specific sequences was performed with SYBR® Green reagent; GUSB was used as the reference gene and normal bone marrow samples used as calibrator. The expression profile analisis showed important associations among the studied genes and clinical features as WBC count at diagnosis, CALLA, TEL/AML1 translocation and minimal residual disease. Among the analyzed genes, possible therapy targets were found at SHOC2 and GPR56. Further we addressed the expression profile of these genes in ALL patients, treated according to the BFM protocol, which chacarterize a group of distinct genetic’s background. The results confirmed the data previously obtained. The overexpression of the gene SHOC2, that was primaraly associated to sensibility to dauborubicin, was related to patients who presented good prednisone response, suggesting the correlation of SHOC2 with good prognostic factors. In order to acess the interaction level of this gene, the protein expression was analyzed and confirmed the mRNA expression data. Despite its lack of information, the data on SHOC2 shows its role as na important element in the Erk activation by Ras induced pathway. Finally, to better understand the possible mechanisms which involve SHOC2 gene to the chemotherapy response process, Jurkat cells was transfect with siRNA to silence the gene SHOC2. Further, functional assays were done to characterize the mechanisms involved. The results showed the association of SHOC2 gene expression with processes of cell proliferation and apoptosis induction, thus suggesting that the overexpression of SHOC2 could play an important role in leukemic cell’s sensibility to chemotherapy agents, and consequently in patients’ treatment outcome. In conclusion, this work demonstrated the association of the expression profile of many genes with important clinical and laboratorial features. Furthermore, this data present the gene SHOC2 as a possible therapy target to acute lymphoblastic leukemia ‘s treatment.