S100A8 inhibition in leukemic lymphoblasts induces sensitivity to chemotherapy and inhibition of disease relapse.

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children and relapsed B-ALL is the leading cause of mortality in children with leukemia due to a lack of response to treatment. S100A8 is a low molecular weight calcium-binding intracellular protein that is expressed in certain cells, and its increased expression is seen in most tumors as well as in relapsed childhood B-ALL cases. The present study indicates the important role of S100A8 in improving viability and resistance to chemotherapy in relapsed B-ALL lymphoblasts. S100A8 levels were compared in B-ALL and relapsed B-ALL lymphoblasts that were sensitive and resistant to Vincristine, respectively. S100A8 was inhibited in the lymphoblasts of two patients by antisense locked nucleic acid (LNA) GapmeRs and the decreased expression of S100A8 was evaluated using quantitative real-time PCR and ELISA. Then, the S100A8 antisense LNA GapmeRs-transfected cells were treated with Vincristine and the expression levels of S100A8 mRNA and S100A8 protein were re-determined. At all of these stages, cell viability and LC50 were assessed by MTT assay. The results showed that S100A8 levels in relapsed B-ALL lymphoblasts were significantly higher than B-ALL lymphoblasts. Moreover, the increase in S100A8 expression was proportionate to the increase in Vincristine resistance in these cells. The S100A8 knockdown procedure using antisense LNA GapmeRs decreased the cell viability and increased vincristine sensitivity in lymphoblasts of two patients, and it also increased the sensitivity to chemotherapy in relapsed B-ALL lymphoblasts. According to the findings of the present study, S100A8 is effective in developing lymphoblast resistance to chemotherapy, and its enhanced expression may contribute to shifting B-ALL into the relapse phase of the illness. As a result, S100A8 may be a valuable target for managing and improving relapses B-ALL.