Abstract B37: hnRNP K in acute promyelocytic leukemia cells NB4 and NB4-R2: Involvement in cell survival and differentiation

Abstract

Abstract hnRNP K has been reported to be overexpressed in myeloid leukemia and it is downregulated during all-trans retinoic acid (ATRA) induced differentiation of Acute Promyelocytic Leukemia (APL) cells. The aim of the present study was to establish role of hnRNP K in APL using responsive (NB4) and resistant (NB4-R2) cells to the all-trans retinoic acid treatment as well as the possible role of hnRNPK in ATRA-induced cellular differentiation. After demonstration, by Western blotting analysis, that hnRNP K is overexpressed (10 fold) in APL (NB4 and NB4-R2) cell lines compared to controls (bone marrow and polymorphonuclear cells), we knocked-down the protein by short hairpin RNA (shRNA) interference in these cell lines and assessed involvement of hnRNP K in ATRA-induced differentiation, by flow cytometry in cells incubated with Cd11bPE antibody, as well as the contribution of hnRNP K to proliferation, with growth curve, using Trypan Blue, and survival, by propidium iodide incorporation analysis in flow cytometer. The knockdown of hnRNP K in NB4 (72%) and NB4-R2 (60%) leads to loss of viability mainly in NB4-R2 (42,43% of viability) vs NB4 (75,33% of viability). The loss of viability was more accentuated after ATRA treatment, NB4-R2 (6,13% of viability) vs NB4 (70% of viability). hnRNP K knockdown increases APL cells differentiation and was more accentuated in association with ATRA treatment, NB4-R2 (+59,13%) vs NB4 ( +14,06%). Furthermore, knockdown of hnRNP K leads to decreased in proliferation in NB4 (-95,98%) and NB4-R2 (-97,5%). hnRNP K knockdown promotes decrease of Bcl-xl, PML-RARα, procaspase-3 and increases of SET protein levels in both cells, demonstrated by Western blotting. The extracellular signal-regulated kinase ERK is a positive hnRNP K regulator, so the treatment with the ERK inhibitor at 10 μM U0126 produces effects similar to hnRNP K knockdown on cell viability in NB4-R2 cells, and in levels of BCL-xl and SET proteins. We concluded that, hnRNP K knockdown decreases the cell proliferation and viability of NB4 and NB4-R2 cells and increases cell differentiation, via MEK-ERK-hnRNP K-SET signaling. hnRNP K represent a potential target in APL ATRA resistant cells. Citation Format: Karina Stringhetta Padovani, María Sol Brassesco Annichini, Eduardo Magalhães Rego, Carlos Curti, Lewis Joel Greene, Andréia Machado Leopoldino. hnRNP K in acute promyelocytic leukemia cells NB4 and NB4-R2: Involvement in cell survival and differentiation. [abstract]. In: Proceedings of the AACR Special Conference: Developmental Biology and Cancer; Nov 30-Dec 3, 2015; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(4_Suppl):Abstract nr B37.