Inhibition of LINK-A lncRNA overcomes ibrutinib resistance in mantle cell lymphoma by regulating Akt/Bcl2 pathway

Ibrutinib, a bruton tyrosine kinase (BTK) inhibitor which suppresses B-cell receptor signaling, has remarkably improved the outcome of patients with mantle cell lymphoma (MCL). However, approximately 33% of MCL patients have primary Ibrutinib resistance, and acquired Ibrutinib resistance is nearly universal. Long intergenic non coding RNA for kinase activation (LINK-A) exerts oncogenic role in different types of tumors, but the role of LINK-A in intrinsic ibrutinib resistance in MCL is still unclear. Here, LINK-A expression level was first assessed using quantitative Realtime PCR (qPCR) and immunofluorescence analysis in five MCL cell lines. The effect of LINK-A on regulating MCL cells viability and apoptosis was assayed using CCK-8 and TdT-mediated dUTP nick end labeling (TUNEL) assay, respectively. The association of LINK-A with AKT activation and B cell lymphoma 2 (Bcl2)expression was evaluated using qPCR and western blot analysis. We found that LINK-A level was elevated in Ibrutinib-resistant MCL cell lines (Mino, REC-1, MAVER-1, and Granta519) compared to Ibrutinib-sensitive MCL cell lines (Jeko-1). Functionally, LINK-A overexpression in Jeko-1 cells enhanced cell viability and repressed Ibrutinib-induced cell apoptosis. LINK-A knockdown in MAVER-1 cells decreased cell viability and further accelerated Ibrutinib-induced cell apoptosis. LINK-A overexpression enhanced Bcl2 expression in Jeko-1 cells, and Bcl2 inhibition blocked the effect of LINK-A on increasing cell viability in the presence of Ibrutinib. On the contrary, LINK-A knockdown reduced Bcl2 expression in MAVER-1 cells, and Bcl2 overexpression damaged the role of LINK-A inhibition in regulating cell viability. Mechanistically, LINK-A positively regulated the activation of AKT signaling, and inhibition of AKT signaling destroyed LINK-A-induced increased of Bcl2 and resulted in a subsequent suppression of cell viability. Taken together, the current results demonstrate that LINK A inhibition overcomes Ibrutinib resistance in MCL cells by regulating AKT/Bcl2 pathway.