Chronic myeloid leukemia (CML) is a haematopoietic stem cell-based malignant disorder. CML is characterized by the presence of the philadelphia chromosome (9; 22), resulting in production of the BCR-ABL fusion protein with a tyrosine kinase activity. First line therapy for CML is Imatinib, a tyrosine kinase inhibitor(TKI) that targets BCR-ABL and improves prognosis for CML. However, the emergence of TKI resistance, largely due to mutation of the ABL kinase domain is a major problem.
Long non-coding RNAs (lncRNAs) are non-coding RNAs that are > 200 nucleotides in length and are involved in several diseases. Aberrant expression of the lncRNA Nuclear paraspeckle assembly transcript 1 (NEAT1) has been linked to many different cancer types. Two isoforms of NEAT1: NEAT1_1 (3.7 kb) and NEAT1_2 (23 kb) originate from the same promoter. In mammalian nuclei the expression of NEAT1_2 results in the formation of nuclear RNA-protein bodies named paraspeckles, wheras NEAT1_1 produces many smaller nuclear microspeckles. The function of NEAT1, microspeckles and paraspeckles still remains largely unknown in BCR-ABL mediated CML and TKI resistance mechanism.
In this study we aimed to evaluate the cytotoxic effect of imatinib in CML cells by altering NEAT1 expression levels and gene expression of NEAT1 targets which are associated with CML progression and TKI resistance mechanism. K562, a human chronic myleoid cell line, was treated with imatinib in a time and dose dependent manner and cytotoxicity and NEAT1 levels were evaluated. In order to modulate NEAT1 expression levels, CRISPR-Cas9 genome editing was also performed in K562 cells.
Our findings showed that increased expression of NEAT1_1/microspeckles effects the imatinib response in K562 cells. One possibility we are investigating is that NEAT1 might target resistance-associated genes downstream of the BCR-ABL pathways that leads to imatinib resistance in CML. These results suggest that NEAT1 may be a therapeutic candidate in CML.