Linc-ROR Expression in Acute Lymphoblastic Leukemia

Background and Aim: Acute lymphoblastic leukemia (ALL) is commonin children and characterized by the overproduction of immaturelymphocytes in bone marrow (BM). Emerging data demonstrate thatlong non-coding RNAs (lncRNA) are involved in pathological processeslike cancer. LINC-ROR plays a role in the endogenous maintenance of stem cells and participated in tumorigenesis by acting as p53 repressor,hypoxia-responsive lncRNA. Also, Leukemic cells in BM have shownan overexpression of hypoxia-inducible factor (HIF-1α). The aim of thisstudy was to examine Linc-ROR expression in ALL cell lines, patients andHypoxia condition.Methods: We cultured T-ALL including RPMI-8402 and Jurkat in RPMI-1640 supplemented with 10% heat-inactivated fetal bovine serum (FBS)at 37˚C in a humidified incubator containing 5% CO2. Cell lines werepurchased from the National Cell Bank of Iran (NCBI) (Pasteur Instituteof Iran, Tehran). For hypoxia condition cell lines were cultured in 10-cmdishes for 24 hours at 37°C in an incubator; gassed with a pre-analyzedgas mixture containing 5% CO2 and 95% N2. BM Mononuclear cells ofpatients were isolated from ficoll-opaque. As control T lymphocyte wasisolated by nylon wool from healthy BM -nylon fibers were obtainedfrom the Iranian Blood Transfusion Organization (IBTO, Tehran, Iran).The purity of isolated T lymphocytes was evaluated using flow cytometry,Cells were incubated with PE-conjugated Anti-human CD3 for 45minutes at 4°C in dark. Expression of LINC-ROR, P53, and HIF-1α incell lines, hypoxia, and Patients by quantitative real-time PCR. β-Actinwas used for normalization. Relative gene expression was calculatedaccording to the 2-ΔΔCT/ΔCT method.Results: Our results revealed that expression of LINC-ROR was lowerin Jurkat and RPMI-8402 compared to T cell Also, P53 expression wasincreased significantly in Jurkat and RPMI-8402 compared to control.Patient samples evaluation showed that expression of LINC-ROR wasdecreased in contrast to p53, which its expression pattern is the same ascell lines. Expression of LINC-ROR was significantly increased in bothcell lines and P53 expression was decreased under hypoxia conditioncompared to normoxia condition. We evaluated the expression of HIF-1αand we observed expression of HIF-1α was higher in the patient samplescompared to healthy patients. In addition, HIF-1α expression wasconsiderably elevated under hypoxia condition compared to control.Conclusion: Our data demonstrated, have a tight correlation betweenLINC-ROR and p53. linc-ROR Expression under hypoxia was increasedthat lead to inhibit important tumor suppressor, p53 that leads to leukemiccell growth. In addition, LINC-ROR can induce HIF-1α expression underhypoxia and it contributes to chemotherapy resistance of leukemic cells.Our findings accompanied by the previous study reveal that LINCRORmay have a role in ALL progression especially, during hypoxia.We hypothesize that LINCROR may have a key function in a T-ALLpathogenesis and it would be a new biomarker for prognostic factor.

Keywords:

Acute lymphoblastic leukemia , Long noncoding RNA , LINCROR