Hypoxia-inducible factor (HIF) performs the function of an oxygen sensor in the cell and the initiator of a metabolic reactions cascade of that allows to adapt to the oxygen lack. Inadequate shifts in the of HIF regulation activity are involved in the metabolic reprogramming common to all carcinogenic mechanisms. An increase in the level of the HIF1α isoform in lymphoproliferative tumors has been repeatedly described, although there are also opposite observations. The HIF1α and HIF2α isoforms functions of the overlap but often play different roles in various physiological and pathological conditions. Deregulation of miR-155 miRNA functions is also involved in carcinogenesis by affecting the proliferation and survival of tumor cells. This pro-oncogenic potential can were determined by an imbalance of HIF1α and HIF2α transcription factors due to selective inhibition of HIF1A mRNA found in some solid tumors. The predominance of the isoform with a more pronounced adaptive effect promotes cell proliferation under conditions of prolonged hypoxia, which is characteristic of inflammatory foci and emerging niches of malignant growth. Simultaneous determination of the level of HIF1α and HIF2A mRNA, as well as the study of their relationship with the miR-155 level in CLL patients, has not been previously performed.

THE AIM OF THIS STUDY

Was to identify the possible involvement of miR-155 in shifts in HIF1A and HIF2A mRNA in blood cells of CLL patients.

MATERIALS AND METHODS

We used samples of venous blood CLL patients and healthy donors, taken to vacutainers with an RNA stabilizer solution assess mRNA expression and to standard EDTA vacutainers for detecting the level of more stable miR-155 microRNA molecules. Isolation of miR-155 was performed by using microcolumns, and reverse transcription was performed using hsa-miR-155-5p specific stem-loop primer.

RESULTS

The mRNA levels of both HIFA isoforms in stabilized venous blood samples were significantly lower in patients with CLL and did not depend on the use of specific therapy. Between miR-155 and HIF1A mRNA, but not with HIF2A, there was a weak inverse correlation (r= –0.51; p=0.03). The expression values of the studied RNAs did not correlate with the level of leukocytes or the clinical stage of the disease. The level of miR-155 microRNA was elevated but statistically significant only in patients before the appointment of therapy.

CONCLUSIONS

For the first time, parallel levels of HIF1A, HIF2A mRNA, and miR-155 expression in venous blood from CLL patients were measured. The results indicate that the phenomenon of selective inhibition of HIF1A mRNA by miR155 microRNA is not a determining factor in the dynamics of HIF1α isoforms at the level of the total populations of venous blood leukocyte cells. At the same time, the data obtained do not exclude the importance of searching for the diagnostic value of the ratio of HIFA and miR-155 mRNA expression in individual subpopulations of leukemia cells as additional markers of individual prognosis for the development of the disease and the effectiveness of therapy.