[Withdrawal syndrome after tyrosine kinase inhibitors discontinuation in patients with chronic myeloid leukemia].

BACKGROUND: Withdrawal syndrome (WS) a musculoskeletal pain after discontinuation of tyrosine kinase inhibitors (TKI) in patients with chronic myeloid leukemia (CML) has been described in the treatment-free remission (TFR) studies. The pathophysiological mechanisms and predisposing factors of WS have not been well established. AIM: Our aim was to evaluate clinical features and factors associated with WS in the Russian cohort of CML patients who discontinued TKI therapy. MATERIALS AND METHODS: WS was evaluated in total of 183 CML patients with chronic phase and sustained deep molecular response (DMR). WS was defined as a musculoskeletal pain newly observed after TKI cessation or as a worsening of previously observed symptoms. RESULTS: DMR loss free survival at 36 months was 49% and 43% in prospective and retrospective groups respectively (p=0.96) with mеdian (Me) time of observation 33 months (range 1136). WS was observed in 49 (27%) patients: grade 12 was in 45 (92%) patients, grade 3 in 4 (8%) patients. Me time to WS occurrence was 2 months (range 17), Ме duration of WS was 5 months (range 135). WS was resolved in 14 of 15 patients with molecular relapse after 13 months of TKI re-initiation and was decreased in 1 patient. WS was completely resolved in 31 of 34 patients who continued remained in TFR and decreased in 3 patients. WS was resolved spontaneously or with nonsteroidal anti-inflammatory drugs in 14 (45%) and 17 (55%) patients accordingly. Older age (p0.0001), longer duration of TKI therapy (p0.0001) and presence of locomotion system diseases (p=0.022) were observed in patients with WS. No WS was observed in pregnant patients (р0.001). Survival without DMR loss at 12 months after TKI stop was 66 and 42% in patients with and without WS accordingly (р=0.095). CONCLUSION: The rate of WS was 27% that is in a good concordance with the data of the other TFR studies. A longer period of TKI exposure, older age and the history of locomotion system diseases were associated with the development of the WS. We found for the first time that WS was not observed in patients with pregnancy. There was no association of WS development and the rate of molecular relapses.

Multipotent Mesenchymal Stromal Cells in Patients with Chronic Myeloid Leukemia before Discontinuation of Tyrosine Kinase Inhibitors.

We analyzed changes in multipotent mesenchymal stromal cells of patients with chronic myeloid leukemia before discontinuation of tyrosine kinase inhibitors. Withdrawal syndrome was significantly more common in patients who have been taking tyrosine kinase inhibitors for a longer time and in patients of older age and with lower body weight. In patients with withdrawal syndrome, the total production of mesenchymal stromal cells and expression of FGFR2 and MMP2 genes were significantly lower; loss of deep molecular response was also less frequent in this group of patients. At the same time, the expression of genes important for the maintenance of stem cells (SOX9, PDGFRa, and LIF) was significantly lower in the mesenchymal stromal cells of patients with withdrawal syndrome and loss of deep molecular response. We observed a clear-cut relationship between the development of withdrawal syndrome and the loss of deep molecular response. The decrease in the expression of FGFR2 and MMP2 genes in the mesenchymal stromal cells of patients with chronic myeloid leukemia before discontinuation of treatment can be a predictor of withdrawal syndrome, while simultaneous decrease in the expression of SOX9, PDGFRa, and LIF in these cells attests to undesirability of therapy discontinuation at the moment.

[Results of following up patients with chronic myeloid leukemia and a deep molecular response without tyrosine kinase inhibitor therapy]. / Rezul'taty nabliudeniia bol'nykh khronicheskim mieloleikozom s glubokim molekuliarnym otvetom bez terapii ingibitorami tirozinkinaz.

AIM: To assess the results of following up patients with chronic myeloid leukemia (CML) and a deep molecular response (MR) without tyrosine kinase inhibitor (TKI) therapy. SUBJECTS AND METHODS: The reasons for TKI discontinuation in 70 patients with CML and a deep MR of more than 1 year's duration were adverse events, pregnancy, and patients' decision. Information was collected retrospectively and prospectively in 2008-2016. RESULTS: The median follow-up after TKI therapy discontinuation was 23 months (2 to 100 months). At 6, 12 and 24 months after TKI therapy discontinuation, the cumulative incidence of major MR (MMR) loss was 28, 41 and 48%, respectively; the survival rates without TKI therapy were 69, 50, and 39%, respectively. MMR loss was noted in 28 (88%) patients at 12 months; it was not seen without TKI therapy at 2-year follow-up. Deaths due to CML progression were absent. The Sokal risk group was a reliable factor influencing MMR loss (p ≤ 0.05). The cumulative recovery rate for deep MR after resumption of TKI use was 73 and 100% at 12 and 24 months, respectively, with a median follow-up of 24 months (1 to 116 months). Deep MR recovered at a later time when the therapy was resumed more than 30 days after MMR loss. CONCLUSION: Safe follow-up is possible in about 50% of the patients with CML and stable deep MRs without TKI therapy. The introduction of this approach into clinical practice requires regular molecular genetic monitoring and organizational activities. Biological factors in maintaining remission after TKI discontinuation need to be separately studied.

[Nucleotide composition and digestion by nucleases of RNA from muscle amylose isomerase]. / Nukleotidnyi sostav i rasshchepliaemost' nukleazami RNK, vydelennoi iz izomerazy amilozy myshts.

The primary structure of homogeneous low molecular RNA preparation with the sedimentation coefficient 2.5S isolated from amilose isomerase (A1) of muscle (E.C. 2.4.1.18) was analysed. This RNA can be digested by venom phosphodiesterase as well as by pancreatic and T2 RNAases; hence we conclude that the polynucleotide chain of A1 RNA consists of 3.5-phosphodiester bonds common for all RNAs. The nucleotide composition of the RNA was studied by two-dimensional TLC followed by spectrophotometry. The results show that its chain is 31--32 nucleotides long. High content of unusual components (about 30%) and guanine (about 40%) are specific features of this RNA.

[Isolation and properties of preparations the branching enzyme of muscles, amylose isomerase]. / Vydelenie i svoistva preparatov vetviashchego fermenta myshts izomerazy amilozy.

The paper describes a modified method of isolating the branching enzyme of amylose isomerase from muscles and a study of the enzyme activity at different stages of purification. By enzyme fractionation on biogel R-150 and Sepharose 6B the fractions containing different RNA amounts have been isolated. The activity of fractions has been shown to depend on their content of RNA. The paper presents a procedure used to isolate a highly purified fraction of amylose isomerase and its properties (pH and temperature optima, enzyme optimal concentration and Michaelis constant).

[An active 2.5S RNA-polysaccharide complex]. / Aktivnyi kompleks 2.5S RNK-polisakharid.

The information on the initial step of enzymatic reaction of 2.5S RNA isolated from muscle 1,4-alpha-glucane branching enzyme (EC 2.4.1.18), isomerase amylose, has been reported for the first time. The 2.5S RNA-polysaccharide (starch) complex was isolated and partly characterized. It was shown that the complex retains its integrity during precipitation with ethanol, gel-filtration on a Biogel P-150 column and electrophoresis but dissociates into RNA and starch upon fractionation on a DEAE-52 cellulose column. Treatment of the original preparation with RNAase fully reflects the complex formation: with a decrease in the RNA content in the original preparation that of the synthesized complex diminishes. The RNA-polysaccharide complex exhibits the properties of the branching enzyme; its enzymatic activity markedly exceeds that of the free RNA.

Primary structure of the nucleic acid from the 1,4-alpha-glucan branching enzyme.

The primary structure of the nucleic acid from the branching enzyme 1,4-alpha-D-glucan: 1,4-alpha-D-glucan 6-alpha-(1,4-alpha-glucano)-transferase (2.5-S RNA) isolated from rabbit muscles has been elucidated. The polyribonucleotide consists of 31 nucleotides; the unique features of the polyribonucleotide are the unusually high content of modified nucleotides (32%) and guanine residues (40%). Apparently 2.5-S RNA belongs to a class of nucleic acids unknown up to now. It is the first time that the structure of a nucleic acid component from a ribonucleoenzyme has been defined. This work is a preprequisite for gaining insight into the intimate activating effect of the poly-ribonucleotide on the enzyme action.