In proliferating normal and tumor cells, the telomere length (TL) is maintained by high telomerase activity (TA). In the absence of TA the TL maintenance involves a mechanism of alternative lengthening of telomeres (ALT). The aim of this study was to investigate the level of TA, the mTert expression and TL in cultured normal and transformed by γ- and γ,n-irradiation mesenchymal stem cells (MSCs) from mouse bone marrow, in sarcomas that developed after the transplantation of these cells into syngeneic mice, and in fibrosarcoma cell lines obtained from these tumors to find out the role of AT or ALT in maintaining TL in these cells. During prolonged cultivation of normal and transformed under the influence of γ- (1 Gy and 6 Gy) and γ,n-irradiation (0.05 Gy, 0.5 Gy, and 2 Gy) MSCs from mouse bone marrow, a decrease in TA was detected in irradiated cells. Even deeper decrease in TA was found in sarcomas developed after administration of transformed MSCs to syngeneic mice and in fibrosarcoma cell lines isolated from these tumors in which TA was either absent or was found to be at a very low level. TL in three of the four lines obtained was halved compared to the initial MSCs. With absent or low TA and reduced TL, the cells of all the obtained fibrosarcoma lines successfully proliferated without signs of a change in survival. The mechanism of telomere maintainance in fibrosarcoma cell lines in the absence of TA needs further investigation and it can be assumed that it is associated with the use of the ALT. The detected decrease or absence of TA in transformed under the action of irradiation MSCs with the preservation or even an increase in the telomerase gene expression may be associated with the formation of inactive splicing variants, and requires further study. The obtained lines of transformed MSCs and fibrosarcomas with TA and without the activity of this enzyme can be a useful model for studying the efficacy of TA and ALT inhibitors in vitro and in vivo.
V proliferiruiushchikh normal'nykh i opukholevykh kletkakh sokhranenie dliny telomer (DT) obespechivaet vysokaia aktivnost' telomerazy (AT). V otsutstvii AT sokhranenie DT vozmozhno pri ispol'zovanii mekhanizma al'ternativnogo udlineniia telomer (AUT). Dlia vyiasneniia roli AT ili AUT v podderzhanii DT v dannoĭ rabote issledovali AT, ékspressiiu gena kataliticheskoĭ sub"edinitsy telomerazy myshi mTert i DT v kul'tiviruemykh normal'nykh i transformirovannykh pod deĭstviem γ- i γ,n-izlucheniia mezenkhimal'nykh stvolovykh kletkakh (MSK) iz kostnogo mozga myshi, v sarkomakh, razvivshikhsia pri vvedenii obluchennykh MSK singennym mysham, a takzhe v poluchennykh iz étikh opukholeĭ liniiakh fibrosarkom. Pri dlitel'nom kul'tivirovanii normal'nykh i transformirovannykh pod deĭstviem γ- (1 Gr i 6 Gr) i γ,n-izlucheniia (0,05 Gr; 0,5 Gr i 2 Gr) MSK iz kostnogo mozga myshi obnaruzheno snizhenie AT v obluchennykh kletkakh. Eshche bolee glubokoe snizhenie AT obnaruzheno v sarkomakh, razvivshikhsia pri vvedenii transformirovannykh MSK singennym mysham, i v liniiakh kletok fibrosarkom, vydelennykh iz étikh opukholeĭ, v kotorykh AT libo otsutstvovala, libo obnaruzhivalas' na ochen' nizkom urovne. V trekh iz chetyrekh poluchennykh liniĭ DT byla snizhena v dva raza po sravneniiu s iskhodnymi MSK. Pri otsutstvuiushcheĭ ili nizkoĭ AT i snizhennoĭ DT kletki vsekh poluchennykh liniĭ fibrosarkom uspeshno proliferirovali bez priznakov izmeneniia vyzhivaemosti. Mekhanizm podderzhaniia DT v liniiakh kletok fibrosarkom s otsutstviem AT, vozmozhno, sviazan s ispol'zovaniem puti AUT. Obnaruzhennoe snizhenie ili otsutstvie AT v transformirovannykh pri deĭstvii oblucheniia MSK pri sokhranenii ili dazhe povyshenii urovnia ékspressii gena telomerazy mozhet byt' sviazano s obrazovaniem neaktivnykh splaĭs-variantov. Poluchennye linii transformirovannykh MSK i fibrosarkom s AT i bez aktivnosti étogo fermenta predstavliaiut udobnuiu model' dlia issledovaniia éffektivnosti ingibitorov AT i AUT in vitro i in vivo.
Keywords: alternative lengthening of the telomeres; gene expression; mesenchymal stem cells; sarcoma; telomerase; telomeres.