Background: In chronic lymphocytic leukemia (CLL), in vivo apoptotic resistance of malignant B lymphocytes results, in part, from the intrinsic defects of their apoptotic machinery. These include genetic alterations and aberrant expression of many apoptosis regulators, among which the Bcl2 family members play a central role.
Aim: The aim of this study was to investigate the association of pro-apoptotic Bax gene expression and Bcl2/Bax ratio with the clinical features of CLL patients as well as with molecular prognostic markers, namely the mutational status of rearranged immunoglobulin heavy variable (IGHV) genes and lipoprotein lipase (LPL) gene expression.
Methods: We analyzed the expression of Bax mRNA and Bcl2/Bax mRNA ratio in the peripheral blood mononuclear cells of 58 unselected CLL patients and 10 healthy controls by the quantitative reverse-transcriptase polymerase chain reaction.
Results: We detected significant Bax gene overexpression in CLL samples compared to non-leukemic samples (p=0.003), as well as an elevated Bcl2/Bax ratio (p=<0.001). Regarding the association with prognostic markers, the Bcl2/Bax ratio showed a negative correlation to lymphocyte doubling time (r=-0.307; p=0.0451), while high-level Bax expression was associated with LPL-positive status (p=0.035). Both the expression of Bax and Bcl2/Bax ratio were higher in patients with unmutated vs. mutated IGHV rearrangements, but this difference did not reach statistical significance.
Conclusions: Our results suggest that dysregulated expression of Bcl2 and Bax, which leads to a high Bcl2/Bax ratio in leukemic cells, contributes to the pathogenesis and clinical course of CLL.
Uvod: Rezistencija na apoptozu koja karakteriše maligne B limfocite in vivo u hroničnoj limfocitnoj leukemiji (HLL) delimično je uzrokovana unutrašnjim poreme-ćajima apoptotske mašinerije u ovim ćelijama. Ti poremećaji su rezultat genetičkih promena i aberantne ekspresije regulatora procesa apoptoze, među kojima ključnu ulogu imaju članovi Bcl2 familije.
Cilj: Cilj ove studije je bio da se ispita udruženost nivoa ekspresije proapoptotskog Bax gena, kao i Bcl2/Bax odnosa, sa kliničkim karakteristikama bolesnika sa HLL kao i molekularnim prognostičkim markerima, i to mutacionim statusom rearanži-ranih gena za teške lance imunoglobulina (IGHV) i ekspresijom gena za lipoproteinsku lipazu (LPL).
Metode: Analizirana je ekspresija Bax iRNK i Bcl2/Bax iRNK odnos u mononuklearnim ćelijama periferne krvi 58 bolesnika sa HLL i 10 zdravih kontrola metodom reverzne transkripcije i lančane reakcije polimeraze u realnom vremenu (qRT-PCR).
Rezultati: Detektovana je povišena ekspresija Bax gena u HLL uzorcima u odnosu na kontrolne uzorke (p=0,003), kao i povišen Bcl2/Bax odnos (p=<0,001). Kada je u pitanju udruženost sa prognostičkim markerima, Bcl2/Bax odnos je ispoljio negativnu korelaciju sa vremenom udvostručavanja broja limfocita (r=-0,307; p=0,0451), dok je visoka ekspresija Bax bila povezana sa LPL-pozitivnim statusom (p=0,035). I ekspresija Bax gena i Bcl2/Bax odnos su bili viši kod bolesnika sa nemutiranim u odnosu na bolesnike sa mutiranim IGHV genima, ali nije dostignuta statistička značajnost.
Zaključak: Rezultati ove studije ukazuju na moguću ulogu poremećene ekspresije Bcl2 i Bax gena, koja dovodi do visokog Bcl2/Bax odnosa u leukemijskim ćelijama, u patogenezi i kliničkom toku HLL.
Keywords: Bax; Bcl2/Bax ratio; apoptosis; chronic lymphocytic leukemia; expression analysis.