Author/Authors :
EI-Sewefy, Dahlia Ain Shams University - Faculty of Medicine - Department of Clinical Pathology, Egypt , Fouad, Dina A Ain Shams University - Faculty of Medicine - Department of Clinical Pathology, Egypt , Khattab, Reem A Ain Shams University - Faculty of Medicine - Department of Clinical Pathology, Egypt , Hamza, Rasha T Ain Shams University - Faculty of Medicine - Department of Pediatrics, Egypt , Abd EI Hamid, Amal Ain Shams University - Faculty of Medicine - Department of Clinical Pathology, Egypt , Abdallah, Khaled O Ain Shams University - Faculty of Medicine - Department of Clinical Pathology, Egypt
Abstract :
p16INK4a (MTS1) and p15INK4b (MTS2) tumor suppressor genes map to 9p21 and counteract the activity of cyclins, CDK (cyclin D - CDK 4/6 complexes) and other regulatory proteins of the cell cycle such as p53 and pRb. Dysregulation of cell cycle control is crucial in the development and progression of acute lymphoblastic leukemia (ALL). This study aimed to detect 9p21 deletion using conventional cytogenetics (CCA) by G-banding coupled with fluorescence in situ hybridization (FISH) using labeled LSI probe. Both techniques were applied on 40 ALL patients (24 children and 16 adults). Conventional cytogenetics yielded successful mitosis in 32/40 (80%) patients, the karyotypic patterns were as fol lows: 6/32 (18.8%) normal pattern, 8/32 (25%) numerical aberrations in the form of hypodiploidy in 2/32 (6.2%) and hyperdiploidy in 6/32 (18.8%) patients. 12/32 (37.5%) revealed structural aberrations in the form of t(1; 19), del (13q14) and del (9p21) as a sole anomaly, each was detected in one patient, the remaining were del (6q) in 3 patients and del (12p) in 2 patients, while 11q23 rearrangement was seen in 4 patients. Moreover, 6/32 (18.8%) patients had complex karyotypes in which t(9;22) was detected in 4/6 (66.7%) patients accompanied by del (9p21) or +8 in one patient and del (9q) in 2 patients, the remaining 2 showed 3q deletion associated with trisomy 21 in one pa- tient withl7p deletion in the other. All patients were successfully reassessed by FISH technique. It revealed positive results for del 9p21 in 12/40 (30%) patients. The number of cells showing 9p21 de- letion ranged from 7% to 49% with cut off value 6%. This study confirmed the superiority of FISH over CCA in detection of particular genetic aberration, especially the cryptic and minute nes, as there were 12 (30%) cases positive for del (9p21) by FISH analysis using LSI, compared to only two (5%) cases by CCA. All patients were followed up for 12-18 months, revealed that only 1 case (8.3%) that presented with heterozygous deletion of 9p21, achieved CR, may be explained by that, the deletion of genetic material from one allele with preservation of a normal coding sequence on the remaining allele conferred a similar prognosis to cases without deletions. On the other hand, the remmning 11 cases (83.3%) accompanied by either homozygous deletion (3 cases) or heterozygous deletion (8) cases, relapsed or died which may be explained by deletion or inactivation of the remaining allele. Moreover, del (9p21) was found to be statistically significant in relation to age, initial total leucocytic count and fate of the patients (p 0.05). As regards other cytogenetic aberrations encountered in this study, hyperdiploidy, del 6q, del 12p were associated with favorable prognosis. In contrast, hypodiploidy, t (1; 19),1 lq23 rearrangement, del 13q14, complex karyotype and 9p21 deletion were associated with inferior outcome. The results of the current study suggest that 9p21 deletion is correlated with leu- kemia transformation and poor prognosis in ALL patients, which may be the target of chemo- therapeutic agents or intensive therapy aiming to improve the outcome
