Detection of BCR-ABL transcripts in acute lymphoblastic leukemia in Indian patients

Prevalence of common fusion transcripts in acute lymphoblastic leukemia: A report of 304 cases

AIM

Information about fusion transcripts in acute lymphoblastic leukemia (ALL) is used to risk-stratify patients, decide on the treatment and to detect minimal residual disease. This study was conducted to determine the frequency of common fusion transcripts BCR-ABL, TEL-AML1, MLL-AF4 and E2A-PBX1 for B-ALL and SIL-TAL1 for T-ALL as seen at a tertiary care center in India.

METHODS

Up to 304 new cases of ALL (271 B-ALL and 33 T-ALL) diagnosed on morphology, cytochemistry and immunophenotyping were studied. All were screened for the common fusion transcripts by RT-PCR.

RESULTS

Both our B- (218/271; 80.4%) and T-ALL (26/33; 78.8%) patients were largely children. In the B-ALL children, BCR-ABL was detected in 26/218 (11.9%), E2A-PBX1 in 13/218 (5.9%), TEL-AML1 in 16/218 (7.3%) and MLL-AF4 in 3/218 (1.4%) patients. Adult B-ALL cases had BCR-ABL in 15/53 (28.3%) and E2A-PBX in 2/53 (3.8%); however, no other fusion transcript was detected. SIL-TAL1 was found in four of 26 pediatric (15%) and zero of 7 adult T-ALL cases.

CONCLUSION

The higher incidence of BCR-ABL and lower incidence of TEL-AML1 in our ALL patients, both in children and adults as compared with the West, suggests that patients in India may be biologically different. This difference may explain at least in part the higher relapse rate and poorer outcome in our B-ALL cases.

High prevalence of BCR-ABL fusion transcripts with poor prognostic impact among adult ALL patients: report from Pakistan

AIM

Philadelphia (Ph) chromosome positive acute lymphoblastic leukemia (ALL) is a common cytogenetic abnormality associated with poor outcome in adults. This preliminary study, in the absence of substantial evidence, reported the prevalence of the BCR-ABL gene fusion in ALL patients by RT-PCR in Pakistan. Moreover, the prognostic significance of BCR-ABL fusion along with other characteristics was also ascertained.

METHODS

One hundred forty six newly diagnosed ALL patients treated at our center between 2005 and 2008 comprised the study group. The patients were treated with a Children and Leukemia Group B induction regimen.

RESULTS

Among these patients, BCR-ABL fusion oncogene was present in 43 of 78 patients (55%). A statistically significant difference in BCR-ABL-positivity within three age groups (<20 years, 20-50 years, >50 years) was observed (P= 0.001). The median age was significantly higher in the BCR-ABL+ group (30 vs 19 years; P= 0.001). BCR-ABL+ patients were also characterized by higher median WBC counts (96,000/µL vs 23,000//µL, P= 0.002). Complete remission was achieved in 74% BCR-ABL- patients and 35% BCR-ABL+ patients (P= 0.001). Only 10% of BCR-ABL- patients achieved continued complete remission (CR). None of the BCR-ABL+ patients maintained a CR further to induction therapy. With the available therapeutic protocol, the presence of a BCR-ABL fusion predicted a lower survival (P= 0.001).

CONCLUSION

A high prevalence of BCR-ABL gene fusion was observed that appeared as a poor prognostic factor. Identification of this genetic entity at diagnosis is crucial for understanding the nature of adult ALL and for deciding optimal treatment.

Significance of MDR1, MRP1, GSTpi and GSTmu mRNA expression in acute lymphoblastic leukemia in Indian patients

Using, semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) in 167 patients of acute lymphoblastic leukemia (ALL) from India at different stages of the disease (presentation 125, remission 33, first relapse nine), MRP1 and GSTpi expression were significantly higher at relapse than presentation (P=0.03 and P=0.01, respectively) and remission (P=0.007 and P=0.003, respectively). MRP1, GSTpi and GSTmu were expressed simultaneously in several samples with significant association of expression levels (P=0.0001). Association with clinicopathological features included higher MDR1 expression with age >15 years (P=0.04) and higher MRP1, GSTpi, GSTmu expression with WBC counts >100x10(9)/l. In 71 patients (age <25 years), inability to achieve CR was associated with a significantly higher MDR1 mRNA expression (P=0.03) indicating a prognostic significance. However, relapse or shorter Event Free Survival was independent of mRNA expression levels of the four genes. In view of the increased mRNA expression of MRP1/GST at the time of relapse and an association with risk factors such as a high WBC count, further studies directed towards investigating the functional aspects of GSH/GST/MRP1 mediated drug transport are warranted.

T-cell receptor gamma and delta gene rearrangements in T-cell acute lymphoblastic leukemia in Indian patients

T-cell acute lymphoblastic leukemia (T-ALL) is a clonal lymphoid malignancy and junctional sequences of rearranged T-cell receptor (TCR) represent the best suitable marker to study clonality in these patients. A sensitive, non-radioactive, and rapid approach of PCR coupled with heteroduplex analysis was used to analyse clonality of TCR gamma and delta gene rearrangements in 26 Indian T-ALL patients. Amongst TCR gamma gene family, VgammaI-Jgamma1.3/2.3 sequences were most utilized (53.9%) while from TCRdelta repertoire Vdelta1-Jdelta1 sequences were preferentially rearranged (23.1%) in these patients. 19.2% of Indian T-ALL patients demonstrated both clonal TCR gamma and delta gene rearrangements along with surface expression of TCRgammadelta. Although the majority of T-ALL patients showed surface expression of TCRalphabeta, the small fraction (19.2%) of TCRgammadelta+ T-ALL represent a distinct subgroup which needs further evaluation.