Does TAL-1 Deletion Contribute to the High Incidence of T-Cell Acute Lymphoblastic Leukemia in South Indian Patients?

Background: The incidence of T-cell acute lymphoblastic leukemia (T-ALL) in South India is very high(43.1%) when compared to the Western countries (10-20%). TAL-1 deletion is the most common geneticabnormality in T-ALL.
Objectives: The present study was aimed to detect the incidence of type 1 and type 2TAL-1 deletions and assess whether they might contribute to the high incidence of T-ALL in South India. Materialsand
Methods: 45 cases of T-ALL (pediatric-32, adolescents-7 and young adults-6) were studied by DNA-PCRand sequencing. Age of the patients ranged from 3 yrs to 29 yrs (median age 14 yrs).
Results: TAL-1 deletiontype 1 was detected in 6 (13.3%) cases (3 pediatric and 3 adolescents) and all were males. TAL-1 deletion type 2was not present. Comparing the clinical features and immunological marker analysis of TAL-1 deletion positiveand negative cases did not show any significant differences except in the WBC count, which was significantlyhigher in cases showing TAL-1 deletion (>100 x 109/L, p value= 0.003). All the positive cases of TAL-1 deletionwere confirmed by sequencing, the results showing that the fusion region at SIL gene and TAL-1 gene containedan average ‘N region’ insertion of 7.8 nucleotides. The numbers of nucleotides deleted at the 5’ end and 3’ end ofTAL-1 gene were averages of 3 and 1, respectively.
Conclusion: Though the incidence of T-ALL is high in SouthIndia, the frequency of TAL-1 deletion and their fusion gene sequences are not unique and are similar to thosereported in other ethnic and geographic populations. Hence the present study indicates that TAL-1 deletionalone does not contribute to the high incidence of T-ALL in South Indian patients.