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 genetic abnormality in T-ALL.


OBJECTIVE
The present study was aimed to detect the incidence of type 1 and type 2 TAL-1 deletions and assess whether they might contribute to the high incidence of T-ALL in South India.


METHODS
45 cases of T-ALL (pediatric-32, adolescents-7 and young adults-6) were studied by DNA-PCR and sequencing. Age of the patients ranged from 3 yrs to 29 yrs (median age 14 yrs).


RESULTS
TAL-1 deletion type 1 was detected in 6 (13.3%) cases (3 pediatric and 3 adolescents) and all were males. TAL-1 deletion type 2 was not present. Comparing the clinical features and immunological marker analysis of TAL-1 deletion positive and negative cases did not show any significant differences except in the WBC count, which was significantly higher in cases showing TAL-1 deletion (>100 x 109/L, p value= 0.003). All the positive cases of TAL-1 deletion were confirmed by sequencing, the results showing that the fusion region at SIL gene and TAL-1 gene contained an average 'N region' insertion of 7.8 nucleotides. The numbers of nucleotides deleted at the 5' end and 3' end of TAL-1 gene were averages of 3 and 1, respectively.


CONCLUSIONS
Though the incidence of T-ALL is high in South India, the frequency of TAL-1 deletion and their fusion gene sequences are not unique and are similar to those reported in other ethnic and geographic populations. Hence the present study indicates that TAL-1 deletion alone does not contribute to the high incidence of T-ALL in South Indian patients.
Sudhakar
N
N
Department of Molecular Oncology, Cancer Institute WIA, Chennai 600036, Tamil Nadu, India. nsudha79@rediffmail.com
Nirmala
K
K
Rajalekshmy
K R
KR
Rajkumar
T
T
D000293:Adolescent; D000328:Adult; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007194:India / Q000453:epidemiology; D008297:Male; D016133:Polymerase Chain Reaction; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D017384:Sequence Deletion; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D055815:Young Adult
D051792:Basic Helix-Loop-Helix Proteins; D011518:Proto-Oncogene Proteins; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; C067143:TAL1 protein, human