Loss of Non-Inherited Maternal MHC and Materno-Fetal Transmission of p190 Type BCR-ABL Leukemia.

Materno-fetal transmission of malignant clone is one of the rare causes of leukemia in infants. It has been recorded some 20 times over the past 100 years but definitive, genetic evidence for a maternal origin has been lacking. Here we present a detailed genetic analysis of materno-fetal transmission in a case with p190 type BCR-ABL leukemia.

A mother was found to have p190 type BCR-ABL positive acute lymphoblastic leukemia (ALL) one month after delivery of a baby, and died during induction therapy by uncontrolled bacillus cereus encephalitis. Her baby developed p190 type BCR-ABL positive B-precursor lymphoblastic lymphoma (B-LBL stage3 jaw tumor and pleural effusion) at 11-month old. Non-Hodgkin's lymphoma type chemotherapy according to Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) ALB-NHL03, followed by Hyper-CVAD imatinib therapy without stem cell transplantation were given to her, leading to complete remission for more than 31 months.

We first cloned the BCR-ABL genomic breakpoint region from the infant's pleural effusion (PE). The breakpoint was designated as a fusion between BCR intron 1 and ABL intron1. Then, We conducted Q-PCR by using BCR-ABL genomic breakpoint specific primer and sequencing. Fifteen polymorphic STR markers were amplified in the paternal blood DNA and Patient's PE and PB DNA samples using the Powerplex-16 system. HLA serotyping was by microdroplet lymphocyte cytotoxity. Genotyping was carried out using a reversed SSO HLA DNA typing method. The infant jaw tumor was further analyzed by Affymetrix high resolusion (250K) SNP arrays.

Short tandem repeat profiles indicated that the infant jaw tumor was, unambiguously, of maternal origin. Amplification of BCR-ABL genomic breakpoints on maternal leukemic cells and infant lymphoma cells revealed that these leukemia clones shared the same unique BCR-ABL genomic sequence, indicating a shared, single cell origin. Positivity of BCR-ABL specific PCR on Guthrie card blood spot also indicated that the leukemic clone was present in the blood at birth. Additionally the infant, maternal-derived leukemic cells had uniparental disomy of chromosome 6p with a deletion of non-inherited maternal MHC allele (NIMA), suggesting a mechanism for immune evasion in the baby.

This is the first case with definite evidence of in utero materno-fetal transmission of mother's leukemic cells. This case also suggests that materno-feto transfer of leukemic cells is more common than as reflected in the frequency of clinically diagnosed cases, where the immuno-surveillance, predominantly directed against major HLA locus antigens, may be the principal constraint.

No relevant conflicts of interest to declare.