Preferential in-vitro growth and expansion of leukemic T lymphoblasts

An in-vitro culture system was used to selectively grow malignant cells from the bone marrow of a patient with acute T-lymphoblastic leukemia. Molecular analysis of DNA extracted from the bone marrow cells before culture showed the presence of both rearranged and germ line patterns for the T-cell beta receptor (CTB) gene, and chromosomal analysis revealed the presence of a major and a minor abnormal clone. The cells were cultured in RPMI medium supplemented with 20% fetal calf serum, 2% lymphocyte conditioned medium, L-glutamine and antibiotics. The presence of malignant cells in the cultured population was confirmed by morphologic, molecular probing and cytogenetic analysis. After four weeks in culture, DNA extracted from the cultured cells showed only the rearranged pattern for the CTB gene. Chromosomal analysis of the same cultured sample revealed only the presence of the initially predominant abnormal clone. Shortly thereafter, analysis of fresh uncultured bone marrow cells from the patient in relapse revealed that the same chromosomally abnormal clone also predominated in vivo. Thus, our results demonstrate the selective nature of this culture system and its ability to amplify leukemic T-lymphoblasts. This culture system is also useful for detecting occult malignant cells in histologically normal bone marrow.