Background: We have previously established tumour T-cell lines, both from the skin and from the blood of patients with a cutaneous T-cell lymphoma (CTCL). In one patient, the tumour cells and the derived cell lines had a CD3+ CD4+ CD8- phenotype and a trisomy of chromosome 7. They expressed three T-cell receptor (TCR) beta-chain transcripts, but only one was productively rearranged and expressed at the cell membrane.
Objectives: In the present study, we tried to isolate a fast-growing new tumour T-cell line from the same patient.
Patients/methods: We performed direct cell cloning of the skin tumour lymphocyte population, which led to the isolation of an interleukin-2-dependent highly proliferative T-cell subclone, named Cou-L3, with a CD3+ TCR-Vbeta13+ CD4- CD8alphaalpha+ phenotype.
Results: We demonstrated that Cou-L3 was identical to the original clonal tumour CD3+ Vbeta13+ CD4+ CD8- cells, as it expressed the same rearranged TCR-Vbeta13 chain. We further studied the functional activity of these CD8alphaalpha+ Vbeta13+ Cou-L3 cells. We found that these cells exhibited CD3-redirected cytotoxic activity.
Conclusions: An immunophenotypic shift, with a change from a CD4+ to a CD8+ phenotype, has been already reported in association with disease progression in CTCL. However, in these cases, there has been no demonstration that the phenotypic change involved the same T-cell clone. The present study is the first report of the phenotypic heterogeneity of the tumour clonal cell population in CTCL.