T-cell number and subtype influence the disease course of primary chronic lymphocytic leukaemia xenografts in alymphoid mice

Chronic lymphocytic leukaemia (CLL) cells require micorenvironmental support for their proliferation. This can be recapitulated in highly immunocompromised hosts in the presence of T-cells and other supporting cells. Current primary CLL xenograft models suffer from limited duration of tumour cell engraftment coupled with gradual T-cell outgrowth. Thus, a greater understanding of the interaction between CLL and T-cells could improve their utility. In this study, using two distinct xenograft models, we investigated whether xenografts recapitulate CLL biology including natural environmental interactions with B-cell receptors and T-cells and whether manipulation of autologous T-cells can expand the duration of CLL engraftment. We observed that primary CLL xenografts recapitulated both the tumour phenotype and T-cell repertoire observed in patients and that engraftment was significantly shorter for progressive tumours. Reduction of patients' T-cells to 2-5% of the initial T-cell number or specific depletion of CD8(+) cells extended the limited xenograft duration of progressive cases to that characteristic of indolent disease. We conclude that manipulation of T-cells can enhance current CLL xenograft models expanding their utility for investigation of tumour biology and pre-clinical drug assessment.