DNMT1 and B-cell non-Hodgkin lymphoma: To test whether DNMT up-regulation in B-cells was possibly resulting from a soluble Tat released from infected cells and taken up by uninfected B-cells, we used an in vitro model of B-cell lymphoma in which Tat was ectopically expressed either by exposure to soluble Tat or by transient and stable transfections.