Abstract
We examined leukemic lymphocyte precursors from ALL patients as well as immortalized ALL cell lines for cytoplasmic histamine expression. The histamine levels ranged from 10.8 pg/106 cells to 82.2 pg/106 cells in ALL cell lines (N=4) and from 12.5 pg/106 cells to 1235.4 pg/106 cells for primary leukemic cells from ALL patients (N=13). The presence of histamine in the cytoplasm of these ALL cells was also confirmed by immunostaining using a polyclonal rabbit anti-histamine antibody. Notably, the histamine receptor blocker diphenhydramine inhibited the clonogenic growth of ALL cells by <90% prompting the hypothesis that histamine may be an autocrine regulator of ALL cell proliferation. Our study suggests that histamine receptor blockers may therefore be useful for the treatment of therapy-refractory ALL.