Enhancement of Th1 type cytokine production and primary T cell activation by PBI-1393

In previous reports, we have shown that PBI-1393 (formerly BCH-1393), N,N-Dimethylaminopurine pentoxycarbonyl d-arginine, stimulates cytotoxic T-lymphocyte (CTL) responses both in vitro and in vivo in normal immune status and immunosuppressed mice. Additionally, PBI-1393 was tested for anticancer activity in syngeneic mouse experimental tumor models and it displayed significant inhibition of tumor outgrowths when given in combination with sub-therapeutic doses of cytotoxic drugs (cyclophosphamide, 5-fluorouracil, doxorubicin and cis-platinum). However, the mechanism of action of PBI-1393 was still unknown. Here, we report that PBI-1393 enhances IL-2 and IFN-γ production in human activated T cells by 51% and 46% respectively. PBI-1393 increases also IL-2 and IFN-γ mRNA expression as shown by RT-PCR. The physiological relevance of IL-2 and IFN-γ gene modulation by PBI-1393 is illustrated by the advantageous increase of T cell proliferation (39 ± 0.3% above control) and human CTL response against prostate (PC-3) cancer cells (42 ± 0.03%). The enhancement of human T cell proliferation and CTL activation by PBI-1393 demonstrates that this compound potentiates the immune response and in this regard, it could be used as an alternative approach to IL-2 and/or IFN-γ therapy against cancer.