Synergistic actions of picibanil (OK-432) on recombinant interleukin-2 induction of tumor-infiltrating lymphocyte expansion, cytotoxicity, and phenotypic differentiation.

Tumor-infiltrating lymphocytes (TILs) comprise a subpopulation of lymphoid cells that infiltrate into growing tumors. These cells can be activated in vitro with recombinant interleukin-2 (rIL-2) to become highly cytotoxic against fresh tumor targets in vitro and against a variety of systemic metastases in vivo. OK-432 is a well-known inducer of NK cells and immune effector T cells. This study was designed to evaluate the effects of OK-432 on (a) the generation and (b) the cytotoxic potential of rIL-2-induced TILs. When TILs obtained from a murine colon adenocarcinoma (the MC-38 tumor) were cultured in complete media supplemented with 100 U of rIL-2/ml and 1.0 microgram of OK-432/ml, the number of TILs generated was greater than that seen with rIL-2 or OK-432 alone (number of TILs on day 15 of culture: 100 U of rIL-2/ml: 268 x 10(5) TILs; 1.0 microgram of OK-432/ml: 30 x 10(5) TILs; 100 U of rIL-2/ml + 1.0 microgram of OK-432/ml: 528 x 10(5) TILs). Higher concentrations of OK-432 had deleterious effects on TIL growth characteristics. TILs generated in 100 U of rIL-2 and 1.0 microgram of OK-432/ml of complete media demonstrated greater tumor lysis compared to rIL-2 alone (% lysis against MCA-102 target; 100 U of rIL-2/ml: 12%; 100 U of rIL-2/ml and 1.0 microgram of OK-432/ml: 50%; effector target ratio 20:1; p less than 0.001). Similar results were seen against the NK-sensitive YAC-1 lymphoma target.(ABSTRACT TRUNCATED AT 250 WORDS)