Synergistic antitumor interactions between newly synthesized ruthenium complexes and cytokines in human colon carcinoma cell lines.

The purpose of these studies was to assess the antiproliferative properties of newly synthesized, heterocyclic ruthenium complexes alone and in combination with cytokines (tumor necrosis factor-alpha, interferon alfa, beta, and gamma) against various human colon carcinoma cell lines. To determine whether any of these ruthenium compounds possesses antitumor activity and reveals synergistic interaction with cytokines six new ruthenium complexes were studied. All six compounds exerted dose-dependent antitumor effects in all colon cancer cell lines tested. The most effective compounds were trans-indazolium[tetrachloro(2H-indazole)ruthenate (III, N1)] and trans-indazolium[tetrachlorobis(1 H-indazole)ruthenate (III, N2)]. Interferon alfa, beta, and gamma as well as tumor necrosis factor-alpha exerted only minimal antiproliferative effects in colon carcinoma cell lines. The data were further analyzed to determine whether preincubation with cytokines altered sensitivity of the cells to synergistically potentiating growth-inhibitory effects. Although simultaneous incubation of ruthenium complexes and interferon did not result in synergistic or additive interactions, 24-hour preincubation with interferon alfa, beta, and gamma significantly enhanced antitumor activity. We conclude from these data that two of six newly synthesized ruthenium complexes possess antiproliferative activity against a panel of human colon carcinoma cell lines. Moreover, biological modulation with interferon using 24-hour preincubation resulted in synergistic interactions. We are planning a phase I trial, since antitumor activity of these ruthenium compounds has been demonstrated in vitro and in vivo, and toxicity as well as stability data are now available.