Antimetastatic and antitumor effects of 2,4-diamino-6-(pyridine-4-yl)-1,3,5-triazine (4PyDAT) on the high lung metastatic colon 26 tumor in mice.

The therapeutic potential of a diaminotriazine, 2,4-diamino-6-(pyridine-4-yl)-1,3,5-triazine (4PyDAT), was investigated in a metastatic model using the mouse colon 26 carcinoma variant (Co26Lu), which preferentially metastasizes to the lung of mouse. The compound had a moderate antimetastatic activity as well as antitumor activity, without toxicity to the host, when administered orally. In the cytotoxicity test in vitro, 4PyDAT showed very weak direct cytotoxicity against the Co26Lu cell line, Co26Lu(F55) (IC50 < or = 1000 microM). Less microcapiral formation on tumors were observed for the treated group with a hemorrhage than the control group under microscopy. 4PyDAT significantly inhibited the production of urokinase-type plasminogen activator (u-PA) in Co26Lu(F55) cells. These results suggest that the antimetastatic and antitumor activities of 4PyDAT are due in part to inhibition of angiogenesis, rather than direct antiproliferative action on the tumor cells. 4PyDAT may become a lead compound to develop antitumor triazine derivatives based on antiangiogenic action.

Effects of interleukin-2 and interferon-alpha A/D treatment on lymphocytes from tumour-bearing mice.

The in vivo antitumour activities of recombinant human interleukin-2 (rHIL-2) and recombinant human hybrid interferon alpha A/D (rIFN-alpha A/D) were tested in relation to adenocarcinoma 755. The tumour growth, following s.c. inoculation of tumour cells, was inhibited to a greater extent in mice treated with the combination of cytokines than in mice treated with either one alone. Pretreatment with these cytokines did not affect the tumour growth. Injection of tumour-bearing mice with a combination of these cytokines resulted in a marked increase in the total number of lymphocytes in the peritoneal cavity. Among them, Lyt-2+/L3T4- and asialo GM1+ cells were markedly enhanced by the combination of cytokines, and the frequencies of these marker cells were closely correlated with the antitumour activity. In tumour-bearing mice, the size of the thymus was decreased while that of the spleen was increased compared to non-tumour-bearing (normal) mice. Treatment with rHIL-2 caused the thymus, spleen and liver to be larger compared to untreated tumour-bearing mice, but when treated with a combination of rHIL-2 and rIFN-alpha A/D these organs were smaller than when rHIL-2 was administered alone. Thymocytes were drastically changed when mice were bearing a tumour or were treated with a cytokine. Especially immature T-cells, Lyt-2+/L3T4+, were drastically decreased in tumour-bearing mice, but were maintained following administration of rHIL-2 or rIFN-alpha A/D. When treated with rHIL-2 plus rIFN-alpha A/D, Lyt-2+/L3T4+ T-cells were decreased while Lyt-2+/L3T4- T-cells were increased. Frequency of immature T-cells, Lyt-2-/L3T4-, was not changed. On the other hand, T-cell subsets of splenocytes were markedly decreased in tumour-bearing mice compared to normal mice, but all the subsets of splenocytes were almost unchanged even when tumour-bearing mice were treated with rHIL-2 plus rIFN-alpha A/D. Thus, injection of rHIL-2 and rIFN-alpha A/D to tumour-bearing mice resulted in induction of Lyt-2+/L3T4- and asialo GM1+ cells in the peritoneal cavity, and the frequencies correlated with the observed antitumour activity in vivo in this murine model. The increase in Lyt-2+/L3T4- T-cells in the peritoneal cavity may be related to changes in the T-cells in thymus.

Synergistic effect of recombinant interleukin-2 on the inhibition of growth of adenocarcinoma 755 by mitomycin.

The increase in life-span (ILS) of tumor-bearing mice caused by recombinant interleukin-2 (RIL-2) was studied in the solid tumor adenocarcinoma 755 system. With long-term treatment (Days 5-12), RIL-2 (10(5) U/mouse) showed a weak effect (24% ILS), but short-term RIL-2 treatment (Days 5-8 or 9-12) had hardly any effect. Mitomycin, at 2 mg/kg (maximum nontoxic dose), caused 35% ILS with Days 5-8 treatment and only 12% ILS with Days 9-12 treatment. Sequential treatment with mitomycin (Days 5-8) and RIL-2 (Days 9-12) markedly enhanced antitumor activity (88% ILS). This value is significantly greater than that of mitomycin alone or RIL-2 alone (P less than 0.01). Furthermore, mitomycin followed by RIL-2 markedly augmented killing activity of spleen cells that are cytotoxic in vitro. These results indicate that RIL-2 markedly affects the inhibition of growth of a tumor treated with an antitumor agent.