Sayers T J, Wiltrout T A, McCormick K, Husted C, Wiltrout R H
Biological Carcinogenesis Development Program, NCI-Frederick Cancer Research Facility, Maryland 21701-1013.
Cancer Res. 1990 Sep 1;50(17):5414-20.
Previous studies have shown that established murine renal cancer (Renca) can be successfully treated with the investigational drug flavone acetic acid (FAA) used in combination with recombinant interleukin 2 (IL-2). Additional experiments demonstrated that the in vivo administration of FAA rapidly induced the expression of the genes, as well as the biologically active proteins, for alpha- and beta-interferons (IFNs) as well as tumor necrosis factor alpha. Both IFN-alpha and IFN-gamma have been shown to have direct antiproliferative effects against some tumors, as well as being potent immunodulators for the induction of antitumor effector cells. Thus, the present study was designed to investigate the ability of IFN-alpha and/or IFN-gamma to mediate direct antiproliferative effects against Renca in vitro as well as to cause regression of Renca in vivo. The present study confirms that RAA and/or IL-2 are inactive against Renca in vitro, further suggesting an indirect mechanism for FAA-induced antitumor effects in vivo. However, the exposure of Renca in vitro to recombinant human IFN-alpha A/D, murine IFN-alpha or murine IFN-beta resulted in a dose dependent growth inhibition of Renca as assessed by the microculture tetrazolium dye incorporation assay. Very little growth inhibition was induced by recombinant murine IFN-gamma. Interestingly, IFN-alpha (100-1000 units/ml) when combined with very low doses of recombinant murine IFN-gamma (1-10 units/ml) yielded significantly more pronounced growth inhibition than either cytokine alone. This effect was most evident by 5 days of culture where combinations of 100-1000 units/ml recombinant human IFN-alpha A/D with 1-5 units/ml recombinant murine IFN-gamma yielded growth inhibition in the range of 45-99%. In order to determine whether the mechanisms for the antitumor activity of recombinant human IFN-alpha A/D and recombinant murine IFN-gamma was due to their direct antiproliferative effects, we also studied the efficacy of these combinations against i.p. Renca in athymic mice. In contrast to the potent antitumor effects observed in euthymic mice, the combination of IFN-alpha and IFN-gamma only slightly increased mean survival times in athymic mice and no long term survivors were obtained. Subsequent studies demonstrated that most mice (77%) cured of peritoneal Renca by recombinant human IFN-alpha A/D plus recombinant murine IFN-gamma were immune to rechallenge. Therefore the combination of IFN-alpha and IFN-gamma may directly inhibit the growth of Renca, but a major effect of IFNs in vivo must be to contribute to the induction of an anti-Renca immune response.
先前的研究表明，已建立的小鼠肾癌（Renca）可用研究性药物黄酮乙酸（FAA）与重组白细胞介素2（IL-2）联合成功治疗。额外的实验表明，体内给予FAA可迅速诱导α-和β-干扰素（IFN）以及肿瘤坏死因子α的基因及其生物活性蛋白的表达。IFN-α和IFN-γ均已显示对某些肿瘤具有直接的抗增殖作用，并且是诱导抗肿瘤效应细胞的有效免疫调节剂。因此，本研究旨在研究IFN-α和/或IFN-γ在体外介导对Renca的直接抗增殖作用以及在体内使Renca消退的能力。本研究证实，RAA和/或IL-2在体外对Renca无活性，这进一步提示了FAA在体内诱导抗肿瘤作用的间接机制。然而，通过微量培养四唑盐染料掺入试验评估，体外将Renca暴露于重组人IFN-αA/D、小鼠IFN-α或小鼠IFN-β导致Renca呈剂量依赖性生长抑制。重组小鼠IFN-γ诱导的生长抑制非常小。有趣的是，当IFN-α（100 - 1000单位/毫升）与非常低剂量的重组小鼠IFN-γ（1 - 10单位/毫升）联合使用时，产生的生长抑制比单独使用任何一种细胞因子都更明显。在培养5天时这种效应最为明显，其中100 - 1000单位/毫升重组人IFN-αA/D与1 - 5单位/毫升重组小鼠IFN-γ的组合产生的生长抑制范围为45 - 99%。为了确定重组人IFN-αA/D和重组小鼠IFN-γ的抗肿瘤活性机制是否归因于它们的直接抗增殖作用，我们还研究了这些组合对无胸腺小鼠腹腔内Renca的疗效。与在有胸腺小鼠中观察到的强大抗肿瘤作用相反，IFN-α和IFN-γ的组合仅略微增加了无胸腺小鼠的平均存活时间，并且没有获得长期存活者。随后的研究表明，大多数（77%）通过重组人IFN-αA/D加重组小鼠IFN-γ治愈腹膜Renca的小鼠对再次攻击具有免疫力。因此，IFN-α和IFN-γ的组合可能直接抑制Renca的生长，但IFN在体内的主要作用必须是有助于诱导抗Renca免疫反应。
