Cancer immunotherapy has recently attracted attention as an approach for cancer treatment through the activation of the immune system. Group-specific component (Gc) protein is a precursor for macrophage activating factor (GcMAF), which has a promising immunomodulatory effect on the suppression of tumor growth and angiogenesis. In this study, we successfully purified Gc protein from human serum using anion-exchange chromatography combined with affinity chromatography using a 25-OH-D₃-immobilized column. The purity of Gc protein reached 95.0% after anion-exchange chromatography. The known allelic variants of Gc protein are classified into three subtypes—Gc1F, Gc1S and Gc2. The fragment sequence of residues 412–424 determined according to their MS/MS spectra is available to evaluate the subtypes of Gc protein. The data showed that the Gc protein purified in this study consisted of the Gc1F and Gc2 subtypes. Our method improved the purity of Gc protein, which was not affected by the treatment to convert it into GcMAF using β-galactosidase- or neuraminidase-immobilized resin, and will be useful for biological studies and/or advanced clinical uses of GcMAF, such as cancer immunotherapy.

通过激活免疫系统，癌症免疫疗法作为一种癌症治疗方法最近引起了关注。特定于组的成分（Gc）蛋白是巨噬细胞活化因子（GcMAF）的前体，它对抑制肿瘤生长和血管生成具有有希望的免疫调节作用。在这项研究中，我们成功地使用阴离子交换色谱结合使用25-OH-D _3的亲和色谱从人血清中成功纯化了Gc蛋白-固定柱。阴离子交换层析后，Gc蛋白的纯度达到95.0％。已知的Gc蛋白等位基因变体分为三个亚型-Gc1F，Gc1S和Gc2。根据其MS / MS光谱确定的残基412–424的片段序列可用于评估Gc蛋白的亚型。数据表明，在这项研究中纯化的Gc蛋白由Gc1F和Gc2亚型组成。我们的方法提高了Gc蛋白的纯度，不受使用β-半乳糖苷酶或神经氨酸酶固定化树脂将其转化为GcMAF的处理的影响，该方法可用于GcMAF的生物学研究和/或高级临床应用，例如癌症免疫疗法。