Hayashi Kazumi, Nagasaki Eijiro, Kan Shin, Ito Masaki, Kamata Yuko, Homma Sadamu, Aiba Keisuke
Division of Oncology, The Jikei University School of Medicine, Tokyo, Japan.
Division of Clinical Oncology and Hematology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan.
Cancer Sci. 2016 May;107(5):682-9. doi: 10.1111/cas.12918. Epub 2016 Apr 7.
Although rituximab, a chimeric monoclonal antibody that specifically binds to CD20, has significantly improved the prognosis for diffuse large B cell lymphoma (DLBCL), one-third of DLBCL patients demonstrate resistance to rituximab or relapse after rituximab treatment. Thus, a novel approach to rituximab-based treatment is likely to be required to improve the efficacy of DLBCL treatment. As complement dependent cytotoxicity (CDC) is a key mechanism mediating rituximab's tumoricidal activity, rituximab binding to CD20 on tumor cells is a critical factor for effective rituximab-based treatments against DLBCL. We found that gemcitabine (GEM), but not lenalidomide (LEN) or azacitidine (AZA), can upregulate CD20 expression in TK and KML-1 cells, two human DLBCL cell lines. Treatment of TK and KML-1 cells with GEM enhanced CD20 expression at both the mRNA and protein levels. CD20 upregulation by GEM treatment was accompanied by increased rituximab binding to CD20. In TK cells, GEM treatment synergistically increased rituximab-mediated CDC activity in a dose-dependent manner. In KML cells, GEM treatment also induced upregulation of complement regulatory proteins, possibly leading to resistance to CDC. Treatment with LEN, a drug that did not upregulate CD20, did not enhance rituximab-mediated CDC activity. GEM treatment activated nuclear factor-kappa B (NF-kB) signaling in these cells. Furthermore, a specific inhibitor to NF-kB suppressed GEM-induced CD20 upregulation, indicating that GEM-induced NF-kB activation is closely associated with CD20 upregulation. These results suggest that when used in combination, GEM might enhance the antitumor efficacy of rituximab against DLBCL due to its unique ability to upregulate CD20.
尽管利妥昔单抗是一种特异性结合CD20的嵌合单克隆抗体，已显著改善弥漫性大B细胞淋巴瘤（DLBCL）的预后，但仍有三分之一的DLBCL患者对利妥昔单抗耐药或在利妥昔单抗治疗后复发。因此，可能需要一种基于利妥昔单抗治疗的新方法来提高DLBCL治疗的疗效。由于补体依赖性细胞毒性（CDC）是介导利妥昔单抗杀瘤活性的关键机制，利妥昔单抗与肿瘤细胞上的CD20结合是基于利妥昔单抗有效治疗DLBCL的关键因素。我们发现，吉西他滨（GEM）而非来那度胺（LEN）或阿扎胞苷（AZA）可上调两种人DLBCL细胞系TK和KML-1细胞中的CD20表达。用GEM处理TK和KML-1细胞可在mRNA和蛋白质水平增强CD20表达。GEM处理导致的CD20上调伴随着利妥昔单抗与CD20结合的增加。在TK细胞中，GEM处理以剂量依赖的方式协同增加利妥昔单抗介导的CDC活性。在KML细胞中，GEM处理也诱导补体调节蛋白上调，可能导致对CDC产生抗性。用未上调CD20的药物LEN处理并未增强利妥昔单抗介导的CDC活性。GEM处理激活了这些细胞中的核因子-κB（NF-κB）信号通路。此外，NF-κB的特异性抑制剂可抑制GEM诱导的CD20上调，表明GEM诱导的NF-κB激活与CD20上调密切相关。这些结果表明，联合使用时，GEM可能因其上调CD20的独特能力而增强利妥昔单抗对DLBCL的抗肿瘤疗效。
