Baum Natalie, Fliegert Ralf, Bauche Andreas, Hambach Julia, Menzel Stephan, Haag Friedrich, Bannas Peter, Koch-Nolte Friedrich
Institute of Immunology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Cancers (Basel). 2020 Dec 30;13(1):76. doi: 10.3390/cancers13010076.
The nucleotides ATP and NAD are released from stressed cells as endogenous danger signals. Ecto-enzymes in the tumor microenvironment hydrolyze these inflammatory nucleotides to immunosuppressive adenosine, thereby, hampering anti-tumor immune responses. The NAD hydrolase CD38 is expressed at high levels on the cell surface of multiple myeloma (MM) cells. Daratumumab, a CD38-specific monoclonal antibody promotes cytotoxicity against MM cells. With long CDR3 loops, nanobodies and nanobody-based heavy chain antibodies (hcAbs) might bind to cavities on CD38 and thereby inhibit its enzyme activity more potently than conventional antibodies. The goal of our study was to establish assays for monitoring the enzymatic activities of CD38 on the cell surface of tumor cells and to assess the effects of CD38-specific antibodies on these activities. We monitored the enzymatic activity of CD38-expressing MM and other tumor cell lines, using fluorometric and HPLC assays. Our results showed that daratumumab and hcAb MU1067 inhibit the ADPR cyclase but not the NAD hydrolase activity of CD38-expressing MM cells. We conclude that neither clinically approved daratumumab nor recently developed nanobody-derived hcAbs provide a second mode of action against MM cells. Thus, there remains a quest for "double action" CD38-inhibitory antibodies.
核苷酸ATP和NAD作为内源性危险信号从应激细胞中释放出来。肿瘤微环境中的胞外酶将这些炎性核苷酸水解为具有免疫抑制作用的腺苷，从而阻碍抗肿瘤免疫反应。NAD水解酶CD38在多发性骨髓瘤（MM）细胞的细胞表面高水平表达。达雷妥尤单抗是一种CD38特异性单克隆抗体，可促进对MM细胞的细胞毒性。由于具有长的互补决定区3（CDR3）环，纳米抗体和基于纳米抗体的重链抗体（hcAb）可能与CD38上的腔结合，从而比传统抗体更有效地抑制其酶活性。我们研究的目的是建立监测肿瘤细胞表面CD38酶活性的测定方法，并评估CD38特异性抗体对这些活性的影响。我们使用荧光测定法和高效液相色谱（HPLC）测定法监测表达CD38的MM细胞系和其他肿瘤细胞系的酶活性。我们的结果表明，达雷妥尤单抗和hcAb MU1067抑制表达CD38的MM细胞的ADP核糖环化酶活性，但不抑制其NAD水解酶活性。我们得出结论，临床批准的达雷妥尤单抗和最近开发的源自纳米抗体的hcAb均未提供针对MM细胞的第二种作用模式。因此，仍然需要“双重作用”的CD38抑制性抗体。
