Center for Novel Therapeutics, Moores Cancer Center, University of California San Diego, La Jolla, CA, USA.
Leukemia. 2021 Jun;35(6):1621-1630. doi: 10.1038/s41375-020-01055-7. Epub 2020 Oct 23.
Patients with chronic lymphocytic leukemia (CLL) have high plasma-levels of Wnt5a, which can induce phosphorylation of ERK1/2 and enhance CLL-cell proliferation. Such effects could be inhibited by treatment with an ERK1/2 inhibitor, ERK1/2-specific siRNA, or cirmtuzumab, an anti-ROR1 mAb. The CLL-derived line, MEC1, expresses Wnt5a, but not ROR1. MEC1 cells transfected to express ROR1 (MEC1-ROR1) had higher levels of phosphorylated ERK1/2 than parental MEC1, or MEC1 transfected with ROR1ΔPRD, a truncated ROR1 lacking the cytoplasmic proline-rich domain (PRD), or ROR1 a mutant ROR1 with a P→A substitution at 808, which is required for complexing with the Rac-specific-guanine-nucleotide-exchange factor DOCK2 upon stimulation with Wnt5a. We silenced DOCK2 with siRNA and found this repressed the capacity of Wnt5a to induce ERK1/2 phosphorylation in MEC1-ROR1 or CLL cells. CLL cells that expressed ROR1 had higher levels of phosphorylated ERK1/2 or DOCK2 than CLL cells lacking ROR1. Although we found ibrutinib could inhibit the phosphorylation of ERK1/2 and DOCK2 induced by B-cell-receptor ligation, we found that this drug was unable to inhibit Wnt5a-induced, ROR1-dependent phosphorylation of ERK1/2 or DOCK2. This study demonstrates that Wnt5a can induce activation of ERK1/2 and enhance CLL-cell proliferation via a ROR1/DOCK2-dependent pathway independent of BTK.
慢性淋巴细胞白血病（CLL）患者的血浆 Wnt5a 水平较高，可诱导 ERK1/2 磷酸化，增强 CLL 细胞增殖。这种作用可被 ERK1/2 抑制剂、ERK1/2 特异性 siRNA 或 cirmtuzumab（一种抗 ROR1 mAb）抑制。CLL 来源的 MEC1 细胞表达 Wnt5a，但不表达 ROR1。转染表达 ROR1 的 MEC1 细胞（MEC1-ROR1）的磷酸化 ERK1/2 水平高于亲本 MEC1 或转染 ROR1ΔPRD（缺失细胞质富含脯氨酸结构域的截短 ROR1）或 ROR1 P→A 突变体（R808 处的 P 突变为 A，这是与 Rac 特异性鸟苷酸交换因子 DOCK2 复合所必需的）的 MEC1 细胞。我们用 siRNA 沉默 DOCK2，发现这抑制了 Wnt5a 诱导 MEC1-ROR1 或 CLL 细胞 ERK1/2 磷酸化的能力。表达 ROR1 的 CLL 细胞的磷酸化 ERK1/2 或 DOCK2 水平高于缺乏 ROR1 的 CLL 细胞。虽然我们发现伊布替尼可抑制 B 细胞受体交联诱导的 ERK1/2 和 DOCK2 磷酸化，但发现该药物不能抑制 Wnt5a 诱导的、ROR1 依赖性的 ERK1/2 和 DOCK2 磷酸化。本研究表明，Wnt5a 可通过 ROR1/DOCK2 依赖的途径诱导 ERK1/2 激活并增强 CLL 细胞增殖，该途径独立于 BTK。
