[Long-term administration of brentuximab vedotin in a patient with primary cutaneous anaplastic large cell lymphoma with peripheral blood involvement with leukemic change].

We report a case of long-term administration of brentuximab vedotin (BV) for primary cutaneous anaplastic large cell lymphoma (pc-ALCL) with leukemic change. A 67-year-old man with lymphadenopathy was admitted to our hospital. Six years ago, he was diagnosed with pc-ALCL at another hospital, and complete remission was achieved with radiation therapy. We performed a biopsy of his lymph node and diagnosed the recurrence of pc-ALCL with leukemic change. Initially, CHOP and GCD regimens were ineffective; however, partial remission was achieved following BV therapy. Thus far, he has received 42 courses of BV; he has responded well to the treatment and no serious side effects have been observed.

Reactive oxygen species generated by hematopoietic cytokines play roles in activation of receptor-mediated signaling and in cell cycle progression.

Hematopoietic cytokines, including interleukin (IL)-3 and erythropoietin (Epo), regulate hematopoiesis by stimulating their receptors coupled with the Jak2 tyrosine kinase to induce receptor tyrosine phosphorylation and activate mainly the STAT5, PI3K/Akt, and Ras/MEK/ERK signaling pathways. Here we demonstrate that IL-3 or Epo induces a rapid and transient (peaking at 30 min) as well as late progressive increase in reactive oxygen species (ROS) in a hematopoietic progenitor model cell line, 32Dcl3, and its subclone expressing the Epo receptor (EpoR), 32D/EpoR-Wt. The cytokine-induced ROS generation was not affected in 32Dcl3 cells depleted of mitochondrial DNA. The antioxidant N-acetyl-L-cysteine (NAC) inhibited IL-3-induced tyrosine phosphorylation of Jak2, IL-3 receptor betac subunit (IL-3Rbetac), and STAT5 as well as activation-specific phosphorylation of Akt, MEK, and ERK, while treatment of cells with H2O2 activated these signaling events. NAC also inhibited the EpoR-induced transphosphorylation of IL-3Rbetac. Moreover, NAC treatment reduced the expression levels of c-Myc, Cyclin D2, and Cyclin E, and induced expression of p27, thus inhibiting the G1 to S phase transition of cells cultured with IL-3. Further studies have shown that the degradation of c-Myc was facilitated or inhibited by treatment of cells with NAC or H2O2, respectively. These data indicate that the rapid generation of ROS by cytokine stimulation, which is at least partly independent of mitochondria, may play a role in activation of Jak2 and the STAT5, PI3K/Akt, and Ras/MEK/ERK signaling pathways as well as in transactivation of cytokine receptors. The cytokine-induced ROS generation was also implicated in G1 to S progression, possibly through stabilization of c-Myc and induction of G1 phase Cyclin expression leading to suppression of p27.

Calmodulin physically interacts with the erythropoietin receptor and enhances Jak2-mediated signaling.

Stimulation of the erythropoietin receptor (EpoR) induces a transient increase in intracellular Ca2+ level as well as activation of the Jak2 tyrosine kinase to stimulate various downstream signaling pathways. Here, we demonstrate that the universal Ca2+ receptor calmodulin (CaM) binds EpoR in a Ca2+-dependent manner in vitro. Binding studies using various EpoR mutants in hematopoietic cells showed that CaM binds the membrane-proximal 65-amino-acid cytoplasmic region (amino acids 258-312) of EpoR that is critical for activation of Jak2-mediated EpoR signaling. Structurally unrelated CaM antagonists, W-13 and CMZ, inhibited activation of Jak2-mediated EpoR signaling pathways, whereas W-12, a W-13 analog, did not show any significant inhibitory effect. Moreover, overexpression of CaM augmented Epo-induced tyrosine phosphorylation of the EpoR. W-13, but not W-12, also inhibited Epo-induced proliferation and survival. Together, these results indicate that CaM binds to the membrane-proximal EpoR cytoplasmic region and plays an essential role in activation of Jak2-mediated EpoR signaling.