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Background The etiology of POEMS syndrome and its associated polyneuropathy have not been fully elucidated. The clinical picture of POEMS-associated polyneuropathy and nutritional polyneuropathy due to vitamin B6 (VB6) deficiency are strikingly similar, both being typically sensorimotor, symmetrical, stocking and glove distribution, and more severe in the lower extremities.Case presentation We report two consecutive POEMS patients with VB6 deficiency who showed unusual rapid and drastic recovery of polyneuropathies within 6–8 weeks after oral VB6 supplementation. Case 1 was supplemented with VB6 from time of autologous stem cell transplantation. Polyneuropathy began to improve within one week, and he became walker-free and could walk unaided with a cane within 6 weeks. Case 2 was supplemented with VB6 from time of stem cell harvest, and he became cane-free and his gait almost normalized within two months. Nerve conduction studies were also confirmatory of neurologic recovery in both cases.Conclusions Objective physical improvement of POEMS-associated polyneuropathy has been reported to typically require approximately a year after autologous stem cell transplantation, and together with our observations of VB6 deficiency and supplementations leading to accelerated recoveries of polyneuropathy, VB6 deficiency most probably contributes to POEMS-associated polyneuropathy. VB6 acts as a coenzyme in approximately 150 biochemical reactions. VB6 has been reported to inhibit the hypoxia-inducible factor/vascular endothelial growth factor (VEGF) pathway, and VEGF levels are known to corollate with disease activity of POEMS syndrome. Therefore, VB6 deficiency may contribute not only to POEMS-associated polyneuropathy, but also to the etiology of POEMS syndrome itself.

Acute myeloid leukemia (AML) is a hematologic malignancy that frequently relapses, even if remission can be achieved with intensive chemotherapy. One known relapse mechanism is the escape of leukemic cells from immune surveillance. Currently, there is no effective immunotherapy for AML because of the lack of specific antigens. Here, we aimed to elucidate the association between CD155 and CD112 in AML cell lines and primary AML samples and determine the therapeutic response. Briefly, we generated NK-92 cell lines (NK-92) with modified DNAX-associated molecule 1 (DNAM-1) and T-cell immunoglobulin and ITIM domain (TIGIT), which are receptors of CD155 and CD112, respectively. Analysis of 200 cases of AML indicated that the survival of patients with high expression of CD112 was shorter than that of patients with low expression. NK-92 DNAM-1 exhibited enhanced cytotoxic activity against AML cell lines and primary cells derived from patients with AML. DNAM-1 induction in NK-92 cells enhanced the expression of cytotoxicity-related genes, thus overcoming the inhibitory activity of TIGIT. Between CD155 and CD112, CD112 is an especially important target for natural killer (NK)-cell therapy of AML. Using a xenograft model, we confirmed the enhanced antitumor effect of NK-92 DNAM-1 compared with that of NK-92 alone. We also discovered that CD112 (Nectin-2), an immune checkpoint molecule belonging to the Nectin/Nectin-like family, functions as a novel target of immunotherapy. In conclusion, modification of the DNAM-1/CD112 axis in NK cells may be an effective novel immunotherapy for AML. Furthermore, our findings suggest that the levels of expression of these molecules are potential prognostic markers in AML.

Chemotherapy for hemodialysis (HD) patients is a challenging situation because HD patients are generally frail, and the pharmacokinetics and pharmacodynamics of most chemotherapeutics in HD patients are unknown. We report a classical Hodgkin lymphoma (cHL) patient successfully treated with 34 courses of brentuximab vedotin (BV) monotherapy, of which 30 courses were carried out during HD. Although grade 2 peripheral sensory neuropathy and one occasion of febrile neutropenia were observed, treatment was well-tolerated overall and effective. This is the first report of successful BV administration in a cHL patient on HD, and also the first to report efficacy and safety of extended courses of BV in an HD patient. Treatment options for cHL in the HD patient are limited, and extended courses of BV monotherapy may be an optimal treatment approach for some patients.

TAFRO syndrome is a relatively new disease entity first reported in 2010. We report a case of TAFRO syndrome accommodated by abnormal exacerbation of moderately differentiated gastric adenocarcinoma. The pathophysiology of TAFRO syndrome is largely unknown, but because the disease often responds to immunosuppressive therapy and also because T follicular helper (Tfh) cells are reported to be drastically decreased in TAFRO syndrome, involvement of a dysregulated immune system can be speculated. Growing evidence points toward a pivotal role of Tfh cells in tumor immunity through supporting ectopic lymphoid structures, which are recruitment sites for cells directly engaging in antitumor activity such as CD8+ T cells, NK cells, and macrophages. In fact, Tfh cells are reported to positively correlate with longer survival in human colorectal and breast cancer. Combined with our observations of hyperprogressive gastric cancer in the presented patient, an impaired tumor immunity is strongly indicated in TAFRO syndrome.