br Materials and methods br Results br Discussion The

Materials and methods
Results
Discussion The treatment regimen used in this study is generally safe and well tolerated. The process of generating therapeutic numbers of CART-138 order SCR7 by limiting their dilutions proved to be quite difficult; however, the target cell dose was reached with a toxicity of only one or two grades in all five patients. No evidence of obvious tumor lysis syndrome or an inflammatory storm was found under normal levels of serum calcium or lactate dehydrogenase. The development of tumor lysis syndrome after cellular immunotherapy has not been reported previously [18]. CART cells are capable of generating extensive cytotoxicity in vivo caused by cytokine production, which was positively correlated with the degree of the tumor burden and the infusion dose [19]. Therefore, an adverse reaction could be provoked by administering CART cells to patients with small disease burdens. Another possible means of reducing acute toxicities after CART cell infusions is to administrate multiple, smaller doses of CAR-transduced T cells rather than one large dose [20]. The burden of myeloma in this patient was not large; the cell proliferation of MM itself was slow; and the process of infusion was divided into six doses, none of which were sufficient to cause extensive damage. The research for therapeutic choices of relapsed and refractory MM is still ongoing because there is hardly any conclusive data outlining the most appropriate way of treatments for these in previous literature. The adoptive transfer of genetically engineered immune effector cells to rapidly establish T cell-mediated tumor immunity is the available choice [21]. In this approach, the patient\'s own T cells are targeted to tumor cells through a transgene-encoded Ag receptor consisting of a CAR, which is composed of an extracellular Ag recognition domain, most commonly a single chain fragment variable derived from a mAb that has been fused to a transmembrane domain, and a cytoplasmic signaling domain, most commonly including that of the CD3 chain [10,21–23]. When expressed in T cells, CARs efficiently redirect T-cell specificity and cytotoxicity toward cells expressing the targeted Ag in HLA-independent manner [24,25]. Previous research has shown that genetically modified NK-92 cells expressing the CAR anti-CD138 were identified to induce an intensified anti-myeloma immunoresponse and to reinforce the lysis and apoptosis of myeloma cells in cell lines and mice [16]. One study reported treating four patients of progressive MM with iodine-131-labeled anti-CD138 monoclonal antibody (mAb). One patient of the four received partial response, the other three patients did not achieve response, their M-protein stayed in the peak. Moreover, one patient suffered from 3/4-grade hematological toxicity for 39 days after the treatment [9]. Efficacy was noted in this study, although long-term outcomes should be followed up separately. There were clinical responses in our research showing that the advanced MM patients were returned to stable conditions after CART-138 infusions. In one patient (UPN 1), 10.5% of CD138+ myeloma cells were observed in peripheral blood before treatment with our protocol. After treatment, when the patient was in remission, the level tended to be 1–3%. Detailed cell surface marker analysis was performed to assess the phenotype of the expanded cells. The data indicate that CART-138 cells can specifically recognize and kill unmanipulated, autologous MM cells in vivo. To act on and within the tumor, genetically modified T cells must home to the site of the malignancy [10]. The trafficking of modified T cells was detectable by qPCR in the bone marrow 24–to48 h after the final infusion among the patients with lymphoma treated by CD20-specific adoptive immunotherapy [11,26]. The CART-19 cells were observed at high level within five weeks after therapy in the BM of the patients with ALL and CLL [27]. In our study, a high expansion of CART-138 could be detected after eight weeks, and the cells were able to enter into the BM at a high copy number. In UPN1, the expansion of CART-138 cells in the BM increased persistently, although only until seven weeks after the infusions. Therefore, the reduction of myeloma in BM was not detected at the beginning of the infusions, and even the proportion of plasma cells was increased. Although there was no obvious decrease in the plasma cell ratio of serial BM aspirates, cytoplasmic swelling and membrane budding of these cells, but not of other cell lineages, could be wildly observed in all patients receiving CART-138 therapy, possibly implying the existence of a CART-138 triggered immune attack on CD138 + cells. For patients with the SD response, these morphological changes, possibly induced by immune attack, appeared to be more consistent and wild. There are many possible explanations for the limited therapeutic antitumor activity observed in this trial. First, the high IgG level in blood of patients could have increased the blood viscosity, thereby affecting the CART cells. Second, an ineffective localization of the T cells to the tumor sites and inadequate transgene-encoded antigen surface expression could also affect the response of tumor cells to treatment. Third, the cytokine microenvironment in tumors may affect the function of CART [28,29].