Suppression of Tregs by anti‐glucocorticoid induced TNF receptor antibody enhances the antitumor immunity of interferon‐α gene therapy for pancreatic cancer

We have reported that interferon (IFN)‐α can attack cancer cells by multiple antitumor mechanisms including the induction of direct cancer cell death and the enhancement of an immune response in several pancreatic cancer models. However, an immunotolerant microenvironment in the tumors is often responsible for the failure of the cancer immunotherapy. Here we examined whether the suppression of regulatory T cells (Tregs) within tumors can enhance an antitumor immunity induced by an intratumoral IFN‐α gene transfer. First we showed that an intraperitoneal administration of an agonistic anti‐glucocorticoid induced TNF receptor (GITR) monoclonal antibody (mAb), which is reported to suppress the function of Tregs, significantly inhibited subcutaneous tumor growth in a murine pancreatic cancer model. The anti‐GITR mAb was then combined with the intratumoral injection of the IFN‐α‐adenovirus vector. The treatment with the antibody synergistically augmented the antitumor effect of IFN‐α gene therapy not only in the vector‐injected tumors but also in the vector‐uninjected tumors. Immunostaining showed that the anti‐GITR mAb decreased Foxp3⁺ cells infiltrating in the tumors, while the intratumoral IFN‐α gene transfer increased CD4⁺ and CD8⁺ T cells in the tumors. Therefore, the combination therapy strongly inclined the immune balance of the tumor microenvironment in an antitumor direction, leading to a marked systemic antitumor effect. The CCR5 expression on Tregs was downregulated in the antibody‐treated mice, which may explain the decrease of tumor‐infiltrating Tregs. The combination of Treg‐suppression by GITR mAb and the tumor immunity induction by IFN‐α gene therapy could be a promising therapeutic strategy for pancreatic cancer.     

Reduction of Foxp3+ T cell subsets involved in incidence of chronic graft‐versus‐host disease after allogeneic hematopoietic stem cell transplantation

Foxp3+ T cells (CD4+ Tregs and CD8+ Treg) have been demonstrated to play roles in the maintenance of tolerance after allogeneic hematopoietic stem cell transplantation (Allo‐HSCT). We have found that Foxp3+ γδTCR+ Treg cells (γδTregs) exerted regulatory functions. In the current study, patients were recruited and divided as non‐cGVHD, limited cGVHD and extensive cGVHD groups. Healthy volunteers were recruited as healthy group. Treg cells were evaluated by flow cytometry. Serum cytokine levels of IL‐2, tumour necrosis factor‐α, interferon‐γ and transforming growth factor‐β1 (TGF‐β1) were evaluated by ELISA. The results showed that percentages of CD4+ Tregs, CD8+ Tregs and γδTregs were all significantly increased in non‐cGVHD group compared with those in healthy group, limited cGVHD group and extensive cGVHD group. Moreover, compared with extensive cGVHD group, percentages of these three types of Tregs were significantly increased in limited cGVHD group. The levels of TGF‐β1 increased dramatically in non‐cGVHD group compared with other groups. Spearman's correlation analysis revealed that the increased levels of TGF‐β1 and IL‐2 were positively associated with increased Treg subsets, indicating that TGF‐β1 and IL‐2 participated in the expansion process of Foxp3+ Tregs in vivo. Our findings support that increasing the number of Tregs following allo‐HSCT would be a preferential strategy for controlling cGVHD. Copyright © 2015 John Wiley & Sons, Ltd.     

Delayed platelet recovery after allogeneic hematopoietic stem cell transplantation: Association with chronic graft‐versus‐host disease and survival outcome

Delayed platelet recovery (DPR) despite prompt neutrophil engraftment is frequently observed after allogeneic hematopoietic stem cell transplantation (HSCT). However, few studies have evaluated the risk factors and long‐term outcome. Therefore, we retrospectively analysed 219 adult patients who underwent their first allogenic HSCT with neutrophil engraftment. Of these 219 patients, 50 (22.8%) had DPR that was defined as relapse‐free survival at day 60 after HSCT without primary platelet recovery despite neutrophil engraftment. The results of a multivariate analysis showed that a high‐risk underlying disease (odds ratio [OR], 2.38; 95% confidence interval [CI], 1.04‐5.48; P = .041) and human leukocyte antigen–mismatched HSCT (OR, 2.63; 95% CI, 1.28‐5.43; P = .009) were associated with an increased risk of DPR. In univariate analyses, the occurrence of DPR was significantly associated with inferior overall survival, high nonrelapse mortality, and a low incidence of chronic graft‐versus‐host disease (GVHD), despite a comparable relapse rate. In multivariate analyses, DPR was associated with inferior overall survival (hazard ratio [HR], 2.00; 95% CI, 1.23‐3.27; P = .005) and a low incidence of chronic GVHD (HR, 0.42; 95% CI, 0.22‐0.78; P = .002). In conclusion, DPR was a strong predictor of shorter survival but also less frequent chronic GVHD.     

Antitumor effect of novel anti‐podoplanin antibody NZ‐12 against malignant pleural mesothelioma in an orthotopic xenograft model

Podoplanin (aggrus) is highly expressed in several types of cancers, including malignant pleural mesothelioma (MPM). Previously, we developed a rat anti‐human podoplanin mAb, NZ‐1, and a rat–human chimeric anti‐human podoplanin antibody, NZ‐8, derived from NZ‐1, which induced antibody‐dependent cellular cytotoxicity (ADCC) and complement‐dependent cytotoxicity against podoplanin‐positive MPM cell lines. In this study, we showed the antitumor effect of NZ‐1, NZ‐8, and NZ‐12, a novel rat–human chimeric anti‐human podoplanin antibody derived from NZ‐1, in an MPM orthotopic xenograft SCID mouse model. Treatment with NZ‐1 and rat NK (CD161a⁺) cells inhibited the growth of tumors and the production of pleural effusion in NCI‐H290/PDPN or NCI‐H226 orthotopic xenograft mouse models. NZ‐8 and human natural killer (NK) (CD56⁺) cells also inhibited tumor growth and pleural effusion in MPM orthotopic xenograft mice. Furthermore, NZ‐12 induced potent ADCC mediated by human MNC, compared with either NZ‐1 or NZ‐8. Antitumor effects were observed following treatment with NZ‐12 and human NK (CD56⁺) cells in MPM orthotopic xenograft mice. In addition, combined immunotherapy using the ADCC activity of NZ‐12 mediated by human NK (CD56⁺) cells with pemetrexed, led to enhanced antitumor effects in MPM orthotopic xenograft mice. These results strongly suggest that combination therapy with podoplanin‐targeting immunotherapy using both NZ‐12 and pemetrexed might provide an efficacious therapeutic strategy for the treatment of MPM.     

IgG1 anti‐epidermal growth factor receptor antibodies induce CD8‐dependent antitumor activity

Anti‐EGFR monoclonal antibodies (mAb) like Cetuximab are commonly used for treatment of EGFR⁺ solid tumors mainly by exerting their therapeutic effect through inhibition of signal transduction. Additionally, IgG1 is a potent mediator of antibody‐dependent cytotoxicity (ADCC). In case of the IgG1, Cetuximab induction of ADCC in vivo is controversially discussed. In our study, we investigated the efficiency of Cetuximab‐mediated ADCC in a humanized mouse tumor model in vivo and analyzed the contribution of immunologic processes toward antitumor activity. Therefore, we used immunodeficient NOD/Scid mice transgenic for human MHC class I molecule HLA‐A2 and adoptively transferred human HLA‐A2⁺ PBMC after engraftment of human epidermoid cell carcinoma A431. Here, we show that high doses of anti‐EGFR mAb induced strong tumor regression independent of the immune system. However, tumor regression by low doses of anti‐EGFR mAb treatment was ADCC dependent and mediated by tumor infiltrating CD8⁺ T effector cells. This novel mechanism of ADCC conducted by CD8⁺ T effector cells was restricted to IgG1 anti‐EGFR mAb, dependent of binding to CD16 on T cells and could be inhibited after EGFR blockade on tumor cells. Furthermore, CD8⁺ T effector cell‐mediated ADCC was enhanced in the presence of IL‐15 and strongly improved after glycosylation of anti‐EGFR mAb indicating the potential of glycoengineered therapeutic mAb as efficient biologicals in cancer therapy.     

Blockade of TGF‐β enhances tumor vaccine efficacy mediated by CD8+ T cells

Though TGF‐β inhibition enhances antitumor immunity mediated by CD8⁺ T cells in several tumor models, it is not always sufficient for rejection of tumors. In this study, to maximize the antitumor effect of TGF‐β blockade, we tested the effect of anti‐TGF‐β combined with an irradiated tumor vaccine in a subcutaneous CT26 colon carcinoma tumor model. The irradiated tumor cell vaccine alone in prophylactic setting significantly delayed tumor growth, whereas anti‐TGF‐β antibodies alone did not show any antitumor effect. However, tumor growth was inhibited significantly more in vaccinated mice treated with anti‐TGF‐β antibodies compared to vaccinated mice without anti‐TGF‐β, suggesting that anti‐TGF‐β synergistically enhanced irradiated tumor vaccine efficacy. CD8⁺ T‐cell depletion completely abrogated the vaccine efficacy, and so protection required CD8⁺ T cells. Depletion of CD25⁺ T regulatory cells led to the almost complete rejection of tumors without the vaccine, whereas anti‐TGF‐β did not change the number of CD25⁺ T regulatory cells in unvaccinated and vaccinated mice. Though the abrogation of CD1d‐restricted NKT cells, which have been reported to induce TGF‐β production by MDSC through an IL‐13‐IL‐4R‐STAT6 pathway, partially enhanced antitumor immunity regardless of vaccination, abrogation of the NKT cell‐IL‐13‐IL‐4R‐STAT‐6 immunoregulatory pathway did not enhance vaccine efficacy. Taken together, these data indicated that anti‐TGF‐β enhances efficacy of a prophylactic vaccine in normal individuals despite their not having the elevated TGF‐β levels found in patients with cancer and that the effect is not dependent on TGF‐β solely from CD4⁺CD25⁺ T regulatory cells or the NKT cell‐IL‐13‐IL‐4R‐STAT‐6 immunoregulatory pathway.     

Intermittent chemotherapy can retain the therapeutic potential of anti‐CD137 antibody during the late tumor‐bearing state

Immunomodulating monoclonal antibodies (mAb) can evoke antitumor T‐cell responses, which are attenuated by regulatory T cells (Treg) and myeloid‐derived suppressor cells (MDSC). Treatment with cyclophosphamide (CP) and gemcitabine (GEM) can mitigate the immunosuppression by Treg and MDSC, respectively. In the current study, we examined the antitumor effects of a combination of local injection with anti‐CD137 mAb and intermittent low‐dose chemotherapy using CP and GEM in subcutaneously established CT26 colon carcinoma. Although a significant antitumor effect was observed when local anti‐CD137 mAb therapy (5 μg) was started early in the tumor‐bearing stage (day 10), no therapeutic efficacy was observed when the mAb therapy was started at a later tumor‐bearing stage (day 17). Analyses of the tumor‐infiltrating immune cells revealed that the number of Gr‐1^high/low CD11b⁺ MDSC started to increase 13 days after tumor inoculation, whereas injection with low‐dose (50 mg/kg) CP and GEM mitigated this increase. In addition, although intermittent injections with low‐dose CP and GEM on days 10 and 18 suppressed tumor growth significantly, additional local injections of anti‐CD137 mAb on days 19, 21, and 23 further augmented the therapeutic efficacy. Cytotoxic T lymphocytes reactive to CT26 and a tumor antigen peptide were induced successfully from the spleen cells of tumor‐cured or tumor‐stable mice. In a bilateral tumor inoculation model, this combination therapy achieved systemic therapeutic effects and suppressed the growth of mAb‐untreated tumors. These results suggest that intermittent immunochemotherapy using CP and GEM could retain the therapeutic potential of anti‐CD137 mAb that is normally impaired during the late tumor‐bearing stage.     

Chimeric antigen receptor‐engineered cytokine‐induced killer cells overcome treatment resistance of pre‐B‐cell acute lymphoblastic leukemia and enhance survival

Pre‐emptive cancer immunotherapy by donor lymphocyte infusion (DLI) using cytokine‐induced killer (CIK) cells may be beneficial to prevent relapse with a reduced risk of causing graft‐versus‐host‐disease. CIK cells are a heterogeneous effector cell population including T cells (CD3⁺ CD56^?), natural killer (NK) cells (CD3^?CD56⁺) and natural killer T (T‐NK) cells (CD3⁺ CD56⁺) that exhibit non‐major histocompatibility complex (MHC)‐restricted cytotoxicity and are generated by ex vivo expansion of peripheral blood mononuclear cells in the presence of interferon (IFN)‐γ, anti‐CD3 antibody, interleukin‐2 (IL‐2) and interleukin‐15 (IL‐15). To facilitate selective target‐cell recognition and enhance specific cytotoxicity against B‐cell acute lymphoblastic leukemia (B‐ALL), we transduced CIK cells with a lentiviral vector encoding a chimeric antigen receptor (CAR) that carries a composite CD28‐CD3ζ domain for signaling and a CD19‐specific scFv antibody fragment for cell binding (CAR 63.28.z). In vitro analysis revealed high and specific cell killing activity of CD19‐targeted CIK/63.28.z cells against otherwise CIK‐resistant cancer cell lines and primary B‐ALL blasts, which was dependent on CD19 expression and CAR signaling. In a xenograft model in immunodeficient mice, treatment with CIK/63.28.z cells in contrast to therapy with unmodified CIK cells resulted in complete and durable molecular remissions of established primary pre‐B‐ALL. Our results demonstrate potent antileukemic activity of CAR‐engineered CIK cells in vitro and in vivo, and suggest this strategy as a promising approach for adoptive immunotherapy of refractory pre‐B‐ALL.     

Intratumoral COX‐2 inhibition enhances GM‐CSF immunotherapy against established mouse GL261 brain tumors

Immunotherapy has shown effectiveness against experimental malignant brain tumors, but the clinical results have been less convincing most likely due to immunosuppression. Prostaglandin E₂ (PGE₂) is the key immunosuppressive product of cyclooxygenase‐2 (COX‐2) and increased levels of PGE₂ and COX‐2 have been shown in several tumor types, including brain tumors. In the current study, we report enhanced cure rate of mice with established mouse GL261 brain tumors when immunized with granulocyte macrophage‐colony stimulating factor (GM‐CSF) secreting tumor cells and simultaneously treated with the selective COX‐2 inhibitors parecoxib systemically (5 mg/kg/day; 69% cure rate) or valdecoxib intratumorally (5.3 µg/kg/day; 63% cure rate). Both combined therapies induced a systemic antitumor response of proliferating CD4⁺ and CD8⁺ T cells, and further analysis revealed T helper 1 (T_h1) cell supremacy. The GL261 tumor cell line produced low levels of PGE₂ in vitro, and co‐staining at the tumor site demonstrated that a large fraction of the COX‐2⁺ cells were derived from CD45⁺ immune cells and more specifically macrophages (F4/80⁺), indicating that tumor‐infiltrating immune cells constitute the primary source of COX‐2 and PGE₂ in this model. We conclude that intratumoral COX‐2 inhibition potentiates GM‐CSF immunotherapy against established brain tumors at substantially lower doses than systemic administration. These findings underscore the central role of targeting COX‐2 during immunotherapy and implicate intratumoral COX‐2 as the primary target.     

CIITA‐driven MHC‐II positive tumor cells: Preventive vaccines and superior generators of antitumor CD4+ T lymphocytes for immunotherapy

In our study, we have investigated whether tumors of distinct histological origin can be rejected if expressing CIITA‐driven MHC class II molecules. Moreover, we assessed whether antitumor lymphocytes generated by this approach could be used as an immunotherapeutic tool for established cancers. Stable CIITA‐transfectants of C51colon adenocarcinoma, RENCA renal adenocarcinoma, WEHI‐164 sarcoma as well as TS/A mammary adenocarcinoma were generated. Tumor cells transfectants were injected in vivo, and their growth kinetics and recipient's immune response were analyzed. Tumor rejection and/or retardation of growth was found for the first 3 CIITA‐transfected tumor cell lines and confirmed for TS/A‐CIITA. Animals rejecting CIITA‐transfected tumors acquired specific immunological memory as demonstrated by resistance to challenge with parental tumors. Adoptive cell transfer experiments demonstrated that tumor immunity correlates with the efficient priming of CD4⁺ T helper cells and the consequent activation of CD8⁺ T lymphocytes. T cells from TS/A‐vaccinated mice were used in an adoptive immunotherapy model of established tumors. The results showed the cure at early stages and significantly prolonged survival at later stages of tumor progression. Importantly, CD4⁺ T cells were clearly superior to CD8⁺ T cells in antitumor protective function. Interestingly, the protective phenotype was associated to both a Th1 and Th2 polarization of the immune effectors. These results establish the general application of our tumor vaccine model and disclose the additional application of this strategy for producing better lymphocyte effectors for adoptive antitumor immunotherapy.     

Humanized anti‐CD19 chimeric antigen receptor‐T cell therapy is safe and effective in lymphoma and leukemia patients with chronic and resolved hepatitis B virus infection

Chimeric antigen receptor‐T (CAR‐T) cell therapy is a promising treatment for CD19⁺ B‐cell malignancies. However, elimination of B cells by anti‐CD19 CAR‐T cells may lead to the reactivation of hepatitis B virus (HBV) and related hepatitis in patients with HBV infection. This study aims to evaluate the safety and efficacy of humanized anti‐CD19 CAR‐T (hCAR‐T) therapy in B‐cell malignancies with HBV infection. Twenty relapsed/refractory (r/r) diffuse large B‐cell lymphoma (DLBCL) and acute lymphoblastic leukemia (ALL) patients with HBV infection were treated with hCAR‐T therapy. Among them, five hepatitis B antigen‐positive patients who received antiviral prophylaxis did not develop HBV reactivation, including two patients who received both hCAR‐T and allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Among 15 patients with resolved HBV infection, two received antiviral prophylaxis, and the other 13 did not experience HBV reactivation without antiviral prophylaxis. One patient with resolved HBV infection experienced HBV reactivation 6 months after hCAR‐T therapy and sequential allo‐HSCT. Moreover, HBV infection did not affect in vivo expansion of hCAR‐T cells or increase the risk of severe cytokine release syndrome. In conclusion, hCAR‐T therapy is safe and effective in DLBCL and ALL patients with chronic and resolved HBV infection under proper antiviral prophylaxis.     

Peptide inhibitors of transforming growth factor‐β enhance the efficacy of antitumor immunotherapy

Transforming growth factor‐β (TGF‐β) is a cytokine with potent immunosuppressive effects and is overexpressed in many tumors. Therefore, development of molecules able to inhibit TGF‐β is of paramount importance to improve the efficacy of antitumor immunotherapy. TGF‐β inhibitor peptides P144 and P17 were combined with the administration of adjuvant molecules poly(I:C) and agonistic anti‐CD40 antibodies, and their effect on the growth of E.G7‐OVA established tumors and on antitumor immune response was evaluated. Tumor rejection efficacy of a single administration of adjuvants was enhanced from 15 to 70 % when combined with repeated injections of TGF‐β inhibitor peptides. Simultaneous administration of adjuvants and TGF‐β inhibitor peptides was required for maximal therapeutic efficacy. Although tumor cells produced TGF‐β, it was found that the beneficial effect of peptide administration was mainly due to the inhibition of TGF‐β produced by regulatory CD4⁺CD25⁺ T cells rather than by tumor cells. The enhanced antitumor effect was accompanied by a higher activity of dendritic cells, natural killer cells and tumor antigen‐specific T cells, as well as by a decrease in the number of myeloid‐derived suppressor cells. In conclusion, administration of peptide inhibitors of TGF‐β in therapeutic vaccination enhances the efficacy of immunotherapy by increasing antitumor immune responses. These peptide inhibitors may have important applications for current immunotherapeutic strategies. © 2009 UICC     

The outcome and characteristics of patients with relapsed adult T cell leukemia/lymphoma after allogeneic hematopoietic stem cell transplantation

Treatment options for patients with adult T cell leukemia/lymphoma (ATLL) who have relapsed disease after allogeneic hematopoietic stem cell transplantation (allo‐HSCT) are limited. To clarify which patients with ATLL are likely to benefit from these treatment options and to define patient populations for novel treatments, we performed a nationwide retrospective analysis of 252 Japanese patients who had relapsed ATLL after allo‐HSCT. Some long‐term survivors remained after tapering and withdrawal of immunosuppressive agents. Thirty‐six patients who received donor lymphocyte infusion had a better overall survival (OS) in comparison to those who did not [hazard ratio (HR), 0.63; 95% confidence interval (CI), 0.43‐0.93; P = .02], suggesting the efficacy of a graft‐versus‐ATLL (GvATLL) effect even after relapse. Multivariate analysis demonstrated that skin lesions at initial relapse of ATLL were independently associated with higher OS (HR, 0.41; 95% CI, 0.22‐0.74; P = .003), indicating that the skin is a susceptible target organ of GvATLL. This study suggested that enhancement of a GvATLL effect is a potential therapeutic option for relapsed disease after allo‐HSCT. Further investigations of incorporation of immune‐based approaches with new molecular target drugs into the therapeutic options of patients with ATLL before and after transplantation are warranted.     

Contrasting effects of cyclophosphamide on anti‐CTL‐associated protein 4 blockade therapy in two mouse tumor models

Immune checkpoint blockade is a promising anticancer therapy, but must be used in combination with other anticancer therapies to increase its therapeutic efficacy. Cyclophosphamide (CP) is a chemotherapeutic drug that shows immune‐modulating effects. In this study, we examined the effect of CP on anti‐CTL‐associated protein 4 (CTLA‐4) blockade therapy in two mouse tumor models. Drastic tumor regression was observed in the CT26 colon carcinoma model after i.p. injection of CP (100 mg/kg) followed by anti‐CTLA‐4 antibody. However, administration in the reverse order increased apoptosis in tumor‐specific CD8⁺ T cells. In the RENCA renal carcinoma model, the antitumor effect of combination therapy was marginal and the tumor‐bearing state reduced body weight with an increased serum level of interleukin‐6. Interestingly, although CP monotherapy increased myeloid‐derived suppressor cells (MDSCs) in the spleens of both models, subsequent anti‐CTLA‐4 therapy increased MDSCs only in RENCA‐bearing mice. Additionally, the serum levels of chemokine ligand 2 and C‐X‐C motif chemokine 10 were increased by the combination therapy only in RENCA‐bearing mice and in vivo depletion of Gr‐1⁺ cells augmented the antitumor effect to some degree. These results reveal a contrasting effect of CP on anti‐CTLA‐4 therapy between the two mouse tumor models. Cyclophosphamide augments the antitumor effect of anti‐CTLA‐4 therapy in CT26‐bearing hosts, whereas CP after anti‐CTLA‐4 therapy attenuates this effect through induction of apoptosis in tumor‐reactive T cells. Alternatively, CP‐induced MDSCs can be increased by anti‐CTLA‐4 therapy only in RENCA‐bearing hosts with an elevated level of interleukin‐6.     

Vaccine immunotherapy with ARNAX induces tumor‐specific memory T cells and durable anti‐tumor immunity in mouse models

Immunological checkpoint blockade therapies benefit a limited population of cancer patients. We have previously shown that vaccine immunotherapy with Toll‐like receptor (TLR)3‐adjuvant and tumor antigen overcomes anti‐programmed death ligand‐1 (PD‐L1) resistance in mouse tumor models. In the present study, 4 different ovalbumin (OVA)‐expressing tumor cell lines were implanted into syngeneic mice and subjected to anti‐tumor immunotherapy using ARNAX and whole OVA protein. ARNAX is a TLR3‐specific agonist that does not activate the mitochondrial antiviral‐signaling protein (MAVS) pathway, and thus does not induce systemic inflammation. Dendritic cell priming and proliferative CTL were induced by ARNAX + OVA, but complete remission was achieved only in a PD‐L1‐low cell line of EG7. Addition of anti‐PD‐L1 antibody to the ARNAX + OVA therapy brought complete remission to another PD‐L1‐high subline of EG7. Tumor shrinkage but not remission was observed in MO5 in that regimen. We analyzed tumor cells and tumor‐infiltrating immune cells to identify factors associated with successful ARNAX vaccine therapy. Tumors that responded to ARNAX therapy expressed high levels of MHC class I and low levels of PD‐L1. The tumor‐infiltrating immune cells in ARNAX‐susceptible tumors contained fewer immunosuppressive myeloid cells with low PD‐L1 expression. Combination with anti‐PD‐L1 antibody functioned not only within tumor sites but also within lymphoid tissues, augmenting the therapeutic efficacy of the ARNAX vaccine. Notably, ARNAX therapy induced memory CD8⁺ T cells and rejection of reimplanted tumors. Thus, ARNAX vaccine + anti‐PD‐L1 therapy enabled permanent remission against some tumors that stably present antigens.     

Cancer‐associated fibroblast‐targeted strategy enhances antitumor immune responses in dendritic cell‐based vaccine

Given the close interaction between tumor cells and stromal cells in the tumor microenvironment (TME), TME‐targeted strategies would be promising for developing integrated cancer immunotherapy. Cancer‐associated fibroblasts (CAFs) are the dominant stromal component, playing critical roles in generation of the pro‐tumorigenic TME. We focused on the immunosuppressive trait of CAFs, and systematically explored the alteration of tumor‐associated immune responses by CAF‐targeted therapy. C57BL/6 mice s.c. bearing syngeneic E.G7 lymphoma, LLC1 Lewis lung cancer, or B16F1 melanoma were treated with an anti‐fibrotic agent, tranilast, to inhibit CAF function. The infiltration of immune suppressor cell types, including regulatory T cells and myeloid‐derived suppressor cells, in the TME was effectively decreased through reduction of stromal cell‐derived factor‐1, prostaglandin E₂, and transforming growth factor‐β. In tumor‐draining lymph nodes, these immune suppressor cell types were significantly decreased, leading to activation of tumor‐associated antigen‐specific CD8⁺ T cells. In addition, CAF‐targeted therapy synergistically enhanced multiple types of systemic antitumor immune responses such as the cytotoxic CD8⁺ T cell response, natural killer activity, and antitumor humoral immunity in combination with dendritic cell‐based vaccines; however, the suppressive effect on tumor growth was not observed in tumor‐bearing SCID mice. These data indicate that systemic antitumor immune responses by various immunologic cell types are required to bring out the efficacy of CAF‐targeted therapy, and these effects are enhanced when combined with effector‐stimulatory immunotherapy such as dendritic cell‐based vaccines. Our mouse model provides a novel rationale with TME‐targeted strategy for the development of cell‐based cancer immunotherapy.     

Novel cucurmosin‐based immunotoxin targeting programmed cell death 1‐ligand 1 with high potency against human tumor in vitro and in vivo

Immunotoxins are Ab‐cytotoxin chimeric molecules with mighty cytotoxicity. Programmed cell death 1‐ligand 1 (PD‐L1), is a transmembrane protein expressed mainly in inflammatory tumor tissues and plays a pivotal role in immune escape and tumor progression. Although PD‐L1 immune checkpoint therapy has been successful in some cases, many patients have not benefited enough due to primary/secondary resistance. In order to optimize the therapeutic efficacy of anti‐PD‐L1 mAb, we used durvalumab as the payload and CUS_245C, a type I ribosome‐inactivating protein isolated from Cucurbita moschata, as the toxin moiety, to construct PD‐L1‐specific immunotoxin (named D‐CUS_245C) through the engineered cysteine residue. In vitro, D‐CUS_245C selectively killed PD‐L1⁺ tumor cells. In vivo studies also showed that D‐CUS_245C had obvious antitumor effect on PD‐L1⁺ human xenograft tumors in nude mice. In conclusion, in the combination of the toxin with mAb, this study developed a new immunotoxin targeting PD‐L1, emphasizing a novel and promising treatment strategy and providing a valuable way to optimize cancer immunotherapy.     

Resveratrol ameliorates Lewis lung carcinoma‐bearing mice development,decreases granulocytic myeloid‐derived suppressor cell accumulation and impairs its suppressive ability

Myeloid‐derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells which consist of 2 subsets: granulocytic MDSC (G‐MDSC) and monocytic MDSC (M‐MDSC). MDSC expand in tumor‐bearing hosts and contribute to immunotherapeutic resistance by remarkably blocking effector T‐cell activation via different mechanisms. Resveratrol (RSV) is a polyphenol and it has been widely used for its various health benefits. However, the underlying mechanism of its anti‐tumor properties remains unclear. In this study, a transplantable mouse model was used to investigate the effects of RSV on MDSC. The results showed that RSV ameliorated tumor development by decreasing G‐MDSC accumulation, impairing its suppressive ability on CD8⁺T cells and promoting M‐MDSC differentiation into CD11c⁺ and F4/80⁺ cells. Our results indicated that RSV should be considered as a modular of MDSC suppressive function and that RSV is a novel booster for tumor immunotherapy.     

CD40‐independent natural killer‐cell help promotes dendritic cell vaccine‐induced T‐cell immunity against endogenous B‐cell lymphoma

It is well established that an interplay between natural killer (NK) cells and dendritic cells (DCs) gives rise to their reciprocal activation and provides a Th1‐biased cytokine milieu that fosters antitumor T‐cell responses. Ex vivo‐differentiated DCs transferred into mice strongly stimulate endogenous NK cells to produce interferon (IFN)‐γ and initiate a cascade that eventually leads to cytotoxic T‐lymphocyte responses. We show that the ability of exogenous DCs to trigger this pathway obviates CD40 signaling and CD4⁺ T‐cell help and depends on a preceding maturation step. Importantly, this mechanism was also effective in endogenously arising tumors where IFN‐γ production is compromised in contrast to transplantable tumors. In c‐myc‐transgenic mice developing spontaneous lymphomas, injection of unpulsed DCs caused NK‐cell activation and induced CD8⁺ T cells capable of recognizing the lymphoma cells. Animals treated with unpulsed DCs showed a survival benefit compared to untreated myc mice. Hence, tumor immunity induced by DC‐based vaccines not only depends on specific antigens loaded on the DCs. Rather, DC vaccines generate broader immune responses, because endogenous DCs presenting tumor antigens may also become stimulated by NK cells that were activated by exogenous DCs. Thus, the DC/NK‐cell/cytotoxic T lymphocyte axis may commonly have relevance for DC‐based vaccination protocols in clinical settings.     

Outcomes of second hematopoietic stem cell transplantation using reduced‐intensity conditioning in an outpatient setting

Relapse and graft failure after autologous (auto) or allogeneic (allo) hematopoietic stem cell transplantation (HSCT) are serious and frequently fatal events. A second HSCT can be a life‐saving alternative, however, information on the results of such intervention in an outpatient setting is limited. Outpatient second hematoprogenitors transplant after reduced‐intensity conditioning (RIC) at a single academic center was analyzed. Twenty‐seven consecutive adults who received an allo‐HSCT after an initial auto‐ or allo‐HSCT from 2006 to 2019 were included. Data were compared using the χ²‐test. Survival analysis using Kaplan–Meier and Cox proportional hazard models was performed; cumulative incidence estimation of transplant‐related mortality (TRM) was assessed. Hodgkin lymphoma was the most frequent diagnosis for the group with a first auto‐HSCT with 5/12 (41.7%) cases, and acute myeloid leukemia for those with a first allo‐HSCT with 6/15 (40%). One‐year overall survival and disease‐free survival (DFS) was 66.7% (95% CI 27.2–88.2) and 59% (95% CI 16–86) for 12 patients with a first auto‐HSCT; and for 15 patients with a first allo‐HSCT, it was 43.3% (95% CI 17.9–66.5) and 36% (95% CI 13.2–59.9), respectively. Eight (29.6%) patients died of TRM and the cumulative incidence of TRM at 1 year was 22% (95% CI 8.6–39.27). Chronic graft‐versus‐host disease and late (>10 months) second transplantation were protective factors for longer survival. Neutropenic fever was more common in the group with a first allo‐HSCT (p = 0.01). In conclusion, outpatient second allo‐HSCT using RIC after auto‐ or allografting failure or relapse is feasible and offers a reasonable alternative for patients with severe life‐threatening hematological diseases.