Michael von Bergwelt-Baildon

The role of B cells in the pathogenesis of graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is an established treatment modality for malignant and nonmalignant hematologic diseases. Acute and chronic graft-versus-host diseases (GVHDs) are a major cause of morbidity and mortality after allogeneic stem cell transplantation. T cells have been identified as key players in the graft-versus-host reaction and, therefore, most established drugs used against GVHD target T cells. Despite our knowledge on the pathogenesis of the GVH reaction, success of established therapies for prevention and treatment of GHVD is unsatisfactory. Recently, animal and human studies demonstrated that B cells are involved in the immunopathophysiology of acute and chronic GVHD. Early phase clinical trials of B-cell depletion with rituximab have shown beneficial effects on both acute and chronic GVHD. This review summarizes the current experimental and clinical evidence for the involvement of B cells in the pathogenesis of acute and chronic GVHD and discusses the clinical implications for the management of patients undergoing allogeneic stem cell transplantation.

Trastuzumab emtansine (T-DM1) renders HER2+ breast cancer highly susceptible to CTLA-4/PD-1 blockade

An antibody-drug conjugate overcomes resistance to immune checkpoint blockade in HER2-positive breast cancer. Targeted therapy with more punch Overexpression of the human epidermal growth factor receptor 2 (HER2) is common in breast cancer, and it is associated with poor outcomes despite the availability of trastuzumab, an antibody against HER2, and other HER2-targeted agents. The reason for the poor outcomes is that many patients develop resistance to the targeted drugs. Müller et al. have now shown that this resistance can be overcome with trastuzumab emtansine, an antibody-drug conjugate that combines the HER2-targeting ability of trastuzumab with a cytotoxic drug, which the antibody delivers directly to the tumor. In addition to its cytotoxic effects, treatment with trastuzumab emtansine activated a strong antitumor immune response and effectively combined with immune checkpoint inhibitors, suggesting that it can be used in combination therapy. Targeted drug delivery with antibody-drug conjugates such as the HER2-directed ado-trastuzumab emtansine (T-DM1) has emerged as a powerful strategy for cancer therapy. We show that T-DM1 is particularly effective in eliciting antitumor immunity in patients with early breast cancer (WSG-ADAPT trial) and in a HER2-expressing orthotopic tumor model. In the latter, despite primary resistance to immunotherapy, combined treatment with T-DM1 and anti–CTLA-4/PD-1 (cytotoxic T lymphocyte–associated protein-4/programmed cell death protein-1) was curative because it triggered innate and adaptive immunity. Tumor rejection was accompanied by massive T cell infiltration, TH1 (T helper 1) cell polarization, and, notably, a substantial increase in regulatory T cells. Depletion of regulatory T cells resulted in inflammation and tissue damage, implying their essential role in protecting the host during therapy. This study provides insights into the mechanisms of T-DM1’s therapeutic activity and a rationale for potential therapeutic combination strategies with immunotherapy.

Mast cells play a protumorigenic role in primary cutaneous lymphoma

Primary cutaneous lymphomas (PCLs) are clonal T- or B-cell neoplasms, which originate in the skin. In recent years, mast cells were described as regulators of the tumor microenvironment in different human malignancies. Here, we investigated the role of mast cells in the tumor microenvironment of PCL. We found significantly increased numbers of mast cells in skin biopsies from patients with cutaneous T-cell lymphoma (CTCL) and cutaneous B-cell lymphoma (CBCL). Mast cell infiltration was particularly prominent in the periphery, at lymphoma rims. Interestingly, CTCL and CBCL patients with a progressive course showed higher mast cell counts than stable patients, and mast cell numbers in different stages of CTCL correlated positively with disease progression. In addition, mast cell numbers positively correlated with microvessel density. Incubating primary CTCL cells with mast cell supernatant, we observed enhanced proliferation and production of cytokines. In line with our in vitro experiments, in a mouse model of cutaneous lymphoma, tumor growth in mast cell-deficient transgenic mice was significantly decreased. Taken together, these experiments show that mast cells play a protumorigenic role in CTCL and CBCL. Our data provide a rationale for exploiting tumor-associated mast cells as a prognostic marker and therapeutic target in PCL.

O-Linked glycans control glycoprotein processing by antigen-presenting cells: a biochemical approach to the molecular aspects of MUC1 processing by dendritic cells

MUC1 is a glycoprotein overexpressed in breast cancer and other adenocarcinomas, and is known to elicit cellular and humoral immunity directed against unglycosylated peptide epitopes in the repeat domain. Based on immunological evidence that O‐linked glycans on repeat peptides remain intact during processing by dendritic cells (DC), we used MUC1 as a model to address the question which role O‐linked glycans play in this process. We were able to identify the sites of proteolysis in MUC1 repeats and the enzyme(s) involved, and elucidated the site‐specific effects of O‐glycosylation on MUC1 processing by human and mouse DC. Peptides generated by the cellular processing machinery from native mucin or (glyco)peptides suggest specific cleavage at Gly13‐Ser14, His20‐Gly1 and Thr3‐Ser4 peptide bonds in the tandem repeat GVTSAPDTRPAPGSTAPPAH resulting in the initial formation of STA27 or GVT20 and SAP17 as the final product with intact O‐glycosylation. Human cathepsin L and the corresponding mouse enzyme in low‐density endosomes were identified in vitro to catalyze this site‐specific MUC1 proteolysis. O‐Glycosylation controls the processing by preventing proteolysis of the Thr3‐Ser4 peptide bond if either amino acid is glycosylated, and is responsible for the inertness of tumor‐associated MUC1 glycoforms to effective DC processing by masking this cleavage site.

Microtubule-depolymerizing agents used in antibody-drug conjugates induce antitumor immunity by stimulation of dendritic cells.

Müller, Martin, von Bergwelt-Baildon, Zippelius, and colleagues show that the dolastatin family of microtubule inhibitors induced tumor-resident DC maturation and homing to draining lymph nodes to potentiate cellular antitumor immune responses, providing a rationale for combining dolastatin-based treatments with immunotherapy. Antibody–drug conjugates (ADC) are emerging as powerful treatment strategies with outstanding target-specificity and high therapeutic activity in patients with cancer. Brentuximab vedotin represents a first-in-class ADC directed against CD30+ malignancies. We hypothesized that its sustained clinical responses could be related to the stimulation of an anticancer immune response. In this study, we demonstrate that the dolastatin family of microtubule inhibitors, from which the cytotoxic component of brentuximab vedotin is derived, comprises potent inducers of phenotypic and functional dendritic cell (DC) maturation. In addition to the direct cytotoxic effect on tumor cells, dolastatins efficiently promoted antigen uptake and migration of tumor-resident DCs to the tumor-draining lymph nodes. Exposure of murine and human DCs to dolastatins significantly increased their capacity to prime T cells. Underlining the requirement of an intact host immune system for the full therapeutic benefit of dolastatins, the antitumor effect was far less pronounced in immunocompromised mice. We observed substantial therapeutic synergies when combining dolastatins with tumor antigen–specific vaccination or blockade of the PD-1–PD-L1 and CTLA-4 coinhibitory pathways. Ultimately, treatment with ADCs using dolastatins induces DC homing and activates cellular antitumor immune responses in patients. Our data reveal a novel mechanism of action for dolastatins and provide a strong rationale for clinical treatment regimens combining dolastatin-based therapies, such as brentuximab vedotin, with immune-based therapies. Cancer Immunol Res; 2(8); 741–55. ©2014 AACR.

Novel treatment concepts for graft-versus-host disease

Acute and chronic graft-versus-host disease (GVHD) are potentially lethal complications after stem cell transplantation (SCT). Steroids are the appropriate first-line treatment for both. However, if patients do not adequately benefit from steroid therapy, mortality is high and standardized treatment algorithms are lacking. This is mainly because of limited data from prospective, randomized clinical trials. In addition, most of the available treatment options only induce clinical benefits in a limited proportion of patients. Thus, there is an urgent clinical need to develop more potent immunosuppressive treatment strategies for patients suffering from acute or chronic steroid-refractory GVHD while maintaining the graft versus tumor effect to avoid a potential rise in relapse-related mortality. The increasing knowledge about host- as well as donor-derived variables favoring GVHD development and the increasing armamentarium of immune-modulatory agents entering preclinical and clinical research will probably allow more effective treatment of GVHD in the future. This review describes novel developments in the treatment of steroid-refractory GVHD, with a special focus on the rationale behind promising pharmacologic compounds or up-coming cellular therapies.

Is physical exercise possible in patients with critical cytopenia undergoing intensive chemotherapy for acute leukaemia or aggressive lymphoma

Patients undergoing intensive chemotherapy for acute leukaemia or aggressive lymphoma not only suffer from the direct side effects of chemotherapy such as infections due to long-lasting immuno-suppression and aplasia, but also from marked fatigue and the inability to do normal physical activity. Furthermore, especially in patients with severe thrombocytopenia, anaemia and leukopenia, doctors recommend abstaining from physical exercise due to the risk of potential bleeding and tissue damage. The normally recommended cutoff level to perform exercise is 50,000 platelets per microliter or haemoglobin of 8 g/dl. This leads to a vicious cycle of loosing physical strength and muscles with subsequent development of treatment-related cachexia and an increased treatment mortality. As number of publications focus on the importance of physical exercise in patients with solid tumours, increasing evidence is found that suggests positive effects on major clinical endpoints such as rate of infection, quality of life and even relapse rate and overall survival. With this work, we intended to address whether intense supervised ergometer training is feasible in patients with severe pancytopenia and whether it has any effect on patients undergoing high-dose chemotherapy. Furthermore, this study was initiated as the groundwork for a large phase III randomised trial.

Local Tumor Treatment in Combination with Systemic Ipilimumab Immunotherapy Prolongs Overall Survival in Patients with Advanced Malignant Melanoma.

Too few patients benefit from immune checkpoint inhibition alone. However, patients with melanoma receiving systemic anti-CTLA-4 plus localized treatments had significantly prolonged overall survival. In a multivariate analysis, adding local treatment was an independent factor for improved survival. Immune checkpoint inhibition with ipilimumab has revolutionized cancer immunotherapy and significantly improved outcomes of patients with advanced malignant melanoma. Local peripheral treatments (LPT), such as radiotherapy or electrochemotherapy, have been shown to modulate systemic immune responses, and preliminary data have raised the hypothesis that the combination of LPT with systemic immune checkpoint blockade might be beneficial. Clinical data from 127 consecutively treated melanoma patients at four cancer centers in Germany and Switzerland were analyzed. Patients received either ipilimumab (n = 82) or ipilimumab and additional LPT (n = 45) if indicated for local tumor control. The addition of LPT to ipilimumab significantly prolonged overall survival (OS; median OS 93 vs. 42 weeks, unadjusted HR, 0.46; P = 0.0028). Adverse immune-related events were not increased by the combination treatment, and LPT-induced local toxicities were in most cases mild. In a multivariable Cox regression analysis, we show that the effect of added LPT on OS remained statistically significant after adjusting for BRAF status, tumor stage, tumor burden, and central nervous system metastases (adjusted HR, 0.56; 95% confidence interval, 0.31–1.01, P = 0.05). Our data suggest that the addition of LPT to ipilimumab is safe and effective in patients with metastatic melanoma irrespective of clinical disease characteristics and known risk factors. Induction of antitumor immune responses is most likely the underlying mechanism and warrants prospective validation. Cancer Immunol Res; 4(9); 744–54. ©2016 AACR.

Viral antigen-specific CD8+ T-cell responses are impaired in multiple myeloma

Summary. Multiple myeloma (MM) is associated with defects of humoral and cellular immunity, however, little is known about the frequency and function of antigen‐specific CD8+ T cells. Such information might be critical for the development of immunotherapy for MM patients. As a model, we assessed the frequency and proliferation of CD8+ T cells specific for HLA‐A*0201‐restricted immunodominant epitopes from influenza A (Inf A) and Epstein–Barr virus (EBV). Experiments in identical twins demonstrated reduced numbers of antigen‐specific T cells after ex‐vivo antigenic challenge in the MM twin when compared with the healthy twin. Similarly, the proliferation and frequency of EBV‐ and Inf A‐specific T cells was also significantly reduced in a cohort of 24 previously untreated or conventionally treated MM patients when compared with 19 healthy individuals. In contrast, MM patients studied after receiving an autologous stem cell transplantation showed strikingly higher frequencies of EBV‐specific T cells with potential to proliferate ex vivo, suggesting that EBV‐specific T cells are readily expandable under these circumstances. These data identify an impaired response of CD8+ T cells in MM patients, which might in part explain the relatively limited success of anti‐MM immunisations. Prospective studies will determine whether such immune assessment strategies may identify patients more likely to benefit from cancer immunotherapy.

Comparison of bone marrow versus peripheral blood allogeneic hematopoietic stem cell transplantation for hematological malignancies in adults - a systematic review and meta-analysis.

It is still under debate whether bone marrow (BM) or peripheral blood (PB) should be the preferred stem cell source in adult patients undergoing allogeneic stem cell transplantation for hematological malignancies. After systematic literature search we identified nine randomised controlled trials comparing BM and PB as stem cell source from 2341 total hits. Meta-analysis involving 1521 patients showed a statistically significant reduction in overall and extensive chronic GvHD for patients transplanted with BM (HR 0.72; 95% CI 0.61 to 0.85 and HR 0.69; 95% CI 0.54 to 0.9), but no difference in overall and disease-free survival. In the related donor setting, data from two of eight studies demonstrated a significant increase of relapse incidence for BM (HR 2.73; 95% CI 1.47 to 5.08). This systematic review demonstrates that the current clinical standard to use peripheral blood stem cells instead of bone marrow for allo-SCT is not inferior with regard to the primary outcome overall survival.