T cells isolated from patients with checkpoint inhibitor-resistant melanoma are functional and can mediate tumor regression.

Background: Almost half of the patients with metastatic melanoma obtain only short-term or no benefit at all from checkpoint inhibitor (CPI) immunotherapy. In this study, we investigated whether the immune system of patients progressing following CPI treatment was able to generate functional tumor-specific immune responses. Materials and methods: Tumor-infiltrating lymphocytes (TILs) were isolated and expanded from metastatic melanoma lesions which progressed during or after anti-programmed cell death protein 1 (PD)-1 and anti-Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) treatment. Tumor-specific immune responses were assessed with co-culture assays of TILs and autologous tumor cells. Results: TILs from 23 metastases of individual patients could be assessed for T cells recognition of autologous tumor cells. All metastases were progressive on or following anti-PD-1 (23/23, 100%), and the majority also after anti-CTLA-4 (17/23, 74%). Functional antitumor immune responses were detected in 19/23 patients (83%). Both CD8+ (in 18/23 patients, 78%) and CD4+ (in 16/23 patients, 70%) TILs were able to recognize autologous tumors. A large fraction of CD8+ TILs (median 23%, range 1.0%-84%) recognized tumor cells. This is similar to the cohorts of unselected patient populations with metastatic melanoma presented in previous studies. The localization of intratumoral immune infiltrates was heterogeneous among samples. In a phase I/II clinical trial, TILs were administered with lymphodepleting chemotherapy, pegIFNα2b and interleukin-2 to 12 patients with CPI-resistant melanoma. Out of 12 patients who previously failed CPI therapy, treatment with TILs resulted in two partial responses, of which one is ongoing. Conclusions: Tumor-reactive T cells appear to heavily infiltrate the tumor microenvironment of patients who failed previous CPI treatment. These patients can still respond to an infusion of unselected autologous TILs. Our results warrant further testing of novel immune re-activation strategies in melanoma patients who failed multiple CPI therapy.

The calreticulin (CALR) exon 9 mutations are promising targets for cancer immune therapy.

The calreticulin (CALR) exon 9 mutations are found in ∼30% of patients with essential thrombocythemia and primary myelofibrosis. Recently, we reported spontaneous immune responses against the CALR mutations. Here, we describe that CALR-mutant (CALRmut)-specific T cells are able to specifically recognize CALRmut cells. First, we established a T-cell culture specific for a CALRmut epitope. These specific T cells were able to recognize several epitopes in the CALRmut C terminus. Next, we established a CALRmut-specific CD4+ T-cell clone by limiting dilution. These CD4+ T cells recognized autologous CALRmut monocytes and hematopoietic stem cells, and T-cell recognition of target cells was dependent on the presence of CALR. Furthermore, we showed that the CALRmut response was human leukocyte antigen (HLA)-DR restricted. Finally, we demonstrated that the CALRmut-specific CD4+ T cells, despite their phenotype, were cytotoxic to autologous CALRmut cells, and that the cytotoxicity was mediated by degranulation of the T cells. In conclusion, the CALR exon 9 mutations are targets for specific T cells and thus are promising targets for cancer immune therapy such as peptide vaccination in patients harboring CALR exon 9 mutations.

Cellular based cancer vaccines: type 1 polarization of dendritic cells.

Cancer vaccines designed to re-calibrate the existing host-tumour interaction, tipping the balance from tumor acceptance towards tumor control holds huge potential to complement traditional cancer therapies. In general, limited success has been achieved with vaccines composed of tumor-associated antigens introduced to dendritic cells (DCs) generated in vitro. This may in part result from suboptimal maturation of DCs leading to insufficient production of IL-12, a key driver of cellular immunity. Therefore, tremendous efforts have been put into the design of maturation cocktails that are able to induce IL-12 secreting type 1 polarized DCs mimicing pathogen-derived molecular activation of DCs. Correct timing and potential synergisms of clinical-grade toll-like receptor ligands, interferons (IFN) and CD40L enhance IL-12 production in DCs. However, cytokine exhaustion, predominant expression of tolerogenic molecules and activation-induced dendritic cell death should be avoided. Thus, compounds such as IFN-γ may initially induce immunity but later on tolerance. Maturation with PGE(2) obviously promotes migration via expression of CCR7 but on the down side PGE(2) limits the production of IL-12 especially following encounter with CD40L-expressing cells and furthermore, PGE(2) imprints DCs for preferential interaction with tolerogenic T cells. In addition, type 1 polarized DCs matured without PGE(2) also seem to be capable of migrating in vivo, although concomitant production of CCL19 seems to transiently affect in vitro migration via autocrine receptor-mediated endocytosis of CCR7. In the current review, we discuss optimal design of DC maturation focused on pre-clinical as well as clinical results from standard and polarized dendritic cell based cancer vaccines.

Immunobiological effects of glucosamine in vitro.

Glucosamine (GlcN) and N-acetyl-d-glucosamine (GlcNAc) were assayed in vitro for their effects on proliferation, cytotoxicity and cytokine secretion in primary and secondary mixed lymphocyte cultures (MLCs). In addition, we studied the effect of GlcN and GlcNAc on the proliferation of purified CD4+ T cells exposed to immobilized anti-CD3 antibody. The present data show that GlcN, but not GlcNAc, inhibits CD4+ T-cell proliferation, the generation of alloreactive cytotoxic T lymphocytes (CTLs) and the secretion of interferon-gamma (IFN-gamma) and interleukin-5 (IL-5) in primary MLC. In secondary T helper-2 (Th2)-polarized MLC, GlcN, but not GlcNAc, inhibits IL-4 and IL-5 secretion, whereas no effect was found on IFN-gamma secretion in Th1-polarized MLC. Dendritic cells treated with GlcN showed a 75-80% decreased capacity for antigen cross-presentation and allostimulation. In cellular bioassays, GlcN was shown to inhibit the stimulatory activity of IL-4 and IL-2, as well as the cytotoxic activity of tumour necrosis factor-alpha (TNF-alpha). In conclusion, GlcN suppresses unprimed T-cell responses by interfering with antigen-presenting cell functions and by a direct inhibitory effect on T-cell proliferation. In addition, GlcN inhibits the secretion of cytokines in antigen-stimulated unprimed T cells and primed Th2-polarized cells.