Elevated baseline serum PD-1 or PD-L1 predicts poor outcome of PD-1 inhibition therapy in metastatic melanoma

BACKGROUND

Programmed cell death protein 1 (PD-1) checkpoint inhibition has recently advanced to one of the most effective treatment strategies in melanoma. Nevertheless, a considerable proportion of patients show upfront therapy resistance and baseline predictive biomarkers of treatment outcome are scarce. In this study we quantified PD-1 and programmed death-ligand 1 (PD-L1) in baseline sera from melanoma patients in relation to therapy response and survival.

PATIENTS AND METHODS

Sera taken at therapy baseline from a total of 222 metastatic melanoma patients (two retrospectively selected monocentric discovery cohorts, n = 130; one prospectively collected multicentric validation cohort, n = 92) and from 38 healthy controls were analyzed for PD-1 and PD-L1 concentration by sandwich enzyme-linked immunosorbent assay.

RESULTS

Melanoma patients showed higher serum concentrations of PD-1 (P = 0.0054) and PD-L1 (P < 0.0001) than healthy controls. Elevated serum PD-1 and PD-L1 levels at treatment baseline were associated with an impaired best overall response (BOR) to anti-PD-1 (P = 0.014, P = 0.041), but not to BRAF inhibition therapy. Baseline PD-1 and PD-L1 serum levels correlated with progression-free (PFS; P = 0.0081, P = 0.053) and overall survival (OS; P = 0.055, P = 0.0062) in patients who received anti-PD-1 therapy, but not in patients treated with BRAF inhibitors. By combining both markers, we obtained a strong discrimination between favorable and poor outcome of anti-PD-1 therapy, with elevated baseline serum levels of PD-1 and/or PD-L1 associated with an impaired BOR (P = 0.037), PFS (P = 0.048), and OS (P = 0.0098). This PD-1/PD-L1 combination serum biomarker was confirmed in an independent multicenter validation set of serum samples prospectively collected at baseline of PD-1 inhibition (BOR, P = 0.019; PFS, P = 0.038; OS, P = 0.022). Multivariable Cox regression demonstrated serum PD-1/PD-L1 as an independent predictor of PFS (P = 0.010) and OS (P = 0.003) in patients treated with PD-1 inhibitors.

CONCLUSION

Our findings indicate PD-1 and PD-L1 as useful serum biomarkers to predict the outcome of PD-1 inhibition therapy in melanoma patients and to select patients for PD-1-based versus BRAF-based therapy strategies.

Differential influence of vemurafenib and dabrafenib on patients' lymphocytes despite similar clinical efficacy in melanoma

BACKGROUND

Since the majority of melanomas eventually become resistant and progress, combining selective BRAF inhibitors (BRAFi) with immunotherapies has been proposed to achieve more durable treatment responses. Here, we explored the impact of selective BRAFi on the hosts' immune system.

PATIENTS AND METHODS

Clinical data, whole blood counts (WBC) and serum lactate dehydrogenase (LDH) of 277 vemurafenib- and 65 dabrafenib-treated melanoma patients were evaluated. The frequency and phenotype of lymphocyte subpopulations were determined by flow cytometry while T cell cytokine secretion was measured by multiplex assays.

RESULTS

Progression-free survival (PFS) as well as overall survival (OS) were similar in patients treated with either BRAFi. High pretreatment LDH was associated with shorter PFS and OS in both groups. During therapy, peripheral lymphocytes decreased by 24.3% (median, P < 0.0001) in vemurafenib-treated patients but remained unchanged in dabrafenib-treated patients (+1.2%, P = 0.717). Differentiation of peripheral lymphocytes of vemurafenib-treated patients showed a significant decrease in CD4(+) T cells (P < 0.05). Within CD4(+) T cells obtained during treatment, an increase in CCR7(+)CD45RA(+) (naïve) and a decrease in CCR7(+)CD45RA(-) (central memory) populations were found (P < 0.01 for both). Furthermore, secretion of interferon-γ and interleukin-9 by CD4(+) T cells was significantly lower in samples obtained during vemurafenib treatment compared with baseline samples.

CONCLUSION

While both compounds have comparable clinical efficacy, vemurafenib but not dabrafenib decreases patients peripheral lymphocyte counts and alters CD4(+) T cell phenotype and function. Thus, selective BRAFi can significantly affect patients' peripheral lymphocyte populations. Fully understanding these effects could be critical for successfully implementing combinatorial therapies of BRAFi with immunomodulatory agents.

Efficient recovery of HLA class I expression in human tumor cells after beta2-microglobulin gene transfer using adenoviral vector: implications for cancer immunotherapy

Here we report a successful use of a non-replicating adenovirus expressing the wild-type human beta2m gene in recovery of normal human leucocyte antigen (HLA) class I expression in beta2m-null cancer cells. Total loss of HLA class I expression in these cell lines is caused by a mutation in beta2m gene and a loss of heterozygosity in chromosome 15 carrying another copy of that gene. Normal HLA class I expression on the tumour cell surface is critical for the successful outcome of cancer immunotherapy as T cells can only recognize tumour-derived peptides in a complex with self-HLA class I molecules. In this report we characterize the newly generated adenoviral vector AdCMVbeta2m and demonstrate an efficient beta2m gene transfer in tumour cell lines of different histological origin, including melanoma, prostate and colorectal carcinoma. The beta2m re-expression lasted for an extended period of time both in vitro and in vivo in human tumour xenograft transplants. We propose that in a subset of cancer patients with structural defect in beta2m gene or chromosome 15, the adenoviral-mediated recovery (or even increase) of HLA class I expression on tumour cells in combination with vaccination or adoptive T-cell therapy can provide a complementary approach to improve the clinical efficacy of cancer immunotherapy.

The CIMT-monitoring panel: a two-step approach to harmonize the enumeration of antigen-specific CD8+ T lymphocytes by structural and functional assays

The interpretation of the results obtained from immunomonitoring of clinical trials is a difficult task due to the variety of methods and protocols available to detect vaccine-specific T-cell responses. This heterogeneity as well as the lack of standards has led to significant scepticism towards published results. In February 2005, a working group was therefore founded under the aegis of the Association for Immunotherapy of Cancer ("CIMT") in order to compare techniques and protocols applied for the enumeration of antigen-specific T-cell responses. Here we present the results from two consecutive phases of an international inter-laboratory testing project referred to as the "CIMT monitoring panel". A total of 13 centers from six European countries participated in the study in which pre-tested PBMC samples, synthetic peptides and PE-conjugated HLA-tetramers were prepared centrally and distributed to participants. All were asked to determine the number of antigen-specific T-cells in each sample using tetramer staining and one functional assay. The results of the first testing round revealed that the total number of cells analyzed was the most important determinant for the sensitive detection of antigen-specific CD8(+) T-cells by tetramer staining. Analysis by ELISPOT was influenced by a combination of cell number and a resting phase after thawing of peripheral blood mononuclear cells. Therefore, the experiments were repeated in a second phase but now the participants were asked to change their protocols according to the new guidelines distilled from the results of the first phase. The recommendations improved the number of antigen-specific T-cell responses that were detected and decreased the variability between the laboratories. We conclude that a two-step approach in inter-laboratory testing allows the identification of distinct variables that influence the sensitivity of different T-cell assays and to formally show that a defined correction to the protocols successfully increases the sensitivity and reduces the inter-center variability. Such "two-step" inter-laboratory projects could define rational bases for accepted international guidelines and thereby lead to the harmonization of the techniques used for immune monitoring.

Impact of a functional polymorphism in the IL12B promoter region on survival in patients with malignant melanoma

8001

Background: Interleukin-12 (IL-12), a heterodimeric cytokine, is important in the generation of a Th1-biased immune response. Several polymorphisms have been described in IL12B, the gene encoding the p40 subunit of IL-12. A bi-allelic polymorphism within the IL12B promoter region has been reported to show association with diseases as diverse as severe childhood asthma and fatal cerebral malaria. Methods: In order to define the molecular basis for these disease associations we investigated the secretion of IL-12 by human monocyte-derived dendritic cells. The amount of IL-12p40 and p70 produced by DCs from normal blood donors was determined following CD40L activation. Subsequently, we therefore sought to investigate the frequency of IL12B genotypes and their impact on the outcome of patients with malignant melanoma. Genomic DNA was isolated from 75 normal blood donors and 80 melanoma cell lines and used for genotyping the IL12B polymorphism. Corresponding clinical data were retrieved from the in-house melanoma database. Results: Allele frequency for IL12Bpro-1 is 0.45 and for IL12Bpro-2 0.55. Homozygotes for the IL12B promoter polymorphism showed a 10-fold difference in median p70 secretion in response to CD40 ligation. Remarkably, this difference resulted from the inability of most allele 1 homozygotes to secrete heterodimeric IL-12. In contrast, most of the donors homozygous for allele 2 had detectable secretion. Distribution of genotypes in melanoma patients was not significantly different from normal blood donors. Kaplan-Meier survival analysis showed significantly decreased survival of patients homozygous for the longer allele, previously defined as being associated with decreased IL-12 secretion (log-rank p=0.015). Subgroup analysis indicated that this survival advantage was seen exclusively in female patients. Conclusions: The recently described IL12B promoter polymorphism is highly correlated with secretion of bioactive IL-12 and has a significant impact on the clinical course of disease in patients with melanoma and may therefore be useful for prognostic stratification.

No significant financial relationships to disclose.

Deficient IL-12p70 secretion by dendritic cells based on IL12B promoter genotype

Interleukin-12 (IL-12), a heterodimeric cytokine, is important in the generation of a Th1-biased immune response. Several polymorphisms have been described in IL12B, the gene encoding the p40 subunit of IL-12. A bi-allelic polymorphism within the IL12B promoter region has been reported to show association with diseases as diverse as severe childhood asthma and fatal cerebral malaria. In order to define the molecular basis for these disease associations, we investigated the secretion of IL-12 by human monocyte-derived dendritic cells. Homozygotes for the IL12B promoter polymorphism showed a 10-fold difference in median p70 secretion in response to CD40 ligation. Remarkably, this difference resulted from the inability of most allele 1 homozygotes to secrete heterodimeric IL-12. In contrast, most of the donors homozygous for allele 2 had detectable secretion. These findings are important for the understanding of the highly complex regulation of IL-12 secretion, and its consequent impact on disease susceptibility, in humans.

Rhodobacter capsulatus nifA mutants mediating nif gene expression in the presence of ammonium

Expression of nitrogen fixation genes in Rhodobacter capsulatus is repressed by ammonium at different regulatory levels including an NtrC-independent mechanism controlling NifA activity. In contrast to R. capsulatus NifA, heterologous NifA proteins of Klebsiella pneumoniae and Rhizobium meliloti, respectively, were not subjected to this posttranslational ammonium control in R. capsulatus. The characterization of ammonium-tolerant R. capsulatus NifA1 mutants indicated that the N-terminal domain of NifA was involved in posttranslational regulation. Analysis of a double mutant carrying amino acid substitutions in both the N-terminal domain and the C-terminal DNA-binding domain gave rise to the hypothesis that an interaction between these two domains might be involved in ammonium regulation of NifA activity. Western analysis demonstrated that both constitutively expressed wild-type and ammonium-tolerant NifA1 proteins exhibited high stability and accumulated to comparable levels in cells grown in the presence of ammonium excluding the possibility that proteolytic degradation was responsible for ammonium-dependent inactivation of NifA.

Human dendritic cells infected by Listeria monocytogenes: induction of maturation, requirements for phagolysosomal escape and antigen presentation capacity

An important feature of microbial infections is the ability of the microorganisms to interfere with and modulate the induction of host immune reactions. However, little is known about the effects of broad host range pathogens such as Listeria monocytogenes on similar cell types in different hosts. Here we examine the effects of the human and animal pathogen L. monocytogenes on human dendritic cells (DC) since this type of cells is essential for the initiation of immune responses. Listeria are phagocytosed efficiently by immature human DC and the bacteria escape from the phagolysosome quickly. Lack of the pore-forming activity of listeriolysin, which was found to be essential for the vacuolar escape of this bacterium in other cell types, retarded but did not prevent egress from the vacuole. Treatment of cultures of immature DC with L. monocytogenes resulted in rapid changes in morphology and cellular constitution followed by maturation of the DC. This could be judged by the appearance of maturation-specific cell surface markers. Antigen presentation to CD4 T cells was apparently not impaired by the infection. These results are in clear contrast to results obtained previously in the mouse system (Guzman et al., Mol. Microbiol. 1996. 20: 119 - 126; Darji et al., Eur. J. Immunol. 1997. 27: 1696 - 1703.).

Autologous, allogeneic tumor cells or genetically engineered cells as cancer vaccine against melanoma

Melanoma is a prototype of immunogenic tumor to which various types of immunotherapy have been applied extensively over the past decades. Melanoma vaccines are designed for the purpose of immune modulation and subsequent anti-tumor effects in the process of an active specific immunotherapy. Previous attempts of these vaccines include immunization with whole tumor cells/cell lysates admixed with nonspecific adjuvants. While these vaccines generated enhanced anti-tumor immunity in a subset of patients, some of which showing prolonged survival compared to historical controls, no clinical benefit has so far been demonstrated in a properly controlled phase III study. New-generation melanoma vaccines, which are based on genetic modifications of tumor cells to express cytokines, generated long-lasting systemic anti-tumor immunity in animal models. Translation of these preclinical results primarily into melanoma patients with advanced diseases, shows the potential of these vaccines to induce systemic anti-tumor immune responses and in some instances tumor regression with acceptably low toxicity. Higher efficacy of this novel vaccine approach would be expected when used in a postsurgical adjuvant setting when the tumor load is small. Also other novel vaccine approaches such as dendritic cell-based therapy hold promise for the treatment of melanoma. But the clinical value of all these new approaches has to be analysed in prospectively randomized clinical studies.

Identification of a new HLA-A(*)0201-restricted T-cell epitope from the tyrosinase-related protein 2 (TRP2) melanoma antigen

For the development of peptide-based immunotherapies, the identification of additional tumor antigens and T-cell epitopes is required. Because HLA-A(*)0201 is the most common allele in Caucasians, who represent the majority of patients with melanomas, 6 peptides carrying an HLA-A(*)0201 motif were synthesized from tyrosinase-related protein-2 (TRP2) melanoma antigen and tested for binding affinity to the HLA allele using processing-defective T2 cells. These peptides were then pulsed onto autologous dendritic cells and used to stimulate in vitro CD8(+)-enriched T cells isolated from peripheral blood of HLA-A(*)02(+) healthy donors or melanoma patients for the induction of specific cytotoxic T lymphocytes (CTLs). One peptide, TRP2(288-296) (SLDDYNHLV), the best HLA-A(*)0201 binder, elicited specific CTLs from 1 of 4 patients and 3 of 4 healthy donors. The induced CTLs from the patient and from 1 donor efficiently recognized HLA-A(*)02(+) TRP2(+) melanomas as well as COS-7 cells expressing HLA-A(*)0201 and TRP2 in an HLA class I-restricted manner, as assessed by cytokine production and direct cytolysis. The remaining 2 CTL lines derived from 2 donors displayed low T-cell receptor avidity, which could lyse melanoma cells in the presence of exogenous peptide. Since TRP2 is an antigen expressed in most melanomas, identification of the TRP2/HLA-A(*)0201 peptide SLDDYNHLV may facilitate the design of present peptide-based immunotherapies for the treatment of a large fraction of melanoma patients.

Cell-based vaccination against melanoma--background, preliminary results, and perspective

Melanoma is the prototype of a tumor to which many forms of immunotherapy have been applied extensively over the past two decades. Melanoma vaccines (active specific immunotherapy) are designed to modulate the immune system and have subsequent anti-tumor effects with minimal toxicity. Previous attempts to produce melanoma vaccines include immunization with whole tumor cells/cell lysates admixed with nonspecific adjuvants. While these vaccines generate enhanced anti-tumor immunity in a subset of patients, some of whom survive for longer than historical controls, no clinical benefit has so far been demonstrated in a properly controlled phase III study. Genetic modifications of tumor cells to make them express cytokines afford new-generation melanoma vaccines, and generate long-lasting systemic antitumor immunity in animal models. Translation of these preclinical results primarily into melanoma patients with advanced diseases shows the potential to induce systemic antitumor immune responses and in some instances tumor regression with acceptably low toxicity. The efficacy of this novel vaccine approach would be expected to be higher when used in a postsurgical adjuvant setting when the tumor load is small. Other novel vaccine approaches such as dendritic cell-based therapy also hold promise for the treatment of melanoma. The clinical value of all these new approaches will eventually have to be established in prospectively randomized clinical studies.

Evidence for a regulatory link of nitrogen fixation and photosynthesis in Rhodobacter capsulatus via HvrA

A Rhodobacter capsulatus reporter strain, carrying a constitutively expressed nifA gene and a nifH-lacZ gene fusion, was used for random transposon Tn5 mutagenesis to search for genes required for the NtrC-independent ammonium repression of NifA activity. A mutation in hvrA, which is known to be involved in low-light activation of the photosynthetic apparatus, released both ammonium and oxygen control of nifH expression in this reporter strain, demonstrating a regulatory link of nitrogen fixation and photosynthesis via HvrA. In addition, a significant increase in bacteriochlorophyll alpha (BChl alpha) content was found in cells under nitrogen-fixing conditions. HvrA was not involved in this up-regulation of BChl alpha. Instead, the presence of active nitrogenase seemed to be sufficient for this process, since no increase in BChl alpha content was observed in different nif mutants.