Immunotherapy Resistance by Inflammation-Induced Dedifferentiation

A promising arsenal of targeted and immunotherapy treatments for metastatic melanoma has emerged over the last decade. With these therapies, we now face new mechanisms of tumor-acquired resistance. We report here a patient whose metastatic melanoma underwent dedifferentiation as a resistance mechanism to adoptive T-cell transfer therapy (ACT) to the MART1 antigen, a phenomenon that had been observed only in mouse studies to date. After an initial period of tumor regression, the patient presented in relapse with tumors lacking melanocytic antigens (MART1, gp100) and expressing an inflammation-induced neural crest marker (NGFR). We demonstrate using human melanoma cell lines that this resistance phenotype can be induced in vitro by treatment with MART1 T cell receptor-expressing T cells or with TNFα, and that the phenotype is reversible with withdrawal of inflammatory stimuli. This supports the hypothesis that acquired resistance to cancer immunotherapy can be mediated by inflammation-induced cancer dedifferentiation.Significance: We report a patient whose metastatic melanoma underwent inflammation-induced dedifferentiation as a resistance mechanism to ACT to the MART1 antigen. Our results suggest that future melanoma ACT protocols may benefit from the simultaneous targeting of multiple tumor antigens, modulating the inflammatory response, and inhibition of inflammatory dedifferentiation-inducing signals. Cancer Discov; 8(8); 935-43. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 899.

Abstract NG04: Mechanisms of resistance to anti-PD-1 immunotherapy through interferon pathway mutations

Checkpoint blockade immunotherapy can produce dramatic, durable tumor regression, is now being deployed or tested in a growing list of cancer types, and has received FDA approval for the treatment of metastatic melanoma, Hodgkin’s lymphoma, and lung, renal, and head and neck carcinomas. Depending on cancer type, higher CD8 infiltration, PD-L1 expression, and mutational load have all been reported as positive prognostic factors for response. We studied response to antiprogrammed cell death 1 (PD-1) or PD-1 ligand (PD-L1) therapy in a cohort of 55 patients from centers in the US and Australia with advanced desmoplastic melanoma (a rare subtype, less than 4% of patients). Our analyses further highlight the relationship between clinical benefit from immune checkpoint blockade therapy and higher mutational load and PD-L1 expression. Objective tumor responses were noted in 39 patients (71%), with most being long lasting. Our analyses reveal that baseline tumor biopsies have significantly higher tumor parenchymal PD-L1 expression than nondesmoplastic skin melanomas that is highly correlated with CD8+ T-cell infiltration in the invasive margins, reflective of adaptive immune resistance as a result of active antitumor immune process. Desmoplastic melanoma has a known relationship to ultraviolet light radiation damage, resulting in one of the highest mutational burdens among all cancer types. Whole-exome sequencing in this cohort confirms this finding, with a median of 1315 somatic nonsynonymous mutations per tumor, as compared with a median of 485 mutations per tumor in nondesmoplastic melanomas (P = 0.01).

However, accumulating data from cutaneous melanoma suggest that primary and secondary resistance to therapy remains a major challenge. Recent pooled data from 655 patients on a clinical trial of the antiprogrammed death 1 (PD-1) therapy antibody pembrolizumab reported that ~60% of patients with metastatic melanoma had no response to therapy (primary resistance), while ~25% of those with initial objective tumor regression had progressed as much as two years later despite continuous therapy (secondary or acquired resistance). Potential mechanisms of resistance conceptually stratify into either T-cell dysfunction (lack of recognition, trafficking, intrinsic exhaustion, or extrinsic suppression) or tumor-based escape (loss of antigen presentation, resistance to killing, or upregulation of suppressive factors).

We have recently reported two genetic mechanisms of acquired resistance to anti-PD-1 therapy (1). In this study, we analyzed melanoma cases with late acquired resistance after strong initial response to anti-PD1 therapy, with the hypothesis that changes from baseline would be mechanistically meaningful in this setting, particularly with respect to immune function or mutations acquired by surviving clones. To investigate this, we performed whole exome sequencing and immunohistochemistry on four cases with paired pre/postrelapse tumor samples, followed by in vitro modeling with primary tumor cell lines.

First, we studied the local immune environment at relapse to rule out a lack of tumor-specific T-cell effectors. Immunohistochemistry revealed that CD8 T cells were present in baseline tumors, and remained present at relapse in large numbers around the tumor margins. This is a pattern that our lab and others have shown would otherwise be predictive of response to PD1 therapy. Futher studies using targeted sequencing of the T-cell receptor population in biopsies from the four reported cases showed that the top T-cell clones at baseline or during active response were detected at similar frequencies in the relapsing tumors, indicating that the local T-cell repertoire had not changed. Additionally, clones that significantly increased in frequency in the peripheral blood during active response were highly enriched among the top clones in the relapsing tumor. Together, these data indicate the T cells present at relapse are likely the same tumor-specific clones that mediated the original response. Multiplexed immunofluorescence showed that stromal cells in the tumor microenvironment at progression were strongly positive for PD-L1 expression in areas of high T-cell density. PD-L1 is often upregulated in response to the interferon gamma produced by activated T cells, raising the possibility that these T cells were currently or had recently been active.

With evidence that T cells were still present and possibly active in the resistant lesions, we investigated relapse-specific changes within the tumors themselves by whole exome sequencing. We identified new homozygous loss-of-function mutations in the interferon receptor pathway-associated kinases in the relapse biopsies of two separate cases (JAK1 Q503* and JAK2 F547_splice-site). In addition to the clinical radiographic evidence of relapse in situ, we found strong genetic evidence that the progressing lesions were directly derived from the baseline lesions by clonal selection and outgrowth. Despite up to two years between biopsies, the resistant tumor shared >92% of nonsynonymous mutations originally identified at baseline. The relapsing tumors also contained the same initial chromosomal loss-of-heterozygosity (LOH) pattern as baseline, and the JAK mutations become homozygous as part of additional LOH events. Neither JAK mutation was detected pretherapy, either in the exome sequencing reads or by targeted amplicon resequencing, suggesting these represent a de novo mutation or extremely rare preexisting clone.

While the JAK kinases are known to associate with growth factor, cytokine, and interferon receptors, in the context of immune resistance we focused on their role in interferon sensitivity. Interferons cause phosphorylation of the STAT transcription factors, and upregulate expression of chemokines, antigen presentation machinery, and PD-L1. In vitro western blot, RNA (Nanostring), and flow cytometry studies using primary cell lines derived from pre- and postprogression biopsies from the JAK2 mutated case showed that the JAK2 mutated cells were entirely insensitive to interferon gamma. Other melanoma cell lines with JAK1 or JAK2 deleted by CRISPR-Cas9 approach produced similar results. We also found the JAK mutant cell lines to be resistant to interferon-gamma induced growth inhibition, while the baseline and JAK wild-type cell lines remained sensitive. Notably, the JAK2 mutant cell lines were still sensitive to growth inhibition by interferon-alpha/beta or a STING agonist (all of which are JAK2-independent), showing the lack of growth arrest was specific to interferon gamma resistance and not a generalized phenomenon.

In a third case, we also identified a new truncating mutation in the antigen presentation gene beta-2 microglobulin (B2M), which led to loss of surface expression of major histocompatibility complex (MHC) class I. This mechanism has been previously implicated in immune escape. Since the publication of this work we have gathered seven additional biopsies of late secondary progression from patients with advanced melanoma (four of them with a paired baseline) in order to assess the frequency of acquired genetic mutations in the interferon gamma and antigen presentation pathways, as well as define other potential mechanisms.

Our studies of primary resistance to anti-PD-1 therapy provide further support that loss of function mutations in JAK1 or JAK2 are of high relevance for resistance to antiprogrammed death protein 1 (PD-1) therapy. Immune selection may lead to similar mutations in previously untreated patients, which would result in lack of adaptive PD-L1 response by cancer cells to a T-cell infiltrate, and result in primary resistance to anti-PD-1 therapy. Whole-exome sequencing of metastatic melanoma biopsies from 23 patients treated with the anti-PD1 revealed a JAK1 missense mutation with chromosomal amplification in the tumor from a nonresponding patient who otherwise had the highest mutational load in the cohort. Similarly, among 16 patients with mismatch repair deficient colon cancer treated with PD-1 blockade, we again found a homozygous JAK1 loss-of-function mutation in the tumor of a nonresponding patient. Analysis of genomic and proteomic data from the TCGA suggests that JAK1/2 loss-of-function alterations confer adverse outcomes in patients, which may result from an immune-editing process. Therefore, we propose that JAK1/2 loss-of-function mutations are positively selected for by immune-editing processes, leading to primary as well as secondary resistance to PD-1 blockade therapy.

The relevance of genetic alterations in the interferon gamma receptor pathway is highlighted by the results published by another group (2). In their study, knockdown of the interferon gamma receptor in a mouse model of melanoma showed impaired tumor rejection in response to anti-CTLA4 therapy, and they identified increased frequency of mutations in interferon-related genes in patients who failed to respond to the anti-CTLA-4 antibody ipilimumab. While the final frequency of interferon signaling or B2M defects and their contribution to primary versus secondary resistance remains to be seen, cataloguing these and other mechanisms will be important for determining who will benefit from immunotherapy and designing rational next-generation drug combinations to improve outcomes with these therapies.

References

1. Zaretsky JM, Garcia-Diaz A, Shin DS et al. Mutations associated with acquired resistance to PD-1 blockade in melanoma. N Engl J Med 2016;375(9):819-29. PMID: 27433842.

2. Gao J, Shi LZ, Zhao et al. Loss of IFN-pathway genes in tumor cells as a mechanism of resistance to anti-CTLA4 therapy. Cell 2016;167(2):397-404. PMID: 27667683.

Citation Format: Jesse Zaretsky, Angel Garcia-Diaz, Daniel S. Shin, Helena Escuin-Ordinas, Willy Hugo, Siwen Hu-Lieskovan, Zeynep Eroglu, Davis Y. Torrejon, Paul C. Tumeh, Roger S. Lo, Antoni Ribas. Mechanisms of resistance to anti-PD-1 immunotherapy through interferon pathway mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr NG04. doi:10.1158/1538-7445.AM2017-NG04

MAPK Signaling and Inflammation Link Melanoma Phenotype Switching to Induction of CD73 during Immunotherapy

Evolution of tumor cell phenotypes promotes heterogeneity and therapy resistance. Here we found that induction of CD73, the enzyme that generates immunosuppressive adenosine, is linked to melanoma phenotype switching. Activating MAPK mutations and growth factors drove CD73 expression, which marked both nascent and full activation of a mesenchymal-like melanoma cell state program. Proinflammatory cytokines like TNFα cooperated with MAPK signaling through the c-Jun/AP-1 transcription factor complex to activate CD73 transcription by binding to an intronic enhancer. In a mouse model of T-cell immunotherapy, CD73 was induced in relapse melanomas, which acquired a mesenchymal-like phenotype. We also detected CD73 upregulation in melanoma patients progressing under adoptive T-cell transfer or immune checkpoint blockade, arguing for an adaptive resistance mechanism. Our work substantiates CD73 as a target to combine with current immunotherapies, but its dynamic regulation suggests limited value of CD73 pretreatment expression as a biomarker to stratify melanoma patients. Cancer Res; 77(17); 4697-709. ©2017 AACR.

Phase I Trial of Intratumoral Injection of CCL21 Gene-Modified Dendritic Cells in Lung Cancer Elicits Tumor-Specific Immune Responses and CD8+ T-cell Infiltration

Purpose: A phase I study was conducted to determine safety, clinical efficacy, and antitumor immune responses in patients with advanced non-small cell lung carcinoma (NSCLC) following intratumoral administration of autologous dendritic cells (DC) transduced with an adenoviral (Ad) vector expressing the CCL21 gene (Ad-CCL21-DC). We evaluated safety and tumor antigen-specific immune responses following in situ vaccination (ClinicalTrials.gov: NCT01574222).Experimental Design: Sixteen stage IIIB/IV NSCLC subjects received two vaccinations (1 × 10⁶, 5 × 10⁶, 1 × 10⁷, or 3 × 10⁷ DCs/injection) by CT- or bronchoscopic-guided intratumoral injections (days 0 and 7). Immune responses were assessed by tumor antigen-specific peripheral blood lymphocyte induction of IFNγ in ELISPOT assays. Tumor biopsies were evaluated for CD8⁺ T cells by IHC and for PD-L1 expression by IHC and real-time PCR (RT-PCR).Results: Twenty-five percent (4/16) of patients had stable disease at day 56. Median survival was 3.9 months. ELISPOT assays revealed 6 of 16 patients had systemic responses against tumor-associated antigens (TAA). Tumor CD8⁺ T-cell infiltration was induced in 54% of subjects (7/13; 3.4-fold average increase in the number of CD8⁺ T cells per mm²). Patients with increased CD8⁺ T cells following vaccination showed significantly increased PD-L1 mRNA expression.Conclusions: Intratumoral vaccination with Ad-CCL21-DC resulted in (i) induction of systemic tumor antigen-specific immune responses; (ii) enhanced tumor CD8⁺ T-cell infiltration; and (iii) increased tumor PD-L1 expression. Future studies will evaluate the role of combination therapies with PD-1/PD-L1 checkpoint inhibition combined with DC-CCL21 in situ vaccination. Clin Cancer Res; 23(16); 4556-68. ©2017 AACR.

Liver Metastasis and Treatment Outcome with Anti-PD-1 Monoclonal Antibody in Patients with Melanoma and NSCLC

We explored the association between liver metastases, tumor CD8⁺ T-cell count, and response in patients with melanoma or lung cancer treated with the anti-PD-1 antibody, pembrolizumab. The melanoma discovery cohort was drawn from the phase I Keynote 001 trial, whereas the melanoma validation cohort was drawn from Keynote 002, 006, and EAP trials and the non-small cell lung cancer (NSCLC) cohort from Keynote 001. Liver metastasis was associated with reduced response and shortened progression-free survival [PFS; objective response rate (ORR), 30.6%; median PFS, 5.1 months] compared with patients without liver metastasis (ORR, 56.3%; median PFS, 20.1 months) P ≤ 0.0001, and confirmed in the validation cohort (P = 0.0006). The presence of liver metastasis significantly increased the likelihood of progression (OR, 1.852; P < 0.0001). In a subset of biopsied patients (n = 62), liver metastasis was associated with reduced CD8⁺ T-cell density at the invasive tumor margin (liver metastasis⁺ group, n = 547 ± 164.8; liver metastasis^- group, n = 1,441 ± 250.7; P < 0.016). A reduced response rate and shortened PFS was also observed in NSCLC patients with liver metastasis [median PFS, 1.8 months; 95% confidence interval (CI), 1.4-2.0], compared with those without liver metastasis (n = 119, median PFS, 4.0 months; 95% CI, 2.1-5.1), P = 0.0094. Thus, liver metastatic patients with melanoma or NSCLC that had been treated with pembrolizumab were associated with reduced responses and PFS, and liver metastases were associated with reduced marginal CD8⁺ T-cell infiltration, providing a potential mechanism for this outcome. Cancer Immunol Res; 5(5); 417-24. ©2017 AACR.

Primary Resistance to PD-1 Blockade Mediated by JAK1/2 Mutations

Loss-of-function mutations in JAK1/2 can lead to acquired resistance to anti-programmed death protein 1 (PD-1) therapy. We reasoned that they may also be involved in primary resistance to anti-PD-1 therapy. JAK1/2-inactivating mutations were noted in tumor biopsies of 1 of 23 patients with melanoma and in 1 of 16 patients with mismatch repair-deficient colon cancer treated with PD-1 blockade. Both cases had a high mutational load but did not respond to anti-PD-1 therapy. Two out of 48 human melanoma cell lines had JAK1/2 mutations, which led to a lack of PD-L1 expression upon interferon gamma exposure mediated by an inability to signal through the interferon gamma receptor pathway. JAK1/2 loss-of-function alterations in The Cancer Genome Atlas confer adverse outcomes in patients. We propose that JAK1/2 loss-of-function mutations are a genetic mechanism of lack of reactive PD-L1 expression and response to interferon gamma, leading to primary resistance to PD-1 blockade therapy.

SIGNIFICANCE

A key functional result from somatic JAK1/2 mutations in a cancer cell is the inability to respond to interferon gamma by expressing PD-L1 and many other interferon-stimulated genes. These mutations result in a genetic mechanism for the absence of reactive PD-L1 expression, and patients harboring such tumors would be unlikely to respond to PD-1 blockade therapy. Cancer Discov; 7(2); 188-201. ©2016 AACR.See related commentary by Marabelle et al., p. 128This article is highlighted in the In This Issue feature, p. 115.

Infiltration of CD8 T Cells and Expression of PD-1 and PD-L1 in Synovial Sarcoma

Tumors expressing programmed death ligand 1 (PD-L1) interact with the corresponding negative-signal generating immune receptor on the surface of CD8 T cells, PD-1, thereby suppressing antitumor activity. Therapeutics blocking this interaction have shown promise in various cancers by restoring functional antitumor T-cell activity. We explored the degree of PD-L1, PD-1, and CD8 expression in a retrospective analysis of 29 clinical synovial sarcoma samples. Quantitative immunohistochemistry and multiplex immunofluorescence were used to determine relative quantification of CD8⁺ and PD-1⁺ T cells and PD-L1 expression within the intratumor area and the interface between the tumor and the surrounding nontumor tissue (i.e., invasive margin), and colocalization of these factors, respectively. PD-L1, PD-1, and CD8 cell densities in the tumor-invasive margins were significantly higher in the metastatic tumors than the primary tumors (P < 0.01), and PD-L1, PD-1, and CD8 cell densities were all significantly positively correlated with one other (P < 0.0001). PD-1 cell density in the tumor-invasive margin was significantly associated with worse progression-free survival. Multiplex immunofluorescence demonstrated coexpression of PD-1 and CD8 on lymphocytes within the invasive margin, as well as relative proximity between PD-1⁺ CD8 cells and PD-L1⁺ tumor cells. Our results provide a preclinical rationale for screening of patients with synovial sarcoma for the colocalization of CD8, PD-1, and PD-L1, which may be a marker for response to PD-1 blockade therapy. Cancer Immunol Res; 5(2); 118-26. ©2016 AACR.

Mutations Associated with Acquired Resistance to PD-1 Blockade in Melanoma

BACKGROUND

Approximately 75% of objective responses to anti-programmed death 1 (PD-1) therapy in patients with melanoma are durable, lasting for years, but delayed relapses have been noted long after initial objective tumor regression despite continuous therapy. Mechanisms of immune escape in this context are unknown.

METHODS

We analyzed biopsy samples from paired baseline and relapsing lesions in four patients with metastatic melanoma who had had an initial objective tumor regression in response to anti-PD-1 therapy (pembrolizumab) followed by disease progression months to years later.

RESULTS

Whole-exome sequencing detected clonal selection and outgrowth of the acquired resistant tumors and, in two of the four patients, revealed resistance-associated loss-of-function mutations in the genes encoding interferon-receptor-associated Janus kinase 1 (JAK1) or Janus kinase 2 (JAK2), concurrent with deletion of the wild-type allele. A truncating mutation in the gene encoding the antigen-presenting protein beta-2-microglobulin (B2M) was identified in a third patient. JAK1 and JAK2 truncating mutations resulted in a lack of response to interferon gamma, including insensitivity to its antiproliferative effects on cancer cells. The B2M truncating mutation led to loss of surface expression of major histocompatibility complex class I.

CONCLUSIONS

In this study, acquired resistance to PD-1 blockade immunotherapy in patients with melanoma was associated with defects in the pathways involved in interferon-receptor signaling and in antigen presentation. (Funded by the National Institutes of Health and others.).

Enhanced skin toxicity with concurrent ipilimumab and radiation in vaginal/vulvar melanoma: a case report and literature review

Ipilimumab is a monoclonal cytotoxic T-lymphocyte-associated protein 4 antibody that has demonstrated improved survival in cutaneous melanoma. Little is known about the clinical impact of combining anti-cytotoxic T-lymphocyteassociated protein 4 therapy with radiation. Here we report a case of severe cutaneous desquamation in a 70-year-old female with vaginal/vulvar melanoma receiving concurrent ipilimumab and radiation therapy. The toxicity was successfully treated with oral/topical steroids and a break from treatment. This case underscores the importance of future research on optimal strategies for combining radiation with novel anti-tumour agents.

Immunodynamics: a cancer immunotherapy trials network review of immune monitoring in immuno-oncology clinical trials

The efficacy of PD-1/PD-L1 targeted therapies in addition to anti-CTLA-4 solidifies immunotherapy as a modality to add to the anticancer arsenal. Despite raising the bar of clinical efficacy, immunologically targeted agents raise new challenges to conventional drug development paradigms by highlighting the limited relevance of assessing standard pharmacokinetics (PK) and pharmacodynamics (PD). Specifically, systemic and intratumoral immune effects have not consistently correlated with standard relationships between systemic dose, toxicity, and efficacy for cytotoxic therapies. Hence, PK and PD paradigms remain inadequate to guide the selection of doses and schedules, both starting and recommended Phase 2 for immunotherapies. The promise of harnessing the immune response against cancer must also be considered in light of unique and potentially serious toxicities. Refining immune endpoints to better inform clinical trial design represents a high priority challenge. The Cancer Immunotherapy Trials Network investigators review the immunodynamic effects of specific classes of immunotherapeutic agents to focus immune assessment modalities and sites, both systemic and importantly intratumoral, which are critical to the success of the rapidly growing field of immuno-oncology.

PD-1 Blockade Expands Intratumoral Memory T Cells

Tumor responses to programmed cell death protein 1 (PD-1) blockade therapy are mediated by T cells, which we characterized in 102 tumor biopsies obtained from 53 patients treated with pembrolizumab, an antibody to PD-1. Biopsies were dissociated, and single-cell infiltrates were analyzed by multicolor flow cytometry using two computational approaches to resolve the leukocyte phenotypes at the single-cell level. There was a statistically significant increase in the frequency of T cells in patients who responded to therapy. The frequency of intratumoral B cells and monocytic myeloid-derived suppressor cells significantly increased in patients' biopsies taken on treatment. The percentage of cells with a regulatory T-cell phenotype, monocytes, and natural killer cells did not change while on PD-1 blockade therapy. CD8(+) memory T cells were the most prominent phenotype that expanded intratumorally on therapy. However, the frequency of CD4(+) effector memory T cells significantly decreased on treatment, whereas CD4(+) effector T cells significantly increased in nonresponding tumors on therapy. In peripheral blood, an unusual population of blood cells expressing CD56 was detected in two patients with regressing melanoma. In conclusion, PD-1 blockade increases the frequency of T cells, B cells, and myeloid-derived suppressor cells in tumors, with the CD8(+) effector memory T-cell subset being the major T-cell phenotype expanded in patients with a response to therapy.

PD-1 Blockade Expands Intratumoral Memory T Cells

Tumor responses to programmed cell death protein 1 (PD-1) blockade therapy are mediated by T cells, which we characterized in 102 tumor biopsies obtained from 53 patients treated with pembrolizumab, an antibody to PD-1. Biopsies were dissociated, and single-cell infiltrates were analyzed by multicolor flow cytometry using two computational approaches to resolve the leukocyte phenotypes at the single-cell level. There was a statistically significant increase in the frequency of T cells in patients who responded to therapy. The frequency of intratumoral B cells and monocytic myeloid-derived suppressor cells significantly increased in patients' biopsies taken on treatment. The percentage of cells with a regulatory T-cell phenotype, monocytes, and natural killer cells did not change while on PD-1 blockade therapy. CD8(+) memory T cells were the most prominent phenotype that expanded intratumorally on therapy. However, the frequency of CD4(+) effector memory T cells significantly decreased on treatment, whereas CD4(+) effector T cells significantly increased in nonresponding tumors on therapy. In peripheral blood, an unusual population of blood cells expressing CD56 was detected in two patients with regressing melanoma. In conclusion, PD-1 blockade increases the frequency of T cells, B cells, and myeloid-derived suppressor cells in tumors, with the CD8(+) effector memory T-cell subset being the major T-cell phenotype expanded in patients with a response to therapy.

PD-1 blockade induces responses by inhibiting adaptive immune resistance

Therapies that target the programmed death-1 (PD-1) receptor have shown unprecedented rates of durable clinical responses in patients with various cancer types. One mechanism by which cancer tissues limit the host immune response is via upregulation of PD-1 ligand (PD-L1) and its ligation to PD-1 on antigen-specific CD8(+) T cells (termed adaptive immune resistance). Here we show that pre-existing CD8(+) T cells distinctly located at the invasive tumour margin are associated with expression of the PD-1/PD-L1 immune inhibitory axis and may predict response to therapy. We analysed samples from 46 patients with metastatic melanoma obtained before and during anti-PD-1 therapy (pembrolizumab) using quantitative immunohistochemistry, quantitative multiplex immunofluorescence, and next-generation sequencing for T-cell antigen receptors (TCRs). In serially sampled tumours, patients responding to treatment showed proliferation of intratumoral CD8(+) T cells that directly correlated with radiographic reduction in tumour size. Pre-treatment samples obtained from responding patients showed higher numbers of CD8-, PD-1- and PD-L1-expressing cells at the invasive tumour margin and inside tumours, with close proximity between PD-1 and PD-L1, and a more clonal TCR repertoire. Using multivariate analysis, we established a predictive model based on CD8 expression at the invasive margin and validated the model in an independent cohort of 15 patients. Our findings indicate that tumour regression after therapeutic PD-1 blockade requires pre-existing CD8(+) T cells that are negatively regulated by PD-1/PD-L1-mediated adaptive immune resistance.

Abstract 5015: TCR usage analysis in blood reveals different mechanisms of action of CTLA-4 and PD-1 blockade in patients

Immune-checkpoint blockade therapies are providing long-lasting responses in a subset of patients with malignant metastatic melanoma. In an effort to better understand the underlying mechanism, the T-cell population in peripheral blood mononuclear cells (PBMCs) was characterized. The complementarity determining region 3 (CDR3) of the rearranged T cell receptor variable ß chain genes (TCR Vß) was sequenced. This was performed using gDNA extracted from the PBMCs of twenty-one patients that were treated with antibody to Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) (tremelimumab) and seven patients that were treated with antibody to the Programmed Death-1 (PD-1) blockade (MK-3475) at baseline and at day 30-60 post first treatment. Four healthy donors were also sequenced as controls. Control PBMCs displayed random distribution with three patients showing a decrease and one showing an increase in the number of unique productive sequences (UPS) from baseline to the time after first cycle. In PBMCs from patients receiving the CTLA-4 antibody, two out of 21 samples showed a decrease in total number of UPS, while 19 out of 21samples experienced an increase. In PBMCs from patients receiving PD-1 antibody, the reponse was more similar to healthy donors as 5 out of 7 (71%) displayed a decrease and 2 out 7 (29%) an increase in total UPS from the pre to post timepoint. There was an increase in the absolute lymphocyte count (ALC) after CTLA-4 blockade therapy (p=0.03), but not in the samples from patients treated with PD-1 antibody (p=0.53). A direct correlation between ALC increase and increase in UPS for CTLA-4 blockade was ruled out (p=0.1 Spearman Correlation). When analyzing according to clinical response status, all responders to CTLA-4 blockade (4 out of 19) experienced an increase in the number of circulating clones. However, samples from clinical responders to PD-1 blockade showed an increase (2 out of 5) or decrease (1 out of 2) in the circulating pool. Considering the concerning toxicity profile for CTLA-4-blockade versus the mild toxicity for PD-1 antibodies, this data supports a model where CTLA-4 blockade induces a non-specific systemic expansion of T cells, while PD-1 blockade may have more specific effects directly in the tumor.

Citation Format: Lidia Robert, Christina L. Harview, Ryan Emerson, Stephen Mok, Blanca Homet, Begonya Comin-Anduix, Richard C. Koya, Harlan Robins, Paul C. Tumeh, Antoni Ribas. TCR usage analysis in blood reveals different mechanisms of action of CTLA-4 and PD-1 blockade in patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5015. doi:10.1158/1538-7445.AM2014-5015

The future of cancer therapy: selecting patients likely to respond to PD1/L1 blockade

It is conceivable that, in the near future, an assay that defines the likelihood of a patient with advanced cancer to respond to immunotherapy based on PD1/L1 blockade will be the initial decision point to select the treatment of patients with any cancer type.

Distinct immunological mechanisms of CTLA-4 and PD-1 blockade revealed by analyzing TCR usage in blood lymphocytes

Targeting immune inhibitory receptors has brought excitement, innovation and hope to cancer patients. Our recent work revealed the immunological effects of blocking the CTLA4 and PD-1 immune checkpoints on T cell receptor usage among peripheral blood cells, and further uncovers how the expansion of the T cell repertoire matches the immunotoxicity profile of the therapy.

Safety and tumor responses with lambrolizumab (anti-PD-1) in melanoma

BACKGROUND

The programmed death 1 (PD-1) receptor is a negative regulator of T-cell effector mechanisms that limits immune responses against cancer. We tested the anti-PD-1 antibody lambrolizumab (previously known as MK-3475) in patients with advanced melanoma.

METHODS

We administered lambrolizumab intravenously at a dose of 10 mg per kilogram of body weight every 2 or 3 weeks or 2 mg per kilogram every 3 weeks in patients with advanced melanoma, both those who had received prior treatment with the immune checkpoint inhibitor ipilimumab and those who had not. Tumor responses were assessed every 12 weeks.

RESULTS

A total of 135 patients with advanced melanoma were treated. Common adverse events attributed to treatment were fatigue, rash, pruritus, and diarrhea; most of the adverse events were low grade. The confirmed response rate across all dose cohorts, evaluated by central radiologic review according to the Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1, was 38% (95% confidence interval [CI], 25 to 44), with the highest confirmed response rate observed in the cohort that received 10 mg per kilogram every 2 weeks (52%; 95% CI, 38 to 66). The response rate did not differ significantly between patients who had received prior ipilimumab treatment and those who had not (confirmed response rate, 38% [95% CI, 23 to 55] and 37% [95% CI, 26 to 49], respectively). Responses were durable in the majority of patients (median follow-up, 11 months among patients who had a response); 81% of the patients who had a response (42 of 52) were still receiving treatment at the time of analysis in March 2013. The overall median progression-free survival among the 135 patients was longer than 7 months.

CONCLUSIONS

In patients with advanced melanoma, including those who had had disease progression while they had been receiving ipilimumab, treatment with lambrolizumab resulted in a high rate of sustained tumor regression, with mainly grade 1 or 2 toxic effects. (Funded by Merck Sharp and Dohme; ClinicalTrials.gov number, NCT01295827.).

BRAF inhibitor vemurafenib improves the antitumor activity of adoptive cell immunotherapy

Combining immunotherapy with targeted therapy blocking oncogenic BRAFV600 may result in improved treatments for advanced melanoma. In this study, we developed a BRAFV600E-driven murine model of melanoma, SM1, which is syngeneic to fully immunocompetent mice. SM1 cells exposed to the BRAF inhibitor vemurafenib (PLX4032) showed partial in vitro and in vivo sensitivity resulting from the inhibition of MAPK pathway signaling. Combined treatment of vemurafenib plus adoptive cell transfer therapy with lymphocytes genetically modified with a T-cell receptor (TCR) recognizing chicken ovalbumin (OVA) expressed by SM1-OVA tumors or pmel-1 TCR transgenic lymphocytes recognizing gp100 endogenously expressed by SM1 resulted in superior antitumor responses compared with either therapy alone. T-cell analysis showed that vemurafenib did not significantly alter the expansion, distribution, or tumor accumulation of the adoptively transferred cells. However, vemurafenib paradoxically increased mitogen-activated protein kinase (MAPK) signaling, in vivo cytotoxic activity, and intratumoral cytokine secretion by adoptively transferred cells. Taken together, our findings, derived from 2 independent models combining BRAF-targeted therapy with immunotherapy, support the testing of this therapeutic combination in patients with BRAFV600 mutant metastatic melanoma.

Abstract 3510: Paradoxical MAPK activation and beneficial effects of vemurafenib on T-cell phenotype resulting in improved functionality in vivo

Adoptive T cell transfer (ACT) based immunotherapy for melanoma can induce remarkable and highly durable tumor responses, which may last many years. Vemurafenib (Vmf) is a potent inhibitor of BRAF mutated at V600E with response rates of up to 80% in patients with metastatic melanoma. However, drug resistance develops in most of patients leading to response durations of only several months. We previously showed that the combined approach of BRAF inhibition with adoptive cell immunotherapy leads to an improved outcome in vivo. Here we show that Vmf also directly and independently affects T lymphocytes, resulting in favorable anti-tumoral phenotypic changes. We had created a transplantable murine melanoma cell-line driven by V600E BRAF oncogene (SM1) derived from a spontaneously arising melanoma in transgenic mice harboring the V600E BRAF mutation under the control of tyrosinase promoter. SM1 cells stably expressing the ovalbumin (OVA) model antigen were implanted in C57BL6 mice. Daily i.p. Vmf combined with ACT of OVA-specific TCR transgenic cells generated by retroviral transduction demonstrated superior tumor control of the combined treatment in comparison to each treatment alone. We also confirmed better outcomes with this combination in the pmel-1 model, which is based on the ACT of TCR transgenic cells against the endogenously expressed and relevant melanoma antigen, gp100. We then cultured primary T cells in the presence of Vmf with a broad range of concentration (0.1 to up to 100 uM). There was no evidence of cytotoxicity, but interestingly, T cells differentiated into a phenotype resembling T central memory (CM) cells (CD44+, CD62L+) in a dose dependent manner as assessed by flow-cytometry. CM T cells were shown to induce superior anti-tumoral responses in comparison to ACT of Effector T cells in murine models. As expected for CM T cells, further analysis of 24 h collection supernatants from in vitro cognate peptide stimulated T cells showed dose-dependent lower interferon-gamma secretion with Vmf as analyzed by ELISA. Pmel-1 T cells were then analyzed by Immunoblotting for phosphorylation status (activation) of protein kinases at 1, 5, 15, 30 min and at 24h after Vmf treatment (concentrations from 1 to 15 uM). Vmf induced increased levels of pERK and pMEK. Co-immunoprecipitation studies and kinase assays further demonstrated a role of C-Raf in this paradoxical activation of the MAPK pathway in T cells induced by Vmf. Furthermore, in vivo studies in C57BL6 mice treated with Vmf daily or vehicle control for 3 weeks demonstrated skewing of CD3+ cells towards a phenotype resembling central memory T cells (CD44+, CD62L+, LY-6C+). Taken all our data together, we provide further support for the rationale of combining BRAF targeted therapy and adoptive T cell immunotherapy and the testing of such combinations in patients with V600E BRAF mutant metastatic melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3510. doi:1538-7445.AM2012-3510

PET imaging of cancer immunotherapy

Immune system activation can be elicited in viral infections, active immunization, or cancer immunotherapy, leading to the final common phenotype of increased glycolytic use by immune cells and subsequent detection by 18F-FDG PET. Because 18F-FDG is also used in baseline staging PET/CT scans and in tumor response assessment, physicians are faced with a unique challenge when evaluating tumor response in patients receiving cancer immunotherapy. The burgeoning field of cancer immunotherapy and the paucity of PET probes that can reliably differentiate activated immune cells from metabolically active cancer cells underscore the pressing need to identify and develop additional molecular imaging strategies. In an effort to address this concern, investigators have taken several molecular imaging approaches for cancer immunotherapy. Direct ex vivo labeling of T lymphocytes with radioactive probes before reinfusion represents the earliest attempts but has proven to be clinically limited because of significant PET probe dilution from proliferation of activated immune cells. Another approach is the indirect in vivo labeling of immune cells via PET reporter gene expression and involves the ex vivo genetic engineering of T lymphocytes with a reporter gene, reinfusion into the host, and the subsequent use of a PET probe specific for the reporter gene. The most recent approach involves the direct in vivo labeling of immune cells by targeting endogenous immune cell biochemical pathways that are differentially expressed during activation. In conclusion, these novel PET-based imaging approaches have demonstrated promise toward the goal of in vivo, noninvasive immune monitoring strategies for evaluating cancer immunotherapy.

Differentiation of vascular and non-vascular skin spectral signatures using in vivo hyperspectral radiometric imaging: implications for monitoring angiogenesis

Molecular imaging techniques can detect and monitor characteristics of the tumor microenvironment, such as angiogenesis, hypoxia, metabolism, and apoptosis that may better correlate with response to cancer therapy and may provide information in real-time. We investigated the use of a novel, spatially discrete, hyperspectral, multi-fiber optical system to characterize selected regions of skin in living mice. We determined the reproducibility and robustness of the spectral signatures derived from comparable regions of interest. Additionally, we characterized spectral differences in vascular and non-vascular fields to determine their potential use in monitoring angiogenesis. The macroscopic Prism and Reflectance Imaging Spectroscopy System (MACRO-PARISS) was calibrated against a National Institute for Standards and Technology (NIST)-certified lamp, allowing for reproducible spectra with any instrument similarly calibrated. Spectra were classified using a linearity-independent algorithm over a wavelength range of 450-920 nm. Classified spectra were integrated into a spectral library and subsequent acquisitions were correlated with the library set to a minimum correlation coefficient (MCC) of 99%. The results indicated that similar regions of interest with respect to vascularity consistently generated a unique spectral signature. As the field of view (FOV) moved from vascular to non-vascular areas, the acquired spectra changed in a step-wise and predictable fashion. Additionally, vascular fields that were deprived of their blood supply subsequently generated a non-vascular spectral signature. This work has implications for the monitoring of various physiologic or pathological processes including tumor angiogenesis and the therapeutic effects of anti-vascular agents.

Structural and Functional Imaging Correlates for Age-Related Changes in the Brain

In recent years, investigators have made significant progress in documenting brain structure and function as it relates to aging by using positron emission tomography, conventional magnetic resonance (MR) imaging, advanced MR techniques, and functional MR imaging. This review summarizes the latest advances in understanding physiologic maturation and aging as detected by these neuroimaging modalities. We also present our experience with MR volumetric and positron emission tomography analysis in separate cohorts of healthy subjects in the pediatric and adult age groups respectively. Our results are consistent with previous studies and include the following: total brain volume was found to increase with age (up to 20 years of age). Whole brain metabolism and frontal lobe metabolism both decrease significantly with age (38% and 42%, respectively), whereas cerebellar metabolism does not show a significant decline with age. Defining normal alterations in brain function and structure allows early detection of disorders such as Alzheimer's and Parkinson's diseases, which are commonly associated with normal aging.

Synthesis and biologic studies of iodinated (125I/127I) ethidium

An iodinated (125I/127I) ethidium derivative (3,8-diamino-5-[6'-(p-iodobenzoylamino)-4'-azahexyl]-6-phenylphenanthridinium chloride hydrochloride) was synthesized and characterized. The labeling yield of the 125I-labeled derivative was 75% for carrier-free 125I, with a radiochemical purity of 95%. The incubation of iodoethidium with calf thymus DNA resulted in a substantial enhancement of fluorescence yield, indicating the intercalation of this compound into DNA. In the presence of iodoethidium, the nuclei of methanol-treated mammalian cells fluoresced, while those of viable cells did not (since the plasma membrane is impermeable to iodoethidium). When viable cells were incubated with the reduced form of the derivative, 125I/127I-dihydroethidium traversed the plasma membrane, was oxidized in the cytoplasm, and intercalated into nuclear DNA. Finally, we tested the hypothesis that larger malignant solid tumors, containing a relatively greater percentage of degenerating permeable cells, can be targeted with 125I-ethidium. In-vivo studies demonstrated a small but positive correlation (R = 0.72) between tumor volume and the uptake of the derivative. Because of the ubiquitous presence of abnormal permeable cells and necrosis in tumors, our results support the belief that radiolabeled DNA-intercalating or DNA-binding molecules may be of diagnostic and therapeutic value for a variety of solid tumors in humans.