Marc S. Ernstoff

We read with interest the work by Olin and collaborators published in the Journal for ImmunoTherapy of Cancer under the title "Vaccination with dendritic cells loaded with allogeneic brain tumor cells for recurrent malignant brain tumors induces a CD4 + IL17+ response" [1]. Immune therapy trials for malignant brain tumors are challenging to undertake and there are many factors, including the high expense per patient which limits the number of patients enrolled, hence curtailing the ability to demonstrate that the intervention improves clinical outcomes. Furthermore, the baseline immune competence of patients with gliomas is heterogeneous and is an important variable in determining who will benefit from this therapeutic modality. Assessment of immune markers before treatment with immunotherapy which could reliably predict response is highly desirable, since patients unlikely to benefit could be considered for alternate clinical trials. Profiling the immune cell populations in peripheral blood by flow cytometry is a potentially useful tool, and hierarchical clustering analysis of the multiple cell populations measured may provide a distinct and comprehensive overview of the immune status [2]. Olin et al. use this methodology to separate patients with brain tumors who had stable or progressive disease after being treated with dendritic cells loaded with allogeneic tumor. We would like to bring to the attention of the authors and readership that in our 2011 publication, we applied hierarchical clustering to functional immune assay measures of antigen specific response to treatment with autologous tumor lysate loaded DC vaccination in a cohort of glioblastoma patients [3]. The shift of immune response measures discerned 2 groups of patients that correlated with survival.

Background Despite the positive impact of targeted therapies on metastatic renal cell carcinoma (mRCC), durable responses are infrequent and an unmet need exists for novel therapies with distinct mechanisms of action. We investigated the combination of recombinant Interleukin 21 (IL-21), a cytokine with unique immunostimulatory properties, plus sorafenib, a VEGFR tyrosine kinase inhibitor. Methods In this phase 1/2 study, 52 mRCC patients received outpatient treatment with oral sorafenib 400 mg twice daily plus intravenous IL-21 (10–50 mcg/kg) on days 1–5 and 15–19 of each 7-week treatment course. The safety, antitumor activity, pharmacokinetic and pharmacodynamic effects of the combination were evaluated. Results In phase 1 (n = 19), the maximum tolerated dose for IL-21 with the standard dose of sorafenib was determined to be 30 mcg/kg/day; grade 3 skin rash was the only dose-limiting toxicity. In phase 2, 33 previously-treated patients tolerated the combination therapy well with appropriate dose reductions; toxicities were mostly grade 1 or 2. The objective response rate was 21% and disease control rate was 82%. Two patients have durable responses that are ongoing, despite cessation of both IL-21 and sorafenib, at 41+ and 30+ months, respectively. The median progression-free survival in phase 2 was 5.6 months. The pharmacokinetic and pharmacodynamic properties of IL-21 appeared to be preserved in the presence of sorafenib. Conclusion IL-21 plus sorafenib has antitumor activity and acceptable safety in previously treated mRCC patients. IL-21 may represent a suitable immunotherapy in further exploration of combination strategies in mRCC. Trial registration ClinicalTrials.gov Identifier: NCT00389285

Among the dendritic cell (DC) subsets, plasmacytoid DC’s (pDC) are thought to be important in the generation of both antiviral and antitumor responses. While pDC may be useful in developing dendritic cell-based tumor vaccines, the low frequency of these cells in the peripheral blood has hampered attempts to understand their biology. To provide better insight into the biology of pDC, we isolated these unperturbed cells from the peripheral blood of healthy donors in order to further characterize their gene expression. Using gene array technology we compared the genetic profiles of these cells to those of CD14+ monocytes isolated from the same donors and found several immune related genes upregulated in this cell population. This is the first description, to our knowledge, of gene expression in this subset of DCs obtained from the peripheral blood of adult human donors without exposure in vitro to cytokine or growth factors. Understanding the natural genetic profiles of this dendritic cell subtype as well as others such as the BDCA-1 expressing myeloid DCs may enable us to manipulate these cells ex-vivo to generate enhanced DC-based tumor vaccines inducing more robust antitumor responses.

Lymphocytes are a key component of the immune system and their differentiation and function are directly influenced by cancer. We examined peripheral blood lymphocyte (PBL) gene expression as a biomarker of illness and treatment effect using the Affymetrix Human Gene ST1 platform in patients with metastatic renal cell carcinoma (mRCC) who received combined treatment with IL-2, interferon-?-2a and dendritic cell vaccine. We examined gene expression, cytokine levels in patient serum and lymphocyte subsets as determined by flow cytometry (FCM). Pre-treatment PBLs from patients with mRCC exhibit a gene expression profile and serum cytokine profile consistent with inflammation and proliferation not found in healthy donors (HD). PBL gene expression from patients with mRCC showed increased mRNA of genes involved with T-cell and T_REG-cell activation pathways, which was also reflected in lymphocyte subset distribution. Overall, PBL gene expression post-treatment (POST) was not significantly different than pre-treatment (PRE). Nevertheless, treatment related changes in gene expression (post-treatment minus pre-treatment) revealed an increased expression of T-cell and B-cell receptor signaling pathways in responding (R) patients compared to non-responding (NR) patients. In addition, we observed down-regulation of T_REG-cell pathways post-treatment in R vs. NR patients. While exploratory in nature, this study supports the hypothesis that enhanced inflammatory cytotoxic pathways coupled with blunting of the regulatory pathways is necessary for effective anti-cancer activity associated with immune therapy. This type of analysis can potentially identify additional immune therapeutic targets in patients with mRCC.

To evaluate CD4⁺CD25⁺FOXP3⁺ T regulatory cells (T_REG) and associated immune-regulatory pathways in peripheral blood lymphocytes (PBL) of metastatic renal cell carcinoma (mRCC) patients and healthy volunteers. We subsequently investigated the effects of immunotherapy on circulating T_REG combining an extensive phenotype examination, DNA methylation analysis and global transcriptome analysis. Eighteen patients with mRCC and twelve volunteers (controls) were available for analysis. T_REG phenotype was examined using flow cytometry (FCM). T_REG were also quantified by analyzing the epigenetic status of the FOXP3 locus using methylation specific PCR. As a third approach, RNA of the PBL was hybridized to Affymetrix GeneChip Human Gene 1.0 ST Arrays and the gene signatures were explored using pathway analysis. We observed higher numbers of T_REG in pre-treatment PBL of mRCC patients compared to controls. A significant increase in T_REG was detected in all mRCC patients after the two cycles of immunotherapy. The expansion of T_REG was significantly higher in non-responders than in responding patients. Methylation specific PCR confirmed the FCM data and circumvented the variability and subjectivity of the FCM method. Gene Set Enrichment Analysis (GSEA) of the microarray data showed significant enrichment of FOXP3 target genes, CTLA-4 and TGF-ß associated pathways in the patient cohort. Immune monitoring of the peripheral blood and tumor tissue is important for a wide range of diseases and treatment strategies. Adoption of methodology for quantifying T_REG with the least variability and subjectivity will enhance the ability to compare and interpret findings across studies.

Purpose: Recovery of lymphocyte populations after lymphocyte depletion is implicated in therapeutic immune pathways in animal models and in patients with cancer. We sought to evaluate the effects of chemotherapy-induced lymphodepletion followed by granulocyte-macrophage colony-stimulating factor (GM-CSF) and high-dose interleukin-2 (IL-2) therapy on clinical response and the recovery of lymphocyte subcompartments in patients with metastatic melanoma. Patients and Methods: This was a two-stage phase II trial design. Patients with measurable metastatic melanoma were treated with intravenous cyclophosphamide (60 mg/kg, days 1 and 2) and fludarabine (25 mg/m², day 3 through 7) followed by two 5-day courses of intravenous high-dose bolus IL-2 (600,000 U/kg; days 8 through 12 and 21 through 25). GM-CSF (250 μg/m²/d beginning day 8) was given until granulocyte recovery. Lymphocyte recovery profiles were determined by flow cytometric phenotyping at regular intervals, and clinical outcome was assessed by Response Evaluation Criteria in Solid Tumors (RECIST). Results: The trial was stopped at the end of stage 1 with four of 18 objective responses noted. Twelve patients had detailed lymphocyte subcompartments evaluated. After lymphodepletion, we observed an induction of regulatory cells (CD4+ T regulatory cells; CD8+ T suppressor cells) and of T memory cells (CD8+ T central memory cells; T effector memory RA+ cells). Expansion of circulating melanoma-specific CD8⁺ cells was observed in one of four HLA-A2-positive patients. Conclusion: Chemotherapy-induced lymphodepletion modulates the homeostatic repopulation of the lymphocyte compartment and influences recovering lymphocyte subpopulations. Clinical activity seems similar to standard high-dose aldesleukin alone.

Purpose: To evaluate the clinical and immunologic outcomes of DC (dendritic cell) vaccine with interleukin (IL)-2 and IFN-α 2a in metastatic renal cell carcinoma patients. Experimental Design: Eighteen consented and eligible patients were treated. Peripheral blood monocytes were cultured ex vivo into mature DCs and loaded with autologous tumor lysate. Treatment consisted of five cycles of intranodal vaccination of DCs (1 × 10⁷ cells/1 mL Lactated Ringer's solution), 5-day continuous i.v. infusion of IL-2 (18MiU/m²), and three s.c. injections of IFN-α 2a (6MiU) every other day. Response Evaluation Criteria in Solid Tumors criteria were used for disease assessment. Correlative immunologic end points included peripheral blood lymphocyte cell phenotype and function as well as peripheral blood anti–renal cell carcinoma antibody and cytokine levels. Results: All patients received between two and five treatment cycles. Toxicities consisted of known and expected cytokine side effects. Overall objective clinical response rate was 50% with three complete responses. Median time to progression for all patients was 8 months, and median survival has not been reached (median follow up of 37+ months). Treatment-related changes in correlative immunologic end points were noted and the level of circulating CD4⁺ T regulatory cells had a strong association with outcome. Pre–IP-10 serum levels approached significance for predicting outcome. Conclusions: The clinical and immunologic responses observed in this trial suggest an interaction between DC vaccination and cytokine therapy. Our data support the hypothesis that modulation of inflammatory, regulatory, and angiogenic pathways are necessary to optimize therapeutic benefit in renal cell carcinoma patients. Further exploration of this approach is warranted.