Major pathologic response on biopsy (MPRbx) in patients with advanced melanoma treated with anti-PD-1: evidence for an early, on-therapy biomarker of response.

BACKGROUND: With increasing anti-PD-1 therapy use in patients with melanoma and other tumor types, there is interest in developing early on-treatment biomarkers that correlate with long-term patient outcome. An understanding of the pathologic features of immune-mediated tumor regression is key in this endeavor. MATERIALS AND METHODS: Histologic features of immune-related pathologic response (irPR) following anti-PD-1 therapy were identified on hematoxylin and eosin (H&E)-stained slides in a discovery cohort of pre- and on-treatment specimens from n = 16 patients with advanced melanoma. These features were used to generate an irPR score [from 0 = no irPR features to 3 = major pathologic response on biopsy (MPRbx, ≤10% residual viable tumor)]. This scoring system was then tested for an association with objective response by RECIST1.1 and overall survival in a prospectively collected validation cohort of pre- and on-treatment biopsies (n = 51 on-treatment at 4-week timepoint) from melanoma patients enrolled on the nivolumab monotherapy arm of CA209-038 (NCT01621490). RESULTS: Specimens from responders in the discovery cohort had features of immune-activation (moderate-high TIL densities, plasma cells) and wound-healing/tissue repair (neovascularization, proliferative fibrosis) compared to nonresponders, (P ≤ 0.021, for each feature). In the validation cohort, increasing irPR score associated with objective response (P = 0.009) and MPRbx associated with increased overall survival (n = 51; HR 0.13; 95%CI, 0.054-0.31, P = 0.015). Neither tumoral necrosis nor pretreatment histologic features were associated with response. Eight of 16 (50%) of patients with stable disease showed irPR features, two of which were MPRbx, indicating a disconnect between pathologic and radiographic features at the 4-week on-therapy timepoint for some patients. CONCLUSIONS: Features of immune-mediated tumor regression on routine H&E-stained biopsy slides from patients with advanced melanoma correlate with objective response to anti-PD-1 and overall survival. An on-therapy biopsy may be particularly clinically useful for informing treatment decisions in patients with radiographic stable disease. This approach is inexpensive, straightforward, and widely available.

B7-1 engagement of cytotoxic T lymphocyte antigen 4 inhibits T cell activation in the absence of CD28.

Ligation of cytotoxic T lymphocyte antigen 4 (CTLA4) appears to inhibit T cell responses. Four mechanisms have been proposed to explain the inhibitory activity of CTLA4: competition for B7-1 and B7-2 binding by CD28; sequestration of signaling molecules away from CD28 via endocytosis; delivery of a signal that antagonizes a CD28 signal; and delivery of a signal that antagonizes a T cell receptor (TCR) signal. As three of these potential mechanisms involve functional antagonism of CD28, an experimental model was designed to determine whether CTLA4 could inhibit T cell function in the absence of CD28. TCR transgenic/recombinase activating gene 2-deficient/CD28-wild-type or CD28-deficient mice were generated and immunized with an antigen-expressing tumor. Primed T cells from both types of mice produced cytokines and proliferated in response to stimulator cells lacking B7 expression. However, whereas the response of CD28+/+ T cells was augmented by costimulation with B7-1, the response of the CD28-/- T cells was strongly inhibited. This inhibition was reversed by monoclonal antibody against B7-1 or CTLA4. Thus, CTLA4 can potently inhibit T cell activation in the absence of CD28, indicating that antagonism of a TCR-mediated signal is sufficient to explain the inhibitory effect of CTLA4.

Murine hepatic accessory cells support the proliferation of Th1 but not Th2 helper T lymphocyte clones.

The liver is the major site of clearance and degradation of foreign antigens from the portal circulation. Despite the presence of hepatic accessory cells, antibody responses to orally administered antigens are uncommon. To ascertain if hepatic accessory cells are incapable of stimulating specific subsets of T lymphocytes, freshly isolated hepatic nonparenchymal and splenic cells were cultured with a panel of antigen-specific, H-2-restricted Th1 and Th2 HTL clones. Whereas spleen cells stimulated the proliferation of both Th1 and Th2 clones, hepatic nonparenchymal cells (NPC) stimulated the proliferation of only Th1 and not Th2 clones. Adding rIL-1, rIL-6, and rIL-7, alone or in combination, to the cultures did not result in proliferation of the Th2 clones. Despite the absence of Th2 proliferation, NPC were able to stimulate the secretion of IL-3 and IL-4 by Th2 clones in the presence of antigen. Moreover, adding hepatic NPC did not inhibit spleen cells from stimulating Th2 clones in the presence of antigen. Thus, the inability of liver cells to stimulate the proliferation of Th2 helper T lymphocytes appears to be secondary to an absence of either an unknown accessory cell cofactor or an accessory cell that preferentially presents antigen to Th2 cells. The selective activation of Th1 and not Th2 cells by liver accessory cells may result in suppression of antibody responses to orally administered antigens.

"Anergy" of TH0 helper T lymphocytes induces downregulation of TH1 characteristics and a transition to a TH2-like phenotype.

Mature CD4+ helper T lymphocytes have been categorized into two major functional phenotypes, TH1 and TH2, which produce distinct arrays of lymphokines and which are thought to arise from a pluripotential precursor cell termed TH0. Clonal anergy can be induced in TH1 clones by stimulating via the T cell receptor (TCR) complex in the absence of a costimulator molecule; however, anergy has been difficult to demonstrate in TH2 clones. We show here that treatment of cloned TH0 lines with anergizing stimuli results in the selective loss of TH1 characteristics and retention of a TH2 phenotype. Treated cells exhibit a substantial reduction in interleukin 2 (IL-2) production and antigen-specific cytolytic activity, but retain comparable IL-4 and IL-5 production in response to restimulation via the TCR complex. TH0 clones exposed to anergizing stimuli also increase in size, thus morphologically resembling TH2 cells. The signaling characteristics of these cells also are altered, in that they exhibit an elevated basal level of intracellular free calcium which fails to increase significantly with subsequent restimulation, reminiscent of the signaling characteristics of TH2 cells. "Anergized" TH0 clones thus share several functional, morphologic, and physiologic properties with cells of the TH2 phenotype, suggesting that TH2 cells may arise when TH0 cells are stimulated via the TCR complex in the absence of a putative costimulator molecule.

Efficacy and safety of ipilimumab monotherapy in patients with pretreated advanced melanoma: a multicenter single-arm phase II study.

BACKGROUND: This phase II study evaluated the safety and activity of ipilimumab, a fully human mAb that blocks cytotoxic T-lymphocyte antigen-4, in patients with advanced melanoma. PATIENTS AND METHODS: Patients with previously treated, unresectable stage III/stage IV melanoma received 10 mg/kg ipilimumab every 3 weeks for four cycles (induction) followed by maintenance therapy every 3 months. The primary end point was best overall response rate (BORR) using modified World Health Organization (WHO) criteria. We also carried out an exploratory analysis of proposed immune-related response criteria (irRC). RESULTS: BORR was 5.8% with a disease control rate (DCR) of 27% (N = 155). One- and 2-year survival rates (95% confidence interval) were 47.2% (39.5% to 55.1%) and 32.8% (25.4% to 40.5%), respectively, with a median overall survival of 10.2 months (7.6-16.3). Of 43 patients with disease progression by modified WHO criteria, 12 had disease control by irRC (8% of all treated patients), resulting in a total DCR of 35%. Adverse events (AEs) were largely immune related, occurring mainly in the skin and gastrointestinal tract, with 19% grade 3 and 3.2% grade 4. Immune-related AEs were manageable and generally reversible with corticosteroids. CONCLUSION: Ipilimumab demonstrated clinical activity with encouraging long-term survival in a previously treated advanced melanoma population.

Microbiome-based interventions: therapeutic strategies in cancer immunotherapy.

The composition of the commensal microbiota has recently emerged as a key element influencing the efficacy of cancer treatments. It has become apparent that the interplay between the microbiome and immune system within the host influences the response to immunotherapy, particularly immune checkpoint inhibitor therapy. Identifying the key components of the gut microbiota that influence this response is paramount for designing therapeutic interventions to enhance the response to cancer therapy. This review will discuss strategies being considered to modulate the gut microbiota, including fecal microbiota transplantation, administration of defined bacterial isolates as well as bacterial consortia, supplementation with probiotics, and lifestyle modifications such as dietary changes. Understanding the influence of the complex variables of the human microbiota on the effectiveness of cancer therapy will help drive the clinical design of microbial-based interventions in the field of oncology.

Blocked Ras activation in anergic CD4+ T cells.

T cell anergy is a state of functional unresponsiveness characterized by the inability to produce interleukin-2 (IL-2) upon T cell receptor stimulation. The mitogen-activated protein kinases ERK-1 and ERK-2 and the guanosine triphosphate-binding protein p21ras were found to remain unactivated upon stimulation of anergic murine T helper cell 1 clones. The inability to activate the Ras pathway did not result from a defect in association among Shc, Grb-2, and murine Son of Sevenless, nor from a defect in their tyrosine phosphorylation. This block in Ras activation may lead to defective transactivation at activator protein 1 sites in anergic cells and may enable T cells to shut down IL-2 production selectively during anergy.

Long-term follow-up of nonmyeloablative allogeneic stem cell transplantation for renal cell carcinoma: The University of Chicago Experience.

Nonmyeloablative allogeneic stem cell transplantation (NST) has considerable activity in patients with metastatic renal cell carcinoma (RCC), although there are limited long-term follow-up data. Between February 1999 and May 2003, 18 patients with metastatic RCC underwent 19 matched-sibling NSTs after conditioning with fludarabine and cyclophosphamide with tacrolimus and mycophenolate mofetil as post-transplant immunosuppression. Among the four objective responses, all were partial and have relapsed with a median response duration of 609 days (range, 107-926). All responders are alive at a median of 41 months. Median overall survival for the entire cohort was 14 months. There were four early treatment-related deaths and one late treatment-related death. Eight patients died from progressive disease and five (28%) from treatment-related mortality. Stratifying transplant outcome as early death, intermediate (no response, no early death), or response, the combination of pre-treatment anemia and decreased performance status, was associated with adverse outcome (P = 0.015) and reduced survival (HR 5.4, 95% confidence interval of 1.4 to 21, P = 0.007). Responders demonstrated prolonged survival compared to nonresponders (P = 0.002). NST leads to durable responses in a minority of metastatic RCC patients. Appropriate patient selection is paramount. Anemia and decreased performance status may enable risk stratification.

Immunization of HLA-A2+ melanoma patients with MAGE-3 or MelanA peptide-pulsed autologous peripheral blood mononuclear cells plus recombinant human interleukin 12.

Vaccination with dendritic cells (DCs) pulsed with tumor antigen peptides has shown promise in the treatment of melanoma. Interleukin (IL)-12 production by DCs is a key component for their efficacy. Murine studies have shown that IL-12 promotes potent antitumor immunization when coadministered with peptides loaded onto other class I MHC+ cells, thus bypassing the need to use DCs. The easiest cell source to obtain in large quantity from human patients is peripheral blood mononuclear cells (PBMCs). A Phase I clinical trial was thus performed in patients with metastatic melanoma using immunization with autologous PBMCs pulsed with a MAGE-3 or a MelanA peptide, coadministered with various doses of recombinant human (rh)IL-12. Patients receiving low-to-moderate doses of rhIL-12 developed increased specific CD8+ T-cell responses. Of the eight patients showing increased immunity, six had evidence of clinical activity, with one complete, one partial, one minor, and three mixed responses observed. In two patients with mixed responses, growing tumors were found to lack expression of the antigen used to immunize. Thus, vaccination with peptide-pulsed PBMCs plus rhIL-12 induces specific immunity and has clinical activity, without the need to generate DCs. Outgrowth of antigen-negative tumors argues for the future development of polyepitope vaccines.

Control of T lymphocyte signal transduction through clonal anergy.

Stimulation of interleukin-2 producing T lymphocytes via the T cell receptor (TCR) complex in the absence of other costimulatory factor results paradoxically not in activation but in an unresponsive state termed clonal anergy. T cell anergy appears to be a mechanism by which potentially autoreactive T lymphocytes are inactivated in the periphery, thus maintaining tolerance to self antigens. The breakdown of such tolerance may result in autoimmune diseases. In contrast, induction of peripheral tolerance is the ultimate goal in organ transplantation and is a potential mechanism by which a growing tumor evades immune destruction. The anergic state is characterized by an inability to secrete interleukin-2 and proliferate following restimulation via the TCR even in the presence of constimulatory factors. Recent studies have demonstrated a specific block in Ras activation in anergic T lymphocytes. This defect is correlated with a failure to activate the downstream effectors Erk and Jnk and a lack of activation of the AP-1 transcription factor complex, offering a plausible mechanism for the inability to initiate interleukin-2 gene transcription in the anergic state.

Non-redundant requirement for CXCR3 signalling during tumoricidal T-cell trafficking across tumour vascular checkpoints.

T-cell trafficking at vascular sites has emerged as a key step in antitumour immunity. Chemokines are credited with guiding the multistep recruitment of CD8(+) T cells across tumour vessels. However, the multiplicity of chemokines within tumours has obscured the contributions of individual chemokine receptor/chemokine pairs to this process. Moreover, recent studies have challenged whether T cells require chemokine receptor signalling at effector sites. Here we investigate the hierarchy of chemokine receptor requirements during T-cell trafficking to murine and human melanoma. These studies reveal a non-redundant role for Gαi-coupled CXCR3 in stabilizing intravascular adhesion and extravasation of adoptively transferred CD8(+) effectors that is indispensable for therapeutic efficacy. In contrast, functional CCR2 and CCR5 on CD8(+) effectors fail to support trafficking despite the presence of intratumoral cognate chemokines. Taken together, these studies identify CXCR3-mediated trafficking at the tumour vascular interface as a critical checkpoint to effective T-cell-based cancer immunotherapy.

Clinical responses following nonmyeloablative allogeneic stem cell transplantation for renal cell carcinoma are associated with expansion of CD8+ IFN-gamma-producing T cells.

Nonmyeloablative allogeneic stem cell transplantation (NST) is thought to be an immunologic therapy in which donor T cells mediate a graft-versus-tumor effect. We recently reported the clinical outcome of a phase II trial of NST in metastatic renal cell carcinoma (RCC). However, the immune response correlates of clinical activity remain unknown. We now describe the analysis of T-cell subsets and T-cell cytokine-producing potential for those patients evaluable for immune monitoring. The incidence of graft-versus-host disease (GVHD) correlated with clinical outcome, with all responders exhibiting chronic GVHD. Following initial tapering of immunosuppression, an increase in the total numbers of CD8+ T cells but not CD4+ T cells was observed among responders compared to nonresponders. In addition, a greater ratio of CD8+ to CD4+ T cells producing IFN-gamma and IL-2 was seen in clinical responders at the time when clinical responses were first detected (day 180 after transplantation). Our results support the hypothesis that the antitumor effects of NST may be mediated by IFN-gamma-producing CD8+ T cells, and indicate that isolation of putative tumor antigen-specific T cells, ideally, should be pursued around day +180.

Peripheral survival of naïve CD8+ T cells.

Maintenance of a sufficient population of naive CD8+ T cells in the peripheral lymphoid compartment is critical for immunocompetence. Peripheral T cell number is a function of T cell generation, survival, and death. Homeostasis, a critical balance between survival and death, must exist to prevent either lymphopenia or lymphocytosis. In the current review, we discuss known requirements for the survival of naive peripheral CD8+ T cells as well as mechanisms of death when survival signals are lost. We also discuss associations between survival and homeostasis-driven proliferation, and highlight the gaps in our knowledge of these critical processes.

B7-1 but not B7-2 efficiently costimulates CD8+ T lymphocytes in the P815 tumor system in vitro.

We recently have developed a method to generate primary P815-specific CTL in vitro from normal syngeneic splenocytes by employing transfection of B7-1 combined with exogenous IL-12 and IL-6. Surprisingly, when the homologous costimulator molecule B7-2 was substituted for B7-1 in this system, no specific CTL activity was obtained. Similarly, B7-1- but not B7-2-transfected P815 cells generated alloantigen-specific CTL activity from C57BL/6, accessory cell- and CD4(+)-depleted splenocytes, and costimulated proliferation of CD8+ lymphocytes in the presence of low doses of anti-CD3 mAb. In all systems, combined expression of both B7-1 and B7-2 costimulated as effectively as B7-1 alone, arguing against delivery of a dominant negative signal by B7-2. Proliferation of allogeneic, CD4(+)-depleted splenocytes in response to P815 cells, which relies on costimulation by normal accessory cells, was inhibited by anti-B7-1 but not anti-B7-2 mAbs. Finally, indirect evidence suggested a higher avidity of B7-1+ cells than B7-2+ cells for CTLA4. Thus, at least in the context of primary stimulation by irradiated P815 transfectants, B7-1 appears to be superior to B7-2 at costimulation of CD8+ T lymphocytes.

Anti-proliferative effect of IFN-gamma in immune regulation. I. IFN-gamma inhibits the proliferation of Th2 but not Th1 murine helper T lymphocyte clones.

A biphasic dose-response curve was observed when the IL-1-dependent HTL clone D10 was exposed to IL-1 plus supernatants from some activated T cell clones but not others. The active component that inhibited proliferation at high concentrations of these supernatants appeared to be IFN-gamma based on the following findings: 1) the biphasic pattern of responsiveness correlated with the presence of IFN-gamma in the supernatants; 2) an anti-IFN-gamma mAb augmented the proliferation of D10 cells to these supernatants; 3) rIFN-gamma inhibited profoundly the response of D10 cells stimulated with rIL-1 plus supernatant from activated D10 cells or with rIL-1 plus rIL-4; 4) the response of D10 cells to rIL-1 plus rIL-2 also was inhibited by rIFN-gamma, although to a lesser extent. The proliferation of an additional Th2 clone stimulated with rIL-1 plus rIL-4 or rIL-2 also was inhibited by rIFN-gamma, implicating IFN-gamma as an inhibitory lymphokine for Th2 cells in general. rIFN-gamma did not affect the proliferation of two Th1 clones, nor did it affect the proliferation of an unconventional HTL clone which produces both IL-4 and IFN-gamma and proliferates in response to IL-2 or IL-4 in an IL-1-independent fashion. The proliferation of D10 cells stimulated by Ag or by immobilized anti-CD3 antibody also was blocked by rIFN-gamma, whereas IL-4 production in response to these stimuli was unaffected, indicating that proliferation and not general cell function was specifically inhibited. Collectively, these data implicate IFN-gamma as a suppressive factor for the proliferation of the subset of HTL designated Th2, and suggest that the relative amounts of the various lymphokines present during an immune response may direct which T cell types increase in number.

The immune system as anti-tumor sentinel: molecular requirements for an anti-tumor immune response.

The concept behind immune surveillance against cancer is that tumor cells continuously develop, but that there may not be clinical evidence of their presence because the immune system recognizes the cells as foreign and destroys them. A clear role for the immune system in preventing and/or eliminating tumors is emerging as insights into the molecular requirements for the induction and effector function of cytolytic T lymphocytes (CTL) have been gained. Using murine tumor rejection models, the role of particular molecular components of the immune system in controlling tumor growth has been defined. However, tumor rejection does not always occur spontaneously in vivo, indicating that defects in the generation or execution of an anti-tumor immune response may be common. Understanding defects when they arise should allow for development of new therapeutic approaches in tumor-bearing individuals. Many clinical studies are underway to test strategies to induce or heighten an antitumor immune response in cancer patients.

Cutting edge: differentiation of antitumor CTL in vivo requires host expression of Stat1.

Several lines of evidence suggest that an IFN-gamma-producing, Th1/Tc1 phenotype may be optimal for tumor rejection. Recent work has indicated that IFN signaling on tumor cells is important for protection against carcinogenesis. However, the potential involvement of IFN signaling among host immune cells has not been carefully examined. To this end, Stat1-deficient mice were employed as tumor recipients. In contrast to wild-type mice, Stat1-/- mice failed to reject immunogenic tumors and did not support regression of poorly immunogenic tumors when treated with an IL-12-based vaccine. T cells from immunized Stat1-/- mice produced 50% of the levels of IFN-gamma and lacked cytolytic activity compared with wild-type mice, and NK lytic activity also was not observed. Lack of cytolytic function correlated with a failure to up-regulate serine esterase activity. Thus, IFN-mediated signaling on host cells is required for the development of antitumor lytic effector cells.

Rational development of tumour antigen-specific immunization in melanoma.

The identification and molecular characterization of antigens expressed on tumour cells, but not on most normal host tissues, has opened the possibility of specific immunization in the therapy of cancer, particularly of melanoma. Most antigens defined are class I MHC-binding peptides recognized by CD8+ cytolytic T lymphocytes (CTL). Methodologies for active immunization to induce effective anti-tumour CTL are under development in a number of laboratories, and some of these approaches have entered clinical trials. Optimization of the anti-tumour immune response will depend on a thorough knowledge of the signals required for T cell activation, differentiation, and inactivation.

Polymyositis with respiratory muscle weakness requiring mechanical ventilation in a patient with metastatic thymoma treated with octreotide.

Although most patients with thymoma present with a mediastinal mass amenable to surgical resection, some patients develop metastatic disease requiring systemic therapy. The majority of thymomas express somatostatin receptors as demonstrated by octreotide scanning, an observation which has prompted the clinical use of octreotide in patients with this disease. Many patients with thymoma exhibit autoimmune paraneoplastic syndromes, most frequently myesthenia gravis. We report here the case of a patient with metastatic thymoma who developed a profound autoimmune polymyositis and lupus-like syndrome that flared following treatment with octreotide and was associated with a clinical response to this agent. No evidence for myesthenia gravis was discovered. The severity of the myopathy necessitated mechanical ventilation for 12 weeks. The natural history of thymoma, treatment options including recent combination chemotherapy regimens, and potential mechanisms for flaring of autoimmune paraneoplastic syndromes triggered by therapy of thymoma are discussed.