Phase 1/2 study of epacadostat in combination with durvalumab in patients with metastatic solid tumors.

BACKGROUND: Targeting programmed cell death protein 1 (PD-1) and indoleamine 2,3-dioxygenase (IDO1) pathways is an appealing option for cancer treatment. METHODS: The open-label, phase 1/2 ECHO-203 study evaluated the safety, tolerability, and efficacy of the IDO1 inhibitor epacadostat in combination with durvalumab, a human anti-PD-L1 monoclonal antibody in adult patients with advanced solid tumors. RESULTS: The most common treatment-related adverse events were fatigue (30.7%), nausea (21.0%), decreased appetite (13.1%), pruritus (12.5%), maculopapular rash (10.8%), and diarrhea (10.2%). Objective response rate (ORR) in the overall phase 2 population was 12.0%. Higher ORR was observed in immune checkpoint inhibitor (CPI)-naïve patients (16.1%) compared with patients who had received previous CPI (4.1%). Epacadostat pharmacodynamics were evaluated by comparing baseline kynurenine levels with those on therapy at various time points. Only the 300-mg epacadostat dose showed evidence of kynurenine modulation, albeit unsustained. CONCLUSIONS: Epacadostat plus durvalumab was generally well tolerated in patients with advanced solid tumors. ORR was low, and evaluation of kynurenine concentration from baseline to cycle 2, day 1, and cycle 5, day 1, suggested >300 mg epacadostat twice daily is needed to ensure sufficient drug effect. CLINICAL TRIAL INFORMATION: A study of epacadostat (INCB024360) in combination with durvalumab (MEDI4736) in subjects with selected advanced solid tumors (ECHO-203) (NCT02318277).

Leukemia-Associated Rho Guanine Nucleotide Exchange Factor and Ras Homolog Family Member C Play a Role in Glioblastoma Cell Invasion and Resistance.

Glioblastoma (GBM) is the most common primary malignant brain cancer in adults. A hallmark of GBM is aggressive invasion of tumor cells into the surrounding normal brain. Both the current standard of care and targeted therapies have largely failed to specifically address this issue. Therefore, identifying key regulators of GBM cell migration and invasion is important. The leukemia-associated Rho guanine nucleotide exchange factor (LARG) has previously been implicated in cell invasion in other tumor types; however, its role in GBM pathobiology remains undefined. Herein, we report that the expression levels of LARG and ras homolog family members C (RhoC), and A (RhoA) increase with glial tumor grade and are highest in GBM. LARG and RhoC protein expression is more prominent in invading cells, whereas RhoA expression is largely restricted to cells in the tumor core. Knockdown of LARG by siRNA inhibits GBM cell migration in vitro and invasion ex vivo in organotypic brain slices. Moreover, siRNA-mediated silencing of RhoC suppresses GBM cell migration in vitro and invasion ex vivo, whereas depletion of RhoA enhances GBM cell migration and invasion, supporting a role for LARG and RhoC in GBM cell migration and invasion. Depletion of LARG increases the sensitivity of GBM cells to temozolomide treatment. Collectively, these results suggest that LARG and RhoC may represent unappreciated targets to inhibit glioma invasion.

Distinct predictive biomarker candidates for response to anti-CTLA-4 and anti-PD-1 immunotherapy in melanoma patients.

BACKGROUND: While immune checkpoint blockade has greatly improved clinical outcomes in diseases such as melanoma, there remains a need for predictive biomarkers to determine who will likely benefit most from which therapy. To date, most biomarkers of response have been identified in the tumors themselves. Biomarkers that could be assessed from peripheral blood would be even more desirable, because of ease of access and reproducibility of sampling. METHODS: We used mass cytometry (CyTOF) to comprehensively profile peripheral blood of melanoma patients, in order to find predictive biomarkers of response to anti-CTLA-4 or anti-PD-1 therapy. Using a panel of ~ 40 surface and intracellular markers, we performed in-depth phenotypic and functional immune profiling to identify potential predictive biomarker candidates. RESULTS: Immune profiling of baseline peripheral blood samples using CyTOF revealed that anti-CTLA-4 and anti-PD-1 therapies have distinct sets of candidate biomarkers. The distribution of CD4+ and CD8+ memory/non-memory cells and other memory subsets was different between responders and non-responders to anti-CTLA-4 therapy. In anti-PD-1 (but not anti-CTLA-4) treated patients, we discovered differences in CD69 and MIP-1ß expressing NK cells between responders and non-responders. Finally, multivariate analysis was used to develop a model for the prediction of response. CONCLUSIONS: Our results indicate that anti-CTLA-4 and anti-PD-1 have distinct predictive biomarker candidates. CD4+ and CD8+ memory T cell subsets play an important role in response to anti-CTLA-4, and are potential biomarker candidates. For anti-PD-1 therapy, NK cell subsets (but not memory T cell subsets) correlated with clinical response to therapy. These functionally active NK cell subsets likely play a critical role in the anti-tumor response triggered by anti-PD-1.

Deep Sequencing of T-cell Receptor DNA as a Biomarker of Clonally Expanded TILs in Breast Cancer after Immunotherapy.

In early-stage breast cancer, the degree of tumor-infiltrating lymphocytes (TIL) predicts response to chemotherapy and overall survival. Combination immunotherapy with immune checkpoint antibody plus tumor cryoablation can induce lymphocytic infiltrates and improve survival in mice. We used T-cell receptor (TCR) DNA sequencing to evaluate both the effect of cryoimmunotherapy in humans and the feasibility of TCR sequencing in early-stage breast cancer. In a pilot clinical trial, 18 women with early-stage breast cancer were treated preoperatively with cryoablation, single-dose anti-CTLA-4 (ipilimumab), or cryoablation + ipilimumab. TCRs within serially collected peripheral blood and tumor tissue were sequenced. In baseline tumor tissues, T-cell density as measured by TCR sequencing correlated with TIL scores obtained by hematoxylin and eosin (H&E) staining. However, tumors with little or no lymphocytes by H&E contained up to 3.6 × 106 TCR DNA sequences, highlighting the sensitivity of the ImmunoSEQ platform. In this dataset, ipilimumab increased intratumoral T-cell density over time, whereas cryoablation ± ipilimumab diversified and remodeled the intratumoral T-cell clonal repertoire. Compared with monotherapy, cryoablation plus ipilimumab was associated with numerically greater numbers of peripheral blood and intratumoral T-cell clones expanding robustly following therapy. In conclusion, TCR sequencing correlates with H&E lymphocyte scoring and provides additional information on clonal diversity. These findings support further study of the use of TCR sequencing as a biomarker for T-cell responses to therapy and for the study of cryoimmunotherapy in early-stage breast cancer. Cancer Immunol Res; 4(10); 835-44. ©2016 AACR.

A Pilot Study of Preoperative Single-Dose Ipilimumab and/or Cryoablation in Women with Early-Stage Breast Cancer with Comprehensive Immune Profiling.

PURPOSE: To assess the safety and tolerability of preoperative cryoablation-mediated tumor antigen presentation and/or ipilimumab-mediated immune modulation in women with operable breast cancer. EXPERIMENTAL DESIGN: In this pilot study, 19 women with breast cancer for whom mastectomy was planned were treated with preoperative tumor cryoablation (n = 7), single-dose ipilimumab at 10 mg/kg (n = 6), or both (n = 6). The primary outcome for this pilot study was safety/tolerability as defined as freedom from delays in pre-planned, curative-intent mastectomy. Exploratory studies of immune activation were performed on peripheral blood and tumor. RESULTS: Preoperative cryoablation and/or ipilimumab were safe and tolerable, with no delays in pre-planned surgery. Grade III toxicity was seen in 1 of 19 (unrelated rash after ipilimumab). Combination therapy was associated with sustained peripheral elevations in: Th1-type cytokines, activated (ICOS+) and proliferating (Ki67+) CD4+ and CD8+ T cells, and posttreatment proliferative T-effector cells relative to T-regulatory cells within tumor. CONCLUSIONS: Preoperative cryoablation and single-dose ipilimumab are safe alone or in combination with no surgical delays incurred. Potentially favorable intratumoral and systemic immunologic effects were observed with the combination, suggesting the possibility for induced and synergistic antitumor immunity with this strategy. Clin Cancer Res; 22(23); 5729-37. ©2016 AACR.

Peripheral T cell receptor diversity is associated with clinical outcomes following ipilimumab treatment in metastatic melanoma.

BACKGROUND: Ipilimumab improves overall survival in a subset of patients with metastatic melanoma. Peripheral blood T cell receptor (TCR) repertoire diversity has been associated with favorable outcomes in patients with cancer, but its relevance as a biomarker for ipilimumab outcomes remains unknown. FINDINGS: In this pilot study, we analyzed the pre-treatment peripheral blood TCR repertoire in 12 patients with metastatic melanoma who received ipilimumab at 3 mg/kg (clinical benefit, n = 4; no clinical benefit, n = 8). TCR diversity was evaluated using a polymerase chain reaction assay which measures TCR combinatorial diversity between V and J genes from genomic DNA. TCR repertoire diversity was studied through richness (observed V-J rearrangements) and evenness (similarity between the frequencies of specific V-J rearrangements). The Wilcoxon rank sum test was used to compare patients with clinical benefit and those without. Association with benefit in a dichotomized analysis was assessed through a Fisher's exact test. Overall survival was studied through log-rank analysis. There was a significant difference in richness (p = 0.033) and evenness (p = 0.028) between patients with and without clinical benefit. Dichotomized analysis showed that none of the patients with low richness (n = 0/5, p = 0.081) nor low evenness (n = 0/7, p = 0.01) achieved clinical benefit. There were no significant differences in overall survival. CONCLUSIONS: In this small group of patients, baseline TCR diversity in the peripheral blood was associated with clinical outcomes. Further investigation is ongoing in larger cohorts of patients to explore these preliminary findings and determine whether TCR diversity can be used as a predictive biomarker in cancer immunotherapy.

Pretreatment serum VEGF is associated with clinical response and overall survival in advanced melanoma patients treated with ipilimumab.

Ipilimumab, an antibody that blocks CTL antigen 4 (CTLA-4), improves overall survival (OS) for patients with metastatic melanoma. Given its role in angiogenesis and immune evasion, serum VEGF levels were evaluated for association with clinical benefit in ipilimumab-treated patients. Sera were collected from 176 patients treated at 3 (n = 98) or 10 mg/kg (n = 68). The VEGF levels before treatment and at induction completion (week 12) were analyzed using the Meso Scale Discovery kit. The association of the levels of VEGF with clinical responses and OS were assessed using the Fisher exact and Kaplan-Meier log-rank tests. VEGF as a continuous variable was associated with OS (P = 0.002). Using 43 pg/mL as the cutoff pretreatment VEGF value defined by maximally selected log-rank statistics, pretreatment VEGF values correlated with clinical benefit at week 24 (P = 0.019; 159 patients evaluable). Pretreatment VEGF ≥ 43 pg/mL was associated with decreased OS (median OS 6.6 vs. 12.9 months, P = 0.006; 7.4 vs. 14.3 months, P = 0.037 for 3 mg/kg; and 6.2 vs. 10.9 months, P = 0.048 for 10 mg/kg). There was no correlation between VEGF changes and clinical outcome. Serum VEGF may be a predictive biomarker for ipilimumab treatment and is worthy of prospective investigation with various forms of immunologic checkpoint blockade.

The MLK-related kinase (MRK) is a novel RhoC effector that mediates lysophosphatidic acid (LPA)-stimulated tumor cell invasion.

The small GTPase RhoC is overexpressed in many invasive tumors and is essential for metastasis. Despite its high structural homology to RhoA, RhoC appears to perform functions that are different from those controlled by RhoA. The identity of the signaling components that are differentially regulated by these two GTPases is only beginning to emerge. Here, we show that the MAP3K protein MRK directly binds to the GTP-bound forms of both RhoA and RhoC in vitro. However, siRNA-mediated depletion of MRK in cells phenocopies depletion of RhoC, rather than that of RhoA. MRK depletion, like that of RhoC, inhibits LPA-stimulated cell invasion, while depletion of RhoA increases invasion. We also show that active MRK enhances LPA-stimulated invasion, further supporting a role for MRK in the regulation of invasion. Depletion of either RhoC or MRK causes sustained myosin light chain phosphorylation after LPA stimulation. In addition, activation of MRK causes a reduction in myosin light chain phosphorylation. In contrast, as expected, depletion of RhoA inhibits myosin light chain phosphorylation. We also present evidence that both RhoC and MRK are required for LPA-induced stimulation of the p38 and ERK MAP kinases. In conclusion, we have identified MRK as a novel RhoC effector that controls LPA-stimulated cell invasion at least in part by regulating myosin dynamics, ERK and p38.

Role of a DNA damage checkpoint pathway in ionizing radiation-induced glioblastoma cell migration and invasion.

Ionizing radiation (IR) induces a DNA damage response that includes activation of cell cycle checkpoints, leading to cell cycle arrest. In addition, IR enhances cell invasiveness of glioblastoma cells, among other tumor cell types. Using RNA interference, we found that the protein kinase MRK, previously implicated in the DNA damage response to IR, also inhibits IR-induced cell migration and invasion of glioblastoma cells. We showed that MRK activation by IR requires the checkpoint protein Nbs1 and that Nbs1 is also required for IR-stimulated migration. In addition, we show that MRK acts upstream of Chk2 and that Chk2 is also required for IR-stimulated migration and invasion. Thus, we have identified Nbs1, MRK, and Chk2 as elements of a novel signaling pathway that mediates IR-stimulated cell migration and invasion. Interestingly, we found that inhibition of cell cycle progression, either with the CDK1/2 inhibitor CGP74514A or by downregulation of the CDC25A protein phosphatase, restores IR-induced migration and invasion in cells depleted of MRK or Chk2. These data indicate that cell cycle progression, at least in the context of IR, exerts a negative control on the invasive properties of glioblastoma cells and that checkpoint proteins mediate IR-induced invasive behavior by controlling cell cycle arrest.

ATM mediates oxidative stress-induced dephosphorylation of DNA ligase IIIalpha.

Among the three mammalian genes encoding DNA ligases, only the LIG3 gene does not have a homolog in lower eukaryotes. In somatic mammalian cells, the nuclear form of DNA ligase IIIalpha forms a stable complex with the DNA repair protein XRCC1 that is also found only in higher eukaryotes. Recent studies have shown that XRCC1 participates in S phase-specific DNA repair pathways independently of DNA ligase IIIalpha and is constitutively phosphorylated by casein kinase II. In this study we demonstrate that DNA ligase IIIalpha, unlike XRCC1, is phosphorylated in a cell cycle-dependent manner. Specifically, DNA ligase IIIalpha is phosphorylated on Ser123 by the cell division cycle kinase Cdk2 beginning early in S phase and continuing into M phase. Interestingly, treatment of S phase cells with agents that cause oxygen free radicals induces the dephosphorylation of DNA ligase IIIalpha. This oxidative stress-induced dephosphorylation of DNA ligase IIIalpha is dependent upon the ATM (ataxia-telangiectasia mutated) kinase and appears to involve inhibition of Cdk2 and probably activation of a phosphatase.

Physical and functional interaction between DNA ligase IIIalpha and poly(ADP-Ribose) polymerase 1 in DNA single-strand break repair.

The repair of DNA single-strand breaks in mammalian cells is mediated by poly(ADP-ribose) polymerase 1 (PARP-1), DNA ligase IIIalpha, and XRCC1. Since these proteins are not found in lower eukaryotes, this DNA repair pathway plays a unique role in maintaining genome stability in more complex organisms. XRCC1 not only forms a stable complex with DNA ligase IIIalpha but also interacts with several other DNA repair factors. Here we have used affinity chromatography to identify proteins that associate with DNA ligase III. PARP-1 binds directly to an N-terminal region of DNA ligase III immediately adjacent to its zinc finger. In further studies, we have shown that DNA ligase III also binds directly to poly(ADP-ribose) and preferentially associates with poly(ADP-ribosyl)ated PARP-1 in vitro and in vivo. Our biochemical studies have revealed that the zinc finger of DNA ligase III increases DNA joining in the presence of either poly(ADP-ribosyl)ated PARP-1 or poly(ADP-ribose). This provides a mechanism for the recruitment of the DNA ligase IIIalpha-XRCC1 complex to in vivo DNA single-strand breaks and suggests that the zinc finger of DNA ligase III enables this complex and associated repair factors to locate the strand break in the presence of the negatively charged poly(ADP-ribose) polymer.