Bruton's tyrosine kinase: an emerging targeted therapy in myeloid cells within the tumor microenvironment

Bruton’s tyrosine kinase (BTK) is a non-receptor kinase belonging to the Tec family of kinases. The role of BTK in B cell receptor signaling is well defined and is known to play a key role in the proliferation and survival of malignant B cells. Moreover, BTK has been found to be expressed in cells of the myeloid lineage. BTK has been shown to contribute to a variety of cellular pathways in myeloid cells including signaling in the NLRP3 inflammasome, receptor activation of nuclear factor-κβ and inflammation, chemokine receptor activation affecting migration, and phagocytosis. Myeloid cells are crucial components of the tumor microenvironment and suppressive myeloid cells contribute to cancer progression, highlighting a potential role for BTK inhibition in the treatment of malignancy. The increased interest in BTK inhibition in cancer has resulted in many preclinical studies that are testing the efficacy of using single-agent BTK inhibitors. Moreover, the ability of tumor cells to develop resistance to single-agent checkpoint inhibitors has resulted in clinical studies utilizing BTK inhibitors in combination with these agents to improve clinical responses. Furthermore, BTK regulates the immune response in microbial and viral infections through B cells and myeloid cells such as monocytes and macrophages. In this review, we describe the role that BTK plays in supporting suppressive myeloid cells, including myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM), while also discussing the anticancer effects of BTK inhibition and briefly describe the role of BTK signaling and BTK inhibition in microbial and viral infections.

Antibody Conjugation of Fluorescent Nanodiamonds for Targeted Innate Immune Cell Activation

BACKGROUND

fluorescent nanodiamonds (FND) are nontoxic, infinitely photostable nanoparticles that emit near-infrared fluorescence and have a modifiable surface allowing for the generation of protein-FND conjugates. FND-mediated immune cell targeting may serve as a strategy to visualize immune cells and promote immune cell activation.

METHODS

uncoated-FND (uFND) were fabricated, coated with glycidol (gFND), and conjugated with immunoglobulin G (IgG-gFND). In vitro studies were performed using a breast cancer/natural killer/monocyte co-culture system, and in vivo studies were performed using a breast cancer mouse model.

RESULTS

in vitro studies demonstrated the targeted immune cell uptake of IgG-gFND, resulting in significant immune cell activation and no compromise in immune cell viability. IgG-gFND remained at the tumor site following intratumoral injection compared to uFND which migrated to the liver and kidneys.

CONCLUSION

antibody-conjugated FND may serve as immune drug delivery vehicles with "track and trace capabilities" to promote directed antitumor activity and minimize systemic toxicities.

Observations on the use of Bruton's tyrosine kinase inhibitors in SAR-CoV-2 and cancer

Bruton's tyrosine kinase (BTK) inhibitors, drugs utilized in cancer, are being repurposed for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) (COVID-19). Recently, BTK inhibitors acalabrutinib and ibrutinib have been found to protect against pulmonary injury in a small group of patients infected with SARS-CoV-2. The high levels of pro-inflammatory cytokines found in the circulation of COVID-19 patients with severe lung disease suggest the involvement of the innate immune system in this process. Understanding the potential mechanism of action of BTK inhibition in SARS-CoV-2 is clearly of importance to determine how acalabrutinib, ibrutinib and possibly other BTK inhibitors may provide protection against lung injury.

Breast cancer survivors' satisfying marriages predict better psychological and physical health: A longitudinal comparison of satisfied, dissatisfied, and unmarried women

OBJECTIVE

Breast cancer survivors who experience psychological and physical symptoms after treatment have an increased risk for comorbid disease development, reduced quality of life, and premature mortality. Identifying factors that reduce or exacerbate their symptoms may enhance their long-term health and physical functioning. This study examined how survivors' marital status and marital satisfaction-key health determinants-impacted their psychological and physical health trajectories to understand when, and for whom, marriage offers health benefits.

METHODS

Breast cancer survivors (n = 209, stages 0-IIIC) completed a baseline visit before treatment and two follow-up visits 6 and 18 months after treatment ended. Women completed questionnaires assessing their marital status and satisfaction when applicable, as well as their psychological (depressive symptoms, stress) and physical (fatigue, pain) health at each visit.

RESULTS

Married women-both those in satisfying and dissatisfying marriages-experienced improvements in their depressive symptoms, stress, and fatigue from pretreatment to 6- and 18-month posttreatment. Unmarried (i.e., single, divorced/separated, or widowed) women's depressive symptoms, stress, fatigue, and pain did not change over time, instead remaining elevated 6 and 18 months after treatment ended. Women in satisfying marriages also had fewer psychological and physical symptoms after treatment than those who were unmarried or in dissatisfying marriages.

CONCLUSIONS

Although marriage was associated with improved psychological and physical health, the gains were most notable when survivors' marriages were satisfying. Thus, the quality of survivors' marriages, rather than the marriage itself, provided the most benefits to their psychological and physical health.

Soy-tomato enriched diet reduces inflammation and disease severity in a pre-clinical model of chronic pancreatitis

Chronic pancreatitis (CP) is a fibro-inflammatory syndrome in individuals who develop persistent pathological responses to parenchymal injury or stress. Novel therapeutic or dietary interventions that could lessen inflammation in this disease could significantly improve quality of life in patients with CP. Complex dietary foods like soy and tomatoes are composed of active metabolites with anti-inflammatory effects. Data from our group reports that bioactive agents in soy and tomatoes can reduce pro-inflammatory cytokines and suppressive immune populations. Additionally, our team has developed a novel soy-tomato juice currently being studied in healthy individuals with no toxicities, and good compliance and bioavailability. Thus, we hypothesize that administration of a soy-tomato enriched diet can reduce inflammation and severity of CP. C57BL/6 mice were injected intraperitoneally with 50 μg/kg caeurlein (7 hourly injections, twice weekly) for 6 weeks to induce CP. After 4 weeks of caerulein injections, mice were administered a control or a soy-tomato enriched diet for 2 weeks. Disease severity was measured via immunohistochemical analysis of pancreata measuring loss of acini, fibrosis, inflammation, and necrosis. Serum lipase and amylase levels were analyzed at the end of the study. Inflammatory factors in the serum and pancreas, and immune populations in the spleen of mice were analyzed by cytokine multiplex detection, qRT-PCR, and flow cytometry respectively. Infra-red (IR) sensing of mice was used to monitor spontaneous activity and distress of mice. Mice fed a soy-tomato enriched diet had a significantly reduced level of inflammation and severity of CP (p = 0.032) compared to mice administered a control diet with restored serum lipase and amylase levels (p < 0.05). Mice with CP fed a soy-tomato diet had a reduction in inflammatory factors (TNF-α, IL-1β, IL-5) and suppressive immune populations (myeloid-derived suppressor cells; MDSC) compared to control diet fed mice (p < 0.05). Infra-red sensing to monitor spontaneous activity of mice showed that soy-tomato enriched diet improved total activity and overall health of mice with CP (p = 0.055) and CP mice on a control diet were determined to spend more time at rest (p = 0.053). These pre-clinical results indicate that a soy-tomato enriched diet may be a novel treatment approach to reduce inflammation and pain in patients with CP.

Endotoxemia coupled with heightened inflammation predicts future depressive symptoms

OBJECTIVE

Cross-sectional data have linked gut barrier abnormalities and endotoxemia with depression, even among those without gastrointestinal symptoms. This study examined longitudinal associations between endotoxemia markers and depressive symptoms, as well as the role of inflammation in this relationship.

DESIGN

At three annual visits, 315 women (n=209 breast cancer survivors, n = 106 non-cancer patient controls, M=55 years old) completed the Center for Epidemiological Studies Depression questionnaire (CES-D) and provided blood samples to assess inflammatory markers - interleukin-6, tumor necrosis factor-alpha, and C-reactive protein - and endotoxemia markers - lipopolysaccharide-binding protein (LBP), soluble CD14 (sCD14), and their ratio.

RESULTS

Adjusting for key demographic variables, health behaviors, visit 1 depressive symptoms, and cancer status and treatment, women with higher visit 1 LBP and LBP/sCD14 had more depressive symptoms at the two subsequent annual visits. Illustrating the notable impact, a woman at the 75th percentile for LBP or LBP/sCD14 at visit 1 was 18 % more likely to report clinically significant depressive symptoms (CES-D ≥16) at follow-up than a woman in the lowest quartile. Cancer status and treatment type did not modulate this relationship. In contrast, visit 1 depressive symptoms did not predict endotoxemia at follow-up. A significant interaction between LBP/sCD14 and inflammatory burden suggested that visit 1 endotoxemia fueled depressive symptoms only in the context of elevated inflammation.

CONCLUSION

These results suggest that endotoxemia, combined with systemic inflammation, can drive depressive symptoms. These findings may implicate bacterial endotoxin translocation from the gut to the bloodstream in depression etiology. Interventions that reduce endotoxemia and inflammation may lessen the risk of depression.

Within-person changes in cancer-related distress predict breast cancer survivors' inflammation across treatment

BACKGROUND

Among breast cancer survivors, elevated inflammation has been linked to greater recurrence risk. Psychological processes, such as cancer-related distress, can pose threats to a survivor's longevity and wellbeing. Although distress can heighten inflammation, little is known about how fluctuations in distress during and after treatment impact a woman's own inflammation - the primary question of this study.

METHODS

Breast cancer survivors (n = 165, stages 0-III) completed a baseline visit before treatment and two follow-up visits 6 and 18 months after. At each visit, women completed the Impact of Events Scale to assess cancer-related distress, and a blood sample was collected to measure proinflammatory cytokines IL-6, TNF-α, IL-1β, and IL-8. This longitudinal study related fluctuations in survivor's own cancer-related distress (i.e., within-person effects), as well as average effects of cancer-related distress between survivors (i.e., between-person effects) to inflammatory changes across visits.

RESULTS

Women had elevated inflammation at visits where they expressed more cancer-related distress than what was typical. In contrast, the average cancer-related distress was not associated with inflammation.

CONCLUSION

Larger increases in a women's cancer-related distress was linked with higher inflammation across visits. Comparing a survivor's own cancer-related distress to her average levels may prove useful in identifying links between distress and inflammation.

Tissue microRNA expression profiling in hepatic and pulmonary metastatic melanoma

Malignant melanoma has a propensity for the development of hepatic and pulmonary metastases. MicroRNAs (miRs) are small, noncoding RNA molecules containing about 22 nucleotides that mediate protein expression and can contribute to cancer progression. We aim to identify clinically useful differences in miR expression in metastatic melanoma tissue. RNA was extracted from formalin-fixed, paraffin-embedded samples of hepatic and pulmonary metastatic melanoma, benign, nevi, and primary cutaneous melanoma. Assessment of miR expression was performed on purified RNA using the NanoString nCounter miRNA assay. miRs with greater than twofold change in expression when compared to other tumor sites (P value ≤ 0.05, modified t-test) were identified as dysregulated. Common gene targets were then identified among dysregulated miRs unique to each metastatic site. Melanoma metastatic to the liver had differential expression of 26 miRs compared to benign nevi and 16 miRs compared to primary melanoma (P < 0.048). Melanoma metastatic to the lung had differential expression of 19 miRs compared to benign nevi and 10 miRs compared to primary melanoma (P < 0.024). Compared to lung metastases, liver metastases had greater than twofold upregulation of four miRs, and 4.2-fold downregulation of miR-200c-3p (P < 0.0081). These findings indicate that sites of metastatic melanoma have unique miR profiles that may contribute to their development and localization. Further investigation of the utility of these miRs as diagnostic and prognostic biomarkers and their impact on the development of metastatic melanoma is warranted.

Impact of age-related T cell dynamics on the identification of biomarkers predictive of immunotherapy discontinuation: a prospective cohort study

Background

The impact of biologic aging on immune checkpoint inhibitor (ICI) toxicity and efficacy is underexplored in metastatic melanoma (MM). In peripheral blood T-lymphocytes (PBTLs), biologic aging is characterized by changes in T-cell composition and cellular senescence. Whether indicators of PBTL biologic aging vary in MM patients or can be used to predict premature ICI discontinuation (pID) is unknown.

Methods

We prospectively collected PBTLs from 117 cancer-free controls and 46 MM patients scheduled to begin pembrolizumab or nivolumab monotherapy. 74 mRNAs indicative of T-cell subsets, activation, co-stimuation/inhibition and cellular senescence were measured by Nanostring. Relationships between each mRNA and chronologic age were assessed in patients and controls. Candidate biomarkers were identified by calculating the hazard ratio (HR) for pID in patients divided into low and high groups based on log-transformed mRNA levels or the magnitude by which each mRNA measurement deviated from the control trend (Δage). Area under the curve (AUC) analyses explored the ability of each biomarker to discriminate between patients with and without pID at 6 months and 1 year.

Results

Fifteen mRNAs correlated with chronologic age in controls, including markers of T-cell subsets, differentiation, cytokine production and co-stimulation/inhibition. None of these mRNAs remained correlated with age in patients. Median follow-up was 94.8 (1.6-195.7) weeks and 35 of 46 patients discontinued therapy (23 progression, 7 toxicity, 5 comorbidity/patient preference). Elevated pre-therapy CD8A (HR 2.2[1.1-4.9]), CD45RB (HR 2.9[1.4-5.8]) and TNFRSF14 (HR 2.2[1.1-4.5]) levels predicted pID independent of Δage-correction. CD3ε, CD27 and FOXO1 predicted pID only after Δage-correction (HR 2.5[1.3-5.1]; 3.7[1.8-7.8]; 2.1[1.1-4.3]). AUC analysis identified Δage-CD3ε and -CD27 as candidate predictors of pID (AUC=0.73; 0.75).

Conclusions

Correlations between transcriptional markers of PBTL composition and chronologic age are disrupted in MM. Correcting for normal, age-related trends in biomarker expression unveils new biomarker candidates predictive of ICI outcomes.

Abstract 4481: Effect of immune checkpoint blockade on myeloid derived suppressor cell populations in patients with melanoma

Introduction: Myeloid derived suppressor cells (MDSC) are a subset of immature myeloid cells that inhibit innate anti-tumor immunity and promote an immunosuppressive tumor microenvironment. MDSC quantity has been correlated with tumor burden and survival in cancer patients. These cells have the potential to contribute to immune therapy resistance. The purpose of this study was to elucidate the ongoing changes to MDSC populations in patients with advanced melanoma as they receive immune checkpoint therapy.

Methods: Patients with melanoma (n=125) were consented to participate in an IRB-approved prospective clinical registry (OSU-13114), and provided blood samples. Samples were drawn at the time of initiation of immune checkpoint therapy (cycle 1), and prior to the beginning of cycles 2 and 3. Samples were then processed using Ficoll and analyzed for MDSC (CD33+/CD11b+/HLA-DRlo/−) and MDSC subsets, monocyte (CD14+, M-MDSC) and granulocytic (CD15+, PMN-MDSC) via flow cytometry. Patient demographics were compiled into a comprehensive database and correlated to the flow cytometry data. Statistical analysis was performed using unpaired and paired t-tests across and within patient cohorts.

Results: Total MDSC percentages increased following initiation of immune checkpoint blockade (10 to 25%, p&lt;0.0001). MDSC levels in patients who had complete or partial response began to taper (10% to 26% to 25%), whereas MDSC levels in those who had progressive disease on immunotherapy continued to increase (11% to 16% to 19%). PMN-MDSC significantly decreased after immunotherapy (19% to 10%, p=0.0423). Specifically, patients who received Pembrolizumab had a significant decrease in PMN-MDSC proportion (11% to 2%, p=0.04). A decrease in PMN-MDSC proportion was also noted with Nivolumab (21% to 16%, p=0.097). Patients who had received immune therapy prior to this trial had less PMN-MDSC at baseline (21% vs 12%, p=0.09), and significantly less PMN-MDSC following immune checkpoint blockade (14% vs 2%, p=0.009).

Conclusions: MDSC levels initially increase following immune checkpoint blockade, but stabilize in responders and continue to rise in non-responders. The proportion of PMN-MDSC decreases with immune checkpoint blockade, most significantly seen with pembrolizumab. Patients who have been previously treated with immune therapy have a more significant decrease in PMN-MDSC.

Citation Format: Steven Hao Sun, Brooke Benner, Himanshu Savardekar, Mallory DiVincenzo, David Abood, Andrew Stiff, Megan Duggan, Erin Nagle, John H. Howard, Manisha H. Shah, Kari Kendra, William E. Carson. Effect of immune checkpoint blockade on myeloid derived suppressor cell populations in patients with melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4481.

Abstract 5514: Analysis of immune checkpoint receptor expression by circulating T cells and tumor specimens in patients pre- and post-neoadjuvant chemotherapy for operable breast cancer

While combinations of immune checkpoint (ICP) inhibitors and neo-adjuvant chemotherapy (NAC) have begun to be tested in patients with breast cancer (BC), chemotherapeutic effects on ICP expression in circulating T cells are still unclear. This information could help design future clinical trials including the selection of the best ICP inhibitors to be incorporated into NAC and finding predictive/prognostic biomarkers. Peripheral blood samples and/or tumor specimens before and after NAC were obtained from twenty-four women with operable BC. Using flow cytometry, the expression of CTLA4, PD-1, Lag3, OX40, and Tim3 on circulating T lymphocytes before and at the end of NAC were measured. Differences in the percentage of CD4+ and CD8+ T cells expressing various checkpoint receptors pre- and post-NAC were determined by a paired t-test. This data showed decreased ICP expression after NAC by circulating CD4+ T cells, including significant decreases in CTLA4 (p&lt;0.001), Lag3 (p&lt;0.001), OX40 (p&lt;0.001), and PD-1 (p&lt;0.001). In comparison, circulating CD8+ T cells showed a significant increase in CTLA4 (p&lt;0.003), Lag3 (p=0.001), and OX40 (p&lt;0.001). In comparing breast cancer subtypes, it was found there were significantly lower amounts of circulating Lag3+ CD4+ T cells from triple-negative (lacking estrogen, progesterone, and HER2 receptor expression) breast cancer patients than those from breast cancer patients with tumors expressing at least one of these receptors. Furthermore, using multi-color immunohistochemistry (IHC), the expression of stromal tumor infiltrating lymphocytes (TILs), CD8+ T cells, and PD-1/PD-L1 within the tumor were determined before and after NAC. This analysis revealed fewer tumor specimens were considered to be PD-L1/PD-1 positive post-NAC as compared to pre-NAC biopsy samples using a cutoff of 1% or greater expression. Overall, this work reveals that NAC has opposing effects on ICP expression by CD4+ and CD8+ T cells as well as provides a starting point to study the biological significance of these changes in BC patients.Trial registration: NCT04022616

Citation Format: Dionisia M. Quiroga, Andrew Stiff, Christopher McQuinn, Zaibo Li, Hiroaki Nitta, Himanshu Savardekar, Brooke Benner, Bhuvaneswari Ramaswamy, Maryam Lustberg, Rachel Layman, Erin Macrae, Mahmoud Kassem, Nicole Williams, Sagar Sardesai, Jeffrey VanDeusen, Daniel Stover, Mathew Cherian, Thomas Mace, Lianbo Yu, Megan Duggan, William E. Carson, Robert Wesolowski. Analysis of immune checkpoint receptor expression by circulating T cells and tumor specimens in patients pre- and post-neoadjuvant chemotherapy for operable breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5514.

Abstract 3696: Determination of the expression patterns and functional implications of microRNAs in ulcerated cutaneous melanoma

Introduction: Ulcerated primary cutaneous melanomas have a poor prognosis and the underlying biology driving this aggressive behavior is largely unexplored. The presence of tumor ulceration at the time of diagnosis of cutaneous melanoma is among the top prognostic indicators for clinical outcome, associated with reduced disease free and overall survival. Thus, ulceration is employed as a clinical and histopathologic criterion for classification of melanomas into a higher tumor stage. microRNAs are small, non-coding RNAs that frequently exhibit dysregulated expression in cancer and can impact tumor biologic behavior via mediation of oncogene or tumor suppressor gene expression. While patterns of microRNA expression in melanoma have been identified that demonstrate their utility as predictive biomarkers of disease progression and metastasis, the microRNA expression profile of cutaneous melanomas with evidence of ulceration has not yet been assessed.

Methods: We determined the microRNA expression profile in RNA isolated from formalin-fixed, paraffin-embedded samples of human ulcerated cutaneous melanoma relative non-ulcerated tumors (n=7 each) using the NanoString human miRNA assay platform. The impact of hsa-miR-1469, a novel microRNA demonstrating downregulated expression in ulcerated melanomas in this study, was examined using in vitro functional assays via transfection of melanoma cell lines A375, CHL-1, and MEL39 with a miR-1469 mimic construct.

Results: The resultant microRNA expression data demonstrated at least 2-fold change in expression of 9 microRNAs between ulcerated and non-ulcerated melanoma tumors (p &lt;0.01). Among the top differentially expressed miRs were hsa-miR-4286, hsa-miR-4488, and hsa-miR-1469, each with greater than 3.9-fold decreases in expression in the setting of ulceration relative to non-ulcerated tumors (p &lt;0.0029). Restoration of miR-1469 expression resulted in significant reduction in the migration of melanoma tumor cells relative to untransfected and miR-scramble transfected controls in the CHL-1 model (0.41-fold decrease, p = 0.046 and 0.36-fold decrease, p = 0.013, respectively), with similar patterns observed in A375 and MEL39 cell lines. Transfection with a miR-1469 mimic also increased apoptosis in response to fludarabine (2.32-fold increase, p=0.044).

Conclusions: The microRNA expression profile generated from this study highlights a subset of microRNAs that may impact disease progression in patients with ulcerated tumors via mediation of tumor cell functions, and provides further molecular characterization of a poorly understood clinical and histopathologic phenotype. Additional studies examining the expression and function of these microRNAs are necessary to determine their utility as predictive biomarkers and role in tumor progression in the setting of ulcerated cutaneous melanoma.

Citation Format: Mallory J. DiVincenzo, Casey Ren, Lorena Suarez-Kelly, Maribelle Moufawad, Zoe Barricklow, Paolo Fadda, Lianbo Yu, John H. Howard, Alejandro A. Gru, William E. Carson. Determination of the expression patterns and functional implications of microRNAs in ulcerated cutaneous melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3696.

Abstract 3414: Brd4 inhibition enhances checkpoint therapy by inducing MDSC apoptosis

Myeloid derived suppressor cells (MDSCs) antagonize antitumor immune responses, and limit the efficacy of immune based therapies for cancer. As a result, MDSCs have garnered attention as therapeutic targets. Unfortunately, there has been limited success in translating agents targeting MDSCs to the clinic. Brd4 is an epigenetic reader and is itself a therapeutic target in oncology due to its ability to regulate the expression of oncogenes such as Myc. In addition, Brd4 is known to regulate inflammatory cytokine production and innate immune responses including myeloid cell function. As a result, it was hypothesized that inhibition of Brd4 would impact MDSC function or expansion. In multiple tumor models (EMT6, 4T1, LLC, and C26) Brd4 inhibitors, both experimental (JQ1) and those in clinical development (PLX51107 and PLX2853) significantly reduced the abundance of total, PMN, and M-MDSC subsets within the tumor and spleen as measured by flow cytometry and IHC (p&lt; 0.05). Furthermore, Nanostring gene expression analysis of EMT6 tumors identified a significant reduction in the abundance signature of neutrophils and macrophages with PLX51107 further confirming a reduction of myeloid cells in the presence of a Brd4 inhibitor (p&lt; 0.01). The Nanostring analysis also showed a significant reduction of IL6 mRNA in PLX51107 treated tumors, and this was confirmed at the protein level by ELISA in the serum of EMT6 and 4T1 tumor bearing mice (p&lt; 0.05). However, exogenous IL6 could not rescue MDSC levels in vivo or in vitro suggesting Brd4 inhibition might be directly affecting MDSCs. This was confirmed by showing that PLX51107 significantly inhibited the expansion of MDSCs from mouse bone marrow cells or healthy donor PBMCs cultured in IL6 and GMCSF as measured by flow cytometry (p&lt;0.05). Furthermore, mouse and FACS sorted MDSCs from patients with melanoma or bladder cancer were found to undergo apoptosis when treated with PLX51107 as measured by flow cytometry (annexin and caspase3, p&lt; 0.05), IF, and western blot. In addition, a pancaspase inhibitor rescued both mouse and patient derived MDSCs from apoptosis in the presence of PLX51107. Further investigation with specific caspase inhibitors showed this effect relied mostly on activation of the intrinsic apoptosis pathway and caspase9. The importance of Brd4 to MDSC survival was further confirmed using a LysMCre Brd4 floxed mouse model. Finally, depletion of MDSCs in vivo with PLX51107 significantly enhanced the efficacy of anti-PDL1 therapy as compared to either agent alone (p&lt; 0.05 in EMT6, 4T1, and LLC tumor models). These results identify Brd4 and the TXNIP/ASK1 apoptosis pathway as novel regulators of MDSC survival, and provide evidence to further investigate Brd4 inhibitors in combination with immune based therapies for solid tumors.

Citation Format: Andrew Stiff, Himanshu Savardekar, Robert Wesolowski, Megan Duggan, Luke Scarberry, Brooke Benner, Darren Wethington, Gabby Lapurga, Steven Sun, Jack Hedberg, Logan Good, William E. Carson. Brd4 inhibition enhances checkpoint therapy by inducing MDSC apoptosis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3414.

CD200 promotes immunosuppression in the pancreatic tumor microenvironment

BACKGROUND

A significant challenge to overcome in pancreatic ductal adenocarcinoma (PDAC) is the profound systemic immunosuppression that renders this disease non-responsive to immunotherapy. Our supporting data provide evidence that CD200, a regulator of myeloid cell activity, is expressed in the PDAC microenvironment. Additionally, myeloid-derived suppressor cells (MDSC) isolated from patients with PDAC express elevated levels of the CD200 receptor (CD200R). Thus, we hypothesize that CD200 expression in the PDAC microenvironment limits responses to immunotherapy by promoting expansion and activity of MDSC.

METHODS

Immunofluorescent staining was used to determine expression of CD200 in murine and human PDAC tissue. Flow cytometry was utilized to test for CD200R expression by immune populations in patient blood samples. In vivo antibody blocking of CD200 was conducted in subcutaneous MT-5 tumor-bearing mice and in a genetically engineered PDAC model (KPC-Brca2 mice). Peripheral blood mononuclear cells (PBMC) from patients with PDAC were analyzed by single-cell RNA sequencing. MDSC expansion assays were completed using healthy donor PBMC stimulated with IL-6/GM-CSF in the presence of recombinant CD200 protein.

RESULTS

We found expression of CD200 by human pancreatic cell lines (BxPC3, MiaPaca2, and PANC-1) as well as on primary epithelial pancreatic tumor cells and smooth muscle actin+ stromal cells. CD200R expression was found to be elevated on CD11b+CD33+HLA-DRlo/- MDSC immune populations from patients with PDAC (p=0.0106). Higher expression levels of CD200R were observed in CD15+ MDSC compared with CD14+ MDSC (p<0.001). In vivo studies demonstrated that CD200 antibody blockade limited tumor progression in MT-5 subcutaneous tumor-bearing and in KPC-Brca2 mice (p<0.05). The percentage of intratumoral MDSC was significantly reduced in anti-CD200 treated mice compared with controls. Additionally, in vivo blockade of CD200 can also significantly enhance the efficacy of PD-1 checkpoint antibodies compared with single antibody therapies (p<0.05). Single-cell RNA sequencing of PBMC from patients revealed that CD200R+ MDSC expressed genes involved in cytokine signaling and MDSC expansion. Further, in vitro cytokine-driven expansion and the suppressive activity of human MDSC was enhanced when cocultured with recombinant CD200 protein.

CONCLUSIONS

These results indicate that CD200 expression in the PDAC microenvironment may regulate MDSC expansion and that targeting CD200 may enhance activity of checkpoint immunotherapy.

Reciprocal Signaling between Myeloid Derived Suppressor and Tumor Cells Enhances Cellular Motility and is Mediated by Structural Cues in the Microenvironment

Myeloid derived suppressor cells (MDSCs) have gained significant attention for their immunosuppressive role in cancer and their ability to contribute to tumor progression and metastasis. Understanding the role of MDSCs in driving cancer cell migration, a process fundamental to metastasis, is essential to fully comprehend and target MDSC-tumor cell interactions. This study employs microfabricated platforms, which simulate the structural cues present in the tumor microenvironment (TME) to elucidate the effects of MDSCs on the migratory phenotype of cancer cells at the single cell level. The results indicate that the presence of MDSCs enhances the motility of cancer-epithelial cells when directional cues (either topographical or spatial) are present. This behavior appears to be independent of cell-cell contact and driven by soluble byproducts from heterotypic interactions between MDSCs and cancer cells. Moreover, MDSC cell-motility is also impacted by the presence of cancer cells and the cancer cell secretome in the presence of directional cues. Epithelial dedifferentiation is the likely mechanism for changes in cancer cell motility in response to MDSCs. These results highlight the biochemical and biostructural conditions under which MDSCs can support cancer cell migration, and could therefore provide new avenues of research and therapy aimed at stemming cancer progression.

Exploratory analysis of immune checkpoint receptor expression by circulating T cells and tumor specimens in patients receiving neo-adjuvant chemotherapy for operable breast cancer

BACKGROUND

While combinations of immune checkpoint (ICP) inhibitors and neo-adjuvant chemotherapy (NAC) have begun testing in patients with breast cancer (BC), the effects of chemotherapy on ICP expression in circulating T cells and within the tumor microenvironment are still unclear. This information could help with the design of future clinical trials by permitting the selection of the most appropriate ICP inhibitors for incorporation into NAC.

METHODS

Peripheral blood samples and/or tumor specimens before and after NAC were obtained from 24 women with operable BC. The expression of CTLA4, PD-1, Lag3, OX40, and Tim3 on circulating T lymphocytes before and at the end of NAC were measured using flow cytometry. Furthermore, using multi-color immunohistochemistry (IHC), the expression of immune checkpoint molecules by stromal tumor-infiltrating lymphocytes (TILs), CD8+ T cells, and tumor cells was determined before and after NAC. Differences in the percentage of CD4+ and CD8+ T cells expressing various checkpoint receptors were determined by a paired Student's t-test.

RESULTS

This analysis showed decreased ICP expression by circulating CD4+ T cells after NAC, including significant decreases in CTLA4, Lag3, OX40, and PD-1 (all p values < 0.01). In comparison, circulating CD8+ T cells showed a significant increase in CTLA4, Lag3, and OX40 (all p values < 0.01). Within tumor samples, TILs, CD8+ T cells, and PD-L1/PD-1 expression decreased after NAC. Additionally, fewer tumor specimens were considered to be PD-L1/PD-1 positive post-NAC as compared to pre-NAC biopsy samples using a cutoff of 1% expression.

CONCLUSIONS

This work revealed that NAC treatment can substantially downregulate CD4+ and upregulate CD8+ T cell ICP expression as well as deplete the amount of TILs and CD8+ T cells found in breast tumor samples. These findings provide a starting point to study the biological significance of these changes in BC patients.

TRIAL REGISTRATION

NCT04022616.

Pexidartinib, a Novel Small Molecule CSF-1R Inhibitor in Use for Tenosynovial Giant Cell Tumor: A Systematic Review of Pre-Clinical and Clinical Development

Tenosynovial giant cell tumor (TGCT) is a rare benign tumor that involves the synovium, bursa, and tendon sheath, resulting in reduced mobility of the affected joint or limb. The current standard of care for TGCT is surgical resection. However, some patients have tumor recurrence, present with unresectable tumors, or have tumors that are in locations where resection could result in amputations or significant debility. Therefore, the development of systemic agents with activity against TGCT to expand treatment options is a highly unmet medical need. Pathologically, TGCT is characterized by the overexpression of colony-stimulating factor 1 (CSF-1), which leads to the recruitment of colony-stimulating factor-1 receptor (CSF-1R) expressing macrophages that make up the primary cell type within these giant cell tumors. The binding of CSF-1 and CSF-1R controls cell survival and proliferation of monocytes and the switch from a monocytic to macrophage phenotype contributing to the growth and inflammation within these tumors. Therefore, molecules that target CSF-1/CSF-1R have emerged as potential systemic agents for the treatment of TGCT. Given the role of macrophages in regulating tumorigenesis, CSF1/CSF1R-targeting agents have emerged as attractive therapeutic targets for solid tumors. Pexidartinib is an orally bioavailable and potent inhibitor of CSF-1R which is one of the most clinically used agents. In this review, we discuss the biology of TGCT and review the pre-clinical and clinical development of pexidartinib which ultimately led to the FDA approval of this agent for the treatment of TGCT as well as ongoing clinical studies utilizing pexidartinib in the setting of cancer.

Evidence for interaction of the NLRP3 inflammasome and Bruton's tyrosine kinase in tumor-associated macrophages: implications for myeloid cell production of interleukin-1beta

An inflammatory microenvironment has been shown to play an important role in the growth and metastasis of tumors. The NLRP3 inflammasome is a multi-protein complex of the innate immune system that is responsible for the production of the potent inflammatory cytokine IL-1β. Tumor- associated macrophages (TAM) are an expanded population of immune cells found in the tumor microenvironment that can promote the initiation and metastasis of tumor cells. Their presence has been correlated with disease burden, highlighting the therapeutic potential of targeting this population. However, to date clinically relevant pharmacologic strategies to target TAM remain elusive. Here, we show that in vitro generated TAM harbor NLRP3 inflammasome components and produce IL-1β. Ibrutinib, an irreversible inhibitor of Bruton's tyrosine kinase (BTK), is in clinical use for the treatment of B- cell malignancies. We report that BTK is expressed by human in vitro generated TAM and murine macrophages and that it physically associates with the NLRP3 inflammasome. Furthermore, ibrutinib is able to inhibit BTK phosphorylation in TAM generated in vitro. Treatment of TAM with ibrutinib significantly impaired the ability of these cells to produce IL-1β. The present study provides evidence that BTK physically associates with the NLRP3 inflammasome and that inhibition of BTK with ibrutinib can impair the production of IL-1β by in vitro generated TAM. Thus, ibrutinib could potentially be of clinical use in abrogating inflammation-associated cancer progression and the immune-suppressive effects of myeloid cells within the tumor microenvironment.

Anti-leukemic effects of all-trans retinoic acid in combination with Daratumumab in acute myeloid leukemia

Acute myeloid leukemia (AML) remains a significant health problem, with poor outcomes despite chemotherapy and bone marrow transplants. Although one form of AML, acute promyelocytic leukemia (APL), is successfully treated with all-trans retinoic acid (ATRA), this drug is seemingly ineffective against all other forms of AML. Here, we show that ATRA up-regulates CD38 expression on AML blasts to sufficient levels that promote antibody-mediated fratricide following the addition of anti-CD38 daratumumab (DARA). The combination of ATRA plus DARA induced Fc-dependent conjugate formation and cytotoxicity among AML blasts in vitro. Combination treatment also led to reduction in tumor volume and resulted in increased overall survival in murine engraftment models of AML. These results suggest that, although ATRA does not induce differentiation of non-APL, it may be effective as a therapy in conjunction with DARA.

An IL-15-based superagonist ALT-803 enhances the NK cell response to cetuximab-treated squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) is the sixth most common cancer worldwide and epidermal growth factor receptor (EGFR) is overexpressed in greater than 90% of patient tumors. Cetuximab is a monoclonal antibody that binds to EGFR and can activate immune cells, such as natural killer (NK) cells, that express receptors for the Fc (constant region) of immunoglobulin G. IL-15 (interleukin-15) is a critical factor for the development, proliferation and activation of effector NK cells. A novel IL-15 compound known as ALT-803 that consists of genetically modified IL-15 plus the IL-15 receptor alpha protein (IL15Rα) fused to the Fc portion of IgG1 has recently been developed. We hypothesized that treatment with ALT-803 would increase NK cell-mediated cytotoxicity of cetuximab-coated head and neck squamous cells. CD56+ NK cells from normal healthy donors were treated overnight with ALT-803 and tested for their ability to lyse cetuximab-coated tumor cells. Cytotoxicity was greater following NK cell ALT-803 activation, as compared to controls. ALT-803-treated NK cells secreted significantly higher levels of IFN-γ than control conditions. Additionally, NK cells showed increased levels of phospho-ERK and phospho-STAT5 when co-cultured with cetuximab-coated tumors and ALT-803. Administration of both cetuximab and ALT-803 to mice harboring Cal27 SCCHN tumors resulted in significantly decreased tumor volume when compared to controls and compared to single-agent treatment alone. Overall, the present data suggest that cetuximab treatment in combination with ALT-803 in patients with EGFR-positive SCCHN may result in significant NK cell activation and have important anti-tumor activity.

Abstract CT169: Pilot study testing the effects of BTK inhibitor ibrutinib and nivolumab on levels and function of myeloid-derived suppressor cells and other immune subsets in patients with metastatic solid tumors (NCT03525925)

Background: Myeloid-derived suppressor cells (MDSC) are a naturally occurring population of immature myeloid cells with immune suppressive function that curtail inflammatory processes. In cancer, these cells abnormally expand and migrate to tumor/lymphoid regions where they negatively impact antigen specific and innate immune effector cells. Circulating MDSC levels have also been associated with the higher tumor burden and decreased survival of patients with solid tumors. Preclinical studies performed by our group demonstrated that ibrutinib (PCI-32765), an irreversible inhibitor of Bruton’s tyrosine kinase, is capable of inhibiting MDSC generation and their immunosuppressive function (A. Stiff, CA Res, 2016). We also found that the combination of ibrutinib and a PD-L1 inhibitor worked synergistically in a mouse model of mammary carcinoma. Based on these results, targeting MDSC with ibrutinib has the potential to enhance the efficacy of immune checkpoint inhibitors such as nivolumab in patients with advanced solid tumors.

Materials and Methods: This pilot study will assess the effect of single agent ibrutinib and ibrutinib in combination with nivolumab on levels and function of circulating myeloid-derived suppressor cells in 15 patients with advanced solid tumors. Eligible patients are required to have metastatic malignancy and be eligible for treatment with nivolumab as determined by the treating physician. Study subjects will be treated with ibrutinib at 420 mg given orally once daily. Nivolumab will be given at a standard dose of 240 mg IV over 30 minutes on days 1 and 15 on 28-day cycles. Ibrutinib dosing will be started 7 (+/-2) days prior to cycle 1 of nivolumab therapy and will be given until cycle 1, day 8 of nivolumab or total of 15 days (whichever comes first). Peripheral blood will be collected just prior to initiation of ibrutinib (at day -7), prior to day 1 of cycle 1, prior to day 8 of cycle 1, prior to day 1 of cycle 2 and at the time of disease progression. The primary objective is to evaluate the effect of the ibrutinib therapy on circulating levels of myeloid-derived suppressor cells (MDSC). The safety of the study combination, effect of ibrutinib/nivolumab on immune cell subsets and the length of progression-free survival will also be assessed.

Conclusion: The study opened to accrual on August 10, 2018 and is currently enrolling the target 15 patients. To date 9 patients are on study.

Citation Format: Brooke Benner, Megan Duggan, Andrew Stiff, Bhavana Konda, Robert D. Rupert, Paul Monk, Claire Verschraegen, Hiral Shah, Anne Noonan, William E. Carson, Robert Wesolowski. Pilot study testing the effects of BTK inhibitor ibrutinib and nivolumab on levels and function of myeloid-derived suppressor cells and other immune subsets in patients with metastatic solid tumors (NCT03525925) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT169.

A Phase I/II Trial of Cetuximab in Combination with Interleukin-12 Administered to Patients with Unresectable Primary or Recurrent Head and Neck Squamous Cell Carcinoma

PURPOSE

mAbs including cetuximab can induce antibody-dependent cellular cytotoxicity (ADCC) and cytokine production mediated via innate immune cells with the ability to recognize mAb-coated tumors. Preclinical modeling has shown that costimulation of natural killer (NK) cells via the Fc receptor and the IL12 receptor promotes NK-cell-mediated ADCC and production of cytokines.

PATIENTS AND METHODS

This phase I/II trial evaluated the combination of cetuximab with IL12 for the treatment of EGFR-expressing head and neck cancer. Treatment consisted of cetuximab 500 mg/m² i.v. every 2 weeks with either 0.2 mcg/kg or 0.3 mcg/kg IL12 s.c. on days 2 and 5 of the 2-week cycle, beginning with cycle 2. Correlative studies from blood draws obtained prior to treatment and during therapy included measurement of ADCC, serum cytokine, and chemokine analysis, determination of NK cell FcγRIIIa polymorphisms, and an analysis of myeloid-derived suppressor cell (MDSC) frequency in peripheral blood.

RESULTS

The combination of cetuximab and IL12 was well tolerated. No clinical responses were observed, however, 48% of patients exhibited prolonged progression-free survival (PFS; average of 6.5 months). Compared with patients that did not exhibit clinical benefit, patients with PFS >100 days exhibited increased ADCC as therapy continued compared with baseline, greater production of IFNγ, IP-10, and TNFα at the beginning of cycle 8 compared with baseline values and had a predominance of monocytic MDSCs versus granulocytic MDSCs prior to therapy.

CONCLUSIONS

Further investigation of IL12 as an immunomodulatory agent in combination with cetuximab in head and neck squamous cell carcinoma is warranted.

Generation of monocyte-derived tumor-associated macrophages using tumor-conditioned media provides a novel method to study tumor-associated macrophages in vitro

Background

Tumor-associated macrophages (TAM) are expanded and exhibit tumor-promoting properties within the tumor microenvironment. Current methods to study TAM have not been replicated across cancer types and often do not include exogenous growth factors from the tumor, a key factor in TAM differentiation in vivo.

Methods

In this study, an in vitro method to generate monocyte- derived TAM using tumor- conditioned media (TCM) and a cytokine cocktail containing IL-4, IL-10, and M-CSF was utilized to study the phenotype, morphology, and function of TAM across multiple cancer types. TCM was generated from two breast cancer cell lines and an Epstein-Barr virus-positive lymphoma cell line. The properties of in vitro generated TAM were compared to in vitro generated M1 and M2- like macrophages and TAM isolated from patients with cancer.

Results

TAM generated in this fashion displayed an increase in CD163/CD206 co-expression compared to M2- like macrophages (87 and 36%, respectively). TAM generated in vitro exhibited increased transcript levels of the functional markers IL-6, IL-10, CCL2, c-Myc, iNOS, and arginase compared to in vitro generated M2-like macrophages. Functionally, in vitro generated TAM inhibited the proliferation of T cells (47% decrease from M1-like macrophages) and the production of IFN-γ by natural killer cells was inhibited (44%) when co-cultured with TAM. Furthermore, in vitro generated TAM secreted soluble factors that promote the growth and survival of tumor cells.

Conclusions

Limited access to patient TAM highlights the need for methods to generate TAM in vitro. Our data confirm that monocyte-derived TAM can be generated reliably using TCM plus the cytokine cocktail of IL-4, IL-10, and M-CSF. Given the ability of TAM to inhibit immune cell function, continued study of methods to deplete or deactivate TAM in the setting of cancer are warranted.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0622-0) contains supplementary material, which is available to authorized users.

Cutaneous Melanoma, Version 2.2019, NCCN Clinical Practice Guidelines in Oncology

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Cutaneous melanoma have been significantly revised over the past few years in response to emerging data on immune checkpoint inhibitor therapies and BRAF-targeted therapy. This article summarizes the data and rationale supporting extensive changes to the recommendations for systemic therapy as adjuvant treatment of resected disease and as treatment of unresectable or distant metastatic disease.