MCL1 inhibition targets Myeloid Derived Suppressors Cells, promotes antitumor immunity and enhances the efficacy of immune checkpoint blockade

Immune checkpoint inhibitors (ICIs) are now the first-line treatment for patients with advanced melanoma. Despite promising clinical results, many patients fail to respond to these therapies. BH3 mimetics, a novel class of small molecule inhibitors that bind and inhibit anti-apoptotic members of the BCL2 family proteins such as BCL2 or MCL1, have been very successful in treating hematologic malignancies. However, there are limited studies on the immunomodulatory role of the BH3 mimetics. Several factors contribute to ICI resistance including myeloid-derived suppressor cells (MDSCs) that exert immunosuppressive effects through direct and indirect inhibition of antitumor immunity. Thus, targeting MDSCs to enhance antitumor immunity has the potential to enhance the efficacy of ICIs. In this study, we show that the MCL1 inhibitor S64315 reduces melanoma tumor growth in an immune cell-dependent manner in mice. Specifically, S64315 enhances antitumor immunity by reducing MDSC frequency and by promoting the activity of CD8+T cells. Additionally, human MDSCs are 10 times more sensitive to S64315 than cutaneous melanoma lines. Further, we found that a higher expression of MCL1 is associated with poor survival for patients treated with anti-PD-1. Finally, combining S64315 and anti-PD-1 significantly slowed tumor growth compared to either agent alone. Together, this proof-of-concept study demonstrates the potential of combining an MCL1 inhibitor with anti-PD-1 in the treatment of melanoma. It justifies the further development of next generation MCL1 inhibitors to improve efficacy of ICIs in treating malignant melanoma.

Clinical presentation of cardiac symptoms following treatment with tumor-infiltrating lymphocytes: diagnostic challenges and lessons learned

BACKGROUND

Treatment with tumor-infiltrating lymphocytes (TILs) is rapidly evolving for patients with solid tumors. Following metastasectomy, TILs (autologous, intratumoral CD4+ and CD8+ T cells with the potential to recognize tumor-associated antigens) are isolated and non-specifically expanded ex vivo in the presence of interleukin-2 (IL-2). Subsequently, the TILs are adoptively transferred to the patients after a preconditioning non-myeloablative, lymphodepleting chemotherapy regimen, followed by administration of high-dose (HD) IL-2. Here, we provide an overview of known cardiac risks associated with TIL treatment and report on seven patients presenting with cardiac symptoms, all with different clinical course and diagnostic findings during treatment with lymphodepleting chemotherapy, TIL, and HD IL-2, and propose a set of clinical recommendations for diagnosis and management of these symptoms.

PATIENTS AND METHODS

This single-center, retrospective study included selected patients who experienced TIL treatment-related cardiac symptoms at the Netherlands Cancer Institute. In addition, 12 patients were included who received TIL in the clinical trial setting without experiencing cardiac symptoms, from whom complete cardiac biomarker follow-up during treatment was available [creatine kinase (CK), CK-myocardial band, troponin T and N-terminal pro-B-type natriuretic peptide].

RESULTS

Within our TIL patient population, seven illustrative cases were chosen from the patients who developed symptoms suspected of severe cardiotoxicity: myocarditis, myocardial infarction, peri-myocarditis, atrial fibrillation, acute dyspnea, and two cases of heart failure. An overview of their clinical course, diagnostics carried out, and management of the symptoms is provided.

CONCLUSIONS

In the absence of evidence-based guidelines for the treatment of TIL therapy-associated cardiotoxicity, we provided an overview of literature, case descriptions, and recommendations for diagnosis and management to help physicians in daily practice, as the number of patients qualifying for TIL treatment is rapidly increasing.

Dysfunctional states of unconventional T-cell subsets in cancer

Unconventional T cells represent a promising therapeutic agent to overcome the current limitations of immunotherapies due to their universal T-cell receptors, ability to respond directly to cytokine stimulation, and capacity to recruit and modulate conventional immune cells in the tumor microenvironment. Like conventional T cells, unconventional T cells can enter a dysfunctional state, and the functional differences associated with this state may provide insight into the discrepancies observed in their role in antitumor immunity in various cancers. The exhaustive signature of unconventional T cells differs from conventional αβ T cells, and understanding the differences in the mechanisms underlying exhaustive differentiation in these cell types may aid in the discovery of new treatments to improve sustained antitumor responses. Ongoing clinical trials investigating therapies that leverage unconventional T-cell populations have shown success in treating hematologic malignancies and reducing the immunosuppressive tumor environment. However, several hurdles remain to extend these promising results into solid tumors. Here we discuss the current knowledge on unconventional T-cell function/dysfunction and consider how the incorporation of therapies that modulate unconventional T-cell exhaustion may aid in overcoming the current limitations of immunotherapy. Additionally, we discuss how components of the tumor microenvironment alter the functions of unconventional T cells and how these changes can affect tumor infiltration by lymphocytes and alter conventional T-cell responses.

Polymorphic KIR3DL3 expression modulates tissue-resident and innate-like T cells

Most human killer cell immunoglobulin-like receptors (KIR) are expressed by natural killer (NK) cells and recognize HLA class I molecules as ligands. KIR3DL3 is a conserved but polymorphic inhibitory KIR recognizing a B7 family ligand, HHLA2, and is implicated for immune checkpoint targeting. The expression profile and biological function of KIR3DL3 have been somewhat elusive, so we searched extensively for KIR3DL3 transcripts, revealing highly enriched expression in γδ and CD8+ T cells rather than NK cells. These KIR3DL3-expressing cells are rare in the blood and thymus but more common in the lungs and digestive tract. High-resolution flow cytometry and single-cell transcriptomics showed that peripheral blood KIR3DL3+ T cells have an activated transitional memory phenotype and are hypofunctional. The T cell receptor (TCR) usage is biased toward genes from early rearranged TCR-α variable segments or Vδ1 chains. In addition, we show that TCR-mediated stimulation can be inhibited through KIR3DL3 ligation. Whereas we detected no impact of KIR3DL3 polymorphism on ligand binding, variants in the proximal promoter and at residue 86 can reduce expression. Together, we demonstrate that KIR3DL3 is up-regulated alongside unconventional T cell stimulation and that individuals may vary in their ability to express KIR3DL3. These results have implications for the personalized targeting of KIR3DL3/HHLA2 checkpoint inhibition.

Lysophosphatidic acid modulates CD8 T cell immunosurveillance and metabolism to impair anti-tumor immunity

Lysophosphatidic acid (LPA) is a bioactive lipid which increases in concentration locally and systemically across different cancer types. Yet, the exact mechanism(s) of how LPA affects CD8 T cell immunosurveillance during tumor progression remain unknown. We show LPA receptor (LPAR) signaling by CD8 T cells promotes tolerogenic states via metabolic reprogramming and potentiating exhaustive-like differentiation to modulate anti-tumor immunity. We found LPA levels predict response to immunotherapy and Lpar5 signaling promotes cellular states associated with exhausted phenotypes on CD8 T cells. Importantly, we show that Lpar5 regulates CD8 T cell respiration, proton leak, and reactive oxygen species. Together, our findings reveal that LPA serves as a lipid-regulated immune checkpoint by modulating metabolic efficiency through LPAR5 signaling on CD8 T cells. Our study offers key insights into the mechanisms governing adaptive anti-tumor immunity and demonstrates LPA could be exploited as a T cell directed therapy to improve dysfunctional anti-tumor immunity.

Targeting MDSC Differentiation Using ATRA: A Phase I/II Clinical Trial Combining Pembrolizumab and All-Trans Retinoic Acid for Metastatic Melanoma

PURPOSE

A phase Ib/II clinical trial was conducted to evaluate the safety and efficacy of the combination of all-trans retinoic acid (ATRA) with pembrolizumab in patients with stage IV melanoma.

PATIENTS AND METHODS

Anti-PD-1 naïve patients with stage IV melanoma were treated with pembrolizumab plus supplemental ATRA for three days surrounding each of the first four pembrolizumab infusions. The primary objective was to establish the MTD and recommended phase II dose (RP2D) of the combination. The secondary objectives were to describe the safety and toxicity of the combined treatment and to assess antitumor activity in terms of (i) the reduction in circulating myeloid-derived suppressor cell (MDSC) frequency and (ii) progression-free survival (PFS).

RESULTS

Twenty-four patients were enrolled, 46% diagnosed with M1a and 29% with M1c stage disease at enrollment. All patients had an ECOG status ≤1, and 75% had received no prior therapies. The combination was well tolerated, with the most common ATRA-related adverse events being headache, fatigue, and nausea. The RP2D was established at 150 mg/m2 ATRA + 200 mg Q3W pembrolizumab. Median PFS was 20.3 months, and the overall response rate was 71%, with 50% of patients experiencing a complete response, and the 1-year overall survival was 80%. The combination effectively lowered the frequency of circulating MDSCs.

CONCLUSIONS

With a favorable tolerability and high response rate, this combination is a promising frontline treatment strategy for advanced melanoma. Targeting MDSCs remains an attractive mechanism to enhance the efficacy of immunotherapies, and this combination merits further investigation. See related commentary by Olson and Luke, p. 1167.

Expression Differences in BCL2 Family Members between Uveal and Cutaneous Melanomas Account for Varying Sensitivity to BH3 Mimetics

Uveal melanoma (UM) is a subtype of melanoma. Although they share a melanocytic origin with cutaneous melanoma (CM), patients with UM have few treatment options. BCL2 homologous 3 mimetics are small-molecule drugs that mimic proapoptotic BCL2 family members. We compared BCL2 family member expression between UM and CM using immunoblot and The Cancer Genome Atlas transcriptomic analysis. UM has a unique signature of low BFL1 and high PUMA proteins compared with CM and 30 other cancer types, making them an attractive candidate for BCL2 homologous 3 protein mimetics. We tested the efficacy of a BCL2 inhibitor and MCL1 inhibitor (MCL1i) in UM, with viability assays, live-cell imaging, sphere assays, and mouse xenograft models. UM had a higher sensitivity to MCL1i than CM. Overexpression of BFL1 or knockdown of PUMA made the UM more resistant to MCL1i. In contrast, MAPK/extracellular signal‒regulated kinase inhibitor treatment in CM made them more sensitive to MCL1i. However, MCL1i-alone treatment was not very effective to reduce the UM initiating cells; to overcome this, we employed a combination of MCL1i with BCL2 inhibitor that synergistically inhibited UM initiating cell's capacity to expand. Overall, we identify a distinct expression profile of BCL2 family members for UM that makes them susceptible to BCL2 homologous 3 mimetics.

Circulating CD8+ mucosal-associated invariant T cells correlate with improved treatment responses and overall survival in anti-PD-1-treated melanoma patients

Objectives

While much of the research concerning factors associated with responses to immune checkpoint inhibitors (ICIs) has focussed on the contributions of conventional peptide‐specific T cells, the role of unconventional T cells, such as mucosal‐associated invariant T (MAIT) cells, in human melanoma remains largely unknown. MAIT cells are an abundant population of innate‐like T cells expressing a semi‐invariant T‐cell receptor restricted to the MHC class I‐like molecule, MR1, presenting vitamin B metabolites derived from bacteria. We sought to characterise MAIT cells in melanoma patients and determined their association with treatment responses and clinical outcomes.

Methods

In this prospective clinical study, we analysed the frequency and functional profile of circulating and tumor‐infiltrating MAIT cells in human melanoma patients. Using flow cytometry, we compared these across metastatic sites and between ICI responders vs. non‐responders as well as healthy donors.

Results

We identified tumor‐infiltrating MAIT cells in melanomas across metastatic sites and found that the number of circulating MAIT cells is reduced in melanoma patients compared to healthy donors. However, circulating MAIT cell frequencies are restored by ICI treatment in responding patients, correlating with treatment responses, in which patients with high frequencies of MAIT cells exhibited significantly improved overall survival.

Conclusion

Our results suggest that MAIT cells may be a potential predictive marker of responses to immunotherapies and provide rationale for testing MAIT cell‐directed therapies in combination with current and next‐generation ICIs.

Melanoma Metastases to the Adrenal Gland Are Highly Resistant to Immune Checkpoint Inhibitors

BACKGROUND

Adrenal gland metastases (AGMs) are common in advanced-stage melanoma, occurring in up to 50% of patients. The introduction of immune checkpoint inhibitors (ICIs) has markedly altered the outcome of patients with melanoma. However, despite significant successes, anecdotal evidence has suggested that treatment responses in AGMs are significantly lower than in other metastatic sites. We sought to investigate whether having an AGM is associated with altered outcomes and whether ICI responses are dampened in the adrenal glands.

PATIENTS AND METHODS

We retrospectively compared ICI responses and overall survival (OS) in 68 patients with melanoma who were diagnosed with an AGM and a control group of 100 patients without AGMs at a single institution. Response was determined using RECIST 1.1. OS was calculated from time of ICI initiation, anti-PD-1 initiation, initial melanoma diagnosis, and stage IV disease diagnosis. Tumor-infiltrating immune cells were characterized in 9 resected AGMs using immunohistochemical analysis.

RESULTS

Response rates of AGMs were significantly lower compared with other metastatic sites in patients with AGMs (16% vs 22%) and compared with those without AGMs (55%). Patients with AGMs also had significantly lower median OS compared with those without AGMs (3.1 years vs not reached, respectively). We further observed that despite this, AGMs exhibited high levels of tumor-infiltrating immune cells.

CONCLUSIONS

In this cohort of patients with melanoma, those diagnosed with an AGM had lower ICI response rates and OS. These results suggest that tissue-specific microenvironments of AGMs present unique challenges that may require novel, adrenal gland-directed therapies or surgical resection.

Targeting the RIG-I-like receptor signaling pathway to improve the efficacy of immunotherapy in mucosal and uveal melanoma

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Background: Patients with cutaneous (CM) or acral (AM) melanoma have high response rates to immune checkpoint blockade (ICB) therapies including anti-CTLA4, anti-PD1, and their combination. In contrast, patients with mucosal (MM) or uveal (UM) melanoma have low ICB response rates and a poorer overall prognosis. In this study, we analyzed melanoma transcriptomes to identify potential mechanisms underlying ICB resistance in MM and UM. We also evaluated epigenetic modifying drugs as potential agents to improve ICB responses in these patients. Methods: RNA sequencing was performed on 13 MM, 8 AM, and 24 CM patient-derived xenograft tumors. These data were analyzed along with published RNA sequencing data for 80 UM and 443 CM tumors. MM and UM cells were treated with several different classes of epigenetic modifying drugs, and the ICB-resistant YUMM1.7 mouse melanoma syngeneic model was used to evaluate the tumor growth effect of one particular drug, decitabine, at low (2.5 ug) and intermediate (10 ug) doses in combination with anti-PD1 (200 ug). Results: We identified 2513 differentially expressed genes (DEG) between MM and CM tumors (ANODEV adjusted p-value < 0.05, FDR < 0.1) compared to only 495 DEG between AM and CM. Ingenuity Pathway Analysis (IPA) analysis of the 2513 DEG in MM identified the RIG-I-like receptor (RLR) pathway as inhibited in MM versus CM ( p < 1x10-5). The RLR pathway was also inhibited in ICB-resistant CM versus ICI-sensitive (anti-CTLA4, p < 0.006 and anti-PD1, p < 0.0002) and in UM versus CM ( p < 1x10-8), but was not inhibited in AM. The RLR pathway is an innate immune pathogen sensing pathway that is critical for ICB responses in CM; therefore, we sought to identify FDA-approved drugs which activate the RLR pathway in MM and UM. Since RLR signaling is frequently repressed by epigenetic silencing, we screened direct DNMT1 inhibitors 5’-azacitidine (AZA) and 5’-aza-deoxycitidine (decitabine, DEC), several indirect DNMT1 inhibitors, and two HDAC inhibitors. We found that only DEC strongly induced the expression of RLR pathway genes in MM, UM, and ICB-resistant CM cells. Compared to vehicle, treatment of YUMM1.7 tumors with single agent anti-PD1 ( p > 0.87) and low dose ( p > 0.90) or intermediate dose ( p > 0.80) DEC had no effect on tumor growth. However, the addition of either low or intermediate dose DEC to anti-PD1 showed a trend of decreased tumor growth (low dose, 31% decrease, p = 0.22 and intermediate dose, 41% decrease, p = 0.55). Conclusions: We identified low RLR pathway signaling as one possible mechanism underlying ICB resistance in MM and UM. We show that an FDA-approved DNMT1 inhibitor, decitabine, strongly induces RLR pathway genes in MM and UM cells in vitro and leads to tumor growth suppression in combination with anti-PD1 in vivo. Therefore, co-administration of decitabine and anti-PD1 agents is a rational and novel strategy for improving outcomes for MM and UM patients.

Pembrolizumab and all-trans retinoic acid combination treatment of advanced melanoma

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Background: Myeloid-derived suppressor cells (MDSCs) are potent suppressors of antitumor immunity and are commonly associated with poor outcomes in melanoma patients treated with immune checkpoint inhibitors. Inducing the differentiation of MDSCs using all-trans retinoic acid (ATRA) reduces MDSC frequency. This analysis seeks to assess the safety and efficacy of combining ATRA and pembrolizumab in advanced melanoma patients. Methods: This single arm, single institution, phase I/II study (NCT03200847) enrolled 24 patients diagnosed with stage IV melanoma. Eligible patients were over the age of 18 and had not been previously treated anti-PD-1 therapy. Treatment consisted of 200mg Q3W pembrolizumab plus the supplemental treatment of 150 mg/m2 ATRA orally for 3 days surrounding each of the first four infusions of pembrolizumab, with patients continuing pembrolizumab for up to two years until confirmed disease progression or unacceptable toxicity. The primary endpoints were safety and reduction in circulating MDSCs. Secondary endpoints were overall response rate (ORR), disease control rate (DCR), progression free survival (PFS) according to RECIST v1.1. Results: At data cut off (Feb, 2021) 22 patients were evaluable for tumor response. Median follow-up was 1.0 years (0.3-2 years). In general, the combination of pembrolizumab and ATRA was well tolerated. The most common treatment-related adverse events (AEs) were grade 1 or 2, including headache (22 pts, 92%), fatigue (18 pts, 75%), rash (16 pts, 66%), and nausea (8 pts, 33%), most of which corresponded with the 3-day course of ATRA treatment. Ten patients had grade 3 or higher AEs with most being common ICI-related AEs. The ORR was 60% and DCR was 83%. Six-month PFS rate was 62%. Excluding patients diagnosed with uveal melanoma (n = 2) the ORR was 72%, DCR was 86%, and the six-month PFS rate was 68%. Paired analysis showed sustained decreases in absolute numbers ( p = 0.002) and percentage ( p = 0.007) of circulating MDSCs (CD3-CD19-CD56-CD11b+CD33+HLA-DR-/low) 4-6 weeks after stopping ATRA. The study is ongoing and further data will be presented in the future. Conclusions: This study demonstrates that the combination of ATRA and pembrolizumab is well tolerated and suggests that reducing MDSCs with ATRA may enhance the efficacy of pembrolizumab. This strategy of targeting MDSCs in combination with pembrolizumab warrants further development. Research Funding: Merck. Clinical trial information: NCT03200847.

Simultaneously Inhibiting BCL2 and MCL1 Is a Therapeutic Option for Patients with Advanced Melanoma

There is an urgent need to develop treatments for patients with melanoma who are refractory to or ineligible for immune checkpoint blockade, including patients who lack BRAF-V600E/K mutations. This is often the case in patients diagnosed with rare melanoma subtypes such as mucosal and acral melanoma. Here, we analyzed data from the cutaneous melanoma The Cancer Genome Atlas Network (TCGA) transcriptomic and proteomic databases for differential expression of apoptosis molecules between melanomas with or without BRAF hotspot mutations. Our data indicated higher B-cell CLL/lymphoma 2 (BCL2) expression in melanoma without BRAF hotspot mutations, suggesting that BH3 mimetics, such as ABT-199 (venetoclax, a small molecule against BCL2), may be a potential therapeutic option for these patients. We explored the efficacy of combining two BH3 mimetics, ABT-199 and a myeloid cell leukemia sequence 1 (MCL1) inhibitor (S63845 or S64315/MIK665) in cutaneous, mucosal and acral melanomas, in vitro and in vivo. Our data indicate this combination induced cell death in a broad range of melanoma cell lines, including melanoma initiating cell populations, and was more potent in melanoma cells without BRAF-V600E/K mutations. Our knockdown/knockout experiments suggest that several pro-apoptotic BCL2 family members, BCL2-like 11 (apoptosis facilitator) (BIM), phorbol-12-myristate-13-acetate-induced protein 1 (NOXA) or BID, play a role in the combination-induced effects. Overall, our study supports the rationale for combining an MCL1 inhibitor with a BCL2 inhibitor as a therapeutic option in patients with advanced melanoma.

High-Dimensional Analysis of Postsplenectomy Peripheral Immune Cell Changes

Although the consequences of splenectomy are well understood in mice, much less is known about the immunologic changes that occur following splenectomy in humans. We sought to characterize the circulating immune cell populations of patients before and after elective splenectomy to determine if these changes are related to postsplenectomy survival outcomes. Retrospective clinical information was collected from 95 patients undergoing elective splenectomy compared with 91 patients undergoing pancreaticoduodenectomy (Whipple procedure). We further analyzed peripheral blood from five patients in the splenectomy group, collected before and after surgery, using single-cell cytometry by time-of-flight mass spectrometry. We compared pre- and postsplenectomy data to characterize both the major and minor immune cell populations in significantly greater detail. Compared with patients undergoing a Whipple procedure, splenectomized patients had significant and long-lasting elevated counts of lymphocytes, monocytes, and basophils. Cytometry by time-of-flight mass spectroscopy analysis demonstrated that the elevated lymphocytes primarily consisted of naive CD4⁺ T cells and a population of activated CD25⁺CD56⁺CD4⁺ T cells, whereas the elevated monocyte counts were mainly mature, activated monocytes. We also observed a significant increase in the expression of the chemokine receptors CCR6 and CCR4 on several cellular populations. Taken together, these data indicate that significant immunological changes take place following splenectomy. Whereas other groups have compared splenectomized patients to healthy controls, this study compared patients undergoing elective splenectomy to those undergoing a similar major abdominal surgery. Overall, we found that splenectomy results in significant long-lasting changes in circulating immune cell populations and function.

IL-6 and IL-8 Are Linked With Myeloid-Derived Suppressor Cell Accumulation and Correlate With Poor Clinical Outcomes in Melanoma Patients

We sought to identify tumor-secreted factors that altered the frequency of MDSCs and correlated with clinical outcomes in advanced melanoma patients. We focused our study on several of the many factors involved in the expansion and mobilization of MDSCs. These were identified by measuring circulating concentrations of 13 cytokines and growth factors in stage IV melanoma patients (n = 55) and healthy controls (n = 22). Based on these results, we hypothesized that IL-6 and IL-8 produced by melanoma tumor cells participate in the expansion and recruitment of MDSCs and together would be predictive of overall survival in melanoma patients. We then compared the expression of IL-6 and IL-8 in melanoma tumors to the corresponding plasma concentrations and the frequency of circulating MDSCs. These measures were correlated with clinical outcomes. Patients with high plasma concentrations of either IL-6 (40%) or IL-8 (63%), or both (35%) had worse median overall survival compared to patients with low concentrations. Patients with low peripheral concentrations and low tumoral expression of IL-6 and IL-8 showed decreased frequencies of circulating MDSCs, and patients with low frequencies of MDSCs had better overall survival. We have previously shown that IL-6 is capable of expanding MDSCs, and here we show that MDSCs are chemoattracted to IL-8. Multivariate analysis demonstrated an increased risk of death for subjects with both high IL-6 and IL-8 (HR 3.059) and high MDSCs (HR 4.265). Together these results indicate an important role for IL-6 and IL-8 in melanoma patients in which IL-6 potentially expands peripheral MDSCs and IL-8 recruits these highly immunosuppressive cells to the tumor microenvironment. This study provides further support for identifying potential therapeutics targeting IL-6, IL-8, and MDSCs to improve melanoma treatments.

Antagonism of major histocompatibility complex class II invariant chain peptide during chronic lipopolysaccharide treatment rescues autoregulatory behavior

Toll-like receptor 4 (TLR4) activation contributes to vascular dysfunction in pathological conditions such as hypertension and diabetes, but the role of chronic TLR4 activation on renal autoregulatory behavior is unknown. We hypothesized that subclinical TLR4 stimulation with low-dose lipopolysaccharide (LPS) infusion increases TLR4 activation and blunts renal autoregulatory behavior. We assessed afferent arteriolar autoregulatory behavior in male Sprague-Dawley rats after prolonged LPS (0.1 mg·kg^-1·day^-1 sq) infusion via osmotic minipump for 8 or 14 days. Some rats also received daily cotreatment with either anti-TLR4 antibody (1 μg ip), competitive antagonist peptide (CAP; 3 mg/kg ip) or tempol (2 mmol/l, drinking water) throughout the 8-day LPS treatment period. Autoregulatory behavior was assessed using the in vitro blood-perfused juxtamedullary nephron preparation. Selected physiological measures, systolic blood pressure and baseline diameters were normal and similar across groups. Pressure-dependent vasoconstriction averaged 72 ± 2% of baseline in sham rats, indicating intact autoregulatory behavior. Eight-day LPS-treated rats exhibited significantly impaired pressure-mediated vasoconstriction (96 ± 1% of baseline), whereas it was preserved in rats that received anti-TLR4 antibody (75 ± 3%), CAP (84 ± 2%), or tempol (82 ± 2%). Using a 14-day LPS (0.1 mg·kg^-1·day^-1 sq) intervention protocol, CAP treatment started on day 7, where autoregulatory behavior is already impaired. Systolic blood pressures were normal across all treatment groups. Fourteen-day LPS treatment retained the autoregulatory impairment (95 ± 2% of baseline). CAP intervention starting on day 7 rescued pressure-mediated vasoconstriction with diameters decreasing to 85 ± 1% of baseline. These data demonstrate that chronic subclinical TLR4 activation impairs afferent arteriolar autoregulatory behavior through mechanisms involving reactive oxygen species and major histocompatibility complex class II activation.

Adrenal metastases in malignant melanoma, is it a privileged site?

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Background: Currently there is a very limited data reporting response of adrenal metastases to immunotherapy in patients with metastatic malignant melanoma. Certain sites in the body may serve as sanctuary sites due to tumor microenvironment. Lower response rates and shorter PFS are reported in malignant melanoma with liver metastases while higher objective response rates are seen with lung metastases. We hypothesized that adrenal glands are sanctuary sites for melanoma metastases and thus would have poor response to immunotherapy due to steroid production in the adrenals making microenvironment less optimum for the anti-tumor effects of immunotherapy. Methods: A retrospective single-institution chart review of all malignant melanoma with metastasis to adrenal gland treated at University Colorado Hospital from 2008 till 2018, with age ≥ 18 yrs of age who received at least one dose of immunotherapy. Immune-related response criteria (irRC) was used to assess the response to immunotherapy on the imaging. Kaplan Meier estimate, and Chi square test were used for statistical analysis. Results: Sixty-five patients met the inclusion criteria. Mean age of 61 yrs. with range from 25 to 90 yrs. 71% were males and 95% were Caucasians. Median duration of follow up was 51.3 months with range of 1.5-212 months. Forty-three percent were cutaneous, 35% unknown primary, 11% each with mucosal and ocular melanoma. Based on the category of malignant melanoma, 60% were metastatic, 12% nodular, 8% choroidal, 8% superficial spreading, 6% acral lentiginous and 6% other. BRAF mutations were present in 38%, wild type in 54% and unknown in 8%. NRAS was mutated in 18% and wild type in 17% and unknown in 65% of the patients. Comparison of response between adrenal metastasis and non-adrenal metastasis, showed that 71% adrenal metastases had progressive disease compared to 54% of non-adrenal metastases. The overall response rate (ORR) to immunotherapy was 15% in adrenal metastases compared to 20% of non-adrenal metastases. Disease control rate (DCR) was 29% in adrenal metastases compared to 46% non-adrenal metastases with p value = 0.015. Conclusions: The adrenal glands appear to be a sanctuary site for metastases in patients with malignant melanoma receiving immunotherapy. The reasons behind this are unclear but may be related to the microenvironment and local corticosteroid production suppressing the immune response. Preliminary data examining cellular responses in nine surgically removed adrenal metastases support this hypothesis and will be presented.

Abstract A117: Tumor-produced IL-6 and IL-8 are associated with MDSC accumulation and correlate with long-term clinical outcomes in melanoma patients

Background: Recruitment and expansion of immunosuppressive myeloid cells present a significant barrier to the successful treatment of melanoma. We aimed to identify tumor-secreted factors that altered the frequency of MDSCs and correlated with clinical outcomes in advanced melanoma patients. We hypothesized that production of IL-6 and IL-8 by melanoma tumors would lead to expansion and accumulation of MDSCs and correlate with long-term clinical outcomes. Methods: Expression of IL-6 and IL-8 in melanoma tumors as well as the plasma concentration of IL-6 and IL-8 were measured and compared with the frequency of circulating MDSCs in a total of 52 stage IV melanoma patients. These measures were correlated with tumor burden, BRAF status, lactic acid dehydrogenase (LDH) levels and with clinical outcomes. Samples were collected beginning in January 2011 and clinical follow-up was collected through January 2018. Results: The plasma concentration of both IL-6 and IL-8 correlated with tumor burden (p &lt; 0.0001 and p= 0.0122, respectively). Patients with high plasma concentrations of either IL-6 (40%) or IL-8 (63%) had worse median overall survival (MOS) (7.5 months, p &lt; 0.0001 and 9.2 months, p = 0.0015, respectively) compared to patients with low concentrations, where MOS was not reached. Patients with high plasma concentrations of both IL-6 and IL-8 (35%) had even worse MOS (6.7 months) than patients with low levels of both cytokines (MOS not reached, 31%) p &lt; 0.0001. We observed that patients with lower circulating concentrations and lower tumoral expression of IL-6 and IL-8 showed decreased frequencies of circulating MDSCs. Furthermore, patients with low frequencies of MDSCs (MOS not reached) had better overall survival than patients with high frequencies of these cells (MOS 11.9 months) p = 0.0224. Multivariable analysis showed that when adjusting for variables BRAF status and LDH in the model, the hazard for the event of death for subjects with both high IL-6 and IL-8 is 4.46 times (95% CI, 1.4, 14.2) that of the hazard for the subjects with low IL-6 and IL-8 (p = 0.01). Additionally, the hazard of death for subjects with higher total MDSCs is 3.3 times (95% CI, 1.2, 9.0) that for subjects with low total MDSCs. Conclusions: The durability of the nearly 7-year follow-up time for these advanced melanoma patients further strengthens the implied importance of IL-6 and IL-8 in the accumulation of MDSC’s in melanoma patients. These data provide clues for potential therapeutic targets in advanced melanoma patients.

Citation Format: Richard P. Tobin, Kimberly R. Jordan, Dana Davis, Victoria M. Vorwald, Kasey Couts, Dexiang Gao, Derek E Smith, William A Robinson, Virginia Borges, Martin D McCarter. Tumor-produced IL-6 and IL-8 are associated with MDSC accumulation and correlate with long-term clinical outcomes in melanoma patients [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A117.

Targeting myeloid-derived suppressor cells using all-trans retinoic acid in melanoma patients treated with Ipilimumab

BACKGROUND

Immune checkpoint inhibitors have improved overall survival rates for many cancers, yet the majority of patients do not respond to treatment and succumb to disease progression. One tumor-related mechanism limiting the efficacy of immunotherapies in melanoma is the recruitment and expansion of myeloid-derived suppressor cells (MDSCs). Therefore, targeting MDSCs in combination with immunotherapies is an attractive strategy to improve response rates and effectiveness.

METHODS

We tested this strategy by designing a randomized phase II clinical trial treating advanced melanoma patients with either Ipilimumab monotherapy or Ipilimumab plus all-trans retinoic acid (ATRA). Clinicaltrails.gov identifier (NCT02403778). The frequency of circulating MDSCs and the activation of CD8(+) T cells was measured by flow cytometry. Expression of immunosuppressive genes was measured with quantitative real time-PCR. T cell suppressive functions were measured by mixed lymphocyte reaction.

RESULTS

Here we show that in vitro treatment with ATRA decreases immunosuppressive function of MDSCs in mixed lymphocyte reactions. Additionally, ATRA reduces the expression of immunosuppressive genes including PD-L1, IL-10, and indoleamine 2,3‑dioxygenase by MDSCs. Furthermore, the addition of ATRA to standard of care Ipilimumab therapy appears safe, as ATRA did not increase the frequency of grade 3 or 4 adverse events. Finally, ATRA significantly decreased the frequency of circulating MDSCs compared to Ipilimumab treatment alone in advanced-stage melanoma patients.

CONCLUSIONS

These results illustrate the importance of MDSCs in immunotherapy resistance and provide evidence that targeting MDSCs in cancer patients may augment immunotherapeutic approaches.

Effects of in vitro ATRA treatment on human MDSC expansion and function

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Background: Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of immature immunosuppressive myeloid cells that are expanded in tumor bearing hosts. Melanoma patients with high frequencies of MDSCs have decreased overall survival and an increased risk of death and disease progression, as well as impaired responses to ipilimumab. Targeting MDSCs to decease their frequency or suppressive activity may provide an effective means to improve the efficacy of anti-cancer therapies. All-trans retinoic acid (ATRA) is a vitamin A derivative currently used to treat APL that may target MDSCs. ATRA differentiates immature myeloid cells into macrophages, dendritic cells, or granulocytes. ATRA has been tested as an MDSC targeting agent in two completed caner clinical trials and is being investigated in several other open and completed trials. Methods: We purified myeloid cells from LRS chambers collected from normal donors. The purified cells were treated with GM-CSF+IL-6, GM-CSF+IL-4, or melanoma conditioned media with or without ATRA. After 5 days of incubation, PCR was used to determine the expression of immunoregulatory genes. Additionally, we used a MLR to determine the effect of ATRA on MDSC’s T cell suppressive function. Results: Here we report that in vitro ATRA treatment decreases the expression of ARG1, NOX1, INOS, and PD-L1. Further, we report that ATRA treatment improved T cell proliferation. Conclusions: Controlling MDSC suppressive function and accumulation may provide a mechanism to improve the efficacy of many current cancer therapies. Here we show that ATRA reduces the expression of the immunosuppressive genes ARG1, NOX1, INOS, and PD-L1 in MDSCs. Additionally, we show that treatment of MDSCs with ATRA decreases MDSC’s ability to suppress T cell proliferation. These results indicate that ATRA may improve the efficacy of conventional and immnunotherapeutic treatments.

The clinical evidence for targeting human myeloid-derived suppressor cells in cancer patients

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that represent a formidable obstacle to the successful treatment of cancer. Patients with high frequencies of MDSCs have significantly decreased progression-free survival (PFS) and overall survival (OS). Whereas there is experimental evidence that the reduction of the number and/or suppressive function of MDSCs in mice improves the efficacy of anti-cancer therapies, there is notably less evidence for this therapeutic strategy in human clinical trials. Here, we discuss currently available data concerning MDSCs from human clinical trials and explore the evidence that targeting MDSCs may improve the efficacy of cancer therapies.

Immunosuppressive myeloid-derived suppressor cells are increased in splenocytes from cancer patients

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that are increased in the peripheral blood of cancer patients and limit productive immune responses against tumors. Immunosuppressive MDSCs are well characterized in murine splenic tissue and are found at higher frequencies in spleens of tumor-bearing mice. However, no studies have yet analyzed these cells in parallel human spleens. We hypothesized that MDSCs would be increased in the spleens of human cancer patients, similar to tumor-bearing mice. We compared the frequency and function of MDSC subsets in dissociated human spleen from 16 patients with benign pancreatic cysts and 26 patients with a variety of cancers. We found that total MDSCs (Lin^neg CD11b^pos CD33^pos HLA-DR^neg), granulocytic MDSCs (additional markers CD14^neg CD15^pos), and monocytic MDSCs (CD14^pos CD15^neg) were identified in human spleen. The monocytic subset was the most prominent in both spleen and peripheral blood and the granulocytic subset was expanded in the spleen relative to matched peripheral blood samples. Importantly, the frequency of CD15^pos MDSCs in the spleen was increased in patients with cancer compared to patients with benign pancreatic cysts and was associated with a significantly increased risk of death and decreased overall survival. Finally, MDSCs isolated from the spleen suppressed T cell responses, demonstrating for the first time the functional capacity of human splenic MDSCs. These data suggest that the human spleen is a potential source of large quantities of cells with immunosuppressive function for future characterization and in-depth studies of human MDSCs.

Abstract P318: miR-155 Induces Inflammation by Polarizing M1 Macrophages in a TLR3-induced Preeclamptic Mouse Model

Placental microRNA (miRNA) expression is known to be dysregulated during preeclampsia (PE), a hypertensive pregnancy disorder but the role it plays in the pathogenesis of PE is currently unknown. We have previously demonstrated that placental miR-155 expression is upregulated (P-PIC: 3.15 fold, p<0.05 vs. controls) in a TLR3-induced PE mouse model similar to PE patients. In addition, poly I:C (PIC) treatment significantly increased systolic blood pressure (SBP) at gestational day 17 in P-PIC WT (147±4.5 mmHg) compared to P WT mice (103±2.7 mmHg), but did not have any effect in P-PIC miR-155 KO mice (101±2 mmHg). In PE there is an increase in the number of total and activated macrophages. M1 macrophages display the capacity to shift T cell responses toward a TH1 while M2 macrophages promote a TH2 response. We hypothesized that TLR3-induced upregulation of miR-155 contributes to hypertension in part by polarizing the macrophages to a M1 phenotype and these effects will be attenuated in P-PIC miR-155 KO mice. Placental flow cytometry analyses demonstrate that administration of poly I:C induced CD45(+) CD11b(+) macrophages in P-PIC WT mice which is attenuated in P-PIC miR-155 KO mice. In addition, placental classical ‘M1’ macrophages CD45(+) CD11b(+) CD86(+) CD206(-) were increased and alternate ‘M2’ macrophages CD45(+) CD11b(+) CD206(+) CD86(-) were decreased in P-PIC WT mice compared to controls. Interestingly, administration of poly I:C did not change M1 macrophages but increased M2 macrophages in P-PIC miR-155 KO mice. P-PIC WT mice exhibited increased placental expression of additional M1 markers (NOS2, IFNg) and decreased expression of M2 markers (Arg1, IL-10) compared to controls by qRTPCR but not in P-PIC miR-155 KO mice. The above observations are also consistent with our splenic flow cytometry and qRTPCR studies. Based on our results, miR-155 activation induces inflammation in part by increasing M1 macrophages thus contributing to hypertension. Targeting the innate immune system by inhibition of monocyte/macrophages may have beneficial cardiovascular effects in women with PE.

Abstract P178: Depletion of Gamma-Delta T Cells Protects Against Toll-Like Receptor-Induced Preeclampsia in Mice

Preeclampsia (PE), a hypertensive disorder of pregnancy, is associated with vascular endothelial dysfunction and excessive immunity and inflammation. However, it is unclear which innate immune cells propagate the pro-inflammatory state. Gamma-delta T (gdT) cells can secrete tolerogenic anti-inflammatory cytokines or cytotoxic pro-inflammatory cytokines depending on their activation status. gdT cells from women with PE produce significantly more IFNg and perforin and are less susceptible to apoptosis than gdT cells from normal pregnant women. We hypothesized that Toll-like receptor (TLR) activation in gdT cells induces inflammation and causes PE-like features in mice and that gdT cell KO mice would be resistant to developing TLR-induced PE-like features. Activation of splenocytes isolated from day 14 normal pregnant mice with the TLR3 agonist poly I:C or the TLR7 agonist R837 for 24 hours significantly increased gdT cells as well as IFNg and TNFa production. We have reported that poly I:C or R837 treatment of normal pregnant mice elicits a pregnancy-dependent PE-like syndrome by inducing a pro-inflammatory immune response. Pregnant poly I:C-treated and R837-treated mice had significantly increased splenic levels of gdT cells and plasma levels of IFNg and TNFa compared to pregnant vehicle-treated mice. Pregnant gdT cell KO mice treated with poly I:C or R837 did not develop hypertension or endothelial dysfunction. These data demonstrate that gdT cells mediate the TLR-induced PE-like features in mice and depletion of gdT cells may reduce the severity of PE in women.

Abstract P056: MHC CLass II-associated Invariant Peptide (CLIP) Antagonism During Chronic Lipopolysaccharide Treatment Preserves Afferent Arteriolar Autoregulatory Behavior

Lipopolysaccharide (LPS) is a cell wall component of gram-negative bacteria that can activate toll-like receptor 4, which in turn, activates the innate immune system. Chronic immune system activation is linked to blunted afferent arteriolar autoregulatory behavior and kidney injury. MHC Class II-associated invariant peptide (CLIP) provides a critical step in antigen processing, presentation, and adaptive immune system activation. Accordingly, we postulated that treatment with a competitive CLIP antagonist (CAP) during chronic low-dose LPS exposure would preserve afferent arteriolar autoregulatory behavior. Rats were implanted with osmotic minipumps (day 0) for infusion of LPS (0.01mg/kg/day) or saline (0.9% NaCl; 0.5μl/hr) for 8 days and then the kidneys were harvested for juxtamedullary nephron studies. Four groups (n=6/group) were studied: Control, LPS, LPS + CAP and Sham + CAP. Both LPS + CAP and Sham + CAP groups were treated with CAP (3mg/kg/day; i.p.) on days 1-7. Autoregulatory behavior was assessed in these groups by increasing perfusion pressure in 15 mmHg increments from 65 to 170 mmHg. Starting baseline diameters were similar across the control (15.2 ± 1.2 μm), LPS (14.1 ± 1.0 μm), LPS + CAP (15.1 ± 1.0), and Sham + CAP (15.7 ± 0.6) groups. When perfusion pressure was increased from 65 to 170 mmHg, control and sham + CAP afferent arteriolar diameter decreased significantly by 26 ± 4% and 25 ± 2% (P<0.05), respectively. In contrast, afferent diameters from LPS treated kidneys decreased by just 5 ± 2% over the same pressure range indicating impaired afferent arteriolar autoregulatory behavior. In LPS + CAP treated kidneys, afferent arteriolar diameter decreased by 17 ± 2% (P<0.05) over the same pressure range signifying preservation of autoregulatory behavior. These data support the hypothesis that CLIP antagonism during chronic low dose LPS treatment preserves afferent arteriolar autoregulatory behavior. Inhibiting CLIP may open novel therapeutic targets for inflammatory kidney disease.

γδ T Cells and dendritic cells in refractory Lyme arthritis

Lyme disease is a multisystem infection transmitted by tick vectors with an incidence of up to 300,000 individuals/yr in the United States. The primary treatments are oral or i.v. antibiotics. Despite treatment, some individuals do not recover and have prolonged symptoms affecting multiple organs, including the nervous system and connective tissues. Inflammatory arthritis is a common symptom associated with Lyme pathology. In the past decades, γδ T cells have emerged as candidates that contribute to the transition from innate to adaptive responses. These cells are also differentially regulated within the synovia of patients affected by RLA. Here, we review and discuss potential cellular mechanisms involving γδ T cells and DCs in RLA. TLR signaling and antigen processing and presentation will be the key concepts that we review in aid of understanding the impact of γδ T cells in RLA.

Cotreatment with interleukin 4 and interleukin 10 modulates immune cells and prevents hypertension in pregnant mice

BACKGROUND

Excessive maternal immune system activation plays a central role in the development of the hypertensive disorder of pregnancy preeclampsia (PE). The immunomodulatory cytokines interleukin 4 (IL-4) and interleukin 10 (IL-10) are dysregulated during PE; therefore we hypothesized that treatment with both recombinant IL-4 and IL-10 during pregnancy could prevent the development of PE in mice.

METHODS

Using our mouse model of PE in which immune system activation is induced by the double-stranded RNA receptor agonist poly I:C, we gave daily injections of IL-4, IL-10, or both on days 13-17 of pregnancy. Mice were then killed on day 18.

RESULTS

Poly I:C caused a significant increase in systolic blood pressure in pregnant (P-PIC) mice compared with vehicle-treated pregnant (P) mice. All 3 treatments significantly decreased blood pressure in P-PIC mice to P levels, ameliorated the endothelial dysfunction, and decreased placental TLR3 levels in P-PIC mice. However, only IL-4/IL-10 cotreatment prevented the proteinuria and increased incidence of fetal demise in P-PIC mice; IL-4 or IL-10 alone had no effect. Additionally, only IL-4/IL-10 cotreatment prevented the significant increase in CD3(+)/γδ(+) T cells and CD11c(+) dendritic cells and significant decrease in CD11b(+)/CD14(-) suppressor monocytes, as well as completely prevented placental necrosis, in P-PIC mice. Importantly, IL-4/IL-10 cotreatment in P mice had no detrimental effects.

CONCLUSIONS

Taken together, these data demonstrate that exogenous IL-4 and IL-10 administration concurrently during pregnancy can normalize immune cell subsets and prevent PE induced by maternal immune system activation.

Traumatic brain injury causes selective, CD74-dependent peripheral lymphocyte activation that exacerbates neurodegeneration

Introduction

Traumatic brain injury (TBI), a significant cause of death and disability, causes, as in any injury, an acute, innate immune response. A key component in the transition between innate and adaptive immunity is the processing and presentation of antigen by professional antigen presenting cells (APCs). Whether an adaptive immune response to brain injury is beneficial or detrimental is not known. Current efforts to understand the contribution of the immune system after TBI have focused on neuroinflammation and brain-infiltrating immune cells. Here, we characterize and target TBI-induced expansion of peripheral immune cells that may act as potential APCs. Because MHC Class II-associated invariant peptide (CLIP) is important for antigen processing and presentation, we engineered a competitive antagonist (CAP) for CLIP, and tested the hypothesis that peptide competition could reverse or prevent neurodegeneration after TBI.

Results

We show that after fluid percussion injury (FPI), peripheral splenic lymphocytes, including CD4+ and CD8+ T cells, regulatory T cells (Tregs), and γδ T cells, are increased in number within 24 hours after FPI. These increases were reversed by CAP treatment and this antagonism of CLIP also reduced neuroinflammation and neurodegeneration after TBI. Using a mouse deficient for the precursor of CLIP, CD74, we observed decreased peripheral lymphocyte activation, decreased neurodegeneration, and a significantly smaller lesion size following TBI.

Conclusion

Taken together, the data support the hypothesis that neurodegeneration following TBI is dependent upon antigen processing and presentation that requires CD74.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0143-5) contains supplementary material, which is available to authorized users.

Levetiracetam Differentially Alters CD95 Expression of Neuronal Cells and the Mitochondrial Membrane Potential of Immune and Neuronal Cells in vitro

Epilepsy is a neurological seizure disorder that affects over 100 million people worldwide. Levetiracetam, either alone, as monotherapy, or as adjunctive treatment, is widely used to control certain types of seizures. Despite its increasing popularity as a relatively safe and effective anti-convulsive treatment option, its mechanism(s) of action are poorly understood. Studies have suggested neuronal, glial, and immune mechanisms of action. Understanding the precise mechanisms of action of levetiracetam would be extremely beneficial in helping to understand the processes involved in seizure generation and epilepsy. Moreover, a full understanding of these mechanisms would help to create more efficacious treatments while minimizing side-effects. The current study examined the effects of levetiracetam on the mitochondrial membrane potential of neuronal and non-neuronal cells, in vitro, in order to determine if levetiracetam influences metabolic processes in these cell types. In addition, this study sought to address possible immune-mediated mechanisms by determining if levetiracetam alters the expression of immune receptor–ligand pairs. The results show that levetiracetam induces expression of CD95 and CD178 on NGF-treated C17.2 neuronal cells. The results also show that levetiracetam increases mitochondrial membrane potential on C17.2 neuronal cells in the presence of nerve growth factor. In contrast, levetiracetam decreases the mitochondrial membrane potential of splenocytes and this effect was dependent on intact invariant chain, thus implicating immune cell interactions. These results suggest that both neuronal and non-neuronal anti-epileptic activities of levetiracetam involve control over energy metabolism, more specifically, mΔΨ. Future studies are needed to further investigate this potential mechanism of action.

Microvascular endothelial cell hyperpermeability induced by endogenous caspase 3 activator staurosporine

BACKGROUND

Microvascular hyperpermeability following conditions such as hemorrhagic shock occurs mainly owing to disruption of the adherens junctional protein complex in endothelial cells. The objective of this study was to examine the action of staurosporine, a potent activator of endogenous caspase 3 on the adherens junction and the cellular pathway through which it causes possible endothelial cell barrier dysfunction.

METHODS

Rat lung microvascular endothelial cell (RLMEC) permeability was measured by fluorescein isothiocyanate-albumin flux across the monolayer in a Transwell plate. Integrity of the endothelial cell adherens junctions was studied using immunofluorescence of β-catenin and vascular endothelial-cadherin. Mitochondrial reactive oxygen species formation was determined by using dihydrorhodamine 123 and mitochondrial transmembrane potential by JC-1 fluorescent probe and flow cytometry. Caspase 3 enzyme activity was assayed fluorometrically. Cell death assay in RLMECs was performed using propidium iodide staining and analyzed by flow cytometry.

RESULTS

Staurosporine (1 µM)-treated RLMEC monolayers showed significant increase in permeability, which was decreased by pretreatment with caspase 3 specific inhibitor, Z-DEVD-FMK (p < 0.05). Immunofluorescence studies showed staurosporine induced disruption of the adherens junction, which was reversed by Z-DEVD-FMK. Staurosporine treatment led to an increase in mitochondrial reactive oxygen species formation and a decrease in mitochondrial transmembrane potential. Furthermore, staurosporine induced a significant increase in caspase 3 activity (p < 0.05) but not cell death in RLMECs (p < 0.05).

CONCLUSION

Staurosporine-induced disruption of the adherens junction and microvascular endothelial cell hyperpermeability is associated with the activation of mitochondrial "intrinsic" apoptotic signaling cascade but without causing endothelial cell death. Our results suggest that prevention of mitochondrial-mediated activation of caspase 3 has therapeutic potential against microvascular hyperpermeability.

The downregulation of Mcl-1 via USP9X inhibition sensitizes solid tumors to Bcl-xl inhibition

Background

It has been shown in many solid tumors that the overexpression of the pro-survival Bcl-2 family members Bcl-xL and Mcl-1 confers resistance to a variety of chemotherapeutic agents. Mcl-1 is a critical survival protein in a variety of cell lineages and is critically regulated via ubiquitination.

Methods

The Mcl-1, Bcl-xL and USP9X expression patterns in human lung and colon adenocarcinomas were evaluated via immunohistochemistry. Interaction between USP9X and Mcl-1 was demonstrated by immunoprecipitation-western blotting. The protein expression profiles of Mcl-1, Bcl-xL and USP9X in multiple cancer cell lines were determined by western blotting. Annexin-V staining and cleaved PARP western blotting were used to assay for apoptosis. The cellular toxicities after various treatments were measured via the XTT assay.

Results

In our current analysis of colon and lung cancer samples, we demonstrate that Mcl-1 and Bcl-xL are overexpressed and also co-exist in many tumors and that the expression levels of both genes correlate with the clinical staging. The downregulation of Mcl-1 or Bcl-xL via RNAi was found to increase the sensitivity of the tumor cells to chemotherapy. Furthermore, our analyses revealed that USP9X expression correlates with that of Mcl-1 in human cancer tissue samples. We additionally found that the USP9X inhibitor WP1130 promotes Mcl-1 degradation and increases tumor cell sensitivity to chemotherapies. Moreover, the combination of WP1130 and ABT-737, a well-documented Bcl-xL inhibitor, demonstrated a chemotherapeutic synergy and promoted apoptosis in different tumor cells.

Conclusion

Mcl-1, Bcl-xL and USP9X overexpression are tumor survival mechanisms protective against chemotherapy. USP9X inhibition increases tumor cell sensitivity to various chemotherapeutic agents including Bcl-2/Bcl-xL inhibitors.

Abstract 173: Depletion of CLIP+ Immune Cells Prevents Toll-Like Receptor-Induced Preeclampsia in Mice

Preeclampsia (PE) is a pregnancy-specific disorder of vascular endothelial dysfunction and inflammation which manifests as hypertension and proteinuria and may result from maladaptation of the maternal immune system. Activation of the dsRNA receptor Toll-like receptor 3 (TLR3) or the ssRNA receptor TLR7 elicits pregnancy-dependent hypertension and endothelial dysfunction in mice in part by increasing pro-inflammatory immune cells. Polyclonal activation of immune cells is associated with expression of Class II-Associated Invariant Peptide Chain (CLIP) in MHC class II which prevents T cell-dependent death leading to persistent immune cell activation. We hypothesized that removal of CLIP reduces pro-inflammatory immune cells and prevents the development of PE in mice. Pregnant mice were given ip injections of normal saline (P), poly I:C (TLR3 agonist; P-PIC), or R837 (TLR7 agonist; P-R837) with or without TPP, a custom-targeted peptide that removes CLIP from MHC class II, on gestational days 13, 15, and 17 and euthanized on day 18. TPP treatment significantly decreased pro-inflammatory CD3+/γδ T cells and increased anti-inflammatory CD4+/CD25+ regulatory T cells in TLR3-induced PE mice as well as TLR7-induced PE mice. TPP treatment also prevented the hypertension (GD17 SBP in mmHg: P=102±3, P+TPP=105±4, P-PIC=147±4*, P-PIC+TPP=103±2, P-R837=133±2*, P-R837+TPP=106±4; *p<0.05 vs. P), proteinuria, and endothelial dysfunction in TLR3-induced and TLR7-induced PE mice while having no detrimental effects in normal pregnant mice. Based on our results, the TPP-mediated decrease in detrimental immune cells positively modulated T cell subsets and prevented the development of PE-like symptoms in mice. CLIP removal from MHC class II with TPP may be a promising therapy for women with PE.

TLR-mediated B cell activation results in ectopic CLIP expression that promotes B cell-dependent inflammation

Infectious pathogens produce compounds called Toll ligands that activate TLRs on lymphocytes. Acute activation triggered by certain TLRs appears to "jump start" the innate immune response, characterized by the release of inflammatory cytokines and cellular expansion. In some individuals, there is a failure to control acute inflammation, resulting in postinfectious, chronic inflammation. Susceptibility to chronic inflammation is strongly associated with an individual's MHC genes. Recent clinical trials for several autoimmune diseases characterized by chronic inflammation suggest that B lymphocyte depletion therapies dampen chronic immune activation. However, currently, there is no known mechanism that accounts for the correlation among TLR activation, MHC genetics, and a pathological role for B-lymphocytes. Our hypothesis is that TLR-activated B cells (B cells that have been polyclonally activated in the absence of antigen-specific signals) are not controlled properly by T cell-dependent B cell death, thereby causing B cell-dependent chronic inflammation. Here, we show that treatment with Toll ligands results in polyclonal B cell activation accompanied by ectopic expression of CLIP. Furthermore, by adoptively transferring purified CLIP+ B cells in syngeneic animals, we find that CLIP+ B cells induce production of TNF-α by host T cells. Finally, we demonstrate that CLIP-targeted peptide competition results in the death of polyclonally activated CLIP+ B cells.

Increased plasma beta-endorphin immunoreactivity in scuba divers after submersion

Increased plasma beta-endorphin immunoreactivity in scuba divers after submersion. Med. Sci. Sports Exerc., Vol. 19, No. 2, pp. 87-90, 1987. After submersion under water in a motionless state of neutral buoyancy, scuba divers frequently report feelings of well-being or euphoria similar to those reported after strenuous exercise. Since strenuous exercise is associated with a stress-related increase in plasma beta-endorphin immunoreactivity (beta-EIR), this study was undertaken to measure plasma beta-EIR after submersion in a state of neutral buoyancy under conditions that do not involve strenuous exercise or other extreme stresses. Plasma beta-EIR was measured by radioimmunoassay in male scuba divers before and immediately after remaining motionless 10 ft under water in a state of neutral buoyancy. A significant (P less than 0.01) increase in plasma beta-EIR was found under these conditions. Venipuncture and scuba breathing out of the water did not alter beta-EIR levels. These results indicate that the milder stress associated with submersion in a state of neutral buoyancy involves an increase in plasma beta-EIR similar to that caused by severe stress.