GPR4 Knockout Attenuates Intestinal Inflammation and Forestalls the Development of Colitis-Associated Colorectal Cancer in Murine Models

GPR4 is a proton-sensing G protein-coupled receptor highly expressed in vascular endothelial cells and has been shown to potentiate intestinal inflammation in murine colitis models. Herein, we evaluated the proinflammatory role of GPR4 in the development of colitis-associated colorectal cancer (CAC) using the dextran sulfate sodium (DSS) and azoxymethane (AOM) mouse models in wild-type and GPR4 knockout mice. We found that GPR4 contributed to chronic intestinal inflammation and heightened DSS/AOM-induced intestinal tumor burden. Tumor blood vessel density was markedly reduced in mice deficient in GPR4, which correlated with increased tumor necrosis and reduced tumor cell proliferation. These data demonstrate that GPR4 ablation alleviates intestinal inflammation and reduces tumor angiogenesis, development, and progression in the AOM/DSS mouse model.

Increased interleukin-6/C-reactive protein levels are associated with the upregulation of the adenosine pathway and serve as potential markers of therapeutic resistance to immune checkpoint inhibitor-based therapies in non-small cell lung cancer

BACKGROUND

Systemic immune activation, hallmarked by C-reactive protein (CRP) and interleukin-6 (IL-6), can modulate antitumor immune responses. In this study, we evaluated the role of IL-6 and CRP in the stratification of patients with non-small cell lung cancer (NSCLC) treated with immune checkpoint inhibitors (ICIs). We also interrogated the underlying immunosuppressive mechanisms driven by the IL-6/CRP axis.

METHODS

In cohort A (n=308), we estimated the association of baseline CRP with objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) in patients with NSCLC treated with ICIs alone or with chemo-immunotherapy (Chemo-ICI). Baseline tumor bulk RNA sequencing (RNA-seq) of lung adenocarcinomas (LUADs) treated with pembrolizumab (cohort B, n=59) was used to evaluate differential expression of purine metabolism, as well as correlate IL-6 expression with PFS. CODEFACS approach was applied to deconvolve cohort B to characterize the tumor microenvironment by reconstructing the cell-type-specific transcriptome from bulk expression. Using the LUAD cohort from The Cancer Genome Atlas (TCGA) we explored the correlation between IL-6 expression and adenosine gene signatures. In a third cohort (cohort C, n=18), plasma concentrations of CRP, adenosine 2a receptor (A2aR), and IL-6 were measured using ELISA.

RESULTS

In cohort A, 67.2% of patients had a baseline CRP≥10 mg/L (CRP-H). Patients with CRP-H achieved shorter OS (8.6 vs 14.8 months; p=0.006), shorter PFS (3.3 vs 6.6 months; p=0.013), and lower ORR (24.7% vs 46.3%; p=0.015). After adjusting for relevant clinical variables, CRP-H was confirmed as an independent predictor of increased risk of death (HR 1.51, 95% CI: 1.09 to 2.11) and lower probability of achieving disease response (OR 0.34, 95% CI: 0.13 to 0.89). In cohort B, RNA-seq analysis demonstrated higher IL-6 expression on tumor cells of non-responders, along with a shorter PFS (p<0.05) and enrichment of the purinergic pathway. Within the TCGA LUAD cohort, tumor IL-6 expression strongly correlated with the adenosine signature (R=0.65; p<2.2e-16). Plasma analysis in cohort C demonstrated that CRP-H patients had a greater median baseline level of A2aR (6.0 ng/mL vs 1.3 ng/mL; p=0.01).

CONCLUSIONS

This study demonstrates CRP as a readily available blood-based prognostic biomarker in ICI-treated NSCLC. Additionally, we elucidate a potential link of the CRP/IL-6 axis with the immunosuppressive adenosine signature pathway that could drive inferior outcomes to ICIs in NSCLC and also offer novel therapeutic avenues.

Transwell In Vitro Cell Migration and Invasion Assays

Cell migration and invasion have essential roles in both normal physiology and disease. As such, methodologies to assess cell migratory and invasive capacities are necessary to elucidate normal cell processes and underlying mechanisms of disease. Here, we describe commonly used transwell in vitro methods for the study of cell migration and invasion. The transwell migration assay involves the chemotaxis of cells through a porous membrane after the establishment of a chemoattractant gradient using two medium-filled compartments. The transwell invasion assay involves the addition of an extracellular matrix on top of the porous membrane which only permits chemotaxis of cells which possess invasive properties such as tumor cells.

Case Report: Peripheral blood T cells and inflammatory molecules in lung cancer patients with immune checkpoint inhibitor-induced thyroid dysfunction: Case studies and literature review

Immunotherapy has changed the paradigm of cancer treatment, yet immune checkpoint inhibitors (ICIs) such as PD-1/PD-L1 monoclonal antibodies may cause immune-related adverse events (irAEs) in some patients. In this report, two non-small cell lung cancer (NSCLC) patients treated with nivolumab presented with checkpoint inhibitor-induced thyroid dysfunction (CITD), followed by a second irAE of pneumonitis and intestinal perforation, respectively. Increases in peripheral CD8⁺ T cells correlated with the onset of CITD in the patients. Intriguingly, common inflammatory biomarkers, including C-reactive protein (CRP) and neutrophil/lymphocyte ratio (NLR), were not consistently increased during the onset of CITD but were substantially increased during the onset of pneumonitis and intestinal perforation irAEs. The observations suggest that unlike other irAEs such as pneumonitis, CRP levels and NLR were non-contributory in diagnosing CITD, whereas T cell expansion may be associated with immunotherapy-induced thyroiditis.

Complex Role of Microbiome in Pancreatic Tumorigenesis: Potential Therapeutic Implications

Pancreatic cancer (PC) is the fourth leading cause of cancer-related mortality with limited diagnostic and therapeutic options. Although immunotherapy has shown promise in the treatment of several cancers, its role in pancreatic cancer is rather limited. Several studies have focused on determining the role of the tumor microenvironment with cancer-cell-intrinsic events and tumor-infiltrating immune cellular properties. However, in the past decade, there has been emerging research aimed at delineating the role of the host microbiome, including the metabolites from microbes and host responses, on pancreatic tumorigenesis. Importantly, there is emerging evidence suggesting the beneficial role of a gut microbiome transplant to improve immunotherapeutic outcomes in cancer patients. In this review, we summarize the recent understanding of the role of the microbiome in pancreatic cancer progression, along with its clinical diagnostic and therapeutic implications.

Peripheral blood t cell responses to immunotherapy related adverse events in metastatic non-small cell lung cancer

e21047

Background: There has been prospective and retrospective evidence for the onset of immunotherapy (IO) related adverse events (irAE) and efficacy of anti programmed death (PD1) and Programmed death Ligand 1(PD L1) antibodies. The incidence of irAE in these studies ranged anywhere from 30-44%. There have been attempts in the past to cluster irAEs into distinct subtypes by T cell profiling before and after immunotherapy. Identifying the trend of CD4/CD8 changes during irAE may aid in finding ways to mitigate the severe toxicities, so the benefits of immunotherapy can be extended to far more number of patients. Methods: We have collected blood samples from 20 patients of Non Small Cell Lung Cancer patients (NSCLC) before each cycle of immunotherapy with informed consent. We have measured the different inflammatory markers such as IL6, IL10 using ELISA and isolated cellular components such as CD4, CD8 T cells along with others using magnetic bead technique, from these samples in our research laboratory at East Carolina University. We have also collected clinical information including the adverse events with their (Common Terminology Criteria for Adverse events) CTCAE 5.0 grading, different cell counts and C- reactive Protein (CRP). Results: In the cohort of 20 patients, 9 experienced irAE, out of which 6 had grade 2, including thyroiditis, pneumonitis, dermatitis, cytokine release syndrome (CRS), 1 had grade 3 pneumonitis, 1 had grade 4 pneumonitis and 1 had grade 1 CRS. When we looked at the CD4/CD8 ratio before each cycle, the one prior to the incidence of the irAE had at least 30-40% drop in the ratio consistently although there were minor fluctuations in the ratio at other times in both directions. Conclusions: Although most irAEs can be treated and reversed with steroids and other immunosuppressive agents, prolonged immunosuppression can lead to reduced efficacy of IO and development of undue opportunistic infections. Experience with IO has shown that earlier initiation of immunosuppression shortens the required treatment. However, given the challenge in the subtility of the earlier presentation, therapies are frequently delayed. Hence, biomarker to identify the early manifestations is of critical importance for early intervention. Studies suggest there is clonal expansion of CD8 T cells preceding grade 2-3 irAEs. Studies also indicate that increased T cells in the tumor is indicative of response to immunotherapy. Our observation suggests that increased CD8 in proportion to CD4 in the peripheral blood precedes the onset of irAE. It is unclear as to how this leads to increased toxicity when the immunotherapy treatment works by affecting T cell function. One possible explanation is that the T cell response in the tumor tissue is beneficial, however, T cell response in the peripheral blood may indicate response against self antigens leading to toxicities in the form of irAE.

Can GPR4 Be a Potential Therapeutic Target for COVID-19?

Coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), first emerged in late 2019 and has since rapidly become a global pandemic. SARS-CoV-2 infection causes damages to the lung and other organs. The clinical manifestations of COVID-19 range widely from asymptomatic infection, mild respiratory illness to severe pneumonia with respiratory failure and death. Autopsy studies demonstrate that diffuse alveolar damage, inflammatory cell infiltration, edema, proteinaceous exudates, and vascular thromboembolism in the lung as well as extrapulmonary injuries in other organs represent key pathological findings. Herein, we hypothesize that GPR4 plays an integral role in COVID-19 pathophysiology and is a potential therapeutic target for the treatment of COVID-19. GPR4 is a pro-inflammatory G protein-coupled receptor (GPCR) highly expressed in vascular endothelial cells and serves as a "gatekeeper" to regulate endothelium-blood cell interaction and leukocyte infiltration. GPR4 also regulates vascular permeability and tissue edema under inflammatory conditions. Therefore, we hypothesize that GPR4 antagonism can potentially be exploited to mitigate the hyper-inflammatory response, vessel hyper-permeability, pulmonary edema, exudate formation, vascular thromboembolism and tissue injury associated with COVID-19.

The Proton-Sensing GPR4 Receptor Regulates Paracellular Gap Formation and Permeability of Vascular Endothelial Cells

GPR4 is a pH-sensing G protein-coupled receptor highly expressed in vascular endothelial cells and can be activated by protons in the inflamed tissue microenvironment. Herein, we report that acidosis-induced GPR4 activation increases paracellular gap formation and permeability of vascular endothelial cells through the G_α12/13/Rho GTPase signaling pathway. Evaluation of GPR4 in the inflammatory response using the acute hindlimb ischemia-reperfusion mouse model revealed that GPR4 mediates tissue edema, inflammatory exudate formation, endothelial adhesion molecule expression, and leukocyte infiltration in the inflamed tissue. Genetic knockout and pharmacologic inhibition of GPR4 alleviate tissue inflammation. These results suggest GPR4 is a pro-inflammatory receptor and could be targeted for therapeutic intervention.

•

Acidosis/GPR4 regulates endothelial paracellular gap formation and permeability

•

GPR4 exacerbates inflammation by increasing tissue edema and leukocyte infiltration

•

Pharmacological inhibition of GPR4 reduces inflammatory responses

Isolated neutropenia as a rare but serious adverse event secondary to immune checkpoint inhibition

BACKGROUND

Compared to conventional chemotherapy, Immune checkpoint inhibitors (ICI) are known to have a distinct toxicity profile commonly identified as immune-related adverse events (irAEs). These irAEs that are believed to be related to immune dysregulations triggered by ICI can be serious and lead to treatment interruptions and in severe cases, precipitate permanent discontinuation. Isolated neutropenia secondary to ICI has been rarely documented in the literature and needs further description. We report a case of pembrolizumab related severe isolated neutropenia in a patient with metastatic non-small cell lung cancer. We were also able to obtain serial blood and plasma-based biomarkers for this patient during treatment and during neutropenia to understand trends that may correlate with the irAE. In addition we summarize important findings from other studies reporting on ICI related neutropenia.

CASE PRESENTATION

A 74 years old Caucasian male treated with single-agent pembrolizumab for metastatic non-small cell lung cancer presented with fevers, chills, and an isolated neutrophil count (ANC) of 0 2 weeks after the fourth dose. In addition to antibiotics, due to the strong suspicion of this neutropenia being immune-mediated, he was started on 1 mg/kg of steroids and also received filgrastim to accelerate neutrophil recovery. Serial trends in C-reactive protein and certain other inflammatory cytokines demonstrated a corresponding rise at the time of neutropenia. Post recovery, his pembrolizumab was kept on hold. Eight weeks later he had a second episode of neutropenia which was again managed similar to the first episode. Despite permanent discontinuation of ICI after the first neutropenia, his disease showed an ongoing complete metabolic response on imaging. Our literature review reveals that hematological toxicities constitute < 1% irAEs with isolated neutropenia roughly accounting for one-fourth of the hematological irAEs. Based on the handful of ICI related neutropenia cases reported to date, we identified nivolumab to be the most common offender. The median number of ICI cycles administered before presenting with neutropenia was three, and the median time to recovery was approximately two weeks. All of these neutropenic episodes were ≥ grade 3 and led to permanent ICI discontinuation. Using immunosuppressive therapies in conjunction with granulocyte-colony stimulating factor was the most common strategy described to have favorable results.

CONCLUSION

Neutropenia as an isolated irAE secondary to ICI is rare but represents a severe toxicity that needs early recognition and can often result in treatment discontinuations. Careful monitoring of these patients with the prompt initiation of immunosuppressive and supportive measures to promote rapid recovery as well as prevent and treat infectious complications should be part of the management algorithms. Serial monitoring of blood and plasma-based biomarkers from more extensive studies may help in identifying patients at risk for irAEs and thus guide patient selection for ICI.

Abstract 1206: Inhibition of GPR4 attenuates intestinal inflammation in a mouse colitis model

Inflammatory bowel disease (IBD), a chronic inflammatory disorder of the digestive tract, is associated with a higher risk of colorectal cancer development. Current therapeutic approaches for IBD are limited and primarily include biologics and steroids such as anti-TNFα monoclonal antibodies and glucocorticoids. Chronic usage, however, can cause significant adverse drug effects such as increased risk of infection and lymphoma in some patients. GPR4, a pH-sensing G protein-coupled receptor, has recently emerged as a potential therapeutic target for intestinal inflammation. Previous studies demonstrate that GPR4 is a pro-inflammatory receptor expressed in vascular endothelial cells (EC) and stimulates leukocyte-EC adhesion and extravasation. Knockout of GPR4 alleviates intestinal inflammation in IBD mouse models. In this study, we have assessed the effects of a recently developed GPR4 antagonist, 2-(4-((2-Ethyl-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)methyl)phenyl)-5-(piperidin-4-yl)-1,3,4-oxadiazole (GPR4 antagonist 13, also known as NE 52-QQ57), in the dextran sulfate sodium (DSS)-induced acute colitis mouse model. The GPR4 antagonist 13 inhibited intestinal inflammation. All colitis parameters, such as body weight loss, fecal score, colon shortening, splenic expansion, and mesenteric lymph node enlargement, were reduced in the GPR4 antagonist 13 treatment group compared to the vehicle group. Histopathological features of active colitis and inflammatory gene expression of colon tissues were reduced in the GPR4 antagonist 13 treatment group compared to vehicle control. Our results indicate that the GPR4 antagonist 13 provides a protective effect in the DSS-induced colitis mouse model and inhibition of GPR4 can be explored as a novel anti-inflammatory approach.

Citation Format: Edward J. Sanderlin, Mona Marie, Juraj Velcicky, Pius Loetscher, Li V. Yang. Inhibition of GPR4 attenuates intestinal inflammation in a mouse colitis model [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 1206.

Tumor mutational burden (TMB) profile of K-RAS/TP-53 co-mutation in metastatic non-small cell lung cancer (m-NSCLC)

2626

Background: Early data suggests that co-occurring genetic events define biological heterogeneity in K-RAS mutant NSCLC, with K-RAS/ TP-53 (KP) co-mutated subset having potential therapeutic vulnerabilities to immune checkpoint blockade (ICB). To explore the immunological basis for these findings, we evaluated the immune biomarker profile (TMB/PD-L1) in KP mutant m-NSCLC using a large next-generation sequencing (NGS) dataset. Methods: Caris life sciences NGS dataset consisting of 1317 m-NSCLC tissue samples from 2016-18 was queried. PD-L1pos was defined as ≥ 1% staining using 22c3 Dako assay. TMB was measured by counting all somatic non-synonymous missense mutations using targeted NGS (592 genes). TMB-high (H) was defined as ≥ 10 mutations/Megabase (mut/Mb). P-values were calculated using Chi-square and Mann-Whitney test. Results: K-RAS mutations were identified in 28.7% (378/1317). Within this K-RAS mutant group, KP subset constituted 49.4% (187/378), remaining were K-RAS mutated/ TP-53 wild type (K-Pwt). 72.2 % (135/187) of KP had PD-L1pos with 51.9% (97/187) having PD-L1 ≥ 50%. KP had higher median TMB vs. K-Pwt (14.5 vs. 9.0 mut/Mb, p<0.001) and higher % of TMB-H vs. K-Pwt (79.9 vs. 45.1%, p<0.001; Table). Even in the PD-L1neg group, KP had higher % of TMB-H vs. K-Pwt (86.5 vs. 41.5%, p<0.001). K-RAS or TP-53 exon-subtypes had no difference in median TMB or % of TMB-H. Across metastatic sites, brain tissue had the highest % of KP subset (38.3%, 68/187) followed by bone (28.9%, 54/187). Within KP subset, brain tissue had higher median TMB vs. bone (16 vs. 11 mut/Mb, p<0.01) as well as greater % of TMB-H vs. bone (86.5 vs. 68.5%, p=0.01). Conclusions: This is the largest dataset to date highlighting the unique immune profile of KP mutant m-NSCLC. Our results show that KP subset has a significantly higher TMB than K-Pwt, especially in the PD-L1neg subgroup. Metastatic site-specific variations in TMB were also observed for the KP subset. These findings could have therapeutic implications in guiding patient selection for ICB and merit prospective investigation.[Table: see text]

Introduction of WT-TP53 into pancreatic cancer cells alters sensitivity to chemotherapeutic drugs, targeted therapeutics and nutraceuticals

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive, highly metastatic malignancy and accounts for 85% of pancreatic cancers. PDAC patients have poor prognosis with a five-year survival of only 5-10%. Mutations at the TP53 gene are readily detected in pancreatic tumors isolated from PDAC patients. We have investigated the effects of restoration of wild-type (WT) TP53 activity on the sensitivity of pancreatic cancer cells to: chemotherapy, targeted therapy, as well as, nutraceuticals. Upon introduction of the WT-TP53 gene into the MIA-PaCa-2 pancreatic cancer cell line, the sensitivity to drugs used to treat pancreatic cancer cells such as: gemcitabine, fluorouracil (5FU), cisplatin, irinotecan, oxaliplatin, and paclitaxel increased significantly. Likewise, the sensitivity to drugs used to treat other cancers such as: doxorubicin, mitoxantrone, and 4 hydroxy tamoxifen (4HT) also increased upon introduction of WT-TP53 into MIA-PaCa-2 cells. Furthermore, the sensitivity to certain inhibitors which target: PI3K/mTORC1, PDK1, SRC, GSK-3, and biochemical processes such as proteasomal degradation and the nutraceutical berberine as increased upon introduction of WT-TP53. Furthermore, in some cases, cells with WT-TP53 were more sensitive to the combination of drugs and suboptimal doses of the MDM2 inhibitor nutlin-3a. However, TP53-independent effects of nutlin-3a were observed upon treatment with either a proteasomal or a PI3K/mTOR inhibitor. These studies indicate the sensitizing effects that WT-TP53 can have in PDAC cells which normally lack WT-TP53 to various therapeutic agents and suggest approaches to improve PDAC therapy.

Abstract 1691: Clinical characteristics influencing survival in stage-IV non-small cell lung cancer treated with nivolumab: A single-institutional experience

Background: Immune-checkpoint blockade (ICB) using antibodies directed against the programmed cell death-1 (PD-1) axis has revolutionized the management of non-small cell lung cancer (NSCLC). Based on results from the Checkmate 017 and 057, nivolumab, an anti-PD-1 antibody, has emerged as the standard of care in the second line setting for advanced NSCLC. However, the lack of uniform responses as noted in daily practice suggests clinical heterogeneity. Hence, it is essential to identify characteristics that may predict inferior efficacy to ICB. Methods: Retrospectively we identified 61 stage IV NSCLC patients treated with nivolumab from April 2015 to March 2017 after progressing on a platinum doublet. These patients were part of an ongoing institutionally approved prospective biomarker-based study. Follow up cutoff for survival analysis was set on October 1, 2017. Overall survival after immunotherapy (OSI) was defined as the time from ICB initiation to last follow up or death. Cox regression was used to assess the correlation of clinical and biochemical factors influencing OSI. Results: The median age was 63 years with predominant histology being adenocarcinoma in 65.6 %. A majority of patients were of Caucasian ethnicity (68.9%) and male gender (60.7%). Skeletal involvement (54.1 %), liver (27.9 %) and brain (26.2 %) were the most common metastatic compartments. Simultaneous involvement of greater than 1 metastatic compartment at ICB initiation was observed in 54.1% of patients. Approximately 67.3 % patients were either former/never smoker at the time of nivolumab initiation. The median OSI for our NSCLC cohort treated with nivolumab was 6.3 months. On adjusted Cox univariate analysis of the clinically relevant covariates, baseline factors present at anti-PD-1 initiation that were associated with inferior OSI were age greater than 65 [p= 0.036; 2.37 (1.05-5.30)], brain metastasis [p=0.014; 3.30 (1.25-7.37)] and greater than 1 metastatic compartment involvement [P=0.041; 2.78 (1.04-7.44). Using adjusted multivariate Cox regression model with backward elimination, all three factors were noted to be independently associated with inferior OSI.Conclusions: Our study identified subgroups with certain baseline clinical features that tend to behave poorly despite ICB. This suggests that improving outcomes in such subgroups may require exploring strategies involving combination ICB or other novel targeted therapies. Also, better identification of such subgroups via larger datasets may help in the appropriate designation of patients for optimally tailored ICB and thus assist in improving outcomes in NSCLC.

Citation Format: Abdul Rafeh Naqash, Chipman R. Stroud, Li V. Yang, Mahvish Muzaffar, Paul R. Walker. Clinical characteristics influencing survival in stage-IV non-small cell lung cancer treated with nivolumab: A single-institutional experience [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1691.

Effects of resveratrol, curcumin, berberine and other nutraceuticals on aging, cancer development, cancer stem cells and microRNAs

Natural products or nutraceuticals have been shown to elicit anti-aging, anti-cancer and other health-enhancing effects. A key target of the effects of natural products may be the regulation of microRNA (miR) expression which results in cell death or prevents aging, diabetes, cardiovascular and other diseases. This review will focus on a few natural products, especially on resveratrol (RES), curcumin (CUR) and berberine (BBR). RES is obtained from the skins of grapes and other fruits and berries. RES may extend human lifespan by activating the sirtuins and SIRT1 molecules. CUR is isolated from the root of turmeric (Curcuma longa). CUR is currently used in the treatment of many disorders, especially in those involving an inflammatory process. CUR and modified derivatives have been shown to have potent anti-cancer effects, especially on cancer stem cells (CSC). BBR is also isolated from various plants (e.g., Coptis chinensis) and has been used for centuries in traditional medicine to treat diseases such as adult- onset diabetes. Understanding the benefits of these and other nutraceuticals may result in approaches to improve human health.

Survival stratification using a baseline inflammatory physiology based scoring system in advanced non-small cell lung cancer (NSCLC) treated with anti-programmed cell death-1 (anti-PD-1) therapy

152

Background: Immune checkpoint blockade (ICB) has shown promise in NSCLC with improved survival and durability in disease control. Despite these advances, the response to ICB remains variable. Thus identifying easily available biomarkers that can assist in the optimal selection of patients for ICB holds paramount importance. Methods: Retrospectively we identified 87 stage III/IV NSCLC patients initiated on anti-PD-1 therapy from April 2015 to March 2017 after progressing on a platinum doublet. These patients were part of an ongoing prospective biomarker-based study at our institution. Follow up cutoff for survival analysis was set at October 1, 2017. Enrolled participants had inflammatory markers (C-reactive protein, absolute neutrophil count, absolute lymphocyte count, serum albumin) measured on the day of first dose of anti-PD-1 administration as well as subsequent doses. Using multivariate Cox analysis, factors demonstrating an association with overall survival after immunotherapy (OSI) were used to develop a composite score to stratify patient survival. Results: The median age was 64 years with predominant histology being adenocarcinoma in 46.0 % followed by squamous cell carcinoma (43.7 %). Stage IV disease was present in 70.1%, with skeletal involvement (54.1 %) and liver (27.9 %) being the most common metastatic sites. In the multivariate Cox regression with backward elimination, factors independently associated with OSI were noted to be: CRP, neutrophil-lymphocyte ratio, and prognostic nutritional index. A composite inflammatory biomarker score was developed using the B-coefficients from the Cox multivariate regression. A score > 1 demonstrated inferior OSI compared to a score of ≤ 1 [1.7 vs. 9.3 months; P < 0.001, HR 4.00, 95% CI (2.21-7.25)]. Conclusions: This study provides preliminary evidence in favor of a composite inflammation based score that can aid in survival stratification of these patients. Validation of this score in prospective NSCLC trials to elucidate its potential utility as a predictive or prognostic tool in facilitating optimal patient selection for ICB is required.

Contextual tumor suppressor function of T cell death-associated gene 8 (TDAG8) in hematological malignancies

Background

Extracellular acidosis is a condition found within the tumor microenvironment due to inadequate blood perfusion, hypoxia, and altered tumor cell metabolism. Acidosis has pleiotropic effects on malignant progression; therefore it is essential to understand how acidosis exerts its diverse effects. TDAG8 is a proton-sensing G-protein-coupled receptor that can be activated by extracellular acidosis.

Methods

TDAG8 gene expression was analyzed by bioinformatic analyses and quantitative RT-PCR in human hematological malignancies. Retroviral transduction was used to restore TDAG8 expression in U937, Ramos and other blood cancer cells. Multiple in vitro and in vivo tumorigenesis and metastasis assays were employed to evaluate the effects of TDAG8 expression on blood cancer progression. Western blotting, immunohistochemistry and biochemical approaches were applied to elucidate the underlying mechanisms associated with the TDAG8 receptor pathway.

Results

TDAG8 expression is significantly reduced in human blood cancers in comparison to normal blood cells. Severe acidosis, pH 6.4, inhibited U937 cancer cell proliferation while mild acidosis, pH 6.9, stimulated its proliferation. However, restoring TDAG8 gene expression modulated the U937 cell response to mild extracellular acidosis and physiological pH by reducing cell proliferation. Tumor xenograft experiments further revealed that restoring TDAG8 expression in U937 and Ramos cancer cells reduced tumor growth. It was also shown U937 cells with restored TDAG8 expression attached less to Matrigel, migrated slower toward a chemoattractant, and metastasized less in severe combined immunodeficient mice. These effects correlated with a reduction in c-myc oncogene expression. The mechanistic investigation indicated that Gα13/Rho signaling arbitrated the TDAG8-mediated c-myc oncogene repression in response to acidosis.

Conclusions

This study provides data to support the concept that TDAG8 functions as a contextual tumor suppressor down-regulated in hematological malignancies and potentiation of the TDAG8 receptor pathway may be explored as a potential anti-tumorigenic approach in blood cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1305-6) contains supplementary material, which is available to authorized users.

Roles of GSK-3 and microRNAs on epithelial mesenchymal transition and cancer stem cells

Various signaling pathways exert critical roles in the epithelial to mesenchymal transition (EMT) and cancer stem cells (CSCs). The Wnt/beta-catenin, PI3K/PTEN/Akt/mTORC, Ras/Raf/MEK/ERK, hedgehog (Hh), Notch and TP53 pathways elicit essential regulatory influences on cancer initiation, EMT and progression. A common kinase involved in all these pathways is moon-lighting kinase glycogen synthase kinase-3 (GSK-3). These pathways are also regulated by micro-RNAs (miRs). TP53 and components of these pathways can regulate the expression of miRs. Targeting members of these pathways may improve cancer therapy in those malignancies that display their abnormal regulation. This review will discuss the interactions of the multi-functional GSK-3 enzyme in the Wnt/beta-catenin, PI3K/PTEN/Akt/mTORC, Ras/Raf/MEK/ERK, Hh, Notch and TP53 pathways. The regulation of these pathways by miRs and their effects on CSC generation, EMT, invasion and metastasis will be discussed.

Abstract 5916: Proton-sensor GPR4 potentiates intestinal inflammation in the DSS-induced colitis mouse model

Inflammation and tissue acidosis are two factors that co-exist in inflammatory bowel disease (IBD) and can contribute to increased risk of colorectal cancer (CRC) development. GPR4 is a proton-sensing G protein-coupled receptor that can be activated by extracellular acidosis through several histidine residues and subsequently signal through downstream G-protein pathways. Recently, GPR4 has been shown to be activated by acidosis and can increase the expression of numerous inflammatory and stress response genes in vascular endothelial cells (ECs) and has functionally increased EC-leukocyte adhesion. Subsequently, genetic and small molecule approaches for the inhibition of GPR4 activity have reduced endothelial cell inflammation. In this study, we examined the role of GPR4 in intestinal inflammation using a dextran sulfate sodium (DSS)-induced colitis mouse model. We observed that GPR4 mRNA expression was increased in mouse and human IBD tissues when compared to control intestinal tissues. To determine the function of GPR4 in intestinal inflammation, wild-type and GPR4-deficient mice were treated with 3% DSS for acute and chronic time points for the induction of colitis. Our results showed that the severity of colitis was decreased in GPR4-deficient DSS-treated mice in comparison to wild-type DSS-treated mice. Clinical parameters, macroscopic disease indicators, and histopathological features were less severe in the DSS-treated GPR4-deficient mice than the DSS-treated wild-type mice. Inflammatory gene expression, endothelial adhesion molecule expression, leukocyte infiltration, and isolated lymphoid follicle (ILF) formation were reduced in intestinal tissues of DSS-treated GPR4-null mice. In summary, our results suggest GPR4 potentiates intestinal inflammation as the absence of GPR4 ameliorates intestinal inflammation in the DSS-induced colitis mouse model. Use of GPR4 inhibitors could prove a valuable therapeutic in the reduction of intestinal inflammation and subsequent CRC development.

Note: This abstract was not presented at the meeting.

Citation Format: Edward J. Sanderlin, Nancy R. Leffler, Kvin Lertpiriyapong, Qi Cai, Heng Hong, Vasudevan Bakthavatchalu, James G. Fox, Joani Z. Oswald, Calvin R. Justus, Elizabeth A. Krewson, Dorcas O’Rourke, Li V. Yang. Proton-sensor GPR4 potentiates intestinal inflammation in the DSS-induced colitis mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5916. doi:10.1158/1538-7445.AM2017-5916

Abstract 1993: Acidic tumor microenvironment stimulation of GPR4 alters cytoskeletal dynamics and migration of vascular endothelial cells

The acidic tumor microenvironment results from aberrant vasculature, insufficient oxygen delivery and aerobic glycolysis of cancer cells. As cancer progresses, the acidic microenvironment can lead to structural changes of endothelial cells (ECs) resulting in increased vascular permeability which may increase metastasis. Extracellular acidification can activate cellular signaling molecules, including G-protein coupled receptor 4 (GPR4), which is prominently expressed in ECs. We have previously reported that acidic activation of GPR4 induces the transcription of several pro-inflammatory and ER-stress related genes in ECs. The purpose of the study is to identify the functional response of acidosis-induced GPR4 activity using Human Umbilical Vein Endothelial Cells (HUVECs) as a model system. The expression of GPR4 was overexpressed (HUVEC/GPR4) or knocked down (GPR4 shRNA) using several genetic constructs. HUVECs were treated with media buffered to pH 6.4 or to physiological pH 7.4. Permeability of a HUVEC cell monolayer was assessed by quantifying gap formation as one indicator. Cell migration was assessed through wound-healing assays. Cytoskeletal dynamics were also investigated using Rhodamine Phalloidin to investigate actin stress fiber formation and immunocytochemistry to investigate focal adhesion dynamics. Our results showed acidic pH induced GPR4 activation changed the cytoskeletal phenotype, decreased cellular migration, and proliferation in HUVECs compared to the physiological pH treatment. There was also a further increase in gap area of a HUVEC/GPR4 monolayer and formation of actin stress fibers in response to acidic conditions. Additionally, altering expression of phosphorylated paxillin and focal adhesion kinase were observed under acidosis/GPR4 mediated stress. In conclusion, the proton sensor GPR4 induces cytoskeletal variations, reduces cellular migration, and proliferation in response to an acidic tumor microenvironment.

Citation Format: Elizabeth A. Krewson, Li V. Yang, Lixue Dong. Acidic tumor microenvironment stimulation of GPR4 alters cytoskeletal dynamics and migration of vascular endothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1993. doi:10.1158/1538-7445.AM2017-1993

Abstract 3217: Novel prostamide, 15-deoxy-delta12,14 prostamide J2, displays activity against melanoma in vitro and in vivo: potential role of endoplasmic reticulum stress

Melanoma is the most aggressive and deadly form of cutaneous neoplasm in the United States, representing a major clinical challenge. Our lab previously demonstrated that the endocannabinoid, arachidonoyl ethanolamide (AEA), induced cell death in non-melanoma skin cancer (NMSC) cells through the cyclooxygenase-2 (COX-2) mediated formation of novel J-series prostamides (PMJs). We were the first to chemically synthesize the primary metabolite, 15-deoxy-Δ12,14 prostamide J2 (15d-PMJ2), which displayed potent and selective cytotoxicity in NMSC cells. As such, we hypothesize that the selective cytotoxicity of 15d-PMJ2 would be observed in other forms of skin cancer, including melanoma. B16F10 murine melanoma cells and nontumorigenic Melan-A cells were treated with different concentrations of 15d-PMJ2 for 24 hours and cell viability was measured using MTS assays. At 5µM, 15d-PMJ2 decreased viability by 63% in B16F10 cells, while Melan-A viability was not affected. To verify that cell death was due to apoptosis, the cleavage of apoptotic markers caspase-3 and PARP was examined by conducting Western blot analysis. 15d-PMJ2 markedly increased caspase-3 and PARP cleavage only in B16F10 melanoma cells. Previous studies in NMSC indicated that 15d-PMJ2 induced ER-stress and apoptosis. To investigate the mechanism of 15d-PMJ2-mediated death in melanoma, we examined ER-stress responses. Melan-A and B16F10 melanoma cells were treated with 5µM 15d-PMJ2 and evaluated for CHOP10 and p-PERK expression by Western blot analysis. B16F10, but not Melan-A cells exhibited a notable increase in CHOP10 and p-PERK expression when treated with 15d-PMJ2. To further examine the role of ER-stress on 15d-PMJ2 mediated apoptosis, B16F10 cells were pretreated with the ER-stress inhibitors salubrinal and 4-phenylbutyric acid (PBA). Both salubrinal and PBA decreased activation of caspase-3/7, suggesting that ER-stress plays an important role in 15d-PMJ2 mediated tumor cell death. To determine the anti-melanoma activity of 15d-PMJ2 in vivo, B16F10 allograft tumors grown in C57BL/6 mice were dosed subcutaneously with 0.5 or 5.0 mg/kg 15d-PMJ2 for 5 days. Tumors treated with 15d-PMJ2 exhibited significantly reduced growth and mean weights compared to vehicle and untreated animals. TUNEL analysis of tumor tissues indicated a large presence of necrotic and apoptotic cells in 15d-PMJ2-treated tumors compared to vehicle and untreated tumors. To determine whether 15d-PMJ2 induced ER-stress in vivo, tumors were assayed for p-PERK and CHOP10 levels by immunohistochemistry (IHC). These markers were significantly elevated in 15d-PMJ2-treated tumors. Similarly, the viability of primary patient-derived melanoma cells was significantly decreased by 15d-PMJ2. These findings suggest that the novel prostamide, 15d-PMJ2, possesses potent and selective anti-melanoma activity in vitro and in vivo.

Citation Format: Daniel A. Ladin, Li V. Yang, Timothy L. Fitzgerald, Rukiyah Van Dross. Novel prostamide, 15-deoxy-delta12,14 prostamide J2, displays activity against melanoma in vitro and in vivo: potential role of endoplasmic reticulum stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3217. doi:10.1158/1538-7445.AM2017-3217

Synthesis and Evaluation of the Novel Prostamide, 15-Deoxy, Δ12,14-Prostamide J2, as a Selective Antitumor Therapeutic

15-deoxy, Δ^12,14-prostaglandin J₂-ethanolamide, also known as 15-deoxy, Δ^12,14-prostamide J₂ (15d-PMJ₂) is a novel product of the metabolism of arachidonoyl ethanolamide (AEA) by COX-2. 15d-PMJ₂ preferentially induced cell death and apoptosis in tumorigenic A431 keratinocytes and B16F10 melanoma cells compared with nontumorigenic HaCaT keratinocytes and Melan-A melanocytes. Activation of the ER stress execution proteins, PERK and CHOP10, was evaluated to determine whether this process was involved in 15d-PMJ₂ cell death. 15d-PMJ₂ increased the phosphorylation of PERK and expression of CHOP10 in tumorigenic but not nontumorigenic cells. The known ER stress inhibitors, salubrinal and 4-phenylbutaric acid, significantly inhibited 15d-PMJ₂-mediated apoptosis, suggesting ER stress as a primary apoptotic mediator. Furthermore, the reactive double bond present within the cyclopentenone structure of 15d-PMJ₂ was identified as a required moiety for the induction of ER stress apoptosis. The effect of 15d-PMJ₂ on B16F10 melanoma growth was also evaluated by dosing C57BL/6 mice with 0.5 mg/kg 15d-PMJ₂ Tumors of animals treated with 15d-PMJ₂ exhibited significantly reduced growth and mean weights compared with vehicle and untreated animals. TUNEL and IHC analysis of tumor tissues showed significant cell death and ER stress in tumors of 15d-PMJ₂-treated compared with control group animals. Taken together, these findings suggest that the novel prostamide, 15d-PMJ₂, possesses potent antitumor activity in vitro and in vivoMol Cancer Ther; 16(5); 838-49. ©2017 AACR.

Acidosis Activates Endoplasmic Reticulum Stress Pathways through GPR4 in Human Vascular Endothelial Cells

Acidosis commonly exists in the tissue microenvironment of various pathophysiological conditions such as tumors, inflammation, ischemia, metabolic disease, and respiratory disease. For instance, the tumor microenvironment is characterized by acidosis and hypoxia due to tumor heterogeneity, aerobic glycolysis (the "Warburg effect"), and the defective vasculature that cannot efficiently deliver oxygen and nutrients or remove metabolic acid byproduct. How the acidic microenvironment affects the function of blood vessels, however, is not well defined. GPR4 (G protein-coupled receptor 4) is a member of the proton-sensing G protein-coupled receptors and it has high expression in endothelial cells (ECs). We have previously reported that acidosis induces a broad inflammatory response in ECs. Acidosis also increases the expression of several endoplasmic reticulum (ER) stress response genes such as CHOP (C/EBP homologous protein) and ATF3 (activating transcription factor 3). In the current study, we have examined acidosis/GPR4- induced ER stress pathways in human umbilical vein endothelial cells (HUVEC) and other types of ECs. All three arms of the ER stress/unfolded protein response (UPR) pathways were activated by acidosis in ECs as an increased expression of phosphorylated eIF2α (eukaryotic initiation factor 2α), phosphorylated IRE1α (inositol-requiring enzyme 1α), and cleaved ATF6 upon acidic pH treatment was observed. The expression of other downstream mediators of the UPR, such as ATF4, ATF3, and spliced XBP-1 (X box-binding protein 1), was also induced by acidosis. Through genetic and pharmacological approaches to modulate the expression level or activity of GPR4 in HUVEC, we found that GPR4 plays an important role in mediating the ER stress response induced by acidosis. As ER stress/UPR can cause inflammation and cell apoptosis, acidosis/GPR4-induced ER stress pathways in ECs may regulate vascular growth and inflammatory response in the acidic microenvironment.

GPR4 deficiency alleviates intestinal inflammation in a mouse model of acute experimental colitis

GPR4 is a proton-sensing G protein-coupled receptor that can be activated by extracellular acidosis. It has recently been demonstrated that activation of GPR4 by acidosis increases the expression of numerous inflammatory and stress response genes in vascular endothelial cells (ECs) and also augments EC-leukocyte adhesion. Inhibition of GPR4 by siRNA or small molecule inhibitors reduces endothelial cell inflammation. As acidotic tissue microenvironments exist in many types of inflammatory disorders, including inflammatory bowel disease (IBD), we examined the role of GPR4 in intestinal inflammation using a dextran sulfate sodium (DSS)-induced acute colitis mouse model. We observed that GPR4 mRNA expression was increased in mouse and human IBD tissues when compared to control intestinal tissues. To determine the function of GPR4 in intestinal inflammation, wild-type and GPR4-deficient mice were treated with 3% DSS for 7days to induce acute colitis. Our results showed that the severity of colitis was decreased in GPR4-deficient DSS-treated mice in comparison to wild-type DSS-treated mice. Clinical parameters, macroscopic disease indicators, and histopathological features were less severe in the DSS-treated GPR4-deficient mice than the DSS-treated wild-type mice. Endothelial adhesion molecule expression, leukocyte infiltration, and isolated lymphoid follicle (ILF) formation were reduced in intestinal tissues of DSS-treated GPR4-null mice. Collectively, our results suggest GPR4 provides a pro-inflammatory role in the inflamed gut as the absence of GPR4 ameliorates intestinal inflammation in the acute experimental colitis mouse model.

Roles of TP53 in determining therapeutic sensitivity, growth, cellular senescence, invasion and metastasis

TP53 is a critical tumor suppressor gene that regulates cell cycle progression, apoptosis, cellular senescence and many other properties critical for control of normal cellular growth and death. Due to the pleiotropic effects that TP53 has on gene expression and cellular physiology, mutations at this tumor suppressor gene result in diverse physiological effects. T53 mutations are frequently detected in numerous cancers. The expression of TP53 can be induced by various agents used to treat cancer patients such as chemotherapeutic drugs and ionizing radiation. Radiation will induce Ataxia telangiectasia mutated (ATM) and other kinases that results in the phosphorylation and activation of TP53. TP53 is also negatively regulated by other mechanisms, such as ubiquitination by ligases such as MDM2. While TP53 has been documented to control the expression of many "classical" genes (e.g., p21^Cip-1, PUMA, Bax) by transcriptional mechanisms for quite some time, more recently TP53 has been shown to regulate microRNA (miR) gene expression. Different miRs can promote oncogenesis (oncomiR) whereas others act to inhibit tumor progression (tumor suppressor miRs). Targeted therapies to stabilize TP53 have been developed by various approaches, MDM2/MDM4 inhibitors have been developed to stabilize TP53 in TP53-wild type (WT) tumors. In addition, small molecules have been isolated that will reactivate certain mutant TP53s. Both of these types of inhibitors are in clinical trials. Understanding the actions of TP53 may yield novel approaches to suppress cancer, aging and other health problems.

Effects of mutations in Wnt/β-catenin, hedgehog, Notch and PI3K pathways on GSK-3 activity-Diverse effects on cell growth, metabolism and cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that participates in an array of critical cellular processes. GSK-3 was first characterized as an enzyme that phosphorylated and inactivated glycogen synthase. However, subsequent studies have revealed that this moon-lighting protein is involved in numerous signaling pathways that regulate not only metabolism but also have roles in: apoptosis, cell cycle progression, cell renewal, differentiation, embryogenesis, migration, regulation of gene transcription, stem cell biology and survival. In this review, we will discuss the roles that GSK-3 plays in various diseases as well as how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK, Wnt/beta-catenin, hedgehog, Notch and TP53. Mutations that occur in these and other pathways can alter the effects that natural GSK-3 activity has on regulating these signaling circuits that can lead to cancer as well as other diseases. The novel roles that microRNAs play in regulation of the effects of GSK-3 will also be evaluated. Targeting GSK-3 and these other pathways may improve therapy and overcome therapeutic resistance.

Comparison study of distinguishing cancerous and normal prostate epithelial cells by confocal and polarization diffraction imaging

Accurate classification of malignant cells from benign ones can significantly enhance cancer diagnosis and prognosis by detection of circulating tumor cells (CTCs). We have investigated two approaches of quantitative morphology and polarization diffraction imaging on two prostate cell types to evaluate their feasibility as single-cell assay methods toward CTC detection after cell enrichment. The two cell types have been measured by a confocal imaging method to obtain their three-dimensional morphology parameters and by a polarization diffraction imaging flow cytometry (p-DIFC) method to obtain image texture parameters. The support vector machine algorithm was applied to examine the accuracy of cell classification with the morphology and diffraction image parameters. Despite larger mean values of cell and nuclear sizes of the cancerous prostate cells than the normal ones, it has been shown that the morphologic parameters cannot serve as effective classifiers. In contrast, accurate classification of the two prostate cell types can be achieved with high classification accuracies on measured data acquired separately in three measurements. These results provide strong evidence that the p-DIFC method has the potential to yield morphology-related “fingerprints” for accurate and label-free classification of the two prostate cell types.

Abstract 3200: Acidic microenvironment activates endoplasmic reticulum stress pathways through GPR4 in human vascular endothelial cells

The tumor microenvironment is characterized by acidosis and hypoxia due to tumor heterogeneity, aerobic glycolysis (“Warburg effect”), and defective vasculature that is inefficient to deliver oxygen and nutrients and to remove metabolic acid byproduct. How the acidic microenvironment affects the function of blood vessels, however, is not well defined. GPR4, a member of the proton-sensing G protein-coupled receptors, has high expression in endothelial cells. We have previously reported that acidosis induces a broad inflammatory response in human vascular endothelial cells through the GPR4 receptor. Acidosis also increases the expression of several endoplasmic reticulum (ER) stress genes such as CHOP and ATF3. In the current study, we have thoroughly examined acidosis/GPR4-induced ER stress pathways in human umbilical vein endothelial cells (HUVEC). All three arms of the ER stress/unfolded protein response (UPR) pathways are activated by acidosis in HUVEC, as we observed an increased expression of phosphorylated eIF2α, phosphorylated IRE1α, and cleaved ATF6 upon acidic pH treatment. In addition, the expression of other downstream mediators of the UPR, such as ATF4, ATF3, CHOP and spliced XBP1, were also induced by acidosis at the mRNA and/or protein levels. Through genetic modifications and a small molecule inhibitor to modulate the expression level or activity of GPR4 in HUVEC, we found that GPR4 plays an important role in mediating the ER stress response induced by acidosis stimulation. As ER stress/UPR can cause inflammation and cell apoptosis, acidosis/GPR4-induced ER stress pathways in endothelial cells may regulate angiogenesis and inflammatory response in the acidic tumor microenvironment.

Citation Format: Lixue Dong, Elizabeth A. Krewson, Li V. Yang. Acidic microenvironment activates endoplasmic reticulum stress pathways through GPR4 in human vascular endothelial cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3200. doi:10.1158/1538-7445.AM2015-3200

GPR4 decreases B16F10 melanoma cell spreading and regulates focal adhesion dynamics through the G13/Rho signaling pathway

The effect of acidosis, a biochemical hallmark of the tumor microenvironment, on cancer progression and metastasis is complex. Both pro- and anti-tumorigenic effects of acidosis have been reported and the acidic microenvironment has been exploited for specific delivery of drugs, imaging agents, and genetic constructs into tumors. In this study we investigate the spreading and focal adhesion of B16F10 melanoma cells that are genetically engineered to overexpress the pH-sensing G protein-coupled receptor GPR4. By using cell attachment assays we found that GPR4 overexpression delayed cell spreading and altered the spatial localization of dynamic focal adhesion complex, such as the localization of phosphorylated focal adhesion kinase (FAK) and paxillin, at acidic pH. The potential G-protein and downstream signaling pathways that are responsible for these effects were also investigated. By using the Rho inhibitor CT04 (C3 transferase), the Rho-associated kinase (ROCK) inhibitors Y27632 and thiazovivin, the myosin light chain kinase (MLCK) inhibitor staurosporine or a G12/13 inhibitory construct, cell spreading was restored whereas the inhibition and activation of the Gq and Gs pathways had little or no effect. Altogether our results indicate that through the G12/13/Rho signaling pathway GPR4 modulates focal adhesion dynamics and reduces cell spreading and membrane ruffling.

Polarization imaging and classification of Jurkat T and Ramos B cells using a flow cytometer

Label-free and rapid classification of cells can have awide range of applications in biology. We report a robust method of polarization diffraction imaging flow cytometry (p-DIFC) for achieving this goal. Coherently scattered light signals are acquired from single cells excited by a polarized laser beam in the form of two cross-polarized diffraction images. Image texture and intensity parameters are extracted with a gray level co-occurrence matrix (GLCM) algorithm to obtain an optimized set of feature parameters as the morphological "fingerprints" for automated cell classification. We selected the Jurkat T cells and Ramos B cells to test the p-DIFC method's capacity for cell classification. After detailed statistical analysis, we found that the optimized feature vectors yield accuracies of classification between the Jurkat and Ramos ranging from 97.8% to 100% among different cell data sets. Confocal imaging and three-dimensional reconstruction were applied to gain insights on the ability of p-DIFC method for classifying the two cell lines of highly similar morphology. Based on these results we conclude that the p-DIFC method has the capacity to discriminate cells of high similarity in their morphology with "fingerprints" features extracted from the diffraction images, which may be attributed to subtle but statistically significant differences in the nucleus-to-cell volume ratio in the case of Jurkat and Ramos cells.

In vitro cell migration and invasion assays

Migration is a key property of live cells and critical for normal development, immune response, and disease processes such as cancer metastasis and inflammation. Methods to examine cell migration are very useful and important for a wide range of biomedical research such as cancer biology, immunology, vascular biology, cell biology and developmental biology. Here we use tumor cell migration and invasion as an example and describe two related assays to illustrate the commonly used, easily accessible methods to measure these processes. The first method is the cell culture wound closure assay in which a scratch is generated on a confluent cell monolayer. The speed of wound closure and cell migration can be quantified by taking snapshot pictures with a regular inverted microscope at several time intervals. More detailed cell migratory behavior can be documented using the time-lapse microscopy system. The second method described in this paper is the transwell cell migration and invasion assay that measures the capacity of cell motility and invasiveness toward a chemo-attractant gradient. It is our goal to describe these methods in a highly accessible manner so that the procedures can be successfully performed in research laboratories even just with basic cell biology setup.

The TMEFF2 tumor suppressor modulates integrin expression, RhoA activation and migration of prostate cancer cells

Cell adhesion and migration play important roles in physiological and pathological states, including embryonic development and cancer invasion and metastasis. The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed mainly in brain and prostate and its expression is deregulated in prostate cancer. We have previously shown that TMEFF2 can function as a tumor suppressor by inhibiting cell migration and invasion of prostate cells. However, the molecular mechanisms involved in this inhibition are not clear. In this study we demonstrate that TMEFF2 affects cell adhesion and migration of prostate cancer cells and that this effect correlates with changes in integrin expression and RhoA activation. Deletion of a 13 basic-rich amino acid region in the cytoplasmic domain of TMEFF2 prevented these effects. Overexpression of TMEFF2 reduced cell attachment and migration on vitronectin and caused a concomitant decrease in RhoA activation, stress fiber formation and expression of αv, β1 and β3 integrin subunits. Conversely, TMEFF2 interference in 22Rv1 prostate cancer cells resulted in an increased integrin expression. Results obtained with a double TRAMP/TMEFF2 transgenic mouse also indicated that TMEFF2 expression reduced integrin expression in the mouse prostate. In summary, the data presented here indicate an important role of TMEFF2 in regulating cell adhesion and migration that involves integrin signaling and is mediated by its cytoplasmic domain.

Acidic tumor microenvironment and pH-sensing G protein-coupled receptors

The tumor microenvironment is acidic due to glycolytic cancer cell metabolism, hypoxia, and deficient blood perfusion. It is proposed that acidosis in the tumor microenvironment is an important stress factor and selection force for cancer cell somatic evolution. Acidic pH has pleiotropic effects on the proliferation, migration, invasion, metastasis, and therapeutic response of cancer cells and the function of immune cells, vascular cells, and other stromal cells. However, the molecular mechanisms by which cancer cells and stromal cells sense and respond to acidic pH in the tumor microenvironment are poorly understood. In this article the role of a family of pH-sensing G protein-coupled receptors (GPCRs) in tumor biology is reviewed. Recent studies show that the pH-sensing GPCRs, including GPR4, GPR65 (TDAG8), GPR68 (OGR1), and GPR132 (G2A), regulate cancer cell metastasis and proliferation, immune cell function, inflammation, and blood vessel formation. Activation of the proton-sensing GPCRs by acidosis transduces multiple downstream G protein signaling pathways. Since GPCRs are major drug targets, small molecule modulators of the pH-sensing GPCRs are being actively developed and evaluated. Research on the pH-sensing GPCRs will continue to provide important insights into the molecular interaction between tumor and its acidic microenvironment and may identify new targets for cancer therapy and chemoprevention.

Analysis of cellular objects through diffraction images acquired by flow cytometry

It was found that the diffraction images acquired along the side scattering directions with objects in a cell sample contain pattern variations at both the global and local scales. We show here that the global pattern variation is associated with the categorical size and morphological heterogeneity of the imaged objects. An automated image processing method has been developed to separate the acquired diffraction images into three types of global patterns. Combined with previously developed method for quantifying local texture pattern variations, the new method allows fully automated analysis of diffraction images for rapid and label-free classification of cells according to their 3D morphology.

Acidosis decreases c-Myc oncogene expression in human lymphoma cells: a role for the proton-sensing G protein-coupled receptor TDAG8

Acidosis is a biochemical hallmark of the tumor microenvironment. Here, we report that acute acidosis decreases c-Myc oncogene expression in U937 human lymphoma cells. The level of c-Myc transcripts, but not mRNA or protein stability, contributes to c-Myc protein reduction under acidosis. The pH-sensing receptor TDAG8 (GPR65) is involved in acidosis-induced c-Myc downregulation. TDAG8 is expressed in U937 lymphoma cells, and the overexpression or knockdown of TDAG8 further decreases or partially rescues c-Myc expression, respectively. Acidic pH alone is insufficient to reduce c-Myc expression, as it does not decrease c-Myc in H1299 lung cancer cells expressing very low levels of pH-sensing G protein-coupled receptors (GPCRs). Instead, c-Myc is slightly increased by acidosis in H1299 cells, but this increase is completely inhibited by ectopic overexpression of TDAG8. Interestingly, TDAG8 expression is decreased by more than 50% in human lymphoma samples in comparison to non-tumorous lymph nodes and spleens, suggesting a potential tumor suppressor function of TDAG8 in lymphoma. Collectively, our results identify a novel mechanism of c-Myc regulation by acidosis in the tumor microenvironment and indicate that modulation of TDAG8 and related pH-sensing receptor pathways may be exploited as a new approach to inhibit Myc expression.

Acidosis activation of the proton-sensing GPR4 receptor stimulates vascular endothelial cell inflammatory responses revealed by transcriptome analysis

Acidic tissue microenvironment commonly exists in inflammatory diseases, tumors, ischemic organs, sickle cell disease, and many other pathological conditions due to hypoxia, glycolytic cell metabolism and deficient blood perfusion. However, the molecular mechanisms by which cells sense and respond to the acidic microenvironment are not well understood. GPR4 is a proton-sensing receptor expressed in endothelial cells and other cell types. The receptor is fully activated by acidic extracellular pH but exhibits lesser activity at the physiological pH 7.4 and minimal activity at more alkaline pH. To delineate the function and signaling pathways of GPR4 activation by acidosis in endothelial cells, we compared the global gene expression of the acidosis response in primary human umbilical vein endothelial cells (HUVEC) with varying level of GPR4. The results demonstrated that acidosis activation of GPR4 in HUVEC substantially increased the expression of a number of inflammatory genes such as chemokines, cytokines, adhesion molecules, NF-κB pathway genes, and prostaglandin-endoperoxidase synthase 2 (PTGS2 or COX-2) and stress response genes such as ATF3 and DDIT3 (CHOP). Similar GPR4-mediated acidosis induction of the inflammatory genes was also noted in other types of endothelial cells including human lung microvascular endothelial cells and pulmonary artery endothelial cells. Further analyses indicated that the NF-κB pathway was important for the acidosis/GPR4-induced inflammatory gene expression. Moreover, acidosis activation of GPR4 increased the adhesion of HUVEC to U937 monocytic cells under a flow condition. Importantly, treatment with a recently identified GPR4 antagonist significantly reduced the acidosis/GPR4-mediated endothelial cell inflammatory response. Taken together, these results show that activation of GPR4 by acidosis stimulates the expression of a wide range of inflammatory genes in endothelial cells. Such inflammatory response can be suppressed by GPR4 small molecule inhibitors and hold potential therapeutic value.

Abstract 2799: Regulation of tumor cell attachment, spreading and migration by the GPR4 receptor and related G protein pathways

The tumor microenvironment has a characteristic low pH due to inadequate blood perfusion, hypoxia, altered cellular metabolism, and inflammation. The effects of acidic pH on cancer progression are complex. It has been shown that low pH increases the metastatic spread of cancer by assisting in the degradation of extracellular matrix. Other studies show that acidic microenvironments decrease metastatic potential in B16F10 melanoma cells upon activation of the GPR4 receptor and also inhibit Akt activity in breast cancer cells. In this study we have investigated the attachment, spreading, and migration of B16F10 cells that have been genetically modified to express the GPR4 receptor at a high level (named B16F10/GPR4 cells). The results showed that upon stimulation of GPR4 in B16F10/GPR4 cells with low pH, cell spreading, membrane ruffling, and migration were significantly decreased. The phosphorylation levels of paxillin Y118 and focal adhesion kinase (FAK) Y397 following one-hour cell attachment were also decreased, and the spatial localization of the phosphorylated paxillin and FAK was substantially altered. Further tests were performed to identify the G-protein signaling pathway responsible for this effect. By using a G13 dominant negative construct or inhibiting Rho activation with C3 transferase (CT04) in B16F10/GPR4 cells, the cell spreading and membrane ruffling abilities were almost completely restored back to the level of B16F10/vector control cells, whereas the inhibition of the Gs and Gq pathways had little effect. These results suggest that activation of the GPR4 receptor and subsequently the G13/Rho downstream pathway are responsible for decreased cell attachment, spreading and membrane ruffling, which may cause decreased metastatic potential of B16F10/GPR4 cells found previously.

Citation Format: Calvin R. Justus, Li V. Yang. Regulation of tumor cell attachment, spreading and migration by the GPR4 receptor and related G protein pathways. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2799. doi:10.1158/1538-7445.AM2013-2799

Comparative study of 3D morphology and functions on genetically engineered mouse melanoma cells

Quantification of 3D morphology and measurement of cellular functions were performed on the mouse melanoma cell lines of B16F10 to investigate the intriguing problem of structure-function relations in the genetically engineered cells with GPR4 overexpression. Results of 3D analysis of cells in suspension and phase contrast imaging of adherent cells yield consistent evidence that stimulation of the proton-sensing GPR4 receptor in these cells may modify significantly their morphology with diminishing ability to produce membrane protrusions and to migrate. Examination of the 3D parameters of mitochondria provide further insights on the measured variation of the maximal capacity of oxygen consumption rate among the genetically modified cells, indicating that the proton-sensing receptor may regulate cancer cell metabolism with increased mitochondrial surface area. Our study demonstrates clearly the significant benefits of quantitative 3D morphological study in illuminating cellular functions and development of novel morphology based cell assay methods.

Activation of GPR4 by acidosis increases endothelial cell adhesion through the cAMP/Epac pathway

Endothelium-leukocyte interaction is critical for inflammatory responses. Whereas the tissue microenvironments are often acidic at inflammatory sites, the mechanisms by which cells respond to acidosis are not well understood. Using molecular, cellular and biochemical approaches, we demonstrate that activation of GPR4, a proton-sensing G protein-coupled receptor, by isocapnic acidosis increases the adhesiveness of human umbilical vein endothelial cells (HUVECs) that express GPR4 endogenously. Acidosis in combination with GPR4 overexpression further augments HUVEC adhesion with U937 monocytes. In contrast, overexpression of a G protein signaling-defective DRY motif mutant (R115A) of GPR4 does not elicit any increase of HUVEC adhesion, indicating the requirement of G protein signaling. Downregulation of GPR4 expression by RNA interference reduces the acidosis-induced HUVEC adhesion. To delineate downstream pathways, we show that inhibition of adenylate cyclase by inhibitors, 2',5'-dideoxyadenosine (DDA) or SQ 22536, attenuates acidosis/GPR4-induced HUVEC adhesion. Consistently, treatment with a cAMP analog or a G(i) signaling inhibitor increases HUVEC adhesiveness, suggesting a role of the G(s)/cAMP signaling in this process. We further show that the cAMP downstream effector Epac is important for acidosis/GPR4-induced cell adhesion. Moreover, activation of GPR4 by acidosis increases the expression of vascular adhesion molecules E-selectin, VCAM-1 and ICAM-1, which are functionally involved in acidosis/GPR4-mediated HUVEC adhesion. Similarly, hypercapnic acidosis can also activate GPR4 to stimulate HUVEC adhesion molecule expression and adhesiveness. These results suggest that acidosis/GPR4 signaling regulates endothelial cell adhesion mainly through the G(s)/cAMP/Epac pathway and may play a role in the inflammatory response of vascular endothelial cells.

Inhibition of tumor cell migration and metastasis by the proton-sensing GPR4 receptor

GPR4 is a member of the proton-sensing G protein-coupled receptor family. Within tumor microenvironments, the interstitial acidic pH may activate GPR4 to regulate the behavior of tumor cells. Mouse B16F10 melanoma cells and TRAMP-C1 prostate cancer cells, genetically engineered to overexpress GPR4 or the control vector, were subject to a series of cell migration, invasion and metastasis assays. Upon GPR4 overexpression and activation in an acidic pH, the migration of B16F10 and TRAMP-C1 cells was substantially inhibited in comparison to the vector control. Similar results were observed in the Matrigel invasion and transendothelial invasion assays. At the molecular level, stimulation of GPR4 by acidosis induced the activation of RhoA and the formation of actin stress fibers. In addition, treating B16F10 cells with the known Rho activator CN01 (calpeptin) strongly inhibited cell migration, recapitulating the acidosis/GPR4-induced motility inhibition phenotype. To examine the biological effects in vivo, B16F10 melanoma cells were intravenously injected into syngeneic C57BL/6 mice and pulmonary metastasis was inhibited by approximately 80% in GPR4-overexpressing B16F10 cells in comparison to the vector control. Upon treatment with the Rho activator CN01, the phenotype of the B16F10 vector cells paralleled that of the GPR4-overexpressing cells in cell migration and metastasis assays. These findings suggest that GPR4 activation by an acidic pH inhibits tumor cell migration and invasion, and the Rho GTPase is at least partly responsible for this phenotype.

Label-free classification of cultured cells through diffraction imaging

Automated classification of biological cells according to their 3D morphology is highly desired in a flow cytometer setting. We have investigated this possibility experimentally and numerically using a diffraction imaging approach. A fast image analysis software based on the gray level co-occurrence matrix (GLCM) algorithm has been developed to extract feature parameters from measured diffraction images. The results of GLCM analysis and subsequent classification demonstrate the potential for rapid classification among six types of cultured cells. Combined with numerical results we show that the method of diffraction imaging flow cytometry has the capacity as a platform for high-throughput and label-free classification of biological cells.

Abstract 1518: Gene expression profiling reveals acidosis/GPR4-induced inflammatory responses in vascular endothelial cells

Due to deficient blood perfusion, hypoxia, and glycolytic metabolism, acidic tissue microenvironments commonly exist in solid tumors, inflammation, and many other pathological conditions. However, the molecular mechanisms by which cells respond to acidic microenvironments are not well understood. GPR4 has recently been identified as a novel proton-sensing receptor expressed in endothelial cells, cancer cells, and other cell types. GPR4 is activated by acidic extracellular pH but has lower activation at the physiological pH 7.4 and minimal activation at more alkaline pH. To delineate the function and signaling pathways of GPR4 in endothelial cells under acidic conditions, we performed gene expression microarray analyses. Primary human umbilical vein endothelial cells (HUVEC) that express endogenous GPR4 were stably transduced with the MSCV-IRES-GFP control vector (designated as HUVEC/Vector cells) or the MSCV-GPR4-IRES-GFP construct (designated as HUVEC/GPR4 cells). HUVEC/Vector and HUVEC/GPR4 cells were treated with pH 6.4 (400 nM H+) for 5 hours to activate GPR4 or with pH 8.4 (4 nM H+) as a negative control. RNAs were isolated, labeled, and hybridized with the Agilent Whole Genome Microarray Chip to compare gene expression. The results demonstrated that the acidic pH treatment of HUVEC/Vector cells stimulated the expression of a number of inflammatory genes, which represent a predominant signature in the microarray dataset. The induction of most of the acid-responsive inflammatory genes were further enhanced by GPR4 overexpression in HUVEC/GPR4 cells at pH 6.4, suggesting these genes are responsive to varying levels of GPR4 signaling. The inflammatory genes with substantial up-regulation by acidosis/GPR4 include chemokines, cytokines, adhesion molecules, genes involved in the TNFα and NF-κB pathways, prostaglandin-endoperoxidase synthase, and EGR transcription factors. The up-regulation of the genes at pH 6.4, compared to pH 7.4 and pH 8.4, was further confirmed by real-time RT-PCR. Taken together, our results show that activation of GPR4 by acidosis stimulates the expression of a wide range of inflammatory genes in endothelial cells. Since the inflammatory response of endothelial cells is important for blood vessels to interact with immune cells and tumor cells in the microenvironment, the acidosis/GPR4 signaling may play a role in the processes such as tumor immunity and metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1518. doi:10.1158/1538-7445.AM2011-1518

Deletion of the pH sensor GPR4 decreases renal acid excretion

Proton receptors are G protein-coupled receptors that accept protons as ligands and function as pH sensors. One of the proton receptors, GPR4, is relatively abundant in the kidney, but its potential role in acid-base homeostasis is unknown. In this study, we examined the distribution of GPR4 in the kidney, its function in kidney epithelial cells, and the effects of its deletion on acid-base homeostasis. We observed GPR4 expression in the kidney cortex, in the outer and inner medulla, in isolated kidney collecting ducts, and in cultured outer and inner medullary collecting duct cells (mOMCD1 and mIMCD3). Cultured mOMCD1 cells exhibited pH-dependent accumulation of intracellular cAMP, characteristic of GPR4 activation; GPR4 knockdown attenuated this accumulation. In vivo, deletion of GPR4 decreased net acid secretion by the kidney and resulted in a nongap metabolic acidosis, indicating that GPR4 is required to maintain acid-base homeostasis. Collectively, these findings suggest that GPR4 is a pH sensor with an important role in regulating acid secretion in the kidney collecting duct.

Abstract 5278: Inhibition of tumor cell migration and metastasis by the GPR4 receptor

GPR4, a G protein-coupled receptor, has been shown to function as a proton sensor. Within tumor microenvironments, the interstitial acidic pH may activate GPR4 to regulate the behavior of tumor cells, blood vessels, and other cells. The expression of GPR4 is detected in some tumor cells, and it is the focus of this study to investigate the effects of acidosis/GPR4 signaling on tumor cell migration and metastasis. B16F10 melanoma cells and TRAMP-C1 prostate cancer cells, genetically engineered to overexpress GPR4 or the control vector, were subject to a series of cell motility assays. Transwell and wound closure assays were performed to examine cell migration, and it was observed that upon GPR4 activation in an acidic pH, cell migration was inhibited two to four fold in comparison to the vector control. These same trends were observed for invasion assays, in which Matrigel or a HUVEC endothelial monolayer was applied to the top of each transwell filter. To elucidate the molecular mechanism by which acidosis/GPR4 mediated motility inhibition occurs, G-LISA RhoA activation assays were used and it was observed that upon GPR4 activation in an acidic environment, the levels of activated RhoA, when compared to the vector control, were increased two and three fold. Furthermore, activation of Rho by its activator CN01 in B16F10 and TRAMP-C1 tumor cells recapitulated the acidosis/GPR4 induced motility inhibition phenotype, while inhibition of Rho reversed such phenotype. To examine the biological effects in vivo, B16F10 cells were injected into C57BL/6 female mice through tail veins. Pulmonary melanoma metastasis was inhibited by greater than 80% in GPR4 overexpressing B16F10 cells in comparison to the vector control. Upon treatment with the Rho activator CN01 in culture, the phenotype of the B16F10 vector cells paralleled that of the GPR4 overexpressing cells as metastasis was inhibited by more than 90%. These findings suggest that GPR4 activation by acidic pH plays a role in the inhibition of migration and invasion in B16F10 and TRAMP-C1 tumor cells, and the activation of Rho is at least partly responsible for this phenotype on the molecular level.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5278.