Identification of new microtubule small-molecule inhibitors and microtubule-associated genes against triple negative breast cancer

Breast cancer represents the leading cancer type and leading cause of cancer-related death among women in the world. Triple-negative breast cancer (TNBC) is a subset of breast cancer with the poorest prognosis and still lacking of effective therapeutic options. We recently screened a natural product library and identified 3 new hit compounds with selective and prominent anti-TNBC activities on different subtype of TNBC cell lines. Interestingly, all of these 3 hit compounds belong to "cytoskeletal drugs" that target tubulin and microtubule function. Our data also showed that these hit compounds showed consistently effective on TNBC cells which are resistant to those currently used antimicrotubule agents such as Paclitaxel. RNA-Sequencing analyses revealed the anti-TNBC mechanisms of these hit compounds and identified a subset of new cellular factors commonly affected by hit compounds in different subtypes of TNBC cells. Among them, we demonstrated AHCYL1 and SPG21 as new microtubule-associated proteins, which were required for TNBC cell survival with clinical implication through tissue array analysis. Our studies provide new insights into the mechanisms of TNBC pathogenesis and offer promising therapeutic directions for this aggressive breast cancer.

Partnership in Cancer Research (PCAR) Program Increases Medical Student Knowledge and Confidence to Perform Cancer Research

Arkansas has a high cancer burden, and a pressing need exists for more medical students to pursue oncology as a career. The Partnership in Cancer Research (PCAR) program provides a summer research experience at the University of Arkansas for Medical Sciences for 12 medical students who have completed their first year of medical training. A majority of participants spend time pursuing cancer research in basic science, clinical, or community-based research. Students report on their research progress in an interactive "Live from the Lab!" series and assemble a final poster presentation describing their findings. Other activities include participation in a moderated, cancer-patient support group online, lecture series on cancer topics, medical simulations, palliative care clinic visit, "Death Over Dinner" event, and an entrepreneurship competition. Students completed surveys over PCAR's first 2 years in operation to evaluate all aspects of the program. Surveys reveal that students enthusiastically embraced the program in its entirety. This was especially true of the medical simulations which received the highest evaluations. Most significantly, surveys revealed that the program increased cancer knowledge and participant confidence to perform cancer research.

The Tumor Microenvironment and Immune Response in Breast Cancer

The complex interactions between cancer cells and their surrounding microenvironment are fundamental in determining tumor progression, response to therapy, and, ultimately, patient prognosis [...].

Characterization of Morreton virus as an oncolytic virotherapy platform for liver cancers

BACKGROUND

Morreton virus (MORV) is an oncolytic Vesiculovirus , genetically distinct from vesicular stomatitis virus (VSV).

AIM

To report that MORV induced potent cytopathic effects (CPEs) in cholangiocarcinoma (CCA) and hepatocellular carcinoma (HCC) in vitro models.

APPROACH AND RESULTS

In preliminary safety analyses, high intranasal doses (up to 10 10 50% tissue culture infectious dose [TCID 50 ]) of MORV were not associated with significant adverse effects in immune competent, non-tumor-bearing mice. MORV was shown to be efficacious in a Hep3B hepatocellular cancer xenograft model but not in a CCA xenograft HuCCT1 model. In an immune competent, syngeneic murine CCA model, single intratumoral treatments with MORV (1 × 10 7 TCID 50 ) triggered a robust antitumor immune response leading to substantial tumor regression and disease control at a dose 10-fold lower than VSV (1 × 10 8 TCID 50 ). MORV led to increased CD8 + cytotoxic T cells without compensatory increases in tumor-associated macrophages and granulocytic or monocytic myeloid-derived suppressor cells.

CONCLUSIONS

Our findings indicate that wild-type MORV is safe and can induce potent tumor regression via immune-mediated and immune-independent mechanisms in HCC and CCA animal models without dose limiting adverse events. These data warrant further development and clinical translation of MORV as an oncolytic virotherapy platform.

Echinomycin as a promising therapeutic agent against KSHV-related malignancies

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), which preferentially arise in immunocompromised patients while lack of effective therapeutic options. Oncoproteins Myc and hypoxia-inducible factor-1α (HIF1α) have been found closely related to KSHV infection, replication and oncogenesis. However, the strategies of dual targeting these two oncoproteins have never been developed and tested for treatments of KSHV-related malignancies. In the current study, we report that treatment of echinomycin dramatically regresses cell growth both in vitro-cultured KSHV + tumor cells and in vivo KS or PEL xenograft mice models, through simultaneously inhibiting Myc and HIF1α expression. Echinomycin treatment also induces viral lytic gene expression whereas not increasing infectious virions production from KSHV + tumor cells. Our comparative transcriptomic analysis has identified a bunch of new Echinomycin-regulated, Myc- and HIF1α-related genes contributed to KSHV pathogenesis, including KDM4B and Tau, which are required for the survival of KSHV + tumor cells with functional validation. These data together reveal that dual targeting Myc and HIF1α such as using Echinomycin may represent a new and promising option for treatments of these virus-associated malignancies.

Role of Histamine and Related Signaling in Kaposi's Sarcoma-Associated Herpesvirus Pathogenesis and Oncogenesis

Although Kaposi's sarcoma-associated herpesvirus (KSHV) has been reported to cause several human cancers including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), the mechanisms of KSHV-induced tumorigenesis, especially virus-host interaction network, are still not completely understood, which therefore hinders the development of effective therapies. Histamine, together with its receptors, plays an important role in various allergic diseases by regulating different inflammation and immune responses. Our previous data showed that antagonists targeting histamine receptors effectively repressed KSHV lytic replication. In the current study, we determined that histamine treatment increased cell proliferation and anchorage-independent growth abilities of KSHV-infected cells. Furthermore, histamine treatment affected the expression of some inflammatory factors from KSHV-infected cells. For clinical relevance, several histamine receptors were highly expressed in AIDS-KS tissues when compared to normal skin tissues. We determined that histamine treatment promoted KSHV-infected lymphoma progression in immunocompromised mice models. Therefore, besides viral replication, our data indicate that the histamine and related signaling are also involved in other functions of KSHV pathogenesis and oncogenesis.

Activation of IL1 signaling molecules by Kaposi's sarcoma-associated herpesvirus

Objective

Kaposi's Sarcoma-associated Herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi's sarcoma (KS) and Primary effusion lymphoma (PEL), which are usually seen in immunocompromised patients while lack of effective therapeutic options. Interleukin1 (IL1) family is a major mediator for inflammation response and has functional role in both innate and adaptive immunity. In contrast to the well-studied IL1 molecules, the activation and functional role of IL1 receptor/co-receptor and other related ligands, such as the IL1 receptor accessory protein (IL1RAP), in KSHV pathogenesis and tumorigenesis remain almost unknown.

Methods

In the current study, a series of KSHV negative and positive primary or tumor cells, as well as AIDS-KS tumor samples from cohort HIV+ patients were used to compare and determine the activation status of IL1 signaling molecules, and their functional roles in KSHV pathogenesis.

Results

We reported the high activation of multiple IL1 signaling molecules, including IL1, IL36, IL1R1, IL1RAP and IRAKs, during KSHV latent and lytic stages, as well as in clinical samples from patients with KSHV-related malignancies. Directly targeting these molecules especially IL1R1 and IL1RAP significantly impaired the survival and growth of KSHV+ tumor cells, as well as their colony formation on 3-D culture.

Conclusion

Our data indicate the importance of IL1 signaling molecules in KSHV pathogenesis and tumorigenesis, which may represent attractive therapeutic targets against these virus-associated diseases.

Repurposing live attenuated trivalent MMR vaccine as cost-effective cancer immunotherapy

It has long been known that oncolytic viruses wield their therapeutic capability by priming an inflammatory state within the tumor and activating the tumor immune microenvironment, resulting in a multifaceted antitumor immune response. Vaccine-derived viruses, such as measles and mumps, have demonstrated promising potential for treating human cancer in animal models and clinical trials. However, the extensive cost of manufacturing current oncolytic viral products makes them far out of reach for most patients. Here by analyzing the impact of intratumoral (IT) administrations of the trivalent live attenuated measles, mumps, and rubella viruses (MMR) vaccine, we unveil the cellular and molecular basis of MMR-induced anti-cancer activity. Strikingly, we found that IT delivery of low doses of MMR correlates with tumor control and improved survival in murine hepatocellular cancer and colorectal cancer models via increased tumor infiltration of CD8+ granzyme B+ T-cells and decreased macrophages. Moreover, our data indicate that MMR activates key cellular effectors of the host’s innate and adaptive antitumor immunity, culminating in an immunologically coordinated cancer cell death. These findings warrant further work on the potential for MMR to be repurposed as safe and cost-effective cancer immunotherapy to impact cancer patients globally.

SARS-CoV-2 infection and lytic reactivation of herpesviruses: A potential threat in the postpandemic era?

The outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative pathogen for the coronavirus disease 2019 (COVID-19) pandemic, has greatly stressed our healthcare system. In addition to severe respiratory and systematic symptoms, several comorbidities increase the risk of fatal disease outcomes, including chronic viral infections. Increasing cases of lytic reactivation of human herpesviruses in COVID-19 patients and vaccinated people have been reported recently. SARS-CoV2 coinfection, COVID-19 treatments, and vaccination may aggravate those herpesvirus-associated diseases by reactivating the viruses in latently infected host cells. In this review, we summarize recent clinical findings and limited mechanistic studies regarding the relationship between SARS-CoV-2 and different human herpesviruses that suggest an ongoing potential threat to human health in the postpandemic era.

Oral Shedding of an Oncogenic Virus Alters the Oral Microbiome in HIV+ Patients

Kaposi's Sarcoma (KS) caused by Kaposi's sarcoma-associated herpesvirus (KSHV) continues to be the most common AIDS-associated tumor. Involvement of the oral cavity represents one of the most common clinical manifestations of this tumor. Numerous types of cancer are associated with the alterations of in components of the microbiome. However, little is known about how KSHV coinfection affects the oral microbiome in HIV+ patients, especially in a "pre-cancer" niche. Using 16S rRNA pyrosequencing, we found that oral shedding of KSHV correlated with altered oral microbiome signatures in HIV+ patients, including a reduction in the microbiota diversity, changing the relative composition of specific phyla and species, and regulating microbial functions. Furthermore, we found that Streptococcus sp., one of the most increased species in the oral cavity of HIV+/KSHV+ patients, induced KSHV lytic reactivation in primary oral cells. Together, these data indicate that oral shedding of KSHV may manipulate the oral microbiome to promote viral pathogenesis and tumorigenesis especially in immunocompromised patients.

The potential impacts of early secreted antigenic target of 6 kDa of Mycobacterium tuberculosis on KSHV-infected cells

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several human cancers, including Kaposi's sarcoma (KS) and primary effusion lymphoma, which are mostly seen in immunocompromised patients, such as human immunodefeciency virus (HIV)+ individuals. Tuberculosis (TB), caused by the bacterial pathogen Mycobacterium tuberculosis (Mtb), remains one of the deadliest infectious diseases in the world. The risk of developing TB is dramatically higher in people living with HIV than among those without HIV infection. Case reports link cutaneous or pulmonary KS in HIV+ patients with mycobacterial co-infections, however, impacts of Mtb infection or its products on KSHV-infected cells are not known. We report here that ESAT-6, a secreted Mtb virulence factor, induces viral reactivation from KSHV-infected cells. KSHV-infected pulmonary endothelial cells were resistant to ESAT-6 induced inhibition of cell growth. Our data demonstrate that Mtb virulence factors influence the biology of KSHV-infected cells, highlighting the need to study the interactions between these two pathogens commonly found in people living with HIV.

Role of EIF4G1 network in non-small cell lung cancers (NSCLC) cell survival and disease progression

Although the Eukaryotic Translation Initiation Factor 4 Gamma 1 (EIF4G1) has been found overexpressed in a variety of cancers, its role in non–small cell lung cancers (NSCLC) pathogenesis especially in immunoregulatory functions, its clinical relevance and therapeutic potential remain largely unknown. By using cancer patients tissue assays, the results indicate that EIF4G1 expressional levels are much higher in NSCLC tissues than in adjacent or normal lung tissues, which are also associated with NSCLC patient survival. By using an RNA‐Sequencing based pipeline, the data show that EIF4G1 has a significant association with immune checkpoint molecules such as PD‐1/PD‐L1 in NSCLC. EIF4G1 small‐molecule inhibitors effectively repress NSCLC growth in cell culture and xenograft animal models. Protein array results identify the signature of proteins controlled by EIF4G1 in NSCLC cells, in which new candidates such as MUC1 and NRG1 are required for NSCLC survival and tumorigenesis with clinical relevance. Taken together, these results have for the first time demonstrated the immunoregulatory functions, clinical relevance and therapeutic potential of the EIF4G1 network in NSCLC, which may represent a promising and novel target to improve lung cancer treatment.

Kaposi Sarcoma-Associated Herpesvirus and Staphylococcus aureus Coinfection in Oral Cavities of HIV-Positive Patients: A Unique Niche for Oncogenic Virus Lytic Reactivation

Collectively, viruses are the principal cause of cancers arising in patients with immune dysfunction, including human immunodeficiency virus (HIV)-positive patients. Kaposi sarcoma (KS) etiologically linked to Kaposi sarcoma-associated herpesvirus (KSHV) continues to be the most common AIDS-associated tumor. The involvement of the oral cavity represents one of the most common clinical manifestations of this tumor. HIV infection incurs an increased risk among individuals with periodontal diseases and oral carriage of a variety of pathogenic bacteria. However, whether interactions involving periodontal bacteria and oncogenic viruses in the local environment facilitate replication or maintenance of these viruses in the oral cavity of HIV-positive patients remain largely unknown. We previously showed that pathogen-associated molecular patterns (PAMPs) from specific periodontal bacteria promoted KSHV entry into oral cells and subsequent establishment of latency. In the current study, we demonstrate that Staphylococcus aureus, one of common pathogens causing infection in HIV-positive patients, and its PAMPs can effectively induce KSHV lytic reactivation from infected oral cells, through the Toll-like receptor reactive oxygen species and cyclin D1-Dicer-viral microRNA axis. This investigation provides further clinical evidence about the relevance of coinfection due to these 2 pathogens in the oral cavities of a cohort HIV-positive patients and reveals novel mechanisms through which these coinfecting pathogens potentially promote virus-associated cancer development in the unique niche of immunocompromised patients.

Porphyromonas gingivalis coinfects with KSHV in oral cavities of HIV+ patients and induces viral lytic reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) infection causes several human cancers, including Kaposi's sarcoma (KS), one of the most common AIDS-associated tumors. The involvement of the oral cavity represents one common clinical manifestation of AIDS-KS individuals with periodontal diseases and an oral carriage of a variety of pathogenic bacteria, including Porphyromonas gingivalis. In the current study, we report the clinical relevance of P. gingivalis and KSHV coinfection in the oral cavity of a cohort of HIV+ patients. Furthermore, we found that P. gingivalis conditioned medium or derived lipopolysaccharide effectively induced KSHV lytic reactivation from infected oral cells. This reactivation requires TLR4 as well as the activities of p38 and Jun N-terminal kinase- mitogen-activated protein kinase signaling pathways. Our findings reveal the mechanisms through which coinfected periodontal pathogens potentially promote oncogenic virus pathogenesis in the unique niche of immunocompromised patients.

Developing new ceramide analogs and identifying novel sphingolipid-controlled genes against a virus-associated lymphoma

Primary effusion lymphoma (PEL) is an aggressive malignancy with poor prognosis even under chemotherapy. Kaposi sarcoma-associated herpesvirus (KSHV), one of the human oncogenic viruses, is the principal causative agent. Currently, there is no specific treatment for PEL; therefore, developing new therapies is of great importance. Sphingolipid metabolism plays an important role in determining the fate of tumor cells. Our previous studies have demonstrated that there is a correlation between sphingolipid metabolism and KSHV+ tumor cell survival. To further develop sphingolipid metabolism-targeted therapy, after screening a series of newly synthesized ceramide analogs, here, we have identified compounds with effective anti-PEL activity. These compounds induce significant PEL apoptosis, cell-cycle arrest, and intracellular ceramide production through regulation of ceramide synthesizing or ceramide metabolizing enzymes and dramatically suppress tumor progression without visible toxicity in vivo. These new compounds also increase viral lytic gene expression in PEL cells. Our comparative transcriptomic analysis revealed their mechanisms of action for inducing PEL cell death and identified a subset of novel cellular genes, including AURKA and CDCA3, controlled by sphingolipid metabolism, and required for PEL survival with functional validation. These data provide the framework for the development of promising sphingolipid-based therapies against this virus-associated malignancy.

SARS-CoV-2 proteins and anti-COVID-19 drugs induce lytic reactivation of an oncogenic virus

An outbreak of the novel coronavirus SARS-CoV-2, the causative agent of Coronavirus Disease-2019 (COVID-19), a respiratory disease, has infected over 34,000,000 people since the end of 2019, killed over 1,000,000, and caused worldwide social and economic disruption. Due to the mechanisms of SARS-CoV-2 infection to host cells and its pathogenesis remain largely unclear, there are currently no antiviral drugs with proven efficacy nor are there vaccines for its prevention. Besides severe respiratory and systematic symptoms, several comorbidities may also increase risk of fatal disease outcome. Therefore, it is required to investigate the impacts of COVID-19 on pre-existing diseases of patients, such as cancer and other infectious diseases. In the current study, we have reported that SARS-CoV-2 encoded proteins and some anti-COVID-19 drugs currently used are able to induce lytic reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV), one of major human oncogenic viruses through manipulation of intracellular signaling pathways. Our data indicate that those KSHV+ patients especially in endemic areas exposure to COVID-19 or undergoing the treatment may have increased risks to develop virus-associated cancers, even after they have fully recovered from COVID-19.

Identification of new antiviral agents against Kaposi's sarcoma-associated herpesvirus (KSHV) by high-throughput drug screening reveals the role of histamine-related signaling in promoting viral lytic reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several human cancers, such as Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). Current treatment options for KSHV infection and virus associated diseases are sometimes ineffective, therefore, more effectively antiviral agents are urgently needed. As a herpesvirus, lytic replication is critical for KSHV pathogenesis and oncogenesis. In this study, we have established a high-throughput screening assay by using an inducible KSHV+ cell-line, iSLK.219. After screening a compound library that consisted of 1280 Food and Drug Administration (FDA)-approved drugs, 15 hit compounds that effectively inhibited KSHV virion production were identified, most of which have never been reported with anti-KSHV activities. Interestingly, 3 of these drugs target histamine receptors or signaling. Our data further confirmed that antagonists targeting different histamine receptors (HxRs) displayed excellent inhibitory effects on KSHV lytic replication from induced iSLK.219 or BCBL-1 cells. In contrast, histamine and specific agonists of HxRs promoted viral lytic replication from induced iSLK.219 or KSHV-infected primary cells. Mechanistic studies indicated that downstream MAPK and PI3K/Akt signaling pathways were required for histamine/receptors mediated promotion of KSHV lytic replication. Direct knockdown of HxRs in iSLK.219 cells effectively blocked viral lytic gene expression during induction. Using samples from a cohort of HIV+ patients, we found that the KSHV+ group has much higher levels of histamine in their plasma and saliva than the KSHV- group. Taken together, our data have identified new anti-KSHV agents and provided novel insights into the molecular bases of host factors that contribute to lytic replication and reactivation of this oncogenic herpesvirus.

Identification of a novel monocytic phenotype in Classic Hodgkin Lymphoma tumor microenvironment

Classic Hodgkin lymphoma (CHL) characteristically shows few malignant cells in a microenvironment comprised of mixed inflammatory cells. Although CHL is associated with a high cure rate, recent studies have associated poor prognosis with absolute monocyte count in peripheral blood and increased monocyte/macrophages in involved lymph nodes. Thus, the role of monocytic infiltration and macrophage differentiation in the tumor microenvironment of CHL may be more relevant than absolute macrophage numbers to defining prognosis in CHL patients and potentially have therapeutic implications. Most studies identify tumor-associated macrophages (TAMs) using markers (e.g., CD68) expressed by macrophages and other mononuclear phagocytes, such as monocytes. In contrast, Class A Scavenger Receptor (SR-A/CD204) is expressed by tissue macrophages but not monocytic precursors. In this study, we examined SR-A expression in CHL (n = 43), and compared its expression with that of other macrophage markers. We confirmed a high prevalence of mononuclear cells that stained with CD68, CD163, and CD14 in CHL lymph nodes. However, SR-A protein expression determined by immunohistochemistry was limited to macrophages localized in sclerotic bands characteristic of nodular sclerosis CHL. In contrast, SR-A protein was readily detectable in lymph nodes with metastatic tumor, extra-nodal CHL, T cell/histiocyte-rich large B cell lymphoma, and resident macrophages in non-malignant tissues, including spleen, lymph node, liver and lung. The results of SR-A protein expression paralleled the expression of SR-A mRNA determined by quantitative RT-PCR. These data provide evidence that tumor-infiltrating monocyte/macrophages in CHL have a unique phenotype that likely depends on the microenvironment of nodal CHL.

ABO blood group is a determinant of von Willebrand factor protein levels in human pulmonary endothelial cells

ABO blood group antigens are expressed on von Willebrand factor (VWF) and glycosylation patterns influence circulating VWF levels. The aim of this study was to examine the effect of ABO blood type on tissue-associated VWF protein levels. We selected 35 formalin-fixed paraffin-embedded pulmonary tissue blocks obtained at autopsy from decedents who died from pulmonary embolism with known ABO blood groups (O, A, B and AB phenotypes), prepared tissue microarrays (TMAs) and stained TMAs with antibodies to VWF and platelet/endothelial cell adhesion marker-1 (PECAM-1) as a marker of endothelial cells. A pixel count scoring algorithm was used to quantify VWF and PECAM-1 staining intensity in pulmonary arterioles in digitised images. Compared with type O, non-O individuals have a significantly higher amount of endothelial cell-associated VWF protein expression. VWF protein levels associated with pulmonary vascular endothelial cells is influenced by ABO antigenic determinants.

Expression of PD-1 and PD-Ls in Kaposi's sarcoma and regulation by oncogenic herpesvirus lytic reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several cancers such as Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). PD-1/PD-Ls immune checkpoint molecules play important roles in cancer cell immune escape. The expression of PD-1/PD-Ls and their regulation by oncogenic viruses, in particular KSHV, remain largely undefined. Here we demonstrate strong PD-1/PD-L1/PD-L2 expression in KS tissues from a cohort of HIV + patients. We found that induction of KSHV lytic reactivation significantly upregulates PD-L1 expression on infected tumor cells, potentially through several major cellular signaling pathways and IL-1β, which may represent a novel mechanism for virus-associated tumor cell immune escape.

Flower isoforms promote competitive growth in cancer

In humans, the adaptive immune system uses the exchange of information between cells to detect and eliminate foreign or damaged cells; however, the removal of unwanted cells does not always require an adaptive immune system^1,2. For example, cell selection in Drosophila uses a cell selection mechanism based on 'fitness fingerprints', which allow it to delay ageing³, prevent developmental malformations^3,4 and replace old tissues during regeneration⁵. At the molecular level, these fitness fingerprints consist of combinations of Flower membrane proteins^3,4,6. Proteins that indicate reduced fitness are called Flower-Lose, because they are expressed in cells marked to be eliminated⁶. However, the presence of Flower-Lose isoforms at a cell's membrane does not always lead to elimination, because if neighbouring cells have similar levels of Lose proteins, the cell will not be killed^4,6,7. Humans could benefit from the capability to recognize unfit cells, because accumulation of damaged but viable cells during development and ageing causes organ dysfunction and disease^8-17. However, in Drosophila this mechanism is hijacked by premalignant cells to gain a competitive growth advantage¹⁸. This would be undesirable for humans because it might make tumours more aggressive^19-21. It is unknown whether a similar mechanism of cell-fitness comparison is present in humans. Here we show that two human Flower isoforms (hFWE1 and hFWE3) behave as Flower-Lose proteins, whereas the other two isoforms (hFWE2 and hFWE4) behave as Flower-Win proteins. The latter give cells a competitive advantage over cells expressing Lose isoforms, but Lose-expressing cells are not eliminated if their neighbours express similar levels of Lose isoforms; these proteins therefore act as fitness fingerprints. Moreover, human cancer cells show increased Win isoform expression and proliferate in the presence of Lose-expressing stroma, which confers a competitive growth advantage on the cancer cells. Inhibition of the expression of Flower proteins reduces tumour growth and metastasis, and induces sensitivity to chemotherapy. Our results show that ancient mechanisms of cell recognition and selection are active in humans and affect oncogenic growth.

Development of an unbiased, semi-automated approach for classifying plasma cell immunophenotype following multicolor flow cytometry of bone marrow aspirates

BACKGROUND

Despite increased usage of multiparameter flow cytometry (MFC) to assess diagnosis, prognosis, and therapeutic efficacy (minimal residual disease, MRD) in plasma cell neoplasms (PCNs), standardization of methodology and data analysis is suboptimal. We investigated the utility of using the mean and median fluorescence intensities (FI) obtained from MFC to objectively describe parameters that distinguish plasma cell (PC) phenotypes.

METHODS

In this retrospective study, flow cytometry results from bone marrow aspirate specimens from 570 patients referred to the Myeloma Institute at UAMS were evaluated. Mean and median FI data were obtained from 8-color MFC of non-neoplastic, malignant, and mixed PC populations using antibodies to CD38, CD138, CD19, CD20, CD27, CD45, CD56, and CD81.

RESULTS

Of 570 cases, 252 cases showed only non-neoplastic PCs, 168 showed only malignant PCs, and 150 showed mixed PC populations. Statistical analysis of median FI data for each CD marker showed no difference in expression intensity on non-neoplastic and malignant PCs, between pure and mixed PC populations. ROC analysis of the median FI of CD expression in non-neoplastic and malignant PCs was used to develop an algorithm to convert quantitative FI values to qualitative assessments including "negative," "positive," "dim," and "heterogeneous" expression.

CONCLUSIONS

FI data derived from 8-color MFC can be used to define marker expression on PCs. Translation of FI data from Infinicyt software to an Excel worksheet streamlines workflow and eliminates transcriptional errors when generating flow reports. © 2018 International Clinical Cytometry Society.

Vulvar squamous cell carcinoma aggressiveness is associated with differential expression of collagen and STAT1

Background

Vulvar squamous cell carcinoma (vSCC) is a rare but debilitating disease. One vSCC variant comprises tumor cells that grow and expand as a cohesive sheet of cells that “pushes” and compresses the associated lymphoplasmacytic (LPC) stroma. Another vSCC variant features tumor cells that grow in loose association with one another and infiltrate the associated fibromyxoid (FMX) stroma consisting mainly of extracellular matrix. Clinically, infiltrative vSCC with FMX stroma (Inf/FMX) is significantly associated with lymph node metastases and recurrence.

Methods

An unbiased proteomic approach was used to identify pathways involved in the development of the different vSCC variants. Proteins extracted from formalin-fixed and paraffin-embedded tissues of 10 cases of pushing vSCC with LPC stroma (Push/LPC) and eight cases of Inf/FMX were subjected to liquid chromatography-tandem mass spectrometry (LC–MS/MS).

Results

Analysis identified 2265 different proteins in the 18 samples of vSCC. Of these, 282 proteins were differentially expressed between vSCC variants. Of these, 45 were higher and 237 lower in Inf/FMX compared to Push/LPC tumors. Consistent with the desmoplastic morphology and increased picrosirius red staining, expression of subunits of several collagens (Col 1, 3, 6, 14) was higher in the more aggressive Inf/FMX tumors. In contrast, signal transducer and activator of transcription 1 (STAT1), an important regulator of several inflammatory pathways, was expressed at lower levels in the Inf/FMX tumors. This finding was confirmed by immunohistochemistry using an antibody to STAT1. Informatics analysis of the differing profiles identified differences in pathways associated with integrin signaling and inflammation mediated by chemokines and cytokines.

Conclusions

Comparing the proteomic profiles of vSCC morphologic variants indicates that increased expression of collagen subunits and decreased expression of STAT1 are associated with a more aggressive tumor variant, defined by increased incidence of nodal metastases and tumor recurrence. Informatic analyses further identify that both alterations in cell interaction with matrix and immune function differ with tumor aggressiveness. Identification of these pathways provides a molecular basis for understanding aggressiveness of vSCC.

Electronic supplementary material

The online version of this article (10.1186/s12014-017-9175-8) contains supplementary material, which is available to authorized users.

Effect of Serum Immunoglobulins on Routine Coagulation Tests: A Comparison of Coagulation Analyzers using Mechanical and Optical Clot Detection

BACKGROUND

We previously showed that the prothrombin time (PT), but not activated partial thromboplastin time (APTT), is correlated with serum immunoglobulin level in patients with plasma cell neoplasms.

METHODS

To determine if the observed effect of serum immunoglobulins on PT was reagent and/or method dependent, PT and APTT were measured in plasma samples obtained from patients referred to the Myeloma Institute using mechanical (STAR Evolution; Diagnostica Stago) and optical clot detection (ACL TOP 500 analyzer; Instrumentation Laboratory) and manufacturer provided reagents.

RESULTS

A total of 97 patients were included in this study. Twelve patients had abnormal coagulation test results. An isolated prolonged PT was found in 8 patients and an isolated prolonged PTT was detected in 4 patients.

CONCLUSION

The PT, but not APTT, was positively correlated with serum paraprotein level and this correlation was observed regardless of the reagents and instrumentation used to assess clot time.

A Consensus Definitive Classification of Scavenger Receptors and Their Roles in Health and Disease

Scavenger receptors constitute a large family of proteins that are structurally diverse and participate in a wide range of biological functions. These receptors are expressed predominantly by myeloid cells and recognize a diverse variety of ligands including endogenous and modified host-derived molecules and microbial pathogens. There are currently eight classes of scavenger receptors, many of which have multiple names, leading to inconsistencies and confusion in the literature. To address this problem, a workshop was organized by the United States National Institute of Allergy and Infectious Diseases, National Institutes of Health, to help develop a clear definition of scavenger receptors and a standardized nomenclature based on that definition. Fifteen experts in the scavenger receptor field attended the workshop and, after extensive discussion, reached a consensus regarding the definition of scavenger receptors and a proposed scavenger receptor nomenclature. Scavenger receptors were defined as cell surface receptors that typically bind multiple ligands and promote the removal of nonself or altered-self targets. They often function by mechanisms that include endocytosis, phagocytosis, adhesion, and signaling that ultimately lead to the elimination of degraded or harmful substances. Based on this definition, nomenclature and classification of these receptors into 10 classes were proposed. This classification was discussed at three national meetings and input from participants at these meetings was requested. The following manuscript is a consensus statement that combines the recommendations of the initial workshop and incorporates the input received from the participants at the three national meetings.

Diagnostic Utility of Interleukin-6 Expression by Immunohistochemistry in Differentiating Castleman Disease Subtypes and Reactive Lymphadenopathies

The objective of the study was to evaluate the expression pattern of interleukin-6 (IL-6) to determine its utility in differentiating Castleman Disease subtypes and reactive lymphadenopathies. Paraffin-embedded tissue blocks from 20 cases referred for assessment of Castleman Disease (CD) and 4 cases of reactive hyperplasia were selected for immunohistochemical staining with an IL-6 antibody. Six pathologists evaluated the hematoxylin and eosin stained tissue sections and IL-6 expression pattern. Of 20 CD referral cases, the pathologic diagnosis was CD in 14 cases and included 6 hyaline-vascular (HV-CD), 6 plasma cell (PC-CD) and 2 "mixed type"-CD cases. The remaining 6 referral cases showed morphologic features consistent with reactive lymphadenopathy. Patients with non-CD, reactive lymphadenopathies had clinical and/or laboratory features of systemic lupus erythematosus, Hashimoto's disease, viral infection or chronic cellulitis. The pattern of IL-6 expression differed between CD subtypes and non-CD cases. In PC-CD, IL-6 expression was detected in plasma cells and vascular endothelial cells; whereas IL-6 immunoreactivity was detected primarily in vascular endothelial cells in HV-CD. Interfollicular plasma cells were prominent in PC-CD and reactive lymphadenopathies; however, IL-6 expression was significantly increased in PC-CD compared to reactive lymph nodes. Together with morphologic features, the expression pattern of IL-6 detected by immunohistochemistry is helpful to distinguish CD subtypes and reactive mimics.

Abstract 1450: Tumor-associated glycans interact with macrophages through class-A scavenger receptor

Introduction. Tumor initiation and growth are associated with modifications to the glycan structure of glycoproteins, glycolipids and proteoglycans present on the cell surface. Suppression of the anti-tumor immune response is a putative mechanism linking tumor-associated-glycans to tumor progression. Within a tumor microenvironment, the conversion of macrophages from an activated, immunological type (referred to as M1) to an alternatively activated, IL-10 secreting type (referred to as M2) suppresses the immune response and potentiates tumor progression. We previously reported that the class A scavenger receptor (SR-A)-mediated macrophage activation enhances production of IL-10, indicating promotion of an immunosuppressive M2 phenotype. Therefore, tumor glycans may suppress immune responses by interacting with macrophages and promoting an M2 phenotype. Such interactions are most likely mediated by pattern recognition receptors such as SR-A. In the current study, we investigated whether tumor glycans interact with macrophages via binding to SRA.

Methods. Binding of recombinant soluble SR-A to breast cancer cells and relevant glycan structures was assayed by flow cytometry and ELISA assays. N-glycosylation was inhibited by incubating cells with tunicamycin. Peritoneal macrophages were harvested from wild type (SR-A+/+) and knock-out (SR-A-/-) mice and used for ligand competition and functional assays. A peptide mimic of GlcNAc/GalNAc-containing tumor-associated carbohydrates was used for binding and competition assays.

Results. To determine whether carbohydrates present on tumor cells are SR-A ligands, we examined the binding of a soluble SR-A protein to tumor cells. We found that soluble SR-A bound to breast cancer cells but not to normal epithelial cells, and that this tumor-specific binding of soluble SR-A was abolished by treating cells with tunicamycin. These results demonstrate that cell surface tumor-associated glycans are ligands for SR-A. Using purified glycans, we found that soluble SR-A bound to multiple breast cancer-associated glycans. To assess the potential consequence of glycan binding to SR-A on macrophage function, we adhered primary macrophages to plates coated with a carbohydrate-mimetic peptide and found that SR-A+/+ macrophages bound to CMP-coated plates showed increased IL-10 production relative to SR-A-/- macrophages. The CMP also competed for acetylated LDL binding to macrophages, indicating that it is a ligand for SR-A. These results suggest that SR-A binding to carbohydrate promotes macrophages to adopt an M2 phenotype.

Conclusions. Together, our results indicate that tumor-associated glycans interact with macrophages via SR-A, and that this interaction leads to production of IL-10, which is a key characteristic of immunosuppressive (M2-like) macrophages.

Citation Format: Behjatolah Monzavi Karbassi, Thomas Kieber-Emmons, Steven R. Post. Tumor-associated glycans interact with macrophages through class-A scavenger receptor. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1450.

Pathologic features of aggressive vulvar carcinoma are associated with epithelial-mesenchymal transition

Factors contributing to aggressive behavior in vulvar squamous cell carcinoma (vSCC) are poorly defined; however, a recent study has shown that vSCCs with an infiltrative pattern of invasion and fibromyxoid stroma are associated with worse outcomes than tumors with a pushing or nested pattern of invasion and lymphoplasmacytic stroma. Epithelial-mesenchymal transition (EMT) has been associated with tumor progression in a number of malignancies, and this study proposes that EMT contributes to tumor aggressiveness in this subset of vSCC. Immunohistochemistry was used to detect nuclear localization of β-catenin, loss of E-cadherin, and presence of vimentin in 58 cases of vSCC. The association of these phenotypic changes with pathologic features and clinical outcomes was tested using Fisher's exact and χ(2) analyses (significance at P≤.05). EMT-associated features were identified in 45 of 58 cases (78%) with 28 cases exhibiting more than one feature. Nuclear β-catenin and presence of vimentin were significantly more likely to occur in tumors with an infiltrative pattern of invasion or a fibromyxoid stromal response. Loss of E-cadherin was significantly associated with an infiltrative pattern, but not a fibromyxoid stroma. Risk for tumor recurrence was significantly increased in tumors with nuclear localization of β-catenin alone or in tumors displaying multiple EMT-associated features. These results suggest that the development of EMT may be a mechanism by which infiltrative vulvar tumors with a fibromyxoid stromal response behave more aggressively and convey worse outcomes than tumors that do not exhibit these pathologic features.

Cleavage of Type I Collagen by Fibroblast Activation Protein-α Enhances Class A Scavenger Receptor Mediated Macrophage Adhesion

Pathophysiological conditions such as fibrosis, inflammation, and tumor progression are associated with modification of the extracellular matrix (ECM). These modifications create ligands that differentially interact with cells to promote responses that drive pathological processes. Within the tumor stroma, fibroblasts are activated and increase the expression of type I collagen. In addition, activated fibroblasts specifically express fibroblast activation protein-α (FAP), a post-prolyl peptidase. Although FAP reportedly cleaves type I collagen and contributes to tumor progression, the specific pathophysiologic role of FAP is not clear. In this study, the possibility that FAP-mediated cleavage of type I collagen modulates macrophage interaction with collagen was examined using macrophage adhesion assays. Our results demonstrate that FAP selectively cleaves type I collagen resulting in increased macrophage adhesion. Increased macrophage adhesion to FAP-cleaved collagen was not affected by inhibiting integrin-mediated interactions, but was abolished in macrophages lacking the class A scavenger receptor (SR-A/CD204). Further, SR-A expressing macrophages localize with activated fibroblasts in breast tumors of MMTV-PyMT mice. Together, these results demonstrate that FAP-cleaved collagen is a substrate for SR-A-dependent macrophage adhesion, and suggest that by modifying the ECM, FAP plays a novel role in mediating communication between activated fibroblasts and macrophages.

Rapid on-site evaluation of EBUS-TBNA specimens of lymph nodes: Comparative analysis and recommendations for standardization

BACKGROUND

There is no widely accepted rapid on-site evaluation (ROSE) reporting system for endobronchial ultrasound-guided transbronchial needle aspiration. At the University of Arkansas for Medical Sciences, ROSE reporting was unstructured. The goal was to evaluate, compare, and improve upon 2 structured approaches proposed in the literature.

METHODS

One hundred eighteen consecutive nodal aspirates were retrospectively reviewed by a pathology resident and a staff cytopathologist, both of whom were blinded to the original unstructured readings. Each reviewer interpreted every specimen with 2 different structured criteria proposed in the literature: criteria from the University of Minnesota (the Minnesota [MN] criteria) and criteria from the North Shore Long Island Jewish Health System (the New York [NY] criteria). The data allowed a comparison of the original unstructured ROSE system with the MN and NY scoring schemes and the final diagnosis.

RESULTS

Original on-site adequacy (OSA) had been assessed at 96%. Three cases were false-adequate according to the original unstructured approach; these had been called adequate on site, but a subsequent slide review including cell blocks did not show definite nodal tissue. OSA dropped to 86% with the MN criteria and to 85% with the NY criteria. No false-adequate on-site diagnoses would have been rendered with the application of either structured criteria. There were no significant differences between the MN and NY criteria with respect to the determination of OSA. An assessment of ease of application favored the NY criteria. With respect to diagnostic categories, each of the systems (MN and NY) was felt to have a category of value not used by the other system.

CONCLUSIONS

A standardized intra- and inter-institutional system for ROSE reporting is needed. On the basis of comparative analyses and consensus, modifications to prior criteria have been proposed in the hope of approaching this goal.

Prostaglandins produced during class A scavenger receptor-mediated macrophage adhesion differentially regulate cytokine production

Inflammation is associated with modification of the extracellular environment, changes in cytokine expression, and the accumulation of immune cells. Such modifications create ligands that support SR-A-mediated macrophage adhesion and retention. This may be particularly important in settings, such as atherosclerosis and diabetes, as modified lipoproteins and gluc-collagen are ligands for SR-A. SR-A-mediated adhesion requires the PLA₂-dependent generation of AA and its metabolism by 12/15 LOX. In contrast, the inhibition of the COX-dependent conversion of AA to PG had no effect on SR-A-mediated adhesion. In this study, macrophages were isolated from SR-A^+/+ and SR-A^-/- mice and plated on gluc-collagen to test the hypothesis that COX-derived PGs are produced during SR-A-mediated adhesion and regulate macrophage function. SR-A-mediated binding to gluc-collagen induced a rapid but transient increase in PG production, which required the activation of PLA₂ and Src kinase but not PI3K. SR-A^+/+ macrophages cultured on gluc-collagen for 24 h secreted a similar amount of TNF-α and 2.5-fold more IL-10 than SR-A^-/- macrophages. The inhibition of COX substantially increased TNF-α production but reduced IL-10 levels in SR-A^+/+ macrophages. These effects of COX inhibition were reversed by exogenous PGE₂ and mimicked by specific antagonism of the EP4 receptor. Thus, in addition to the enhancement of macrophage adhesion, SR-A binding to gluc-collagen stimulates PG production, which in turn, differentially regulates the expression of inflammatory cytokines.

Lipid rafts couple class A scavenger receptors to phospholipase A2 activation during macrophage adhesion

SR-A mediated macrophage adhesion to modified ECM proteins in a process that involves physical attachment of SR-A to modified ECM and activation of Lyn-PI3K and PLA2-12/15-lipoxygenase signaling pathways. Structurally, SR-A-mediated cell adhesion requires a 6-aa membrane-proximal cytoplasmic motif. However, the mechanism that couples SR-A-mediated adhesion to activation of these distinct signaling pathways is not known. For other adhesion receptors, including integrins, localization in cholesterol-rich LRs is an important mechanism for coupling the receptor with the activation of specific signaling pathways. We hypothesized that SR-A-mediated macrophage adhesion might also involve LRs. Our results demonstrate that SR-A is enriched in LRs in HEK cells that heterologously express SR-A and in macrophages that endogenously expressed the receptor. We further show that a truncated SR-A construct (SR-A(Δ1-49)), which mediates cell adhesion but not ligand internalization, is also enriched in LRs, suggesting an association between LRs and SR-A-dependent cell adhesion. To examine this association more directly, we used the cholesterol chelator MβCD to deplete cholesterol and disrupt LR function. We found that cholesterol depletion significantly decreased SR-A-mediated macrophage adhesion. We further show that decreased SR-A-dependent macrophage adhesion following cholesterol depletion results from the inhibition of PLA2 but not PI3K activation. Overall, our results demonstrate an important role for LRs in selectively coupling SR-A with PLA2 activation during macrophage adhesion.

Platelet glycoprotein Ib-IX as a regulator of systemic inflammation

OBJECTIVE

The platelet glycoprotein Ib-IX (GP Ib-IX) receptor is a well-characterized adhesion receptor supporting hemostasis and thrombosis via interactions with von Willebrand factor. We examine the GP Ib-IX/von Willebrand factor axis in murine polymicrobial sepsis, as modeled by cecal ligation and puncture (CLP).

APPROACH AND RESULTS

Genetic absence of the GP Ib-IX ligand, von Willebrand factor, prolongs survival after CLP, but absence of the receptor, GP Ib-IX, does not. Because absence of either von Willebrand factor or GP Ib-IX significantly impairs hemostasis and thrombosis, we sought to define additional GP Ib-IX-dependent pathways impacting survival in the CLP model. We document that the absence of GP Ib-IX leads to reduced platelet-neutrophil and platelet-monocyte interactions. Twenty-four hours after CLP, absence of GP Ib-IX coincides with an alteration in cytokine levels, such as tumor necrosis factor-α secreted by monocytes, and increased macrophage-1 antigen expression by neutrophils.

CONCLUSIONS

In contrast to the well-characterized proinflammatory properties of platelets, we describe in the CLP model an anti-inflammatory property associated with platelet GP Ib-IX. Thus, a single platelet receptor displays a dual modulatory role in both the thrombotic and inflammatory pathways associated with polymicrobial sepsis. In sharing leucine-rich motifs with toll-like receptors, platelet GP Ib-IX can be considered a multifunctional participant in hemostasis, thrombosis, and the inflammatory cascade. The results highlight a dynamic role for platelets in systemic inflammation and add to the complex pathophysiologic events that occur during the dysregulated coagulation and inflammation associated with sepsis.

The ral exchange factor rgl2 promotes cardiomyocyte survival and inhibits cardiac fibrosis

Cardiomyocytes compensate to acute cardiac stress by increasing in size and contractile function. However, prolonged stress leads to a decompensated response characterized by cardiomyocyte death, tissue fibrosis and loss of cardiac function. Identifying approaches to inhibit this transition to a decompensated response may reveal important targets for treating heart failure. The Ral guanine nucleotide disassociation (RalGDS) proteins are Ras-interacting proteins that are upregulated by hypertrophic stimuli. The Ral guanine nucleotide dissociation stimulator-like 2 (Rgl2) is a member of the RalGDS family that modulates expression of hypertrophic genes in cardiomyocytes. However, the pathophysiologic consequence of increased Rgl2 expression in cardiomyoctyes remains unclear. To evaluate the effect of increasing Rgl2 activity in the heart, transgenic mice with cardiac-targeted over-expression of Rgl2 were generated. Although Ral activation was increased, there were no apparent morphologic or histological differences between the hearts of Rgl2 transgenic and nontransgenic mice indicating that increased Rgl2 expression had no effect on basal cardiac phenotype. To determine if Rgl2 modulates the cardiac response to stress, mice were infused with the ß-adrenergic receptor agonist, isoproterenol. Isoproterenol infusion increased heart mass in both Rgl2 transgenic and nontransgenic mice. However, unlike nontransgenic mice, Rgl2 transgenic mice showed no morphologic evidence of cardiomyocyte damage or increased cardiac fibrosis following isoproterenol infusion. Increased Rgl2 expression in cultured cardiomyocytes stimulated Ral activation and inhibited staurosporine-induced apoptosis via increased activation of PI3-kinase. Activation of the PI3-kinase signaling pathway was confirmed in hearts isolated from Rgl2 transgenic mice. Increased expression and function of Rgl2 in cardiomyocytes promotes activation of the PI3-kinase signaling cascade and protects from carciomyocyte death and pathologic cardiac fibrosis. Taken further, these results suggest that Rgl2 upregulation in hypertrophic hearts may be a protetive mechanism, and that Rgl2 may be a novel therapeutic target in treating heart disease.

Prolonged prothrombin time correlates with serum monoclonal protein concentration in patients with plasma cell dyscrasia

INTRODUCTION

Abnormal screening coagulation tests are frequently observed in asymptomatic patients with multiple myeloma and other plasma cell neoplasms.

METHODS

Prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen activity were correlated with clinical history and disease parameters in patients referred to the Myeloma Institute for Research and Therapy.

RESULTS

An isolated prolonged PT was the most common abnormal coagulation test (25%). Prolonged PT was more frequently observed in patients with multiple myeloma (n = 157) compared to MGUS patients (n = 34) or other diagnostic categories of plasma cell dyscrasia. There were no differences in age, gender, previous chemotherapy, or immunoglobulin isotype in patients with isolated prolonged PT (n = 62) compared to those with normal screening coagulation tests (n = 173). Fibrinogen activity was significantly lower in patients with prolonged PT; however, there was no correlation between fibrinogen activity and PT. Serum M protein concentrations were significantly greater in patients with prolonged PT and were positively correlated with PT.

CONCLUSION

An association between disease severity and prolonged PT is suggested by our finding that patients with multiple myeloma were more likely to have prolonged PT than patients with other plasma cell neoplasms. Of the factors examined, the monoclonal protein level was significantly higher in patients with isolated prolonged PT and correlated with PT.

SR-A ligand and M-CSF dynamically regulate SR-A expression and function in primary macrophages via p38 MAPK activation

BACKGROUND

Inflammation is characterized by dynamic changes in the expression of cytokines, such as M-CSF, and modifications of lipids and proteins that result in the formation of ligands for Class A Scavenger Receptors (SR-A). These changes are associated with altered SR-A expression in macrophages; however, the intracellular signal pathways involved and the extent to which SR-A ligands regulate SR-A expression are not well defined. To address these questions, SR-A expression and function were examined in resident mouse peritoneal macrophages incubated with M-CSF or the selective SR-A ligand acetylated-LDL (AcLDL).

RESULTS

M-CSF increased SR-A expression and function, and required the specific activation of p38 MAPK, but not ERK1/2 or JNK. Increased SR-A expression and function returned to basal levels 72 hours after removing M-CSF. We next determined whether prolonged incubation of macrophages with SR-A ligand alters SR-A expression. In contrast to most receptors, which are down-regulated by chronic exposure to ligand, SR-A expression was reversibly increased by incubating macrophages with AcLDL. AcLDL activated p38 in wild-type macrophages but not in SR-A-/- macrophages, and p38 activation was specifically required for AcLDL-induced SR-A expression.

CONCLUSIONS

These results demonstrate that in resident macrophages SR-A expression and function can be dynamically regulated by changes in the macrophage microenvironment that are typical of inflammatory processes. In particular, our results indicate a previously unrecognized role for ligand binding to SR-A in up-regulating SR-A expression and activating p38 MAPK. In this way, SR-A may modulate inflammatory responses by enhancing macrophage uptake of modified protein/lipid, bacteria, and cell debris; and by regulating the production of inflammatory cytokines, growth factors, and proteolytic enzymes.

Regulation of class A scavenger receptor-mediated cell adhesion and surface localization by PI3K: identification of a regulatory cytoplasmic motif

The importance of cytoplasmic motifs in differentially regulating SR-A function was demonstrated by deleting the first 49 cytoplasmic aa (SR-A(Delta1-49)), which abolished SR-A-mediated ligand internalization without reducing cell adhesion. To identify additional cytoplasmic motifs within the first 49 aa that regulate SR-A function, the acidic residues in a conserved motif (EDAD) were changed to their amide derivatives (SR-A(QNAN)). The function and regulation of SR-A(QNAN) were compared with that of SR-A(Delta1-49) and SR-A in transfected HEK-293 cells. Blocking PI3K activation inhibited SR-A, but not SR-A(Delta1-49)- or SR-A(QNAN)-mediated cell adhesion. Although deleting (SR-A(Delta1-49)) or mutating (SR-A(QNAN)) the EDAD motif abolished the PI3K sensitivity of SR-A-mediated cell adhesion, these mutations did not affect ligand internalization or PI3K activation during cell adhesion. To define the mechanism by which PI3K regulates SR-A-mediated cell adhesion, the cellular localization of wild-type and mutant SR-A was examined. PI3K inhibition reduced surface localization of SR-A but not of SR-A(Delta1-49) or SR-A(QNAN). The regulation of SR-A surface localization by PI3K was confirmed in peritoneal macrophages, which endogenously express SR-A. Together, these results suggest a pathway in which SR-A binding to an immobilized ligand activates PI3K to recruit more receptor to the plasma membrane and enhances cell adhesion.

Class A scavenger receptor-mediated macrophage adhesion requires coupling of calcium-independent phospholipase A(2) and 12/15-lipoxygenase to Rac and Cdc42 activation

Class A scavenger receptors (SR-A) participate in multiple macrophage functions including adhesion to modified extracellular matrix proteins present in various inflammatory disorders such as atherosclerosis and diabetes. By mediating macrophage adhesion to modified proteins and increasing macrophage retention, SR-A may contribute to the inflammatory process. Eicosanoids produced after phospholipase A(2) (PLA(2))-catalyzed release of arachidonic acid (AA) are important regulators of macrophage function and inflammatory responses. The potential roles of AA release and metabolism in SR-A-mediated macrophage adhesion were determined using macrophages adherent to modified protein. SR-A-dependent macrophage adhesion was abolished by selectively inhibiting calcium-independent PLA(2) (iPLA(2)) activity and absent in macrophages isolated from iPLA(2) beta(-/-) mice. Our results further demonstrate that 12/15-lipoxygenase (12/15-LOX)-derived, but not cyclooxygenase- or cytochrome P450-dependent epoxygenase-derived AA metabolites, are specifically required for SR-A-dependent adhesion. Because of their role in regulating actin polymerization and cell adhesion, Rac and Cdc42 activation were also examined and shown to be increased via an iPLA(2)- and LOX-dependent pathway. Together, our results identify a novel role for iPLA(2)-catalyzed AA release and its metabolism by 12/15-LOX in coupling SR-A-mediated macrophage adhesion to Rac and Cdc42 activation.

The Effect of Class A Scavenger Receptor Deficiency in Bone

Class A scavenger receptor (SR-A) is predominantly expressed by macrophages, and because osteoclasts are of monocyte/macrophage lineage, SR-A is of potential interest in osteoclast biology. In addition to modified low density lipoprotein uptake, SR-A is also important in cell attachment and signaling. In this study we evaluated the effect of SR-A deletion on bone. Knock-out animals have 40% greater body weight than wild type. Body composition analyses demonstrated that total lean and fat body mass were greater in knock-out animals, but there was no significant difference in percent fat and lean body mass. Bone mineral density and content were significantly greater in knock-out compared with wild type animals. Micro-computed tomography analyses confirmed that total volume, bone volume as well as trabecular number, thickness, and connectivity were significantly greater in knock-out mice. As expected, trabecular separation was greater in wild type mice. The phenotype appears to be explained by 60% fewer osteoclasts in females and 35% fewer in males compared to wild type mice with a paradoxical increase in nuclei/osteoclast in knock-out animals. Furthermore, there were no differences in adipocyte number and osteoblast number or activity. The addition of the soluble extracellular domain of SR-A to RAW264.7 cells stimulated a concentration-dependent increase in osteoclast differentiation that was receptor activator of nuclear factor-kappaB ligand (RANKL)-dependent. Soluble SR-A had no effect on cell proliferation in the presence of RANKL but stimulated a 40% increase in numbers in the absence of RANKL. We conclude that SR-A plays a role in normal osteoclast differentiation, suggesting a novel role for this receptor in bone biology.

Class A scavenger receptor-mediated cell adhesion requires the sequential activation of Lyn and PI3-kinase

Class A scavenger receptors (SR-A) participate in multiple macrophage functions including macrophage adhesion to modified proteins. SR-A-mediated adhesion may therefore contribute to chronic inflammation by promoting macrophage accumulation at sites of protein modification. The mechanisms that couple SR-A binding to modified proteins with increased cell adhesion have not been defined. In this study, SR-A expressing HEK cells and SR-A+/+ or SR-A-/- macrophages were used to delineate the signaling pathways required for SR-A-mediated adhesion to modified protein. Inhibiting G(i/o) activation, which decreases initial SR-A-mediated cell attachment, did not prevent the subsequent spreading of attached cells. In contrast, inhibition of Src kinases or PI3-kinase abolished SR-A-dependent cell spreading without affecting SR-A-mediated cell attachment. Consistent with these results, the Src kinase Lyn and PI3-kinase were sequentially activated during SR-A-mediated cell spreading. Furthermore, activation of both Lyn and PI3-kinase was required for enhancing paxillin phosphorylation. Activation of a Src kinase-PI3-kinase-Akt pathway was also observed in cells expressing a truncated SR-A protein that does not internalize indicating that SR-A-mediated activation of intracellular signaling cascades following adhesion to MDA-BSA is independent of receptor internalization. Thus SR-A binding to modified protein activates signaling cascades that have distinct roles in regulating initial cell attachment and subsequent cell spreading.

Phosphatidylinositol-3-kinase regulates scavenger receptor class B type I subcellular localization and selective lipid uptake in hepatocytes

OBJECTIVE

The high-density lipoprotein (HDL) receptor scavenger receptor Class B type I (SR-BI) plays a key role in mediating the final step of reverse cholesterol transport. This study examined the possible regulation of hepatic SR-BI by phosphatidylinositol-3-kinase (PI3K), a well known regulator of endocytosis and membrane protein trafficking.

METHODS AND RESULTS

SR-BI-dependent HDL selective cholesterol ester uptake in human HepG2 hepatoma cells was decreased (approximately 50%) by the PI3K inhibitors wortmannin and LY294002. Insulin increased selective uptake (approximately 30%), and this increase was blocked by PI3K inhibitors. Changes in SR-BI activity could be accounted for by pronounced changes in the subcellular localization and cell surface expression of SR-BI as determined by HDL cell surface binding, receptor biotinylation studies, and confocal fluorescence microscopy of HepG2 cells expressing green fluorescent protein-tagged SR-BI. Thus, under conditions of PI3K activation by insulin, and to a lesser extent by the SR-BI ligand HDL, cell surface expression of SR-BI was promoted, resulting in increased SR-BI-mediated HDL selective lipid uptake.

CONCLUSIONS

Our data indicate that PI3K activation stimulates hepatic SR-BI function post-translationally by regulating the subcellular localization of SR-BI in a P13K-dependent manner. Decreased hepatocyte PI3K activity in insulin-resistant states, such as type 2 diabetes, obesity, or metabolic syndrome, may impair reverse cholesterol transport by reducing cell surface expression of SR-BI.

Up-regulation of CPI-17 phosphorylation in diabetic vasculature and high glucose cultured vascular smooth muscle cells

OBJECTIVE

Contractile responses are significantly increased in vascular smooth muscle tissues isolated from type 2 diabetic db/db mice (hyperreactivity). However, the molecular mechanisms underlying this hyperreactivity are largely unknown. The current study investigates the roles of RhoA, ROCK (rho kinase), PKC (protein kinase C), and CPI-17 (protein kinase C-potentiated phosphatase inhibitor of 17 kDa), molecules shown to play pivotal physiological roles regulating smooth muscle contraction, in diabetes-associated vascular smooth muscle hyperreactivity.

METHODS

Experiments utilized db/db mouse mesenteric arteries and aortas and primary rat aortic smooth muscle cells (VSMCs) cultured in high or normal glucose. RhoA, ROCK, and CPI-17 protein expression and activity were determined by immunoblotting for total or phosphorylated proteins. RhoA activity was determined by subcellular fractionation and pull-down assays. Isometric contractions were determined using isolated mesenteric artery strips.

RESULTS

Active phosphorylated CPI-17 and total and active membrane-bound RhoA were significantly increased in db/db mouse mesenteric arteries and aortas. High glucose time-dependently activated RhoA, ROCK, and CPI-17 in VSMCs. Moreover, inhibiting either RhoA with C3 exoenzyme or ROCK with Y-27632 or H-1152 for 30 min diminished high glucose-induced CPI-17 phosphorylation. Inhibiting protein kinase C (PKC) with GF109203X for 30 min did not inhibit high glucose-induced CPI-17 phosphorylation. Interestingly, when added at the same time as high glucose for a total of 48 h, GF109203X diminished high glucose-induced RhoA and ROCK activation as well as CPI-17 phosphorylation, suggesting PKC is required for high glucose-induced RhoA/ROCK activation and consequently CPI-17 phosphorylation. Importantly, in isolated db/db mouse mesenteric arteries, inhibiting ROCK with Y-27632 or H-1152 significantly alleviated the contractile hyperreactivity in response to phenylephrine or high potassium.

CONCLUSIONS

Diabetes and high glucose activate RhoA, ROCK, and CPI-17, which in turn contribute to diabetic vascular smooth muscle hyperreactivity.

SREC-I, a type F scavenger receptor, is an endocytic receptor for calreticulin

Calreticulin and gp96 (GRP94) traffic associated peptides into the major histocompatibility complex class-I cross-presentation pathway of antigen-presenting cells (APCs). Efficient accession of the cross-presentation pathway requires APC receptor-mediated endocytosis of the chaperone/peptide complexes. Previously, scavenger receptor class-A (SRA) was shown to play a substantial role in trafficking gp96 and calreticulin into macrophages, accounting for half of total receptor-mediated uptake. However, the scavenger receptor ligand fucoidin competed the chaperone uptake beyond that accounted for by SRA, indicating that another scavenger receptor(s) may also contribute. Consistent with this hypothesis, we showed that the residual calreticulin uptake into SRA(-/-) macrophages is competed by the scavenger receptor ligand acetylated low density lipoprotein (LDL). We now report that an additional scavenger receptor, SREC-I (scavenger receptor expressed by endothelial cell-I), mediates the endocytosis of calreticulin and gp96. Ectopic expression of SREC-I in Chinese hamster ovary cells yielded chaperone recognition and uptake, and these processes were competed by the inhibitory ligands fucoidin and acetylated (Ac)LDL. Although AcLDL competes for the chaperone interactions with SRA and SREC, we showed that not all of the scavenger receptors, which bind AcLDL, bind calreticulin or gp96. The overexpression of SREC-I in macrophages increased chaperone endocytosis, indicating that SREC-I functions in APCs and that the cytosolic components necessary for the endocytosis of SREC-I and its cargo are present and not limiting in APCs. These data identify a novel class of ligands for SREC-I and provide insight into the mechanisms by which APCs and potentially endothelial cells traffic chaperone/antigen complexes.