Radiation Therapy Induces Macrophages to Suppress T-Cell Responses Against Pancreatic Tumors in Mice.

BACKGROUND & AIMS: The role of radiation therapy in the treatment of patients with pancreatic ductal adenocarcinoma (PDA) is controversial. Randomized controlled trials investigating the efficacy of radiation therapy in patients with locally advanced unresectable PDA have reported mixed results, with effects ranging from modest benefit to worse outcomes compared with control therapies. We investigated whether radiation causes inflammatory cells to acquire an immune-suppressive phenotype that limits the therapeutic effects of radiation on invasive PDAs and accelerates progression of preinvasive foci. METHODS: We investigated the effects of radiation therapy in p48(Cre);LSL-Kras(G12D) (KC) and p48(Cre);LSLKras(G12D);LSL-Trp53(R172H) (KPC) mice, as well as in C57BL/6 mice with orthotopic tumors grown from FC1242 cells derived from KPC mice. Some mice were given neutralizing antibodies against macrophage colony-stimulating factor 1 (CSF1 or MCSF) or F4/80. Pancreata were exposed to doses of radiation ranging from 2 to 12 Gy and analyzed by flow cytometry. RESULTS: Pancreata of KC mice exposed to radiation had a higher frequency of advanced pancreatic intraepithelial lesions and more foci of invasive cancer than pancreata of unexposed mice (controls); radiation reduced survival time by more than 6 months. A greater proportion of macrophages from radiation treated invasive and preinvasive pancreatic tumors had an immune-suppressive, M2-like phenotype compared with control mice. Pancreata from mice exposed to radiation had fewer CD8(+) T cells than controls, and greater numbers of CD4(+) T cells of T-helper 2 and T-regulatory cell phenotypes. Adoptive transfer of T cells from irradiated PDA to tumors of control mice accelerated tumor growth. Radiation induced production of MCSF by PDA cells. A neutralizing antibody against MCSF prevented radiation from altering the phenotype of macrophages in tumors, increasing the anti-tumor T-cell response and slowing tumor growth. CONCLUSIONS: Radiation treatment causes macrophages murine PDA to acquire an immune-suppressive phenotype and disabled T-cell-mediated anti-tumor responses. MCSF blockade negates this effect, allowing radiation to have increased efficacy in slowing tumor growth.

Development of a novel multiplexed assay for quantification of transforming growth factor-ß (TGF-ß).

Changes in activity or levels of transforming growth factor-ß (TGF-ß) are associated with a variety of diseases; however, measurement of TGF-ß in biological fluids is highly variable. TGF-ß is biologically inert when associated with its latency-associated peptide (LAP). Most available immunoassays require exogenous activation by acid/heat to release TGF-ß from the latent complex. We developed a novel electrochemiluminescence-based multiplexed assay on the MesoScale Discovery® platform that eliminates artificial activation, simultaneously measures both active TGF-ß1 and LAP1 and includes an internal control for platelet-derived TGF-ß contamination in blood specimens. We optimized this assay to evaluate plasma levels as a function of activation type and clinical specimen preparation. We determined that breast cancer patients' plasma have higher levels of circulating latent TGF-ß (LTGF-ß) as measured by LAP1 than healthy volunteers (p < 0.0001). This assay provides a robust tool for correlative studies of LTGF-ß levels with disease, treatment outcomes and toxicity with a broad clinical applicability.

Response to microtubule-interacting agents in primary epithelial ovarian cancer cells.

BACKGROUND: Ovarian cancer constitutes nearly 4% of all cancers among women and is the leading cause of death from gynecologic malignancies in the Western world. Standard first line adjuvant chemotherapy treatments include Paclitaxel (Taxol) and platinum-based agents. Taxol, epothilone B (EpoB) and discodermolide belong to a family of anti-neoplastic agents that specifically interferes with microtubules and arrests cells in the G2/M phase of the cell cycle. Despite initial success with chemotherapy treatment, many patients relapse due to chemotherapy resistance. In vitro establishment of primary ovarian cancer cells provides a powerful tool for better understanding the mechanisms of ovarian cancer resistance. We describe the generation and characterization of primary ovarian cancer cells derived from ascites fluids of patients with epithelial ovarian cancer. METHODS: Chemosensitivity of these cell lines to Taxol, EpoB and discodermolide was tested, and cell cycle analysis was compared to that of immortalized ovarian cancer cell lines SKOV3 and Hey. The relationship between drug resistance and αß-tubulin and p53 status was also investigated. RESULTS: All newly generated primary cancer cells were highly sensitive to the drugs. αß-tubulin mutation was not found in any primary cell lines tested. However, one cell line that harbors p53 mutation at residue 72 (Arg to Pro) exhibits altered cell cycle profile in response to all drug treatments. Immortalized ovarian cancer cells respond differently to EpoB treatment when compared to primary ovarian cancer cells, and p53 polymorphism suggests clinical significance in the anti-tumor response in patients. CONCLUSIONS: The isolation and characterization of primary ovarian cancer cells from ovarian cancer patients' specimens contribute to further understanding the nature of drug resistance to microtubule interacting agents (MIAs) currently used in clinical settings.

Cytotoxic chemotherapy potentiates the immune response and efficacy of combination CXCR4/PD-1 inhibition in models of pancreatic ductal adenocarcinoma.

Purpose: The CXCL12-CXCR4 chemokine axis plays a significant role in modulating T-cell infiltration into the pancreatic tumor microenvironment. Despite promising preclinical findings, clinical trials combining inhibitors of CXCR4 (AMD3100/BL-8040) and anti-programmed death 1/ligand1 (anti-PD1/PD-L1) have failed to improve outcomes. Experimental Design: We utilized a novel ex vivo autologous patient-derived immune/organoid (PDIO) co-culture system using human peripheral blood mononuclear cells and patient derived tumor organoids, and in vivo the autochthonous LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre (KPC) pancreatic cancer mouse model to interrogate the effects of either monotherapy or all combinations of gemcitabine, AMD3100, and anit-PD1 on CD8+ T cell activation and survival. Results: We demonstrate that disruption of the CXCL12-CXCR4 axis using AMD3100 leads to increased migration and activation of CD8+ T-cells. In addition, when combined with the cytotoxic chemotherapy gemcitabine, CXCR4 inhibition further potentiated CD8+ T-cell activation. We next tested the combination of gemcitabine, CXCR4 inhibition, and anti-PD1 in the KPC pancreatic cancer mouse model and demonstrate that this combination markedly impacted the tumor immune microenvironment by increasing infiltration of natural killer cells, the ratio of CD8+ to regulatory T-cells, and tumor cell death while decreasing tumor cell proliferation. Moreover, this combination extended survival in KPC mice. Conclusions: These findings suggest that combining gemcitabine with CXCR4 inhibiting agents and anti-PD1 therapy controls tumor growth by reducing immunosuppression and potentiating immune cell activation and therefore may represent a novel approach to treating pancreatic cancer.

Epothilone B enhances Class I HLA and HLA-A2 surface molecule expression in ovarian cancer cells.

OBJECTIVE: Ovarian cancer is the leading cause of death from gynecologic cancers in the United States. Epothilone B (EpoB), Taxol and vinblastine are anti-neoplastic agents that interfere with microtubules and arrest the cell cycle in the G2/M phase. EpoB is being evaluated in phase III clinical trials, and its analogs are currently being used in the treatment of taxane-resistant metastatic breast cancer. Little is known about the effect of these drugs on the immune response to tumors. Cancer cells evade immune recognition by down-regulating HLA Class I expression, allowing escape from immune surveillance and destruction. Our data illustrates the effect of microtubule-interacting agents on HLA Class I and HLA-A2 expression as well as the modulation of cytokine expression in ovarian cancer cells. METHODS: Ovarian cancer cells were treated with different concentrations of drugs. Cell surface expression and mRNA transcription of HLA Class I molecules and HLA-A2 was examined. IFNα, IL1ß, IL12 and IL6 mRNA expression was also evaluated upon EpoB treatment. RESULTS: Low-dose EpoB, Taxol and vinblastine greatly increased expression of HLA Class I and HLA-A2 molecules in Hey ovarian cancer cells. EpoB does not modulate HLA expression in drug-resistant ovarian cancer cells. The expression of IFNα, IL1ß, IL12 and IL6 is also markedly increased upon EpoB treatment. CONCLUSIONS: Nanomolar concentrations of microtubule-interacting agents enhance immune-visibility of ovarian cancer cells by increasing HLA Class I and pro-inflammatory cytokine expression. Immune recognition of tumor cells may be improved.

A Phase I Study of the Combination of Pexidartinib and Sirolimus to Target Tumor-Associated Macrophages in Unresectable Sarcoma and Malignant Peripheral Nerve Sheath Tumors.

PURPOSE: To evaluate the safety and tolerability in phase I first-in-human combination therapy with pexidartinib, an inhibitor of colony-stimulating factor-1 receptor, and sirolimus, an mTOR inhibitor, to target tumor-associated macrophage (TAM) polarization in soft tissue sarcomas (STS). PATIENTS AND METHODS: This multicenter phase I study used the time-to-event continual reassessment method (TITE-CRM) to study the combination of sirolimus, doses ranging from 2 to 6 mg, with pexidartinib, doses ranging from 600 to 1,000 mg, both provided continuously on a 28-day cycle, in patients with advanced sarcoma. A total of 24 patients [8 malignant peripheral nerve sheath tumor, 3 tenosynovial giant cell tumor (TGCT), 5 leiomyosarcoma, and 8 with other sarcoma subtypes] were enrolled. The median age was 46 years, 56% were male, and 61% had >2 prior lines of therapy. RESULTS: The recommended phase II dose was 2 mg of sirolimus combined with 1,000 mg of pexidartinib daily. Of the 18 evaluable subjects, 5 experienced dose-limiting toxicities (2 elevated aspartate aminotransferase/alanine aminotransferase, 2 elevated sirolimus trough levels, and 1 grade 5 dehydration). Most common grade 2 or higher treatment-related adverse events included anemia, fatigue, neutropenia, and lymphopenia. Clinical benefit was observed in 12 of 18 (67%) evaluable subjects with 3 partial responses (all in TGCT) and 9 stable disease. Tissue staining indicated a decreased proportion of activated M2 macrophages within tumor samples with treatment. CONCLUSIONS: Pexidartinib can be safely administered with sirolimus. These findings support further investigation of this combination to determine clinical efficacy. Clinicaltrials.gov identifier NCT02584647.

A double-edged sword: Prolonged detection of SARS-COV-2 in patients receiving cancer directed therapy.

INTRODUCTION: SARS-CoV-2 (S-2) infection duration and its impact on patients with cancer and mild to moderate COVID-19 undergoing cancer-directed therapy (CDT), especially in the underserved population, is not well described. We conducted a retrospective study to analyze S-2 positive (+) patients on CDT to describe the S-2 duration and its impact on CDT. METHODS: Two hundred ninety-nine patients with cancer were tested with nasopharyngeal (NP) S-2 PCR assay at Columbia University Medical Irving Center (CUIMC), a Minority-NCI Community Oncology site, of which 77 (26%) tested positive. We retrospectively analyzed 26 S-2 (+) patients with mild-to-moderate COVID-19 receiving CDT who consented to the study. NP PCR was repeated every 1 to 2 weeks until 2 successive negative (-) PCRs were obtained prior to restarting CDT. Time to 2 (-) PCR and serology results were recorded. Cycling thresholds (Ct) were obtained for S-2 specific targets and represented an indirect measure of viral load. RESULTS: Demographics of N = 26 patients are: Hispanic (N = 17, 65%), Black (N = 1, 4%), White (N = 7, 27%), and undeclared (N = 1, 4%). Among the tumor histologies represented, gastrointestinal (N = 9, 35%), breast (N = 5, 19%), and sarcoma (N = 3, 12%) were most common. Median time to 2 (-) PCR was 32 days. Twenty patients required greater than 14 days to achieve 2 sequential (-) swabs. CDT was delayed in 21 patients (81%) of whom three experienced disease progression, likely attributed to an interruption in CDT, which was delayed by a mean of 53 days. Interestingly, nine (41%) patients had Ct values greater than 34 for the pan SARS target and seven (32%) patients had Ct values greater than 34 for the SARS-COV-2 target. Sixteen of 16 patients on CDT, tested positive for IgG antibodies at the time of consent, despite protracted viral detectability by NP PCR. CONCLUSION: Patients receiving CDT appear to have prolonged detectable S-2 by PCR, which can lead to interruption of CDT and POD in patients. We believe and recommend that patients with asymptomatic to mild COVID-19 and aggressive malignancies are at greatest risk for cancer related morbidity and mortality due to CDT cessation and should be considered for continued CDT without interruption. Ct values and serology testing are tools that can help identify those patients on CDT who may be at greatest risk of worsening COVID-19 or of spreading S-2.

Autocrine TGFß Is a Survival Factor for Monocytes and Drives Immunosuppressive Lineage Commitment.

Transforming growth factor ß (TGFß) is an effector of immune suppression and contributes to a permissive tumor microenvironment that compromises effective immunotherapy. We identified a correlation between TGFB1 and genes expressed by myeloid cells, but not granulocytes, in The Cancer Genome Atlas lung adenocarcinoma data, in which high TGFB1 expression was associated with poor survival. To determine whether TGFß affected cell fate decisions and lineage commitment, we studied primary cultures of CD14+ monocytes isolated from peripheral blood of healthy donors. We discovered that TGFß was a survival factor for CD14+ monocytes, which rapidly executed an apoptotic program in its absence. Continued exposure to TGFß in combination with granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 6 (IL6) amplified HLA-DRlowCD14+CD11b+CD33+ myeloid-derived suppressor cells (MDSCs) at the expense of macrophage and dendritic cell (DC) differentiation. MDSCs generated in the presence of TGFß were more effective in suppressing T-cell proliferation and promoted the T regulatory cell phenotype. In contrast, inhibition of TGFß signaling using a small-molecule inhibitor of receptor kinase activity in CD14+ monocytes treated with GM-CSF and IL6 decreased MDSC differentiation and increased differentiation to proinflammatory macrophages and antigen-presenting DCs. The effect of autocrine and paracrine TGFß on myeloid cell survival and lineage commitment suggests that pharmacologic inhibition of TGFß-dependent signaling in cancer would favor antitumor immunity.

RFA strongly modulates the immune system and anti-tumor immune responses in metastatic liver patients.

Radiofrequency tumor ablation (RFA) is a therapeutic modality for liver cancer patients inducing localized tumor necrosis with maximal preservation of normal liver parenchyma. We investigated the immunomodulatory effects exerted by RFA treatment in liver cancer patients with metastatic liver lesions (13 patients) or hepatocellular carcinoma (HCC) (4 patients). Analysis of lymphocyte subsets by flow cytometry revealed that after RFA, CD3+ T cells, in particular CD4+, were decreased in metastatic cancer patients, while no change was observed in HCC patients. Moreover, RFA induced trafficking of naïve and memory CD62L+ T cells from circulation to tissues. When characterizing the function of T cells, proliferative response to PHA was strongly increased after 48 h from RFA in metastatic cancer patients. Furthermore, T cells produced IFN-gamma in response to the tumor associated MUC1 antigen. In contrast, humoral immune responses against tumor antigens such as MUC1 and HCV proteins were unaffected by RFA treatment, although increase of circulating B cells was observed only in metastatic cancer patients. These results indicate that RFA application can exert an activating effect on the immune system in metastatic cancer patients, favouring trafficking of lymphocyte subsets and enhancing tumor antigen specific cellular immune responses.

TLR9-independent activation of B lymphocytes by bacterial DNA.

The intracellular Toll-like receptor 9 (TLR9) is unique in its ability to recognize single-stranded DNA unmethylated at CpG motifs. Work from this laboratory showed that plasmid DNA is spontaneously internalized in B lymphocytes. This event is followed by the upregulation of costimulatory molecules and the acquisition of antigen presenting function by these cells. However, it is not known whether this phenomenon depends on TLR9. Because of the relevant role played by DNA-based drugs in immunotherapy and vaccination, and the central role of TLR9 signaling by CpG motifs, we decided to investigate whether signaling through TLR9 is a prerequisite for spontaneous transgenesis of lymphocytes. Here we found that transgene expression and upregulation of CD40 and CD86 costimulatory molecules was not inhibited by chloroquine treatment. Spontaneous transgenesis also occurred in B lymphocytes from TLR9-/- mice, and the injection of TLR9-/- transgenic B lymphocytes in C57Bl/6 mice induced both CD4 and CD8 T cell responses comparable to those induced by wild-type B lymphocytes. Collectively, these results suggest that plasmid DNA activates mammalian B lymphocytes through a TLR9 independent pathway.

Presence of both Mesenchymal and Carcinomatous Features in an In-vitro Model of Ovarian Carcinosarcoma Derived from Patients' Ascitic Fluid.

We have refined the technique for isolating and propagating cultures of primary ovarian carcinosarcoma cells (OSCs) derived from ascites, which allowed the cells to obtain the biphasic features of carcinosarcoma in cell culture conditions (presence of both carcinoma and mesenchymal morphologic types). This protocol involves a simple yet rapid method for the growth and propagation of ascites OSC in a basal culture medium. Autologous ascitic fluid was used as source of growth factors, and minimal manipulation was involved to establish the culture. The methodology allowed for the direct application of multiple molecular, cellular, and functional analyses within a few weeks of initial cell isolation, with the further potential of retrospective analyses of archived cells and tissues.

Attenuation of the DNA damage response by transforming growth factor-beta inhibitors enhances radiation sensitivity of non-small-cell lung cancer cells in vitro and in vivo.

PURPOSE: To determine whether transforming growth factor (TGF)-ß inhibition increases the response to radiation therapy in human and mouse non-small-cell lung carcinoma (NSCLC) cells in vitro and in vivo. METHODS AND MATERIALS: TGF-ß-mediated growth response and pathway activation were examined in human NSCLC NCI-H1299, NCI-H292, and A549 cell lines and murine Lewis lung cancer (LLC) cells. Cells were treated in vitro with LY364947, a small-molecule inhibitor of the TGF-ß type 1 receptor kinase, or with the pan-isoform TGF-ß neutralizing monoclonal antibody 1D11 before radiation exposure. The DNA damage response was assessed by ataxia telangiectasia mutated (ATM) or Trp53 protein phosphorylation, γH2AX foci formation, or comet assay in irradiated cells. Radiation sensitivity was determined by clonogenic assay. Mice bearing syngeneic subcutaneous LLC tumors were treated with 5 fractions of 6 Gy and/or neutralizing or control antibody. RESULTS: The NCI-H1299, A549, and LLC NSCLC cell lines pretreated with LY364947 before radiation exposure exhibited compromised DNA damage response, indicated by decreased ATM and p53 phosphorylation, reduced γH2AX foci, and increased radiosensitivity. The NCI-H292 cells were unresponsive. Transforming growth factor-ß signaling inhibition in irradiated LLC cells resulted in unresolved DNA damage. Subcutaneous LLC tumors in mice treated with TGF-ß neutralizing antibody exhibited fewer γH2AX foci after irradiation and significantly greater tumor growth delay in combination with fractionated radiation. CONCLUSIONS: Inhibition of TGF-ß before radiation attenuated DNA damage recognition and increased radiosensitivity in most NSCLC cells in vitro and promoted radiation-induced tumor control in vivo. These data support the rationale for concurrent TGF-ß inhibition and RT to provide therapeutic benefit in NSCLC.

Radiation fosters dose-dependent and chemotherapy-induced immunogenic cell death.

Established tumors are typified by an immunosuppresive microenvironment. Countering this naturally occurring phenomenon, emerging evidence suggests that radiation promotes a proimmunogenic milieu within the tumor capable of stimulating host cancer-specific immune responses. Three cryptic immunogenic components of cytotoxic-agent induced cell death-namely, calreticulin cell surface exposure, the release of high mobility group box 1 (HMGB1) protein, and the liberation of ATP-have been previously shown to be critical for dendritic cell (DC) activation and effector T-cell priming. Thus, these immune-mobilizing components commonly presage tumor rejection in response to treatment. We initially set out to address the hypothesis that radiation-induced immunogenic cell death (ICD) is dose-dependent. Next, we hypothesized that radiation would enhance chemotherapy-induced ICD when given concomitantly, as suggested by the favorable clinical outcomes observed in response to analogous concurrent chemoradiation regimens. Thus, we designed an in vitro assay to examine the 3 hallmark features of ICD at clinically relevant doses of radiation. We then tested the immunogenic-death inducing effects of radiation combined with carboplatin or paclitaxel, focusing on these combinations to mimic chemoradiation regimens actually used in clinical trials of early stage triple negative [NCT0128953/NYU-10-01969] and locally advanced [NYU-06209] breast cancer patients, respectively. Despite the obvious limitations of an in vitro model, radiotherapy produced both a dose-dependent induction and chemotherapeutic enhancement of ICD. These findings provide preliminary evidence that ICD stimulated by either high-dose radiotherapy alone, or concurrent chemoradiation regimens, may contribute to the establishment of a peritumoral proimmunogenic milieu.

The convergence of radiation and immunogenic cell death signaling pathways.

Ionizing radiation (IR) triggers programmed cell death in tumor cells through a variety of highly regulated processes. Radiation-induced tumor cell death has been studied extensively in vitro and is widely attributed to multiple distinct mechanisms, including apoptosis, necrosis, mitotic catastrophe (MC), autophagy, and senescence, which may occur concurrently. When considering tumor cell death in the context of an organism, an emerging body of evidence suggests there is a reciprocal relationship in which radiation stimulates the immune system, which in turn contributes to tumor cell kill. As a result, traditional measurements of radiation-induced tumor cell death, in vitro, fail to represent the extent of clinically observed responses, including reductions in loco-regional failure rates and improvements in metastases free and overall survival. Hence, understanding the immunological responses to the type of radiation-induced cell death is critical. In this review, the mechanisms of radiation-induced tumor cell death are described, with particular focus on immunogenic cell death (ICD). Strategies combining radiotherapy with specific chemotherapies or immunotherapies capable of inducing a repertoire of cancer specific immunogens might potentiate tumor control not only by enhancing cell kill but also through the induction of a successful anti-tumor vaccination that improves patient survival.

Clinical utility of chromogranin A and octreotide in large cell neuro endocrine carcinoma of the uterine corpus.

Primary neuroendocrine tumors of the female genital tract have been described in the cervix, ovaries and uterus. Large cell neuroendocrine carcinoma (LCNC) of the uterine corpus is the least common and appears to behave the most aggressively. We report a rare case of a large cell neuroendocrine tumor of the endometrium. These tumors are not well characterized, unlike neuroendocrine tumors of the uterine cervix. Consequently, the optimal management remains still unclear. The treatment of our case consisted of surgery, radiotherapy, chemotherapy, and octreotide. Despite the aggressive treatment, the patient died of disease progression 12 months after the initial diagnosis. We discuss the diagnosis, prognosis, and treatment options for LCNC of the genital tract, and potential future therapeutics.

Presentation of telomerase reverse transcriptase, a self-tumor antigen, is down-regulated by histone deacetylase inhibition.

Histone deacetylases (HDAC) modify the architecture of chromatin, leading to decreased gene expression, an effect that is reversed by HDAC inhibition. The balance between deacetylation and acetylation is central to many biological events including the regulation of cell proliferation and cancer but also the differentiation of immune T cells. The effects of HDAC inhibition on the interaction between antitumor effector T cells and tumor cells are not known. Here, we studied presentation of a universal self-tumor antigen, telomerase reverse transcriptase, in human tumor cells during HDAC inhibition. We found that HDAC inhibition with trichostatin A was associated with a decreased presentation and diminished killing of tumor cells by CTLs. Using gene array analysis, we found that HDAC inhibition resulted in a decrease of genes coding for proteasome catalytic proteins and for tapasin, an endoplasmic reticulum resident protein involved in the MHC class I pathway of endogenous antigen presentation. Our findings indicate that epigenetic changes in tumor cells decrease self-tumor antigen presentation and contribute to reduced recognition and killing of tumor cells by cytotoxic T lymphocytes. This mechanism could contribute to tumor escape from immune surveillance.

Recombinant tumor-associated MUC1 glycoprotein impairs the differentiation and function of dendritic cells.

Tumors exploit several strategies to evade immune recognition, including the production of a large number of immunosuppressive factors, which leads to reduced numbers and impaired functions of dendritic cells (DCs) in the vicinity of tumors. We have investigated whether a mucin released by tumor cells could be involved in causing these immunomodulating effects on DCs. We used a recombinant purified form of the MUC1 glycoprotein, an epithelial associated mucin that is overexpressed, aberrantly glycosylated, and shed during cancer transformation. The O-glycosylation profile of the recombinant MUC1 glycoprotein (ST-MUC1) resembled that expressed by epithelial tumors in vivo, consisting of large numbers of sialylated core 1 (sialyl-T, ST) oligosaccharides. When cultured in the presence of ST-MUC1, human monocyte-derived DCs displayed a modified phenotype with decreased expression of costimulatory molecules (CD86, CD40), Ag-presenting molecules (DR and CD1d), and differentiation markers (CD83). In contrast, markers associated with an immature phenotype, CD1a and CD206 (mannose receptor), were increased. This effect was already evident at day 4 of DC culture and was dose dependent. The modified phenotype of DCs corresponded to an altered balance in IL-12/IL-10 cytokine production, with DC expressing an IL-10(high)IL-12(low) phenotype after exposure to ST-MUC1. These DCs were defective in their ability to induce immune responses in both allogeneic and autologous settings, as detected in proliferation and ELISPOT assays. The altered DC differentiation and Ag presentation function induced by the soluble sialylated tumor-associated mucin may represent a mechanism by which epithelial tumors can escape immunosurveillance.

Regulated expression of MUC1 epithelial antigen in erythropoiesis.

MUC1 is a large surface glycoprotein expressed by epithelial cells, which is overexpressed and aberrantly glycosylated in carcinomas. MUC1 is involved in epithelial cell interactions and appears to function as a signal-transducing molecule. The finding that MUC1 can also be expressed in the haematopoietic lineages prompted us to further investigate the possible function(s) of this molecule in haematopoietic cells. In bone marrow differentiating cells, MUC1 was strongly and selectively expressed during erythropoiesis; it was also weakly expressed during megakaryocytopoiesis and granulomonocytopoiesis; however, no correlation between MUC1 and differentiation marker expression was observed in these lineages. In vitro CD34+ cells, induced towards erythroid differentiation, acquired MUC1 transiently, while expressing increasing levels of the lineage marker glycophorin A. MUC1 was absent in the circulating erythrocytes. During erythropoiesis, MUC1 expression was transcriptionally regulated and the molecule underwent phosphorylation. To investigate the possible role of MUC1 during erythropoiesis, we studied the ability of MUC1 to act as ligand for cell-cell interaction. The sialylated MUC1 glycoforms selectively expressed on erythroid cells were able to bind the macrophage-restricted molecule sialoadhesin. These results suggest that MUC1 can function as a cross-talk molecule between the erythroblasts and the surrounding cells during erythropoiesis.