Mucin-1 conjugated polyamidoamine-based nanoparticles for image-guided delivery of gefitinib to breast cancer

PAMAM dendrimers (PAMs) are a group of polymeric macromolecules with distinctive physicochemical features, which can make them multifunctional theranostic nanoparticles (NPs). This study was designed to examine the impact of mucin-1 aptamer-conjugated NPs which were engineered using PAM for image-guided delivery of gefitinib (GEF) in the breast cancer cells/tumor. For this, PAMAM was conjugated with diethylenetriaminepentaacetic acid (DTPA) and modified with PEG2000 to prepare a multi-functionalized NPs. Subsequently, GEF was loaded onto the DTPA-PAM-PEG NPs, which were then armed with MUC-1 aptamer to form the DTPA-PAM-PEG/GEF@MUC-1 nanosystem. Finally, aptamer-conjugated NPs were radiolabeled by gallium-67 as an imaging agent to construct image-guided nanoplatforms. The prepared NPs were characterized by different techniques. The kinetic release models of gefitinib from radiolabeled NPs offer the sustained-release mechanism of the encapsulated drug for over 7 days. In vitro evaluation showed higher cytotoxicity and enhanced uptake of the mucin-grafted NPs in MCF-7 cells. Nuclear medicine imaging and in vivo investigations revealed significant accumulation of ⁶⁷Ga-DTPA-PAM-PEG/GEF@MUC-1 in the tumor site of the animal models. These data suggest that the engineered NPs are a promising image-guided nanosystem for mucin-expressing breast cells/tumors with the assistance of nuclear medicine.

One-Step Self-Assembly of Multifunctional DNA Nanohydrogels: An Enhanced and Harmless Strategy for Guiding Combined Antitumor Therapy

DNA nanostructure-based drug delivery system (DDS) has become an advanced therapeutic strategy for cancer because of its unsurpassed editability, intrinsic biodegradability, and tunable multifunctionality. An intelligent DNA nanosystem integrating targeting, immunostimulation, and chemotherapy was constructed based on unmethylated cytosine-phosphate-guanine oligonucleotides (CpG ODNs) DNA nanohydrogels (CpG-MUC1-hydrogel). By facile one-step self-assembly, the cross-shaped DNAs (C-DNAs) assembled from pH-responsive I-motif sequences and targeted MUC1 aptamer-immunoadjuvant CpG-fused sequences (CpG-MUC1) were integrated into DNA nanohydrogels with controllable size by the hybridization of DNA linkers. Subsequently, DOX was successively intercalated into the base pairs of CpG-MUC1-hydrogel, resulting in CpG-MUC1-hydrogel/Dox that would disassemble and release DOX and CpGs at acidic conditions. After MUC1-mediated internalization, CpG-MUC1-hydrogel/Dox dissociated in the endo/lysosomes and induced favorable apoptosis of tumor cells. Afterward, liberated CpGs triggered vast cytokine secretion from immune cells which elicited potent immune response against malignancy. Notably, CpG-MUC1-hydrogel induced an apoptosis effect on MCF-7 cells via significantly increasing the Bax/Bcl₂ ratios and a higher level of tumor necrosis factor (TNF-α) on RAW264.7 cells than naked CpGs. Our results demonstrated that self-assembled CpG-MUC1-hydrogel represented an attractive DDS for precise delivery, potent immunostimulating activity, and considerable combination efficiency with few adverse effects, which is expected to make breakthroughs in clinical translation.

Detection of breast cancer from blood through analysis of lymphocyte fluorescent intensity using MUC1 antigen

BACKGROUND

Sensitive and reliable early diagnostic markers for breast cancer (BC) are still unavailable today. In this work, we proposed a new complementary method for detection of BC. This method is based on an observation that lymphocytes re-exposed in vitro to antigenic stimulation express cytoplasmic changes.

METHODS

In the new protocol, we recorded changes in the fluorescence intensity of light emitted from lymphocytes obtained from females with and without BC after stimulation with MUC1 antigen utilized flow cytometry.

RESULTS

Out of 55 BC patients tested, 46 were correctly diagnosed. Of 73 controls, 55 were correctly identified as healthy subjects. The sensitivity of the test was 84 %; the specificity was 75 %.

CONCLUSION

These results suggest a potentially valuable method for detection of BC. The clinical importance of this procedure relies on the ability to screen populations for BC with widely available flow cytometry by a relatively fast, accurate, and economical procedure. Another potential benefit would be identification of candidates for vaccination as a primary or secondary preventive measure.

KL-6 regulated the expression of HGF, collagen and myofibroblast differentiation

OBJECTIVES

KL-6 is a pulmonary epithelial-derived mucin which is secreted mainly by type II alveolar epithelial cells. The level of KL-6 in serum is closely correlated to the clinical activity of various interstitial lung diseases (ILD) and acts as a prognostic factor for ILD patients. Previous studies have showed that KL-6 promoted chemotaxis, proliferation and inhibited the apoptosis of human lung fibroblasts. However, the underlying mechanism remains unknown. In this study, we investigated the function of KL-6 on the expression of hepatocyte growth factor (HGF), transforming growth factor-β1 (TGF-β1), collagen and α-smooth muscle actin(α-SMA) in human embryonic lung fibroblasts cell line MRC-5.

METHODS

Human embryonic lung fibroblasts were cultured in Eagle's minimum essential medium. The cells plated in 6-well plates was cultured in serum-free medium at 37°C in 5% CO2 and challenged with recombinant KL-6 at a final concentration of 0, 10, 20, 40 ng/mL. Five micrograms of total RNA template were transcripted to cDNA by using AMV (Avian Myeloblastosis Virus) reverse transcriptase and random 9 mers as the first-strand primer. Synthesized cDNA was used in PCR experiments. The expression of TGF-β1 and HGF in cell culture supernatants was measured using ELISA kit. Cells incubated with KL-6 for 72h were collected for flow-cytometry analysis. The analysis was done using a Beckman counter device.

RESULTS

It was found that KL-6 up-regulated the expression of collagen type I and III in a dose-dependent manner. However, the addition of KL-6 significantly inhibited the production of HGF. As regard to the biological function, KL-6 induced myofibroblast differentiation confirmed by the elevated expression of a-SMA.

CONCLUSIONS

KL-6 is one of the key molecules involved in epithelial-mesenchymal interactions and might contribute to the fibrosis in ILD.

Inhibition of human immunodeficiency virus type 1 activity by purified human breast milk mucin (MUC1) in an inhibition assay

It has been reported that breast-feeding is responsible for approximately 40% of the HIV transmissions from HIV-positive mothers to children. Human breast milk, however, is known to contain numerous biologically active components which protect breast-fed infants against bacteria, viruses, and toxins. The purpose of this study was to purify and characterize breast milk mucin and to determine its anti-HIV-1 activity in an HIV inhibition assay. Sepharose CL-4B column chromatography and caesium chloride isopycnic density gradient purification were used to isolate and purify the mucin. Following Western blotting and amino acid analysis, an HIV-1 inhibition assay was carried out to determine the anti-HIV-1 activity of crude breast milk and purified milk mucin (MUC1) by incubating them with HIV-1 prior to infection of the human T lymphoblastoid cell line (CEM SS cells). SDS-PAGE analysis of the mucin, together with its amino acid composition and Western blotting, suggested that this purified mucin from human breast milk was MUC1. The HIV inhibition assay revealed that while the purified milk mucin (MUC1) inhibited the HIV-1 activity by approximately 97%, there was no inhibition of the HIV-1 activity by crude breast milk. Although the reason for this is not clear, it is likely that because the MUC1 in crude milk is enclosed by fat globules, there may not be any physical contact between the mucin and the virus in the crude breast milk. Thus, there is a need to free the mucin from the fat globules for it to be effective against the virus.

[Prokaryotic expression, purification of HSP65-MUC1 VNTR2 fusion protein and primary research on its tumoricidal effect]

AIM

To express the HSP65-MUC1 VNTR(2) in E.coli and to evaluate its activity of inhibiting tumor growth in vivo.

METHODS

HSP65 and MUC1 VNTR(2) were generated by PCR method and sub-cloned to pET28a(+) to construct the recombinant expression vector HSP65-MUC1 VNTR(2)-pET28a(+). E.coli BL21(DE3) bearing the plasmid was induced with IPTG for protein production. Target protein was characterized by Western blot with monoclonal antibody and purified by Q-Sepharose ion-exchange chromatography and gel filtration. The murine cancer cell linejB16 that transfected by human gene MUC1 was utilized to construct the model of carcinoma, and the tumor growth inhibition activities of HSP65-MUC1VNTR(2) was evaluated in mice C57BL/6.

RESULTS

The gene HSP65 and MUC1 VNTR(2) confirmed by sequence analysis matched respectively with BCG HSP65 and human gene MUC1 VNTRs in GenBank exactly. The reconstructed vector HSP65-MUC1 VNTR(2)-pET28a could express target protein stably in the soluble fraction of bacterial extract. The purity of HSP65-MUC1 VNTR(2) protein could be above 95% after purification by Q ion-exchange chromatography and gel filtration. The result of Western blot with monoclonal antibody showed positive. The results of prophylactic immunization with HSP65-MUC1 VNTR(2) fusion protein showed that experiment all groups had significantly higher tumor inhibition rates than that of control group.

CONCLUSION

In summary, HSP65-MUC1 VNTR(2) fusion protein was solubly expressed in prokaryotic expression system and its tumor growth inhibition activity was evaluated primarily. The result indicated that the fusion protein could inhibit the MUC1 positive tumor growth significantly. It can be used in the future research as the cancer vaccine.

A unique mucin immunoenhancing peptide with antitumor properties

Implantation of DA-3 mammary tumor cells into BALB/c mice results in tumor growth, metastatic lesions, and death. These cells were transfected with genes encoding for either the transmembrane (DA-3/TM) or secreted (DA-3/sec) form of human mucin 1 (MUC1). Although the gene for the secreted form lacks the transmembrane and cytoplasmic domains, the 5' sequences of these mucins are identical; however, the gene for the secreted mucin isoform ends with a sequence encoding for a unique 11 amino acid peptide. The DA-3/TM or DA-3 cells transfected with the neomycin vector only (DA-3/neo) have the same in vivo growth characteristics as the parent cell line. In contrast, DA-3/sec cells fail to grow when implanted in immunocompetent BALB/c animals. DA-3/sec cells implanted in nude mice resulted in tumor development verifying the tumorigenic potential of these cells. Pre-exposure of BALB/c mice to DA-3/sec cells afforded protection against challenge with DA-3/TM or DA-3/neo mammary tumors and the unrelated tumors K7, an osteosarcoma, and RENCA, a renal cell carcinoma. Partial protection against subsequent tumor challenges was also achieved by substituting the 11 amino acid peptide found only in the secreted MUC1 isoform, for the live DA-3/sec cells. Notably, the efficacy of this peptide is not strain restricted because it also retarded the growth of Lewis lung carcinoma cells in C57 BL/6 mice. These findings reveal that a unique peptide present in the secreted MUC1 has immunoenhancing properties and may be a potential agent for use in immunotherapy.

Multistep process through which adenoviral vector vaccine overcomes anergy to tumor-associated antigens

Our goal in the present work was to characterize the multiple steps involved in overcoming the anergy that exists in tumor hosts to tumor-associated antigen (TAA). Our studies showed that the subcutaneous injection of the Ad-sig-TAA/ecdCD40L vector resulted in secretion of the TAA/ecdCD40L protein for at least 10 days from infected cells. Binding of the TAA/ecdCD40L protein to dendritic cells (DCs) resulted in the induction of CCR-7 chemokine receptor expression and cytokine release. This was followed by migration of the DCs to regional lymph nodes. Tetramer staining, enzyme-linked immunospot (ELISPOT) assay, and cytotoxicity assay all showed that the Ad-sig-TAA/ecdCD40L vector increased the levels of splenic CD8+ T cells specific for the 2 TAAs (human MUC1 [hMUC1] and HPV E7) tested. Vaccination with the Ad-sighMUC1/ecdCD40L vector suppressed the growth of hMUC1 antigen-positive tumor cells in 100% of the test mice that were previously anergic to the hMUC1 antigen. These data suggest that Ad-sig-TAA-ecd/ecdCD40L vector injections may be of value in treating the many epithelial malignancies in which TAA-like hMUC1 is overexpressed. (Blood. 2004;104:2704-2713)

Subcellular localization of MUC1 recognized by a monoclonal antibody MY.1E12 correlates with postsurgical prognosis in differentiated-type gastric carcinomas of stage II and III

Because of the complex nature of the diverse histologic grade in gastric carcinomas a useful biomarker should be provided to scale the aggressiveness of the disease and to determine surgical strategy, especially for advanced carcinomas. Our previous study of MUC1 in gallbladder carcinoma using mAb MY.1E12 has revealed the stromal localization of MUC1 adjacent to the carcinoma was correlated with poor prognosis. In gastric carcinoma the biological significance of the localization of MUC1 recognized by mAb MY.1E12 has not been fully investigated. We performed immunohistochemical analysis to determine the correlations with the localization of mAb MY.1E12-reactive-MUC1 (MY.1E12-MUC1) and clinicopathological findings. A total of 91 consecutive patients with stage II, IIIA or IIIB gastric carcinoma after curative resection were reviewed retrospectively. The localization of MY.1E12-MUC1 was classified as negative, apical, cytoplasmic or stromal type based on the predominant subcellular localization. Immunostaining of MY.1E12-MUC1 was recognized in 84% of the 55 cases of differentiated-type carcinoma and in 53% of the 36 cases of undifferentiated-type carcinoma (P<0.01). In differentiated-type carcinoma, the proportion of stromal-type dominant localization of MY.1E12-MUC1 was increased at the deepest invading sites. Postsurgical liver metastasis was seen in 11 (30%) of 37 cases showing stromal or cytoplasmic-type localization-dominant group and in 1 (6%) of 18 cases showing apical-type localization-dominant group or negative staining group (P<0.05). The postsurgical survival was significantly poorer in the former group than in the latter (P=0.004). In differentiated-type gastric carcinoma, the presence of the cytoplasmic- or stromal-type localization of MY.1E12-MUC1 at the deepest invading sites correlates with aggressiveness of the disease, such as the tendency to form liver metastasis. This phenotype may serve as a unique biological feature associated with the malignant behavior of differentiated-type gastric carcinomas.

The importance of MUC1 cellular localization in patients with breast carcinoma: an immunohistologic study of 71 patients and review of the literature

BACKGROUND

The MUC1 mucin is present on the apical surface of normal secretory epithelia. In breast carcinoma, MUC1 expression is variable in amount and cellular localization, the significance of which is controversial. The authors undertook a detailed analysis of staining pattern combined with a comprehensive literature review to better understand the role of MUC1 in breast carcinoma.

METHODS

Seventy-one patients with breast carcinoma were examined for MUC1, beta-catenin, and E-cadherin staining patterns. These data were compared with data from 25 articles from the literature examining the expression of MUC1 in breast carcinoma.

RESULTS

All invasive carcinomas showed some MUC1 staining. In invasive ductal carcinomas, MUC1 was detected in the apical membrane (15%), cytoplasm (93%), or circumferential membrane (13%), with 81% of tumors showing a mixture of patterns. Tumors with low overall MUC1 expression (< or = 50% positive tumor cells) had a higher nuclear grade than tumors with high overall MUC1 expression (> 50%; P = 0.01). Tumors with high and low cytoplasmic expression had no difference in nuclear grade (P > 0.3). Circumferential membrane staining was correlated with positive lymph node status (P = 0.011).

CONCLUSIONS

In the literature, similar findings prevailed in which overall MUC1 expression was increased in lower grade (10 of 14 studies), estrogen receptor positive (8 of 13 studies) tumors and was associated with a better prognosis (8 of 13 studies). High cytoplasmic staining was associated with a worse prognosis, an association that was not explained by differences in histologic grade. Thus, the presence of MUC1 in the majority of tumor cells is associated with better differentiated tumors and with an improved prognosis. However, aberrantly localized MUC1 in the tumor cell cytoplasm or nonapical membrane is associated with a worse prognosis.

Alkyl-lysophospholipid 1-O-octadecyl-2-O-methyl- glycerophosphocholine induces invasion through episialin-mediated neutralization of E-cadherin in human mammary MCF-7 cells in vitro

1-O-octadecyl-2-O-methyl-glycerophosphocholine (ET-18-OMe) is an analogue of the naturally occurring 2-lysophosphatidylcholine belonging to the class of antitumor lipids. Previously, we demonstrated that ET-18-OMe modulates cell-cell adhesion of human breast cancer MCF-7 cells. In the present study, we tested the effect of ET-18-OMe on adhesion, invasion and localisation of episialin and E-cadherin in MCF-7/AZ cells expressing a functional E-cadherin/catenin complex. The MCF-7/6 human breast cancer cells were used as negative control since their E-cadherin/catenin complex is functional in cells grown on solid substrate but not in suspension. The function of E-cadherin, a calcium-dependent transmembrane cell-cell adhesion and signal-transducing molecule, is disturbed in invasive cancers by mutation, loss of mRNA stability, proteolytic degradation, tyrosine phosphorylation of associated proteins and large cell-associated proteoglycans or mucin-like molecules such as episialin. Episialin, also called MUC1, is an anti-adhesion molecule that by its large number of glycosylated tandem repeats can sterically hinder the adhesive properties of other glycoproteins. ET-18-OMe inhibited the E-cadherin functions of MCF-7/AZ cells as measured by inhibition of fast and slow aggregation and by the induction of collagen invasion. These effects were enhanced by MB2, an antibody against E-cadherin and blocked by monoclonal antibodies (MAbs) 214D4 or M8 against episialin. ET-18-OMe had no influence on tyrosine phosphorylation of beta-catenin and the E-cadherin/catenin complex remained intact. Transcription, translation, protein turnover and cell surface localisation of episialin were not altered. ET-18-OMe induced finger-like extensions with clustering of episialin together with E-cadherin and carcinoembryonic antigen but not with occludin. In cells in suspension, ET-18-OMe caused a shift in the flow-cytometric profile of episialin toward a lower intensity for MCF-7/AZ cells. In contrast with MCF-7/AZ cells, the adhesion-deficient and noninvasive MCF-7/6 cells showed neither morphotypic changes nor induction of aggregation nor invasion in collagen I upon treatment with ET-18-OMe. Co-localisation of episialin with E-cadherin was rarely observed. We conclude that in the human breast cancer cells MCF-7/AZ, E-cadherin and episialin are key molecular players in the regulation of promotion and suppression of cell-cell adhesion and invasion.

MUC1 mucin core protein binds to the domain 1 of ICAM-1

BACKGROUND

MUC1 is aberrantly expressed on a variety of epithelial tumors. We have reported that MUC1 plays important roles in separation from primary site, invasion into the stromal tissue, and protection from immune responses. The aim of this study is to determine the precise binding of MUC1 to intercellular adhesion molecule 1 (ICAM-1) that accelerates the cancer metastasis.

METHODS

A cell aggregation assay between MUC1 cDNA transfectants and ICAM-1 expressing cells was employed. An anti-MUC1 antibody, anti-ICAM-1 antibody or synthetic peptide of MUC1 core protein was added to the assay to inhibit the cell aggregation.

RESULTS

MUC1 transfectants showed a significantly higher aggregation rate compared to the control cells. This aggregation was further enhanced by the inhibition of O-glycan biosynthesis. It was inhibited by either an anti-MUC1 antibody recognizing the tandem repeat domain of MUC1 core protein or an anti-ICAM-1 antibody identifying domain 1. It was also inhibited by a synthetic MUC1 peptide of 40 amino acids corresponding to two tandem repeats.

CONCLUSIONS

The results revealed that a tandem repeat domain of MUC1 mucin core protein binds to domain 1 of ICAM-1, suggesting a potential role of MUC1- ICAM-1 interaction in the metastasis of epithelial tumors.

Ex vivo targeting of the macrophage mannose receptor generates anti-tumor CTL responses

MUC1 is highly expressed in adenocarcinomas and is a possible target for immunotherapy. In mice, oxidized mannan linked to MUC1 (M-FP), given in vivo, induces potent MHC-restricted CTL and tumor protection. Because of the resistance of cancer patients to immunization, ex vivo immunization of macrophage/dendritic cells was examined using oxidized mannan MUC1 to target the mannose receptor and the MHC Class I antigen presentation pathway. Here, we show that murine mannose receptor (MR) bearing macrophages derived from peritoneal exudate cells (PEC) and cultured ex vivo with M-FP can, after adoptive transfer, efficiently present MUC1 to T cells, leading to the generation of high frequency of CTL and protection from tumor challenge. Mice immunized once with syngeneic PEC pulsed with M-FP elicit a similar CTLp frequency to that obtained with three in vivo immunizations. Targeting the MR is crucial to obtain high frequency CTL, and without oxidation the CTLp frequency was low. GM-CSF is important, as GM-CSF o/o mice gave reduced responses, a deficiency corrected by in vivo GM-CSF. In addition, the treatment of macrophages ex vivo with GM-CSF gave enhanced responses and treating mice with GM-CSF prior to M-FP immunizations also enhanced cellular responses. M-FP targets the MR and ensures rapid passage of peptides to Class I molecules, and can also directly stimulate in vitro IL-12 production by macrophages. While many studies are now focussing on dendritic cells, in this study the cells involved were adherent F4/80+ 33D1- macrophages. The findings could be of benefit for the immunization of patients with cancer.

The effect of T1 and T2 cytokines on the cytotoxic T cell response to mannan-MUC1

MUC1 is a mucin over-expressed in breast cancer and a proposed target for immunotherapy. By immunising mice with MUC1 conjugated to mannan (M-FP), CD8(+) MHC-class-I restricted cytotoxic T lymphocytes (CTL), of high CTL precursor (CTLp) frequency (1/8000) and with significant tumour protection, can be induced. The effect of various cytokines [interleukin-2 (IL-2), IL-4, IL-6, IL-7, interferon gamma (IFNgamma), and granulocyte/macrophage-colony-stimulating factor (GM-CSF)] on the MUC1 CTL immune response was investigated (a) by measuring the frequencies of CTLp in mice immunised with vaccinia virus constructs containing recombinant cytokines and M-FP, or (b) by immunising cytokine- or cytokine-receptor-knockout (-/-) mice with M-FP. Vaccinia virus (VV) constructs containing recombinant cytokines were used either individually or in combination in vivo with M-FP immunisation. M-FP immunisations combined with VV-IL-2, VV-IL-7 and VV-GM-CSF, and combinations of VV-IFNgamma + VV-IL-2, VV-IFNgamma + VV-IL-4 or VV-GM-CSF + VV-IL-7 increased CTLp frequencies up to threefold (1/17 666: M-FP + VV-GM-CSF + VV-IL-7) compared to M-FP (1/77 500) alone. By contrast, M-FP combined with VV-IL-4 decreased the CTLp frequency threefold whereas VV-IL-6 and VV-IFNgamma had no effect. Studies in cytokine- and cytokine-receptor-gene-knockout (-/-) mice demonstrated that mice that are IL-2 -/- and IL-7 receptor -/- produce the same CTLp response to M-FP as do control mice, whereas responses in the IL-6 -/-, IL-10 -/- and IFNgamma -/- mice were marginally improved and responses to M-FP in IL-4 -/- and tumour necrosis factor receptor 2 -/- mice were weaker. In spite of the increase in CTLp frequency, this was not reflected in an in vivo tumour model. Tumour challenges using MUC1(+) P815 cells, demonstrated that the addition of cytokines had little additive effect on the already effective tumour-regression capabilities of M-FP alone.

Cytotoxic T lymphocytes from humans with adenocarcinomas stimulated by native MUC1 mucin and a mucin peptide mutated at a glycosylation site

MUC1 mucin peptides stimulated cytotoxic T lymphocytes (CTL) from humans with adenocarcinomas. Peripheral blood mononuclear cells, tumor-draining lymph node cells, or tumor-infiltrating lymphocytes were stimulated using mono-nuclear cells from humans with adenocarcinomas of breast or ovary, respectively, using (a) a native MUC1 mucin tandem repeat peptide of 20 amino acids (MUC1-mtr1) plus recombinant human interleukin-2 (IL-2), (b) the mutated (T3N) MUC1-mtr1 plus IL-2, or (c) immobilized anti-CD3 plus IL-2, or (d) IL-2 alone. The CTL stimulated by each of these four conditions were predominately CD4+. However, the CTL stimulated by either the native MUC1-mtr1 or (T3N) MUC1-mtr1 showed 5-10 times greater cytotoxicity of a breast cancer cell line that expresses MUC1 compared to CTL stimulated by either anti-CD3 + IL-2 or IL-2 alone. Each incubation condition generated CTL with different variable beta gene families of T-cell receptors, implying an oligoclonal expansion of a limited CTL repertoire for each. Thus, peptide-stimulated T cells showed expression of cytotoxic cells, which was not induced by nonspecific (anti-CD3 or IL-2) stimulation.

Modulation of CD4 cell cytokine production by colon cancer-associated mucin

PURPOSE

Mucins have been implicated in tumor-associated immunosuppression. The possibility that colon cancer mucin (CCM) may modulate T-helper 1 (TH1) activity was evaluated by investigating its effect on the production of interleukin-2 (IL-2) by CD4+ cells, a process that requires antigen-specific and costimulatory signals.

METHODS

CCM was purified from human colorectal cancer cells by gel-exclusion fast-pressure liquid chromatography. Cytokine production of purified CD4+ cells was evaluated at the protein and gene level in the presence of a phorbol ester or an anti-CD3 monoclonal antibody (mAb) plus mAb against the CD28 costimulatory receptor to mimic two-signal activation.

RESULTS

Soluble CCM, which contains mucins MUC2 as well as MUC1, inhibited IL-2 mRNA expression and secretion of CD4+ stimulated with a phorbol ester or an anti-CD3 mAb plus anti-CD28 mAb. Pretreatment of CD4+ cells with anti-CD28 mAb abrogated the suppressive effects of CCM on IL-2 production, and flow cytometry showed decreased binding of anti-CD28 mAb to its receptor in the presence of mucin. In addition, Ca2+ mobilization after T cell receptor cross-linking with anti-CD3 mAb was maintained in the presence of CCM. Although interferon gamma production was also diminished, CCM did not induce a general inhibition of cytokine production, nor did it decrease cell viability. Macrophage inflammatory protein 1alpha production was up-regulated; the production of IL-10 and transforming growth factor beta was unchanged.

CONCLUSIONS

The results indicate that CCM can alter TH1 activity and suggest that the modulation of costimulatory interactions is involved. They provide another mechanism of immunosuppression mediated by these highly expressed tumor products.

Liposomal formulations of synthetic MUC1 peptides: effects of encapsulation versus surface display of peptides on immune responses

Synthetic human MUC1 peptides are important candidates for therapeutic cancer vaccines. To explore whether a human MUC1 peptide BP25 (STAPPAHGVTSAPDTRPAPGSTAPP) can be rendered immunogenic by incorporation in liposomes, the effects of physical association of the peptide with liposomes on immune responses were investigated. Lipid conjugated and nonconjugated MUC1 peptides were incorporated in liposomes with a composition of distearoylphosphatidylcholine/cholesterol/dimyristoylphosphatidylglyc erol (3:1:0.25, molar ratio) containing monophosphoryl lipid A (1% w/w of the total lipids). Liposomes were characterized for peptide retention by HPLC and for surface peptide display of MUC1 epitopes by flow cytometry. C57BL/6 mice were immunized with lipopeptide alone, peptide mixed with peptide-free liposomes, and peptide associated with liposomes in entrapped or surface-exposed forms. T cell proliferative responses, cytokine patterns, and antibody isotypes were studied. Results showed that immune responses were profoundly influenced by the liposome formulations. Physically associated, either encapsulated or surface-exposed, peptide liposomes elicited strong antigen-specific T cell responses, but not lipopeptide alone or peptide mixed with peptide-free liposomes. Analysis of the cytokines secreted by the proliferating T cells showed a high level of IFN-gamma and undetectable levels of IL-4, indicating a T helper type 1 response. Thus, physical association of the peptide with liposomes was required for T cell proliferative responses, but the mode of association was not critical. On the other hand, the nature of the association significantly affected humoral immune responses. Only the surface-exposed peptide liposomes induced MUC1-specific antibodies. A domination of anti-MUC1 IgG2b over IgG1 (94 versus 6%) was observed. Our results support the hypothesis that different immune pathways are stimulated by different liposome formulations. This study demonstrated that a liposome delivery system could be tailored to induce either a preferential cellular or humoral immune response.

Increased invasiveness of MUC1 and cDNA-transfected human gastric cancer MKN74 cells

MUC1 mucin is an anti-adhesion molecule expressed in a wide variety of tumors. To examine whether MUC1 mucin is involved in tumor invasion, we have prepared MUC1 transfectants using the human gastric cancer cell line MKN74 and performed an in vivo tumor assay by transplanting these into nude mice. Tumor weight at 71 days after s.c. injection of transfectants was measured, showing that the in vivo growth of MUC1 transfectants was increased compared to that of mock transfectants. Furthermore, MUC1-transfectant tumors invaded into the muscle layer, whereas mock-transfectant tumors did not. In vitro invasion, adhesion to extracellular matrix components and phagokinetic track motility were then evaluated to analyze the mechanisms for the in vivo invasiveness of the transfectants. MUC1 transfectants exhibited an increased in vitro invasiveness, decreased binding to laminin, fibronectin, type I collogen and type IV collagen and increased motility. These effects of MUC1 mucin over-expression in MKN74 cells were abolished by the treatment of transfectants with an inhibitor of O-glycan biosynthesis, benzyl-alpha-GalNAc. Our data suggest that MUC1 mucin could be related to the increased invasive ability of MKN74 cells, whereas O-glycan might play an essential role.

Intercellular and intracellular events following the MHC-unrestricted TCR recognition of a tumor-specific peptide epitope on the epithelial antigen MUC1

We examined the functional and molecular parameters involved in direct TCR recognition of a tumor-specific peptide epitope on the tumor Ag MUC1. This peptide epitope is tandemly repeated and recognized on the native molecule rather than processed and bound to the MHC. Even though the TCR was not MHC restricted, intercellular interactions found to facilitate this recognition included intercellular adhesion molecule-1/LFA-1, LFA-3/CD2, and class I/CD8. Intracellular parameters of MHC-unrestricted CTL activation were examined to compare the recognition of the MUC1 epitope presented on synthetic microspheres, with the recognition of the native epitope in the context of other molecules on the target cells. The epitope on microspheres induced a transient influx of Ca2+ that was not accompanied by detectable tyrosine phosphorylation of the zeta-associated protein ZAP-70, whereas recognition of MUC1 epitopes on tumor cells caused a sustained Ca2+ influx and ZAP-70 phosphorylation. The transient influx of Ca2+ was not sufficient to cause translocation of the nuclear factor of activated T cells (NF-AT) into the nucleus or CTL proliferation. In contrast, recognition of the MUC1 epitope on tumor cells resulted in full activation of the CTL, nuclear translocation of NF-AT, and proliferation. MHC-unrestricted TCR triggering, therefore, involves similar intercellular and intracellular events that participate in the conventional, MHC-restricted Ag recognition. Direct recognition of the MUC1 peptide epitope by the TCR in the absence of presentation by the MHC induces a partial signal that is completed by further interactions of other receptor/ligand pairs on the surface of the CTL and their target cells.

Cancer-associated MUC1 mucin inhibits human T-cell proliferation, which is reversible by IL-2

A number of adenocarcinomas abundantly express and secrete underglycosylated MUC1 mucin. Underglycosylation exposes tandem repeat peptide sequences on cancer-associated MUC1 mucin that are normally cryptic. High levels of MUC1 mucin are correlated with a poor prognosis and immunosuppression in adenocarcinoma patients. In this report we show that cancer-associated MUC1 mucin, affinity-purified from ascites fluids of cancer patients, and synthetic tandem repeats of MUC1 mucin core peptide can suppress human T-cell proliferative responses. This MUC1 mucin-induced suppression of T-cell responses can be reversed by the addition of exogenous IL-2 or anti-CD28 monoclonal antibody. These results are consistent with other studies showing that lymphocytes present in the vicinity of tumor cells are anergic and can be reactivated with exogenous interleukin-2. Overcoming MUC1 mucin-induced immunosuppression with IL-2 combined with active specific immunotherapy might be an effective immunotherapeutic strategy against human adenocarcinomas.

Effect of MUC1 mucin, an anti-adhesion molecule, on tumor cell growth

MUC1 mucin is expressed in a wide variety of tumors and is considered to function as an anti-adhesion molecule which inhibits cell-to-cell interactions. To reveal the biological significance of this activity in tumor cells, MUC1 cDNA was transfected into EJNIH3T3 cells and human colon cancer cell lines, CHCY1 and DLD1. The in vivo growth rate of MUC1+ (MUC1-transfected) EJNIH3T3, CHCY1 and DLD1 cells in SCID mice was clearly lower than that of MUC1- (mock transfectant) cells. Several in vitro experiments using MUC1+ EJNIH3T3 cells were performed to analyze the mechanisms for the decreased in vivo tumor growth. It was found that (i) the in vitro growth rate of MUC1+ EJNIH3T3 cells was also decreased compared to that of MUC1- cells, (ii)the DNA synthesis of MUC1+ EJNIH3T3 cells after stimulation with either growth factor (fetal calf serum or bombesin) or extracellular matrix (collagen or fibronectin) was lower than that of MUC1- cells, and (iii) MUC1+ EJNIH3T3 cells grew more slowly than MUC1- cells on both collagen- and fibronectin-coated dishes. These data suggest that MUC1 mucin may regulate tumor cell growth through inhibition of cell-to-cell, growth factor-to-receptor and cell-to-matrix interactions.