Transferrin receptor is a marker of malignant phenotype in human pancreatic cancer and in neuroendocrine carcinoma of the pancreas

Automated selection of regions of interest for intensity-based FRET analysis of transferrin endocytic trafficking in normal vs. cancer cells

The overexpression of certain membrane-bound receptors is a hallmark of cancer progression and it has been suggested to affect the organization, activation, recycling and down-regulation of receptor-ligand complexes in human cancer cells. Thus, comparing receptor trafficking pathways in normal vs. cancer cells requires the ability to image cells expressing dramatically different receptor expression levels. Here, we have presented a significant technical advance to the analysis and processing of images collected using intensity based Förster resonance energy transfer (FRET) confocal microscopy. An automated Image J macro was developed to select region of interests (ROI) based on intensity and statistical-based thresholds within cellular images with reduced FRET signal. Furthermore, SSMD (strictly standardized mean differences), a statistical signal-to-noise ratio (SNR) evaluation parameter, was used to validate the quality of FRET analysis, in particular of ROI database selection. The Image J ROI selection macro together with SSMD as an evaluation parameter of SNR levels, were used to investigate the endocytic recycling of Tfn-TFR complexes at nanometer range resolution in human normal vs. breast cancer cells expressing significantly different levels of endogenous TFR. Here, the FRET-based assay demonstrates that Tfn-TFR complexes in normal epithelial vs. breast cancer cells show a significantly different E% behavior during their endocytic recycling pathway. Since E% is a relative measure of distance, we propose that these changes in E% levels represent conformational changes in Tfn-TFR complexes during endocytic pathway. Thus, our results indicate that Tfn-TFR complexes undergo different conformational changes in normal vs. cancer cells, indicating that the organization of Tfn-TFR complexes at the nanometer range is significantly altered during the endocytic recycling pathway in cancer cells. In summary, improvements in the automated selection of FRET ROI datasets allowed us to detect significant changes in E% with potential biological significance in human normal vs. cancer cells.

Ligand-mediated endocytosis of nanoparticles in neural stem cells: implications for cellular magnetic resonance imaging

Neural stem cells (NSCs) have great prospects in therapy for neurological disorders. However, the correlation between improved function and stem cell transplantation has not been fully elucidated. A non-invasive method for stem cell tracking is crucial for clinical studies. In the present study, NSCs were infected with lentiviral vectors, and the expression of transferrin receptor (TfR) in neural stem cells after lentivirus transfection (TfR-NSC) was confirmed by western blot analysis. TfR-NSCs were incubated with 1.8 nM ultra-small super-paramagnetic iron oxide nanoparticles (USPIOs) or transferrin (Tf)-conjugate of USPIO nanoparticles (Tf-USPIOs). Tf-USPIO enhanced the cellular iron content in TfR-NSCs 80 ± 18 % compared to USPIOs. These results demonstrated that TfR overexpressed in neural stem cells specifically internalized Tf-USPIOs. Furthermore, the results indicate that TfR reporter imaging may be a valuable way to evaluate the efficacy of neural stem cell treatment.

Lipidosterolic extract of serenoa repens modulates the expression of inflammation related-genes in benign prostatic hyperplasia epithelial and stromal cells

Despite the high prevalence of histological Benign Prostatic Hypeplasia (BPH) in elderly men, little is known regarding the molecular mechanisms and networks underlying the development and progression of the disease. Here, we explored the effects of a phytotherapeutic agent, Lipidosterolic extract of the dwarf palm plant Serenoa repens (LSESr), on the mRNA gene expression profiles of two representative models of BPH, BPH1 cell line and primary stromal cells derived from BPH. Treatment of these cells with LSESr significantly altered gene expression patterns as assessed by comparative gene expression profiling on gene chip arrays. The expression changes were manifested three hours following in vitro administration of LSESr, suggesting a rapid action for this compound. Among the genes most consistently affected by LSESr treatment, we found numerous genes that were categorized as part of proliferative, apoptotic, and inflammatory pathways. Validation studies using quantitative real-time PCR confirmed the deregulation of genes known to exhibit key roles in these biological processes including IL1B, IL1A, CXCL6, IL1R1, PTGS2, ALOX5, GAS1, PHLDA1, IL6, IL8, NFkBIZ, NFKB1, TFRC, JUN, CDKN1B, and ERBB3. Subsequent analyses also indicated that LSESr treatment can impede the stimulatory effects of certain proinflammatory cytokines such as IL6, IL17, and IL15 in these cells. These results suggest that LSESr may be useful to treat BPH that manifest inflammation characteristics. This also supports a role for inflammation in BPH presumably by mediating the balance between apoptosis and proliferation.

Targeting polymeric fluorescent nanodiamond-gold/silver multi-functional nanoparticles as a light-transforming hyperthermia reagent for cancer cells

This work demonstrates a simple route for synthesizing multi-functional fluorescent nanodiamond-gold/silver nanoparticles. The fluorescent nanodiamond is formed by the surface passivation of poly(ethylene glycol) bis(3-aminopropyl) terminated. Urchin-like gold/silver nanoparticles can be obtained via one-pot synthesis, and combined with each other via further thiolation of nanodiamond. The morphology of the nanodiamond-gold/silver nanoparticles thus formed was identified herein by high-resolution transmission electron microscopy, and clarified using diffraction patterns. Fourier transform infrared spectroscopy clearly revealed the surface functionalization of the nanoparticles. The fluorescence of the materials with high photo stability was examined by high power laser irradiation and long-term storage at room temperature. To develop the bio-recognition of fluorescent nanodiamond-gold/silver nanoparticles, pre-modified transferrin was conjugated with the gold/silver nanoparticles, and the specificity and activity were confirmed in vitro using human hepatoma cell line (J5). The cellular uptake analysis that was conducted using flow cytometry and inductively coupled plasma mass spectrometry exhibited that twice as many transferrin-modified nanoparticles as bare nanoparticles were engulfed, revealing the targeting and ease of internalization of the human hepatoma cell. Additionally, the in situ monitoring of photothermal therapeutic behavior reveals that the nanodiamond-gold/silver nanoparticles conjugated with transferrin was more therapeutic than the bare nanodiamond-gold/silver materials, even when exposed to a less energetic laser source. Ultimately, this multi-functional material has great potential for application in simple synthesis. It is non-cytotoxic, supports long-term tracing and can be used in highly efficient photothermal therapy against cancer cells.

Transferrin receptor targeting nanomedicine delivering wild-type p53 gene sensitizes pancreatic cancer to gemcitabine therapy

To overcome gene therapy barriers such as low transfection efficiency and nonspecific delivery, liposomal nanoparticles targeted by a single-chain antibody fragment to the transferrin receptor (TfRscFv) delivering wild-type (wt) human p53 (SGT-53) were developed for tumor-specific targeting. We hypothesize that SGT-53 in combination with gemcitabine will demonstrate enhanced therapeutic benefit in an in vivo metastatic pancreatic cancer model. Intrasplenic injection of 1 × 10(6) Panc02 murine pancreatic cancer cells was used to generate in vivo hepatic metastatic tumors. Nanoparticle localization was assessed by tail vein injection of TfRscFv with fluorescently labeled oligonucleotides (6-carboxyfluorescein phosphoramidite (6FAM) ODN) imaged by Xenogen IVIS 200 scan. SGT-53 (equivalent to 30 μg of p53 intravenously) and gemcitabine (20 mg/kg intraperitoneally) alone and in combination were administered biweekly and compared with untreated mice. Survival was determined by blinded daily assessment of morbidity. Human wtp53 expression and transferrin levels in the tumors were assessed by western blot analysis. Tumor burden was quantified by liver weight. Xenogen imaging demonstrated tumor-specific uptake of TfRscFv-6FAM ODN. Exogenous human wtp53 protein was detected in the SGT-53-treated tumors compared with control. Compared with untreated mice with metastatic tumors demonstrating median survival of 20 days, SGT-53, gemcitabine and the combination demonstrated improved median survival of 29, 30 and 37 days, respectively. The combination treatment prolonged median survival when compared with single drug treatment and decreased tumor burden. The tumor targeting liposomal-based SGT-53 nanoparticle is capable of sensitizing pancreatic cancer to conventional chemotherapy in pancreatic cancer models. This approach has the potential to be translated into a new, more effective therapy for pancreatic cancer. Further optimization is ongoing, moving towards a Phase 1B/2 clinical trial.

Advances in magnetic resonance molecular and functional imaging to diagnose pancreatic cancer

Pancreatic cancer has a high mortality rate, which is generally related to the initial diagnosis coming at late stage disease combined with a lack of effective diagnostic techniques. Over the past few years, molecular-functional imaging, which can be defined as the in vivo characterization and measurement of biologic processes at the molecular and gene levels, has developed rapidly and allows diagnosing pancreatic cancer more early and specifically. Magnetic resonance (MR) imaging is widely used for molecular imaging because of the high spatial resolution. This paper reviews recent advances in MR molecular and functional imaging to diagnose pancreatic cancer.

Magnetoferritin nanoparticles for targeting and visualizing tumour tissues

Engineered nanoparticles have been used to provide diagnostic, therapeutic and prognostic information about the status of disease. Nanoparticles developed for these purposes are typically modified with targeting ligands (such as antibodies, peptides or small molecules) or contrast agents using complicated processes and expensive reagents. Moreover, this approach can lead to an excess of ligands on the nanoparticle surface, and this causes non-specific binding and aggregation of nanoparticles, which decreases detection sensitivity. Here, we show that magnetoferritin nanoparticles (M-HFn) can be used to target and visualize tumour tissues without the use of any targeting ligands or contrast agents. Iron oxide nanoparticles are encapsulated inside a recombinant human heavy-chain ferritin (HFn) protein shell, which binds to tumour cells that overexpress transferrin receptor 1 (TfR1). The iron oxide core catalyses the oxidation of peroxidase substrates in the presence of hydrogen peroxide to produce a colour reaction that is used to visualize tumour tissues. We examined 474 clinical specimens from patients with nine types of cancer and verified that these nanoparticles can distinguish cancerous cells from normal cells with a sensitivity of 98% and specificity of 95%.

Engineered viral nanoparticles for flow cytometry and fluorescence microscopy applications

Viral nanoparticles (VNPs) are attractive platforms for use in the biotechnology and biomedical fields because of their biological nature. A wide variety of these particles, labeled with fluorescent reporters, have been characterized using flow cytometry and cellular imaging techniques. Fluorescence microscopy allows the direct observation of VNPs on the cell surface or inside the membrane as well as the cellular localization of the nanoparticles while flow cytometry allows the statistical quantification of nanoparticle uptake and targeting specificity. These techniques are essential when characterizing the properties of VNPs and provide information toward the use of VNPs for targeting, imaging, and/or cargo delivery.

Inactivation of MYO5B promotes invasion and motility in gastric cancer cells

BACKGROUND

Loss of cell polarity and tissue disorganisation are hallmarks of cancer. MYO5B mutations disrupt epithelial cell polarity, suggesting that MYO5B may be involved in tumorigenesis.

METHODS

We analyzed MYO5B expression in 70 gastric cancer tissues by immunohistochemistry using a tissue microarray method. Two related proteins, Rab11a and TfR, were also investigated.

RESULTS

We found that the negative rate of MYO5B was 78.6 and 17.1% in gastric cancer and normal gastric tissues (P < 0.001), respectively. The MYO5B expression had a strong relationship with Rab11a expression (P = 0.002). We also found that inactivation by siRNA against MYO5B promoted the proliferation, invasion and migration of gastric cancer cells.

CONCLUSION

The expression of MYO5B was downregulated in gastric cancer and inactivation of MYO5B may contribute to tumorigenesis. Therefore, MYO5B may become an important biomarker for gastric cancer in the future.

Genome-wide linkage analysis of Swedish families to identify putative susceptibility loci for cutaneous malignant melanoma

Cutaneous malignant melanoma is a clinically and genetically heterogeneous disorder which is caused by an interaction between hereditary and environmental factors. In Sweden, a small portion of the inherited susceptibility is explained by the presence of germline mutations in the tumor suppressor gene CDKN2A. But still, the genetic background of melanoma susceptibility is largely unknown. Here, we conducted a genome-wide linkage scan on melanoma-prone families using high-density single-nucleotide polymorphisms (SNPs) arrays to identify novel melanoma susceptibility genes. We investigated 35 families of Swedish origin without CDKN2A mutations. Nonparametric and parametric multipoint linkage analyses were performed. After removal of SNPs in strong linkage disequilibrium, the strongest evidence of linkage was detected on chromosome 17p11-12 (logarithm (base 10) of odds (LOD) scores of 2.76) using parametric linkage analysis assuming a dominant trait with full penetrance. Analyses were also performed on a subset of families with low age at diagnosis (mean age ≤ 47 years), to obtain a more homogenous subset. This subgroup analysis based on 22 families yielded suggestive evidence of linkage to the chromosomal regions 11p12-p11 and 18q22 (multipoint LOD scores of 2.10 and 2.02, respectively). Also, the 17p region that was detected in the complete family set showed suggestive linkage in this cohort (multipoint LOD scores of 2.01). Our data suggest that these chromosomal regions, 17p12-p11 in particular as it was present in both analyses, may harbor genes involved in the susceptibility of malignant melanoma in the Swedish population.

An anti-transferrin receptor antibody enhanced the growth inhibitory effects of chemotherapeutic drugs on human glioma cells

Transferrin receptor (TfR) has been used as a target for antibody-based therapy of cancer. Anti-TfR antibody together with chemotherapeutic drugs has potential for cancer therapy. In this study, we investigated the in vitro anti-tumor effects of the anti-TfR monoclonal antibody (mAb), 7579, alone or in combination with Nimustine, a chemotherapeutic drug, on the gliomas cell lines U251 and U87MG. Our results indicated that 7579 alone dramatically down-regulated surface expression of TfR on tumor cells and induced S phase accumulation and apoptosis of tumor cells. Compared with 7579 or Nimustine used alone, the combination of 7579 with Nimustine demonstrated enhanced growth inhibitory effect on tumor cells. PI (Propidium iodide)/Annexin V staining analyzed by FCM (flow cytometry) demonstrated that 7579 enhanced the cytotoxic effects of chemotherapeutic drug on tumor cells, indicating the therapeutic effect of 7579 was mediated mainly by promoting tumor cell necrosis. Using the median-effect/combination-index isobologram method, we further evaluated the nature of 7579/chemotherapeutic drug interactions. Synergistic interaction was observed for combination of 7579 with Nimustine. Our study provides additional evidence to develop combination therapies of anti-TfR mAbs-plus chemoimmunotherapy for gliomas.

Synthesis of biomolecule-modified mesoporous silica nanoparticles for targeted hydrophobic drug delivery to cancer cells

Synthetic methodologies integrating hydrophobic drug delivery and biomolecular targeting with mesoporous silica nanoparticles are described. Transferrin and cyclic-RGD peptides are covalently attached to the nanoparticles utilizing different techniques and provide selectivity between primary and metastatic cancer cells. The increase in cellular uptake of the targeted particles is examined using fluorescence microscopy and flow cytometry. Transferrin-modified silica nanoparticles display enhancement in particle uptake by Panc-1 cancer cells over that of normal HFF cells. The endocytotic pathway for these particles is further investigated through plasmid transfection of the transferrin receptor into the normal HFF cell line, which results in an increase in particle endocytosis as compared to unmodified HFF cells. By designing and attaching a synthetic cyclic-RGD, selectivity between primary cancer cells (BT-549) and metastatic cancer cells (MDA-MB 435) is achieved with enhanced particle uptake by the metastatic cancer cell line. Incorporation of the hydrophobic drug Camptothecin into these two types of biomolecular-targeted nanoparticles causes an increase in mortality of the targeted cancer cells compared to that caused by both the free drug and nontargeted particles. These results demonstrate successful biomolecular-targeted hydrophobic drug delivery carriers that selectively target specific cancer cells and result in enhanced drug delivery and cell mortality.

Aberrant expression of TfR1/CD71 in thyroid carcinomas identifies a novel potential diagnostic marker and therapeutic target

BACKGROUND

Type I receptor for transferrin (TfR1/CD71) is overexpressed in several malignant tumors, but no studies are available on thyroid carcinomas. Our previous comparative analyses of the relative distribution of transferrin in benign versus papillary thyroid carcinoma (PTC) tissues highlighted a marked malignancy-associated abundance of the molecule. The aim of the present study was to evaluate whether TfR1/CD71 is also differentially expressed in benign versus malignant thyroid tissues.

METHODS

Tissue samples, including benign lesions and follicular-derived carcinomas, from 241 patients and a total of 35 benign and malignant fresh specimens were assayed for TfR1/CD71 expression by reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemistry.

RESULTS

We found that transcription of TfR1/CD71 gene is constitutive in thyroid epithelia, but the mRNA is differently translated in benign and malignant tissues. Western blot revealed higher levels of TfR1/CD71 protein in malignant versus benign tissues. Immunohistochemically, most carcinomas exhibited overexpression of the receptor, predominantly in the cytoplasm of neoplastic cells. The highest expression level was detected in primary and metastatic papillary carcinomas and anaplastic carcinomas, with positive results ranging from 86% to 100% of the cases. In contrast, most benign tissues were negative, with only a minority of cases showing focal and weak immunoreactivity.

CONCLUSIONS

Our findings suggest that altered expression of TfR1/CD71 may be used as a marker helpful in distinguishing PTC from papillary hyperplasia and follicular variant PTC from benign follicular-patterned lesions. Additionally, the present observations support the rationale for the use of radiolabeled transferrin/transferrin analogs and/or anti-TfR1/CD71 antibodies for diagnostic and/or radiotherapeutic purposes in TfR1/CD71-expressing thyroid tumors.

Proteomic identification of salivary transferrin as a biomarker for early detection of oral cancer

Oral cancer has a low five-year survival rate. Early detection of oral cancer could reduce the mortality and morbidity associated with this disease. Saliva, which can be sampled non-invasively and is less complex than blood, is a good potential source of oral cancer biomarkers. Proteomic analysis of saliva from oral cancer patients and control subjects was performed to identify salivary biomarkers of early stage oral cancer in humans. The protein profile of pooled salivary samples from patients with oral squamous cell carcinoma (OSCC) or OSCC-free control subjects was analyzed using two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. Potential biomarkers were verified by Western blotting and ELISA assays. Transferrin levels were elevated in the saliva of OSCC patients as determined using 2DE followed by MALDI-TOF MS and confirmed by MALDI-TOF/TOF MS, Western blotting and ELISA. The increase in salivary transferrin levels in OSCC patients strongly correlated with the size and stage of the tumor. The area under the receiver-operating characteristics curves showed that salivary transferrin-based ELISA was highly specific, sensitive and accurate for the early detection of oral cancer. We have identified salivary transferrin as a biomarker for the detection of early stage oral cancer. This finding provides a promising basis for the development of a non-invasive diagnostic test for early stage oral cancer.

Chemistry and biology of the caged Garcinia xanthones

Natural products have been a great source of many small molecule drugs for various diseases. In spite of recent advances in biochemical engineering and fermentation technologies that allow us to explore microorganisms and the marine environment as alternative sources of drugs, more than 70 % of the current small molecule therapeutics derive their structures from plants used in traditional medicine. Natural-product-based drug discovery relies heavily on advances made in the sciences of biology and chemistry. Whereas biology aims to investigate the mode of action of a natural product, chemistry aims to overcome challenges related to its supply, bioactivity, and target selectivity. This review summarizes the explorations of the caged Garcinia xanthones, a family of plant metabolites that possess a unique chemical structure, potent bioactivities, and a promising pharmacology for drug design and development.

Multivalent display and receptor-mediated endocytosis of transferrin on virus-like particles

The structurally regular and stable self-assembled capsids derived from viruses can be used as scaffolds for the display of multiple copies of cell- and tissue-targeting molecules and therapeutic agents in a convenient and well-defined manner. The human iron-transfer protein transferrin, a high affinity ligand for receptors upregulated in a variety of cancers, has been arrayed on the exterior surface of the protein capsid of bacteriophage Qbeta. Selective oxidation of the sialic acid residues on the glycan chains of transferrin was followed by introduction of a terminal alkyne functionality through an oxime linkage. Attachment of the protein to azide-functionalized Qbeta capsid particles in an orientation allowing access to the receptor binding site was accomplished by the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction. Transferrin conjugation to Qbeta particles allowed specific recognition by transferrin receptors and cellular internalization through clathrin-mediated endocytosis, as determined by fluorescence microscopy on cells expressing GFP-labeled clathrin light chains. By testing Qbeta particles bearing different numbers of transferrin molecules, it was demonstrated that cellular uptake was proportional to ligand density, but that internalization was inhibited by equivalent concentrations of free transferrin. These results suggest that cell targeting with transferrin can be improved by local concentration (avidity) effects.

Viral specific cytotoxic T cells inhibit the growth of TfR-expressing tumor cells with antibody targeted viral peptide/HLA-A2 complex

A fusion protein of single chain antibody (scFv) specific for transferrin receptor (TfR, CD71) and viral peptide/HLA-A2 complex was prepared in this study to redirect cytotoxic T cells (CTLs) of viral specificity to tumor cells by attaching the ligand of T cell receptor (TCR) to tumor cells via binding of TfR scFv to TfR. The results demonstrate that the fusion protein can attach the active virus-peptide/HLA-A2 complex to HLA class I-negative, TfR-expressing K562 cells through binding of TfR scFv to TfR, and mediate cytotoxicity of viral peptide-specific CTLs against K562 cells in vitro. In addition, the fusion protein can induce inhibition of solid tumor formation and improve survival time in tumor xenograft nude mouse with the injection of the sorted viral peptide-specific CTLs generated by co-culture of peripheral blood lymphocytes from HLA-A2 positive donors with inactivated T2 cells pulsed with the viral peptide.

Preparation and quality test of superparamagnetic iron oxide labeled antisense oligodeoxynucleotide probe: a preliminary study

Molecular imaging of tumor antisense gene techniques have been applied to the study of magnetic resonance (MR) gene imaging associated with malignant tumors. In this study, we designed, synthesized, and tested a novel molecular probe, in which the antisense oligodeoxynucleotide (ASODN) was labeled with superparamagnetic iron oxide (SPIO), and its efficiency was examined by in vitro MR imaging after SK-Br-3 mammary carcinoma cell lines (oncocytes) transfection. The SPIO-labeled ASODN probe was prepared through SPIO conjugated to ASODN using a chemical cross linking method. Its morphology and size were detected by atomic force microscope, size distribution were detected by laser granulometer, the conjugating rate and biological activity were determined by high performance liquid chromatography, and the stability was determined by polyacrylamide gel electrophoresis. After that, the probes were transfected into the SK-Br-3 oncocytes, cellular iron uptake was analyzed qualitatively at light and electron microscopy and was quantified at atomic absorption spectrometry, and the signal change of the transfected cells was observed and measured using MR imaging. The morphology of the SPIO-labeled ASODN probe was mostly spherical with well-distributed scattering, and the diameters were between 25 and 40 nm (95%) by atomic force microscope and laser granulometer, the conjugating rate of the probe was 99%. Moreover, this probe kept its activity under physiological conditions and could conjugate with antisense oligodeoxynucleotide. In addition, light microscopy revealed an intracellular uptake of iron oxides in the cytosol and electron microscopic studies revealed a lysosomal deposition of iron oxides in the transfected SK-Br-3 oncocytes by antisense probes, some of them gathered stacks, and the iron content of the group of transfected SK-Br-3 oncocytes by antisense probe is significantly higher (18.37 +/- 0.42 pg) than other contrast groups, the MR imaging showed that transfected SK-Br-3 oncocytes by antisense probe had the lowest signal of all. The SPIO-labeled ASODN probe shows unique features including well-distributed spherical morphology, high conjugating rate and loading efficiency, and the signal intensity of SPIO-labeled ASODN-transfected SK-Br-3 oncocytes is reduced in MR imaging. These results indicate that the SPIO-labeled ASODN probe is potentially useful as a MR targeting contrast enhancing agent to specifically diagnose tumors which had over-expression of the c-erbB2 oncogene at an early stage.

Tumor targeting using canine parvovirus nanoparticles

Advances in genetics, proteomics and cellular and molecular biology are being integrated and translated to develop effective methods for the prevention and control of cancer. One such combined effort is to create multifunctional nanodevices that will specifically recognize tumors and thus enable early diagnosis and provide targeted treatment of this disease. Viral particles are being considered for this purpose since they are inherently nanostructures with well-defined geometry and uniformity, ideal for displaying molecules in a precise spatial distribution at the nanoscale level and subject to greater structural control. Viruses are presumably the most efficient nanocontainer for cellular delivery as they have naturally evolved mechanisms for binding to and entering cells. Virus-based systems typically require genetic or chemical modification of their surfaces to achieve tumor-specific interactions. Interestingly, canine parvovirus (CPV) has a natural affinity for transferrin receptors (TfRs) (both of canine and human origin) and this property could be harnessed as TfRs are overexpressed by a variety of human tumor cells. Since TfR recognition relies on the CPV capsid protein, we envisioned the use of virus or its shells as tumor targeting agents. We observed that derivatization of CPV virus-like particles (VLPs) with dye molecules did not impair particle binding to TfRs or internalization into human tumor cells. Thus CPV-based VLPs with a natural tropism for TfRs hold great promise in the development of novel nanomaterial for delivery of a therapeutic and/or genetic cargo.

Transferrin receptor (CD71) is a marker of poor prognosis in breast cancer and can predict response to tamoxifen

Transferrin receptor (CD71) is involved in the cellular uptake of iron and is expressed on cells with high proliferation. It may be implicated in promoting the growth of endocrine resistant phenotypes within ER+/luminal-like breast cancer. We used a panel of in vitro cell models of acquired resistance to tamoxifen (TAMR), Faslodex (FASR) or severe oestrogen deprivation (MCF-7X) and the ER+ luminal MCF-7 parental line to determine CD71 mRNA expression and to study transferrin (Tf) effects on in vitro tumour growth and its inhibition. Furthermore, CD71 protein expression was assessed in a well-characterized series of patients with invasive breast carcinoma using tissue microarrays. Our results demonstrated a striking elevation of CD71 in all cell models of acquired resistance. Exogenous Tf significantly promoted growth in MCF-7-X and MCF-7 cells but more so in MCF-7-X; this growth was significantly reduced by Faslodex (FAS) or a phosphoinositide-3 kinase inhibitor (LY294002). Increased CD71 expression was associated with poor NPI score, tumour proliferation, basal CKs, p53, EGFR, HER2, steroid receptor negativity and shortened breast cancer specific survival (P < 0.001). On multivariate analysis, CD71 was found to be an independent prognostic factor in the ER+ cohort of patients. In conclusion, therapies of current interest in breast cancer (e.g. FAS, PI3K-inhibitors) appear able to partially impact on transferrin/CD71-promoted growth, but further investigation of this important mitogenic mechanism may assist in designing new therapeutic strategies to target highly proliferative, endocrine resistant breast cancers. CD71 appears to be a candidate marker of a subgroup of ER+/luminal-like breast cancer characterised by poor outcome and resistance to tamoxifen.

An anti-transferrin receptor antibody enhanced the growth inhibitory effects of chemotherapeutic drugs on human non-hematopoietic tumor cells

Transferrin receptor (TfR) has been used as a target for antibody-based therapy of cancer. Combining anti-TfR antibodies with chemotherapeutic drugs shows potential as one of the strategies for cancer therapy. In this study, we investigated the effects of anti-TfR monoclonal antibody 7579 alone or in combination with chemotherapeutic drugs (5-fluorouracil or doxorubicin) on non-hematopoietic tumor cells (HepG2 and MCF-7) in vitro. We found that 7579 mAb alone could dramatically down-regulate surface TfR expression on tumor cells. Consequently, marked S phase arrest and apoptosis were observed in 7579 mAb-treated tumor cells. In combination with 5-fluorouracil or doxorubicin, 7579 mAb enhanced the growth inhibitory effects of chemotherapeutic drugs on tumor cells. Results of 7AAD/Annexin V staining demonstrated that 7579 mAb enhanced the cytotoxic effects of chemotherapeutic drugs on tumor cells by mainly promoting tumor cell necrosis. Using the median-effect/combination-index isobologram method, we further evaluated the nature of 7579 mAb/chemotherapeutic drug interactions. Synergistic interaction was observed for 7579 mAb combined with 5-fluorouracil whereas additive efficacy was observed for 7579 mAb plus doxorubicin. Our study provided the basis to further develop 7579 mAb-containing chemoimmunotherapy for non-hematopoietic malignancies.

Differential apoptotic induction of gambogic acid, a novel anticancer natural product, on hepatoma cells and normal hepatocytes

Gambogic acid (GA) is the major active ingredient of gamboge, a brownish resin exuded from Garcinia hanburryi tree in Southeast Asia. In this study, we compared the different apoptotic induction of GA on human normal embryonic hepatic L02 cells and human hepatoma SMMC-7721 cells by detecting growth inhibition, observing morphological changes, and the expressions of the relative apoptotic proteins (Bax, Bcl-2 and caspase-3). The results indicated that GA could selectively induce apoptosis of SMMC-7721 cells, while had relatively less effect on L02 cells. To illustrate the distinct selective antitumor mechanism of GA, we further study its distribution in cultured cells and in tumor-bearing mice. The results indicated that SMMC-7721 cells have higher GA binding activity than L02 cells. The retention time of GA in grafted tumor was longer than in liver, renal and other organs. Collectively, the selective anticancer activity of GA could be due to its significant apoptotic inducing effects as well as its higher distribution and longer retention time in tumor cells compared to the normal cells. So GA might be a kind of highly effective anticancer drug candidate with low toxicity to normal tissue.

Preparation of adriamycin liposome coupled with HTf(Fe)2 and its anti-tumor activity on human hepatoma cell line SMMC-7721

AIM: To modify the adriamycin (ADM) liposome with transferrin HTf(Fe)₂ according to the difference of receptor or antigen expression between tumor cells and normal cells, and study its efficacy of anti-tumor activities on human hepatoma cell line SMMC-7721.

METHODS: Cross-linking reagent (SPDP) reacting with human transferrin HTf(Fe)₂ was utilized, and liposomes coupled with transferrin [named as HTf(Fe)₂-ADM-liposome] were prepared. Then human hepatoma cell line SMMC-7721 was treated with different concentrations of HTf(Fe)₂-ADM-liposome and MTT assay was used to the killing effect on SMMC-7721 cells.

RESULTS: The success rate of HTf(Fe)₂ coupling with liposomes was 73.5%. Electron microscopy showed no significant difference in the diameters between HTf(Fe)₂-ADM-liposome and ADM-liposome (56 ± 38 nm vs 54 ± 30 nm, P < 0.05). Modification and coupling didn't affect the activity of HTf(Fe)₂. The specific cytotoxicities of HTf(Fe)₂-ADM-liposome, ADM-liposome and free ADM on SMMC-7721 cells were 64.52%, 22.12% and 37.82%, respectively, and there were marked difference between the former and the latter two (P < 0.05).

CONCLUSION: The anti-tumor activity of HTf(Fe)₂-ADM-liposome on SMMC-7721 cells in vitro shows a high potency and specificity and a minimal dosage is able to achieve this effect.

A list of candidate cancer biomarkers for targeted proteomics

We have compiled from literature and other sources a list of 1261 proteins believed to be differentially expressed in human cancer. These proteins, only some of which have been detected in plasma to date, represent a population of candidate plasma biomarkers that could be useful in early cancer detection and monitoring given sufficiently sensitive specific assays. We have begun to prioritize these markers for future validation by frequency of literature citations, both total and as a function of time. The candidates include proteins involved in oncogenesis, angiogenesis, development, differentiation, proliferation, apoptosis, hematopoiesis, immune and hormonal responses, cell signaling, nucleotide function, hydrolysis, cellular homing, cell cycle and structure, the acute phase response and hormonal control. Many have been detected in studies of tissue or nuclear components; nevertheless we hypothesize that most if not all should be present in plasma at some level. Of the 1261 candidates only 9 have been approved as "tumor associated antigens" by the FDA. We propose that systematic collection and large-scale validation of candidate biomarkers would fill the gap currently existing between basic research and clinical use of advanced diagnostics.

Prevention of Mantle Lymphoma Tumor Establishment by Routing Transferrin Receptor toward Lysosomal Compartments

Mantle cell lymphoma (MCL) is one of the most frequent of the newly recognized non-Hodgkin's lymphomas. The major problem of MCL therapy is the occurrence of relapse and subsequent resistance to chemotherapy and immunotherapy in virtually all cases. Here, we show that one injection of anti-human transferrin receptor (TfR) monoclonal antibody A24 totally prevented xenografted MCL tumor establishment in nude mice. It also delayed and inhibited tumor progression of established tumors, prolonging mice survival. In vitro, A24 induced up to 85% reduction of MCL cell proliferation (IC(50) = 3.75 nmol/L) independently of antibody aggregation, complement-dependent or antibody-dependent cell-mediated cytotoxicity. A24 induced MCL cell apoptosis through caspase-3 and caspase-9 activation, either alone or synergistically with chemotherapeutic agents. A24 induced TfR endocytosis via the clathrin adaptor protein-2 complex pathway followed by transport to lysosomal compartments. Therefore, A24-based therapies alone or in association with classic chemotherapies could provide a new alternative strategy against MCL, particularly in relapsing cases.

Ultravlolet-B induced expression of hypoxia-inducible factor 1α, transferrin receptor through EGFR/PI3K/AKT/DEC1 pathway

The aim of this research was to explore the effects and signaling pathway of ultraviolet-B (UVB) irradiation on the expression of hypoxia-inducible factor 1α (HIF-1α) and transferrin receptor (TfR). HIF-1α protein was measured by Western blot method. Expressions of epidermal growth factor receptor (EGFR), phosphor-EGF-R and TfR after UVB irradiation were determined with flow cytometry. After UVB irradiation, mRNA levels of HIF-1α and TfR were detected by real time-PCR. Results showed that compared with control groups, UVB was able to induce HIF1α and TfR protein expression in a dose-and time-dependent manner in HaCat cells (P < 0.05). TfR mRNA was expressed in a dose-dependent manner and reached a peak at the 8th hour in HaCat cells (P < 0.05) whereas HIF-1α mRNA expression was not affected by UVB treatment (P>0.05). The EGFR/PI3K/AKT signaling pathway was required for the induction of HIF-1α and TfR expression induced by UVB. UVB induced activation of EGFR in HaCat cells and EGFR regulated expression of TfR and HIF-1α. EGFR (-/-) MEF did not increase the HIF1 expression following UVB irradiation (P>0.05). In contrast, EGFR (+/+) MEF strongly enhanced HIF1α expression after UVB irradiation (P < 0.05). PD153035, a selective inhibitor of EGFR tyrosine kinase, inhibited the TfR protein expression in UVB-treated cells in a dose-dependent manner (P < 0.05). PI3K inhibitors, LY294002 and wortmannin, inhibited HIF-1α and TfR expressions induced by UVB (P < 0.05). The DEC1 (-/-) HaCat cells did not increase their TfR and HIF-1α expressions following UVB irradiation (P>0.05). In contrast, DEC1 (+/+) HaCat cells strongly enhanced TfR and HIF-1α protein expression after UVB irradiation (P < 0.05). We conclude that UVB induces TfR and HIF-1α expressions via EGFR/PI3K/AKT/DEC1 signaling pathway.

Canine parvovirus-like particles, a novel nanomaterial for tumor targeting

Specific targeting of tumor cells is an important goal for the design of nanotherapeutics for the treatment of cancer. Recently, viruses have been explored as nano-containers for specific targeting applications, however these systems typically require modification of the virus surface using chemical or genetic means to achieve tumor-specific delivery. Interestingly, there exists a subset of viruses with natural affinity for receptors on tumor cells that could be exploited for nanotechnology applications. For example, the canine parvovirus (CPV) utilizes transferrin receptors (TfRs) for binding and cell entry into canine as well as human cells. TfRs are over-expressed by a variety of tumor cells and are widely being investigated for tumor-targeted drug delivery. We explored whether the natural tropism of CPV to TfRs could be harnessed for targeting tumor cells. Towards this goal, CPV virus-like particles (VLPs) produced by expression of the CPV-VP2 capsid protein in a baculovirus expression system were examined for attachment of small molecules and delivery to tumor cells. Structural modeling suggested that six lysines per VP2 subunit are presumably addressable for bioconjugation on the CPV capsid exterior. Between 45 and 100 of the possible 360 lysines/particle could be routinely derivatized with dye molecules depending on the conjugation conditions. Dye conjugation also demonstrated that the CPV-VLPs could withstand conditions for chemical modification on lysines. Attachment of fluorescent dyes neither impaired binding to the TfRs nor affected internalization of the 26 nm-sized VLPs into several human tumor cell lines. CPV-VLPs therefore exhibit highly favorable characteristics for development as a novel nanomaterial for tumor targeting.

Unbiased Examination of Changes in Plasma Membrane Proteins in Drug Resistant Cancer Cells

In this study, an unbiased examination is made of the abundance changes between proteins found in the basolateral plasma membranes of a drug susceptible parental MCF-7 breast cancer cell line and a cell line selected from the parent line for resistance to the anticancer drug mitoxantrone. Plasma membrane proteins were differentially labeled metabolically, enriched using the colloidal silica pellicle method, and characterized by tandem mass spectrometry. Fifteen proteins were identified with significant (>2) changes, including receptors, adhesion proteins, proteins involved in amino acid uptake, and proteins involved in glucose uptake. From 40 mug of membrane proteins, 3227 unique peptides and 540 proteins were identified.

Accelerated Bioorthogonal Conjugation: A Practical Method for the Ligation of Diverse Functional Molecules to a Polyvalent Virus Scaffold

Covalent bond formation to proteins is made difficult by their multiple unprotected functional groups and normally low concentrations. A water-soluble sulfonated bathophenanthroline ligand (2) was used to promote a highly efficient Cu(I)-mediated azide-alkyne cycloaddition (CuAAC) reaction for the chemoselective attachment of biologically relevant molecules to cowpea mosaic virus (CPMV). The ligated substrates included complex sugars, peptides, poly(ethylene oxide) polymers, and the iron carrier protein transferrin, with routine success even for cases that were previously resistant to azide-alkyne coupling using the conventional ligand tris(triazolyl)amine (1). The use of 4-6 equiv of substrate was sufficient to achieve loadings of 60-115 molecules/virion in yields of 60-85%. Although it is sensitive to oxygen, the reliably efficient performance of the Cu.2 system makes it a useful tool for demanding bioconjugation applications.

Altered iron metabolism, transferrin receptor 1 and ferritin in patients with colon cancer

In this study, the level and distribution of transferrin receptor 1 (TfR1) and ferritin in colorectal carcinoma and in normal colon epithelium has been determined relative to the tumor stage and iron status of patients using immunohistochemical staining methods. While the majority of carcinoma patients were anemic, no relationship between the level of colon tissue ferritin and TfR1 and the systemic parameters of iron metabolism was evident. Furthermore, no association between ferritin content and the grade of colorectal carcinoma was observed. However, a relationship between the expression of TfR1 and the grade of colorectal carcinoma was observed. In this case high expression of TfR1 was found in colorectal carcinoma samples of Dukes A or B grade, and well differentiated colorectal carcinoma cells. In comparison, weak or no expression of TfR1 was observed in carcinoma samples of Dukes C or D grade with poorly differentiated cells and in carcinoma samples that had lymph node infiltration and distant metastasis.

A role for transferrin receptor in triggering apoptosis when targeted with gambogic acid

Transferrin receptor (TfR) has been shown to be significantly overexpressed in different types of cancers. We discovered TfR as a target for gambogic acid (GA), used in traditional Chinese medicine and a previously undiscovered link between TfR and the rapid activation of apoptosis. The binding site of GA on TfR is independent of the transferrin binding site, and it appears that GA potentially inhibits TfR internalization. Down-regulation of TfR by RNA interference decreases sensitivity to GA-induced apoptosis, further supporting TfR as the primary GA receptor. In summary, GA binding to TfR induces a unique signal leading to rapid apoptosis of tumor cells. These results suggest that GA may provide an additional approach for targeting the TfR and its use in cancer therapy.

Metastases-related genes in the classification of liver and peritoneal metastasis in human gastric cancer

INTRODUCTION

With the aim of identifying metastases-related genes in gastric cancer, we performed a broad analysis of differential gene expression between low-metastatic parental cell lines and established highly metastatic sublines.

MATERIALS AND METHODS

We established novel cell lines, AZ-H5c, NUGC-3H5, and TMK-1H7, with a high potential of liver metastasis, and AZ-P7a, NUGC-3P4T, and TMK-1P4a, with a high potential of peritoneal metastasis. These cell lines were derived from low-metastatic parental AZ-521, NUGC-3, and TMK-1 cell lines, respectively. Furthermore, to investigate different levels of gene expression implicated in metastatic potentials in gastric cancer, we investigated approximately 2000 expressed genes in each cell line using a DNA microarray.

RESULTS

Varieties of genes were up-regulated or down-regulated in highly metastatic liver and peritoneal cell lines. Fifty-eight genes, including the transferrin receptor, ras-related rho, and osteopontin, and 22 genes, including apolipoprotein E and inhibin A-submit, were up-regulated and down-regulated in two or three liver metastatic sublines. On the other hand, 19 genes, the transferrin receptor, c-fos, and RANTES, and 26 genes, including MAC25, PISSLRE, and RNA polymerase, were up-regulated and down-regulated in two or three peritoneal metastatic sublines.

CONCLUSION

How gene expression is implicated in gastric cancer metastasis has never been thoroughly explained, and further studies are necessary to understand the involvement of genes in cancer metastasis more thoroughly. We hope that our highly metastatic liver and peritoneal experimental models are helpful for further study and gene therapy of human gastric cancer.