Graphitic Carbon Nitride Causes Widespread Global Molecular Changes in Epithelial and Fibroblast Cells

For scaffold and imaging applications, nanomaterials such as graphene and its derivatives have been widely used. Graphitic carbon nitride (g-C₃N₄) is among one such derivative of graphenes, which draws strong consideration due to its physicochemical properties and photocatalytic activity. To use g-C₃N₄ for biological applications, such as molecular imaging or drug delivery, it must interact with the epithelium, cross the epithelial barrier, and then come in contact with the extracellular matrix of the fibroblast cells. Thus, it becomes essential to understand its molecular mechanism of action. Hence, in this study, to understand the molecular reprogramming associated with g-C₃N₄, global gene expression using DNA microarrays and proteomics using tandem mass tag (TMT) labeling and mass spectrometry were performed in epithelial and fibroblast cells, respectively. Our results showed that g-C₃N₄ can cross the epithelial barrier by regulating the adherens junction proteins. Further, using g-C₃N₄-PDMS scaffolds as a mimic of the extracellular matrix for fibroblast cells, the common signaling pathways were identified between the epithelium and fibroblast cells. These pathways include Wnt signaling, integrin signaling, TGF-β signaling, cadherin signaling, oxidative stress response, ubiquitin proteasome pathway, and EGF receptor signaling pathways. These altered signature pathways identified could play a prominent role in g-C₃N₄-mediated cellular interactions in both epithelial and fibroblast cells. Additionally, β catenin, EGFR, and MAP2K2 protein-protein interaction networks could play a prominent role in fibroblast cell proliferation. The findings could further our knowledge on g-C₃N₄-mediated alterations in cellular molecular signatures, enabling the potential use of these materials for biological applications such as molecular imaging and drug delivery.

Synthesis of saporin-antibody conjugates for targeting EpCAM positive tumour cells

Epithelial cell adhesion molecule (EpCAM) is a transmembrane glycoprotein involved in cell proliferation and differentiation. Ribosomal inactivating proteins derived from plants specifically target ribosomes and irreversibly inhibit protein synthesis. EpCAM antibody and saporin were conjugated using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide chemistry. The mass of the conjugates were characterised using matrix-assisted laser desorption ionisation (MALDI). The saporin-EpCAM (SAP-EpAB) conjugates were tested in-vitro against MCF-7 (breast cancer cells), WERI-Rb1 (retinoblastoma) cells. The flow cytometry and fluorescence microscopy were performed to show the binding efficiency of SAP-EpAB conjugate. Whole transcriptome changes of sap-conjugate treated cells were studied using affymetrix microarrays. MALDI-TOF analysis and polyacrylamide gel electrophoresis confirmed the conjugation of SAP with EpCAM antibody. Flow cytometry and fluorescent microscopy analysis revealed the binding of SAP-EpAB conjugates to the MCF-7, WERI-Rb1 cells. Apoptosis assay by annexin-V has shown an increased apoptotic and necrotic population in conjugate treated cells. MTT assay confirmed the tumour cell death and had shown the IC₅₀ value of 0.8 µg for conjugate in MCF-7 (breast cancer cells), and 1 µg for WERI-Rb1 (retinoblastoma) cells. The microarray analysis revealed downregulation of the tumourigenic genes and upregulation of pro-apoptotic genes leading to apoptosis of tumour cells.

Neocarzinostatin, Aptamer Conjugates for Targeting EpCAM-positive Tumor Cells

BACKGROUND/AIM

The aim of this study was to investigate the role of Neocarzinostatin (NCS) conjugated with epithelial cell adhesion molecule (EpCAM) aptamer in EpCAM-positive cancer cells. NCS is an antitumor antibiotic protein chromophore that has the ability to cleave double stranded DNA and can be used as a potential drug for the treatment of EpCAM-positive cancers. EpCAM aptamer is an oligonucleotide ligand that binds specifically to EpCAM, a protein overexpressed in tumor cells.

MATERIALS AND METHODS

NCS was conjugated with EpCAM aptamer using Sulfo-Succinimidyl 6-(3-(2-pyridyldithio) - propionamide hexanoate) LC-(SPDP) cross-linker to deliver it to EpCAM-positive tumor cells. The conjugates were characterized using polyacrylamide gel electrophoresis (PAGE) and high-performance liquid chromatography (HPLC). Flow cytometry was used to study the binding efficiency of the aptamer and the conjugates in cancer cells. The effect of the conjugate on cancer cells was studied using propidium iodide (PI) to analyze the cell cycle phase changes. The apoptosis assay was performed using the IC₅₀ concentration of NCS. Microarrays were performed to study the gene level changes in cancer cells upon treatment with NCS and the conjugate.

RESULTS

Flow cytometry revealed significant binding of aptamer and conjugate in the MCF-7 and WERI-Rb1 cell lines. Briefly, 62% in MCF and 30% in WERI-Rb1 cells with conjugate treated cells (p<0.005). The cell-cycle analysis indicated G₂ phase arrest in MCF-7 cells and S phase arrest in WERI-Rb1 cells (p<0.005). Microarray analysis showed differentially expressed genes involved in cell cycle, DNA damage, and apoptosis. The BrDU assay and the apoptosis assay showed that the expression of BrDU was reduced in conjugate-treated cells and the PARP levels were increased confirming the double stranded DNA breaks (p<0.005). In MCF-7 and WERI-Rb1 cells, most of the cells underwent necrosis (p<0.005).

CONCLUSION

The EpCAM aptamer conjugated NCS showed specificity to EpCAM-positive cells. The effect of the conjugates on cancer cells were impressive as the conjugate arrested the cell cycle and promoted apoptosis and necrosis. The high levels of PARP expression confirmed the DNA breaks upon conjugate treatment. Our study demonstrates that the NCS conjugated with EpCAM can be targeted to cancer cells sparing normal cells.