Reprogramming of Cancer Cells into Induced Pluripotent Stem Cells Questioned

BACKGROUND AND OBJECTIVES: Several recent studies have claimed that cancer cells can be reprogrammed into induced pluripotent stem cells (iPSCs). However, in most cases, cancer cells seem to be resistant to cellular reprogramming. Furthermore, the underlying mechanisms of limited reprogramming in cancer cells are largely unknown. Here, we identified the candidate barrier genes and their target genes at the early stage of reprogramming for investigating cancer reprogramming.METHODS: We tried induction of pluripotency in normal human fibroblasts (BJ) and both human benign (MCF10A) and malignant (MCF7) breast cancer cell lines using a classical retroviral reprogramming method. We conducted RNA-sequencing analysis to compare the transcriptome of the three cell lines at early stage of reprogramming.RESULTS: We could generate iPSCs from BJ, whereas we were unable to obtain iPSCs from cancer cell lines. To address the underlying mechanism of limited reprogramming in cancer cells, we identified 29 the candidate barrier genes based on RNA-sequencing data. In addition, we found 40 their target genes using Cytoscape software.CONCLUSIONS: Our data suggest that these genes might one of the roadblock for cancer cell reprogramming. Furthermore, we provide new insights into application of iPSCs technology in cancer cell field for therapeutic purposes.

Alteration of Genomic Imprinting Status of Human Parthenogenetic Induced Pluripotent Stem Cells during Neural Lineage Differentiation

BACKGROUND AND OBJECTIVES: Genomic imprinting modulates growth and development in mammals and is associated with genetic disorders. Although uniparental embryonic stem cells have been used to study genomic imprinting, there is an ethical issue associated with the destruction of human embryos. In this study, to investigate the genomic imprinting status in human neurodevelopment, we used human uniparental induced pluripotent stem cells (iPSCs) that possessed only maternal alleles and differentiated into neural cell lineages. METHODS: Human somatic iPSCs (hSiPSCs) and human parthenogenetic iPSCs (hPgiPSCs) were differentiated into neural stem cells (NSCs) and named hSi-NSCs and hPgi-NSCs respectively. DNA methylation and gene expression of imprinted genes related neurodevelopment was analyzed during reprogramming and neural lineage differentiation. RESULTS: The DNA methylation and expression of imprinted genes were altered or maintained after differentiation into NSCs. The imprinting status in NSCs were maintained after terminal differentiation into neurons and astrocytes. In contrast, gene expression was differentially presented in a cell type-specific manner. CONCLUSIONS: This study suggests that genomic imprinting should be determined in each neural cell type because the genomic imprinting status can differ in a cell type-specific manner. In addition, the in vitro model established in this study would be useful for verifying the epigenetic alteration of imprinted genes which can be differentially changed during neurodevelopment in human and for screening novel imprinted genes related to neurodevelopment. Moreover, the confirmed genomic imprinting status could be used to find out an abnormal genomic imprinting status of imprinted genes related with neurogenetic disorders according to uniparental genotypes.

Production of Recombinant Anti-Cancer Vaccines in Plants

Plant expression systems have been developed to produce anti-cancer vaccines. Plants have several advantages as bioreactors for the production of subunit vaccines: they are considered safe, and may be used to produce recombinant proteins at low production cost. However, several technical issues hinder large-scale production of anti-cancer vaccines in plants. The present review covers design strategies to enhance the immunogenicity and therapeutic potency of anti-cancer vaccines, methods to increase vaccine-expressing plant biomass, and challenges facing the production of anti-cancer vaccines in plants. Specifically, the issues such as low expression levels and plant-specific glycosylation are described, along with their potential solutions.

Production of Recombinant Anti-Cancer Vaccines in Plants

Plant expression systems have been developed to produce anti-cancer vaccines. Plants have several advantages as bioreactors for the production of subunit vaccines: they are considered safe, and may be used to produce recombinant proteins at low production cost. However, several technical issues hinder large-scale production of anti-cancer vaccines in plants. The present review covers design strategies to enhance the immunogenicity and therapeutic potency of anti-cancer vaccines, methods to increase vaccine-expressing plant biomass, and challenges facing the production of anti-cancer vaccines in plants. Specifically, the issues such as low expression levels and plant-specific glycosylation are described, along with their potential solutions.

Erratum

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Relationship between ganglioside expression and anti-cancer effects of the monoclonal antibody against epithelial cell adhesion molecule in colon cancer

The human colorectal carcinoma-associated GA733 antigen epithelial cell adhesion molecule (EpCAM) was initially described as a cell surface protein selectively expressed in some myeloid cancers. Gangliosides are sialic acid-containing glycosphingolipids involved in inflammation and oncogenesis. We have demonstrated that treatment with anti-EpCAM mAb and RAW264.7 cells significant inhibited the cell growth in SW620 cancer cells, but neither anti-EpCAM mAb nor RAW264.7 cells alone induced cytotoxicity. The relationship between ganglioside expression and the anti-cancer effects of anti-EpCAM mAb and RAW264.7 was investigated by high-performance thin-layer chromatography. The results demonstrated that expression of GM1 and GD1a significantly increased in the ability of anti-EpCAM to inhibit cell growth in SW620 cells. Anti-EpCAM mAb treatment increased the expression of anti-apoptotic proteins such as Bcl-2, but the expression of pro-apoptotic proteins Bax, TNF-alpha, caspase-3, cleaved caspase-3, and cleaved caspase-8 were unaltered. We observed that anti-EpCAM mAb significantly inhibited the growth of colon tumors, as determined by a decrease in tumor volume and weight. The expression of anti-apoptotic protein was inhibited by treatment with anti-EpCAM mAb, whereas the expression of pro-apoptotic proteins was increased. These results suggest that GD1a and GM1 were closely related to anticancer effects of anti-EpCAM mAb. In light of these results, further clinical investigation should be conducted on anti-EpCAM mAb to determine its possible chemopreventive and/or therapeutic efficacy against human colon cancer.

The roles of glycosphingolipids in the proliferation and neural differentiation of mouse embryonic stem cells

Glycosphingolipids including gangliosides play important regulatory roles in cell proliferation and differentiation. UDP-glucose:ceramide glucosyltransferase (Ugcg) catalyze the initial step in glycosphingolipids biosynthesis pathway. In this study, Ugcg expression was reduced to approximately 80% by short hairpin RNAs (shRNAs) to evaluate the roles of glycosphingolipids in proliferation and neural differentiation of mouse embryonic stem cells (mESCs). HPTLC/immunofluorescence analyses of shRNA-transfected mESCs revealed that treatment with Ugcg-shRNA decreased expression of major gangliosides, GM3 and GD3. Furthermore, MTT and Western blot/immunofluorescence analyses demonstrated that inhibition of the Ugcg expression in mESCs resulted in decrease of cell proliferation (P < 0.05) and decrease of activation of the ERK1/2 (P < 0.05), respectively. To further investigate the role of glycosphingolipids in neural differentiation, the embryoid bodies formed from Ugcg-shRNA transfected mESCs were differentiated into neural cells by treatment with retinoic acid. We found that inhibition of Ugcg expression did not affect embryoid body (EB) differentiation, as judged by morphological comparison and expression of early neural precursor cell marker, nestin, in differentiated EBs. However, RT-PCR/immunofluorescence analyses showed that expression of microtubule- associated protein 2 (MAP-2) for neurons and glial fibrillary acidic protein (GFAP) for glial cells was decreased in neural cells differentiated from the shRNA-transfected mESCs. These results suggest that glycosphingolipids are involved in the proliferation of mESCs through ERK1/2 activation, and that glycosphingolipids play roles in differentiation of neural precursor cells derived from mESCs.