Ho Park

Exosomes from ovarian cancer cells induce adipose tissue-derived mesenchymal stem cells to acquire the physical and functional characteristics of tumor-supporting myofibroblasts

OBJECTIVE Most tumor tissue is composed of parenchymal tumor cells and tumor stroma. Mesenchymal stem cells (MSCs) can function as precursors for tumor stromal cells, including myofibroblasts, which provide a favorable environment for tumor progression. A close relationship between tumor cells and MSCs in a tumor microenvironment has been described. Exosomes are small membrane vesicles that are enriched with a discrete set of cellular proteins, and are therefore expected to exert diverse biological functions according to cell origin. METHODS In the current study, we determined the biological effect of exosomes from two ovarian cancer cell lines (SK-OV-3 and OVCAR-3) on adipose tissue-derived MSCs (ADSCs). RESULTS Exosome treatment induced ADSCs to exhibit the typical characteristics of tumor-associated myofibroblasts, with increased expression of α-SMA, and also increased expression of tumor-promoting factors (SDF-1 and TGF-β). This phenomenon was correlated with an increased expression of TGF-β receptors I and II. Analysis of TGF-β receptor-mediated downstream signaling pathways revealed that each exosome activated different signaling pathways, showing that exosomes from SK-OV-3 cells increased the phosphorylated form of SMAD2, which is essential in the SMAD-dependent pathway, whereas exosomes from OVCAR-3 cells increased the phosphorylated form of AKT, a representative SMAD-independent pathway. Taken together, exosomes from ovarian cancer cells induced the myofibroblastic phenotype and functionality in ADSCs by activating an intracellular signaling pathway, although the activated pathway could differ from exosome-to-exosome. CONCLUSION The current study suggested that ovarian cancer-derived exosomes contribute to the generation of tumor-associated myofibroblasts from MSCs in tumor stroma.

Mitotic catastrophe is the predominant response to histone acetyltransferase depletion

Histone acetylation induces chromatin opening by perturbing higher-order chromatin compaction and folding, suggesting that histone acetylation and deacetylation dynamics are central to chromosome condensation or decondensation. The condensation of chromosomes during mitosis is an essential prerequisite for successful chromosome segregation. In this study, we depleted three representative histone acetyltransferases (HATs; p300, CBP, and P/CAF) using shRNAs to explore their role in regulating mitotic progression and chromosome segregation. We showed that HAT depletion severely interfered with the normal timing of mitotic progression, and it reduced condensin subunit levels. The predominant response to HAT depletion, in both human primary and cancer cells, was a mitotic catastrophe following aberrant mitotic arrest. Alternatively, adaptation to HAT depletion, particularly in cancer cells, led to multinucleation and aneuploidy. Interestingly, mitotic catastrophe induced by HAT depletion appeared to be coupled to the signaling process of H2AX phosphorylation and foci formation, independently of DNA double-strand breaks and DNA damage. Taken together, our results provide novel molecular evidence that HAT proteins maintain mitotic chromatin assembly and integrity as a cellular determinant of mitotic cell death.

Hyperthermia-treated mesenchymal stem cells exert antitumor effects on human carcinoma cell line†

Mesenchymal stem cells (MSCs) possess the potential for differentiation into multilineages. MSCs have been reported to play a role as precursors for tumor stroma in providing a favorable environment for tumor progression. Hyperthermia destroys cancer cells by raising the temperature of tumor‐loaded tissue to 40°C to 43°C and causes indirect sensitizing effects when combined with chemo‐ and/or radiotherapy. However, how hyperthermia affects the tumor‐supportive stroma is unknown. Here, the authors investigated the effects of hyperthermia‐treated MSCs, from different sources, on the human ovarian cancer cell line SK‐OV‐3.

Vocal fold wound healing after injection of human adipose-derived stem cells in a rabbit model

Abstract Conclusion: Injection of injured rabbit vocal folds with human adipose-derived stem cells (hADSCs) led to improved wound healing and fewer signs of scarring as demonstrated by a decreased collagen content in the treated folds compared with the untreated folds. hADSCs remained viable for up to 12 weeks in rabbit vocal folds. Objective: The aim of this study was to investigate the morphologic and histologic properties of scarred rabbit vocal folds following injection of hADSCs. Methods: This was a randomized, controlled animal study. Twenty-four vocal folds from 12 New Zealand rabbits were scarred using a CO2 laser and injected with either hADSCs (left vocal fold) or phosphate-buffered saline (right vocal fold). Every 4 weeks for the first 12 weeks after injection, an endoscopic examination was performed to assess the morphology of the vocal folds. Twelve weeks later the animals were euthanized and the tissues were stained for histology. Results: In comparison with the right vocal folds, there was significantly less granulation tissue in the hADSCs-injected left vocal folds (p < 0.05). Histological examination revealed excessive collagen deposition and perichondral fibrosis in the right vocal folds, whereas the left vocal folds exhibited better wound healing and less collagen deposition (p < 0.05). Among the 12 specimens injected with hADSCs, 4 specimens demonstrated viable hADSCs under immunofluorescent cytochemistry.

Cell cycle regulators are critical for maintaining the differentiation potential and immaturity in adipogenesis of adipose-derived stem cells.

A single cell division is governed by the catalytic reactions of cyclins and cyclin-dependent kinases (CDKs). Stem cells are unique in that they can differentiate into tissue-specific cell types (lineage commitment) during cell division (self-renewal). In this study, we analyzed changes in the differentiation potency of adipose tissue-derived stem cells (ADSCs) according to the number of spontaneous cell divisions. We used low passage number (p3) to late passage number (p60) adipose-derived stem cells (ADSCs) as our model system. A preliminary investigation of the typical stem cell phenotypes revealed that CD44 expression decreased remarkably as the passage number of the ADSCs increased. Further examinations revealed that the higher the cell passage number, the lower the cell proliferation capability, differentiation potency, and expression of stem cell transcriptional factors and cell cycle regulators such as cyclins E, A, B, CDK2, and CDK1/CDC2. To verify if the observed changes in differentiation potency according to the number of cell divisions were related to cell cycle regulators, p3 ADSCs were treated with the selective CDK2 and CDK1/CDC2 inhibitor Purvalanol A. Inhibitor treatment of p3 ADSCs induced changes in the morphology, differentiation potency, and pattern of stem cell transcriptional factor expression so that these low passage ADSCs more closely resembled high-passage ADSCs. Collectively, our results indicate that cell cycle regulators control the differentiation potency of ADSCs, and provide insights into the cell biology and differentiation potency of ADSCs according to the number of cell divisions.

Cyclin-dependent kinase 4 signaling acts as a molecular switch between syngenic differentiation and neural transdifferentiation in human mesenchymal stem cells.

Multipotent mesenchymal stem/stromal cells (MSCs) are capable of differentiating into a variety of cell types from different germ layers. However, the molecular and biochemical mechanisms underlying the transdifferentiation of MSCs into specific cell types still need to be elucidated. In this study, we unexpectedly found that treatment of human adipose- and bone marrow-derived MSCs with cyclin-dependent kinase (CDK) inhibitor, in particular CDK4 inhibitor, selectively led to transdifferentiation into neural cells with a high frequency. Specifically, targeted inhibition of CDK4 expression using recombinant adenovial shRNA induced the neural transdifferentiation of human MSCs. However, the inhibition of CDK4 activity attenuated the syngenic differentiation of human adipose-derived MSCs. Importantly, the forced regulation of CDK4 activity showed reciprocal reversibility between neural differentiation and dedifferentiation of human MSCs. Together, these results provide novel molecular evidence underlying the neural transdifferentiation of human MSCs; in addition, CDK4 signaling appears to act as a molecular switch from syngenic differentiation to neural transdifferentiation of human MSCs.

Roles of 14-3-3η in mitotic progression and its potential use as a therapeutic target for cancers.

14-3-3 proteins are involved in several cellular processes, including the G1/S and G2/M cell cycle transitions. However, their roles during mitosis are not well understood. Here, we showed that depletion of 14-3-3η, a 14-3-3 protein isoform, enhanced mitotic cell death, resulting in sensitization to microtubule inhibitors and inhibition of aneuploidy formation. The enhanced mitotic cell death by depletion of 14-3-3η appeared to be both caspase-dependent and independent. Furthermore, enhanced mitotic cell death and a reduction in aneuploidy following 14-3-3η depletion were independent of the mitotic checkpoint, which is thought to be the primary signaling event in the regulation of the cell death induced by microtubule inhibitors. When 14-3-3η depletion was combined with microtubule inhibitors in HCT116 and U87MG cells, it sensitized both cancer cell lines to microtubule inhibitors. These results collectively suggest that 14-3-3η may be required for mitotic progression and may be considered as a novel anti-cancer strategy in combination with microtubule inhibitors.