Connexin46 Expression Enhances Cancer Stem Cell and Epithelial-to-Mesenchymal Transition Characteristics of Human Breast Cancer MCF-7 Cells

Connexins (Cxs) are a family of proteins that form two different types of ion channels: hemichannels and gap junction channels. These channels participate in cellular communication, enabling them to share information and act as a synchronized syncytium. This cellular communication has been considered a strong tumor suppressor, but it is now recognized that some type of Cxs can be pro-tumorigenic. For example, Cx46 expression is increased in human breast cancer samples and correlates with cancer stem cell (CSC) characteristics in human glioma. Thus, we explored whether Cx46 and glioma cells, can set up CSC and epithelial-to-mesenchymal transition (EMT) properties in a breast cancer cell line. To this end, we transfected MCF-7 cells with Cx46 attached to a green fluorescent protein (Cx46GFP), and we determined how its expression orchestrates both the gene-expression and functional changes associated with CSC and EMT. We observed that Cx46GFP increased Sox2, Nanog, and OCT4 mRNA levels associated with a high capacity to form monoclonal colonies and tumorspheres. Similarly, Cx46GFP increased the mRNA levels of n-cadherin, Vimentin, Snail and Zeb1 to a higher migratory and invasive capacity. Furthermore, Cx46GFP transfected in MCF-7 cells induced the release of higher amounts of VEGF, which promoted angiogenesis in HUVEC cells. We demonstrated for the first time that Cx46 modulates CSC and EMT properties in breast cancer cells and thus could be relevant in the design of future cancer therapies.     

Endothelium-Dependent Induction of Vasculogenic Mimicry in Human Triple-Negative Breast Cancer Cells Is Inhibited by Calcitriol and Curcumin

In highly aggressive tumors, cancer cells may form channel-like structures through a process known as vasculogenic mimicry (VM). VM is generally associated with metastasis, mesenchymal phenotype, and treatment resistance. VM can be driven by antiangiogenic treatments and/or tumor microenvironment-derived factors, including those from the endothelium. Curcumin, a turmeric product, inhibits VM in some tumors, while calcitriol, the most active vitamin D metabolite, exerts potent antineoplastic effects. However, the effect of these natural products on VM in breast cancer remains unknown. Herein, we studied the effect of both compounds on triple-negative breast cancer (TNBC) VM-capacity in a co-culture model. The process of endothelial cell-induced VM in two human TNBC cell lines was robustly inhibited by calcitriol and partially by curcumin. Calcitriol promoted TNBC cells’ morphological change from spindle-like to cobblestone-shape, while curcumin diminished VM 3D-structure. Notably, the treatments dephosphorylated several active kinases, especially those involved in the PI3K/Akt pathway. In summary, calcitriol and curcumin disrupted endothelium-induced VM in TNBC cells partially by PI3K/Akt inactivation and mesenchymal phenotype inhibition. Our results support the possible use of these natural compounds as adjuvants for VM inactivation in patients with malignant tumors inherently capable of forming VM, or those with antiangiogenic therapy, warranting further in vivo studies.     

Propolin G-Suppressed Epithelial-to-Mesenchymal Transition in Triple-Negative Breast Cancer Cells via Glycogen Synthase Kinase 3β-Mediated Snail and HDAC6-Regulated Vimentin Degradation

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer with a poor prognosis. The incidence and mortality rate of TNBC are frequently found in younger women. Due to the absence of a good therapeutic strategy, effective remedies for inhibiting TNBC have been developed for improving the cure rate. Epithelial-to-mesenchymal transition (EMT) is a critical mechanism to regulate cancer cell motility and invasion. Furthermore, ectopic expression of EMT molecules correlates with the metastasis and poor prognosis of TNBC. Targeting EMT might be a strategy for the therapy and prevention of TNBC. Propolin G, an active c-prenylflavanone in Taiwanese propolis, has been shown to possess anti-cancer activity in many cancers. However, the anti-metastasis activity of propolin G on TNBC is still unclear. The present study showed that the migration and invasion activities of TNBC cells was suppressed by propolin G. Down-regulated expression of Snail and vimentin and up-regulated expression of E-cadherin were dose- and time-dependently observed in propolin G-treated MDA-MB-231 cells. Propolin G inhibited Snail and vimentin expressions via the signaling pathways associated with post-translational modification. The activation of glycogen synthase kinase 3β (GSK-3β) by propolin G resulted in increasing GSK-3β interaction with Snail. Consequently, the nuclear localization and stability of Snail was disrupted resulting in promoting the degradation. Propolin G-inhibited Snail expression and the activities of migration and invasion were reversed by GSK-3β inhibitor pretreatment. Meanwhile, the outcomes also revealed that histone deacetylase 6 (HDAC6) activity was dose-dependently suppressed by propolin G. Correspondently, the amounts of acetyl-α-tubulin, a down-stream substrate of HDAC6, were increased. Dissociation of HDAC6/Hsp90 with vimentin leading to increased vimentin acetylation and degradation was perceived in the cells with the addition of propolin G. Moreover, up-regulated expression of acetyl-α-tubulin by propolin G was attenuated by HDAC6 overexpression. On the contrary, down-regulated expression of vimentin, cell migration and invasion by propolin G were overturned by HDAC6 overexpression. Conclusively, restraint cell migration and invasion of TNBC by propolin G were activated by the expression of GSK-3β-suppressed Snail and the interruption of HDAC6-mediated vimentin protein stability. Aiming at EMT, propolin G might be a potential candidate for TNBC therapy.     

Evaluation of Depigmenting Activity by 8-Hydroxydaidzein in Mouse B16 Melanoma Cells and Human Volunteers

In our previous study, 8-hydroxydaidzein (8-OHDe) was demonstrated to be a potent and unique suicide substrate of mushroom tyrosinase. In this study, the compound was evaluated for in vitro cellular tyrosinase and melanogenesis inhibitory activities in mouse B16 melanoma cells and for in vivo skin-whitening activity in human volunteers. Tyrosinase activity and melanogenesis in the cell culture incubated with 10 μM of 8-OHDe were decreased to 20.1% and 51.8% of control, respectively, while no obvious cytotoxicity was observed in this concentration. In contrast, a standard tyrosinase inhibitor, kojic acid, showed 69.9% and 71.3% of control in cellular tyrosinase and melanogenesis activity, respectively, at a concentration as high as 100 μM. Hence, 8-OHDe exhibited more than an inhibitory effects on melanin production in B16 cells 10-fold stronger than kojic acid. In addition, when a cream containing 4% 8-OHDe was applied to human skin in an in vivo study, significant increases in the dL*-values were observed after three weeks. Moreover, the increase in the dL*-values after 8-week treatment with 4% 8-OHDe (from −0.57 to 1.94) is stronger than those of 2% 8-OHDe treatment (from 0.26 to 0.94) and 2% ascorbic acid-2-glucoside treatment (from 0.07 to 1.54). From the results of the study, it was concluded that 8-OHDe, the potent suicide substrate of mushroom tyrosinase, has depigmenting activities in both mouse melanoma cells and in human volunteers. Thus, the compound has significant potential for use in cosmetics as a skin-whitening ingredient.     

Human Vascular Endothelial Cells Promote the Secretion of Vascularization Factors and Migration of Human Skin Fibroblasts under Co-Culture and Its Preliminary Application

The good treatment of skin defects has always been a challenge in the medical field, and the emergence of tissue engineering skin provides a new idea for the treatment of injured skin. However, due to the single seed cells, the tissue engineering skin has the problem of slow vascularization at the premonitory site after implantation into the human body. Cell co-culture technology can better simulate the survival and communication environment of cells in the human body. The study of multicellular co-culture hopes to bring a solution to the problem of tissue engineering. In this paper, human skin fibroblasts (HSFs) and human vascular endothelial cells (HVECs) were co-cultured in Transwell. The Cell Counting Kit 8 (CCK8), Transwell migration chamber, immunofluorescence, Western blot (WB), and real time quantitative PCR (RT-qPCR) were used to study the effects of HVECs on cell activity, migration factor (high mobility group protein 1, HMGB1) and vascularization factor (vascular endothelial growth factor A, VEGFA and fibroblast growth factor 2, FGF2) secretion of HSFs after co-cultured with HVECs in the Transwell. The biological behavior of HSFs co-cultured with HVECs was studied. The experimental results are as follows: (1) The results of cck8 showed that HVECS could promote the activity of HSFs. (2) HVECs could significantly promote the migration of HSFs and promote the secretion of HMGB1. (3) HVECs could promote the secretion of VEGFA and FGF2 of HSFs. (4) The HVECs and HSFs were inoculated on tissue engineering scaffolds at the ratio of 1:4 and were co-cultured and detected for 7 days. The results showed that from the third day, the number of HSFs was significantly higher than that of the control group without HVECs.     

Decursinol Angelate Arrest Melanoma Cell Proliferation by Initiating Cell Death and Tumor Shrinkage via Induction of Apoptosis

Melanoma is known to aggressively metastasize and is one of the prominent causes of skin cancer mortality. This study was designed to assess the molecular mechanism of decursinol angelate (DA) against murine melanoma cell line (B16F10 cells). Treatment of DA resulted in growth inhibition and cell cycle arrest at G0/G1 (p < 0.001) phase, evaluated through immunoblotting. Moreover, autophagy-related proteins such as ATG-5 (p < 0.0001), ATG-7 (p < 0.0001), beclin-1 (p < 0.0001) and transition of LC3-I to LC3-II (p < 0.0001) were markedly decreased, indicating autophagosome inhibition. Additionally, DA treatment triggered apoptotic events which were corroborated by the occurrence of distorted nuclei, elevated reactive oxygen species (ROS) levels and reduction in the mitochondrial membrane potential. Subsequently, there was an increase in the expression of pro-apoptotic protein Bax in a dose-dependent manner, with the corresponding downregulation of Bcl-2 expression and cytochrome C expression following 24 h DA treatment in A375.SM and B16F10 cells. We substantiated our results for apoptotic occurrence through flow cytometry in B16F10 cells. Furthermore, we treated B16F10 cells with N-acetyl-L-cysteine (NAC). NAC treatment upregulated ATG-5 (p < 0.0001), beclin-1 (p < 0.0001) and LC3-I to LC3-II (p < 0.0001) conversion, which was inhibited in the DA treatment group. We also noticed a systematic upregulation of important markers for progression of G1 cell phase such as CDK-2 (p < 0.029), CDK-4 (p < 0.036), cyclin D1 (p < 0.0003) and cyclin E (p < 0.020) upon NAC treatment. In addition, we also observed a significant fold reduction (p < 0.05) in ROS fluorescent intensity and the expression of Bax (p < 0.0001), cytochrome C (p < 0.0001), cleaved caspase-9 (p > 0.010) and cleaved caspase-3 (p < 0.0001). NAC treatment was able to ameliorate DA-induced apoptosis and cell cycle arrest to support our finding. Our in vivo xenograft model also revealed similar findings, such as downregulation of CDK-2 (p < 0.0001) and CDK-4 (p < 0.0142) and upregulation of Bax (p < 0.0001), cytochrome C (p < 0.0001), cleaved caspase 3 (p < 0.0001) and cleaved caspase 9 (p < 0.0001). In summary, our study revealed that DA is an effective treatment against B16F10 melanoma cells and xenograft mice model.     

Deciphering Repertoire of B16 Melanoma Reactive TCRs by Immunization,In Vitro Restimulation and Sequencing of IFNγ-Secreting T Cells

Recent advances in cancer immunotherapy have great promise for the treatment of solid tumors. One of the key limiting factors that hamper the decoding of physiological responses to these therapies is the inability to distinguish between specific and nonspecific responses. The identification of tumor-specific lymphocytes is also the most challenging step in cancer cell therapies such as adoptive cell transfer and T cell receptor (TCR) cloning. Here, we have elaborated a protocol for the identification of tumor-specific T lymphocytes and the deciphering of their repertoires. B16 melanoma engraftment following anti-PD1 checkpoint therapy provides better antitumor immunity compared to repetitive immunization with heat-shocked tumor cells. We have also revealed that the most error-prone part of dendritic cell (DC) generation, i.e., their maturation step, can be omitted if DCs are cultured at a sufficiently high density. Using this optimized protocol, we have achieved a robust IFNγ response to B16F0 antigens, but only within CD4+ T helper cells. A comparison of the repertoires of IFNγ-positive and -negative cells shows a prominent enrichment of certain clones with putative tumor specificity among the IFNγ+ fraction. In summary, our optimized protocol and the data provided here will aid in the acquisition of broad statistical data and the creation of a meaningful database of B16-specific TCRs.