Melanoma cells use different migratory strategies to exit the primary tumor mass and invade surrounding and subsequently distant tissues. We reported previously that ADAR1 expression is downregulated ...in metastatic melanoma, thereby facilitating proliferation. Here we show that ADAR1 silencing enhances melanoma cell invasiveness and ITGB3 expression. The enhanced invasion is reversed when ITGB3 is blocked with antibodies. Re-expression of wild-type or catalytically inactive ADAR1 establishes this mechanism as independent of RNA editing. We demonstrate that ADAR1 controls ITGB3 expression both at the post-transcriptional and transcriptional levels, via miR-22 and PAX6 transcription factor, respectively. These are proven here as direct regulators of ITGB3 expression. miR-22 expression is controlled by ADAR1 via FOXD1 transcription factor. Clinical relevance is demonstrated in patient-paired progression tissue microarray using immunohistochemistry. The novel ADAR1-dependent and RNA-editing-independent regulation of invasion, mediated by ITGB3, strongly points to a central involvement of ADAR1 in cancer progression and metastasis.
Previously we have reported that metastatic melanoma cell lines and tumor specimens have reduced expression of ADAR1 and consequently are impaired in their ability to perform A-to-I microRNA (miRNA) ...editing. The effects of A-to-I miRNAs editing on melanoma growth and metastasis are yet to be determined. Here we report that miR-378a-3p is undergoing A-to-I editing only in the non-metastatic but not in metastatic melanoma cells. The function of the edited form is different from its wild-type counterpart. The edited form of miR-378a-3p preferentially binds to the 3'-UTR of the PARVA oncogene and inhibits its expression, thus preventing the progression of melanoma towards the malignant phenotype. Indeed, edited miR-378a-3p but not its WT form inhibits melanoma metastasis in vivo. These results further emphasize the role of RNA editing in melanoma progression.
Immune checkpoint blockade (ICB) has demonstrated an impressive outcome in patients with metastatic melanoma, yet, durable complete response; even with Ipilimumab/Nivolumab combo are under 30%. ...Primary and acquired resistance in response to ICB is commonly due to a tumor immune escape mechanism dictated by the tumor microenvironment (TME). Macrophage Migratory Inhibition Factor (MIF) has emerged as an immunosuppressive factor secreted in the TME. We have previously demonstrated that blockade of the MIF-CD74 signaling on macrophages and dendritic cells restored the anti-tumor immune response against melanoma. Here, we report that inhibition of the MIF-CD74 axis combined with ipilimumab could render resistant melanoma to better respond to anti-CTLA-4 treatment. We provide evidence that blocking the MIF-CD74 signaling potentiates CD8+ T-cells infiltration and drives pro-inflammatory M1 conversion of macrophages in the TME. Furthermore, MIF inhibition resulted in reprogramming the metabolic pathway by reducing lactate production, HIF-1α and PD-L1 expression in the resistant melanoma cells. Melanoma patient data extracted from the TCGA database supports the hypothesis that high MIF expression strongly correlates with poor response to ICB therapy. Our findings provide a rationale for combining anti-CTLA-4 with MIF inhibitors as a potential strategy to overcome resistance to ICB therapy in melanoma, turning a "cold" tumor into a "hot" one mediated by the activation of innate immunity and reprogramming of tumor metabolism and reduced PD-L1 expression in melanoma cells.
Why is melanoma so metastatic? Braeuer, Russell R.; Watson, Ian R.; Wu, Chang-Jiun ...
Pigment cell and melanoma research,
January 2014, Letnik:
27, Številka:
1
Journal Article
Recenzirano
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Summary
Malignant melanoma is one of the most aggressive cancers and can disseminate from a relatively small primary tumor and metastasize to multiple sites, including the lung, liver, brain, bone, ...and lymph nodes. Elucidating the molecular and genetic changes that take place during the metastatic process has led to a better understanding of why melanoma is so metastatic. Herein, we describe the unique features that distinguish melanoma from other solid tumors and contribute to the malignant phenotype of melanoma cells. For example, although melanoma cells are highly antigenic, they are extremely efficient at evading host immune response. Melanoma cells share numerous cell surface molecules with vascular cells, are highly angiogenic, are mesenchymal in nature, and possess a higher degree of ‘stemness’ than do other solid tumors. Finally, analysis of melanoma mutations has revealed that the gene expression profile of malignant melanoma is different from that of other cancers. Elucidating these molecular and genetic processes in highly metastatic melanoma can lead to the development of improved treatment and individualized therapy options.
In this research, we studied the factors that control formation of GMO/tricaprylin/water hexosomes and affect their inner structure. As a stabilizer of the soft particles dispersed in the aqueous ...phase, we used the hydrophilic nonionic triblock polymer Pluronic 127. We demonstrate how properties of the hexosomes, such as size, structure, and stability, can be tuned by their internal composition, polymer concentration, and processing conditions. The morphology and inner structure of the hexosomes were characterized by small-angle X-ray scattering, cryo-transmission electron microscope, and dynamic light scattering. The physical stability (to creaming, aggregation, and coalescence) of the hexosomes was further examined by the LUMiFuge technique. Two competing processes are presumed to take place during the formation of hexosomes: penetration of water from the continuous phase during dispersion, resulting in enhanced hydration of the head groups, and incorporation of the polymer chains into the hexosome structure while providing a stabilizing surface coating for the dispersed particles. Hydration is an essential stage in lyotropic liquid crystal (LLC) formation. The polymer, on the other hand, dehydrates the lipid heads, thereby introducing disorder into the LLC and reducing the domain size. Yet, a critical minimum polymer concentration is necessary in order to form stable nanosized hexosomes. These competing effects require the attention of those preparing hexosomes. The competition between these two processes can be controlled. At relatively high polymer concentrations (1−1.6 wt % of the total formulation of the soft particles), the hydration process seems to occur more rapidly than polymer adsorption. As a result, smaller and more stable soft particles with high symmetry were formed. On the other hand, when the polymer concentration is fixed at lower levels (<1.0 wt %), the homogenization process encourages only partial polymer adsorption during the dispersion process. This adsorption is insufficient; hence, maximum hydration of the surfactant head group is reached prior to obtaining full adsorption, resulting in the formation of less ordered hexosomes of larger size and lower stability.
Melanoma is the deadliest form of skin cancer in which patients with metastatic disease have a 5-year survival rate of less than 10%. Recently, the overexpression of a β-galactoside binding protein, ...galectin-3 (LGALS3), has been correlated with metastatic melanoma in patients. We have previously shown that silencing galectin-3 in metastatic melanoma cells reduces tumor growth and metastasis. Gene expression profiling identified the protumorigenic gene autotaxin (ENPP2) to be downregulated after silencing galectin-3. Here we report that galectin-3 regulates autotaxin expression at the transcriptional level by modulating the expression of the transcription factor NFAT1 (NFATC2). Silencing galectin-3 reduced NFAT1 protein expression, which resulted in decreased autotaxin expression and activity. Reexpression of autotaxin in galectin-3 silenced melanoma cells rescues angiogenesis, tumor growth, and metastasis in vivo. Silencing NFAT1 expression in metastatic melanoma cells inhibited tumor growth and metastatic capabilities in vivo. Our data elucidate a previously unidentified mechanism by which galectin-3 regulates autotaxin and assign a novel role for NFAT1 during melanoma progression.
The progression of melanoma toward the metastatic phenotype occurs in a defined stepwise manner. While many molecular changes take place early in melanoma development, progression toward the ...malignant phenotype, most notably during the transition from the radial growth phase (RGP) to the vertical growth phase (VGP) involves deregulated expression of several transcription factors. For example, the switch from RGP to VGP is associated with the loss of the transcription factor AP2α and gain of transcriptional activity of cAMP-responsive element binding protein. Together with the upregulation of microphthalmia-associated transcription factor, activating transcription factor 2, nuclear factor kappa B, and other transcription factors, these changes lead to dysregulated expression or function of important cellular adhesion molecules, matrix degrading enzymes, survival factors, as well as other factors leading to metastatic melanoma. Additionally, recent evidence suggests that microRNAs and RNA editing machinery influence the expression of transcription factors or are regulated themselves by transcription factors. Many of the downstream signaling molecules regulated by transcription factors, such as protease activated receptor-1, interleukin-8, and MCAM/MUC18 represent new treatment prospects.
Summary
Melanoma is the leading cause of skin cancer‐related deaths, which is due in large part to its aggressive behavior, resistance to therapy, and ability to metastasize to multiple organs such ...as the lymph nodes, lung, and brain. Melanoma progresses in a stepwise manner from the benign nevus, to radial spreading through the dermis, to a vertical invasive phase, and finally to metastasis. The carbohydrate‐binding family of galectins has a strong influence on each phase of melanoma progression through their effects on immune surveillance, angiogenesis, cell migration, tumor cell adhesion, and the cellular response to chemotherapy. Galectins share significant homology in their carbohydrate recognition domain (CRD), which mediates binding to an array of N‐glycosylated proteins located on the surface of tumor cells, endothelial cells, T‐cells, and to similarly glycosylated extracellular matrix proteins. Galectins are also present within tumor cells where they perform anti‐apoptotic functions and enhance intracellular signaling that results in deregulated expression of genes involved in tumor progression. The most extensively studied galectins, galectin‐1 and galectin‐3, have been shown to have profound effects on melanoma growth and metastasis by influencing many of these biological processes.
A water-in-oil microemulsion was further dispersed in an aqueous phase containing Pluronic F127 as a steric stabilizer, to form a specific type of double emulsion termed emulsified microemulsion ...(EME). The inner microemulsion phase was made from glycerol-monooleate (GMO), R(+)-limonene, ethanol and glycerol. SAXS (small x-ray scattering), PGSE-NMR (pulse gradient spin echo-NMR), electrical conductivity, and cryo-TEM (cryogenic-transmission electron microscopy) imaging techniques were used to confirm the existence of inner W/O nano-droplets after second emulsification step and upon EME aging. Spherical globules of EME without long-range internal order were observed by the SAXS measurements and the cryo-TEM images. The average globule size of about 200-300 nm remained intact for at least 6 months.
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