Focal adhesion alterations in G0-positive melanoma cells.

BACKGROUND: Melanoma is a highly heterogeneous malignant tumor that exhibits various forms of drug resistance. Recently, reversal transition of cancer cells to the G0 phase of the cell cycle under the influence of therapeutic drugs has been identified as an event associated with tumor dissemination. In the present study, we investigated the ability of chemotherapeutic agent dacarbazine to induce a transition of melanoma cells to the G0 phase as a mechanism of chemoresistance. METHODS: We used the flow cytometry to analyze cell distribution within cell cycle phases after dacarbazine treatment as well as to identifyG0 -positive cells population. Transcriptome profiling was provided to determine genes associated with dacarbazine resistance. We evaluated the activity of ß-galactosidase in cells treated with dacarbazine by substrate hydrolysis. Cell adhesion strength was measured by centrifugal assay application with subsequent staining of adhesive cells with Ki-67 monoclonal antibodies. Ability of melanoma cells to metabolize dacarbazine was determined by expressional analysis of CYP1A1, CYP1A2, CYP2E1 followed by CYP1A1 protein level evaluation by the ELISA method. RESULTS: The present study determined that dacarbazine treatment of melanoma cells could induce an increase in the percentage of cells in G0 phase without alterations of ß-galactosidase positive cells which corresponded to the fraction of the senescent cells. Transcriptomic profiling of cells under dacarbazine induction of G0 -positive cells percentage revealed that 'VEGFA-VEGFR2 signaling pathway' and 'Cell cycle' signaling were mostly enriched by dysregulated genes. 'Focal adhesion' signaling was also found to be triggered by dacarbazine. In melanoma cells treated with dacarbazine, an increase in G0 -positive cells among adherent cells was found. CONCLUSIONS: Dacarbazine induces the alteration in a percentage of melanoma cells residing in G0 phase of a cell cycle. The altered adhesive phenotype of cancer cells under transition in the G0 phase may refer to a specific intercellular communication pattern of quiescent/senescent cancer cells.

MicroRNAs' control of cancer cell dormancy.

'Dormancy', in the context of carcinogenesis, is a biological phenomenon of decreased cancer cell proliferation and metabolism. In view of their ability to remain quiescent, cancer cells are able to avoid cell death induced by chemotherapeutic agents, and thereby give rise to tumor relapse at a later stage. Being a dynamic event, the dormant state is controlled by several epigenetic mechanisms, including the action of microRNAs. The present review highlights microRNAs that have been shown to be dysregulated in dormant cancer cells among different tumor types. MicroRNAs accomplish their control of cancer cell quiescence by targeting cell cycle regulators and signaling pathways involved in cell growth maintenance, including the AKT/phosphoinositide 3-kinase (PI3K) pathway. MicroRNAs, as components of intercellular vesicles, enable interactions to occur between cancer cells and cells of the microenvironment, resulting in the cancer cells either acquiring the quiescent state or, oppositely, stimulating them to proliferate. Taken together, the evidence obtained to date has collectively confirmed the involvement of microRNAsin cancer cell dormancy. Modulation of the various processes may enable optimization of the treatment of metastatic tumors.

Semaphorin-5A downregulation is associated with enhanced migration and invasion of BRAF-positive melanoma cells under vemurafenib treatment in melanomas with heterogeneous BRAF status.

Tumor heterogeneity affects the efficacy of anticancer treatment as tumor subclones with distinct molecular patterns may be present within one tumor, leading to differing sensitivities to chemotherapeutic agents. In the present study, six melanoma tissue fragments were obtained from different parts of tumor of four patients and then the effect of vemurafenib treatment on biological characteristics and molecular processes of cell cultures was estimated by using MTT-test, apoptosis, migration and invasion assays, PCR real time. There was different BRAF status determined between cells derived from the central and peripheral regions of primary melanoma tumors. BRAF-positive melanoma cells showed an increased apoptotic rate under vemurafenib treatment, as well as increased migration and invasion rates, whereas BRAF-negative melanoma cells did not exhibit such tendency. Furthermore, semaphorin-5A levels were diminished in BRAF-positive cells, but not in BRAF-negative ones, which could be related to increased migration and invasion. Melanoma cells derived from different regions of the same tumor may differ by mutations status, molecular processes and biological response to target therapy. The downregulation of semaphorin-5A may be involved in divergent effects of anticancer agents on tumor cell biology.

miR-155 overexpression is followed by downregulation of its target gene, NFE2L2, and altered pattern of VEGFA expression in the liver of melanoma B16-bearing mice at the premetastatic stage.

MicroRNAs are involved in the control of tumour progression and in metastatic cascade dynamics. However, the role of microRNAs in distant organ reorganization at the premetastatic stage is less clear, although the process of premetastatic niche formation is a crucial event according to modern concepts of tumour dissemination. The role of the present study was to investigate the expression levels of miR-155, miR-21, miR-205 and miR-let7b, as well as that of their target genes, in target organs of melanoma metastasis at the premetastatic stage. The expression levels of both the pro-oncogenic miR-155 and the tumour suppressive miR-205 were found to be altered in the premetastatic liver of melanoma B16-bearing mice. Bioinformatics analysis identified the target genes of miR-155 to be nuclear factor, erythroid 2 like 2 (NFE2L2), secretogranin II, miR-205, semaphorin 5A and vascular endothelial growth factor A (VEGFA). Among those, the redox status regulatory factor NFE2L2 was downregulated, which corresponded to increased levels of miR-155. Due to the ability of pro-oxidative events to initiate angiogenesis, VEGFA levels were evaluated in the premetastatic liver by immunohistochemistry, which revealed increased VEGFA expression in the central parts of the organ and diminished expression in the periphery. Taken together, these findings may support the concept of functional organ reorganization due to melanoma progression.

Genetic analysis of melanocortin 1 receptor red hair color variants in a Russian population of Eastern Siberia.

The melanocortin 1 receptor is a Gs protein-coupled receptor implicated in melanogenesis regulation. The receptor gene is highly polymorphic, which accounts for the association of several of its single-nucleotide polymorphisms (SNPs) with an increased risk of melanoma. The present study aimed to evaluate the distribution of melanocortin 1 receptor gene variants R151C, R160W, and D294H within the Russian population of Eastern Siberia and its association with melanoma development. Melanoma patients (n=95) admitted to Krasnoyarsk Territorial Oncological Center and healthy controls (n=334) were enrolled in the study. A clinical examination of patients was performed to evaluate the phenotypic features of melanoma patients. SNPs were analyzed by real-time PCR. Clinical examination indicated a more frequent occurrence of fair skin type, blue eyes, blonde and red hair, and more frequent localization of freckles on the neck, trunk, and extremities in the melanoma group of patients. The R151C melanocortin 1 receptor gene variant was found in 18% of melanoma patients and associated with an increased likelihood of melanoma development (odds ratio=6.4; 95% confidence interval: 2.8-14.3; P=0.0001). The two remaining variant alleles of the melanocortin 1 receptor gene occurred with low frequency both in controls and in the melanoma group. The R160W SNP was identified neither in controls nor in melanoma patients. The D294H heterozygous variant was observed in 0.3% of individuals in the control group and in 1.1% of the patients in the melanoma group. Such an asymmetric distribution of the melanocortin 1 receptor within red hair color genotypes in the population under study compared with other populations may be because of Russian genetic homogeneity. Carriers of the mutant R151C allele should exercise caution in terms of exposure to the sun to avoid the risk of melanoma development.

MicroRNA in skin diseases.

MicroRNAs are essential regulators of various cellular processes such as cell growth, differentiation, apoptosis, and the immune response, acting as factors for translational repression and/or degradation of target messenger RNA. Currently, microRNAs are considered as promising biomarkers and therapeutic targets for different pathological conditions. Skin may serve as a convenient model for microRNA modulation studies due to the comparatively easy access to targets cells. Cutaneous diseases are characterized by multiple intercellular communication pathways, triggered by diverse stimuli and mediated by heterogenous regulators, including microRNAs. The goal of this article is to summarize the state of research in dermatology concerning the action of microRNAs as epigenetic modulators.