MicroRNA-21 antisense oligonucleotide improves the sensitivity of A375 human melanoma cell to Cisplatin: An in vitro study

Targeting the epigenome in malignant melanoma: Facts, challenges and therapeutic promises

Malignant melanoma is the most lethal type of skin cancer with high rates of mortality. Although current treatment options provide a short-clinical benefit, acquired-drug resistance highlights the low 5-year survival rate among patients with advanced stage of the disease. In parallel, the involvement of an aberrant epigenetic landscape, (e.g., alterations in DNA methylation patterns, histone modifications marks and expression of non-coding RNAs), in addition to the genetic background, has been also associated with the onset and progression of melanoma. In this review article, we report on current therapeutic options in melanoma treatment with a focus on distinct epigenetic alterations and how their reversal, by specific drug compounds, can restore a normal phenotype. In particular, we concentrate on how single and/or combinatorial therapeutic approaches have utilized epigenetic drug compounds in being effective against malignant melanoma. Finally, the role of deregulated epigenetic mechanisms in promoting drug resistance to targeted therapies and immune checkpoint inhibitors is presented leading to the development of newly synthesized and/or improved drug compounds capable of targeting the epigenome of malignant melanoma.

Effect of a Low-Level Laser on Liposomal Doxorubicin Efficacy in a Melanoma Cell Line

Introduction: The cytotoxicity of chemotherapy drugs is a significant challenge in the way of surmounting cancer. Liposomal drug delivery has proven to be efficacious in increasing the function of the drugs. Its potential to accumulate drugs in the target site and enhance the efficiency of anti-cancer agents with lower doses hinders their cytotoxicity on normal healthy cells. Since the release of drugs from liposomes is not generally on a controlled basis, several studies have suggested that external stimuli including lasers could be used to induce controlled release and boost the efficiency of liposomal drug delivery systems (LDDSs). Methods: The A375 cancer cell line was used and exposed to the liposomes containing doxorubicin in the presence of a low-level laser beam to investigate its effect on the liposomal stimuli-responsiveness release and its toxicity on cancer cells. So as to achieve that goal, Annexin V/PI was employed to analyze the number of cells that underwent apoptosis and necrosis. Results: Here, we report the effect of laser irradiation on LDDSs. According to the results obtained from the annexin V/PI assay, the pattern of viability status has shifted, so that the number of pre-apoptotic cells treated with liposomal doxorubicin and a laser beam was more than that of cells treated with only liposomal doxorubicin. Conclusion: The use of stimuli-responsive LDDSs, in this case, laser-responsive, has led to favorable circumstances in the treatment of cancer, offering enhanced cancer cell cytotoxicity.

miR-21 Induces Chemoresistance in Ovarian Cancer Cells via Mediating the Expression and Interaction of CD44v6 and P-gp

Background

Ovarian cancer (OC), a representative female reproductive system tumor, is one of the most malignant tumors in female. The most important reason for its poor prognosis is because of its high rate of chemotherapy resistance.

Results

This study aims to explore the effects of miR-21 on the chemotherapy resistance of OC cells. The functions of miR-21 on proliferation, migration and invasion of OC cells were assessed by transwell, clonal formation and CCK8 assay. Expression levels of miR-21, P-gp and CD44v6 in SKOV3 (cisplatin sensitive) cells and SKOV3/DDP (cisplatin resistant) cells were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting. Si-CD44v6 was transfected into OC cells to detect the influence on P-glycoprotein (P-gp) expression. Immunofluorescence was used to detect the localization of CD44v6 and P-gp in cell. Co-immunoprecipitation was used to detect the relationship between CD44v6 and P-gp. Results showed that miR-21 expression in cisplatin-resistant SKOV3/DDP cells was significantly higher than that in SKOV3 cells, at the same time, cells proliferation, as well as invasion and migration ability were enhanced after the miR-21 mimics transfected into SKOV3 cisplatin-sensitive cells. Furthermore, miR-21 expression level affected the CD44v6 and P-gp expression. Immunofluorescence and co-immunoprecipitation showed that CD44v6 and P-gp protein could interact.

Conclusion

In conclusion, the high miR-21 expression level could increase the proliferation, invasion, and migration ability of OC cells. And the interaction of CD44v6 and P-gp may mediate miR-21 involvement in chemotherapy resistance of OC cells.

3-O-Methylquercetin from Achyrocline satureioides-cytotoxic activity against A375-derived human melanoma cell lines and its incorporation into cyclodextrins-hydrogels for topical administration

3-O-Methylquercetin (3OMQ), a natural 3-O-methylflavonoid, was isolated from Achyrocline satureioides and purified using the high-performance counter current chromatography (HPCCC) on a semi-preparative scale. High-purity 3OMQ (98%) was obtained with excellent recovery (81.8% (w/w)) and good yield (190 mg/100 g of plant). Isolated 3OMQ was evaluated against the A375 human amelanotic melanoma cancer cell line and A375-derived with different degrees of aggressiveness (A375-A7, A375-G10, and A375-PCDNA3). The results showed that 3OMQ reduced the cell viability of all strains, demonstrating time- and dose-dependent responses. 3OMQ was used to obtain hydrogels for the topical treatment of melanoma. Thus, 3OMQ was incorporated into hypromellose hydrogels with/without different cyclodextrins (CDs). The 3OMQ formulations showed permeation/retention in all skin layers, namely stratum corneum, epidermis, and dermis. A significant amount of 3OMQ was found in the replication site of the melanoma cells (epidermis and dermis). Altogether, these results demonstrate that 3OMQ can be isolated from Achyrocline satureioides by HPCCC on a semi-preparative scale and exhibit cytotoxic activity against melanoma cells. Its incorporation into an HPMC hydrogel containing HP-β-CD yielded a formulation with excellent technological and biopharmaceutical characteristics for evaluating the topical management of melanoma.

Importance of microRNAs in Skin Oncogenesis and Their Suitability as Agents and Targets for Topical Therapy

Skin cancer is the most common cancer worldwide, with rapidly increasing incidence and consistent mortality. Skin cancer encompasses melanoma and non-melanoma skin cancer, which in turn is mainly divided into cutaneous squamous cell carcinoma and basal cell carcinoma. Small noncoding micro-RNAs (miRNAs) regulate protein expression after transcription and play a role in the development and progression of skin cancer. Deregulated expression of miRNAs in skin cancer is associated with cell proliferation, angiogenesis, metastasis, apoptosis, immune response, and drug resistance. Specific patterns of miRNAs in specific skin cancer types can be used as diagnostic markers. For therapeutic purposes, both miRNA and chemically modified variants thereof as well as miRNA antagonists (antagomiRs) or RNA inhibitors may be applied topically. Due to their specific physicochemical properties, physical or chemical diffusion promoters are used with varying degrees of success. There is no question by now that such preparations have a high potential for the treatment of epithelial skin tumors in particular.

MicroRNA-21-Enriched Exosomes as Epigenetic Regulators in Melanomagenesis and Melanoma Progression: The Impact of Western Lifestyle Factors

DNA mutation-induced activation of RAS-BRAF-MEK-ERK signaling associated with intermittent or chronic ultraviolet (UV) irradiation cannot exclusively explain the excessive increase of malignant melanoma (MM) incidence since the 1950s. Malignant conversion of a melanocyte to an MM cell and metastatic MM is associated with a steady increase in microRNA-21 (miR-21). At the epigenetic level, miR-21 inhibits key tumor suppressors of the RAS-BRAF signaling pathway enhancing proliferation and MM progression. Increased MM cell levels of miR-21 either result from endogenous upregulation of melanocytic miR-21 expression or by uptake of miR-21-enriched exogenous exosomes. Based on epidemiological data and translational evidence, this review provides deeper insights into environmentally and metabolically induced exosomal miR-21 trafficking beyond UV-irradiation in melanomagenesis and MM progression. Sources of miR-21-enriched exosomes include UV-irradiated keratinocytes, adipocyte-derived exosomes in obesity, airway epithelium-derived exosomes generated by smoking and pollution, diet-related exosomes and inflammation-induced exosomes, which may synergistically increase the exosomal miR-21 burden of the melanocyte, the transformed MM cell and its tumor environment. Several therapeutic agents that suppress MM cell growth and proliferation attenuate miR-21 expression. These include miR-21 antagonists, metformin, kinase inhibitors, beta-blockers, vitamin D, and plant-derived bioactive compounds, which may represent new options for the prevention and treatment of MM.

RKIP Regulates Differentiation-Related Features in Melanocytic Cells

Raf Kinase Inhibitor Protein (RKIP) has been extensively reported as an inhibitor of key signaling pathways involved in the aggressive tumor phenotype and shows decreased expression in several types of cancers. However, little is known about RKIP in melanoma or regarding its function in normal cells. We examined the role of RKIP in both primary melanocytes and malignant melanoma cells and evaluated its diagnostic and prognostic value. IHC analysis revealed a significantly higher expression of RKIP in nevi compared with early-stage (stage I–II, AJCC 8th) melanoma biopsies. Proliferation, wound healing, and collagen-coated transwell assays uncovered the implication of RKIP on the motility but not on the proliferative capacity of melanoma cells as RKIP protein levels were inversely correlated with the migration capacity of both primary and metastatic melanoma cells but did not alter other parameters. As shown by RNA sequencing, endogenous RKIP knockdown in primary melanocytes triggered the deregulation of cellular differentiation-related processes, including genes (i.e., ZEB1, THY-1) closely related to the EMT. Interestingly, NANOG was identified as a putative transcriptional regulator of many of the deregulated genes, and RKIP was able to decrease the activation of the NANOG promoter. As a whole, our data support the utility of RKIP as a diagnostic marker for early-stage melanomas. In addition, these findings indicate its participation in the maintenance of a differentiated state of melanocytic cells by modulating genes intimately linked to the cellular motility and explain the progressive decrease of RKIP often described in tumors.

Overexpression of CASC2 Improves Cisplatin Sensitivity in Hepatocellular Carcinoma Through Sponging miR-222

The long noncoding RNA cancer susceptibility candidate 2 (CASC2) has been shown to play a crucial role in cancer cell chemoresistance. However, its function and underlying molecular mechanism in hepatocellular carcinoma (HCC) chemoresistance remain unknown. In this study, we used cisplatin (DDP)-resistant HCC cells to investigate CASC2 function and its underlying mechanism. The results demonstrated that CASC2 expression was significantly reduced in HCC tissues and cells, especially in DDP-resistant HCC tissues and cells. Lower CASC2 expression was strongly correlated with shorter survival times in patients with HCC. Functionally, CASC2 overexpression sensitized DDP-resistant Huh7/DDP and SMMC-7721/DDP cells to DDP. Mechanically, CASC2 improved the sensitivity of HCC cells to DDP through sponging miR-222. Taken together, these findings suggested that overexpression of CASC2 overcame DDP resistance in HCC by regulating miR-222 expression, thereby providing a potential therapeutic strategy for overcoming HCC cell chemoresistance.

Overexpression of microRNA‑21 inhibits the growth and metastasis of melanoma cells by targeting MKK3

Melanoma is an aggressive skin carcinoma with poor prognosis, and is prevalent worldwide. It was demonstrated that microRNA (miR)‑21 and mitogen‑activated protein kinase kinase 3 (MKK3) both participated in the occurrence and development of various tumors; however, their detailed roles in the progression of melanoma remain unclear. Reverse transcription‑quantitative PCR (RT‑qPCR) and western blot analyses were conducted to examine the expression levels of miR‑21 and MKK3 in clinical specimens of patients with melanoma and melanoma cell lines. A dual‑luciferase reporter assay was performed to verify the target interaction between miR‑21 and MKK3. The mRNA and protein expressions of MKK3 were measured using RT‑qPCR and western blot analysis, respectively, following transfection with miR‑21 mimics and inhibitor. Subsequently, Cell Counting Kit‑8 and colony formation assays, and flow cytometry were conducted to assess the effects of miR‑21 and MKK3 on the cell growth of melanoma. Cell migration and invasion experiments were performed to evaluate the effects of miR‑21 and MKK3 on the cell metastasis of melanoma. It was revealed that MKK3 was upregulated, and miR‑21 was downregulated in patients with melanoma and melanoma cell lines. MKK3 was demonstrated to be a direct target of miR‑21. Furthermore, it was demonstrated that upregulated miR‑21 expression and downregulated MKK3 expression suppressed cell proliferation and colony formation, promoted apoptosis, delayed the cell cycle, and inhibited cell migration and invasion. The present findings suggested that miR‑21 could inhibit the cell growth and metastasis of melanoma by negatively regulating MKK3.

Glutathione peroxidase 3 (GPX3) suppresses the growth of melanoma cells through reactive oxygen species (ROS)-dependent stabilization of hypoxia-inducible factor 1-α and 2-α

In this study, we aimed to explore the mechanism of glutathione peroxidase 3 (GPX3) in the growth of malignant melanoma (MM) cells by hypoxia-inducible factor-1α (HIF1-α) and HIF2-α regulating the metabolism through reactive oxygen species (ROS). The messenger RNA and protein expression of GPX3, HIF1-α, HIF2-α in tissues, and cell lines were measured by reverse transcription-quantitative PCR and Western blot analysis. A375 cells were transfected with GPX3 overexpression plasmid, small interfering RNA (siRNA) targeting GPX3, or siRNA targeting HIF1-α/HIF2-α to upregulate or downregulate the expression of GPX3 or HIF1-α/HIF2-α. The effects of H₂ O₂ and N-acetylcysteine (NAC) on the levels of HIF1-α and HIF2-α after overexpression of GPX3 were studied. The cell viability was detected by Cell Counting Kit-8. The levels of ROS, glucose uptake and lactic acid production, oxidative phosphorylation, and glycolysis of cells were measured for assessment of cellular metabolism. The expression of GPX3 decreased, while ROS, HIF1-α, and HIF2-α increased in MM tissues and cells. Overexpression of GPX3 inhibited the viability of MM cells and the growth of melanoma xenografts. The overexpression of GPX3 reduced the glucose uptake, extracellular lactic acid content, and extracellular acidification rate and increased the oxygen consumption rate level. Overexpression of GPX3 could reduce the levels of HIF1-α and HIF2-α, which could regulate metabolic levels. GPX3 reduced ROS level in MM to inhibit HIF1-α and HIF2-α. The addition of H₂ O₂ increased while NAC reduced the protein levels of HIF1-α and HIF2-α in the cells overexpressing GPX3. Our study demonstrates that GPX3 inhibits the growth of MM cells through its inhibitory effect on cell metabolic disorder by inhibiting HIF1-α via regulating ROS.

Methylation-Mediated Silencing of MicroRNA-211 Decreases the Sensitivity of Melanoma Cells to Cisplatin

BACKGROUND Malignant melanoma is recalcitrant to most existing chemotherapies, and aberrant expression of miR-211 plays prominent roles in progression of melanoma. However, the trigger mechanism of aberrant miR-211 expression in melanoma is still elusive. MATERIAL AND METHODS We used qRT-PCR to test miR-211 expression. Cell viability assay and mouse xenograft assay were performed to examine the role of miR-211 on the sensitivity of melanoma cells to cisplatin. The epigenetic modification of miR-211 promoter was assess by DNA methylation analysis and DAC treatment. RESULTS In this study, decreased miR-211 expression was detected. Bisulfite sequencing PCR showed that DNA hypermethylation contributed to the downregulation of miR-211 in melanoma tissues. In melanoma cells, overexpressed 211 could enhance the anticancer effect of cisplatin and restoration of miR-211 rendered susceptibility to cisplatin in cisplatin-resistant cells. And the same result was showed in vivo by mouse xenograft assay. What is more, DAC treatment could increase miR-211 expression and EZH2 expression was increased in cisplatin-resistant cells. MiR-211 could be transcriptionally repressed by EZH2 mediated promoter methylation. CONCLUSIONS Taken together, our findings revealed that epigenetic modification of miR-211 governed melanoma cell chemosensitivity and were involved in the progression of tumorigenesis.

Miniaturization of the Clonogenic Assay Using Confluence Measurement

The clonogenic assay is a widely used method to study the ability of cells to ‘infinitely’ produce progeny and is, therefore, used as a tool in tumor biology to measure tumor-initiating capacity and stem cell status. However, the standard protocol of using 6-well plates has several disadvantages. By miniaturizing the assay to a 96-well microplate format, as well as by utilizing the confluence detection function of a multimode reader, we here describe a new and modified protocol that allows comprehensive experimental setups and a non-endpoint, label-free semi-automatic analysis. Comparison of bright field images with confluence images demonstrated robust and reproducible detection of clones by the confluence detection function. Moreover, time-resolved non-endpoint confluence measurement of the same well showed that semi-automatic analysis was suitable for determining the mean size and colony number. By treating cells with an inhibitor of clonogenic growth (PTC-209), we show that our modified protocol is suitable for comprehensive (broad concentration range, addition of technical replicates) concentration- and time-resolved analysis of the effect of substances or treatments on clonogenic growth. In summary, this protocol represents a time- and cost-effective alternative to the commonly used 6-well protocol (with endpoint staining) and also provides additional information about the kinetics of clonogenic growth.

Long non-coding RNA CASC2 enhanced cisplatin-induced viability inhibition of non-small cell lung cancer cells by regulating the PTEN/PI3K/Akt pathway through down-regulation of miR-18a and miR-21

Long non-coding RNA cancer susceptibility candidate 2 (lncRNA CASC2) is a tumor suppressor and has been proved to contribute to chemotherapy efficacy. However, the effect of CASC2 on cisplatin cytotoxicity in non-small cell lung cancer (NSCLC) is unclear. The present study aimed to investigate the role of CASC2 in regulating cisplatin cytotoxicity in NSCLC cells. Herein, we found that CASC2 was low-expressed, while miR-18a and miR-21 were over-expressed in NSCLC cell lines. CASC2 enhanced the inhibition effect of cisplatin on cell viability. Down-regulation of miR-18a and miR-21 exhibited the similar effect to CASC2 and mimics of miR-18a and miR-21 displayed the opposite effect to CASC2. MiR-18a and miR-21 were two targets of CASC2 in NSCLC. PTEN was found to be a target of miR-18a and miR-21 in NSCLC. CASC2 overexpression increased PTEN expression level and reduced the ratio of p-Akt/Akt. MiR-18a or miR-21 mimics attenuated the effect of CASC2 overexpression on the PTEN expression and ratio of p-Akt/Akt. The results suggested that CASC2 enhanced cisplatin-induced viability inhibition of NSCLC cells via PTEN/PI3K/Akt pathway through suppressing miR-18a and miR-21 expression.

Long non-coding RNA cancer susceptibility candidate 2 (lncRNA CASC2) is a tumor suppressor and has been proved to contribute to chemotherapy efficacy.