Nuclear Localization of BRAFV600E Is Associated with HMOX-1 Upregulation and Aggressive Behavior of Melanoma Cells

Background: Previously, we have demonstrated that nuclear BRAFV600E is associated with melanoma aggressiveness and vemurafenib resistance. However, the underlying mechanisms of how nuclear localization of BRAFV600E promotes cell aggressiveness have not yet been investigated. Despite therapeutic advancements targeting cutaneous melanoma, unknown cellular processes prevent effective treatment for this malignancy, prompting an urgent need to identify new biological targets. This study aims to explore the association of inducible heme oxygenase 1 (HMOX-1) with nuclear BRAFV600E in promoting melanoma aggressiveness. Methods: Proteomics analysis was performed to identify the interacting partner(s) of nuclear BRAFV600E. Immunohistochemistry was applied to evaluate the levels of HMOX-1 and nuclear BRAFV600E expression in melanoma and adjacent healthy tissues. Immunofluorescence assessed the nuclear localization of BRAFV600E in vemurafenib-resistant A375R melanoma cells. Further study of HMOX-1 knockdown or BRAFV600E overexpression in melanoma cells suggested a role for HMOX-1 in the regulation of cell proliferation in vivo and in vitro. Finally, Western blot analysis was performed to confirm the pathway by which HMOX-1 mediates Akt signaling. Results: Proteomics results showed that HMOX-1 protein expression was 10-fold higher in resistant A375R cells compared to parental counterpart cells. In vitro and in vivo results illustrate that nuclear BRAFV600E promotes HMOX-1 overexpression, whereas HMOX-1 reduction represses melanoma cell proliferation and tumor growth. Mechanistic studies revealed that HMOX-1 was associated with nuclear BRAFV600E localization, thus promoting melanoma proliferation via a persistent activation of the AKT pathway. Conclusions: Our results highlight a previously unknown mechanism in which the nuclear BRAFV600E/HMOX-1/AKT axis plays an essential role in melanoma cell proliferation. Targeting HMOX-1 could be a novel method for treating melanoma patients who develop BRAF inhibitor resistance.

Vitamin D Enhances Anticancer Properties of Cediranib, a VEGFR Inhibitor, by Modulation of VEGFR2 Expression in Melanoma Cells

Regardless of the recent groundbreaking introduction of personalized therapy, melanoma continues to be one of the most lethal skin malignancies. Still, a substantial proportion of patients either fail to respond to the therapy or will relapse over time, representing a challenging clinical problem. Recently, we have shown that vitamin D enhances the effectiveness of classical chemotherapeutics in the human malignant melanoma A375 cell line. In search for new combination strategies and adjuvant settings to improve melanoma patient outcomes in the current study, the effects of cediranib (AZD2171), an oral tyrosine kinase inhibitor of VEGFR1-3, PDGFR, and c-KIT, used in combination either with 1,25(OH)2D3 or with low-calcemic analog calcipotriol were tested on four human malignant melanoma cell lines (A375, MNT-1, RPMI-7951, and SK-MEL-28). Melanoma cells were pretreated with vitamin D and subsequently exposed to cediranib. We observed a marked decrease in melanoma cell proliferation (A375 and SK-MEL-28), G2/M cell cycle arrest, and a significant decrease in melanoma cell mobility in experimental conditions used (A375). Surprisingly, concurrently with a very desirable decrease in melanoma cell proliferation and mobility, we noticed the upregulation of VEGFR2 at both protein and mRNA levels. No effect of vitamin D was observed in MNT-1 and RPMI-7951 melanoma cells. It seems that vitamin D derivatives enhance cediranib efficacy by modulation of VEGFR2 expression in melanoma cells expressing VEGFR2. In conclusion, our experiments demonstrated that vitamin D derivatives hold promise as novel adjuvant candidates to conquer melanoma, especially in patients suffering from vitamin D deficiency. However, further extensive research is indispensable to reliably assess their potential benefits for melanoma patients.

IRF4-activated TEX41 promotes the malignant behaviors of melanoma cells by targeting miR-103a-3p/C1QB axis

Background Malignant melanoma is an aggressive skin cancer and a tumor of melanocytic origin. Recent studies have suggested that long non-coding RNAs (lncRNAs) play crucial regulatory roles in multiple malignancies, including melanoma. Testis expressed 41 (TEX41) is a relatively new lncRNA whose mechanism in melanoma remains vague. Aims This study aimed to explore the role and specific mechanism of TEX41 in melanoma. Methods The expression of genes involved in this study was determined by qRT-PCR. Functional assays were conducted to analyze the role of relevant genes in melanoma cells. The interaction between TEX41 promoter and IRF4 as well as the relationship among TEX41, miR-103a-3p and C1QB was verified by mechanism assays. Results IRF4 up-regulated TEX41 at the transcriptional level in melanoma cells. TEX41 knockdown hindered melanoma cell proliferation, migration and invasion while promoting cell apoptosis. TEX41 bound to miR-103a-3p and regulated C1QB. The suppressive impact of TEX41 depletion on melanoma cell malignant behaviors could be counteracted by miR-103a-3p inhibition or C1QB overexpression. Moreover, IRF4 could facilitate melanoma cell growth via up-regulating C1QB. Conclusions IRF4-activated TEX41 sequestered miR-103a-3p and modulated C1QB to promote melanoma cell malignant behaviors, for which TEX41 might be regarded as a potential therapeutic target for melanoma.

UBTF facilitates melanoma progression via modulating MEK1/2-ERK1/2 signalling pathways by promoting GIT1 transcription

Background UBTF is an HMGB-box DNA binding protein and a necessary Pol I/Pol II basal transcription factor. It has been found that UBTF involves in carcinogenesis and progression of a few cancers. Nevertheless, the the biological function and potential molecular mechanism of UBTF in melanoma are still not clear and need to be clarified. Methods UBTF and GIT1 expressions in melanoma specimens and cell lines were examined by quantitative real-time PCR (qRT-PCR) and Western blot. MTT and colony formation assays were used to investigate the effects of UBTF and GIT1 on melanoma cell proliferation. Cell cycle and apoptosis assays were detected by flow cytometry. Tumor formation assay was used to analyze the effect of UBTF on melanoma growth. Bioinformatics predicting, chromatin immunoprecipitation (ChIP)-qRT-PCR and reporter gene assay were fulfilled for verifing GIT1 as UBTF targeting gene. Results Here we reported that UBTF mRNA and protein expressions were upregulated in primary melanoma specimens and cell lines. UBTF overexpression facilitated melanoma cell proliferation and cell cycle progression and restrained. Silencing UBTF suppressed cell multiplication, cell cycle progression and tumor growth, and promoted apoptosis. UBTF expression was positively related with GIT1 expression in human melanoma tissues. It was verified that UBTF promoted GIT1 transcription in melanoma cells through binding to the promoter region of GIT1. Furthermore, GIT1 overexpression promoted melanoma cell growth and suppressed apoptosis. Knockdown of GIT1 inhibited cell multiplication and induced apoptosis. Overexpression of GIT1 eliminated the effects of silencing UBTF on melanoma cells. Importantly, UBTF activated MEK1/2-ERK1/2 signalling pathways by upregulating GIT1 expression. Conclusions Our study demonstrates that UBTF promotes melanoma cell proliferation and cell cycle progression by promoting GIT1 transcription, thereby activating MEK1/2-ERK1/2 signalling pathways. The findings indicate that UBTF plays a crucial function in melanoma and may be a potential therapeutic target for the treatment of this disease.

LncRNA POU3F3 promotes melanoma cell proliferation by downregulating lncRNA MEG3

Background LncRNA POU3F3 (POU3F3) is overexpressed and plays oncogenic roles in esophageal squamous-cell carcinomas. LncRNA MEG3 (MEG3) has been characterized as a tumor suppressive lncRNA in different types of cancer. Our preliminary deep sequencing analysis revealed the inverse correlation between POU3F3 and MEG2 across melanoma tissues, indicating the interaction between them in melanoma. Therefore, this study was performed to investigate the crosstalk between POU3F3 and MEG3 in melanoma. Methods Tumor and adjacent healthy tissues collected from 60 melanoma patients were subjected to RNA extractions and RT-qPCRs to analyze the differential expression of POU3F3 and MEG2 in melanoma. In melanoma cells, POU3F3 and MEG2 were overexpressed to study the interactions between them. CCK-8 assays were performed to analyze the roles of POU3F3 and MEG2 in regulating melanoma cell proliferation. Results We found that POU3F3 was upregulated, while lncRNA MEG3 was downregulated in melanoma. Expression levels of POU3F3 and MEG3 were inversely correlated across tumor tissues. In vitro experiments showed that POU3F3 overexpression decreased MEG3 expression in melanoma cells, while MEG3 overexpression failed to affect POU3F3. POU3F3 overexpression increased melanoma cell proliferation, while MEG3 overexpression decreased melanoma cell proliferation. In addition, rescue experiments showed that MEG3 overexpression attenuated the enhancing effects of POU3F3 overexpression. Conclusion POU3F3 may promote melanoma cell proliferation by downregulating MEG3.

Targeting grainyhead-like transcription factor 2/Snail2 with chitosan-lipid nanoparticles inhibits melanoma progression

The grainyhead-like transcription factor 2 (GRHL2) has been reported to be involved in the progression of several malignant tumors; however, its expression and function are still unclear. This study confirmed that GRHL2 expression increased in melanoma tissue and cell lines. We used a novel chitosan-lipid nanoparticle (CS-LNP) nanomaterial to form CS-LNP/plasmids and CS-LNP/siRNAs to upregulate/downregulate GRHL2. The results indicated that GRHL2 promoted melanoma cell proliferation and migration by upregulating the EMT-related snail2 gene, and GRHL2 function in melanoma cells was partially reversed by snail2 knockdown. GRHL2/snail2 could be a potential target in melanoma treatment.