Advances in targeted therapy for unresectable melanoma: new drugs and combinations

Advances in dual-targeting inhibitors of HDAC6 for cancer treatment

Histone Deacetylase 6 (HDAC6) is an essential regulator of histone acetylation processes, exerting influence on a multitude of cellular functions such as cell motility, endocytosis, autophagy, apoptosis, and protein trafficking through its deacetylation activity. The significant implications of HDAC6 in diseases such as cancer, neurodegenerative disorders, and immune disorders have motivated extensive investigation into the development of specific inhibitors targeting this enzyme for therapeutic purposes. Single targeting drugs carry the risk of inducing drug resistance, thus prompting exploration of dual targeting therapy which offers the potential to impact multiple signaling pathways simultaneously, thereby lowering the likelihood of resistance development. While pharmacological studies have exhibited promise in combined therapy involving HDAC6, challenges related to potential drug interactions exist. In response to these challenges, researchers are investigating HDAC6 hybrid molecules which enable the concomitant targeting of HDAC6 and other key proteins, thus enhancing treatment efficacy while mitigating side effects and reducing the risk of resistance compared to traditional combination therapies. The published design strategies for dual targeting inhibitors of HDAC6 are summarized and discussed in this review. This will provide some valuable insights into more novel HDAC6 dual targeting inhibitors to meet the urgent need for innovative therapies in oncology and other related fields.

Pharmacophore-based virtual screening of ZINC database, molecular modeling and designing new derivatives as potential HDAC6 inhibitors

To date, many HDAC6 inhibitors have been identified and developed but none is clinically approved as of now. Through this study, we aim to obtain novel HDAC6 selective inhibitors and provide new insights into the detailed structural design of potential HDAC6 inhibitors. A HypoGen-based 3D QSAR HDAC6 pharmacophore was built and used as a query model to screen approximately 8 million ZINC database compounds. First, the ZINC Database was filtered using ADMET, followed by pharmacophore-based library screening. Using fit value and estimated activity cutoffs, a final set of 54 ZINC hits was obtained that were further investigated using molecular docking with the crystal structure of human histone deacetylase 6 catalytic domain 2 in complex with Trichostatin A (PDB ID: 5EDU). Through detailed in silico screening of the ZINC database, we shortlisted three hits as the lead molecules for designing novel HDAC6 inhibitors with better efficacy. Docking with 5EDU, followed by ADMET and TOPKAT analysis of modified ZINC hits provided 9 novel potential HDAC6 inhibitors that possess better docking scores and 2D interactions as compared to the control ZINC hit molecules. Finally, a 50 ns MD analysis run followed by Protein-Ligand Interaction Energy (PLIE) analysis of the top scored hits provided a novel molecule N1 that showed promisingly similar results to that of Ricolinostat (a known HDAC6 inhibitor). The comparable result of the designed hits to established HDAC6 inhibitors suggests that these compounds might prove to be successful HDAC6 inhibitors in future. Designed novel hits that might act as good HDAC6 inhibitors derived from ZINC database using combined molecular docking and modeling approaches.

Recent development of selective inhibitors targeting the HDAC6 as anti-cancer drugs: Structure, function and design

HDAC6, a member of the histone deacetylase family, mainly is a cytosolic protein and regulates cell growth by acting on non-histone substrates, such as α -tubulin, cortactin, heat shock protein HSP90, programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1), that are closely related to the proliferation, invasion, immune escape and angiogenesis of cancer tissues. The approved drugs targeting the HDACs are all pan-inhibitors and have many side effects due to their lack of selectivity. Therefore, development of selective inhibitors of HDAC6 has attracted much attention in the field of cancer therapy. In this review, we will summarize the relationship between HDAC6 and cancer, and discuss the design strategies of HDAC6 inhibitors for cancer treatment in recent years.

Combination Therapy of Curcumin and Disulfiram Synergistically Inhibits the Growth of B16-F10 Melanoma Cells by Inducing Oxidative Stress

Oxidative stress plays a central role in the pathophysiology of melanoma. Curcumin (CUR) is a polyphenolic phytochemical that stimulates reactive oxygen species (ROS) production, while disulfiram (DSS) is a US FDA-approved drug for the treatment of alcoholism that can act by inhibiting the intracellular antioxidant system. Therefore, we hypothesized that they act synergistically against melanoma cells. Herein, we aimed to study the antitumor potential of the combination of CUR with DSS in B16-F10 melanoma cells using in vitro and in vivo models. The cytotoxic effects of different combination ratios of CUR and DSS were evaluated using the Alamar Blue method, allowing the production of isobolograms. Apoptosis detection, DNA fragmentation, cell cycle distribution, and mitochondrial superoxide levels were quantified by flow cytometry. Tumor development in vivo was evaluated using C57BL/6 mice bearing B16-F10 cells. The combinations ratios of 1:2, 1:3, and 2:3 showed synergic effects. B16-F10 cells treated with these combinations showed improved apoptotic cell death and DNA fragmentation. Enhanced mitochondrial superoxide levels were observed at combination ratios of 1:2 and 1:3, indicating increased oxidative stress. In vivo tumor growth inhibition for CUR (20 mg/kg), DSS (60 mg/kg), and their combination were 17.0%, 19.8%, and 28.8%, respectively. This study provided data on the potential cytotoxic activity of the combination of CUR with DSS and may provide a useful tool for the development of a therapeutic combination against melanoma.

Dimethyl Fumarate Combined With Vemurafenib Enhances Anti-Melanoma Efficacy via Inhibiting the Hippo/YAP, NRF2-ARE, and AKT/mTOR/ERK Pathways in A375 Melanoma Cells

Melanoma is a deadly form of skin cancer with high rates of resistance to traditional chemotherapy and radiotherapy. BRAF inhibitors (BRAFi) can achieve initial efficacy when used to treat melanoma patients, but drug resistance and relapse are common, emphasizing the need for new therapeutic strategies. Herein, we reported that combination of dimethyl fumarate (DMF) and vemurafenib (Vem) inhibited melanoma cell proliferation more significantly and induced more cell death than single agent did both in vitro and in vivo. DMF/Vem treatment induced cell death through inhibiting the expression and transcriptional activity of NRF2 thereby resulting in more reactive oxygen species (ROS) and via inhibiting the expression of YAP, a key downstream effector of Hippo pathway. DMF/Vem treatment also reduced phosphorylation of AKT, 4EBP1, P70S6K and ERK in AKT/mTOR/ERK signaling pathways. RNA-seq analysis revealed that DMF/Vem treatment specifically suppressed 4561 genes which belong to dozens of cell signaling pathways. These results indicated that DMF/Vem treatment manifested an enhanced antitumor efficacy through inhibiting multiple cell signaling pathways, and thus would be a novel promising therapeutic approach targeted for melanoma.

HDAC6 inhibitor WT161 performs anti-tumor effect on osteosarcoma and synergistically interacts with 5-FU

BACKGROUND

WT161, as a selective HDAC6 inhibitor, has been shown to play anti-tumor effects on several kinds of cancers. The aim of the present study is to explore the roles of WT161 in osteosarcoma and its underlying mechanisms.

METHODS

The anti-proliferative effect of WT161 on osteosarcoma cells was examined using MTT assay and colony formation assay. Cell apoptosis was analyzed using flow cytometer. The synergistic effect was evaluated by isobologram analysis using CompuSyn software. The osteosarcoma xenograft models were established to evaluate the anti-proliferative effect of WT161 in vivo.

RESULTS

WT161 suppressed the cell growth and induced apoptosis of osteosarcoma cells in a dose- and time-dependent manner. Mechanistically, we found that WT161 treatment obviously increased the protein level of PTEN and decreased the phosphorylation level of protein kinase-B (AKT). More importantly, WT161 showed synergistic inhibition with 5-FU on osteosarcoma cells in vitro and in vivo.

CONCLUSIONS

These results indicate that WT161 inhibits the growth of osteosarcoma through PTEN and has a synergistic efficiency with 5-FU.

Small Molecules Targeting HATs, HDACs, and BRDs in Cancer Therapy

Evidence for research over the past decade shows that epigenetic regulation mechanisms run through the development and prognosis of tumors. Therefore, small molecular compounds targeting epigenetic regulation have become a research hotspot in the development of cancer therapeutic drugs. According to the obvious abnormality of histone acetylation when tumors occur, it suggests that histone acetylation modification plays an important role in the process of tumorigenesis. Currently, as a new potential anti-cancer therapeutic drugs, many active small molecules that target histone acetylation regulatory enzymes or proteins such as histone deacetylases (HDACs), histone acetyltransferase (HATs) and bromodomains (BRDs) have been developed to restore abnormal histone acetylation levels to normal. In this review, we will focus on summarizing the changes of histone acetylation levels during tumorigenesis, as well as the possible pharmacological mechanisms of small molecules that target histone acetylation in cancer treatment.

IGFBP2 regulates PD-L1 expression by activating the EGFR-STAT3 signaling pathway in malignant melanoma

Immunotherapy targeting the PD-1/PD-L1 receptor has achieved great success in melanoma patients. Although many studies have addressed the underlying mechanisms involved in the blockade of PD-1/PD-L1 and the consequent modulation of the immune system, the mechanisms of PD-L1 upregulation and reliable biomarkers to predict the efficacy of anti-PD-1/PD-L1 therapy remain unknown. The present study demonstrates the correlation between IGFBP2 and PD-L1, revealing a novel immune-associated tumor function of IGFBP2 in facilitating nuclear accumulation of EGFR and activation of the EGFR/STAT3/PD-L1 signaling pathway in melanoma cells. Our results also suggest that combined IGFBP2 and PD-L1 expression has the potential to predict the efficacy of anti-PD-1 treatment for malignant melanoma; because the combination of high IGFBP2 and PD-L1 expression characterizes melanoma patients with worse overall survival and is associated with a better immune ecosystem. These characteristics have been confirmed by both in vitro and in vivo data. Consequently, IGFBP2 regulates PD-L1 expression by activating the EGFR-STAT3 signaling pathway and its function as a PD-L1 regulator might suggest novel therapeutic approach for melanoma.

Extending the use of tadalafil scaffold: Development of novel selective phosphodiesterase 5 inhibitors and histone deacetylase inhibitors

Herein we present the synthesis and characterization of a novel chemical series of tadalafil analogues that display different pharmacological profiles. Compounds that have the 6R, 12aR configuration and terminal carboxylic acid group at the side chain arising from the piperazinedione nitrogen were potent PDE5 inhibitors, with compound 11 having almost equal potency to tadalafil and superior selectivity over PDE11, the most common off-target for tadalafil. Modifying the stereochemistry into 6S, 12aS configuration and adopting the hydroxamic acid moiety as a terminal group gave rise to compounds that only inhibited HDAC. Dual PDE5/HDAC inhibition could be achieved with compounds having 6R, 12aR configuration and hydroxamic acid moiety as a terminal group. The anticancer activity of the synthesized compounds was evaluated against a diverse number of cell lines of different origin. The compounds elicited anticancer activity against cell lines belonging to lymphoproliferative cancer as well as solid tumors. Despite the previous reports suggesting anticancer activity of PDE5 inhibitors, the growth inhibitory activity of the compounds seemed to be solely dependent on HDAC inhibition. Compound 26 (pan HDAC IC50 = 14 nM, PDE5 IC50 = 46 nM) displayed the most potent anticancer activity in the present series and was shown to induce apoptosis in Molt-4 cells. HDAC isoform selectivity testing for compound 26 showed that it is more selective for HDAC6 and 8 over HDAC1 by more than 20-fold.

T-Type Calcium Channels as Potential Therapeutic Targets in Vemurafenib-Resistant BRAFV600E Melanoma

Melanoma is a malignant neoplasia that is highly resistant to chemotherapy and radiotherapy and is associated with poor prognosis in advanced stage. Targeting melanoma that harbors the common BRAF^V600E mutation with kinase inhibitors, such as vemurafenib, reduces tumor burden, but these tumors frequently acquire resistance to these drugs. We previously proposed that T-type calcium channel (TTCC) expression may serve as a biomarker for melanoma progression and prognosis, and we showed that TTCC blockers reduce migration and invasion rates because of autophagy blockade only in BRAF^V600E-mutant melanoma cells. Here, we demonstrated that high expression of the TTCC Cav3.1 isoform is related to autophagic status in vemurafenib-resistant BRAF^V600E-mutant melanoma cells and human biopsies, and in silico analysis revealed an enrichment of Cav3.1 expression in post-treatment melanomas. We also demonstrated that the TTCC blocker mibefradil induces apoptosis and impairs migration and invasion via inhibition of autophagy in resistant melanoma cells and mouse xenograft models. Moreover, we identified an association between PTEN status and Cav3.1 expression in these cells as a marker of sensitivity to combination therapy in resistant cells. Together, our results suggest that TTCC blockers offer a potential targeted therapy in resistant BRAF^V600E-mutant melanoma and a therapeutic strategy to reduce progression toward BRAF inhibitor resistance.

Biotin functionalized PEGylated poly(amidoamine) dendrimer conjugate for active targeting of paclitaxel in cancer

In the current study, we employed poly(amidoamine) (PAMAM) dendrimers of generation 4 (G4) to deliver paclitaxel (PTX), a poorly soluble anti-cancer agent precisely to cancer cells via its conjugation on dendrimer surface. Further, G4 PAMAM has been PEGylated (PEG) and tagged with Biotin, an essential micronutrient for cellular functions, receptors of which are overexpressed in certain cancers. The synthesized multifunctional conjugates were characterized by ¹H NMR and zeta potential analysis techniques. In addition, the conjugates were evaluated in vitro in cell monolayers and 3D spheroids of biotin receptor over-expressed A549 cell line (human non-small cell lung cancer). G4 PTX PEG-Biotin conjugate penetrated at significantly higher extent in monolayers as well as spheroids as studied by flow cytometry and confocal microscopy by visualizing the cells at varied depth. The G4 PTX PEG-Biotin conjugate demonstrated higher cytotoxicity compared to free PTX and G4 PTX PEG conjugate as assessed by MTT assay in monolayers and Presto Blue assay in detached spheroidal cells. G4 PTX PEG-Biotin demonstrated significant inhibition of growth of tumor spheroids. Therefore, the newly synthesized biotin anchored PTX-conjugated dendrimer system is promising and could be further explored for efficiently delivering PTX to biotin receptor overexpressed cancers.

Synergistic inhibition of melanoma xenografts by Brequinar sodium and Doxorubicin

Malignant melanoma continues to be a fatal disease for which novel and long-term curative breakthroughs are desired. One such innovative idea would be to assess combination therapeutic treatments - by way of combining two potentially effective and very different therapy. Previously, we have shown that DHODH inhibitors, A771726 and Brequinar sodium (BQR) induced cell growth impairment in melanoma cells. Similar results were seen with DHODH RNA interference (shRNA). In the present study, we showed that combination of BQR with doxorubicin resulted in synergistic and additive cell growth inhibition in these cells. In addition, in vivo studies with this combination of drugs demonstrated an almost 90% tumor regression in nude mice bearing melanoma tumors. Cell cycle regulatory proteins, cyclin B₁ and its binding partner pcdc-2 and p21 were significantly downregulated and upregulated respectively following the combined treatment. Given that we have observed synergistic effects with BQR and doxorubicin, both in vitro and in vivo, these drugs potentially represent a new combination in the targeted therapy of melanoma.

Histone deacetylase 6 in cancer

Histone acetylation and deacetylation are important epigenetic mechanisms that regulate gene expression and transcription. Histone deacetylase 6 (HDAC6) is a unique member of the HDAC family that not only participates in histone acetylation and deacetylation but also targets several nonhistone substrates, such as α-tubulin, cortactin, and heat shock protein 90 (HSP90), to regulate cell proliferation, metastasis, invasion, and mitosis in tumors. Furthermore, HDAC6 also upregulates several critical factors in the immune system, such as program death receptor-1 (PD-1) and program death receptor ligand-1 (PD-L1) receptor, which are the main targets for cancer immunotherapy. Several selective HDAC6 inhibitors are currently in clinical trials for cancer treatment and bring hope for patients with malignant tumors. A fuller understanding of HDAC6 as a critical regulator of many cellular pathways will help further the development of targeted anti-HDAC6 therapies. Here, we review the unique features of HDAC6 and its role in cancer, which make HDAC6 an appealing drug target.

Seed targeting with tiny anti-miR-1297 inhibits EMT in melanoma cells

MicroRNAs (miRNAs) are small, noncoding RNAs that have tissue- and cell-specific expression. They have the ability to regulate the malignant proliferation and transformation of tumour cells. The research focussed on the expression and role of miR-1297 in melanoma. We firstly found that miR-1297 is up-regulated in melanoma tissues and cell lines. Functionally, phosphatase and tension homology deleted on chromsome ten gene (PTEN) was used as a potential target for miR-1297 and detected using Western blotting and immunohistochemistry (IHC). We then used chemical synthesis of anti-miR1297 to explore the influence on melanoma cells and examined the effects on A375 cell proliferation using MTT and western blotting methods. The results showed that anti-miR-1297 transfected A375 cells could inhibit the growth. Furthermore, transfection with anti-miR-1297 reduced PTEN protein expression and partially restrained A375 cells proliferation, migration and reversed Epithelial-Mesenchymal Transition (EMT) progression. In conclusion, we tentatively put forward that miR-1297 might be the key oncomiR in melanoma, and seed-targeted anti-miR-1297 might serve as a new tactic for miR-1297-based therapies.

CAPN1 is a novel binding partner and regulator of the tumor suppressor NF1 in melanoma

Neurofibromin 1 (NF1), a tumor suppressor that negatively regulates RAS through its GTPase activity, is highly mutated in various types of sporadic human cancers, including melanoma. However, the binding partners of NF1 and the pathways in which it is involved in melanoma have not been characterized in an in depth manner. Utilizing a mass spectrometry analysis of NF1 binding partners, we revealed Calpain1 (CAPN1), a calcium-dependent neutral cysteine protease, as a novel NF1 binding partner that regulates NF1 degradation in melanoma cells. ShRNA-mediated knockdown of CAPN1 or treatment with a CAPN1 inhibitor stabilizes NF1 protein levels, downregulates AKT signaling and melanoma cell growth. Combination treatment of Calpain inhibitor I with MEKi Trametinib in different melanoma cells is more effective in reducing melanoma cell growth compared to treatment with Trametinib alone, suggesting that this combination may have a therapeutic potential in melanoma. This novel mechanism for regulating NF1 in melanoma provides a molecular basis for targeting CAPN1 in order to stabilize NF1 levels and, in doing so, suppressing Ras activation; this mechanism can be exploited therapeutically in melanoma and other cancers.

Current status and future direction in the management of malignant melanoma

The incidence of malignant melanoma is increasing rapidly on a global scale. Although some types of melanoma, for example primary cutaneous melanoma, can be managed by surgery, metastatic melanoma cannot and it has a high mortality rate. Both oncogene and immune-targeted strategies have shown marked efficacy in some patients, but their effect on overall survival is still variable. Therefore, newer therapeutic approaches are needed. Fortunately, new advances in molecular medicine have led to an understanding of an individual patient's cancer at the genomic level. This information is now being used in all stages of cancer treatment including diagnosis, treatment selection, and treatment monitoring. This new strategy of personalized medicine may lead to marked shifts in immunotherapeutic treatment approaches such as individualized cancer vaccines and adoptive transfer of genetically modified T cells. This review provides an overview of recent approaches in cancer research and expected impact on the future of treatment for metastatic melanoma.

CD147 silencing inhibits tumor growth by suppressing glucose transport in melanoma

Melanoma is a very malignant disease and there are still no effective treatments. CD147 participates in the carcinogenesis of multiple human cancers and GLUT-1, as a glucose transporter, is associated with tumor growth. However, the function of CD147 and GLUT-1 in melanoma have not been completely understood. Thus, in this study we investigated the expression of CD147 and GLUT-1 in melanoma tissue, which were overexpressed compared with that in nevus tissue. In addition, CD147 and GLUT-1 were co-localized in the cytoplasm of human melanoma A375 cells. Immunoprecipitation proved that CD147 interacted with GLUT-1 at D105-199. Silencing CD147 by specific siRNA could downregulate GLUT-1 level via inhibiting PI3K/Akt signaling and decrease glucose uptake in A375 cells. In vivo experiments also supported that CD147 knockdown suppressed the tumor growth in melanoma subcutaneous mice model, observed by micro PET/CT. Our results could help validate CD147 as a new therapeutic target for treating melanoma.

T-type calcium channels drive migration/invasion in BRAFV600E melanoma cells through Snail1

Melanoma is a malignant tumor derived from melanocytes. Once disseminated, it is usually highly resistant to chemotherapy and is associated with poor prognosis. We have recently reported that T-type calcium channels (TTCCs) are overexpressed in melanoma cells and play an important role in melanoma progression. Importantly, TTCC pharmacological blockers reduce proliferation and deregulate autophagy leading to apoptosis. Here, we analyze the role of autophagy during migration/invasion of melanoma cells. TTCC Cav3.1 and LC3-II proteins are highly expressed in BRAFV600E compared with NRAS mutant melanomas, both in cell lines and biopsies. Chloroquine, pharmacological blockade, or gene silencing of TTCCs inhibit the autophagic flux and impair the migration and invasion capabilities, specifically in BRAFV600E melanoma cells. Snail1 plays an important role in motility and invasion of melanoma cells. We show that Snail1 is strongly expressed in BRAFV600E melanoma cells and patient biopsies, and its expression decreases when autophagy is blocked. These results demonstrate a role of Snail1 during BRAFV600E melanoma progression and strongly suggest that targeting macroautophagy and, particularly TTCCs, might be a good therapeutic strategy to inhibit metastasis of the most common melanoma type (BRAFV600E).

Essential role for acid sphingomyelinase-inhibited autophagy in melanoma response to cisplatin

The sphingolipid metabolising enzyme Acid Sphingomyelinase (A-SMase) has been recently shown to inhibit melanoma progression and correlate inversely to tumour grade. In this study we have investigated the role of A-SMase in the chemo-resistance to anticancer treatmentusing mice with melanoma allografts and melanoma cells differing in terms of expression/activity of A-SMase. Since autophagy is emerging as a key mechanism in tumour growth and chemo-resistance, we have also investigated whether an action of A-SMase in autophagy can explain its role. Melanoma sensitivity to chemotherapeutic agent cisplatin in terms of cell viability/apoptosis, tumour growth, and animal survival depended directly on the A-SMase levels in tumoural cells. A-SMase action was due to inhibition of autophagy through activation of Akt/mammalian target of rapamycin (mTOR) pathway. Treatment of melanoma-bearing mice with the autophagy inhibitor chloroquine restored sensitivity to cisplatin of tumours expressing low levels of A-SMase while no additive effects were observed in tumours characterised by sustained A-SMase levels. The fact that A-SMase in melanomas affects mTOR-regulated autophagy and plays a central role in cisplatin efficacy encourages pre-clinical testing on the modulation of A-SMase levels/activity as possible novel anti-neoplastic strategy.

Effect of dacarbazine on CD44 in live melanoma cells as measured by atomic force microscopy-based nanoscopy

CD44 ligand-receptor interactions are known to be involved in regulating cell migration and tumor cell metastasis. High expression levels of CD44 correlate with a poor prognosis of melanoma patients. In order to understand not only the mechanistic basis for dacarbazine (DTIC)-based melanoma treatment but also the reason for the poor prognosis of melanoma patients treated with DTIC, dynamic force spectroscopy was used to structurally map single native CD44-coupled receptors on the surface of melanoma cells. The effect of DTIC treatment was quantified by the dynamic binding strength and the ligand-binding free-energy landscape. The results demonstrated no obvious effect of DTIC on the unbinding force between CD44 ligand and its receptor, even when the CD44 nanodomains were reduced significantly. However, DTIC did perturb the kinetic and thermodynamic interactions of the CD44 ligand-receptor, with a resultant greater dissociation rate, lower affinity, lower binding free energy, and a narrower energy valley for the free-energy landscape. For cells treated with 25 and 75 μg/mL DTIC for 24 hours, the dissociation constant for CD44 increased 9- and 70-fold, respectively. The CD44 ligand binding free energy decreased from 9.94 for untreated cells to 8.65 and 7.39 kcal/mol for DTIC-treated cells, which indicated that the CD44 ligand-receptor complexes on DTIC-treated melanoma cells were less stable than on untreated cells. However, affinity remained in the micromolar range, rather than the millimolar range associated with nonaffinity ligands. Hence, the CD44 receptor could still be activated, resulting in intracellular signaling that could trigger a cellular response. These results demonstrate DTIC perturbs, but not completely inhibits, the binding of CD44 ligand to membrane receptors, suggesting a basis for the poor prognosis associated with DTIC treatment of melanoma. Overall, atomic force microscopy-based nanoscopic methods offer thermodynamic and kinetic insight into the effect of DTIC on the CD44 ligand-binding process.

Two novel atypical PKC inhibitors; ACPD and DNDA effectively mitigate cell proliferation and epithelial to mesenchymal transition of metastatic melanoma while inducing apoptosis

Atypical protein kinase Cs (aPKC) are involved in cell cycle progression, tumorigenesis, cell survival and migration in many cancers. We believe that aPKCs play an important role in cell motility of melanoma by regulating cell signaling pathways and inducing epithelial to mesenchymal transition (EMT). We have investigated the effects of two novel aPKC inhibitors; 2-acetyl-1,3-cyclopentanedione (ACPD) and 3,4-diaminonaphthalene-2,7-disulfonic acid (DNDA) on cell proliferation, apoptosis, migration and invasion of two malignant melanoma cell lines compared to normal melanocytes. Molecular docking data suggested that both inhibitors specifically bind to protein kinase C-zeta (PKC-ζ) and PKC-iota (PKC-ι) and kinase activity assays were carried out to confirm these observations. Both inhibitors decreased the levels of total and phosphorylated PKC-ζ and PKC-ι. Increased levels of E-cadherin, RhoA, PTEN and decreased levels of phosphorylated vimentin, total vimentin, CD44, β-catenin and phosphorylated AKT in inhibitor treated cells. This suggests that inhibition of both PKC-ζ and PKC-ι using ACPD and DNDA downregulates EMT and induces apoptosis in melanoma cells. We also carried out PKC-ι and PKC-ζ directed siRNA treatments to prove the above observations. Immunoprecipitation data suggested an association between PKC-ι and vimentin and PKC-ι siRNA treatments confirmed that PKC-ι activates vimentin by phosphorylation. These results further suggested that PKC-ι is involved in signaling pathways which upregulate EMT and which can be effectively suppressed using ACPD and DNDA. Our results summarize that melanoma cells proliferate via aPKC/AKT/NF-κB mediated pathway while inducing the EMT via PKC-ι/Par6/RhoA pathway. Overall, results show that aPKCs are essential for melanoma progression and metastasis, suggesting that ACPD and DNDA can be effectively used as potential therapeutic drugs for melanoma by inhibiting aPKCs.

Detecting human melanoma cell re-differentiation following BRAF or heat shock protein 90 inhibition using photoacoustic and magnetic resonance imaging

Targeted therapies specific to the BRAF-MEK-ERK signaling pathway have shown great promise in the treatment of malignant melanoma in the last few years, with these drugs now commonly used in clinic. Melanoma cells treated using these agents are known to exhibit increased levels of melanin pigment and tyrosinase activity. In this study we assessed the potential of non-invasive imaging approaches (photoacoustic imaging (PAI) and magnetic resonance imaging (MRI)) to detect melanin induction in SKMEL28 human melanoma cells, following inhibition of Hsp90 and BRAF signaling using 17-AAG and vemurafenib, respectively. We confirmed, using western blot and spectrophotometry, that Hsp90 or BRAF inhibitor-induced melanoma cell differentiation resulted in an upregulation of tyrosinase and melanin expression levels, in comparison to control cells. This post-treatment increase in cellular pigmentation induced a significant increase in PAI signals that are spectrally identifiable and shortening of the MRI relaxation times T 1 and [Formula: see text]. This proof-of-concept study demonstrates the potential of MRI and PAI for detecting the downstream cellular changes induced by Hsp90 and BRAF-MEK-targeted therapies in melanoma cells with potential significance for in vivo imaging.

Impaired dacarbazine activation and 7-ethoxyresorufin deethylation in vitro by polymorphic variants of CYP1A1 and CYP1A2: implications for cancer therapy

OBJECTIVES

To extend our understanding of how interindividual variability mediates the efficacy of cancer treatment.

MATERIALS AND METHODS

The kinetics of dacarbazine (DTIC) N-demethylation by the most frequent polymorphic variants of CYP1A1 (T461N, I462V) and CYP1A2 (F186L, D348N, I386F, R431W, R456H) were characterized, along with kinetic parameters for the O-deethylation of the prototypic CYP1A substrate 7-ethoxyresorufin, using recombinant protein expression and high-performance liquid chromatographic techniques.

RESULTS

A reduction of ∼30% in the catalytic efficiencies (measured as in-vitro intrinsic clearance, CLint) was observed for DTIC N-demethylation by the two CYP1A1 variants relative to wild type. Although a modest increase in the CLint value for DTIC N-demethylation was observed for the CYP1A2 D348N variant relative to the wild type, the CLint for the F186L variant was reduced and the I386F, R431W, and R456H variants all showed loss of catalytic function.

CONCLUSION

Comparison of the kinetic data for DTIC N-demethylation and 7-ethoxyresorufin O-deethylation indicated that alterations in the kinetic parameters (Km, Vmax, CLint) observed with each of the CYP1A1 and CYP1A2 polymorphic variants were substrate dependent. These data indicate that cancer patients treated with DTIC who possess any of the CYP1A1-T461N and I462V variants or the CYP1A2-F186L, D348N, I386F, R431W, and R456H variants are likely to have decreased prodrug activation, and hence may respond less favorably to DTIC treatment compared with individuals with wild-type CYP1A alleles.

Immunohistochemical analysis of T-type calcium channels in acquired melanocytic naevi and melanoma

BACKGROUND

Cutaneous malignant melanoma arises from transformed melanocytes de novo or from congenital or acquired melanocytic naevi. We have recently reported that T-type Ca²⁺ channels (TT-Cs) are upregulated in human melanoma and play an important role in cell proliferation.

OBJECTIVES

To describe for the first time in formalin-fixed paraffin-embedded tissue the immunoexpression of TT-Cs in biopsies of normal skin, acquired melanocytic naevi and melanoma, in order to evaluate their role in melanomagenesis and/or tumour progression, their utility as prognostic markers and their possible use in targeted therapies.

METHODS

Tissue samples from normal skin, melanocytic naevi and melanoma were subjected to immunohistochemistry for two TT-Cs (Cav3.1, Cav3.2); markers of proliferation (Ki67), the cell cycle (cyclin D1), hypoxia (Glut1), vascularization (CD31) and autophagy (LC3); BRAF V600E mutation (VE1) and phosphatase and tensin homologue (PTEN). Immunostaining was evaluated by histoscore. In silico analysis was used to assess the prognostic value of TT-C overexpression.

RESULTS

TT-C immunoexpression increased gradually from normal skin to common naevi, dysplastic naevi and melanoma samples, but with differences in the distribution of both isoforms. Particularly, Cav3.2 expression was significantly higher in metastatic melanoma than in primary melanoma. Statistical correlation showed a linear interaction between PTEN loss/BRAF V600E/Cav3.1/LC3/ Ki67/cyclin D1/Cav3.2/Glut1. Disease-free survival (DFS) and overall survival correlated inversely with overexpression of Cav3.2. DFS also correlated inversely with overexpression of Cav3.1.

CONCLUSIONS

TT-C immunoexpression on melanocytic neoplasms is consistent with our previous in vitro studies and appears to be related to tumour progression. TT-C upregulation can be considered as a prognostic marker using The Cancer Genome Atlas database. The high expression of Cav3.2 in metastatic melanoma encourages the investigation of the use of TT-C blockers in targeted therapies.

2-phenylethynesulphonamide (PFT-μ) enhances the anticancer effect of the novel hsp90 inhibitor NVP-AUY922 in melanoma, by reducing GSH levels

Heat shock proteins (HSPs), are molecular chaperones that assist the proper folding of nascent proteins. This study aims to evaluate the antitumour effects of the hsp90 inhibitor NVP-AUY922 in melanoma, both in vitro and in vivo. Our results show that NVP-AUY922 inhibits melanoma cell growth in vitro, with down regulation of multiple signalling pathways involved in melanoma progression such as NF-ĸB and MAPK/ERK. However, NVP-AUY922 was unable to limit tumour growth in vivo. Cotreatment of A375M xenografts with NVP-AUY922 and PFT-μ, a dual inhibitor of both hsp70 and autophagy, induced a synergistic increase of cell death in vitro, and delayed tumour formation in A375M xenografts. PFT-μ depleted cells from the reduced form of glutathione (GSH) and increased oxidative stress. The oxidative stress induced by PFT-μ further enhanced NVP-AUY922-induced cytotoxic effects. These data suggest a potential therapeutic role for NVP-AUY922 used in combination with PFT-μ, in melanoma.

Clinical Characteristics of Malignant Melanoma in Southwest China: A Single-Center Series of 82 Consecutive Cases and a Meta-Analysis of 958 Reported Cases

Purpose

The present study determined the clinical characteristics and prognostic factors in patients with malignant melanoma based on a series of 82 cases from January 2009 to December 2014 in Southwest Hospital and a meta-analysis (including 12 articles) involving 958 patients in China.

Materials and methods

The database elements included basic demographic data and prognosticators which were extracted from medical records. Statistical analyses of survival, and multivariate analyses of factors associated with survival were performed using the Kaplan—Meier method, and the Cox proportional hazard model, respectively. Literatures were identified through systematic searches in PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI) and Weipu database (VIP) database for the period from inception to December 2015. The meta-analysis was conducted using R 3.1.1 meta-analysis software

Results

In this series of 82 cases, the median age of the patients was 57.50 years. Melanoma was located in the foot in 79% of patients. Sixty-one patients (74.4%) were classified as stage II-III. Thirty-two patients (39.0%) had acral malignant melanoma, and 31 patients (37.8%) had nodular malignant melanoma. The clinical characteristics of melanoma were similar to those in areas outside southwest China (from results of the meta-analysis). The median survival time was 29.50 months. The 1-year, 3-year, and 5-year survival rates were 84.1%, 39.0% and 10.9%, respectively. COX regression following multi-factor analysis showed that ulcer, tumor boundary and lymph node metastasis were associated with prognosis.

Conclusions

The clinical characteristics of melanoma in Chinese were different from those in Caucasians. Ulcer, tumor margins, and lymph node metastasis were significantly associated with prognosis. Immune therapy may prolong the median survival time of patients with acral melanoma, nodular melanoma, or stage I-III disease, although these differences were not statistically significant.

Treatment of malignant melanoma with nivolumab and vemurafenib combined with hypofractionated radiation therapy

Management of metastatic malignant melanoma is challenging. Although several new systemic therapies for metastatic malignant melanoma have recently been developed, some patients still also require radiation therapy (RT) for palliative care. However, the safety and efficacy of combining use of novel drugs with RT remain unclear. Here, we report treating a patient with rapidly growing malignant melanoma with a programmed cell death protein 1 (PD-1) inhibitor and a BRAF inhibitor together with 60 Gy of hypofractionated RT without severe adverse effects. The tumor within the radiation field exhibited a more marked response than that outside it. A combination of RT with an anti-PD-1 antibody or a BRAF inhibitor may, therefore, be a useful and tolerable approach to treating metastatic BRAF-mutant melanoma.

Vitamin E δ-tocotrienol triggers endoplasmic reticulum stress-mediated apoptosis in human melanoma cells

Malignant melanoma is the leading cause of death from skin cancer. Drug toxicity and resistance represent a serious challange for melanoma treatments. Evidence demonstrates that natural compounds may play a crucial role in cancer prevention, growth and progression. Vitamin E tocotrienols (TT) were shown to possess antitumor activity. Here, we analyzed the effects of δ-TT on melanoma cell growth and the involvement of the endoplasmic reticulum (ER) stress in this activity. The experiments were performed on human melanoma cell lines, BLM and A375. δ-TT exerted a significant proapoptotic effect on both cell lines, involving the intrinsic apoptosis pathway; importantly, this compound did not affect the viability of normal human melanocytes. In melanoma cells, δ-TT exerted its antitumor effect through activation of the PERK/p-eIF2α/ATF4/CHOP, IRE1α and caspase-4 ER stress-related branches. Salubrinal, an inhibitor of the ER stress, counteracted the cytotoxic activity of δ-TT. In vivo experiments performed in nude mice bearing A375 xenografts evidenced that δ-TT reduces tumor volume and tumor mass; importantly, tumor progression was significantly delayed by δ-TT treatment. In conclusion, δ-TT exerts a proapoptotic activity on melanoma cells, through activation of the ER stress-related pathways. δ-TT might represent an effective option for novel chemopreventive/therapeutic strategies for melanoma.

Knockdown of USP39 induces cell cycle arrest and apoptosis in melanoma

The spliceosome machinery composed of multimeric protein complexes guides precursor messenger RNAs (mRNAs) (pre-mRNAs) splicing in eukaryotic cells. Spliceosome components have been shown to be downregulated in cancer and could be a promising molecular target for anticancer therapy. The ubiquitin-specific protease 39 (USP39) is essential for pre-mRNA splicing, and upregulated USP39 expression is noted in a variety of cancers. However, the role of USP39 in the development and progression of melanoma remains unclear. In the present study, USP39 expression was found to be increased in melanoma tissues compared with that in nevus tissues. USP39 silencing via lentivirus-mediated short hairpin RNA (shRNA) significantly suppressed melanoma cell proliferation, induced G0/G1 cell cycle phase arrest, and increased apoptosis in vitro. Moreover, USP39 knockdown suppressed melanoma tumor growth in a xenograft model. In addition, USP39 silencing was associated with the increased expressions of p21, p27, and Bax. Furthermore, the inhibition of USP39 expression decreased the phosphorylation of extracellular signal-regulated kinase (ERK)1/2, indicating that ERK signaling pathways might be involved in the regulation of melanoma cell proliferation by USP39. Our findings suggest that USP39 may play crucial roles in the development and pathogenesis of melanoma, and it may serve as a potential therapeutic target for melanoma.

Climacostol reduces tumour progression in a mouse model of melanoma via the p53-dependent intrinsic apoptotic programme

Climacostol, a compound produced by the ciliated protozoan Climacostomum virens, displayed cytotoxic properties in vitro. This study demonstrates that it has anti-tumour potential. Climacostol caused a reduction of viability/proliferation of B16-F10 mouse melanoma cells, a rapidly occurring DNA damage, and induced the intrinsic apoptotic pathway characterised by the dissipation of the mitochondrial membrane potential, the translocation of Bax to the mitochondria, the release of Cytochrome c from the mitochondria, and the activation of Caspase 9-dependent cleavage of Caspase 3. The apoptotic mechanism of climacostol was found to rely on the up-regulation of p53 and its targets Noxa and Puma. In vivo analysis of B16-F10 allografts revealed a persistent inhibition of tumour growth rate when melanomas were treated with intra-tumoural injections of climacostol. In addition, it significantly improved the survival of transplanted mice, decreased tumour weight, induced a remarkable reduction of viable cells inside the tumour, activated apoptosis and up-regulated the p53 signalling network. Importantly, climacostol toxicity was more selective against tumour than non-tumour cells. The anti-tumour properties of climacostol and the molecular events associated with its action indicate that it is a powerful agent that may be considered for the design of pro-apoptotic drugs for melanoma therapy.

Meta-Analysis of the Safety and Efficacy of Interferon Combined With Dacarbazine Versus Dacarbazine Alone in Cutaneous Malignant Melanoma

The aim of this study was to compare the efficacy and safety of interferon (IFN) combined with dacarbazine (DTIC) (experimental group) versus DTIC alone (control group) in cutaneous malignant melanoma. After searching all available databases, eligible articles were identified and subjected to quality assessment. Meta-analysis was performed using RevMan 5.3; combined relative risk (RR) and 95% confidence intervals (95% CIs) were calculated for survival rates, response rates, and adverse events. Eight randomized controlled trials published between 1990 and 2014 involving 795 patients were included in the meta-analysis. Compared with DTIC alone, IFN combined with DTIC significantly increased the overall response rate (RR = 1.59, 95% CI 1.21-2.08, P = 0.0008),the complete response rate (RR = 3.30, 95% CI 1.89-5.76, P < 0.0001), 2-year survival (RR = 1.59, 95% CI 0.99-2.54, P = 0.050) grade ≥3 hematologic toxicity (RR = 2.30, 95% CI 1.32-4.02, P = 0.003), neurotoxicity (RR = 18.15, 95% CI 5.34-61.74, P < 0.00001), and flu-like symptoms (RR = 6.31, 95% CI 1.95-20.39, P = 0.002). The partial response rate, grade ≥3 nausea and vomiting, treatment-related, and 1- and 3-year survival were not significantly different between IFN combined with DTIC and DTIC alone. IFN combined with DTIC may moderately improve the complete response rate, but increases the incidence of adverse events and has no significant effect on 1- and 3-year survival in cutaneous malignant melanoma.

Recent development of biotin conjugation in biological imaging, sensing, and target delivery

Despite encouraging results from preliminary studies of anticancer therapies, the lack of tumor specificity remains an important issue in the modern pharmaceutical industry. New findings indicate that biotin or biotin-conjugates could be favorably assimilated by tumor cells that over-express biotin-selective transporters. Furthermore, biotin can form stable complexes with avidin and its bacterial counterpart streptavidin. The strong bridging between avidin and biotin moieties on other molecules is a proven adaptable tool with broad biological applications. Under these circumstances, a biotin moiety is certainly an attractive choice for live-cell imaging, biosensing, and target delivery.

Cutaneous adverse events (AEs) of anti-programmed cell death (PD)-1 therapy in patients with metastatic melanoma: A single-institution cohort

BACKGROUND

Anti-programmed cell death (PD)-1 therapy is emerging as the backbone of new standard of care immunotherapy for metastatic melanoma. Immune-related cutaneous events are observed in these patients.

OBJECTIVE

We sought to describe cutaneous adverse events observed in patients with metastatic melanoma on anti-PD-1 therapy.

METHODS

We reviewed the clinical and histologic information of all patients treated with single-agent anti-PD-1 therapy for metastatic melanoma at Westmead Hospital, Sydney, Australia, from May 2012 to February 2015.

RESULTS

Of the 82 patients included in the study, 34 had dermatology assessments. Forty (49%) developed a form of anti-PD-1-associated cutaneous adverse events. In all, 17% developed lichenoid reactions and eczema, and 15% developed vitiligo. An estimated 25% of patients were expected to develop their first lichenoid reactions within 8.3 months, and eczema and vitiligo within 10.3 months of therapy. These adverse events tend to appear together in patients on anti-PD-1 therapy.

LIMITATIONS

The study was from a single center and clinical information was reviewed retrospectively in patients not referred to dermatology.

CONCLUSION

Anti-PD-1 therapy is associated with the development of immune-related cutaneous events. Lichenoid reactions, eczema, and vitiligo are the 3 most prevalent lesions observed in our population. There is a tendency for lichenoid reactions and eczema to occur with vitiligo.

Prognostic significance of forkhead box M1 (FoxM1) expression and antitumour effect of FoxM1 inhibition in melanoma

AIMS

Forkhead box M1 (FoxM1) is a transcription factor that regulates cell-cycle progression and tumour progression, but limited information is available regarding its clinical significance in melanoma. The aim of this study was to investigate the potency of FoxM1 as a therapeutic target in melanoma.

METHODS AND RESULTS

We investigated 60 melanoma clinical samples and a melanoma WM266-4 cell line using immunohistochemical staining and molecular biological approaches. Patients with a FoxM1-overexpressing melanoma had significantly shorter survival [both for melanoma-specific survival (MSS) and disease-free survival (DFS)] than the other patients (P < 0.001, respectively). The FoxM1 overexpression was also an adverse prognostic factor for both MSS and DFS on the Cox multivariate analyses [hazard ratio (HR): 3.96, 95% confidence interval (CI): 1.12-14.27, P = 0.032; HR: 3.21, 95% CI: 1.08-9.67, P = 0.037, respectively). FoxM1 inhibition using siRNA and an inhibitor (thiostrepton) each suppressed the cell proliferation of the melanoma cell line. Furthermore, FoxM1 inhibition improved chemosensitivity to dacarbazine, whereas it reduced cell migration and invasion. These results suggest that FoxM1 plays important roles in tumour progression and the chemoresistance of melanoma.

CONCLUSION

We have shown the prognostic impact of FoxM1 on melanoma patients. FoxM1 inhibition may be a potential therapeutic option for advanced melanoma.

MEK inhibitors and their potential in the treatment of advanced melanoma: the advantages of combination therapy

The treatment of melanoma has improved markedly over the last several years with the advent of more targeted therapies. Unfortunately, complex compensation mechanisms, such as those of the mitogen-activated protein kinase (MAPK) pathway, have limited the clinical benefit of these treatments. Recently, a better understanding of melanoma resistance mechanisms has given way to intelligently designed multidrug regimes. Herein, we review the extensive pathways of BRAF inhibitor (vemurafenib and dabrafenib) resistance. We also review the advantages of dual therapy, including the addition of an MEK inhibitor (cobimetinib or trametinib), which has proven to increase progression-free survival when compared to BRAF inhibitor monotherapy. Finally, this review touches on future treatment strategies that are being developed for advanced melanoma, including the possibility of triple therapy with immune checkpoint inhibitors and the work on optimizing sequential therapy.

Fibrin gels loaded with cisplatin and cisplatin-hyaluronate complexes tested in a subcutaneous human melanoma model

Fibrin gels are attractive biomaterials for local delivery of a variety of agents, from drugs to proteins. Similarly, polymer-anticancer-drug conjugates and nanoparticles are emerging as potential candidates for cancer treatment. Combining these different approaches, we have studied the efficacy of fibrin gels loaded with cisplatin (DDP) and a complex of DDP with hyaluronate (DDP-HA) for tumor growth inhibition in a melanoma model. Loaded gels prepared at relatively high fibrinogen concentration (22 mg/ml) showed good in vitro antiproliferative activities, prolonged release of the anticancer drug, and a long persistence (10-15 days) in vivo when implanted subcutaneously (sc) in immunodeficient mice. Gels loaded with DDP or DDP-HA containing 1/3 or even 1/6 of their systemic dose (6 mg/kg) and positioned under the tumor mass in mice bearing a sc human SK-Mel-28 tumor showed an antitumor activity better than that of the original parent compound given intraperitoneally (ip). Moreover, in an additional experiment in vivo, fibrin gels loaded with N-trimethyl chitosan-based nanoparticles containing a DDP-HA complex were assayed, resulting in a further 8 % improvement of anticancer activity, with lesser adverse systemic toxic effects. Taken together, these results suggest that the combination of fibrin gels and drugs complexed with suitable macromolecules holds great promise for loco-regional anticancer therapy of melanoma and other surgically removable cancer types.

New Anti-Nodal Monoclonal Antibodies Targeting the Nodal Pre-Helix Loop Involved in Cripto-1 Binding

Nodal is a potent embryonic morphogen belonging to the TGF-β superfamily. Typically, it also binds to the ALK4/ActRIIB receptor complex in the presence of the co-receptor Cripto-1. Nodal expression is physiologically restricted to embryonic tissues and human embryonic stem cells, is absent in normal cells but re-emerges in several human cancers, including melanoma, breast, and colon cancer. Our aim was to obtain mAbs able to recognize Nodal on a major CBR (Cripto-Binding-Region) site and to block the Cripto-1-mediated signalling. To achieve this, antibodies were raised against hNodal(44-67) and mAbs generated by the hybridoma technology. We have selected one mAb, named 3D1, which strongly associates with full-length rhNodal (KD 1.4 nM) and recognizes the endogenous protein in a panel of human melanoma cell lines by western blot and FACS analyses. 3D1 inhibits the Nodal-Cripto-1 binding and blocks Smad2/3 phosphorylation. Data suggest that inhibition of the Nodal-Cripto-1 axis is a valid therapeutic approach against melanoma and 3D1 is a promising and interesting agent for blocking Nodal-Cripto mediated tumor development. These findings increase the interest for Nodal as both a diagnostic and prognostic marker and as a potential new target for therapeutic intervention.

Gastrointestinal cancers in the era of theranostics: Updates and future perspectives

Theranostics are one of the practical aspects of personalized medicine. This concept was designed to describe a material combining diagnosis, treatment and follow up of a disease. It evolved and included molecular targeting and nanotechnologies that incorporate both diagnosis and therapeutics. In this editorial, we are presenting briefly the concept and evolution of theranostics, highlighting many applications of theranostics in daily practice and discussing future perspectives and aspects of this model in gastro-intestincal cancers.