Long-Term Vemurafenib Exposure Induced Alterations of Cell Phenotypes in Melanoma: Increased Cell Migration and Its Association with EGFR Expression

Development and in-depth characterization of BRAFi-resistant melanoma cell lines in vitro and in vivo

Regardless of the clinical response and improved patient survival observed following treatment with BRAFi like Vemurafenib (Vem), rapid development of resistance still remains as a major obstacle in melanoma therapy. In this context, we developed and characterized two acquired Vem-resistant melanoma cell lines, A375V and SK-MEL-28V, and an intrinsically Vem-resistant cell line, RPMI-7951. Altered morphology and growth rate of the resistant cell lines displayed spindle-shaped cells with filopodia formation and enhanced proliferation rate as compared to parental cells. Further in vitro characterization in 2D models confirmed the emergence of a resistant phenotype in melanoma cells. To mimic the in vivo tumor microenvironment, spheroids were developed for both parental and resistant cell lines to recognize materialization of invadopodia structures demonstrating elevated invasiveness and proliferation of resistant cells-based spheroids, especially A375V. Importantly, we validated A375V cell line in vivo to prove its tumorigenicity and drug resistance in tumor xenograft model. Taken together, our established clinically relevant Vem-resistant tumor model could be beneficial to elucidate drug resistance mechanisms, screen and identify novel anticancer therapies to overcome BRAFi resistance in melanoma.

PSAT1 mediated EMT of colorectal cancer cells by regulating Pl3K/AKT signaling pathway

Background: The metastasis of colorectal cancer (CRC) is one of the significant barriers impeding its treated consequence and bring about high mortality, less surgical resection rate and poor prognosis of CRC patients. PSAT1 is an enzyme involved in serine biosynthesis. The studies showed that PSAT1 plays the part of a crucial character in the regulation of tumor metastasis. And Epithelial-Mesenchymal Transition (EMT) is a process of cell reprogramming in which epithelialcells obtain mesenchymal phenotypes. It is a crucial course in promoting cell metastasis and the progression of malignant tumors. The relationship between PSAT1 and EMT in colorectal cancer, as well as the underlying molecular mechanisms, remains enigmatic and warrants thorough exploration. These findings suggest that PSAT1 may serve as a promising therapeutic target for mitigating colorectal cancer metastasis and holds the potential to emerge as a valuable prognostic biomarker in forthcoming research endeavors. Materials and Methods: Utilizing TCGA dataset in conjunction with clinical CRC specimens, our initial focus was directed towards an in-depth examination of PSAT1 expression within CRC, specifically exploring its potential correlation with the adverse prognostic outcomes experienced by patients. Furthermore, we conducted a comprehensive investigation into the regulatory influence exerted by PSAT1 on CRC through the utilization of siRNA knockdown techniques. In the realm of in vitro experimentation, we meticulously evaluated the impact of PSAT1 on various facets of CRC progression, including cell migration, invasion, proliferation, and colony formation. In order to elucidate the intricate effects in question, we adopted a multifaceted methodology that encompassed a range of assays and analyses. These included wound healing assays, transwell assays, utilization of the Cell Counting Kit-8 (CCK-8) assay, and colony formation assays. By employing this diverse array of investigative techniques, we were able to achieve a comprehensive comprehension of the multifaceted role that PSAT1 plays in the pathogenesis of colorectal cancer. This multifarious analysis greatly contributed to our in-depth understanding of the complex mechanisms at play in colorectal cancer pathogenesis. Using WB and PCR experiments, we found that PSAT1 has a role in regulating EMT development in CRC.In terms of mechanism, we found that PSAT1 affected EMT by Regulating Pl3K/AKT Signaling Pathway. Results: Our investigation revealed a noteworthy down-regulation of PSAT1 expression in CRC specimens. Importantly, this down-regulation exhibited a significant positive correlation with the unfavorable prognosis of patients afflicted with CRC. Functionally, our study showcased that the siRNA-mediated knockdown of PSAT1 markedly enhanced various key aspects of CRC pathogenesis in an in vitro setting. Specifically, this included a substantial promotion of CRC cell migration, invasion, proliferation, and colony formation. Moreover, the silencing of PSAT1 also demonstrated a substantial promotion of the EMT process. Intriguingly, our research unveiled a hitherto unexplored mechanism underlying the regulatory role of PSAT1 in CRC and EMT. We have established, for the first time, that PSAT1 exerts its influence by modulating the activation of the PI3K/AKT Signaling Pathway. This mechanistic insight provides a valuable contribution to the understanding of the molecular underpinnings of CRC progression and EMT induction mediated by PSAT1. Conclusions: In unison, our research findings shed light on the previously uncharted and significant role of the PSAT1/PI3K/AKT axis in the initiation of the EMT process in CRC. Furthermore, our discoveries introduce a novel biomarker with potential implications for the clinical diagnosis and treatment of CRC.

Antibody dependent cellular cytotoxicity-inducing anti-EGFR antibodies as effective therapeutic option for cutaneous melanoma resistant to BRAF inhibitors

Introduction

About 50% of cutaneous melanoma (CM) patients present activating BRAF mutations that can be effectively targeted by BRAF inhibitors (BRAFi). However, 20% of CM patients exhibit intrinsic drug resistance to BRAFi, while most of the others develop adaptive resistance over time. The mechanisms involved in BRAFi resistance are disparate and globally seem to rewire the cellular signaling profile by up-regulating different receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR). RTKs inhibitors have not clearly demonstrated anti-tumor activity in BRAFi resistant models. To overcome this issue, we wondered whether the shared up-regulated RTK phenotype associated with BRAFi resistance could be exploited by using immune weapons as the antibody-dependent cell cytotoxicity (ADCC)-mediated effect of anti-RTKs antibodies, and kill tumor cells independently from the mechanistic roots.

Methods and results

By using an in vitro model of BRAFi resistance, we detected increased membrane expression of EGFR, both at mRNA and protein level in 4 out of 9 BRAFi-resistant (VR) CM cultures as compared to their parental sensitive cells. Increased EGFR phosphorylation and AKT activation were observed in the VR CM cultures. EGFR signaling appeared dispensable for maintaining resistance, since small molecule-, antibody- and CRISPR-targeting of EGFR did not restore sensitivity of VR cells to BRAFi. Importantly, immune-targeting of EGFR by the anti-EGFR antibody cetuximab efficiently and specifically killed EGFR-expressing VR CM cells, both in vitro and in humanized mouse models in vivo, triggering ADCC by healthy donors' and patients' peripheral blood cells.

Conclusion

Our data demonstrate the efficacy of immune targeting of RTKs expressed by CM relapsing on BRAFi, providing the proof-of-concept supporting the assessment of anti-RTK antibodies in combination therapies in this setting. This strategy might be expected to concomitantly trigger the crosstalk of adaptive immune response leading to a complementing T cell immune rejection of tumors.

Vemurafenib induces senescence in acute myeloid leukemia and myelodysplastic syndrome by activating the HIPPO signaling pathway: implications for potential targeted therapy

BACKGROUND

The outcome of Acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) remain dismal despite the development of treatment. Targeted therapy is gaining more and more attention in improving prognosis.

METHODS

Expression of BRAF was analyzed by RT-qPCR in AML and MDS patients. Cells viability treated by drugs was measured by CCK-8 assay. Network pharmacology and RNA-sequence were used to analyze the mechanism of drugs and verified in vitro and xenograft tumor model.

RESULTS

Here we showed that BRAF was overexpressed in AML and MDS patients, and correlated with poor prognosis. The BRAF inhibitor-Vemurafenib (VEM) could significantly induce senescence, proliferation inhibition and apoptosis in AML cells, which can be enhanced by Bortezomib (BOR). This inhibitory effect was also verified in CD34 + cells derived from AML patients. Mechanistically, we showed that VEM combined with BOR could turn on HIPPO signaling pathway, thereby inducing cellular senescence in AML cells and xenograft mouse.

CONCLUSIONS

Taken together, our findings demonstrate a significant upregulation of BRAF expression in AML and MDS patients, which is associated with unfavorable clinical outcomes. We also discovered that the BRAF inhibitor Vemurafenib induces cellular senescence through activation of the HIPPO signaling pathway. Analysis of BRAF expression holds promise as a prognostic indicator and potential therapeutic target for individuals with AML and MDS.

Cardamonin suppressed the migration, invasion, epithelial mesenchymal transition (EMT) and lung metastasis of colorectal cancer cells by down-regulating ADRB2 expression

CONTEXT

Cardamonin (CDN) can suppress cell growth in colorectal cancer (CRC), a common digestive malignancy.

OBJECTIVE

We explored the effect and mechanism of CDN on metastatic CRC.

MATERIALS AND METHODS

Two cell lines (HT29 and HCT116) were initially treated with CDN at different concentrations (5, 10 and 20 μmol/L) or 50 μmol/L propranolol (positive control) for 24 or 48 h. Then, the two cell lines were separately transfected with siADRB2 and ADRB2 overexpression plasmids, and further treated with 10 μmol/L CDN for 24 h. The cell viability, migration and invasion were determined by cell counting kit-8 (CCK-8), wound healing and transwell assays, respectively. The levels of ADRB2, matrix metalloprotease (MMP)-2, MMP-9, E-cadherin and N-cadherin were measured by Western blotting or/and RT-qPCR. A CRC metastasis model was established to evaluate the antimetastatic potential of CDN (25 mg/kg).

RESULTS

ADRB2 (3.2-fold change; p < 0.001) was highly expressed in CRC tissues. CDN at 10 μmol/L suppressed viability (69% and 70%), migration (33% and 66%), invasion (43% and 72%) and ADRB2 expression (2.2- and 2.84-fold change) in HT29 and HCT116 cells (p < 0.001). CDN at 10 μmol/L inhibited MMP-2, MMP-9 and N-cadherin expression but promoted E-cadherin expression in CRC cells (p < 0.001). Importantly, the effect of CDN on CRC cells was impaired by ADRB2 overexpression, but further enhanced by ADRB2 down-regulation (p < 0.01). Additionally, ADRB2 overexpression reversed the inhibitory effect of CDN on metastatic lung nodules (p < 0.05). Discussion and conclusions: CDN is a potential candidate for the treatment of metastatic CRC in clinical practice.

Characterization of Vemurafenib-Resistant Melanoma Cell Lines Reveals Novel Hallmarks of Targeted Therapy Resistance

Regardless of the significant improvements in treatment of melanoma, the majority of patients develop resistance whose mechanisms are still not completely understood. Hence, we generated and characterized two melanoma-derived cell lines, primary WM793B and metastatic A375M, with acquired resistance to the RAF inhibitor vemurafenib. The morphology of the resistant primary WM793B melanoma cells showed EMT-like features and exhibited a hybrid phenotype with both epithelial and mesenchymal characteristics. Surprisingly, the vemurafenib-resistant melanoma cells showed a decreased migration ability but also displayed a tendency to collective migration. Signaling pathway analysis revealed the reactivation of MAPK and the activation of the PI3K/AKT pathway depending on the vemurafenib-resistant cell line. The acquired resistance to vemurafenib caused resistance to chemotherapy in primary WM793B melanoma cells. Furthermore, the cell-cycle analysis and altered levels of cell-cycle regulators revealed that resistant cells likely transiently enter into cell cycle arrest at the G0/G1 phase and gain slow-cycling cell features. A decreased level of NME1 and NME2 metastasis suppressor proteins were found in WM793B-resistant primary melanoma, which is possibly the result of vemurafenib-acquired resistance and is one of the causes of increased PI3K/AKT signaling. Further studies are needed to reveal the vemurafenib-dependent negative regulators of NME proteins, their role in PI3K/AKT signaling, and their influence on vemurafenib-resistant melanoma cell characteristics.

Targeting EGFR in melanoma - The sea of possibilities to overcome drug resistance

Melanoma is considered one of the most aggressive skin cancers. It spreads and metastasizes quickly and is intrinsically resistant to most conventional chemotherapeutics, thereby presenting a challenge to researchers and clinicians searching for effective therapeutic strategies to treat patients with melanoma. The use of inhibitors of mutated serine/threonine-protein kinase B-RAF (BRAF), e.g., vemurafenib and dabrafenib, has revolutionized melanoma chemotherapy. Unfortunately, the response to these drugs lasts a limited time due to the development of acquired resistance. One of the proteins responsible for this process is epidermal growth factor receptor (EGFR). In this review, we summarize the role of EGFR signaling in the multidrug resistance of melanomas and discuss possible applications of EGFR inhibitors to overcome the development of drug resistance in melanoma cells during therapy.

Potential Biomarkers of Skin Melanoma Resistance to Targeted Therapy—Present State and Perspectives

Simple Summary

Around 5–10% of advanced melanoma patients progress early on anti-BRAF targeted therapy and 20–30% respond only with the stabilization of the disease. Presumably, these patients could benefit more from first-line immunotherapy. Resistance to BRAF/MEK inhibitors is generated by genetic and non-genetic factors inherent to a tumor or acquired during therapy. Some of them are well documented as a cause of treatment failure. They are potential predictive markers that could improve patients’ selection for both standard and also alternative therapy as some of them have therapeutic potential. Here, a summary of the most promising predictive and therapeutic targets is presented. This up-to-date knowledge may be useful for further study on implementing more accurate genetic/molecular tests in melanoma treatment.

Abstract

Melanoma is the most aggressive skin cancer, the number of which is increasing worldwide every year. It is completely curable in its early stage and fatal when spread to distant organs. In addition to new therapeutic strategies, biomarkers are an important element in the successful fight against this cancer. At present, biomarkers are mainly used in diagnostics. Some biological indicators also allow the estimation of the patient’s prognosis. Still, predictive markers are underrepresented in clinics. Currently, the only such indicator is the presence of the V600E mutation in the BRAF gene in cancer cells, which qualifies the patient for therapy with inhibitors of the MAPK pathway. The identification of response markers is particularly important given primary and acquired resistance to targeted therapies. Reliable predictive tests would enable the selection of patients who would have the best chance of benefiting from treatment. Here, up-to-date knowledge about the most promising genetic and non-genetic resistance-related factors is described. These are alterations in MAPK, PI3K/AKT, and RB signaling pathways, e.g., due to mutations in NRAS, RAC1, MAP2K1, MAP2K2, and NF1, but also other changes activating these pathways, such as the overexpression of HGF or EGFR. Most of them are also potential therapeutic targets and this issue is also addressed here.

Molecular Alterations Associated with Acquired Drug Resistance during Combined Treatment with Encorafenib and Binimetinib in Melanoma Cell Lines

Combination treatment using BRAF/MEK inhibitors is a promising therapy for patients with advanced BRAF^V600E/K mutant melanoma. However, acquired resistance largely limits the clinical efficacy of this drug combination. Identifying resistance mechanisms is essential to reach long-term, durable responses. During this study, we developed six melanoma cell lines with acquired resistance for BRAFi/MEKi treatment and defined the molecular alterations associated with drug resistance. We observed that the invasion of three resistant cell lines increased significantly compared to the sensitive cells. RNA-sequencing analysis revealed differentially expressed genes that were functionally linked to a variety of biological functions including epithelial-mesenchymal transition, the ROS pathway, and KRAS-signalling. Using proteome profiler array, several differentially expressed proteins were detected, which clustered into a unique pattern. Galectin showed increased expression in four resistant cell lines, being the highest in the WM1617^E+BRes cells. We also observed that the resistant cells behaved differently after the withdrawal of the inhibitors, five were not drug addicted at all and did not exhibit significantly increased lethality; however, the viability of one resistant cell line (WM1617^E+BRes) decreased significantly. We have selected three resistant cell lines to investigate the protein expression changes after drug withdrawal. The expression patterns of CapG, Enolase 2, and osteopontin were similar in the resistant cells after ten days of "drug holiday", but the Snail protein was only expressed in the WM1617^E+BRes cells, which showed a drug-dependent phenotype, and this might be associated with drug addiction. Our results highlight that melanoma cells use several types of resistance mechanisms involving the altered expression of different proteins to bypass drug treatment.

Vemurafenib Drives Epithelial-to-Mesenchymal Transition Gene Expression in BRAF Inhibitor‒Resistant BRAFV600E/NRASQ61K Melanoma Enhancing Tumor Growth and Metastasis in a Bioluminescent Murine Model

BRAF inhibitor (BRAFi) resistance compromises long-term survivorship of patients with malignant melanoma, and mutant NRAS is a major mediator of BRAFi resistance. In this study, employing phenotypic and transcriptomic analysis of isogenic melanoma cells that differ only by NRAS mutational status (BRAFi-sensitive A375-BRAF^V600E/NRAS^Q61 vs. BRAFi-resistant A375-BRAF^V600E/NRAS^Q61K), we show that BRAFi (vemurafenib) treatment selectively targets BRAF^V600E/NRAS^Q61K cells upregulating epithelial-to-mesenchymal transition (EMT) gene expression, paradoxically promoting invasiveness and metastasis in vitro and in vivo. First, NanoString nCounter transcriptomic analysis identified the upregulation of specific gene expression networks (EMT and EMT to metastasis) as a function of NRAS^Q61K status. Strikingly, BRAFi treatment further exacerbated the upregulation of genes promoting EMT in BRAF^V600E/NRAS^Q61K cells (with opposing downregulation of EMT-driver genes in the BRAF^V600E/NRAS^Q61 genotype) as detected by EMT-focused RT² Profiler qPCR array analysis. In BRAF^V600E/NRAS^Q61K cells, BRAFi treatment enhanced proliferation and invasiveness, together with activation of phosphorylated protein kinase B (Ser473), with opposing phenotypic effects observable in BRAF^V600E/NRAS^Q61 cells displaying downregulation of phosphorylated protein kinase B and phosphorylated extracellular signal-regulated kinase 1/2. In a SCID mouse bioluminescent melanoma metastasis model, BRAFi treatment enhanced lung tumor burden imposed by BRAF^V600E/NRAS^Q61K cells while blocking BRAF^V600E/NRAS^Q61 metastasis. These preclinical data document the BRAFi-driven enhancement of tumorigenesis and metastasis in BRAFi-resistant human BRAF^V600E/NRAS^Q61K melanoma, a finding with potential clinical implications for patients with NRAS-driven BRAFi-resistant tumors receiving BRAFi treatment.

BRAF inhibitor resistance of melanoma cells triggers increased susceptibility to natural killer cell-mediated lysis

Background

Targeted therapies and immunotherapies are first-line treatments for patients with advanced melanoma. Serine–threonine protein kinase B-RAF (BRAF) and mitogen-activated protein kinase (MEK) inhibition leads to a 70% response rate in patients with advanced melanoma with a BRAF^V600E/K mutation. However, acquired resistance occurs in the majority of patients, leading to relapse. Immunotherapies that activate immune cytotoxic effectors induce long-lasting responses in 30% of patients. In that context, combination of targeted therapies with immunotherapy (IT) is a promising approach. We considered boosting natural killer (NK) cell tumor immunosurveillance, as melanoma cells express stress-induced molecules and activate NK cell lysis.

Methods

Here we have generated vemurafenib (a BRAF inihibitor)-resistant (R) cells from BRAF^V600E SK28 and M14-sensitive (S) melanoma cell lines and investigated how resistance interferes with immunogenicity to NK cells. We determined the levels of several soluble molecules including NK ligands in 61 melanoma patients at baseline and 6 months M post-treatment with targeted therapies or immunotherapies.

Results

Vemurafenib resistance involved activation of p-AKT in SK28R and of p-MEK/p-ERK in M14R cells and was accompanied by modulation of NK ligands. Compared with S cells, SK28R displayed an increased expression of natural killer group 2 D (NKG2D) receptor ligands (major histocompatibility complex class (MHC) I chain-related protein A (MICA) and UL16-binding protein 2 (ULBP2)) whereas M14R exhibited decreased ULBP2. SK28R and M14R cells induced higher NK degranulation and interferon gamma secretion and were more efficiently lysed by donor and patient NK cells. SK28R showed increased tumor necrosis factor-related apoptosis-inducing ligand receptor II (TRAIL-RII) expression and TRAIL-induced apoptosis, and TRAIL-induced apoptosis of M14R was decreased. Combined BRAF/MEK inhibitors abrogated the growth of SK28S, M14S, and M14R cells, while growth of SK28R was maintained. BRAF/MEK inhibition attenuated NK activity but R cell lines activated polyfunctional NK cells and were lysed with high efficiency. We investigated the relationship of soluble NK ligands and response to treatment in a series of melanoma patients. Soluble NKG2D ligands known to regulate the receptor function have been associated to cancer progression. Serum analysis of patients treated with target therapies or IT indicates that soluble forms of NK ligands (MICA, B7H6, programmed cell death ligand 1, and carcinoembryonic antigen cell adhesion molecule 1) may correlate with clinical response.

Conclusion

These results support strategies combining targeted therapies and NK-based immunotherapies.

Neratinib kills B-RAF V600E melanoma via ROS-dependent autophagosome formation and death receptor signaling

Melanoma cells expressing mutant B-RAF V600E are susceptible to treatment with the combination of a B-RAF inhibitor and a MEK1/2 inhibitor. We investigated the impact of the ERBB family and MAP4K inhibitor neratinib on the biology of PDX isolates of cutaneous melanoma expressing B-RAF V600E. Neratinib synergized with HDAC inhibitors to kill melanoma cells at their physiologic concentrations. Neratinib activated ATM, AMPK, ULK1, and PERK and inactivated mTORC1/2, ERK1/2, eIF2 alpha, and STAT3. Neratinib increased expression of Beclin1, ATG5, CD95, and FAS-L and decreased levels of multiple toxic BH3 domain proteins, MCL1, BCL-XL, FLIP-s, and ERBB1/2/4. ATG13 S318 phosphorylation and autophagosome formation was dependent upon ATM, and activation of ATM was dependent on reactive oxygen species. Reduced expression of ERBB1/2/4 required autophagosome formation and reduced MCL1/BCL-XL levels required eIF2 alpha phosphorylation. Maximal levels of eIF2 alpha phosphorylation required signaling by ATM-AMPK and autophagosome formation. Knock down of eIF2 alpha, CD95, FAS-L, Beclin1, and ATG5 or over-expression of FLIP-s significantly reduced killing. Combined knock down of Beclin1 and CD95 abolished cell death. Our data demonstrate that PDX melanoma cells expressing B-RAF V600E are susceptible to being killed by neratinib and more so when combined with HDACi.

How Neural Crest Transcription Factors Contribute to Melanoma Heterogeneity, Cellular Plasticity, and Treatment Resistance

Cutaneous melanoma represents one of the deadliest types of skin cancer. The prognosis strongly depends on the disease stage, thus early detection is crucial. New therapies, including BRAF and MEK inhibitors and immunotherapies, have significantly improved the survival of patients in the last decade. However, intrinsic and acquired resistance is still a challenge. In this review, we discuss two major aspects that contribute to the aggressiveness of melanoma, namely, the embryonic origin of melanocytes and melanoma cells and cellular plasticity. First, we summarize the physiological function of epidermal melanocytes and their development from precursor cells that originate from the neural crest (NC). Next, we discuss the concepts of intratumoral heterogeneity, cellular plasticity, and phenotype switching that enable melanoma to adapt to changes in the tumor microenvironment and promote disease progression and drug resistance. Finally, we further dissect the connection of these two aspects by focusing on the transcriptional regulators MSX1, MITF, SOX10, PAX3, and FOXD3. These factors play a key role in NC initiation, NC cell migration, and melanocyte formation, and we discuss how they contribute to cellular plasticity and drug resistance in melanoma.

YM155 inhibits retinal pigment epithelium cell survival through EGFR/MAPK signaling pathway

AIM

To investigate YM155's effect on retinal pigment epithelium (RPE) cells' viability and the potential regulatory mechanisms.

METHODS

Human immortalized RPE cell lines (ARPE-19 cell line) were processed with YM155 and epidermal growth factor (EGF). ARPE-19 cell viability was detected by methyl thiazolyl tetrazolium assay, and apoptosis was tested by flow cytometry assay. ARPE-19 cell proliferation was assessed with bromodeoxyuridine tagged incorporation assay, and migration ability was evaluated via a wound-healing assay. Epidermal growth factor receptor (EGFR)/MAPK pathway proteins were tested via immunoblotting. EGFR localization was examined by immunofluorescence assay.

RESULTS

YM155 suppressed ARPE-19 cells' viability in a time and concentration-dependent manner. A high dose of YM155 caused a small amount of ARPE-19 cell death. YM155 significantly diminished the ARPE-19 cells' proliferative and migrative capacity. YM155 down-regulated total EGFR and phosphorylated external signal-regulated protein kinase (ERK), and it up-regulated the phosphorylation of P38MAPK and c-Jun N-terminal kinase (JNK). YM155 induced endocytosis of EGFR in ARPE-19 cell. YM155 also attenuated EGF-induced ARPE-19 cells' proliferative and migrative capacity. Moreover, YM155 significantly decreased the expression of phosphorylated EGFR and ERK after treated by EGF.

CONCLUSION

YM155 inhibits RPE cell survival, the cell proliferative and migrative capacity, and it effectuates a small amount of cell death through the EGFR/MAPK signaling pathway. YM155 might, therefore, be an agent to prevent and treat abnormal RPE cell survival in proliferative vitreoretinopathy.

GZ17-6.02 Interacts With [MEK1/2 and B-RAF Inhibitors] to Kill Melanoma Cells

We defined the lethal interaction between the novel therapeutic GZ17-6.02 and the standard of care combination of the MEK1/2 inhibitor trametinib and the B-RAF inhibitor dabrafenib in PDX isolates of cutaneous melanoma expressing a mutant B-RAF V600E protein. GZ17-6.02 interacted with trametinib/dabrafenib in an additive fashion to kill melanoma cells. Regardless of prior vemurafenib resistance, the drugs when combined interacted to prolong ATM S1981/AMPK T172 and eIF2α S51 phosphorylation and prolong the reduced phosphorylation of JAK2 Y1007, STAT3 Y705 and STAT5 Y694. In vemurafenib-resistant cells GZ17-6.02 caused a prolonged reduction in mTORC1 S2448, mTORC2 S2481 and ULK1 S757 phosphorylation; regardless of vemurafenib resistance, GZ17-6.02 caused a prolonged elevation in CD95 and FAS-L expression. Knock down of eIF2α, Beclin1, ATG5, ATM, AMPKα, CD95 or FADD significantly reduced the ability of GZ17-6.02 to kill as a single agent or when combined with the kinase inhibitors. Expression of activated mTOR, activated STAT3, activated MEK1 or activated AKT significantly reduced the ability of GZ17-6.02 to kill as a single agent or when combined with kinase inhibitors; protective effects that were significantly less pronounced in cells treated with trametinib/dabrafenib. Regardless of vemurafenib resistance, the drugs alone or in combination all reduced the expression of PD-L1 and increased the levels of MHCA, which was linked to degradation of multiple HDAC proteins. Our findings support the use of GZ17-6.02 in combination with trametinib/dabrafenib in the treatment of melanomas expressing mutant B-RAF V600E proteins.

Juniperus indica Bertol. extract synergized with cisplatin against melanoma cells via the suppression of AKT/mTOR and MAPK signaling and induction of cell apoptosis

Juniperus indica Bertol. is an herbal plant that belongs to the genus Juniperus, which is commonly used in traditional medicine to refresh the mind and for diuretic use. However, few studies have reported the function of J. indica Bertol. Hence, this study aimed to investigate the anti-tumor and synergistic potential of J. indica Bertol. extract (JIB extract) for melanoma cells. Our results indicated the anti-melanoma activity of JIB extract. JIB extract induced cell cycle arrest at the G₀/G₁ phase and decreased cyclin and cdk protein expressions. In addition, AKT/mTOR signaling and MAPK signaling were inhibited by JIB extract to suppress melanoma cell growth and proliferation. Additionally, JIB extract induced B16/F10 cell apoptosis via the caspase cascade. According to the JIB extract's anti-melanoma capacity, to assess the synergistic effects of cisplatin and JIB extract. The results demonstrated that JIB extract combined with cisplatin enhanced the inhibition of cell growth, proliferation, and survival through the obstruction of cell cycle progression and AKT/mTOR and MAPK signaling as well as the induction of cell apoptosis. Collectively, our results indicate that JIB extract showed anti-tumor effects and synergized with cisplatin against B16/F10 cells, indicating the possibility of JIB extract to be developed as adjuvant therapy for melanoma.

Mechanisms of Acquired BRAF Inhibitor Resistance in Melanoma: A Systematic Review

This systematic review investigated the literature on acquired v-raf murine sarcoma viral oncogene homolog B1 (BRAF) inhibitor resistance in patients with melanoma. We searched MEDLINE for articles on BRAF inhibitor resistance in patients with melanoma published since January 2010 in the following areas: (1) genetic basis of resistance; (2) epigenetic and transcriptomic mechanisms; (3) influence of the immune system on resistance development; and (4) combination therapy to overcome resistance. Common resistance mutations in melanoma are BRAF splice variants, BRAF amplification, neuroblastoma RAS viral oncogene homolog (NRAS) mutations and mitogen-activated protein kinase kinase 1/2 (MEK1/2) mutations. Genetic and epigenetic changes reactivate previously blocked mitogen-activated protein kinase (MAPK) pathways, activate alternative signaling pathways, and cause epithelial-to-mesenchymal transition. Once BRAF inhibitor resistance develops, the tumor microenvironment reverts to a low immunogenic state secondary to the induction of programmed cell death ligand-1. Combining a BRAF inhibitor with a MEK inhibitor delays resistance development and increases duration of response. Multiple other combinations based on known mechanisms of resistance are being investigated. BRAF inhibitor-resistant cells develop a range of 'escape routes', so multiple different treatment targets will probably be required to overcome resistance. In the future, it may be possible to personalize combination therapy towards the specific resistance pathway in individual patients.

Gene Expression Signature of BRAF Inhibitor Resistant Melanoma Spheroids

In vitro cell cultures are frequently used to define the molecular background of drug resistance. The majority of currently available data have been obtained from 2D in vitro cultures, however, 3D cell culture systems (spheroids) are more likely to behave similarly to in vivo conditions. Our major aim was to compare the gene expression signature of 2D and 3D cultured BRAFV600E mutant melanoma cell lines. We successfully developed BRAF-drug resistant cell lines from paired primary/metastatic melanoma cell lines in both 2D and 3D in vitro cultures. Using Affymetrix Human Gene 1.0 ST arrays, we determined the gene expression pattern of all cell lines. Our analysis revealed 1049 genes (562 upregulated and 487 downregulated) that were differentially expressed between drug-sensitive cells grown under different cell cultures. Pathway analysis showed that the differently expressed genes were mainly associated with the cell cycle, p53, and other cancer-related pathways. The number of upregulated genes (72 genes) was remarkably fewer when comparing the resistant adherent cells to cells that grow in 3D, and were associated with cell adhesion molecules and IGF1R signalling. Only 1% of the upregulated and 5.6% of the downregulated genes were commonly altered between the sensitive and the resistant spheroids. Interestingly, we found several genes (BNIP3, RING1 and ABHD4) with inverse expression signature between sensitive and resistant spheroids, which are involved in anoikis resistance and cell cycle regulation. In summary, our study highlights gene expression alterations that might help to understand the development of acquired resistance in melanoma cells in tumour tissue.

Characterization of Melanoma Cell Lines Resistant to Vemurafenib and Evaluation of Their Responsiveness to EGFR- and MET-Inhibitor Treatment

Constitutively active mutated BRAF kinase occurs in more than 40% of patients suffering from melanoma. To block its activity, a specific inhibitor, vemurafenib, is applied as a therapy. Unfortunately, patients develop resistance to this drug rather quickly. Previously, we demonstrated that pairs of inhibitors directed against EGFR (epidermal growth factor receptor) and MET (hepatocyte growth factor receptor) trigger a synergistic cytotoxic effect in human melanoma cells, and decrease their invasive abilities. In this study, we aimed to generate and characterize melanoma cells resistant to vemurafenib treatment, and then to evaluate the effectiveness of a previously developed therapy in this model. We showed that melanoma cells resistant to the BRAF inhibitor are characterized by a lower proliferation rate and they acquire a spindle-like shape. Using Western Blot, we also noticed increased levels of EGFR, MET, and selected markers of cancer stem cells in generated cell lines. Resistant cells also exhibited increased invasive abilities and elevated proteolytic activity, observed using scratch wound assays and gelatin zymography. Moreover, combination therapy reduced their viability, as measured with a colorimetric cytotoxicity test, and decreased invasiveness. The obtained results validate the application of combination therapy directed against EGFR and MET in melanoma cells resistant to treatment with inhibitors of mutated BRAF.