Diverse Mechanisms of BRAF Inhibitor Resistance in Melanoma Identified in Clinical and Preclinical Studies

The identification of functional regions of MEK1 using CRISPR tiling screens

CRISPR tiling screen is a powerful tool to identify protein regions relevant to its biological function. Understanding the functional relevance of the regions of target protein is of great help for structure-based drug discovery. Studying the drug resistance mechanisms of small-molecule inhibitors is important for the development and clinical application of the compounds. Using MEK1 and MEK inhibitors as example here, we demonstrate the utility of CRISPR tiling to identify regions essential for cancer cell viability and regions where mutations are resistant to MEK inhibitors. We study the drug resistance mechanisms of the regions and discussed the potential, as well as limitations, of applying the technology to drug development. Our findings demonstrate the value and prompt the utilization of CRISPR tiling technology in structure-based drug discovery.

C-Terminal Hsp90 Inhibitors Overcome MEK and BRAF Inhibitor Resistance in Melanoma

Targeted therapies for melanoma MEK and BRAF inhibitors fail due to the development of chemoresistance. As Hsp90 inhibitors target client proteins of resistant pathways, we hypothesised that C-terminal Hsp90 inhibitors will target BRAF/MEK inhibitor resistant melanoma cells by overcoming the resistant pathways. Two melanoma cell lines, A375 and A375 MEK/BRAF inhibitor resistant (A375MEKi) were utilised. The inhibitory concentrations (IC50) of two C-terminal Hsp90 inhibitors, KU757 and KU758, were determined by CellTiter Glo. RNA sequencing was performed after treatment with KU757. Pathways targeted by differentially expressed genes were evaluated by David, IPA, GSEA, and by evaluating the cell cycle, apoptosis and oxidative phosphorylation. Expression levels of hub genes were evaluated using Xena and validated by RT-PCR. The survival analysis was performed using UALCAN. A375MEKi was not resistant to the C-terminal Hsp90 inhibitor with a KU757 IC50 of 0.59 μM versus 0.64 μM and a KU758 IC50 of 0.89 μM versus 0.93 μM in A375 versus A375MEKi, respectively. RNA sequencing analysis revealed KU757 upregulates cell cycle checkpoint regulation and apoptosis and downregulates genes involved in the peroxisome, AKT/PI3K/MTOR, EIF2, fatty acid metabolism and oxidative phosphorylation. These pathways were further validated through survival analysis that demonstrated potential survival benefit in patients with dysregulated NDUFA7, CDC20, CDC25C, CDK1, VDAC2, HEATR5a, COL4A4, FLT3LG, BMP2, PRKCH and ADMST9. Melanomas often develop concurrent resistance to BRAF and MEK inhibitors. C-terminal Hsp90 inhibition with KU757 appears to overcome these chemo-resistance pathways in vitro, downregulating metabolic pathways including oxidative phosphorylation and the cell cycle, warranting further in vivo translation. The novel C-terminal HSP90 inhibitor KU757 effectively targets primary and BRAF and MEK inhibitor-resistant melanoma cells equally by affecting oxidative phosphorylation and the cell cycle.

Second-generation BRAF inhibitor Encorafenib resistance is regulated by NCOA4-mediated iron trafficking in the drug-resistant malignant melanoma cells

The current study established the first in vitro Encorafenib resistance protocol in BRAF-mutated malignant melanoma (MM) cells and investigated the resistance-related mechanisms. After establishing Encorafenib-resistant A375-MM cells, resistant-related mechanisms were investigated using WST-1, Annexin V, cell cycle, morphological analysis, live-cell, Western blot, RNA-Seq, transmission electron microscopy-(TEM), oxidative stress and iron colorimetric assay. The most resistant group, called A375-R, was determined in the cells treated with a constant dose of 10 nM over 3 months. The viability, apoptosis, and G0/G1 arrest reflected the acquired chemoresistance. Autophagic Beclin and LC3 proteins, and AKT signaling increased in the A375-R. RNA-Seq results also exhibited altered epigenetic regulation of resistance; particularly ferritin family members, ion transport pathways. Then, increased NCOA4, FTH1, and iron levels detected in A375-R suggest that the iron metabolism-related mechanism, such as ferritinophagy, might be triggered, which was supported by TEM and oxidative stress analysis. Iron storage, transport, and ferritinophagy have the promising potential to be targeted for combining with BRAF-targeted therapy to reverse Encorafenib resistance in MM. Moreover, this is the first study evaluating in vitro Encorafenib resistance mechanisms, and we suggest that our findings contribute to improving new drug combinations targeting BRAF and iron metabolism in different MM cells.

Global trends and emerging insights in BRAF and MEK inhibitor resistance in melanoma: a bibliometric analysis

Objective

This study aims to perform a comprehensive bibliometric analysis of global research on BRAF and MEK inhibitor resistance in melanoma, identifying key research trends, influential contributors, and emerging themes from 2003 to 2024.

Methods

A systematic search was conducted in the Web of Science Core Collection (WoSCC) database to retrieve publications related to BRAF and MEK inhibitor resistance from 1 January 2003, to 1 September 2024. Bibliometric analyses, including publication trends, citation networks, and keyword co-occurrence patterns, were performed using VOSviewer and CiteSpace. Collaborative networks, co-cited references, and keyword burst analyses were mapped to uncover shifts in research focus and global cooperation.

Results

A total of 3,503 documents, including 2,781 research articles and 722 review papers, were analyzed, highlighting significant growth in this field. The United States, China, and Italy led in publication volume and citation impact, with Harvard University and the University of California System among the top contributing institutions. Research output showed three phases of growth, peaking in 2020. Keyword and co-citation analyses revealed a transition from early focus on BRAF mutations and MAPK pathway activation to recent emphasis on immunotherapy, combination therapies, and non-apoptotic cell death mechanisms like ferroptosis and pyroptosis. These trends reflect the evolving priorities and innovative approaches shaping the field of resistance to BRAF and MEK inhibitors in melanoma.

Conclusion

Research on BRAF and MEK inhibitor resistance has evolved significantly. This analysis provides a strategic framework for future investigations, guiding the development of innovative, multi-modal approaches to improve treatment outcomes for melanoma patients.

POU5F1B is responsible for the acquired resistance to dabrafenib in papillary thyroid cancer cells with the BRAF V600E mutation

BACKGROUND

Dabrafenib, an inhibitor of the B-Raf proto-oncogene (BRAF) V600E mutant, has become the major drug for targeted therapy of papillary thyroid cancer (PTC) with the BRAF V600E mutant; however, acquired resistance is inevitable.

OBJECTIVE

To identify key transcription factors (TFs) involved in dabrafenib resistance and identify targets to reverse dabrafenib resistance.

METHODS

Dabrafenib-resistant PTC cell lines BCPAP/DabR and K1/DabR were established, and phenotypic assays were performed to validate the malignant phenotype. RNA sequencing and bioinformatics analyses were used to identify differentially expressed genes (DEGs) and screen TFs involved in resistant phenotype-related pathways. The role of the key TF POU5F1B in dabrafenib resistance was further validated using gene gain-and-loss assays.

RESULTS

BCPAP/DabR and K1/DabR were resistant to dabrafenib, with a resistance index of 5-8. Resistant cells exhibited slower proliferation, strong migration, and spheroid-forming abilities. RNA sequencing screened 6233 DEGs in the resistant group, including 2687 protein-coding RNA (mRNA). Venn analysis indicated that three genes, E2F2, WNT4, and POU5F1B, were involved in resistant phenotype-related pathways and were included in the TF regulatory network. Four TFs of the three genes, POU5F1B, TBX4, FOXO4, and FOXP3, were validated, and POU5F1B showed the highest validated fold-change. Overexpression of POU5F1B in sensitive cells resulted in resistance to dabrafenib and induced a malignant phenotype, whereas silencing it sensitized the resistant cells and reversed the resistant phenotype.

CONCLUSION

This study successfully established two dabrafenib-resistant PTC cell lines, and POU5F1B could be a potential target for reversing dabrafenib resistance.

The development of drug resistance in metastatic tumours under chemotherapy: An evolutionary perspective

We present a mathematical model of the evolutionary dynamics of a metastatic tumour under chemotherapy, comprising non-local partial differential equations for the phenotype-structured cell populations in the primary tumour and its metastasis. These equations are coupled with a physiologically-based pharmacokinetic model of drug administration and distribution, implementing a realistic delivery schedule. The model is carefully calibrated from the literature, focusing on BRAF-mutated melanoma treated with Dabrafenib as a case study. By means of long-time asymptotic and global sensitivity analyses, as well as numerical simulations, we explore the impact of cell migration from the primary to the metastatic site, physiological aspects of the tumour tissues and drug dose on the development of chemoresistance and treatment efficacy. Our findings provide a possible explanation for empirical evidence indicating that chemotherapy may foster metastatic spread and that metastases may be less impacted by the chemotherapeutic agent.

Mutation-Specific CRISPR Targeting with SaCas9 and AsCas12a Restores Therapeutic Sensitivity in Treatment-Resistant Melanoma

Background: Melanoma remains one of the most challenging cancers to treat effectively with drug resistant remaining a constant concern, primarily with activating BRAF mutations. Mutations in the BRAF gene appear in approximately 50% of patients, 90% of which are V600E. Two frontline BRAF inhibitors (BRAFi), vemurafenib and dabrafenib, are frequently used to treat unresectable or metastatic BRAF V600E melanoma. Initial response rates are high, but soon thereafter, 70-80% of patients develop resistance to treatment within a year. A major mechanism of resistance is the generation of a secondary Q61K mutation in the NRAS gene. Methods: We have developed an approach in which a CRISPR-Cas complex can be designed to distinguish between mutant genes enabling resistance to standard care in tumor cells and normal genomes of healthy cells. For the first time, we demonstrated the utility of two CRISPR-directed mutation-specific editing approaches to restore BRAFi sensitivity in BRAFV600E/NRASQ61K resistant A375 cells. Results: We utilize an AsCas12a protospacer adjacent motif site created by the NRAS Q61K mutation and the Q61K mutation in the critical seed region of an SaCas9 sgRNA for Q61K-selective targeting. We show here that both approaches allow for effective NRAS targeting of only mutated-Q61K and after CRISPR-directed Q61K-targeting, previously resistant A375 cells are re-sensitized to BRAFi treatment. Conclusion: Our data support the feasibility of the development of CRISPR-Cas therapeutic approaches to the treatment of melanoma. Successful therapeutic CRISPR-directed gene editing would enable both specific and efficient editing of a mutation-specific targeting approach eliminate concern for on- and off-target damage to the genomes of healthy cells.

BRAF-Mutated Melanoma Cell Lines Develop Distinct Molecular Signatures After Prolonged Exposure to AZ628 or Dabrafenib: Potential Benefits of the Antiretroviral Treatments Cabotegravir or Doravirine on BRAF-Inhibitor-Resistant Cells

Melanoma is an aggressive cancer characterized by rapid growth, early metastasis, and poor prognosis, with resistance to current therapies being a significant issue. BRAF mutations drive uncontrolled cell division by activating the MAPK pathway. In this study, A375 and FO-1, BRAF-mutated melanoma cell lines, were treated for 4-5 months with RAF inhibitor dabrafenib or AZ628, leading to drug resistance over time. The resistant cells showed altered molecular signatures, with differences in cell cycle regulation and the propensity of cell death. Dabrafenib-resistant cells maintained high proliferative activity, while AZ628-resistant cells, especially A375 cells, exhibited slow-cycling, and a senescent-like phenotype with high susceptibility to ferroptosis, a form of cell death driven by iron. Antiretroviral drugs doravirine and cabotegravir, known for their effects on human endogenous retroviruses, were tested for their impact on these resistant melanoma cells. Both drugs reduced cell viability and colony formation in resistant cell lines. Doravirine was particularly effective in reactivating apoptosis and reducing cell growth in highly proliferative resistant cells by increasing tumor-suppressor proteins p16Ink4a and p27Kip1. These findings suggest that antiretroviral drugs can influence apoptosis and cell proliferation in RAF-inhibitor-resistant melanoma cells, offering potential therapeutic strategies for overcoming drug resistance.

Stromal reprogramming overcomes resistance to RAS-MAPK inhibition to improve pancreas cancer responses to cytotoxic and immune therapy

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy that is often resistant to therapy. An immune suppressive tumor microenvironment (TME) and oncogenic mutations in KRAS have both been implicated as drivers of resistance to therapy. Mitogen-activated protein kinase (MAPK) inhibition has not yet shown clinical efficacy, likely because of rapid acquisition of tumor-intrinsic resistance. However, the unique PDAC TME may also be a driver of resistance. We found that long-term focal adhesion kinase (FAK) inhibitor treatment led to hyperactivation of the RAS/MAPK pathway in PDAC cells in mouse models and tissues from patients with PDAC. Concomitant inhibition of both FAK (with VS-4718) and rapidly accelerated fibrosarcoma and MAPK kinase (RAF-MEK) (with avutometinib) induced tumor growth inhibition and increased survival across multiple PDAC mouse models. In the TME, cancer-associated fibroblasts (CAFs) impaired the down-regulation of MYC by RAF-MEK inhibition in PDAC cells, resulting in resistance. By contrast, FAK inhibition reprogramed CAFs to suppress the production of FGF1, which can drive resistance to RAF-MEK inhibition. The addition of chemotherapy to combined FAK and RAF-MEK inhibition led to tumor regression, a decrease in liver metastasis, and improved survival in KRAS-driven PDAC mouse models. Combination of FAK and RAF-MEK inhibition alone improved antitumor immunity and priming of T cell responses in response to chemotherapy. These findings provided the rationale for an ongoing clinical trial evaluating the efficacy of avutometinib and defactinib in combination with gemcitabine and nab-paclitaxel in patients with PDAC and may suggest further paths for combined stromal and tumor-targeting therapies.

ARID1A-Deficient Tumors Acquire Immunogenic Neoantigens during the Development of Resistance to Targeted Therapy

Neoantigen-based immunotherapy is an attractive potential treatment for previously intractable tumors. To effectively broaden the application of this approach, stringent biomarkers are crucial to identify responsive patients. ARID1A, a frequently mutated subunit of SWI/SNF chromatin remodeling complex, has been reported to determine tumor immunogenicity in some cohorts; however, mutations and deletions of ARID1A are not always linked to clinical responses to immunotherapy. In this study, we investigated immunotherapeutic responses based on ARID1A status in targeted therapy-resistant cancers. Mouse and human BRAFV600E melanomas with or without ARID1A expression were transformed into resistant to vemurafenib, an FDA-approved specific BRAFV600E inhibitor. Anti-PD-1 antibody treatment enhanced antitumor immune responses in vemurafenib-resistant ARID1A-deficient tumors but not in ARID1A-intact tumors or vemurafenib-sensitive ARID1A-deficient tumors. Neoantigens derived from accumulated somatic mutations during vemurafenib resistance were highly expressed in ARID1A-deficient tumors and promoted tumor immunogenicity. Furthermore, the newly generated neoantigens could be utilized as immunotherapeutic targets by vaccines. Finally, targeted therapy resistance-specific neoantigen in experimental human melanoma cells lacking ARID1A were validated to elicit T-cell receptor responses. Collectively, the classification of ARID1A-mutated tumors based on vemurafenib resistance as an additional indicator of immunotherapy response will enable a more accurate prediction to guide cancer treatment. Furthermore, the neoantigens that emerge with therapy resistance can be promising therapeutic targets for refractory tumors. Significance: Chemotherapy resistance promotes the acquisition of immunogenic neoantigens in ARID1A-deficient tumors that confer sensitivity to immune checkpoint blockade and can be utilized for developing antitumor vaccines, providing strategies to improve immunotherapy efficacy.

Therapeutic implications of the metabolic changes associated with BRAF inhibition in melanoma

Melanoma metabolism can be reprogrammed by activating BRAF mutations. These mutations are present in up to 50% of cutaneous melanomas, with the most common being V600E. BRAF mutations augment glycolysis to promote macromolecular synthesis and proliferation. Prior to the development of targeted anti-BRAF therapies, these mutations were associated with accelerated clinical disease in the metastatic setting. Combination BRAF and MEK inhibition is a first line treatment option for locally advanced or metastatic melanoma harboring targetable BRAF mutations. This therapy shows excellent response rates but these responses are not durable, with almost all patients developing resistance. When BRAF mutated melanoma cells are inhibited with targeted therapies the metabolism of those cells also changes. These cells rely less on glycolysis for energy production, and instead shift to a mitochondrial phenotype with upregulated TCA cycle activity and oxidative phosphorylation. An increased dependence on glutamine utilization is exhibited to support TCA cycle substrates in this metabolic rewiring of BRAF mutated melanoma. Herein we describe the relevant core metabolic pathways modulated by BRAF inhibition. These adaptive pathways represent vulnerabilities that could be targeted to overcome resistance to BRAF inhibitors. This review evaluates current and future therapeutic strategies that target metabolic reprogramming in melanoma cells, particularly in response to BRAF inhibition.

Multi-omics analysis delineates resistance mechanisms associated with BRAF inhibition in melanoma cells

Mutant BRAF is a critical oncogenic driver in melanoma, making it an attractive therapeutic target. However, the success of targeted therapy using BRAF inhibitors vemurafenib and dabrafenib has been limited due to development of resistance, restricting their clinical efficacy. A prior knowledge of resistance mechanisms to BRAFi or any cancer drug can lead to development of drugs that overcome resistance thus improving clinical outcomes. In vitro cellular models are powerful systems that can be utilized to mimic and study resistance mechanisms. In this study, we employed a multi-omics approach to characterize a panel of BRAF mutant melanoma cell lines to develop and systematically characterize BRAFi persister and resistant cells using exome sequencing, proteomics and phosphoproteomics. Our datasets revealed frequently observed intrinsic and acquired, genetic and non-genetic mechanisms of BRAFi resistance that have been studied in patients who developed resistance. In addition, we identified proteins that can be potentially targeted to overcome BRAFi resistance. Overall, we demonstrate that in vitro systems can be utilized not only to predict resistance mechanisms but also to identify putative therapeutic targets.

The effects of dabrafenib and/or trametinib treatment in Braf V600-mutant glioma: a systematic review and meta-analysis

This study aimed to evaluate the effects of dabrafenib and/or trametinib therapy in BRAF v600-mutant glioma treatment. PubMed, the Cochrane Library, EMBASE and Web of Science were searched from inception to Sep 2023. Inclusion criteria were designed based on the PICO principle to select relevant articles. Search keywords included 'dabrafenib', 'trametinib', 'glioma' and other related keywords. Outcomes included overall survival (OS), progression-free survival (PFS), adverse events (AEs), and death events. Methodological index for non-randomized studies (MINORS) was used to assess the methodological quality. Stata 14.0 was selected to perform the Cochrane Q and I2 statistics to test the heterogeneity among all studies. As for publication bias assessment and sensitivity analysis, the funnel plot, Egger regression test, Begg test, and trim and fill method were selected. Including 8 studies for meta-analysis. The pooled results of the single-arm trials showed that the median PFS and median OS after treatment were 6.10 months and 22.73 months, respectively. Notably, this study found a high incidence of AEs and death events of 50% and 43% after treatment. All the above findings were statistically significant. Also, this study statistically supported the advantage of disease response improvement after the combination therapy in BRAF v600-mutant glioma patients, which were shown as a pooled rate of PR (30%), a pooled rate of CR (18%), and a pooled rate of ORR (39%). And the AE rate was lower in the monotherapy group (AE: 25%) than in the combination treatment group (AE: 60%). Sensitivity analysis indicated that all the results were robust. Based on current literature outcomes, dabrafenib and/or trametinib may lead to the median PFS of 6.10 months and median OS as 22.73 months for BRAF v600-mutant glioma patients, and the safety of monotherapy is better than that of combination therapy. This conclusion needs to be treated with caution and further verified.

Advancements in Melanoma Therapies: From Surgery to Immunotherapy

OPINION STATEMENT

Melanoma is defined as the most aggressive and deadly form of skin cancer. The treatment of melanoma depends on the disease stage, tumor location, and extent of its spread from its point of origin. Melanoma treatment has made significant advances, notably in the context of targeted and immunotherapies. Surgical resection is the main therapeutic option for earlystage melanoma, and it provides favourable outcomes. With disease metastasis, systemic treatments such as immunotherapy and targeted therapy become increasingly important. The identification of mutations that lead to melanoma has influenced treatment strategies. Targeted therapies focusing on these mutations offer improved response rates and fewer toxicities than conventional chemotherapy. Furthermore, developing immunotherapies, including checkpoint inhibitors and tumor-infiltrating lymphocyte (TIL) therapies, has demonstrated encouraging outcomes in effectively combating cancer cells. These therapeutic agents demonstrate superior effectiveness and a more tolerable side-effect profile, improving the quality of life for patients receiving treatment. The future of melanoma treatment may involve a multimodal approach consisting of a combination of surgery, targeted therapy, and immunotherapy adapted to each patient's profile. This approach may improve survival rates and health outcomes.

Off-targets of BRAF inhibitors disrupt endothelial signaling and vascular barrier function

Targeted therapies against mutant BRAF are effectively used in combination with MEK inhibitors (MEKi) to treat advanced melanoma. However, treatment success is affected by resistance and adverse events (AEs). Approved BRAF inhibitors (BRAFi) show high levels of target promiscuity, which can contribute to these effects. The blood vessel lining is in direct contact with high plasma concentrations of BRAFi, but effects of the inhibitors in this cell type are unknown. Hence, we aimed to characterize responses to approved BRAFi for melanoma in the vascular endothelium. We showed that clinically approved BRAFi induced a paradoxical activation of endothelial MAPK signaling. Moreover, phosphoproteomics revealed distinct sets of off-targets per inhibitor. Endothelial barrier function and junction integrity were impaired upon treatment with vemurafenib and the next-generation dimerization inhibitor PLX8394, but not with dabrafenib or encorafenib. Together, these findings provide insights into the surprisingly distinct side effects of BRAFi on endothelial signaling and functionality. Better understanding of off-target effects could help to identify molecular mechanisms behind AEs and guide the continued development of therapies for BRAF-mutant melanoma.

Salidroside improves cognitive function in Parkinson's disease via Braf-mediated mitogen‑activated protein kinase signaling pathway

OBJECTIVE

To delve into the underlying mechanism of Salidroside (Sal) on the improvement of cognitive function in Parkinson's Disease (PD).

METHODS

The experimental mice were divided into Control group, Model group [injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)], and Model+Sal (low concentration, high concentration) group. Mouse hippocampal tissues were extracted for RNA sequencing to obtain the core pathway and core gene. Mouse plasma was prepared and analyzed by LC-MS to obtain differential metabolites. In vitro experiments were verified by immunofluorescence and lentiviral transduction.

RESULTS

ELISA signaled that Sal facilitated the reduction of neuronal damage and inflammatory reaction in mice. MPTP_Sal_Low and MPTP_Sal_High groups had high levels of glial cell derived neurotrophie factor (GDNF) expression. Differentially expressed genes (DEGs) in control group, MPTP group and MPTP_Sal_High group were identified by transcriptomic, which were classified to the mitogen-activated protein kinase (MAPK) signaling pathway, and the core gene Braf was obtained. Metabolomics manifested that the differential metabolites involved DL-tyrosine, adenosine, phosphoenolpyruvate, and L-tryptophan. In vitro experiments verified that Sal treatment inhibited the up-regulation of p-p38, p-c-Jun N-terminal kinase (JNK), and p-extracellular signal-regulated kinase (ERK) expression, and growth of neuronal protrusions. The OE-Braf group showed a significant up-regulation of the GDNF expression, a decrease in the expression of p-p38, p-JNK, and p-ERK, and a significant growth of neuronal protrusions.

CONCLUSION

Sal may exert its effects in PD through the Braf-mediated MAPK signaling pathway, which can increase GDNF expression and promote neuronal protrusion growth for the protection of neurological function and the improvement of cognitive function.

High levels of soluble CD73 unveil resistance to BRAF inhibitors in melanoma cells

Melanoma cells express high levels of CD73 that produce extracellular immunosuppressive adenosine. Changes in the CD73 expression occur in response to tumor environmental factors, contributing to tumor phenotype plasticity and therapeutic resistance. Previously, we have observed that CD73 expression can be up-regulated on the surface of melanoma cells in response to nutritional stress. Here, we explore the mechanism by which melanoma cells release soluble CD73 under low nutrient availability and whether this might be affected by agents targeting the proto-oncogene B-Raf (BRAF). We found that starved melanoma cells can release high levels of CD73, able to convert AMP into adenosine, and this activity is abrogated by selective CD73 inhibitors, APCP or PSB-12489. The release of CD73 from melanoma cells is mediated by the matrix metalloproteinase MMP-9. Indeed, MMP-9 inhibitors significantly reduce the levels of CD73 released from the cells, while its surface levels increase. Of relevance, melanoma cells, harboring an activating BRAF mutation, upon treatment with dabrafenib or vemurafenib, show a strong reduction of CD73 cell expression and reduced levels of CD73 released into the extracellular space. Conversely, melanoma cells resistant to dabrafenib show high expression of membrane-bound CD73 and soluble CD73 released into the culture medium. In summary, our data indicate that CD73 is released from melanoma cells. The expression of CD73 is associated with response to BRAF inhibitors. Melanoma cells developing resistance to dabrafenib show increased expression of CD73, including soluble CD73 released from cells, suggesting that CD73 is involved in acquiring resistance to treatment.

Fustin suppressed melanoma cell growth via cAMP/PKA-dependent mechanism

Melanoma, a cancer arising from melanocytes, requires a novel treatment strategy because of the ineffectiveness of conventional therapies in certain patients. Fustin is a flavanonol found in young fustic (Cotinus coggygria). However, little is known about its antimelanoma effects. Our study demonstrates that fustin suppresses the growth of B16 melanoma cells. Phalloidin staining of cytoskeletal actin revealed that fustin induced a conformational change in the actin structure of melanoma cells, accompanied by suppressed phosphorylation of myosin regulatory light chain 2 (MLC2), a regulator of actin structure. Furthermore, the protein kinase A (cAMP-dependent protein kinase) inhibitor H89 completely attenuated fustin-induced downregulation of phosphorylated myosin phosphatase targeting subunit 1, which is involved in dephosphorylation of MLC2. In a mouse model, administration of fustin suppressed tumor growth in B16 melanoma cells without adverse effects. In conclusion, our findings suggest that fustin effectively suppresses melanoma cell growth both in vitro and in vivo.

Polyamine and EIF5A hypusination downstream of c-Myc confers targeted therapy resistance in BRAF mutant melanoma

BACKGROUND

BRAF inhibitors are widely employed in the treatment of melanoma with the BRAF V600E mutation. However, the development of resistance compromises their therapeutic efficacy. Diverse genomic and transcriptomic alterations are found in BRAF inhibitor resistant melanoma, posing a pressing need for convergent, druggable target that reverse therapy resistant tumor with different resistance mechanisms.

METHODS

CRISPR-Cas9 screens were performed to identify novel target gene whose inhibition selectively targets A375VR, a BRAF V600E mutant cell line with acquired resistance to vemurafenib. Various in vitro and in vivo assays, including cell competition assay, water soluble tetrazolium (WST) assay, live-dead assay and xenograft assay were performed to confirm synergistic cell death. Liquid Chromatography-Mass Spectrometry analyses quantified polyamine biosynthesis and changes in proteome in vemurafenib resistant melanoma. EIF5A hypusination dependent protein translation and subsequent changes in mitochondrial biogenesis and activity were assayed by O-propargyl-puromycin labeling assay, mitotracker, mitoSOX labeling and seahorse assay. Bioinformatics analyses were used to identify the association of polyamine biosynthesis with BRAF inhibitor resistance and poor prognosis in melanoma patient cohorts.

RESULTS

We elucidate the role of polyamine biosynthesis and its regulatory mechanisms in promoting BRAF inhibitor resistance. Leveraging CRISPR-Cas9 screens, we identify AMD1 (S-adenosylmethionine decarboxylase 1), a critical enzyme for polyamine biosynthesis, as a druggable target whose inhibition reduces vemurafenib resistance. Metabolomic and proteomic analyses reveal that polyamine biosynthesis is upregulated in vemurafenib-resistant cancer, resulting in enhanced EIF5A hypusination, translation of mitochondrial proteins and oxidative phosphorylation. We also identify that sustained c-Myc levels in vemurafenib-resistant cancer are responsible for elevated polyamine biosynthesis. Inhibition of polyamine biosynthesis or c-Myc reversed vemurafenib resistance both in vitro cell line models and in vivo in a xenograft model. Polyamine biosynthesis signature is associated with poor prognosis and shorter progression free survival after BRAF/MAPK inhibitor treatment in melanoma cohorts, highlighting the clinical relevance of our findings.

CONCLUSIONS

Our findings delineate the molecular mechanisms involving polyamine-EIF5A hypusination-mitochondrial respiration pathway conferring BRAF inhibitor resistance in melanoma. These targets will serve as effective therapeutic targets that can maximize the therapeutic efficacy of existing BRAF inhibitors.

Comparative Quantitative Proteomic Analysis of Melanoma Subtypes, Nevus-Associated Melanoma, and Corresponding Nevi

A substantial part of cutaneous malignant melanomas develops from benign nevi. However, the precise molecular events driving the transformation from benign to malignant melanoma are not well-understood. We used laser microdissection and mass spectrometry to analyze the proteomes of melanoma subtypes, including superficial spreading melanomas (n = 17), nodular melanomas (n = 17), and acral melanomas (n = 15). Furthermore, we compared the proteomes of nevi cells with those of melanoma cells within the same specimens (nevus-associated melanoma (n = 14)). In total, we quantified 7935 proteins. Despite the genomic and clinical differences of the melanoma subtypes, our analysis revealed relatively similar proteomes, except for the upregulation of proteins involved in immune activation in nodular melanomas versus acral melanomas. Examining nevus-associated melanoma versus nevi, we found 1725 differentially expressed proteins (false discovery rate < 0.05). Among these proteins were 140 that overlapped with cancer hallmarks, tumor suppressors, and regulators of metabolism and cell cycle. Pathway analysis indicated aberrant activation of the phosphoinositide 3-kinase-protein kinase B-mTOR pathways and the Hippo-YAP pathway. Using a classifier, we identified six proteins capable of distinguishing melanoma from nevi samples. Our study represents a comprehensive comparative analysis of the proteome in melanoma subtypes and associated nevi, offering insights into the biological behavior of these distinct entities.

Precision nanomedicine to treat non-small cell lung cancer

Lung cancer is a major cause of death worldwide, being often detected at a later stage due to the non-appearance of early symptoms. Therefore, specificity of the treatment is of utmost importance for its effective treatment. Precision medicine is a personalized therapy based on the genomics of the patient to design a suitable drug approach. Genetic mutations render the tumor resistant to specific mutations and the therapy is in vain even though correct medications are prescribed. Therefore, Precision medicine needs to be explored for the treatment of Non-small cell lung cancer (NSCLC). Nanoparticles are widely explored to give personalized interventions to treat lung cancer due to their various advantages like the ability to reach cancer cells, enhanced permeation through tissues, specificity, increased bioavailability, etc. Various nanoparticles (NPs) including gold nanoparticles, carbon nanotubes, aptamer-based NPs etc. were conjugated with biomarkers/diagnostic agents specific to cancer type and were delivered. Various biomarker genes have been identified through precision techniques for the diagnosis and treatment of NSCLC like EGFR, RET, KRAS, ALK, ROS-1, NTRK-1, etc. By incorporating of drug with the nanoparticle through bioconjugation, the specificity of the treatment can be enhanced with this revolutionary treatment. Additionally, integration of theranostic cargos in the nanoparticle would allow diagnosis as well as treatment by targeting the site of disease progression. Therefore, to target NSCLC effectively precision nanomedicine has been adopted in recent times. Here, we present different nanoparticles that are used as precision nanomedicine and their effectiveness against NSCLC disease.

Extracellular vesicles promote migration despite BRAF inhibitor treatment in malignant melanoma cells

Extracellular vesicles (EVs) constitute a vital component of intercellular communication, exerting significant influence on metastasis formation and drug resistance mechanisms. Malignant melanoma (MM) is one of the deadliest forms of skin cancers, because of its high metastatic potential and often acquired resistance to oncotherapies. The prevalence of BRAF mutations in MM underscores the importance of BRAF-targeted therapies, such as vemurafenib and dabrafenib, alone or in combination with the MEK inhibitor, trametinib. This study aimed to elucidate the involvement of EVs in MM progression and ascertain whether EV-mediated metastasis promotion persists during single agent BRAF (vemurafenib, dabrafenib), or MEK (trametinib) and combined BRAF/MEK (dabrafenib/trametinib) inhibition.Using five pairs of syngeneic melanoma cell lines, we assessed the impact of EVs - isolated from their respective supernatants - on melanoma cell proliferation and migration. Cell viability and spheroid growth assays were employed to evaluate proliferation, while migration was analyzed through mean squared displacement (MSD) and total traveled distance (TTD) measurements derived from video microscopy and single-cell tracking.Our results indicate that while EV treatments had remarkable promoting effect on cell migration, they exerted only a modest effect on cell proliferation and spheroid growth. Notably, EVs demonstrated the ability to mitigate the inhibitory effects of BRAF inhibitors, albeit they were ineffective against a MEK inhibitor and the combination of BRAF/MEK inhibitors. In summary, our findings contribute to the understanding of the intricate role played by EVs in tumor progression, metastasis, and drug resistance in MM.

RICTOR/mTORC2 downregulation in BRAFV600E melanoma cells promotes resistance to BRAF/MEK inhibition

BACKGROUND

The main drawback of BRAF/MEK inhibitors (BRAF/MEKi)-based targeted therapy in the management of BRAF-mutated cutaneous metastatic melanoma (MM) is the development of therapeutic resistance. We aimed to assess in this context the role of mTORC2, a signaling complex defined by the presence of the essential RICTOR subunit, regarded as an oncogenic driver in several tumor types, including MM.

METHODS

After analyzing The Cancer Genome Atlas MM patients' database to explore both overall survival and molecular signatures as a function of intra-tumor RICTOR levels, we investigated the effects of RICTOR downregulation in BRAFV600E MM cell lines on their response to BRAF/MEKi. We performed proteomic screening to identify proteins modulated by changes in RICTOR expression, and Seahorse analysis to evaluate the effects of RICTOR depletion on mitochondrial respiration. The combination of BRAFi with drugs targeting proteins and processes emerged in the proteomic screening was carried out on RICTOR-deficient cells in vitro and in a xenograft setting in vivo.

RESULTS

Low RICTOR levels in BRAF-mutated MM correlate with a worse clinical outcome. Gene Set Enrichment Analysis of low-RICTOR tumors display gene signatures suggestive of activation of the mitochondrial Electron Transport Chain (ETC) energy production. RICTOR-deficient BRAFV600E cells are intrinsically tolerant to BRAF/MEKi and anticipate the onset of resistance to BRAFi upon prolonged drug exposure. Moreover, in drug-naïve cells we observed a decline in RICTOR expression shortly after BRAFi exposure. In RICTOR-depleted cells, both mitochondrial respiration and expression of nicotinamide phosphoribosyltransferase (NAMPT) are enhanced, and their pharmacological inhibition restores sensitivity to BRAFi.

CONCLUSIONS

Our work unveils an unforeseen tumor-suppressing role for mTORC2 in the early adaptation phase of BRAFV600E melanoma cells to targeted therapy and identifies the NAMPT-ETC axis as a potential therapeutic vulnerability of low RICTOR tumors. Importantly, our findings indicate that the evaluation of intra-tumor RICTOR levels has a prognostic value in metastatic melanoma and may help to guide therapeutic strategies in a personalized manner.

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.

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.

Resistance to BRAF inhibition explored through single circulating tumour cell molecular profiling in BRAF-mutant non-small-cell lung cancer

BACKGROUND

Resistance mechanisms to combination therapy with dabrafenib plus trametinib remain poorly understood in patients with BRAFV600E-mutant advanced non-small-cell lung cancer (NSCLC). We examined resistance to BRAF inhibition by single CTC sequencing in BRAFV600E-mutant NSCLC.

METHODS

CTCs and cfDNA were examined in seven BRAFV600E-mutant NSCLC patients at failure to treatment. Matched tumour tissue was available for four patients. Single CTCs were isolated by fluorescence-activated cell sorting following enrichment and immunofluorescence (Hoechst 33342/CD45/pan-cytokeratins) and sequenced for mutation and copy number-alteration (CNA) analyses.

RESULTS

BRAFV600E was found in 4/4 tumour biopsies and 5/7 cfDNA samples. CTC mutations were mostly found in MAPK-independent pathways and only 1/26 CTCs were BRAFV600E mutated. CTC profiles encompassed the majority of matched tumour biopsy CNAs but 72.5% to 84.5% of CTC CNAs were exclusive to CTCs. Extensive diversity, involving MAPK, MAPK-related, cell cycle, DNA repair and immune response pathways, was observed in CTCs and missed by analyses on tumour biopsies and cfDNA. Driver alterations in clinically relevant genes were recurrent in CTCs.

CONCLUSIONS

Resistance was not driven by BRAFV600E-mutant CTCs. Extensive tumour genomic heterogeneity was found in CTCs compared to tumour biopsies and cfDNA at failure to BRAF inhibition, in BRAFV600E-mutant NSCLC, including relevant alterations that may represent potential treatment opportunities.

Mechanisms of Melanoma Progression and Treatment Resistance: Role of Cancer Stem-like Cells

Melanoma is the third most common type of skin cancer, characterized by its heterogeneity and propensity to metastasize to distant organs. Melanoma is a heterogeneous tumor, composed of genetically divergent subpopulations, including a small fraction of melanoma-initiating cancer stem-like cells (CSCs) and many non-cancer stem cells (non-CSCs). CSCs are characterized by their unique surface proteins associated with aberrant signaling pathways with a causal or consequential relationship with tumor progression, drug resistance, and recurrence. Melanomas also harbor significant alterations in functional genes (BRAF, CDKN2A, NRAS, TP53, and NF1). Of these, the most common are the BRAF and NRAS oncogenes, with 50% of melanomas demonstrating the BRAF mutation (BRAFV600E). While the successful targeting of BRAFV600E does improve overall survival, the long-term efficacy of available therapeutic options is limited due to adverse side effects and reduced clinical efficacy. Additionally, drug resistance develops rapidly via mechanisms involving fast feedback re-activation of MAPK signaling pathways. This article updates information relevant to the mechanisms of melanoma progression and resistance and particularly the mechanistic role of CSCs in melanoma progression, drug resistance, and recurrence.

Drug dependence in cancer is exploitable by optimally constructed treatment holidays

Cancers with acquired resistance to targeted therapy can become simultaneously dependent on the presence of the targeted therapy drug for survival, suggesting that intermittent therapy may slow resistance. However, relatively little is known about which tumours are likely to become dependent and how to schedule intermittent therapy optimally. Here we characterized drug dependence across a panel of over 75 MAPK-inhibitor-resistant BRAFV600E mutant melanoma models at the population and single-clone levels. Melanocytic differentiated models exhibited a much greater tendency to give rise to drug-dependent progeny than their dedifferentiated counterparts. Mechanistically, acquired loss of microphthalmia-associated transcription factor in differentiated melanoma models drives ERK-JunB-p21 signalling to enforce drug dependence. We identified the optimal scheduling of 'drug holidays' using simple mathematical models that we validated across short and long timescales. Without detailed knowledge of tumour characteristics, we found that a simple adaptive therapy protocol can produce near-optimal outcomes using only measurements of total population size. Finally, a spatial agent-based model showed that optimal schedules derived from exponentially growing cells in culture remain nearly optimal in the context of tumour cell turnover and limited environmental carrying capacity. These findings may guide the implementation of improved evolution-inspired treatment strategies for drug-dependent cancers.

Magnetic Delivery of Antigen-Loaded Magnetic Liposomes for Active Lymph Node Targeting and Enhanced Anti-Tumor Immunity

Therapeutic cancer vaccines offer the greatest advantage of enhancing antigen-specific immunity against tumors, particularly for immunogenic tumors, such as melanoma. However, clinical responses remain unsatisfactory, primarily due to inadequate T cell priming and the development of acquired immune tolerance. A major obstacle lies in the inefficient uptake of antigen by peripheral dendritic cells (DCs) and their migration to lymph nodes for antigen presentation. In this context, the magnetic delivery of antigen-loaded magnetic liposomes (Ag-MLs) to actively target lymph node, is proposed. These magnetic responsive liposomes contain soluble mouse melanoma lysate and iron oxide nanoparticles in the core, along with the immunostimulatory adjuvant CpG-1826 incorporated into the lipid bilayer. When applied through magnetic targeting in the mouse melanoma model, Ag-MLs accumulate significantly in the target lymph nodes. This accumulation results in increased population of active DCs in lymph nodes and cytotoxic T lymphocytes (CTLs) within tumors, correlating with effective tumor growth inhibition. Overall, this study demonstrates the potential of magnetic targeting as an effective strategy for delivering cancer vaccines and activating the immune response, offering a novel platform for cancer immunotherapies.

Six-Membered Aromatic Nitrogen Heterocyclic Anti-Tumor Agents: Synthesis and Applications

Cancer stands as a serious malady, posing substantial risks to human well-being and survival. This underscores the paramount necessity to explore and investigate novel antitumor medications. Nitrogen-containing compounds, especially those derived from natural sources, form a highly significant category of antitumor agents. Among these, antitumor agents with six-membered aromatic nitrogen heterocycles have consistently attracted the attention of chemists and pharmacologists. Accordingly, we present a comprehensive summary of synthetic strategies and clinical implications of these compounds in this review. This entails an in-depth analysis of synthesis pathways for pyridine, quinoline, pyrimidine, and quinazoline. Additionally, we explore the historical progression, targets, mechanisms of action, and clinical effectiveness of small molecule inhibitors possessing these structural features.

MitoTracer facilitates the identification of informative mitochondrial mutations for precise lineage reconstruction

Mitochondrial (MT) mutations serve as natural genetic markers for inferring clonal relationships using single cell sequencing data. However, the fundamental challenge of MT mutation-based lineage tracing is automated identification of informative MT mutations. Here, we introduced an open-source computational algorithm called "MitoTracer", which accurately identified clonally informative MT mutations and inferred evolutionary lineage from scRNA-seq or scATAC-seq samples. We benchmarked MitoTracer using the ground-truth experimental lineage sequencing data and demonstrated its superior performance over the existing methods measured by high sensitivity and specificity. MitoTracer is compatible with multiple single cell sequencing platforms. Its application to a cancer evolution dataset revealed the genes related to primary BRAF-inhibitor resistance from scRNA-seq data of BRAF-mutated cancer cells. Overall, our work provided a valuable tool for capturing real informative MT mutations and tracing the lineages among cells.

Teaser

MitoTracer enables automatically and accurately discover informative mitochondrial mutations for lineage tracing.

Activated MKK3/MYC crosstalk impairs dabrafenib response in BRAFV600E colorectal cancer leading to resistance

Colorectal cancer (CRC) patients with BRAF mutations develop resistance to BRAF inhibitors at a very early stage. Understanding the molecular mechanisms involved in BRAF inhibitor resistance is critical for the development of novel therapeutic opportunities for this subtype of CRC patients. CRC cells bearing BRAF mutations are mostly sensitive to the abrogation of Mitogen-Activated Protein Kinase Kinase 3 (MKK3), a specific activator of p38MAPKs signaling, suggesting that BRAF alterations might addict CRC cells to the MKK3/p38MAPK signaling. Interestingly, publicly available gene expression profiling data show significantly higher MKK3 transcript levels in CRC lines with acquired resistance to BRAF inhibitors. Herein, we investigated the roles of MKK3 in the response to BRAF targeting (dabrafenib) with COLO205 and HT29 BRAFV600E CRC lines and derived dabrafenib-resistant (DABR) sublines. Dabrafenib treatments reduce MKK3 activation by inducing autophagy in parental but not DABR cells. The MKK3 knockdown induces cell death in DABR cells, whereas ectopic MKK3 expression reduces dabrafenib sensitivity in parental cells. Mechanistically, activated MKK3 interacts and co-localizes with c-Myc oncoprotein (MYC), sustaining MYC protein stability and thus preventing the dabrafenib induced effects in CRC DABR cells both in vitro and in vivo. Overall, we identify a novel molecular mechanism beyond the dabrafenib resistance, shedding light on an uncovered vulnerability for the development of novel therapeutic opportunities in BRAFV600E CRC.

Understanding cancer drug resistance with Sleeping Beauty functional genomic screens: Application to MAPK inhibition in cutaneous melanoma

Combined BRAF and MEK inhibition is an effective treatment for BRAF-mutant cutaneous melanoma. However, most patients progress on this treatment due to drug resistance. Here, we applied the Sleeping Beauty transposon system to understand how melanoma evades MAPK inhibition. We found that the specific drug resistance mechanisms differed across melanomas in our genetic screens of five cutaneous melanoma cell lines. While drivers that reactivated MAPK were highly conserved, many others were cell-line specific. One such driver, VAV1, activated a de-differentiated transcriptional program like that of hyperactive RAC1, RAC1P29S. To target this mechanism, we showed that an inhibitor of SRC, saracatinib, blunts the VAV1-induced transcriptional reprogramming. Overall, we highlighted the importance of accounting for melanoma heterogeneity in treating cutaneous melanoma with MAPK inhibitors. Moreover, we demonstrated the utility of the Sleeping Beauty transposon system in understanding cancer drug resistance.

Successes and challenges in modeling heterogeneous BRAFV600E mutated central nervous system neoplasms

Central nervous system (CNS) neoplasms are difficult to treat due to their sensitive location. Over the past two decades, the availability of patient tumor materials facilitated large scale genomic and epigenomic profiling studies, which have resulted in detailed insights into the molecular underpinnings of CNS tumorigenesis. Based on results from these studies, CNS tumors have high molecular and cellular intra-tumoral and inter-tumoral heterogeneity. CNS cancer models have yet to reflect the broad diversity of CNS tumors and patients and the lack of such faithful cancer models represents a major bottleneck to urgently needed innovations in CNS cancer treatment. Pediatric cancer model development is lagging behind adult tumor model development, which is why we focus this review on CNS tumors mutated for BRAFV600E which are more prevalent in the pediatric patient population. BRAFV600E-mutated CNS tumors exhibit high inter-tumoral heterogeneity, encompassing clinically and histopathological diverse tumor types. Moreover, BRAFV600E is the second most common alteration in pediatric low-grade CNS tumors, and low-grade tumors are notoriously difficult to recapitulate in vitro and in vivo. Although the mutation predominates in low-grade CNS tumors, when combined with other mutations, most commonly CDKN2A deletion, BRAFV600E-mutated CNS tumors are prone to develop high-grade features, and therefore BRAFV600E-mutated CNS are a paradigm for tumor progression. Here, we describe existing in vitro and in vivo models of BRAFV600E-mutated CNS tumors, including patient-derived cell lines, patient-derived xenografts, syngeneic models, and genetically engineered mouse models, along with their advantages and shortcomings. We discuss which research gaps each model might be best suited to answer, and identify those areas in model development that need to be strengthened further. We highlight areas of potential research focus that will lead to the heightened predictive capacity of preclinical studies, allow for appropriate validation, and ultimately improve the success of "bench to bedside" translational research.

The impact of cellular elements of TME on melanoma biology and its sensitivity to EGFR and MET targeted therapy

Microenvironment of the melanoma consists of cellular elements like fibroblasts, adipocytes, and keratinocytes as well as extracellular matrix and physicochemical conditions. In our previous research, we have established that melanoma influences strongly above mentioned cells present in the tumor niche and recruits them to support cancer progression. In this work, we evaluated the impact of cancer-associated cells, namely fibroblasts (CAFs), adipocytes (CAAs), and keratinocytes (CAKs) on melanoma proliferation, signaling pathways activation, metabolism as well as the effectiveness of used anti-cancer therapy. Obtained results indicated elevated phosphorylation of STAT3, upregulated GLUT1 and GLUT3 as well as downregulated of MCT-1 expression level in melanoma cells under the influence of all examined cells present in the tumor niche. The proliferation of melanoma cells was increased after co-culture with CAFs and CAKs, while epithelial-mesenchymal transition markers' expression level was raised in the presence of CAFs and CAAs. The level of perilipin 2 and lipid content was elevated in melanoma cells under the influence of CAAs. Moreover, increased expression of CYP1A1, gene encoding drug metabolizing protein, in melanoma cells co-cultured with CAFs and CAKs prompted us to verify the effectiveness of the previously proposed by us anti-melanoma therapy based on combination of EGFR and MET inhibitors. Obtained results indicate that the designed therapy is still efficient, even if the fibroblasts, adipocytes, and keratinocytes, are present in the melanoma vicinity.

The Cytoprotective Role of Autophagy in Response to BRAF-Targeted Therapies

BRAF-targeted therapies are widely used for the treatment of melanoma patients with BRAF V600 mutations. Vemurafenib, dabrafenib as well as encorafenib have demonstrated substantial therapeutic activity; however, as is the case with other chemotherapeutic agents, the frequent development of resistance limits their efficacy. Autophagy is one tumor survival mechanism that could contribute to BRAF inhibitor resistance, and multiple studies support an association between vemurafenib-induced and dabrafenib-induced autophagy and tumor cell survival. Clinical trials have also demonstrated a potential benefit from the inclusion of autophagy inhibition as an adjuvant therapy. This review of the scientific literature relating to the role of autophagy that is induced in response to BRAF-inhibitors supports the premise that autophagy targeting or modulation could be an effective adjuvant therapy.

Kisspeptin-mediated improvement of sensitivity to BRAF inhibitors in vemurafenib-resistant melanoma cells

Metastatic dissemination is still one of the major causes of death of melanoma's patients. KiSS1 is a metastasis suppressor originally identified in melanoma cells, known to play an important physiological role in mammals' development and puberty. It has been previously shown that expression of KiSS1 could be increased in lung cancer cells using epigenetic agents, and that KiSS1 could have a pro-apoptotic action in combination with cisplatin. Thus, the aim of the present study was to examine in human melanoma vemurafenib sensitive- and -resistant BRAF mutant cells characterized by different mutational profiles and KiSS1, KiSS1 receptor and KiSS1 drug-induced release, if peptides derived from KiSS1 cleavage, i.e., kisspeptin 54, could increase the sensitivity to vemurafenib of human melanoma, using cellular, molecular and biochemical approaches. We found that kisspeptin 54 increases vemurafenib pro-apoptotic activity in a statistically significant manner, also in drug resistant cellular models. The efficacy of the combination appears to reflect the intrinsic susceptibility of each cell line to PLX4032-induced apoptosis, together with the different mutational profile as well as perturbation of proteins regulating the apoptotic pathway, The results presented here highlight the possibility to exploit KiSS1 to modulate the apoptotic response to therapeutically relevant agents, suggesting a multitasking function of this metastasis suppressor.

Therapeutic strategies for BRAF mutation in non-small cell lung cancer: a review

Lung cancer is the leading cause of cancer related deaths. Among the two broad types of lung cancer, non-small cell lung cancer accounts for 85% of the cases. The study of the genetic alteration has facilitated the development of targeted therapeutic interventions. Some of the molecular alterations which are important targets for drug therapy include Kirsten rat sarcoma (KRAS), Epidermal Growth Factor Receptor (EGFR), V-RAF murine sarcoma viral oncogene homolog B (BRAF), anaplastic lymphoma kinase gene (ALK). In the setting of extensive on-going clinical trials, it is imperative to periodically review the advancements and the newer drug therapies being available. Among all mutations, BRAF mutation is common with incidence being 8% overall and 1.5 - 4% in NSCLC. Here, we have summarized the BRAF mutation types and reviewed the various drug therapy available - for both V600 and nonV600 group; the mechanism of resistance to BRAF inhibitors and strategies to overcome it; the significance of comprehensive profiling of concurrent mutations, and the role of immune checkpoint inhibitor in BRAF mutated NSCLC. We have also included the currently ongoing clinical trials and recent advancements including combination therapy that would play a role in improving the overall survival and outcome of NSCLC.

PLX4032 resistance of patient-derived melanoma cells: crucial role of oxidative metabolism

Background

Malignant melanoma is the most lethal form of skin cancer which shows BRAF mutation in 50% of patients. In this context, the identification of BRAFV600E mutation led to the development of specific inhibitors like PLX4032. Nevertheless, although its initial success, its clinical efficacy is reduced after six-months of therapy leading to cancer relapse due to the onset of drug resistance. Therefore, investigating the mechanisms underlying PLX4032 resistance is fundamental to improve therapy efficacy. In this context, several models of PLX4032 resistance have been developed, but the discrepancy between in vitro and in vivo results often limits their clinical translation.

Methods

The herein reported model has been realized by treating with PLX4032, for six months, patient-derived BRAF-mutated melanoma cells in order to obtain a reliable model of acquired PLX4032 resistance that could be predictive of patient's treatment responses. Metabolic analyses were performed by evaluating glucose consumption, ATP synthesis, oxygen consumption rate, P/O ratio, ATP/AMP ratio, lactate release, lactate dehydrogenase activity, NAD+/NADH ratio and pyruvate dehydrogenase activity in parental and drug resistant melanoma cells. The intracellular oxidative state was analyzed in terms of reactive oxygen species production, glutathione levels and NADPH/NADP+ ratio. In addition, a principal component analysis was conducted in order to identify the variables responsible for the acquisition of targeted therapy resistance.

Results

Collectively, our results demonstrate, for the first time in patient-derived melanoma cells, that the rewiring of oxidative phosphorylation and the maintenance of pyruvate dehydrogenase activity and of high glutathione levels contribute to trigger the onset of PLX4032 resistance.

Conclusion

Therefore, it is possible to hypothesize that inhibitors of glutathione biosynthesis and/or pyruvate dehydrogenase activity could be used in combination with PLX4032 to overcome drug resistance of BRAF-mutated melanoma patients. However, the identification of new adjuvant targets related to drug-induced metabolic reprogramming could be crucial to counteract the failure of targeted therapy in metastatic melanoma.

Impairment of SK-MEL-28 Development-A Human Melanoma Cell Line-By the Crataeva tapia Bark Lectin and Its Sequence-Derived Peptides

Melanoma is difficult to treat with chemotherapy, prompting the need for new treatments. Protease inhibitors have emerged as promising candidates as tumor cell proteases promote metastasis. Researchers have developed a chimeric form of the Bauhinia bauhinioides kallikrein inhibitor, rBbKIm, which has shown negative effects on prostate tumor cell lines DU145 and PC3. Crataeva tapia bark lectin, CrataBL, targets sulfated oligosaccharides in glycosylated proteins and has also demonstrated deleterious effects on prostate and glioblastoma tumor cells. However, neither rBbKIm nor its derived peptides affected the viability of SK-MEL-28, a melanoma cell line, while CrataBL decreased viability by over 60%. Two peptides, Pep. 26 (Ac-Q-N-S-S-L-K-V-V-P-L-NH2) and Pep. 27 (Ac-L-P-V-V-K-L-S-S-N-Q-NH2), were also tested. Pep. 27 suppressed cell migration and induced apoptosis when combined with vemurafenib, while Pep. 26 inhibited cell migration and reduced nitric oxide and the number of viable cells. Vemurafenib, a chemotherapy drug used to treat melanoma, was found to decrease the release of interleukin 8 and PDGF-AB/BB cytokines and potentiated the effects of proteins and peptides in reducing these cytokines. These findings suggest that protease inhibitors may be effective in blocking melanoma cells and highlight the potential of CrataBL and its derived peptides.

Late-Stage Metastatic Melanoma Emerges through a Diversity of Evolutionary Pathways

Understanding the evolutionary pathways to metastasis and resistance to immune-checkpoint inhibitors (ICI) in melanoma is critical for improving outcomes. Here, we present the most comprehensive intrapatient metastatic melanoma dataset assembled to date as part of the Posthumous Evaluation of Advanced Cancer Environment (PEACE) research autopsy program, including 222 exome sequencing, 493 panel-sequenced, 161 RNA sequencing, and 22 single-cell whole-genome sequencing samples from 14 ICI-treated patients. We observed frequent whole-genome doubling and widespread loss of heterozygosity, often involving antigen-presentation machinery. We found KIT extrachromosomal DNA may have contributed to the lack of response to KIT inhibitors of a KIT-driven melanoma. At the lesion-level, MYC amplifications were enriched in ICI nonresponders. Single-cell sequencing revealed polyclonal seeding of metastases originating from clones with different ploidy in one patient. Finally, we observed that brain metastases that diverged early in molecular evolution emerge late in disease. Overall, our study illustrates the diverse evolutionary landscape of advanced melanoma.

SIGNIFICANCE

Despite treatment advances, melanoma remains a deadly disease at stage IV. Through research autopsy and dense sampling of metastases combined with extensive multiomic profiling, our study elucidates the many mechanisms that melanomas use to evade treatment and the immune system, whether through mutations, widespread copy-number alterations, or extrachromosomal DNA. See related commentary by Shain, p. 1294. This article is highlighted in the In This Issue feature, p. 1275.

Sustained release hydrogel for durable locoregional chemoimmunotherapy for BRAF-mutated melanoma

The wide prevalence of BRAF mutations in diagnosed melanomas drove the clinical advancement of BRAF inhibitors in combination with immune checkpoint blockade for treatment of advanced disease. However, deficits in therapeutic potencies and safety profiles motivate the development of more effective strategies that improve the combination therapy's therapeutic index. Herein, we demonstrate the benefits of a locoregional chemoimmunotherapy delivery system, a novel thermosensitive hydrogel comprised of gelatin and Pluronic® F127 components already widely used in humans in both commercial and clinical products, for the co-delivery of a small molecule BRAF inhibitor with immune checkpoint blockade antibody for the treatment of BRAF-mutated melanoma. In vivo evaluation of administration route and immune checkpoint target effects revealed intratumoral administration of antagonistic programmed cell death protein 1 antibody (aPD-1) lead to potent antitumor therapy in combination with BRAF inhibitor vemurafenib. The thermosensitive F127-g-Gelatin hydrogel that was evaluated in multiple murine models of BRAF-mutated melanoma that facilitated prolonged local drug release within the tumor (>1 week) substantially improved local immunomodulation, tumor control, rates of tumor response, and animal survival. Thermosensitive F127-g-Gelatin hydrogels thus improve upon the clinical benefits of vemurafenib and aPD-1 in a locoregional chemoimmunotherapy approach for the treatment of BRAF-mutated melanoma.

Oral IRAK-4 Inhibitor CA-4948 Is Blood-Brain Barrier Penetrant and Has Single-Agent Activity against CNS Lymphoma and Melanoma Brain Metastases

PURPOSE

An ongoing challenge in cancer is the management of primary and metastatic brain malignancies. This is partly due to restrictions of the blood-brain barrier and their unique microenvironment. These challenges are most evident in cancers such as lymphoma and melanoma, which are typically responsive to treatment in systemic locations but resistant when established in the brain. We propose interleukin-1 receptor-associated kinase-4 (IRAK-4) as a potential target across these diseases and describe the activity and mechanism of oral IRAK-4 inhibitor CA-4948.

EXPERIMENTAL DESIGN

Human primary central nervous system lymphoma (PCNSL) and melanoma brain metastases (MBM) samples were analyzed for expression of IRAK-4 and downstream transcription pathways. We next determined the central nervous system (CNS) applicability of CA-4948 in naïve and tumor-bearing mice using models of PCNSL and MBM. The mechanistic effect on tumors and the tumor microenvironment was then analyzed.

RESULTS

Human PCNSL and MBM have high expression of IRAK-4, IRAK-1, and nuclear factor kappa B (NF-κB). This increase in inflammation results in reflexive inhibitory signaling. Similar profiles are observed in immunocompetent murine models. Treatment of tumor-bearing animals with CA-4948 results in the downregulation of mitogen-activated protein kinase (MAPK) signaling in addition to decreased NF-κB. These intracellular changes are associated with a survival advantage.

CONCLUSIONS

IRAK-4 is an attractive target in PCNSL and MBM. The inhibition of IRAK-4 with CA-4948 downregulates the expression of important transcription factors involved in tumor growth and proliferation. CA-4948 is currently being investigated in clinical trials for relapsed and refractory lymphoma and warrants further translation into PCNSL and MBM.

TARGETING OF PDGF-C/NRP-1 AUTOCRINE LOOP AS A NEW STRATEGY FOR COUNTERACTING THE INVASIVENESS OF MELANOMA RESISTANT TO BRAF INHIBITORS

Melanoma resistance to BRAF inhibitors (BRAFi) is often accompanied by a switch from a proliferative to an invasive phenotype. Therefore, the identification of signaling molecules involved in the development of metastatic properties by resistant melanoma cells is of primary importance. We have previously demonstrated that activation of neuropilin-1 (NRP-1) by platelet-derived growth factor (PDGF)-C confers melanoma cells with an invasive behavior similar to that of BRAFi resistant tumors. Aims of the present study were to evaluate the role of PDGF-C/NRP-1 autocrine loop in the acquisition of an invasive and BRAFi-resistant phenotype by melanoma cells and the effect of its inhibition on drug resistance and extracellular matrix (ECM) invasion. Furthermore, we investigated whether PDGF-C serum levels were differentially modulated by drug treatment in metastatic melanoma patients responsive or refractory to BRAFi as a single agent or in combination with MEK inhibitors (MEKi). The results indicated that human melanoma cells resistant to BRAFi express higher levels of PDGF-C and NRP-1 as compared to their susceptible counterparts. Overexpression occurs early during development of drug resistance and contributes to the invasive properties of resistant cells. Accordingly, silencing of NRP-1 or PDGF-C reduces tumor cell invasiveness. Analysis of PDGF-C in the serum collected from patients treated with BRAFi or BRAFi+MEKi, showed that in responders PDGF-C levels decrease after treatment and raise again at tumor progression. Conversely, in non-responders treatment does not affect PDGF-C serum levels. Thus, blockade of NRP-1 activation by PDGF-C might represent a new therapeutic approach to counteract the invasiveness of BRAFi-resistant melanoma.

Established and Emerging Cancer Therapies and Cardiovascular System: Focus on Hypertension-Mechanisms and Mitigation

Cardiovascular disease and cancer are 2 of the leading causes of death worldwide. Although improvements in outcomes have been noted for both disease entities, the success of cancer therapies has come at the cost of at times very impactful adverse events such as cardiovascular events. Hypertension has been noted as both, a side effect as well as a risk factor for the cardiotoxicity of cancer therapies. Some of these dynamics are in keeping with the role of hypertension as a cardiovascular risk factor not only for heart failure, but also for the development of coronary and cerebrovascular disease, and kidney disease and its association with a higher morbidity and mortality overall. Other aspects such as the molecular mechanisms underlying the amplification of acute and long-term cardiotoxicity risk of anthracyclines and increase in blood pressure with various cancer therapeutics remain to be elucidated. In this review, we cover the latest clinical data regarding the risk of hypertension across a spectrum of novel anticancer therapies as well as the underlying known or postulated pathophysiological mechanisms. Furthermore, we review the acute and long-term implications for the amplification of the development of cardiotoxicity with drugs not commonly associated with hypertension such as anthracyclines. An outline of management strategies, including pharmacological and lifestyle interventions as well as models of care aimed to facilitate early detection and more timely management of hypertension in patients with cancer and survivors concludes this review, which overall aims to improve both cardiovascular and cancer-specific outcomes.

BET inhibitors synergize with sunitinib in melanoma through GDF15 suppression

Targeting bromodomain and extra-terminal domain (BET) proteins has shown a promising therapeutic effect on melanoma. The development of strategies to better kill melanoma cells with BET inhibitor treatment may provide new clinical applications. Here, we used a drug synergy screening approach to combine JQ1 with 240 antitumor drugs from the Food and Drug Administration (FDA)-approved drug library and found that sunitinib synergizes with BET inhibitors in melanoma cells. We further demonstrated that BET inhibitors synergize with sunitinib in melanoma by inducing apoptosis and cell cycle arrest. Mechanistically, BET inhibitors sensitize melanoma cells to sunitinib by inhibiting GDF15 expression. Strikingly, GDF15 is transcriptionally regulated directly by BRD4 or indirectly by the BRD4/IL6/STAT3 axis. Xenograft assays revealed that the combination of BET inhibitors with sunitinib causes melanoma suppression in vivo. Altogether, these findings suggest that BET inhibitor-mediated GDF15 inhibition plays a critical role in enhancing sunitinib sensitivity in melanoma, indicating that BET inhibitors synergize with sunitinib in melanoma.

Vemurafenib and Dabrafenib Downregulates RIPK4 Level

Vemurafenib and dabrafenib are BRAF kinase inhibitors (BRAFi) used for the treatment of patients with melanoma carrying the V600E BRAF mutation. However, melanoma cells develop resistance to both drugs when used as monotherapy. Therefore, mechanisms of drug resistance are investigated, and new molecular targets are sought that could completely inhibit melanoma progression. Since receptor-interacting protein kinase (RIPK4) probably functions as an oncogene in melanoma and its structure is similar to the BRAF protein, we analyzed the impact of vemurafenib and dabrafenib on RIPK4 in melanomas. The in silico study confirmed the high similarity of BRAF kinase domains to the RIPK4 protein at both the sequence and structural levels and suggests that BRAFi could directly bind to RIPK4 even more strongly than to ATP. Furthermore, BRAFi inhibited ERK1/2 activity and lowered RIPK4 protein levels in BRAF-mutated melanoma cells (A375 and WM266.4), while in wild-type BRAF cells (BLM and LoVo), both inhibitors decreased the level of RIPK4 and enhanced ERK1/2 activity. The phosphorylation of phosphatidylethanolamine binding protein 1 (PEBP1)-a suppressor of the BRAF/MEK/ERK pathway-via RIPK4 observed in pancreatic cancer did not occur in melanoma. Neither downregulation nor upregulation of RIPK4 in BRAF- mutated cells affected PEBP1 levels or the BRAF/MEK/ERK pathway. The downregulation of RIPK4 inhibited cell proliferation and the FAK/AKT pathway, and increased BRAFi efficiency in WM266.4 cells. However, the silencing of RIPK4 did not induce apoptosis or necroptosis. Our study suggests that RIPK4 may be an off-target for BRAF inhibitors.

Response and resistance to BRAFV600E inhibition in gliomas: Roadblocks ahead?

BRAF^V600E represents the most common BRAF mutation in all human cancers. Among central nervous system (CNS) tumors, BRAF^V600E is mostly found in pediatric low-grade gliomas (pLGG, ~20%) and, less frequently, in pediatric high-grade gliomas (pHGG, 5-15%) and adult glioblastomas (GBM, ~5%). The integration of BRAF inhibitors (BRAFi) in the treatment of patients with gliomas brought a paradigm shift to clinical care. However, not all patients benefit from treatment due to intrinsic or acquired resistance to BRAF inhibition. Defining predictors of response, as well as developing strategies to prevent resistance to BRAFi and overcome post-BRAFi tumor progression/rebound growth are some of the main challenges at present in the field. In this review, we outline current achievements and limitations of BRAF inhibition in gliomas, with a special focus on potential mechanisms of resistance. We discuss future directions of targeted therapy for BRAF^V600E mutated gliomas, highlighting how insights into resistance to BRAFi could be leveraged to improve outcomes.

Silencing FOXP2 reverses vemurafenib resistance in BRAFV600E mutant papillary thyroid cancer and melanoma cells

BACKGROUND

Vemurafenib (VEM) is a commonly used inhibitor of papillary thyroid cancer (PTC) and melanoma with the BRAFV600E mutation; however, acquired resistance is unavoidable. The present study aimed to identify a potential target to reverse resistance.

MATERIALS AND METHODS

A VEM-resistant PTC cell line (B-CPAP/VR) was established by gradually increasing the drug concentration, and a VEM-resistant BRAFV600E melanoma cell line (A375/VR) was also established. RNA sequencing and bioinformatics analyses were conducted to identify dysregulated genes and construct a transcription factor (TF) network. The role of a potential TF, forkhead box P2 (FOXP2), verified by qRT-PCR, was selected for further confirmation.

RESULTS

The two resistant cell lines were tolerant of VEM and displayed higher migration and colony formation abilities (p < 0.05). RNA sequencing identified 9177 dysregulated genes in the resistant cell lines, and a TF network consisting of 13 TFs and 44 target genes was constructed. Alterations in FOXP2 expression were determined to be consistent between the two VEM-resistant cell lines. Finally, silencing FOXP2 resulted in an increase in drug sensitivity and significant suppression of the migration and colony formation abilities of the two resistant cell lines (p < 0.05).

CONCLUSIONS

The present study successfully established two VEM-resistant cell lines and identified a potential target for VEM-resistant PTC or melanoma.