Metastatic melanoma is an aggressive disease, despite recent improvements in therapy. Eradicating all melanoma cells even in drug-sensitive tumors is unsuccessful in patients because a subset of ...cells can transition to a slow-cycling state, rendering them resistant to most targeted therapy. It is still unclear what pathways define these subpopulations and promote this resistant phenotype. In the current study, we show that Wnt5A, a non-canonical Wnt ligand that drives a metastatic, therapy-resistant phenotype, stabilizes the half-life of p53 and uses p53 to initiate a slow-cycling state following stress (DNA damage, targeted therapy, and aging). Inhibiting p53 blocks the slow-cycling phenotype and sensitizes melanoma cells to BRAF/MEK inhibition. In vivo, this can be accomplished with a single dose of p53 inhibitor at the commencement of BRAF/MEK inhibitor therapy. These data suggest that taking the paradoxical approach of inhibiting rather than activating wild-type p53 may sensitize previously resistant metastatic melanoma cells to therapy.
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•Wnt5A increases the half-life of wild-type p53 to promote a slow-cycling phenotype•Multiple types of stress increase Wnt5A and p53 expression in metastatic melanoma•Inhibiting p53 sensitizes melanoma cells to BRAF/MEK inhibitor therapy
Cancer cells adopt multiple ways to evade therapy, including adopting a slow-cycling phenotype to resist drugs that target rapidly proliferating cells. Webster et al. show by circumventing this slow-cycling state through inhibition of p53, cells can be sensitized to targeted therapies that affect proliferation pathways such as the MAPK pathway.
Melanoma is a highly plastic tumor characterized by dynamic interconversion of different cell identities depending on the biological context. Melanoma cells with high expression of the H3K4 ...demethylase KDM5B (JARID1B) rest in a slow-cycling, yet reversible persister state. Over time, KDM5B
cells can promote rapid tumor repopulation with equilibrated KDM5B expression heterogeneity. The cellular identity of KDM5B
persister cells has not been studied so far, missing an important cell state-directed treatment opportunity in melanoma. Here, we have established a doxycycline-titratable system for genetic induction of permanent intratumor expression of KDM5B and screened for chemical agents that phenocopy this effect. Transcriptional profiling and cell functional assays confirmed that the dihydropyridine 2-phenoxyethyl 4-(2-fluorophenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxylate (termed Cpd1) supports high KDM5B expression and directs melanoma cells towards differentiation along the melanocytic lineage and to cell cycle-arrest. The high KDM5B state additionally prevents cell proliferation through negative regulation of cytokinetic abscission. Moreover, treatment with Cpd1 promoted the expression of the melanocyte-specific tyrosinase gene specifically sensitizing melanoma cells for the tyrosinase-processed antifolate prodrug 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG). In summary, our study provides proof-of-concept for a dual hit strategy in melanoma, in which persister state-directed transitioning limits tumor plasticity and primes melanoma cells towards lineage-specific elimination.
Activating mutations in PIK3CA are frequently found in estrogen-receptor-positive (ER+) breast cancer, and the combination of the phosphatidylinositol 3-kinase (PI3K) inhibitor alpelisib with anti-ER ...inhibitors is approved for therapy. We have previously demonstrated that the PI3K pathway regulates ER activity through phosphorylation of the chromatin modifier KMT2D. Here, we discovered a methylation site on KMT2D, at K1330 directly adjacent to S1331, catalyzed by the lysine methyltransferase SMYD2. SMYD2 loss attenuates alpelisib-induced KMT2D chromatin binding and alpelisib-mediated changes in gene expression, including ER-dependent transcription. Knockdown or pharmacological inhibition of SMYD2 sensitizes breast cancer cells, patient-derived organoids, and tumors to PI3K/AKT inhibition and endocrine therapy in part through KMT2D K1330 methylation. Together, our findings uncover a regulatory crosstalk between post-translational modifications that fine-tunes KMT2D function at the chromatin. This provides a rationale for the use of SMYD2 inhibitors in combination with PI3Kα/AKT inhibitors in the treatment of ER+/PIK3CA mutant breast cancer.
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•KMT2D is methylated at K1330 by SMYD2•There is crosstalk between phosphorylation of KMT2D at S1331 and methylation at K1330•Loss of SMYD2 abrogates PI3Ki-induced KMT2D chromatin binding and ER-dependent transcription•Inhibition of KMT2D methylation sensitizes cells and tumors to PI3K/AKT inhibition
Blawski et al. show that KMT2D is methylated by the lysine methyltransferase SMYD2 at K1330. SMYD2 loss attenuates PI3K inhibitor-induced KMT2D chromatin binding at estrogen-receptor (ER) loci and ER-dependent transcription. SMYD2 inhibition sensitizes cells, patient-derived organoids, and tumors to PI3K/AKT inhibition and endocrine therapy through KMT2D K1330 methylation.
In recent years, melanoma research has undergone a renaissance. What was once viewed, at least in the metastatic setting, as an intractable and untreatable disease is now revealing its molecular ...weaknesses. 2011 was a landmark year for melanoma therapy, with two new agents, the anti-CTLA4 antibody ipilimumab and the BRAF inhibitor vemurafenib, shown to confer a survival benefit in randomized phase III clinical trials. Overlooked in the recent flurry of interest that has accompanied the development of these drugs, melanoma is in fact an ancient disease that has long frustrated attempts at therapeutic interventions. In this article, we trace the history of melanoma: from the earliest known cases of melanoma in pre-Colombian South America, through the explorations of the Victorian anatomists right up to the molecular biology revolution of the 20th century that allowed for the identification of the key driving events required for melanomagenesis. We further outline how observations about melanoma heterogeneity, first made over 190 years ago, continue to drive our efforts to reduce melanoma to the level of a chronic, manageable disease and ultimately to cure it entirely.
Metastatic melanoma is challenging to clinically address. Although standard-of-care targeted therapy has high response rates in patients with BRAF-mutant melanoma, therapy relapse occurs in most ...cases. Intrinsically resistant melanoma cells drive therapy resistance and display molecular and biologic properties akin to neural crest-like stem cells (NCLSC) including high invasiveness, plasticity, and self-renewal capacity. The shared transcriptional programs and vulnerabilities between NCLSCs and cancer cells remains poorly understood. Here, we identify a developmental LPAR1-axis critical for NCLSC viability and melanoma cell survival. LPAR1 activity increased during progression and following acquisition of therapeutic resistance. Notably, genetic inhibition of LPAR1 potentiated BRAFi ± MEKi efficacy and ablated melanoma migration and invasion. Our data define LPAR1 as a new therapeutic target in melanoma and highlights the promise of dissecting stem cell-like pathways hijacked by tumor cells. SIGNIFICANCE: This study identifies an LPAR1-axis critical for melanoma invasion and intrinsic/acquired therapy resistance.
Autophagy mediates resistance to various anticancer agents. In melanoma, resistance to targeted therapy has been linked to expression of Wnt5A, an intrinsic inhibitor of β-catenin, which also ...promotes invasion. In this study, we assessed the interplay between Wnt5A and autophagy by combining expression studies in human clinical biopsies with functional analyses in cell lines and mouse models. Melanoma cells with high Wnt5A and low β-catenin displayed increased basal autophagy. Genetic blockade of autophagy revealed an unexpected feedback loop whereby knocking down the autophagy factor ATG5 in Wnt5A
cells decreased Wnt5A and increased β-catenin. To define the physiologic relevance of this loop, melanoma cells with different Wnt status were treated
and
with the potent lysosomotropic compound Lys05. Wnt5A
cells were less sensitive to Lys05 and could be reverted by inducing β-catenin activity. Our results suggest the efficacy of autophagy inhibitors might be improved by taking the Wnt signature of melanoma cells into account.
.
Abstract Background One of major issues in clinical trials in oncology is their high failure rate, despite the fact that the trials were designed based on the data from successful equivalent ...preclinical studies. This is in part due to the intrinsic homogeneity of preclinical model systems and the contrasting heterogeneity of actual patient responses. Methods We present a mathematical model-driven framework, phase i (virtual/imaginary) trials, that integrates the heterogeneity of actual patient responses and preclinical studies through a cohort of virtual patients. The framework includes an experimentally calibrated mathematical model, a cohort of heterogeneous virtual patients, an assessment of stratification factors, and treatment optimisation. We show the detailed process through the lens of melanoma combination therapy (chemotherapy and an AKT inhibitor), using both preclinical and clinical data. Results The mathematical model predicts melanoma treatment response and resistance to mono and combination therapies and was calibrated and then validated with in vitro experimental data. The validated model and a genetic algorithm were used to generate virtual patients whose tumour volume responses to the combination therapy matched statistically the actual heterogeneous patient responses in the clinical trial. Analyses on simulated cohorts revealed key model parameters such as a tumour volume doubling rate and a therapy-induced phenotypic switch rate that may have clinical correlates. Finally, our approach predicts optimal AKT inhibitor scheduling suggesting more effective but less toxic treatment strategies. Conclusion Our proposed computational framework to implement phase i trials in cancer can readily capture observed heterogeneous clinical outcomes and predict patient survival. Importantly, phase i trials can be used to optimise future clinical trial design.
The Society for Melanoma Research (SMR) was created 20 years ago and has unequivocally contributed to the vast progress of the field, particularly for the treatment of melanoma patients with ...metastatic disease by facilitating synergistic collaborations between clinicians, researchers at the bench, and industry. In commemoration of the 20th anniversary of the first SMR International Congress (held in 2003 in Philadelphia), we look to the future by highlighting the perspectives of the next generation of rising stars, medical, and graduate students across six continents.
Lysosomal autophagy inhibitors (LAI) such as hydroxychloroquine (HCQ) have significant activity in a subset of cancer cell lines. LAIs are being evaluated in cancer clinical trials, but genetic ...determinants of sensitivity to LAIs are unknown, making it difficult to predict which tumors would be most susceptible. Here we characterize differentially expressed genes in HCQ-sensitive (-S) and -resistant (-R) cancer cells. Notably, expression of canonical macroautophagy/autophagy genes was not associated with sensitivity to HCQ. Expression patterns of ALDH1A1 (aldehyde dehydrogenase 1 family member A1) and HLTF (helicase like transcription factor) identified HCQ-S (ALDH1A1
high
HLTF
low
; ALDH1A1
low
HLTF
low
) and HCQ-R (ALDH1A1
low
HLTF
high
) cells. ALDH1A1 overexpression was found to enhance LAI cell entry and cytotoxicity without directly affecting lysosome function or autophagic flux. Expression of HLTF allows repair of DNA damage caused by LAI-induced reactive oxygen species, leading to HCQ resistance. Sensitivity to HCQ is increased in cells where HLTF is silenced by promoter methylation. HLTF overexpression blunted the antitumor efficacy of chloroquine derivatives in vitro and in vivo. Analysis of tumor RNA sequencing data from >700 patients in the Cancer Genome Atlas identified cancers including colon cancer, renal cell carcinoma, and gastric cancers, that were enriched for the HCQ-S or HCQ-R signature. These results provide mechanistic insights into LAI efficacy, and guidance for LAI clinical development.
In melanomas, therapy resistance can arise due to a combination of genetic, epigenetic and phenotypic mechanisms. Due to its crucial role in DNA supercoil relaxation, TOP1 is often considered an ...essential chemotherapeutic target in cancer. However, how TOP1 expression and activity might differ in therapy sensitive versus resistant cell types is unknown. Here we show that TOP1 expression is increased in metastatic melanoma and correlates with an invasive gene expression signature. More specifically, TOP1 expression is highest in cells with the lowest expression of MITF, a key regulator of melanoma biology. Notably, TOP1 and DNA Single-Strand Break Repair genes are downregulated in BRAFi- and BRAFi/MEKi-resistant cells and TOP1 inhibition decreases invasion markers only in BRAFi/MEKi-resistant cells. Thus, we show three different phenotypes related to TOP1 levels: i) non-malignant cells with low TOP1 levels; ii) metastatic cells with high TOP1 levels and high invasiveness; and iii) BRAFi- and BRAFi/MEKi-resistant cells with low TOP1 levels and high invasiveness. Together, these results highlight the potential role of TOP1 in melanoma progression and resistance.
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