Certain transcription factors have vital roles in lineage development, including specification of cell types and control of differentiation. Microphthalmia-associated transcription factor (MITF) is a ...key transcription factor for melanocyte development and differentiation. MITF regulates expression of numerous pigmentation genes to promote melanocyte differentiation, as well as fundamental genes for maintaining cell homeostasis, including genes encoding proteins involved in apoptosis (eg, BCL2) and the cell cycle (eg, CDK2). Loss-of-function mutations of MITF cause Waardenburg syndrome type IIA, whose phenotypes include depigmentation due to melanocyte loss, whereas amplification or specific mutation of MITF can be an oncogenic event that is seen in a subset of familial or sporadic melanomas. In this article, we review basic features of MITF biological function and highlight key unresolved questions regarding this remarkable transcription factor.
The melanoma field has seen an unprecedented set of clinical advances over the past decade. Therapeutic efficacy for advanced or metastatic melanoma went from being one of the most poorly responsive ...to one of the more responsive. Perhaps most strikingly, the advances that transformed management of the disease are based upon modern mechanism-based therapeutic strategies. The targeted approaches that primarily suppress the BRAF oncoprotein pathway have a high predictability of efficacy although less optimal depth or durability of response. Immunotherapy is primarily based on blockade of one or two immune checkpoints and has a lower predictability of response but higher fractions of durable remissions. This article reviews the clinical progress in management of advanced melanoma and also discusses the impact of the same therapies on earlier stage disease, where the agents have shown significant promise in treating resectable but high-risk clinical scenarios. Collectively, the progress in melanoma therapeutics has transformed the standard of care for patients, informed new approaches that are increasingly utilized for treatment of other malignancies, and suggest novel strategies to further boost efficacy for the many patients not yet receiving optimal benefit from these approaches.
Melanoma, the deadliest form of skin cancer, is an aggressive disease that is rising in incidence. Although melanoma is a historically treatment-resistant malignancy, in recent years unprecedented ...breakthroughs in targeted therapies and immunotherapies have revolutionized the standard of care for patients with advanced disease. Here, we provide an overview of recent developments in our understanding of melanoma risk factors, genomics, and molecular pathogenesis and how these insights have driven advances in melanoma treatment. In addition, we review benefits and limitations of current therapies and look ahead to continued progress in melanoma prevention and therapy. Remarkable achievements in the field have already produced a paradigm shift in melanoma treatment: Metastatic melanoma, once considered incurable, can now be treated with potentially curative rather than palliative intent.
Ultraviolet radiation (UVR) has numerous effects on skin, including DNA damage, tanning, vitamin D synthesis, carcinogenesis, and immunomodulation. Keratinocytes containing damaged DNA secrete both ...α‐melanocyte‐stimulating hormone (α‐MSH), which stimulates pigment production by melanocytes, and the opioid β‐endorphin, which can trigger addiction‐like responses to UVR. The pigmentation (tanning) response is an adaptation that provides some delayed protection against further DNA damage and carcinogenesis, while the opioid response may be an evolutionary adaptation for promoting sun‐seeking behavior to prevent vitamin D deficiency. Here, we review the pigmentation response to UVR, driven by melanocytic microphthalmia‐associated transcription factor (MITF), and evidence for UVR‐induced melanomagenesis and addiction. We also discuss potential applications of a novel approach to generate protective pigmentation in the absence of UVR (sunless tanning) using a topical small‐molecule inhibitor of the salt‐inducible kinase (SIK) family.
Group size is an important trait for many ecological and evolutionary processes. However, it is not a trait possessed by individuals but by social groups, and as many genomes contribute to group size ...understanding its genetic underpinnings and so predicting its evolution is a conceptual challenge. Here I suggest how group size can be modelled as a joint phenotype of multiple individuals, and so how models for evolution accounting for indirect genetic effects are essential for understanding the genetic variance of group size. This approach makes it clear that (a) group size should have a larger genetic variance than initially expected as indirect genetic effects always contribute exactly as much as direct genetic effects and (b) the response to selection of group size should be faster than expected based on direct genetic variance alone as the correlation between direct and indirect effects is always at the maximum positive limit of 1. Group size should therefore show relatively rapid evolved increases and decreases, the consequences of which and evidence for I discuss.
The decision to leave or join a group is important as group size influences many aspects of organisms' lives and their fitness. This tendency to socialise with others, sociability, should be ...influenced by genes carried by focal individuals (direct genetic effects) and by genes in partner individuals (indirect genetic effects), indicating the trait's evolution could be slower or faster than expected. However, estimating these genetic parameters is difficult. Here, in a laboratory population of the cockroach Blaptica dubia, I estimate phenotypic parameters for sociability: repeatability (R) and repeatable influence (RI), that indicate whether direct and indirect genetic effects respectively are likely. I also estimate the interaction coefficient (Ψ), which quantifies how strongly a partner's trait influences the phenotype of the focal individual and is key in models for the evolution of interacting phenotypes. Focal individuals were somewhat repeatable for sociability across a 3‐week period (R = 0.080), and partners also had marginally consistent effects on focal sociability (RI = 0.053). The interaction coefficient was non‐zero, although in opposite sign for the sexes; males preferred to associate with larger individuals (Ψmale = −0.129), while females preferred to associate with smaller individuals (Ψfemale = 0.071). Individual sociability was consistent between dyadic trials and in social networks of groups. These results provide phenotypic evidence that direct and indirect genetic effects have limited influence on sociability, with perhaps most evolutionary potential stemming from heritable effects of the body mass of partners. Sex‐specific interaction coefficients may produce sexual conflict and the evolution of sexual dimorphism in social behaviour.
A graphical summarising the results of the article.
Precision medicine is about matching the right drugs to the right patients. Although this approach is technology agnostic, in cancer there is a tendency to make precision medicine synonymous with ...genomics. However, genome-based cancer therapeutic matching is limited by incomplete biological understanding of the relationship between phenotype and cancer genotype. This limitation can be addressed by functional testing of live patient tumour cells exposed to potential therapies. Recently, several 'next-generation' functional diagnostic technologies have been reported, including novel methods for tumour manipulation, molecularly precise assays of tumour responses and device-based in situ approaches; these address the limitations of the older generation of chemosensitivity tests. The promise of these new technologies suggests a future diagnostic strategy that integrates functional testing with next-generation sequencing and immunoprofiling to precisely match combination therapies to individual cancer patients.
In the light of substantial discoveries in epithelial and hair pigmentation pathophysiology, this review summarizes the current understanding of skin pigmentation mechanisms. Melanocytes are ...pigment‐producing cells, and their key regulating transcription factor is the melanocyte‐specific microphthalmia‐associated transcription factor (m‐MITF). Ultraviolet (UV) radiation is a unique modulator of skin pigmentation influencing tanning pathways. The delayed tanning pathway occurs as UVB produces keratinocyte DNA damage, causing p53‐mediated expression of the pro‐opiomelanocortin (POMC) gene that is processed to release α‐melanocyte‐stimulating hormone (α‐MSH). α‐MSH stimulates the melanocortin 1 receptor (MC1R) on melanocytes, leading to m‐MITF expression and melanogenesis. POMC cleavage also releases β‐endorphin, which creates a neuroendocrine pathway that promotes UV‐seeking behaviours. Mutations along the tanning pathway can affect pigmentation and increase the risk of skin malignancies. MC1R variants have received considerable attention, yet the allele is highly polymorphic with varied phenotypes. Vitiligo presents with depigmented skin lesions due to autoimmune destruction of melanocytes. UVB phototherapy stimulates melanocyte stem cells in the hair bulge to undergo differentiation and upwards migration resulting in perifollicular repigmentation of vitiliginous lesions, which is under sophisticated signalling control. Melanocyte stem cells, normally quiescent, undergo cyclic activation/differentiation and downward migration with the hair cycle, providing pigment to hair follicles. Physiological hair greying results from progressive loss of melanocyte stem cells and can be accelerated by acute stress‐induced, sympathetic driven hyperproliferation of the melanocyte stem cells. Ultimately, by reviewing the pathways governing epithelial and follicular pigmentation, numerous areas of future research and potential points of intervention are highlighted.
Melanoma: from mutations to medicine Tsao, Hensin; Chin, Lynda; Garraway, Levi A ...
Genes & development,
2012-Jun-01, 2012-06-01, 20120601, Letnik:
26, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Melanoma is often considered one of the most aggressive and treatment-resistant human cancers. It is a disease that, due to the presence of melanin pigment, was accurately diagnosed earlier than most ...other malignancies and that has been subjected to countless therapeutic strategies. Aside from early surgical resection, no therapeutic modality has been found to afford a high likelihood of curative outcome. However, discoveries reported in recent years have revealed a near avalanche of breakthroughs in the melanoma field-breakthroughs that span fundamental understanding of the molecular basis of the disease all the way to new therapeutic strategies that produce unquestionable clinical benefit. These discoveries have been born from the successful fruits of numerous researchers working in many-sometimes-related, although also distinct-biomedical disciplines. Discoveries of frequent mutations involving BRAF(V600E), developmental and oncogenic roles for the microphthalmia-associated transcription factor (MITF) pathway, clinical efficacy of BRAF-targeted small molecules, and emerging mechanisms underlying resistance to targeted therapeutics represent just a sample of the findings that have created a striking inflection in the quest for clinically meaningful progress in the melanoma field.
Despite compelling rates of durable clinical responses to programmed cell death-1 (PD-1) blockade, advances are needed to extend these benefits to resistant tumors. We found that tumor-bearing mice ...deficient in the chemokine receptor CXCR3 responded poorly to anti-PD-1 treatment. CXCR3 and its ligand CXCL9 were critical for a productive CD8+ T cell response in tumor-bearing mice treated with anti-PD-1 but were not required for the infiltration of CD8+ T cells into tumors. The anti-PD-1-induced anti-tumor response was facilitated by CXCL9 production from intratumoral CD103+ dendritic cells, suggesting that CXCR3 facilitates dendritic cell-T cell interactions within the tumor microenvironment. CXCR3 ligands in murine tumors and in plasma of melanoma patients were an indicator of clinical response to anti-PD-1, and their induction in non-responsive murine tumors promoted responsiveness to anti-PD-1. Our data suggest that the CXCR3 chemokine system is a biomarker for sensitivity to PD-1 blockade and that augmenting the intratumoral function of this chemokine system could improve clinical outcomes.
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•Anti-PD-1 efficacy depends on intratumoral activity of the CXCR3 chemokine system•CD103+ dendritic-cell-derived CXCL9 and CXCR3 on CD8+ T cells are required•CXCR3 ligands are positive indicators of responsiveness to anti-PD-1 therapy•Inducing CXCR3 ligands in non-responsive tumors restores sensitivity to anti-PD-1
Chow et al. find the CXCR3 chemokine system is not required for CD8+ T cell migration into the tumor, but rather for the enhancement of the intratumoral CD8+ T cell response in the context of PD-1 blockade. The CXCR3 chemokine system might serve as a biomarker for sensitivity to PD-1 blockade and a target for improving clinical outcomes.
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