A unique gender difference in early onset melanoma implies that in addition to ultraviolet light exposure other causative factors are important

Using US SEER17 Registry data, age‐specific melanoma incidence rates were calculated and comparisons were made between males and females. Relative Risk (RR) for males and females in each age group was computed and compared with that from Nordic Cancer Registry data set and to that for non‐melanoma skin cancer (NMSC). For age groups 44 and younger, females showed higher incidence rates, with a peak difference at age 20–24 (RR = 2.01, 95% CI = 1.21–3.33). Males exhibited higher incidence rates after age 44. The same bimodal gender difference was confirmed by the Nordic Cancer Registry data set, but it was not observed for NMSC, which is known to be strongly associated with cumulative exposure to solar UV radiation. We conclude that exposure to solar ultraviolet (UV) radiation is the major causative factor for melanoma at older age (>44 yr), but that other factors may play a role in early onset melanomas, particularly in females.     

Inhibition of melanoma development in the Nras(Q61K)::Ink4a−/− mouse model by the small molecule BI‐69A11

To date, there are no effective therapies for tumors bearing NRAS mutations, which are present in 15–20% of human melanomas. Here we extend our earlier studies where we demonstrated that the small molecule BI‐69A11 inhibits the growth of melanoma cell lines. Gene expression analysis revealed the induction of interferon‐ and cell death‐related genes that were associated with responsiveness of melanoma cell lines to BI‐69A11. Strikingly, the administration of BI‐69A11 inhibited melanoma development in genetically modified mice bearing an inducible form of activated Nras and a deletion of the Ink4a gene (Nras^(Q61K)::Ink4a^?/?). Biweekly administration of BI‐69A11 starting at 10 weeks or as late as 24 weeks after the induction of mutant Nras expression inhibited melanoma development (100 and 36%, respectively). BI‐69A11 treatment did not inhibit the development of histiocytic sarcomas, which constitute about 50% of the tumors in this model. BI‐69A11‐resistant Nras^(Q61K)::Ink4a^?/? tumors exhibited increased CD45 expression, reflective of immune cell infiltration and upregulation of gene networks associated with the cytoskeleton, DNA damage response, and small molecule transport. The ability to attenuate the development of NRAS mutant melanomas supports further development of BI‐69A11 for clinical assessment.     

Emerging molecular targets in melanoma invasion and metastasis

Metastatic cutaneous melanoma accounts for the majority of skin cancer deaths due to its aggressiveness and high resistance to current therapies. To efficiently metastasize, invasive melanoma cells need to change their cytoskeletal organization and alter contacts with the extracellular matrix and the surrounding stromal cells. Melanoma cells can use different migratory strategies depending on varying environments to exit the primary tumour mass and invade surrounding and later distant tissues. In this review, we have focused on tumour cell plasticity or the interconvertibility that melanoma cells have as one of the factors that contribute to melanoma metastasis. This has been an area of very intense research in the last 5 yr yielding a vast number of findings. We have therefore reviewed all the possible clinical opportunities that this new knowledge offers to both stratify and treat cutaneous malignant melanoma patients.     

Metastatic risk and resistance to BRAF inhibitors in melanoma defined by selective allelic loss of ATG5

Melanoma is a paradigm of aggressive tumors with a complex and heterogeneous genetic background. Still, melanoma cells frequently retain developmental traits that trace back to lineage specification programs. In particular, lysosome-associated vesicular trafficking is emerging as a melanoma-enriched lineage dependency. However, the contribution of other lysosomal functions such as autophagy to melanoma progression is unclear, particularly in the context of metastasis and resistance to targeted therapy. Here we mined a broad spectrum of cancers for a meta-analysis of mRNA expression, copy number variation and prognostic value of 13 core autophagy genes. This strategy identified heterozygous loss of ATG5 at chromosome band 6q21 as a distinctive feature of advanced melanomas. Importantly, partial ATG5 loss predicted poor overall patient survival in a manner not shared by other autophagy factors and not recapitulated in other tumor types. This prognostic relevance of ATG5 copy number was not evident for other 6q21 neighboring genes. Melanocyte-specific mouse models confirmed that heterozygous (but not homozygous) deletion of Atg5 enhanced melanoma metastasis and compromised the response to targeted therapy (exemplified by dabrafenib, a BRAF inhibitor in clinical use). Collectively, our results support ATG5 as a therapeutically relevant dose-dependent rheostat of melanoma progression. Moreover, these data have important translational implications in drug design, as partial blockade of autophagy genes may worsen (instead of counteracting) the malignant behavior of metastatic melanomas.     

Autophagy modulator plays a part in UV protection

Ultraviolet (UV)-induced DNA damage is a major risk factor for skin cancers including melanoma. UVRAG, originally identified to complement UV sensitivity in xeroderma pigmentosum (XP), has since been implicated in modulating macroautophagy/autophagy, in coordinating different intracellular trafficking pathways, and in maintaining chromosomal stability. Intriguingly, our recent study has demonstrated that UVRAG plays an essential role in protecting cells from UV-induced DNA damage by activating the nucleotide excision repair (NER) pathway. Since NER is the major mechanism by which cells maintain DNA integrity against UV insult, the inactivation of UVRAG seen in some melanoma may impart these cells with an ability to accumulate high-load UV mutagenesis, leading to cancer progression. Thus, this property of UVRAG has untapped potential to be of fundamental importance in understanding the genetics and pathogenesis of human skin cancer.     

The extent of whole‐genome copy number alterations predicts aggressive features in primary melanomas

Recent evidence indicates that melanoma comprises distinct types of tumors and suggests that specific morphological features may help predict its clinical behavior. Using a SNP‐array approach, we quantified chromosomal copy number alterations (CNA) across the whole genome in 41 primary melanomas and found a high degree of heterogeneity in their genomic asset. Association analysis correlating the number and relative length of CNA with clinical, morphological, and dermoscopic attributes of melanoma revealed that features of aggressiveness were strongly linked to the overall amount of genomic damage. Furthermore, we observed that melanoma progression and survival were mainly affected by a low number of large chromosome losses and a high number of small gains. We identified the alterations most frequently associated with aggressive melanoma, and by integrating our data with publicly available gene expression profiles, we identified five genes which expression was found to be necessary for melanoma cells proliferation. In conclusion, this work provides new evidence that the phenotypic heterogeneity of melanoma reflects a parallel genetic diversity and lays the basis to define novel strategies for a more precise prognostic stratification of patients.     

The YUMM lines: a series of congenic mouse melanoma cell lines with defined genetic alterations

The remarkable success of immune therapies emphasizes the need for immune‐competent cancer models. Elegant genetically engineered mouse models of a variety of cancers have been established, but their effective use is limited by cost and difficulties in rapidly generating experimental data. Some mouse cancer cell lines are transplantable to immunocompetent host mice and have been utilized extensively to study cancer immunology. Here, we describe the Yale University Mouse Melanoma (YUMM) lines, a comprehensive system of mouse melanoma cell lines that are syngeneic to C57BL/6, have well‐defined human‐relevant driver mutations, and are genomically stable. This will be a useful tool for the study of tumor immunology and genotype‐specific cancer biology.     

Analysis of monosomy‐3 in immunomagnetically isolated circulating melanoma cells in uveal melanoma patients

Monosomy‐3 in primary uveal melanoma (UM) is associated with a high risk of metastasis and mortality. Although circulating melanoma cells (CMC) can be found in most UM patients, only approximately 50% of the patients develop metastases. We utilized a novel immuno‐FISH assay to detect chromosome‐3 in intact CMC isolated by dual immunomagnetic enrichment. Circulating melanoma cells were detected in 91% of the patients (n = 44) with primary non‐metastatic UM, of which 58% were positive for monosomy‐3. The monosomy‐3 status of CMC corresponded to the monosomy‐3 status of the primary tumor in 10 of the 11 patients where this could be tested. Monosomy‐3 in the CMC was associated with an advanced tumor stage (P = 0.046) and was detected in all four patients who developed metastasis within the follow‐up period of 4 yr. This non‐invasive technique may enable the identification of UM patients at risk for metastasis particularly when a primary tumor specimen is unavailable.     

TGF‐β induces SOX2 expression in a time‐dependent manner in human melanoma cells

The sry‐related high‐mobility box (SOX)‐2 protein has recently been proven to play a significant role in progression, metastasis, and clinical prognosis spanning several cancer types. Research on the role of SOX2 in melanoma is limited and currently little is known about the mechanistic function of this gene in this context. Here, we observed high expression of SOX2 in both human melanoma cell lines and primary melanomas in contrast to melanocytic nevi. This overexpression in melanoma can, in part, be explained by extra gene copy numbers of SOX2 in primary samples. Interestingly, we were able to induce SOX2 expression, mediated by SOX4, via TGF‐β1 stimulation in a time‐dependent manner. Moreover, the knockdown of SOX2 impaired TGF‐β‐induced invasiveness. This phenotype switch can be explained by SOX2‐mediated cross talk between TGF‐β and non‐canonical Wnt signaling. Thus, we propose that SOX2 is involved in the critical TGF‐β signaling pathway, which has been shown to correlate with melanoma aggressiveness and metastasis. In conclusion, we have identified a novel downstream factor of TGF‐β signaling in melanoma, which may have further implications in the clinic.     

Enhancing the evaluation of PI3K inhibitors through 3D melanoma models

Targeted therapies for mutant BRAF metastatic melanoma are effective but not curative due to acquisition of resistance. PI3K signaling is a common mediator of therapy resistance in melanoma; thus, the need for effective PI3K inhibitors is critical. However, testing PI3K inhibitors in adherent cultures is not always reflective of their potential in vivo. To emphasize this, we compared PI3K inhibitors of different specificity in two‐ and three‐dimensional (2D, 3D) melanoma models and show that drug response predictions gain from evaluation using 3D models. Our results in 3D demonstrate the anti‐invasive potential of PI3K inhibitors and that drugs such as PX‐866 have beneficial activity in physiological models alone and when combined with BRAF inhibition. These assays finally help highlight pathway effectors that could be involved in drug response in different environments (e.g. p4E‐BP1). Our findings show the advantages of 3D melanoma models to enhance our understanding of PI3K inhibitors.