Next-generation of melanoma researchers: Trainee perspectives from around the world.

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.

Progress in melanoma treatment: Patient's perspectives.

Upon the 20th Anniversary of the Society for Melanoma Research, we highlight the perspectives of patients aiming to help improve future experiences, outcomes, and their quality of life over the next 20 years. Five melanoma patients generously shared their inspiring and enlightening stories of diagnosis, treatment, and outcomes. Many patients had excellent medical teams that synergistically worked together to provide an accurate diagnosis, effective treatment options, and supportive care. However, it is clear that health inequities persist in communities where people of color are predominant, affecting early detection, patient experience, and outcomes. These stories shed light on the unique challenges faced by patients and how the lack of melanoma awareness and adequate resources, especially in communities of color or low socioeconomic status, can contribute to disparate outcomes in melanoma care. We expect that these stories will raise awareness about the progress in melanoma treatment but also the existent disparities in melanoma diagnosis and treatment and the importance of early detection and prevention.

Brief history of the Society for Melanoma Research: A community of clinicians, researchers, and friends.

To commemorate the 20th Anniversary of the Society of Melanoma Research and the first International Melanoma Research Congress held in June of 2003, we have described in brief, how the Society for Melanoma Research (SMR) began, the purpose, goals, and governance of the SMR, and how the society has evolved to support new melanoma researchers. In celebration of the immense progress in treating melanoma patients over the last 20 years and the impact of the SMR on these advances, we have highlighted memories and insight from early SMR members and founders.

Stromal changes in the aged lung induce an emergence from melanoma dormancy.

Disseminated cancer cells from primary tumours can seed in distal tissues, but may take several years to form overt metastases, a phenomenon that is termed tumour dormancy. Despite its importance in metastasis and residual disease, few studies have been able to successfully characterize dormancy within melanoma. Here we show that the aged lung microenvironment facilitates a permissive niche for efficient outgrowth of dormant disseminated cancer cells-in contrast to the aged skin, in which age-related changes suppress melanoma growth but drive dissemination. These microenvironmental complexities can be explained by the phenotype switching model, which argues that melanoma cells switch between a proliferative cell state and a slower-cycling, invasive state1-3. It was previously shown that dermal fibroblasts promote phenotype switching in melanoma during ageing4-8. We now identify WNT5A as an activator of dormancy in melanoma disseminated cancer cells within the lung, which initially enables the efficient dissemination and seeding of melanoma cells in metastatic niches. Age-induced reprogramming of lung fibroblasts increases their secretion of the soluble WNT antagonist sFRP1, which inhibits WNT5A in melanoma cells and thereby enables efficient metastatic outgrowth. We also identify the tyrosine kinase receptors AXL and MER as promoting a dormancy-to-reactivation axis within melanoma cells. Overall, we find that age-induced changes in distal metastatic microenvironments promote the efficient reactivation of dormant melanoma cells in the lung.

sFRP2 Supersedes VEGF as an Age-related Driver of Angiogenesis in Melanoma, Affecting Response to Anti-VEGF Therapy in Older Patients.

PURPOSE: Angiogenesis is thought to be critical for tumor metastasis. However, inhibiting angiogenesis using antibodies such as bevacizumab (Avastin), has had little impact on melanoma patient survival. We have demonstrated that both angiogenesis and metastasis are increased in older individuals, and therefore sought to investigate whether there was an age-related difference in response to bevacizumab, and if so, what the underlying mechanism could be. EXPERIMENTAL DESIGN: We analyzed data from the AVAST-M trial of 1,343 patients with melanoma treated with bevacizumab to determine whether there is an age-dependent response to bevacizumab. We also examined the age-dependent expression of VEGF and its cognate receptors in patients with melanoma, while using syngeneic melanoma animal models to target VEGF in young versus old mice. We also examined the age-related proangiogenic factor secreted frizzled-related protein 2 (sFRP2) and whether it could modulate response to anti-VEGF therapy. RESULTS: We show that older patients respond poorly to bevacizumab, whereas younger patients show improvement in both disease-free survival and overall survival. We find that targeting VEGF does not ablate angiogenesis in an aged mouse model, while sFRP2 promotes angiogenesis in vitro and in young mice. Targeting sFRP2 in aged mice successfully ablates angiogenesis, while the effects of targeting VEGF in young mice can be overcome by increasing sFRP2. CONCLUSIONS: VEGF is decreased during aging, thereby reducing response to bevacizumab. Despite the decrease in VEGF, angiogenesis is increased because of an increase in sFRP2 in the aged tumor microenvironment. These results stress the importance of considering age as a factor for designing targeted therapies.

Changes in Aged Fibroblast Lipid Metabolism Induce Age-Dependent Melanoma Cell Resistance to Targeted Therapy via the Fatty Acid Transporter FATP2.

Older patients with melanoma (>50 years old) have poorer prognoses and response rates to targeted therapy compared with young patients (<50 years old), which can be driven, in part, by the aged microenvironment. Here, we show that aged dermal fibroblasts increase the secretion of neutral lipids, especially ceramides. When melanoma cells are exposed to the aged fibroblast lipid secretome, or cocultured with aged fibroblasts, they increase the uptake of lipids via the fatty acid transporter FATP2, which is upregulated in melanoma cells in the aged microenvironment and known to play roles in lipid synthesis and accumulation. We show that blocking FATP2 in melanoma cells in an aged microenvironment inhibits their accumulation of lipids and disrupts their mitochondrial metabolism. Inhibiting FATP2 overcomes age-related resistance to BRAF/MEK inhibition in animal models, ablates tumor relapse, and significantly extends survival time in older animals. SIGNIFICANCE: These data show that melanoma cells take up lipids from aged fibroblasts, via FATP2, and use them to resist targeted therapy. The response to targeted therapy is altered in aged individuals because of the influences of the aged microenvironment, and these data suggest FATP2 as a target to overcome resistance.See related commentary by Montal and White, p. 1255.This article is highlighted in the In This Issue feature, p. 1241.

Paradoxical Role for Wild-Type p53 in Driving Therapy Resistance in Melanoma.

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.

Age-Related Changes in HAPLN1 Increase Lymphatic Permeability and Affect Routes of Melanoma Metastasis.

Older patients with melanoma have lower rates of sentinel lymph node (LN) metastases yet paradoxically have inferior survival. Patient age correlated with an inability to retain Technetium radiotracer during sentinel LN biopsy in more than 1,000 patients, and high Technetium counts correlated to better survival. We hypothesized that loss of integrity in the lymphatic vasculature due to extracellular matrix (ECM) degradation might play a role. We have implicated HAPLN1 in age-dependent ECM degradation in the dermis. Here, we queried whether HAPLN1 could be altered in the lymphatic ECM. Lymphatic HAPLN1 expression was prognostic of long-term patient survival. Adding recombinant HAPLN1 to aged fibroblast ECMs in vitro reduced endothelial permeability via modulation of VE-cadherin junctions, whereas endothelial permeability was increased following HAPLN1 knockdown in young fibroblasts. In vivo, reconstitution of HAPLN1 in aged mice increased the number of LN metastases, but reduced visceral metastases. These data suggest that age-related changes in ECM can contribute to impaired lymphatics. SIGNIFICANCE: Our studies reveal that changes in the stroma during aging may influence the way tumor cells traffic through the lymphatic vasculature. Aging may dictate the route of metastatic dissemination of tumor cells, and understanding these changes may help to reveal targetable moieties in the aging tumor microenvironment.See related commentary by Marie and Merlino, p. 19.This article is highlighted in the In This Issue feature, p. 1.

Remodeling of the Collagen Matrix in Aging Skin Promotes Melanoma Metastasis and Affects Immune Cell Motility.

Physical changes in skin are among the most visible signs of aging. We found that young dermal fibroblasts secrete high levels of extracellular matrix (ECM) constituents, including proteoglycans, glycoproteins, and cartilage-linking proteins. The most abundantly secreted was HAPLN1, a hyaluronic and proteoglycan link protein. HAPLN1 was lost in aged fibroblasts, resulting in a more aligned ECM that promoted metastasis of melanoma cells. Reconstituting HAPLN1 inhibited metastasis in an aged microenvironment, in 3-D skin reconstruction models, and in vivo. Intriguingly, aged fibroblast-derived matrices had the opposite effect on the migration of T cells, inhibiting their motility. HAPLN1 treatment of aged fibroblasts restored motility of mononuclear immune cells, while impeding that of polymorphonuclear immune cells, which in turn affected regulatory T-cell recruitment. These data suggest that although age-related physical changes in the ECM can promote tumor cell motility, they may adversely affect the motility of some immune cells, resulting in an overall change in the immune microenvironment. Understanding the physical changes in aging skin may provide avenues for more effective therapy for older patients with melanoma. SIGNIFICANCE: These data shed light on the mechanochemical interactions that occur between aged skin, tumor, and immune cell populations, which may affect tumor metastasis and immune cell infiltration, with implications for the efficacy of current therapies for melanoma.See related commentary by Marie and Merlino, p. 19.This article is highlighted in the In This Issue feature, p. 1.

Age Correlates with Response to Anti-PD1, Reflecting Age-Related Differences in Intratumoral Effector and Regulatory T-Cell Populations.

Purpose: We have shown that the aged microenvironment increases melanoma metastasis, and decreases response to targeted therapy, and here we queried response to anti-PD1.Experimental Design: We analyzed the relationship between age, response to anti-PD1, and prior therapy in 538 patients. We used mouse models of melanoma, to analyze the intratumoral immune microenvironment in young versus aged mice and confirmed our findings in human melanoma biopsies.Results: Patients over the age of 60 responded more efficiently to anti-PD-1, and likelihood of response to anti-PD-1 increased with age, even when we controlled for prior MAPKi therapy. Placing genetically identical tumors in aged mice (52 weeks) significantly increased their response to anti-PD1 as compared with the same tumors in young mice (8 weeks). These data suggest that this increased response in aged patients occurs even in the absence of a more complex mutational landscape. Next, we found that young mice had a significantly higher population of regulatory T cells (Tregs), skewing the CD8+:Treg ratio. FOXP3 staining of human melanoma biopsies revealed similar increases in Tregs in young patients. Depletion of Tregs using anti-CD25 increased the response to anti-PD1 in young mice.Conclusions: While there are obvious limitations to our study, including our inability to conduct a meta-analysis due to a lack of available data, and our inability to control for mutational burden, there is a remarkable consistency in these data from over 500 patients across 8 different institutes worldwide. These results stress the importance of considering age as a factor for immunotherapy response. Clin Cancer Res; 24(21); 5347-56. ©2018 AACR See related commentary by Pawelec, p. 5193.

ATG5 Mediates a Positive Feedback Loop between Wnt Signaling and Autophagy in Melanoma.

Autophagy mediates resistance to various anticancer agents. In melanoma, resistance to targeted therapy has been linked to expression of Wnt5A, an intrinsic inhibitor of ß-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 ß-catenin displayed increased basal autophagy. Genetic blockade of autophagy revealed an unexpected feedback loop whereby knocking down the autophagy factor ATG5 in Wnt5Ahigh cells decreased Wnt5A and increased ß-catenin. To define the physiologic relevance of this loop, melanoma cells with different Wnt status were treated in vitro and in vivo with the potent lysosomotropic compound Lys05. Wnt5Ahigh cells were less sensitive to Lys05 and could be reverted by inducing ß-catenin activity. Our results suggest the efficacy of autophagy inhibitors might be improved by taking the Wnt signature of melanoma cells into account. Cancer Res; 77(21); 5873-85. ©2017 AACR.

Modeling the two-way feedback between contractility and matrix realignment reveals a nonlinear mode of cancer cell invasion.

Cancer cell invasion from primary tumors is mediated by a complex interplay between cellular adhesions, actomyosin-driven contractility, and the physical characteristics of the extracellular matrix (ECM). Here, we incorporate a mechanochemical free-energy-based approach to elucidate how the two-way feedback loop between cell contractility (induced by the activity of chemomechanical interactions such as Ca2+ and Rho signaling pathways) and matrix fiber realignment and strain stiffening enables the cells to polarize and develop contractile forces to break free from the tumor spheroids and invade into the ECM. Interestingly, through this computational model, we are able to identify a critical stiffness that is required by the matrix to break intercellular adhesions and initiate cell invasion. Also, by considering the kinetics of the cell movement, our model predicts a biphasic invasiveness with respect to the stiffness of the matrix. These predictions are validated by analyzing the invasion of melanoma cells in collagen matrices of varying concentration. Our model also predicts a positive correlation between the elongated morphology of the invading cells and the alignment of fibers in the matrix, suggesting that cell polarization is directly proportional to the stiffness and alignment of the matrix. In contrast, cells in nonfibrous matrices are found to be rounded and not polarized, underscoring the key role played by the nonlinear mechanics of fibrous matrices. Importantly, our model shows that mechanical principles mediated by the contractility of the cells and the nonlinearity of the ECM behavior play a crucial role in determining the phenotype of the cell invasion.

Inhibition of Age-Related Therapy Resistance in Melanoma by Rosiglitazone-Mediated Induction of Klotho.

Purpose: Aging is a poor prognostic factor for melanoma. We have shown that melanoma cells in an aged microenvironment are more resistant to targeted therapy than identical cells in a young microenvironment. This is dependent on age-related secreted factors. Klotho is an age-related protein whose serum levels decrease dramatically by age 40. Most studies on klotho in cancer have focused on the expression of klotho in the tumor cell. We have shown that exogenous klotho inhibits internalization and signaling of Wnt5A, which drives melanoma metastasis and resistance to targeted therapy. We investigate here whether increasing klotho in the aged microenvironment could be an effective strategy for the treatment of melanoma.Experimental Design: PPARγ increases klotho levels and is increased by glitazones. Using rosiglitazone, we queried the effects of rosiglitazone on Klotho/Wnt5A cross-talk, in vitro and in vivo, and the implications of that for targeted therapy in young versus aged animals.Results: We show that rosiglitazone increases klotho and decreases Wnt5A in tumor cells, reducing the burden of both BRAF inhibitor-sensitive and BRAF inhibitor-resistant tumors in aged, but not young mice. However, when used in combination with PLX4720, tumor burden was reduced in both young and aged mice, even in resistant tumors.Conclusions: Using glitazones as adjuvant therapy for melanoma may provide a new treatment strategy for older melanoma patients who have developed resistance to vemurafenib. As klotho has been shown to play a role in other cancers too, our results may have wide relevance for multiple tumor types. Clin Cancer Res; 23(12); 3181-90. ©2017 AACR.

In the Wnt-er of life: Wnt signalling in melanoma and ageing.

Although the clinical landscape of melanoma is improving rapidly, metastatic melanoma remains a deadly disease. Age remains one of the greatest risk factors for melanoma, and patients older than 55 have a much poorer prognosis than younger individuals, even when the data are controlled for grade and stage. The reasons for this disparity have not been fully uncovered, but there is some recent evidence that Wnt signalling may have a role. Wnt signalling is known to have roles both in cancer progression as well as in organismal ageing. In melanoma, the interplay of Wnt signalling pathways is complex, with different members of the Wnt family guiding different aspects of invasion and proliferation. Here, we will briefly review the current literature addressing the roles of different Wnt pathways in melanoma pathogenesis, provide an overview of Wnt signalling during ageing, and discuss the intersection between melanoma and ageing in terms of Wnt signalling.

sFRP2 in the aged microenvironment drives melanoma metastasis and therapy resistance.

Cancer is a disease of ageing. Clinically, aged cancer patients tend to have a poorer prognosis than young. This may be due to accumulated cellular damage, decreases in adaptive immunity, and chronic inflammation. However, the effects of the aged microenvironment on tumour progression have been largely unexplored. Since dermal fibroblasts can have profound impacts on melanoma progression, we examined whether age-related changes in dermal fibroblasts could drive melanoma metastasis and response to targeted therapy. Here we find that aged fibroblasts secrete a Wnt antagonist, sFRP2, which activates a multi-step signalling cascade in melanoma cells that results in a decrease in ß-catenin and microphthalmia-associated transcription factor (MITF), and ultimately the loss of a key redox effector, APE1. Loss of APE1 attenuates the response of melanoma cells to DNA damage induced by reactive oxygen species, rendering the cells more resistant to targeted therapy (vemurafenib). Age-related increases in sFRP2 also augment both angiogenesis and metastasis of melanoma cells. These data provide an integrated view of how fibroblasts in the aged microenvironment contribute to tumour progression, offering new possibilities for the design of therapy for the elderly.

HSP70 Inhibition Limits FAK-Dependent Invasion and Enhances the Response to Melanoma Treatment with BRAF Inhibitors.

The stress-inducible chaperone protein HSP70 (HSPA1) is implicated in melanoma development, and HSP70 inhibitors exert tumor-specific cytotoxic activity in cancer. In this study, we documented that a significant proportion of melanoma tumors express high levels of HSP70, particularly at advanced stages, and that phospho-FAK (PTK2) and BRAF are HSP70 client proteins. Treatment of melanoma cells with HSP70 inhibitors decreased levels of phospho-FAK along with impaired migration, invasion, and metastasis in vitro and in vivo Moreover, the HSP70 inhibitor PET-16 reduced levels of mutant BRAF, synergized with the BRAF inhibitor PLX4032 in vitro, and enhanced the durability of response to BRAF inhibition in vivo Collectively, these findings provide strong support for HSP70 inhibition as a therapeutic strategy in melanoma, especially as an adjuvant approach for overcoming the resistance to BRAF inhibitors frequently observed in melanoma patients. Cancer Res; 76(9); 2720-30. ©2016 AACR.