RANK is expressed in metastatic melanoma and highly upregulated on melanoma-initiating cells. J Invest Dermatol. 2011;131:944-955. [PMID: 21270824 DOI: 10.1038/jid.2010.377]

The RANKL inhibitor denosumab in combination with dual checkpoint inhibition is associated with increased CXCL-13 serum concentrations

BACKGROUND

Recent evidence suggests additional immunomodulatory properties of RANKL inhibition possibly boosting the clinical efficacy of immune checkpoint inhibitors (ICI).

METHODS

We conducted a prospective, multicentre clinical trial in unresectable stage IV melanoma patients with bone metastases who received denosumab in parallel with dual ICI (BONEMET) and performed comprehensive immune monitoring at baseline and 4, 12, and 24 weeks after initiation of therapy. Secondary endpoints included tolerability and efficacy. For comparison, biospecimens from melanoma patients treated with dual ICI without denosumab were analyzed accordingly and served as retrospective reference cohort.

RESULTS

In both the BONEMET (n = 16) and the reference cohort (n = 18) serum levels of 17 cytokines, including IFNγ were significantly increased after 4 weeks of treatment. Patients who received ICI and denosumab showed a significantly higher increase in serum CXCL-13 and a significant decrease in VEGFc compared with the reference cohort. While no changes in T cell composition were observed at 4 weeks, patients in the BONEMET cohort showed a significant decrease in the peripheral naïve T-cell population and an increase in CD8+ effector cells after 12 weeks. Treatment-related adverse events occurred with comparable frequency (93.8% in the BONEMET cohort versus 83.3% in the reference cohort). 7/16 patients in the BONEMET cohort and 8/18 patients in the reference cohort achieved disease control.

CONCLUSION

Denosumab in combination with dual ICI modulates cytokine expression and T-cell composition in peripheral blood. The upregulation of CXCL-13, a key factor for initiating tertiary lymphoid structures, strengthens the hypothesis that denosumab indeed boost immunological effects.

Management of metastatic bone disease of melanoma

One of the most aggressive tumors arising from the skin, mucosa, and uvea is malignant melanoma, which easily metastasizes. Bone tissue is one of the most typical locations for distant metastasis, and around 5%-20% of patients eventually acquired skeletal metastases. For decades, the incidence of bone metastases was higher, bringing greater burden on the family, society, and healthcare system owing to the progress of targeted therapy and immunotherapy, which prolonging the survival time substantially. Moreover, bone metastases result in skeletal-related events, which influence the quality of life, obviously. Appropriate intervention is therefore crucial. To obtain the optimum cost-effectiveness, existing treatment algorithm must be integrated, which is still controversial. We have aimed to throw light on current views concerning the formation, biological and clinical features, and treatment protocol of melanoma bone metastases to guide the decision-making process.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Origin and Therapies of Osteosarcoma

Simple Summary

Osteosarcoma is the most common malignant bone tumor in children, with a 5-year survival rate ranging from 70% to 20% depending on the aggressiveness of the disease. The current treatments have not evolved over the past four decades due in part to the genetic complexity of the disease and its heterogeneity. This review will summarize the current knowledge of OS origin, diagnosis and therapies.

Abstract

Osteosarcoma (OS) is the most frequent primary bone tumor, mainly affecting children and young adults. Despite therapeutic advances, the 5-year survival rate is 70% but drastically decreases to 20–30% for poor responders to therapies or for patients with metastasis. No real evolution of the survival rates has been observed for four decades, explained by poor knowledge of the origin, difficulties related to diagnosis and the lack of targeted therapies for this pediatric tumor. This review will describe a non-exhaustive overview of osteosarcoma disease from a clinical and biological point of view, describing the origin, diagnosis and therapies.

The Genetic Basis of Dormancy and Awakening in Cutaneous Metastatic Melanoma

Immune dysregulation, in combination with genetic and epigenetic alterations, induces an excessive proliferation of uncontrolled melanoma cells followed by dissemination of the tumor cells to distant sites, invading organs and creating metastasis. Although immunotherapy, checkpoint inhibitors and molecular targeted therapies have been developed as treatment options for advanced melanoma, there are specific mechanisms by which cancer cells can escape treatment. One of the main factors associated with reduced response to therapy is the ability of residual tumor cells to persist in a dormant state, without proliferation. This comprehensive review aimed at understanding the genetic basis of dormancy/awakening phenomenon in metastatic melanoma will help identify the possible therapeutical strategies that might eliminate melanoma circulating tumor cells (CTCs) or keep them in the dormant state forever, thereby repressing tumor relapse and metastatic spread.

The Interplay between Tumour Microenvironment Components in Malignant Melanoma

Malignant melanoma has shown an increasing incidence during the last two decades, exhibiting a large spectrum of locations and clinicopathological characteristics. Although current histopathological, biochemical, immunohistochemical, and molecular methods provide a deep insight into its biological behaviour and outcome, melanoma is still an unpredictable disease, with poor outcome. This review of the literature is aimed at updating the knowledge regarding melanoma’s clinicopathological and molecular hallmarks, including its heterogeneity and plasticity, involving cancer stem cells population. A special focus is given on the interplay between different cellular components and their secretion products in melanoma, considering its contribution to tumour progression, invasion, metastasis, recurrences, and resistance to classical therapy. Furthermore, the influences of the specific tumour microenvironment or “inflammasome”, its association with adipose tissue products, including the release of “extracellular vesicles”, and distinct microbiota are currently studied, considering their influences on diagnosis and prognosis. An insight into melanoma’s particular features may reveal new molecular pathways which may be exploited in order to develop innovative therapeutic approaches or tailored therapy.

Liquid Biopsy in Melanoma: Significance in Diagnostics, Prediction and Treatment Monitoring

Liquid biopsy is a common term referring to circulating tumor cells and other biomarkers, such as circulating tumor DNA (ctDNA) or extracellular vesicles. Liquid biopsy presents a range of clinical advantages, such as the low invasiveness of the blood sample collection and continuous control of the tumor progression. In addition, this approach enables the mechanisms of drug resistance to be determined in various methods of cancer treatment, including immunotherapy. However, in the case of melanoma, the application of liquid biopsy in patient stratification and therapy needs further investigation. This review attempts to collect all of the relevant and recent information about circulating melanoma cells (CMCs) related to the context of malignant melanoma and immunotherapy. Furthermore, the biology of liquid biopsy analytes, including CMCs, ctDNA, mRNA and exosomes, as well as techniques for their detection and isolation, are also described. The available data support the notion that thoughtful selection of biomarkers and technologies for their detection can contribute to the development of precision medicine by increasing the efficacy of cancer diagnostics and treatment.

RANK promotes colorectal cancer migration and invasion by activating the Ca2+-calcineurin/NFATC1-ACP5 axis

The tumor necrosis factor (TNF) receptor superfamily member 11a (TNFRSF11a, also known as RANK) was demonstrated to play an important role in tumor metastasis. However, the specific function of RANK in colorectal cancer (CRC) metastasis and the underlying mechanism are unknown. In this study, we found that RANK expression was markedly upregulated in CRC tissues compared with that in matched noncancerous tissues. Increased RANK expression correlated positively with metastasis, higher TNM stage, and worse prognosis in patients with CRC. Overexpression of RANK promoted CRC cell metastasis in vitro and in vivo, while knockdown of RANK decreased cell migration and invasion. Mechanistically, RANK overexpression significantly upregulated the expression of tartrate-resistant acid phosphatase 5 (TRAP/ACP5) in CRC cells. Silencing of ACP5 in RANK-overexpressing CRC cells attenuated RANK-induced migration and invasion, whereas overexpression of ACP5 increased the migration and invasion of RANK-silencing cells. The ACP5 expression was transcriptionally regulated by calcineurin/nuclear factor of activated T cells c1 (NFATC1) axis. The inhibition of calcineurin/NFATC1 significantly decreased ACP5 expression, and attenuated RANK-induced cell migration and invasion. Furthermore, RANK induced phospholipase C-gamma (PLCγ)-mediated inositol-1,4,5-trisphosphate receptor (IP3R) axis and stromal interaction molecule 1 (STIM1) to evoke calcium (Ca²⁺) oscillation. The RANK-mediated intracellular Ca²⁺ mobilization stimulated calcineurin to dephosphorylate NFATC1 and induce NFATC1 nuclear translocation. Both blockage of PLCγ-IP3R axis and STIM1 rescued RANK-induced NFATC1 nuclear translocation, ACP5 expression, and cell metastasis. Our study revealed the functional expression of RANK in human CRC cells and demonstrated that RANK induced the Ca²⁺-calcineurin/NFATC1-ACP5 axis in the regulation of CRC metastasis, that might be amenable to therapeutic targeting.

Minimal Residual Disease in Melanoma:molecular characterization of in transit cutaneous metastases and Circulating Melanoma Cells recognizes an expression panel potentially related to disease progression

Isolating circulating melanoma cells (CMCs) represents a powerful method to monitor minimal residual disease. We documented that MCAM/MUC18/CD146 expression is strongly associated with disease progression. ABCB5 is melanoma-stem antigen with self-renewal, proliferation, differentiation, tumorigenicity capabilities. These findings supported us to improve CMC detection, investigating MCAM/MUC18/CD146 and ABCB5 as enrichment targets in MM progression. Moreover, we decided to compare possible molecular diversity of these CMC fractions with metastatic tissue expression, collecting concomitantly cutaneous in transit metastases (CTM). We enriched CMCs from eight melanoma patients staged ≥pT1b AJCC, who developed CTMs at baseline or during follow up. We assessed a gene expression panel comprising ABCB5, the differentiation markers (Tyrosinase, MART1), angiogenic factors (VEGF, bFGF), the cell-cell adhesion molecules (MCAM/MUC18/CD146 5'-portion, Long, and Short isoforms, E-Cadherin, N-Cadherin, VE-Cadherin) and matrix-metallo-proteinases (MMP2 and MMP9) via high-sensitive RT-PCR. Preliminary findings defined three distinct sub-populations: "endothelial" CD45-CD146+CMCs, "stem" CD45-ABCB5+CMCs and a "hybrid- stem-endothelial"- CD45-MCAM+ABCB5+CMCs. The expression panel documented that - almost high expression found in CTMs - like in 73.5% of CMCs resulted positive for at least one transcript at baseline, showing gene-expression variability. Longitudinal monitoring documented shut-down of all gene-expressions in "endothelial"- and "hybrid stem-endothelial"-subsets, whilst persistency or acquisition of MCAM/MUC18/CD146, VE-CADH and MMPs was documented in disease-progression status.Conversely, a drastic expression shut-down was documented when patients achieved clinical remission. The "stem"- CMCs fraction" showed quite lower gene expression frequencies. MCAM/MUC18/CD146 and ABCB5 as melanoma-specific-targets are effective in the selection of highly primitive CMCs and highlights those putative genes associated with disease spreading progression.

Cancer stem cells, epigenetics, tumor microenvironment and future therapeutics in cutaneous malignant melanoma: a review

This review provides an overview of the current understanding of the ontogeny and biology of melanoma stem cells in cutaneous malignant melanoma. This article also summarizes and evaluates the current knowledge of the underlying epigenetic mechanisms, the regulation of melanoma progress by the tumor microenvironment as well as the therapeutic implications and applications of these novel insights, in the setting of personalized medicine. Unraveling the complex ecosystem of cutaneous malignant melanoma and the interplay between its components, aims to provide novel insights into the establishment of efficient therapeutic strategies.

Stem-Mesenchymal Signature Cell Genes Detected in Heterogeneous Circulating Melanoma Cells Correlate With Disease Stage in Melanoma Patients

During the process of metastasis, cancer cells dissociate from primary tumors, migrate to distal sites, and finally colonize, eventually leading to the formation of metastatic tumors. These cancer cells, defined circulating tumor cells (CTCs) spreading through the blood stream, may develop metastatic lesions or remain dormant. Some emerging clinical evidence supports that some tumor cells may possess metastatic properties already in the earlier stages of tumorigenesis. Because the initiation and progression of vertical growth in human melanoma is fundamental to the notion of tumor virulence and progression, we decided to immune-magnetic collect and molecularly characterize circulating melanoma cells (CMCs) from melanoma patients AJCC staged = pT1b (i.e., transition from radial to vertical phase). CMCs are phenotypically and molecularly heterogeneous, thus we performed a "home-made Liquid-Biopsy," by targeting the melanoma-associated-antigen, MCAM/MUC18/CD146, and/or the melanoma-initiating marker, ABCB5. We assessed a biomarker qualitative expression panel, contemplating the angiogenic-potential, melanoma-initiating and melanoma-differentiation drivers, cell-cell adhesion molecules, matrix-metallo-proteinases, which was performed on three enriched subpopulations from a total of 61 blood-samples from 21 melanoma patients. At first, a significant differential expression of the specific transcripts was documented between and within the CMC fractions enriched with MCAM-, ABCB5-, and both MCAM/ABCB5-coated beads, when analyzing two distinct groups: early AJCC- (stage I-II) and advanced- staged patients (stage II-IV). Moreover, in the early-AJCC staged-group, we could distinguish "endothelial," CD45-MCAM+ enriched-, "stem" S-CMCs, CD45-ABCB5+ enriched- and a third hybrid bi-phenotypic CD45-MCAM+/ABCB5+ enriched-fractions, due to three distinct gene-expression profiles. In particular, the endothelial-CMCs were characterized by positive expression of genes involved in migration and invasion, whilst the stem CMC-fraction only expressed stem and differentiation markers. The third subpopulation isolated based on concurrent MCAM and ABCB5 protein expression showed an invasive phenotype. All three distinct CMCs sub-populations, exhibited a primitive, "stem-mesenchymal" profile suggesting a highly aggressive and metastasizing phenotype. This study confirms the phenotypic and molecular heterogeneity observed in melanoma and highlights those putative genes involved in early melanoma spreading and disease progression.

Clinical Relevance of Liquid Biopsy in Melanoma and Merkel Cell Carcinoma

Melanoma and Merkel cell carcinoma are two aggressive skin malignancies with high disease-related mortality and increasing incidence rates. Currently, invasive tumor tissue biopsy is the gold standard for their diagnosis, and no reliable easily accessible biomarker is available to monitor patients with melanoma or Merkel cell carcinoma during the disease course. In these last years, liquid biopsy has emerged as a candidate approach to overcome this limit and to identify biomarkers for early cancer diagnosis, prognosis, therapeutic response prediction, and patient follow-up. Liquid biopsy is a blood-based non-invasive procedure that allows the sequential analysis of circulating tumor cells, circulating cell-free and tumor DNA, and extracellular vesicles. These innovative biosources show similar features as the primary tumor from where they originated and represent an alternative to invasive solid tumor biopsy. In this review, the biology and technical challenges linked to the detection and analysis of the different circulating candidate biomarkers for melanoma and Merkel cell carcinoma are discussed as well as their clinical relevance.

Dual-procedural separation of CTCs in cutaneous melanoma provides useful information for both molecular diagnosis and prognosis

Background:

Circulating tumor cells (CTCs) have recently emerged as a new dynamic soluble marker for several malignancies including cutaneous melanoma (CM) and are suitable for prognostic evaluations and treatment monitoring. However, to date many limitations still hamper the wide-scale application of CTCs in CM setting, including the lack of standardized methods as well as both low levels and heterogeneity of these cells.

Methods:

We developed a protocol for CTC detection in CM based on immune-magnetic sorting to deplete CD45-, CD31- or CD34-positive cells, followed by dielectrophoretic DEPArray separation according to cell morphology and immunophenotype. To this end, we explored the expression of melanoma stem cell antigens (CD271, ABCB5, and RANK) and the epithelial-to-mesenchymal transition markers (N-Cad, -CD44, and -MCAM/CD146) on CTCs from 17 stage IV CM patients, and investigated their BRAF mutational status by droplet digital PCR.

Results:

The number of CTCs isolated from CM patients ranged from 2 to 91 cells (38 ± 6.4) with respect to healthy donors (p < 0.0002). To confirm the melanoma origin of isolated cells, we observed an 80% agreement between their BRAF^V600 mutational status and matched primary tumors. The characterization of the immune phenotype of isolated cells revealed high interindividual and intraindividual heterogeneity that was found to correlate with the clinical outcome.

Conclusions:

The dual-step protocol of immune-magnetic sorting and subsequent dielectrophoretic DEPArray separation, turned out to be a suitable method to isolate viable CTCs from stage IV melanoma patients and enabled quantitative and qualitative analyses on these cells, which may deserve prospective evaluation for potential use in the clinical practice.

Detection and prognostic role of heterogeneous populations of melanoma circulating tumour cells

BACKGROUND

Circulating tumour cells (CTCs) can be assessed through a minimally invasive blood sample with potential utility as a predictive, prognostic and pharmacodynamic biomarker. The large heterogeneity of melanoma CTCs has hindered their detection and clinical application.

METHODS

Here we compared two microfluidic devices for the recovery of circulating melanoma cells. The presence of CTCs in 43 blood samples from patients with metastatic melanoma was evaluated using a combination of immunocytochemistry and transcript analyses of five genes by RT-PCR and 19 genes by droplet digital PCR (ddPCR), whereby a CTC score was calculated. Circulating tumour DNA (ctDNA) from the same patient blood sample, was assessed by ddPCR targeting tumour-specific mutations.

RESULTS

Our analysis revealed an extraordinary heterogeneity amongst melanoma CTCs, with multiple non-overlapping subpopulations. CTC detection using our multimarker approach was associated with shorter overall and progression-free survival. Finally, we found that CTC scores correlated with plasma ctDNA concentrations and had similar pharmacodynamic changes upon treatment initiation.

CONCLUSIONS

Despite the high phenotypic and molecular heterogeneity of melanoma CTCs, multimarker derived CTC scores could serve as viable tools for prognostication and treatment response monitoring in patients with metastatic melanoma.

Successful Treatment of Multiple Metastatic Melanoma with Nivolumab, Ipilimumab plus Denosumab Combined Therapy

Nivolumab plus ipilimumab combined therapy is one of the promising drugs that enhance the anti- immune response in patients with advanced melanoma. Therefore, to increase its response rate is of great interest to dermatologists. Recent reports suggested that, since CD8+ T cells after the administration of ICIs increase the RANKL expression to induce an immunosuppressive tumor microenvironment in melanoma, denosumab might enhance the anti-tumor effects of immune checkpoint inhibitors, such as nivolumab and ipilimumab. In this report, we present a case of multiple metastatic melanoma with nivolumab, ipilimumab plus denosumab combined therapy.

S100-EPISPOT: A New Tool to Detect Viable Circulating Melanoma Cells

Metastatic melanoma is one of the most aggressive and drug-resistant cancers with very poor overall survival. Circulating melanoma cells (CMCs) were first described in 1991. However, there is no general consensus on the clinical utility of CMC detection, largely due to conflicting results linked to the use of heterogeneous patient populations and different detection methods. Here, we developed a new EPithelial ImmunoSPOT (EPISPOT) assay to detect viable CMCs based on their secretion of the S100 protein (S100-EPISPOT). Then, we compared the results obtained with the S100-EPISPOT assay and the CellSearch^® CMC kit using blood samples from a homogeneous population of patients with metastatic melanoma. We found that S100-EPISPOT sensitivity was significantly higher than that of CellSearch^®. Specifically, the percentage of patients with ≥2 CMCs was significantly higher using S100-EPISPOT than CellSearch^® (48% and 21%, respectively; p = 0.0114). Concerning CMC prognostic value, only the CellSearch^® results showed a significant association with overall survival (p = 0.006). However, due to the higher sensitivity of the new S100-EPISPOT assay, it would be interesting to determine whether this functional test could be used in patients with non-metastatic melanoma for the early detection of tumor relapse and for monitoring the treatment response.

Combination of denosumab and immune checkpoint inhibition: experience in 29 patients with metastatic melanoma and bone metastases

BACKGROUND

PD-1 inhibition (PD-1i) is the standard of care in melanoma and other malignancies. In patients with bone metastases of solid tumors, the monoclonal antibody denosumab directed against RANKL is approved for the prevention of skeletal-related events. However, RANKL is not only relevant in osteoclastogenesis, but also has immunological effects. Hence, we aimed at investigating, whether the combination of PD-1i and denosumab produces synergistic effects in metastatic melanoma treatment.

METHODS

We retrospectively collected and analyzed clinical data of metastatic melanoma patients with bone metastases, who received PD-1i and denosumab therapy.

RESULTS

29 patients were identified with a median age of 60.7 years: 20 were male and 9 were female. 20 patients (69%) were in stage IV M1c and 9 (31%) in stage IV M1d; 52% had an increased serum LDH. 24 patients (83%) received PD-1i as first-line therapy and five patients (17%) as second- or third-line therapy. 13 patients received the triple combination nivolumab, ipilimumab and denosumab (N + I+D), 16 patients received PD-1i and denosumab (PD-1i + D). Within a median follow-up time of 19.8 months, 17 patients progressed with a median time to progression of 6 months. The objective response rate was 54% in the N + I + D group and 50% in the PD-1i + D group. Recalcification of bone metastases was radiologically observed in 18 (62%) patients. No unexpected treatment-related adverse events emerged.

CONCLUSIONS

The combination therapy of metastatic melanoma with PD-1i and denosumab was feasible without unexpected safety issues and showed a promising efficacy signal. Further investigation in prospective studies is needed.

Immunomagnetic-Enriched Subpopulations of Melanoma Circulating Tumour Cells (CTCs) Exhibit Distinct Transcriptome Profiles

Cutaneous melanoma circulating tumour cells (CTCs) are phenotypically and molecularly heterogeneous. We profiled the gene expression of CTC subpopulations immunomagnetic-captured by targeting either the melanoma-associated marker, MCSP, or the melanoma-initiating marker, ABCB5. Firstly, the expression of a subset of melanoma genes was investigated by RT-PCR in MCSP-enriched and ABCB5-enriched CTCs isolated from a total of 59 blood draws from 39 melanoma cases. Of these, 6 MCSP- and 6 ABCB5-enriched CTC fractions were further analysed using a genome-wide gene expression microarray. The transcriptional programs of both CTC subtypes included cell survival maintenance, cell proliferation, and migration pathways. ABCB5-enriched CTCs were specifically characterised by up-regulation of genes involved in epithelial to mesenchymal transition (EMT), suggesting an invasive phenotype. These findings underscore the presence of at least two distinct melanoma CTC subpopulations with distinct transcriptional programs, which may have distinct roles in disease progression and response to therapy.

An observational study of concomitant immunotherapies and denosumab in patients with advanced melanoma or lung cancer

After a case report of profound clinical response in a melanoma patient following treatment with an immune checkpoint inhibitor (ICI) and RANK-ligand inhibitor denosumab, we identified similar patients from electronic health records (EHR) and described patient characteristics and outcomes. This 2017 observational study used Flatiron Health's EHR database from ~255 US cancer clinics. Included were advanced melanoma or non-small-cell lung cancer (NSCLC) patients who received denosumab within 30 days of CTLA-4 (ipilimumab) or PD1 (pembrolizumab, nivolumab) inhibitors start with a minimum of 6 months of follow up. Real-world tumor response (rwTR) was analyzed for scans available up to 30 days after concomitant therapy. Preclinical experiments evaluated sequencing of ICI, denosumab vs monotherapy or control. Melanoma (n = 66) patients received concomitant denosumab/ICI for a mean 4.0 months, 3.1 months for NSCLC (n = 241). Two-thirds of patients had best rwTR evaluable (complete [CR], partial response [PR], stable disease [SD], or disease progression [PD]). Longer mean duration of concomitant exposure was associated with overall response rate (ORR; CR+PR) in melanoma (p = 0.0172), NSCLC (p < .0001), and combined cohorts (p < .0001). The disease control rate (ORR plus SD) was 56% amongst melanoma patients and 58% amongst NSCLC patients. Longer concomitant therapy was associated with increased overall survival, primarily in NSCLC (p < .0001). Preclinical data suggest that ICI initiated before or at same time as denosumab was optimal. Results provide proof-of-concept that rwTR is associated with concomitant denosumab/ICI. Crude survival analyses supported the association of concomitant therapy and improved outcomes outside of clinical trials and warrant comparative study.

Emerging Biomarkers in Cutaneous Melanoma

Earlier identification of aggressive melanoma remains a goal in the field of melanoma research. With new targeted and immune therapies that have revolutionized the care of patients with melanoma, the ability to predict progression and monitor or predict response to therapy has become the new focus of research into biomarkers in melanoma. In this review, promising biomarkers are highlighted. These biomarkers have been used to diagnose melanoma as well as predict progression to advanced disease and response to therapy. The biomarkers take various forms, including protein expression at the level of tissue, genetic mutations of cancer cells, and detection of circulating DNA. First, a brief description is provided about the conventional tissue markers used to stage melanoma, including tumor depth. Next, protein biomarkers, which provide both diagnostic and prognostic information, are described. This is followed by a discussion of important genetic mutations, microRNA, and epigenetic modifications that can provide therapeutic and prognostic material. Finally, emerging serologic biomarkers are reviewed, including circulating melanoma cells and exosomes. Overall the goal is to identify biomarkers that aid in the earlier identification and improved treatment of aggressive melanoma.

Melanoma circulating tumor cells: Benefits and challenges required for clinical application

The implementation of novel therapeutic interventions has improved the survival rates of melanoma patients with metastatic disease. Nonetheless, only 33% of treated cases exhibit long term responses. Circulating tumor cell (CTC) measurements are currently of clinical value in breast, prostate and colorectal cancers. However, the clinical utility of melanoma CTCs (MelCTCs) is still unclear due to challenges that appear intrinsic to MelCTCs (i.e. rarity, heterogeneity) and a lack of standardization in their isolation, across research laboratories. Here, we review the latest developments, pinpoint the challenges in MelCTC isolation and address their potential role in melanoma management.

Salmonella VNP20009-mediated RNA interference of ABCB5 moderated chemoresistance of melanoma stem cell and suppressed tumor growth more potently

Drug resistance remains an obstacle hindering the success of chemotherapy. Cancer stem cells (CSCs) have been recently found to confer resistance to chemotherapy. Therefore functional markers of CSCs should be discovered and specific therapies targeting these cells should be developed. In our investigation, a small population of B16F10 cells which was positive for ATP-binding cassette sub-family B member 5 (ABCB5) was isolated. This population displayed characteristics similar to those of CSCs and ABCB5 was identified to confer tumor growth and drug resistance in B16F10 cell line. Although targeting ABCB5 by small short interfering RNA delivered by VNP20009 failed to inhibit tumor growth, the combined treatment of VNP-shABCB5 and chemotherapy can act synergistically to delay tumor growth and enhance survival time in a primary B16F10 mice model. Results suggest that the combined treatment of VNP-shABCB5 and chemotherapy can improve the efficacy of chemotherapeutic drugs. Therefore, this combination therapy is of potential significance for melanoma treatment.

Melanoma: Genetic Abnormalities, Tumor Progression, Clonal Evolution and Tumor Initiating Cells

Melanoma is an aggressive neoplasia issued from the malignant transformation of melanocytes, the pigment-generating cells of the skin. It is responsible for about 75% of deaths due to skin cancers. Melanoma is a phenotypically and molecularly heterogeneous disease: cutaneous, uveal, acral, and mucosal melanomas have different clinical courses, are associated with different mutational profiles, and possess distinct risk factors. The discovery of the molecular abnormalities underlying melanomas has led to the promising improvement of therapy, and further progress is expected in the near future. The study of melanoma precursor lesions has led to the suggestion that the pathway of tumor evolution implies the progression from benign naevi, to dysplastic naevi, to melanoma in situ and then to invasive and metastatic melanoma. The gene alterations characterizing melanomas tend to accumulate in these precursor lesions in a sequential order. Studies carried out in recent years have, in part, elucidated the great tumorigenic potential of melanoma tumor cells. These findings have led to speculation that the cancer stem cell model cannot be applied to melanoma because, in this malignancy, tumor cells possess an intrinsic plasticity, conferring the capacity to initiate and maintain the neoplastic process to phenotypically different tumor cells.

Isolation and detection of circulating tumour cells from metastatic melanoma patients using a slanted spiral microfluidic device

Circulating Tumour Cells (CTCs) are promising cancer biomarkers. Several methods have been developed to isolate CTCs from blood samples. However, the isolation of melanoma CTCs is very challenging as a result of their extraordinary heterogeneity, which has hindered their biological and clinical study. Thus, methods that isolate CTCs based on their physical properties, rather than surface marker expression, such as microfluidic devices, are greatly needed in melanoma. Here, we assessed the ability of the slanted spiral microfluidic device to isolate melanoma CTCs via label-free enrichment. We demonstrated that this device yields recovery rates of spiked melanoma cells of over 80% and 55%, after one or two rounds of enrichment, respectively. Concurrently, a two to three log reduction of white blood cells was achieved with one or two rounds of enrichment, respectively. We characterised the isolated CTCs using multimarker flow cytometry, immunocytochemistry and gene expression. The results demonstrated that CTCs from metastatic melanoma patients were highly heterogeneous and commonly expressed stem-like markers such as PAX3 and ABCB5. The implementation of the slanted microfluidic device for melanoma CTC isolation enables further understanding of the biology of melanoma metastasis for biomarker development and to inform future treatment approaches.

Therapeutic implications of cellular and molecular biology of cancer stem cells in melanoma

Melanoma is a form of cancer that initiates in melanocytes. Melanoma has multiple phenotypically distinct subpopulation of cells, some of them have embryonic like plasticity which are involved in self-renewal, tumor initiation, metastasis and progression and provide reservoir of therapeutically resistant cells. Cancer stem cells (CSCs) can be identified and characterized based on various unique cell surface and intracellular markers. CSCs exhibit different molecular pattern with respect to non-CSCs. They maintain their stemness and chemoresistant features through specific signaling cascades. CSCs are weak in immunogenicity and act as immunosupressor in the host system. Melanoma treatment becomes difficult and survival is greatly reduced when the patient develop metastasis. Standard conventional oncology treatments such as chemotherapy, radiotherapy and surgical resection are only responsible for shrinking the bulk of the tumor mass and tumor tends to relapse. Thus, targeting CSCs and their microenvironment niche addresses the alternative of traditional cancer therapy. Combined use of CSCs targeted and traditional therapies may kill the bulk tumor and CSCs and offer a promising therapeutic strategy for the management of melanoma.

Possible mechanisms of the crosstalk between Langerhans cells and regulatory T cells in extramammary Paget disease by receptor activator of nuclear factor kappa B (RANK) ligand/RANK pathways

BACKGROUND

Extramammary Paget disease (EMPD) is a skin adenocarcinoma of apocrine gland origin, in which Paget cells express receptor activator of nuclear factor kappa B (RANK) ligand (RANKL) and matrix metalloproteinase (MMP)-7, and release soluble (s)RANKL into the tumour microenvironment. We previously reported that about 60% of the RANK⁺ cells among the stromal cells are M2 macrophages, but the identity of the remaining population of RANK⁺ cells is still unknown.

OBJECTIVES

To investigate the unknown subpopulation of RANK-expressing cells in EMPD.

METHODS

The main population of RANK-expressing cells in the epidermis was composed of epidermal Langerhans cells (LCs). To explore the effects of RANKL on LCs, we stimulated LCs generated from human CD34⁺ hematopoietic progenitor cells with graded concentrations of sRANKL. To further examine the correlation between LCs and regulatory T cells (Tregs) in EMPD, we employed immunohistochemical staining.

RESULTS

sRANKL stimulation was shown to augment the production of C-C motif chemokine ligand 17 (CCL17) from LCs. We additionally demonstrated CCL17 expression by CD1a⁺ LCs in EMPD in an immunofluorescence study. Spearman's rank correlation test confirmed a correlation between the number of LCs and the number of Foxp3⁺ Tregs in the lesional skin of invasive EMPD. In addition, the numbers of Foxp3⁺ Tregs in the sentinel lymph nodes of metastatic EMPD were significantly higher than those of metastatic melanoma, which did not express RANKL.

CONCLUSIONS

The findings suggest that the RANKL/RANK pathway in EMPD might contribute to the recruitment of Tregs and to maintenance of the tumour microenvironment.

Inflammatory regulation of stem-like cells in melanoma

The link between inflammation, immunity and cancer is well established. In the last decade, there has been considerable excitement over cancer stem cells, believed to be a subset of tumour cells responsible for their initiation, propagation and resistance to conventional chemoradiotherapy. In this review, we discuss the characterization of cancer stem cells and describe their modulation by inflammation with a focus on melanoma.

RANK-RANKL signalling in cancer

Oncogenic events combined with a favourable environment are the two main factors in the oncological process. The tumour microenvironment is composed of a complex, interconnected network of protagonists, including soluble factors such as cytokines, extracellular matrix components, interacting with fibroblasts, endothelial cells, immune cells and various specific cell types depending on the location of the cancer cells (e.g. pulmonary epithelium, osteoblasts). This diversity defines specific "niches" (e.g. vascular, immune, bone niches) involved in tumour growth and the metastatic process. These actors communicate together by direct intercellular communications and/or in an autocrine/paracrine/endocrine manner involving cytokines and growth factors. Among these glycoproteins, RANKL (receptor activator nuclear factor-κB ligand) and its receptor RANK (receptor activator nuclear factor), members of the TNF and TNFR superfamilies, have stimulated the interest of the scientific community. RANK is frequently expressed by cancer cells in contrast with RANKL which is frequently detected in the tumour microenvironment and together they participate in every step in cancer development. Their activities are markedly regulated by osteoprotegerin (OPG, a soluble decoy receptor) and its ligands, and by LGR4, a membrane receptor able to bind RANKL. The aim of the present review is to provide an overview of the functional implication of the RANK/RANKL system in cancer development, and to underline the most recent clinical studies.

RANK as a therapeutic target in cancer

The RANK signaling pathway has emerged as a new target in breast cancer as receptor activator of nuclear factor κB ligand (RANKL) and its receptor RANK mediate the pro-tumorigenic role of progesterone in the mammary gland. Thousands of cancer patients worldwide are already taking RANKL inhibitors for the management of bone metastasis, given the relevance of this pathway in osteoclastogenesis and bone resorption. RANK signaling also has multiple divergent effects in immunity and inflammation, both in the generation of active immune responses and in the induction of tolerance: it is required for lymph node organogenesis, thymic medullary epithelial development and self-tolerance, and regulates activation of several immune cells and inflammatory processes. The RANK pathway interferes with mammary epithelial differentiation and mediates the major proliferative response of mammary epithelium to progesterone and progesterone-driven expansion of mammary stem cells; it also controls hair follicle and epidermal stem cell homeostasis, pointing to RANK as a key regulator of epithelial stemness. Here we revisit the main functions of RANK signaling in bone remodeling, immune cells and epithelial differentiation. We also discuss the mechanistic evidence that supports its pleiotropic effects on cancer: from bone metastasis to immune and cancer-cell-dependent effects.

Isolation of Circulating Melanoma Cells

Circulating melanoma cells (CMCs) represent critical mediators of metastatic melanoma progression. However, isolation and characterization of CMCs has been challenging due to the low frequency of these cells and the paucity of melanoma-specific cell surface markers. Herein, we describe a method for the isolation of CMCs that employs two independent markers, displays high sensitivity for CMC enrichment, and can be readily adapted to include additional molecular melanoma markers of interest. CMCs isolated by this method are enriched for ABCB5-positive melanoma stem cells, are tumorigenic in xenotransplantation assays, and can be used for phenotypical, genetic, and functional investigations of CMC biology.

Aberrant Activation of the RANK Signaling Receptor Induces Murine Salivary Gland Tumors

Unlike cancers of related exocrine tissues such as the mammary and prostate gland, diagnosis and treatment of aggressive salivary gland malignancies have not markedly advanced in decades. Effective clinical management of malignant salivary gland cancers is undercut by our limited knowledge concerning the key molecular signals that underpin the etiopathogenesis of this rare and heterogeneous head and neck cancer. Without knowledge of the critical signals that drive salivary gland tumorigenesis, tumor vulnerabilities cannot be exploited that allow for targeted molecular therapies. This knowledge insufficiency is further exacerbated by a paucity of preclinical mouse models (as compared to other cancer fields) with which to both study salivary gland pathobiology and test novel intervention strategies. Using a mouse transgenic approach, we demonstrate that deregulation of the Receptor Activator of NFkB Ligand (RANKL)/RANK signaling axis results in rapid tumor development in all three major salivary glands. In line with its established role in other exocrine gland cancers (i.e., breast cancer), the RANKL/RANK signaling axis elicits an aggressive salivary gland tumor phenotype both at the histologic and molecular level. Despite the ability of this cytokine signaling axis to drive advanced stage disease within a short latency period, early blockade of RANKL/RANK signaling markedly attenuates the development of malignant salivary gland neoplasms. Together, our findings have uncovered a tumorigenic role for RANKL/RANK in the salivary gland and suggest that targeting this pathway may represent a novel therapeutic intervention approach in the prevention and/or treatment of this understudied head and neck cancer.

Circulating Melanoma Cell Subpopulations: Their Heterogeneity and Differential Responses to Treatment

Metastatic melanoma is a highly heterogeneous tumor; thus, methods to analyze tumor-derived cells circulating in blood should address this diversity. Taking this into account, we analyzed, using multiparametric flow cytometry, the co-expression of the melanoma markers melanoma cell adhesion molecule and melanoma-associated chondroitin sulphate proteoglycan and the tumor-initiating markers ATP-binding cassette sub-family B member 5 (ABCB5), CD271, and receptor activator of NF-κβ (RANK) in individual circulating tumor cells (CTCs) from 40 late-stage (III-IV) and 16 early-stage (I-II) melanoma patients. CTCs were heterogeneous within and between patients, with limited co-expression between the five markers analyzed. Analysis of patient matched blood and metastatic tumors revealed that ABCB5 and RANK subpopulations are more common among CTCs than in the solid tumors, suggesting a preferential selection for these cells in circulation. Pairwise comparison of CTC subpopulations longitudinally before and 6-13 weeks after treatment initiation showed that the percentage of RANK(+) CTCs significantly increased in the patients undergoing targeted therapy (N=16, P<0.01). Moreover, the presence of ⩾5 RANK(+) CTCs in the blood of patients undergoing targeted therapies was prognostic of shorter progression-free survival (hazards ratio 8.73, 95% confidence interval 1.82-41.75, P<0.01). Taken together, our results provide evidence of the heterogeneity among CTC subpopulations in melanoma and the differential response of these subpopulations to targeted therapy.

Detection of BRAF-V600E and V600K in melanoma circulating tumour cells by droplet digital PCR

OBJECTIVES

Defining the BRAF mutation status in metastatic melanoma patients is critical to selecting patients for therapeutic treatment with targeted therapies. Circulating tumour cells (CTCs) can provide an alternative source of contemporaneous tumour genetic material. However methodologies to analyse the presence of rare mutations in a background of wild-type DNA requires a detailed assessment. Here we evaluate the sensitivity of two technologies for cancer mutation detection and the suitability of whole genome amplified DNA as a template for the detection of BRAF-V600 mutations.

DESIGN AND METHODS

Serial dilutions of mutant BRAF-V600E DNA in wild-type DNA were tested using both competitive allele-specific PCR (castPCR) and droplet digital PCR (ddPCR), with and without previous whole genome amplification (WGA). Using immunomagnetic beads, we partially enriched CTCs from blood obtained from metastatic melanoma patients with confirmed BRAF mutation positive tumours and extracted RNA and DNA from the CTCs. We used RT-PCR of RNA to confirm the presence of melanoma cells in the CTC fraction then the DNAs of CTC positive fractions were WGA and tested for BRAF V600E or V600K mutations by ddPCRs.

RESULTS

WGA DNA produced lower than expected fractional abundances by castPCR analysis but not by ddPCR. Moreover, ddPCR was found to be 200 times more sensitive than castPCR and in combination with WGA produced the most concordant results, with a limit of detection of 0.0005%. BRAF-V600E or V600K mutated DNA was detected in 77% and 44%, respectively, of enriched CTC fractions from metastatic melanoma patients carrying the corresponding mutations.

CONCLUSIONS

Our results demonstrate that using ddPCR in combination with WGA DNA allows the detection with high sensitivity of cancer mutations in partially enriched CTC fractions.

Human cancer growth and therapy in immunodeficient mouse models

Since the discovery of the "nude" mouse more than 40 years ago, investigators have attempted to model human tumor growth in immunodeficient mice. Here, we summarize how the field has advanced over the ensuing years owing to improvements in the murine recipients of human tumors. These improvements include the discovery of the scid mutation and development of targeted mutations in the recombination-activating genes 1 and 2 (Rag1(null), Rag2(null)) that severely cripple the adaptive immune response of the murine host. More recently, mice deficient in adaptive immunity have been crossed with mice bearing targeted mutations designed to weaken the innate immune system, ultimately leading to the development of immunodeficient mice bearing a targeted mutation in the gene encoding the interleukin 2 (IL2) receptor common γ chain (IL2rg(null), also known in humans as cytokine receptor common subunit γ). The IL2rg(null) mutation has been used to develop several immunodeficient strains of mice, including the NOD-scid IL2rg(null) (NSG) strain. Using NSG mice as human xenograft recipients, it is now possible to grow almost all types of primary human tumors in vivo, including most solid tumors and hematological malignancies that maintain characteristics of the primary tumor in the patient. Programs to optimize patient-specific therapy using patient-derived xenograft tumor growth in NSG mice have been established at several institutions, including The Jackson Laboratory. Moreover, NSG mice can be engrafted with functional human immune systems, permitting for the first time the potential to study primary human tumors in vivo in the presence of a human immune system.

ABCB5 maintains melanoma-initiating cells through a proinflammatory cytokine signaling circuit

The drug efflux transporter ABCB5 identifies cancer stem-like cells (CSC) in diverse human malignancies, where its expression is associated with clinical disease progression and tumor recurrence. ABCB5 confers therapeutic resistance, but other functions in tumorigenesis independent of drug efflux have not been described that might help explain why it is so broadly overexpressed in human cancer. Here we show that in melanoma-initiating cells, ABCB5 controls IL1β secretion, which serves to maintain slow cycling, chemoresistant cells through an IL1β/IL8/CXCR1 cytokine signaling circuit. This CSC maintenance circuit involved reciprocal paracrine interactions with ABCB5-negative cancer cell populations. ABCB5 blockade induced cellular differentiation, reversed resistance to multiple chemotherapeutic agents, and impaired tumor growth in vivo. Together, our results defined a novel function for ABCB5 in CSC maintenance and tumor growth.

Melanoma stem cells and metastasis: mimicking hematopoietic cell trafficking?

Malignant melanoma is a highly metastatic cancer that bears responsibility for the majority of skin cancer-related deaths. Amidst the research efforts to better understand melanoma progression, there has been increasing evidence that hints at a role for a subpopulation of virulent cancer cells, termed malignant melanoma stem or initiating cells (MMICs), in metastasis formation. MMICs are characterized by their preferential ability to initiate and propagate tumor growth and their selective capacity for self-renewal and differentiation into less tumorigenic melanoma cells. The frequency of MMICs has been shown to correlate with poor clinical prognosis in melanoma. In addition, MMICs are enriched among circulating tumor cells in the peripheral blood of cancer patients, suggesting that MMICs may be a critical factor in the metastatic cascade. Although these links exist between MMICs and metastatic disease, the mechanisms by which MMICs may advance metastatic progression are only beginning to be elucidated. Recent studies have shown that MMICs express molecules critical for hematopoietic cell maintenance and trafficking, providing a possible explanation for how circulating MMICs could drive melanoma dissemination. We therefore propose that MMICs might fuel melanoma metastasis by exploiting homing mechanisms commonly utilized by hematopoietic cells. Here we review the biological properties of MMICs and the existing literature on their metastatic potential. We will discuss possible mechanisms by which MMICs might initiate metastases in the context of established knowledge of cancer stem cells in other cancers and of hematopoietic homing molecules, with a particular focus on selectins, integrins, chemokines and chemokine receptors known to be expressed by melanoma cells. Biological understanding of how these molecules might be utilized by MMICs to propel the metastatic cascade could critically impact the development of more effective therapies for advanced disease.

Multifunctional properties of RANKL/RANK in cell differentiation, proliferation and metastasis

It is known that there are close relationships between bone destruction and tumor growth in bone metastasis. RANKL is a central factor in bone metastasis, inducing osteoclastogenesis mediated by its receptor RANK. Recent reports demonstrate that RANKL has important roles in organogenesis stimulating proliferation and differentiation of epithelial and stroma cells. RANKL is induced not only by cytokines and hormones but also by UV-irradiation, inflammation and carcinogens. Expression of RANK and RANKL is found in several human cancer cell lines, and RANK signaling stimulates proliferation, migration and epithelial–mesenchymal transition of cancer cells, which may be involved in metastasis via an autocrine/paracrine mechanism. RANKL regulates the number of Tregs that produce RANKL, which may affect cancer metastasis. In this review we discuss the multifunctional roles of RANKL/RANK in osteoclastogenesis, organogenesis, and the metastasis and tumorigenesis of cancer cells.

Activities of multiple cancer-related pathways are associated with BRAF mutation and predict the resistance to BRAF/MEK inhibitors in melanoma cells

Drug resistance is a major obstacle in the targeted therapy of melanoma using BRAF/MEK inhibitors. This study was to identify BRAF V600E-associated oncogenic pathways that predict resistance of BRAF-mutated melanoma to BRAF/MEK inhibitors. We took in silico approaches to analyze the activities of 24 cancer-related pathways in melanoma cells and identify those whose activation was associated with BRAF V600E and used the support vector machine (SVM) algorithm to predict the resistance of BRAF-mutated melanoma cells to BRAF/MEK inhibitors. We then experimentally confirmed the in silico findings. In a microarray gene expression dataset of 63 melanoma cell lines, we found that activation of multiple oncogenic pathways preferentially occurred in BRAF-mutated melanoma cells. This finding was reproduced in 5 additional independent melanoma datasets. Further analysis of 46 melanoma cell lines that harbored BRAF mutation showed that 7 pathways, including TNFα, EGFR, IFNα, hypoxia, IFNγ, STAT3, and MYC, were significantly differently expressed in AZD6244-resistant compared with responsive melanoma cells. A SVM classifier built on this 7-pathway activation pattern correctly predicted the response of 10 BRAF-mutated melanoma cell lines to the MEK inhibitor AZD6244 in our experiments. We experimentally showed that TNFα, EGFR, IFNα, and IFNγ pathway activities were also upregulated in melanoma cell A375 compared with its sub-line DRO, while DRO was much more sensitive to AZD6244 than A375. In conclusion, we have identified specific oncogenic pathways preferentially activated in BRAF-mutated melanoma cells and a pathway pattern that predicts resistance of BRAF-mutated melanoma to BRAF/MEK inhibitors, providing novel clinical implications for melanoma therapy.

Stem cells and targeted approaches to melanoma cure

Melanoma stem cells, also known as malignant melanoma-initiating cells, are identifiable through expression of specific biomarkers such as ABCB5 (ATP-binding cassette, sub-family B (MDR/TAP), member 5), NGFR (nerve growth factor receptor, CD271) and ALDH (aldehyde dehydrogenase), and drive melanoma initiation and progression based on prolonged self-renewal capacity, vasculogenic differentiation and immune evasion. As we will review here, specific roles of these aggressive subpopulations have been documented in tumorigenic growth, metastatic dissemination, therapeutic resistance, and malignant recurrence. Moreover, recent findings have provided pre-clinical proof-of-concept for the potential therapeutic utility of the melanoma stem cell concept. Therefore, melanoma stem cell-directed therapeutic approaches represent promising novel strategies to improve therapy of this arguably most virulent human cancer.

Chafuroside B, an Oolong tea polyphenol, ameliorates UVB-induced DNA damage and generation of photo-immunosuppression related mediators in human keratinocytes

Chafuroside B was recently isolated as a new polyphenolic constituent of oolong tea leaves. However, the effects of chafuroside B on skin function have not been examined. In this study, we investigated the protective effects of chafuroside B against UVB-induced DNA damage, apoptosis and generation of photo-immunosuppression related mediators in cultured normal human epidermal keratinocytes (NHEK). Chafuroside B at 1 µM attenuated both UVB-induced apoptosis, evaluated in terms of caspase-3/7 activity, and UVB-induced DNA damage, evaluated in terms of formation of cyclobutane pyrimidine dimers (CPD), in NHEK exposed to UVB (20 mJ/cm²). In addition, chafuroside B at 0.3 or 1 µM suppressed the UVB-induced production of interleukin (IL)-10, tumor necrosis factor (TNF)-α, and prostaglandin E2 (PGE₂), as determined by ELISA, and conversely enhanced IL-12 mRNA expression and production, as measured by RT-PCR and ELISA. Further, chafuroside B at 1 µM also suppressed UVB-induced expression of receptor activator of nuclear factor κB ligand (RANKL) mRNA. These results indicate that chafuroside B promotes repair of UVB-induced DNA damage and ameliorates the generation of IL-10, TNF-α, PGE₂, and RANKL, all of which are UVB-induced immunosuppression related mediators. These effects of chafuroside B may be mediated at least in part through induction of IL-12 synthesis in human keratinocytes. Because chafuroside B might have practical value as a photoprotective agent, a further study of the in vivo effects of chafuroside B seems warranted.

Culture and isolation of melanoma-initiating cells

Melanoma is the most aggressive skin cancer. This unit illustrates protocols for culture and isolation of human melanoma cancer stem cells/tumor-initiating cells (CSC/TIC). We describe two complementary methods to enrich for melanoma CSC/TIC. The first approach exploits the ability of CSC/TIC to grow as tumor spheres in low-adherent culture conditions, as previously shown for neural stem cells and human embryonic stem cells. As a second approach, melanoma CSC/TIC are enriched by fluorescence-activated cell sorting for the aldehyde dehydrogenase (ALDH) enzyme activity. We previously showed that melanoma cells with high ALDH activity (ALDH(high)) are endowed with higher self-renewal and tumorigenic abilities than the population with low activity (ALDH(low)), suggesting that ALDH might be a good marker to select for melanoma CSC/TIC. This unit will also describe how to functionally test melanoma CSC/TIC by determining self-renewal in vitro and tumor-forming abilities in vivo using orthotopic xenograft assay.

Co-expression of CD44+/RANKL+ tumor cells in the carcinogenesis of oral squamous cell carcinoma

Receptor activator of nuclear factor-kappa (RANK)/receptor activator of nuclear factor-kappa B ligand (RANKL) signaling helps putative cancer stem cells (CSC) to maintain their stemness. Expression of CD44 and RANKL was analyzed in oral squamous cell carcinoma specimen (n = 191). Moreover, RANKL expression was measured in cancer cell lines (BICR3, BICR56) by immunohistochemistry and western blot analysis. Scanned images were digitally analyzed using ImageJ and the immunomembrane plug-in. CD44 and RANKL expression on protein level was correlated with clinical characteristics and impact on survival. RANKL was co-labeled with CD44 in immunohistochemical and immunofluorescence double labeling experiments. Although high CD44+/RANKL+ co-expression was significantly associated with clinicopathological factors and worse survival, multivariate analysis did not demonstrate high CD44+/RANKL+ co-expression as independent prognostic factor. Immunohistochemical and immunofluorescence double labeling experiments revealed RANKL expression by CD44+ cancer cells. RANKL specificity was confirmed by western blot analysis. For the first time, this study provides evidence that RANKL expression in OSCC might be associated with disease recurrence and a cell compartment measured by CD44+/RANKL+ co-expression within the mucosal epithelial basal layer cells.

Genetically determined ABCB5 functionality correlates with pigmentation phenotype and melanoma risk

ABCB5 is a multidrug resistance (MDR) member of the ATP-binding cassette (ABC) superfamily of active transporters and represents a marker for chemoresistant malignant melanoma-initiating cells. ABCB5 expression is closely linked to tumorigenicity and progression of diverse human malignancies, including melanoma, and is functionally required for tumor growth. Here, we genotyped 585 melanoma cases and 605 age-matched controls for 44 ABCB5 tagging single nucleotide polymorphisms (SNPs) to span a region covering 108.2kb of the gene on the 7p21.1 locus. We identified three SNPs that were associated with decreased melanoma risk in additive models: rs10231520 (OR: 0.83, 95% CI: 0.70-0.98), rs17817117 (OR: 0.82, 95% CI: 0.68-0.98), and rs2301641 (OR: 0.83, 95% CI: 0.69-0.98). Additionally, the rs2301641 SNP was associated with non-red compared to red hair color (OR: 0.38, 95% CI: 0.14-1.03) in controls. Twelve human melanoma cell lines were genotyped for the rs2301641 SNP, which encodes a non-synonymous ABCB5 amino acid change (K115E). Functional studies revealed that the E form associated with lower melanoma risk correlated significantly with decreased ABCB5 transport capacity (P<0.01) and increased melanin production (P<0.05). Our results identify novel associations of the ABCB5 K115E polymorphism with human pigmentation phenotype and melanoma risk and point to potential functional roles of ABCB5 in melanomagenesis. Moreover, they provide a first example that functional variation in a prospective cancer stem cell marker can be associated with disease risk for the corresponding malignancy.

Prominin-1 (CD133) and Metastatic Melanoma: Current Knowledge and Therapeutic Perspectives

Innovative approaches to specifically target the melanoma subpopulation responsible for local invasion and metastatic dissemination are needed. Prominin-1 (CD133) expression has been observed in many melanoma cell lines, as well as in primary and metastatic melanomas from patients. Although its function(s) in melanoma is presently unknown, prominin-1 may represent a molecular target, due to its association with melanoma stem cells and with the metastatic phenotype.

Receptor activator for NF-κB ligand in acute myeloid leukemia: expression, function, and modulation of NK cell immunosurveillance

The TNF family member receptor activator for NF-κB ligand (RANKL) and its receptors RANK and osteoprotegerin are key regulators of bone remodeling but also influence cellular functions of tumor and immune effector cells. In this work, we studied the involvement of RANK-RANKL interaction in NK cell-mediated immunosurveillance of acute myeloid leukemia (AML). Substantial levels of RANKL were found to be expressed on leukemia cells in 53 of 78 (68%) investigated patients. Signaling via RANKL into the leukemia cells stimulated their metabolic activity and induced the release of cytokines involved in AML pathophysiology. In addition, the immunomodulatory factors released by AML cells upon RANKL signaling impaired the anti-leukemia reactivity of NK cells and induced RANK expression, and NK cells of AML patients displayed significantly upregulated RANK expression compared with healthy controls. Treatment of AML cells with the clinically available RANKL Ab Denosumab resulted in enhanced NK cell anti-leukemia reactivity. This was due to both blockade of the release of NK-inhibitory factors by AML cells and prevention of RANK signaling into NK cells. The latter was found to directly impair NK anti-leukemia reactivity with a more pronounced effect on IFN-γ production compared with cytotoxicity. Together, our data unravel a previously unknown function of the RANK-RANKL molecule system in AML pathophysiology as well as NK cell function and suggest that neutralization of RANKL with therapeutic Abs may serve to reinforce NK cell reactivity in leukemia patients.

Anti-RANKL therapy for bone tumours: Basic, pre-clinical and clinical evidences

Bone remodelling is related to coordinated phases of bone resorption and bone apposition allowing the maintenance of bone integrity, the phosphocalcic homoeostasis all along the life and consequently the bone adaptation to mechanical constraints or/and to endocrine fluctuations. Unfortunately, bone is a frequent site of tumour development originated from bone cell lineages (primary bone tumours: bone sarcomas) or from nonosseous origins (bone metastases: carcinomas). These tumour cells disrupt the balance between osteoblast and osteoclast activities resulting in a disturbed bone remodelling weakening the bone tissue, in a strongly altered bone microenvironment and consequently facilitating the tumour growth. At the early stage of tumour development, osteoclast differentiation and recruitment of mature osteoclasts are strongly activated resulting in a strong bone matrix degradation and release of numerous growth factors initially stored into this organic/calcified matrix. In turn these soluble factors stimulate the proliferation of tumour cells and exacerbate their migration and their ability to initiate metastases. Because Receptor Activator of NFκB Ligand (RANKL) is absolutely required for in vivo osteoclastogenesis, its role in the bone tumour growth has been immediately pointed out and has consequently allowed the development of new targeted therapies of these malignant diseases. The present review summarises the role of RANKL in the bone tumour microenvironment, the most recent pre-clinical and clinical evidences of its targeting in bone metastases and bone sarcomas. The following sections position RANKL targeted therapy among the other anti-resorptive therapies available and underline the future directions which are currently under investigations.

Novel biomarkers and therapeutic targets for optimizing the therapeutic management of melanomas

Cutaneous malignant melanoma is the most aggressive form of skin cancer with an extremely poor survival rate for the patients diagnosed with locally invasive and metastatic disease states. Intensive research has led in last few years to an improvement of the early detection and curative treatment of primary cutaneous melanomas that are confined to the skin by tumor surgical resection. However, locally advanced and disseminated melanomas are generally resistant to conventional treatments, including ionizing radiation, systemic chemotherapy, immunotherapy and/or adjuvant stem cell-based therapies, and result in the death of patients. The rapid progression of primary melanomas to locally invasive and/or metastatic disease states remains a major obstacle for an early effective diagnosis and a curative therapeutic intervention for melanoma patients. Importantly, recent advances in the melanoma research have led to the identification of different gene products that are often implicated in the malignant transformation of melanocytic cells into melanoma cells, including melanoma stem/progenitor cells, during melanoma initiation and progression to locally advanced and metastatic disease states. The frequent deregulated genes products encompass the oncogenic B-RafV600E and N-RasQ61R mutants, different receptor tyrosine kinases and developmental pathways such as epidermal growth factor receptor (EGFR), stem cell-like factor (SCF) receptor KIT, hedgehog, Wnt/β-catenin, Notch, stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor-4 (CXCR4) and vascular endothelial growth factor (VEGF)/VEGFR receptor. These growth factors can cooperate to activate distinct tumorigenic downstream signaling elements and epithelial-mesenchymal transition (EMT)-associated molecules, including phosphatidylinositol 3’-kinase (PI3K)/Akt/ molecular target of rapamycin (mTOR), nuclear factor-kappaB (NF-κB), macrophage inhibitory cytokine-1 (MIC-1), vimentin, snail and twist. Of therapeutic relevance, these deregulated signal transduction components constitute new potential biomarkers and therapeutic targets of great clinical interest for improving the efficacy of current diagnostic and prognostic methods and management of patients diagnosed with locally advanced, metastatic and/or relapsed melanomas.