The nerve growth factor receptor CD271 is crucial to maintain tumorigenicity and stem-like properties of melanoma cells

Role of microRNA-363 during tumor progression and invasion

Recent progresses in diagnostic and therapeutic methods have significantly improved prognosis in cancer patients. However, cancer is still considered as one of the main causes of human deaths in the world. Late diagnosis in advanced tumor stages can reduce the effectiveness of treatment methods and increase mortality rate of cancer patients. Therefore, investigating the molecular mechanisms of tumor progression can help to introduce the early diagnostic markers in these patients. MicroRNA (miRNAs) has an important role in regulation of pathophysiological cellular processes. Due to their high stability in body fluids, they are always used as the non-invasive markers in cancer patients. Since, miR-363 deregulation has been reported in a wide range of cancers, we discussed the role of miR-363 during tumor progression and metastasis. It has been reported that miR-363 has mainly a tumor suppressor function through the regulation of transcription factors, apoptosis, cell cycle, and structural proteins. MiR-363 also affected the tumor progression via regulation of various signaling pathways such as WNT, MAPK, TGF-β, NOTCH, and PI3K/AKT. Therefore, miR-363 can be introduced as a probable therapeutic target as well as a non-invasive diagnostic marker in cancer patients.

Orthotopic model for the analysis of melanoma circulating tumor cells

Metastatic melanoma, a highly lethal form of skin cancer, presents significant clinical challenges due to limited therapeutic options and high metastatic capacity. Recent studies have demonstrated that cancer dissemination can occur earlier, before the diagnosis of the primary tumor. The progress in understanding the kinetics of cancer dissemination is limited by the lack of animal models that accurately mimic disease progression. We have established a xenograft model of human melanoma that spontaneously metastasizes to lymph nodes and lungs. This model allows precise monitoring of melanoma progression and is suitable for the quantitative and qualitative analysis of circulating tumor cells (CTCs). We have validated a flow cytometry-based protocol for CTCs enumeration and isolation. We could demonstrate that (i) CTCs were detectable in the bloodstream from the fourth week after tumor initiation, coinciding with the lymph node metastases appearance, (ii) excision of the primary tumor accelerated the formation of metastases in lymph nodes and lungs as early as one-week post-surgery, accompanied by the increased numbers of CTCs, and (iii) CTCs change their surface protein signature. In summary, we present a model of human melanoma that can be effectively utilized for future drug efficacy studies.

Spatial tissue proteomics reveals distinct landscapes of heterogeneity in cutaneous papillomavirus-induced keratinocyte carcinomas

Infection with certain cutaneous human papillomaviruses (HPV), in conjunction with chronic ultraviolet (UV) exposure, are the major cofactors of non-melanoma skin cancer (NMSC), the most frequent cancer type worldwide. Cutaneous squamous cell carcinomas (SCCs) as well as tumors in general represent three-dimensional entities determined by both temporal and spatial constraints. Whole tissue proteomics is a straightforward approach to understand tumorigenesis in better detail, but studies focusing on different progression states toward a dedifferentiated SCC phenotype on a spatial level are rare. Here, we applied an innovative proteomic workflow on formalin-fixed, paraffin-embedded (FFPE) epithelial tumors derived from the preclinical animal model Mastomys coucha. This rodent is naturally infected with its genuine cutaneous papillomavirus and closely mimics skin carcinogenesis in the context of cutaneous HPV infections in humans. We deciphered cellular networks by comparing diverse epithelial tissues with respect to their differentiation level and infection status. Our study reveals novel regulatory proteins and pathways associated with virus-induced tumor initiation and progression of SCCs. This approach provides the basis to better comprehend the multistep process of skin carcinogenesis.

Decoding molecular programs in melanoma brain metastases

Melanoma brain metastases (MBM) variably respond to therapeutic interventions; thus determining patient's prognosis. However, the mechanisms that govern therapy response are poorly understood. Here, we use a multi-OMICS approach and targeted sequencing (TargetSeq) to unravel the programs that potentially control the development of progressive intracranial disease. Molecularly, the expression of E-cadherin (Ecad) or NGFR, the BRAF mutation state and level of immune cell infiltration subdivides tumors into proliferative/pigmented and invasive/stem-like/therapy-resistant irrespective of the intracranial location. The analysis of MAPK inhibitor-naive and refractory MBM reveals switching from Ecad-associated into NGFR-associated programs during progression. NGFR-associated programs control cell migration and proliferation via downstream transcription factors such as SOX4. Moreover, global methylome profiling uncovers 46 differentially methylated regions that discriminate BRAF^mut and wildtype MBM. In summary, we propose that the expression of Ecad and NGFR sub- classifies MBM and suggest that the Ecad-to-NGFR phenotype switch is a rate-limiting process which potentially indicates drug-response and intracranial progression states in melanoma patients.

The Role of Schwann Cells in Cancer

Schwann cells (SCs) are the most abundant cell type in the nerves in the peripheral nervous system and compose a family of subtypes that are endowed with a variety of different functions. SCs facilitate the transmission of neural impulses, provide nutrients and protection for neurons, guide axons in nerve repair, and regulate immune functions. In the context of cancer, recent studies have revealed an active role of SCs in promoting cancer cell invasion, modulating immune responses, and transmitting pain sensation.

NGF-p75 signaling coordinates skeletal cell migration during bone repair

Bone regeneration following injury is initiated by inflammatory signals and occurs in association with infiltration by sensory nerve fibers. Together, these events are believed to coordinate angiogenesis and tissue reprogramming, but the mechanism of coupling immune signals to reinnervation and osteogenesis is unknown. Here, we found that nerve growth factor (NGF) is expressed following cranial bone injury and signals via p75 in resident mesenchymal osteogenic precursors to affect their migration into the damaged tissue. Mice lacking Ngf in myeloid cells demonstrated reduced migration of osteogenic precursors to the injury site with consequently delayed bone healing. These features were phenocopied by mice lacking p75 in Pdgfra+ osteoblast precursors. Single-cell transcriptomics identified mesenchymal subpopulations with potential roles in cell migration and immune response, altered in the context of p75 deletion. Together, these results identify the role of p75 signaling pathway in coordinating skeletal cell migration during early bone repair.

Tracking of Melanoma Cell Plasticity by Transcriptional Reporters

Clonal evolution and cellular plasticity are the genetic and non-genetic driving forces of tumor heterogeneity, which in turn determine tumor cell responses towards therapeutic drugs. Several lines of evidence suggest that therapeutic interventions foster the selection of drug-resistant neural crest stem-like cells (NCSCs) that establish minimal residual disease (MRD) in melanoma. Here, we establish a dual-reporter system, enabling the tracking of NGFR expression and mRNA stability and providing insights into the maintenance of NCSC states. We observed that a transcriptional reporter that contained a 1-kilobase fragment of the human NGFR promoter was activated only in a minor subset (0.72 ± 0.49%, range 0.3–1.5), and ~2–4% of A375 melanoma cells revealed stable NGFR mRNA. The combination of both reporters provides insights into phenotype switching and reveals that both cellular subsets gave rise to cellular heterogeneity. Moreover, whole transcriptome profiling and gene-set enrichment analysis (GSEA) of the minor cellular subset revealed hypoxia-associated programs that might serve as potential drivers of an in vitro switching of NGFR-associated phenotypes and relapse of post-BRAF inhibitor-treated tumors. Concordantly, we observed that the minor cellular subset increased in response to dabrafenib over time. In summary, our reporter-based approach provides insights into plasticity and identified a cellular subset that might be responsible for the establishment of MRD in melanoma.

Melanoma-derived small extracellular vesicles induce lymphangiogenesis and metastasis through an NGFR-dependent mechanism

Secreted extracellular vesicles (EVs) influence the tumor microenvironment and promote distal metastasis. Here, we analyzed the involvement of melanoma-secreted EVs in lymph node pre-metastatic niche formation in murine models. We found that small EVs (sEVs) derived from metastatic melanoma cell lines were enriched in nerve growth factor receptor (NGFR, p75NTR), spread through the lymphatic system and were taken up by lymphatic endothelial cells, reinforcing lymph node metastasis. Remarkably, sEVs enhanced lymphangiogenesis and tumor cell adhesion by inducing ERK kinase, nuclear factor (NF)-κB activation and intracellular adhesion molecule (ICAM)-1 expression in lymphatic endothelial cells. Importantly, ablation or inhibition of NGFR in sEVs reversed the lymphangiogenic phenotype, decreased lymph node metastasis and extended survival in pre-clinical models. Furthermore, NGFR expression was augmented in human lymph node metastases relative to that in matched primary tumors, and the frequency of NGFR⁺ metastatic melanoma cells in lymph nodes correlated with patient survival. In summary, we found that NGFR is secreted in melanoma-derived sEVs, reinforcing lymph node pre-metastatic niche formation and metastasis.

Upregulation of CD271 transcriptome in breast cancer promotes cell survival via NFκB pathway

BACKGROUND

Biological treatment of many cancers currently targets membrane bound receptors located on a cell surface. We are in a great to need identify novel membrane proteins associated with migration and metastasis of breast cancer cells. CD271, a single transmembrane protein belongs to tumor necrosis factor receptor family acts and play its role in proliferation of cancer cell. The purpose of this study is to investigate the role of CD271 in breast cancer.

METHODS AND RESULTS

In this study we analyzed the mRNA expression of CD271 in breast tumor tissue, breast cancer cell line MCF7 and isolated cancer stem cells (MCF7-CSCs) by RT-qPCR. We also measured the protein levels through western blotting in MCF-7 cell line. CD271 was upregulated in breast cancer patients among all age groups. Within the promoter region of CD271, there is a binding site for NF-κB1 which overlaps a putative quadraplex forming sequence. While CD271 also activates NF-κB pathway, down regulation of CD271 through quadraplex targeting resulted in inhibition of NF-κB and its downstream targets Nanog and Sox2.

CONCLUSION

In conclusion, our data shows that CD271 and NF-κB are regulated in interdependent manner. Upon CD271 inhibition, the NF-κB expression also reduces which in turn affects the cell proliferation and migration. These results suggest that CD271 is playing a crucial rule in cancer progression by regulating NF-κB and is a good candidate for the therapeutic targeting.

MUG Mel3 Cell Lines Reflect Heterogeneity in Melanoma and Represent a Robust Model for Melanoma in Pregnancy

Melanomas are aggressive tumors with a high metastatic potential and an increasing incidence rate. They are known for their heterogeneity and propensity to easily develop therapy-resistance. Nowadays they are one of the most common cancers diagnosed during pregnancy. Due to the difficulty in balancing maternal needs and foetal safety, melanoma is challenging to treat. The aim of this study was to provide a potential model system for the study of melanoma in pregnancy and to illustrate melanoma heterogeneity. For this purpose, a pigmented and a non-pigmented section of a lymph node metastasis from a pregnant patient were cultured under different conditions and characterized in detail. All four culture conditions exhibited different phenotypic, genotypic as well as tumorigenic properties, and resulted in four newly established melanoma cell lines. To address treatment issues, especially in pregnant patients, the effect of synthetic human lactoferricin-derived peptides was tested successfully. These new BRAF-mutated MUG Mel3 cell lines represent a valuable model in melanoma heterogeneity and melanoma pregnancy research. Furthermore, treatment with anti-tumor peptides offers an alternative to conventionally used therapeutic options—especially during pregnancy.

Effect of melanoma stem cells on melanoma metastasis

Cancer stem cells (CSCs) are involved in the metastatic process, the resistance of many types of cancer to therapeutic treatments and consequently the onset of recurrences. The CSC concept therefore significantly extends our understanding of melanoma biology. More recently, melanoma stem cells (MSCs) have been described in melanoma as expressing specific biomarkers. These primitive melanoma cells are not only capable of self-renewal and differentiation plasticity, but may also confer virulence via immune evasion and multidrug resistance, and potentially, via vasculogenic mimicry and transition to migratory and metastasizing derivatives. This review will present the specific biomarkers of MSCs, including CD133, ATP binding cassette subfamily B member 5, CD271, CD20 and aldehyde dehydrogenase, which can regulate the transduction of tumor-related signals. These signal molecules can reversely act on tumor cells and regulate tumor angiogenesis, leading to the occurrence of melanoma metastasis. Targeting these specific biomarkers could inhibit the progression of melanoma and may help the development of novel therapeutic strategies for melanoma.

Listening to the Whispers in Neuroimmune Crosstalk: A Comprehensive Workflow to Investigate Neurotrophin Receptor p75NTR Under Endogenous, Low Abundance Conditions

Inflammatory conditions are critically influenced by neuroimmune crosstalk. Cytokines and neurotrophic factors shape the responses of both nervous and immune systems. Although much progress has been made, most findings to date are based on expression of recombinant (tagged) proteins. The examination of receptor interactions by immunoprecipitation (IP) at endogenous levels provides further insight into the more subtle regulations of immune responses. Here, we present a comprehensive workflow and an optimized IP protocol that provide step-by-step instructions to investigate neurotrophin receptor p75NTR at endogenous, low abundance levels: from lysate preparation and confirmation of receptor expression to antibody validation and successful detection of protein-protein interactions. We employ human melanoma cell line A375 to validate specific antibodies and IP conditions, and apply these methods to explore p75NTR interactions in human leukemic plasmacytoid dendritic cell line PMDC05 detecting 14-3-3ϵ:p75NTR interaction in this cell type. With p75NTR as an exemplary protein, our approach provides a strategy to detect specific interaction partners even under endogenous, low abundance expression conditions.

Inhibiting the MNK1/2-eIF4E axis impairs melanoma phenotype switching and potentiates antitumor immune responses

Melanomas commonly undergo a phenotype switch, from a proliferative to an invasive state. Such tumor cell plasticity contributes to immunotherapy resistance; however, the mechanisms are not completely understood and thus are therapeutically unexploited. Using melanoma mouse models, we demonstrated that blocking the MNK1/2-eIF4E axis inhibited melanoma phenotype switching and sensitized melanoma to anti-PD-1 immunotherapy. We showed that phospho-eIF4E-deficient murine melanomas expressed high levels of melanocytic antigens, with similar results verified in patient melanomas. Mechanistically, we identified phospho-eIF4E-mediated translational control of NGFR, a critical effector of phenotype switching. Genetic ablation of phospho-eIF4E reprogrammed the immunosuppressive microenvironment, exemplified by lowered production of inflammatory factors, decreased PD-L1 expression on dendritic cells and myeloid-derived suppressor cells, and increased CD8+ T cell infiltrates. Finally, dual blockade of the MNK1/2-eIF4E axis and the PD-1/PD-L1 immune checkpoint demonstrated efficacy in multiple melanoma models regardless of their genomic classification. An increase in the presence of intratumoral stem-like TCF1+PD-1+CD8+ T cells, a characteristic essential for durable antitumor immunity, was detected in mice given a MNK1/2 inhibitor and anti-PD-1 therapy. Using MNK1/2 inhibitors to repress phospho-eIF4E thus offers a strategy to inhibit melanoma plasticity and improve response to anti-PD-1 immunotherapy.

Targeting Genome Stability in Melanoma-A New Approach to an Old Field

Despite recent groundbreaking advances in the treatment of cutaneous melanoma, it remains one of the most treatment-resistant malignancies. Due to resistance to conventional chemotherapy, the therapeutic focus has shifted away from aiming at melanoma genome stability in favor of molecularly targeted therapies. Inhibitors of the RAS/RAF/MEK/ERK (MAPK) pathway significantly slow disease progression. However, long-term clinical benefit is rare due to rapid development of drug resistance. In contrast, immune checkpoint inhibitors provide exceptionally durable responses, but only in a limited number of patients. It has been increasingly recognized that melanoma cells rely on efficient DNA repair for survival upon drug treatment, and that genome instability increases the efficacy of both MAPK inhibitors and immunotherapy. In this review, we discuss recent developments in the field of melanoma research which indicate that targeting genome stability of melanoma cells may serve as a powerful strategy to maximize the efficacy of currently available therapeutics.

Transcriptomic analysis of granulosa cell populations proximal and distal to the germinal disc of chicken preovulatory follicles

Within the oocytes of chicken preovulatory follicles, the engulfed yolk constitutes 99% of the oocyte content, while the small germinal disc (GD) (which contains the nucleus and 99% ooplasm) occupies only less than 1%. Relative to the position of the GD, the single granulosa cell layer surrounding the oocyte can be sub-divided into two sub-populations: granulosa cells proximal (named Gp cells) and distal (Gd cells) to the GD. It was reported that Gp cells and Gd cells differ in their morphology, proliferative rate and steroidogenic capacity, however, the underlying mechanism controlling granulosa cell heterogeneity remains unclear. Here we analyzed the transcriptomes of Gd and Gp cells of preovulatory (F5 and F1) follicles in chicken ovaries. We found that: (1) genes associated with cell cycle and DNA replication (CDK1, CCNB3 etc.) have comparatively higher expression levels in Gp cells than in Gd cells, while genes associated with steroidogenesis (CYP51A1, DHCR24) are highly expressed in Gd cells, indicating that Gp cells are likely more mitotic and less steroidogenic than Gd cells; (2) genes associated with extracellular matrix remodeling, cell adhesion and sperm binding (ZP3, ZP2) are differentially expressed in Gp and Gd cells; (3) Furthermore, signaling molecules (WNT4/IHH) and receptors for NGF (NGFR), epidermal growth factor (EGFR), gonadotropins (FSHR/LHR) and prostaglandin (PTGER3) are abundantly but differentially expressed in Gp and Gd cells. Taken together, our data strongly supports the notion that Gp and Gd cells of preovulatory follicles differ in their proliferation rate, steroidogenic activity, ECM organization and sperm binding capacity, which are likely controlled by gonadotropins and local ovarian factors, such as GD-derived factors.

Targeting Oncoimmune Drivers of Cancer Metastasis

Residual metastasis is a major cause of cancer-associated death. Recent advances in understanding the molecular basis of the epithelial-mesenchymal transition (EMT) and the related cancer stem cells (CSCs) have revealed the landscapes of cancer metastasis and are promising contributions to clinical treatments. However, this rarely leads to practical advances in the management of cancer in clinical settings, and thus cancer metastasis is still a threat to patients. The reason for this may be the heterogeneity and complexity caused by the evolutional transformation of tumor cells through interactions with the host environment, which is composed of numerous components, including stromal cells, vascular cells, and immune cells. The reciprocal evolution further raises the possibility of successful tumor escape, resulting in a fatal prognosis for patients. To disrupt the vicious spiral of tumor-immunity aggravation, it is important to understand the entire metastatic process and the practical implementations. Here, we provide an overview of the molecular and cellular links between tumors' biological properties and host immunity, mainly focusing on EMT and CSCs, and we also highlight therapeutic agents targeting the oncoimmune determinants driving cancer metastasis toward better practical use in the treatment of cancer patients.

CD133 Antigen as a Potential Marker of Melanoma Stem Cells: In Vitro and In Vivo Studies

Melanoma is the most dangerous type of skin cancer. Cancer stem cells (CSCs) are suspected to be responsible for the cancer recurrence and in the consequence for cancer therapy failure. CD133 is a potential marker for detection of melanoma CSCs. Experiments were performed on the B16-F10 mouse melanoma cell line. CD133+ cells were isolated using an immunomagnetic cell sorting technique. After isolation proliferative and clonogenic potential of CD133+, CD133- and CD133+/- were evaluated. The potential of CD133+ and CD133- cells for tumor induction was conducted on C57BL/6J mouse model. Three different cell quantities (100, 1000, 10000) were tested. Tumor morphology, number of mitoses, and tumor necrosis area were analyzed. Average 0.12% CD133+ cells were isolated. Compared to CD133- and unsorted CD133+/- cells, CD133+ cells were characterized by the higher proliferative and clonogenic potential. These properties were not confirmed in vivo, as both CD133+ and CD133- cells induced tumor growth in mouse model. No statistical differences in mitosis number and tumor necrosis area were observed. Simultaneous detection of CD133 antigen with other markers is necessary for accurate identification of these melanoma cancer stem cells.

Reemergence of neural crest stem cell-like states in melanoma during disease progression and treatment

Melanoma is the deadliest of all skin cancers due to its high metastatic potential. In recent years, advances in targeted therapy and immunotherapy have contributed to a remarkable progress in the treatment of metastatic disease. However, intrinsic or acquired resistance to such therapies remains a major obstacle in melanoma treatment. Melanoma disease progression, beginning from tumor initiation and growth to acquisition of invasive phenotypes and metastatic spread and acquisition of treatment resistance, has been associated with cellular dedifferentiation and the hijacking of gene regulatory networks reminiscent of the neural crest (NC)—the developmental structure which gives rise to melanocytes and hence melanoma. This review summarizes the experimental evidence for the involvement of NC stem cell (NCSC)‐like cell states during melanoma progression and addresses novel approaches to combat the emergence of stemness characteristics that have shown to be linked with aggressive disease outcome and drug resistance.

Three-dimensional multicellular cell culture for anti-melanoma drug screening: focus on tumor microenvironment

Abstract

The development of new treatments for malignant melanoma, which has the worst prognosis among skin neoplasms, remains a challenge. The tumor microenvironment aids tumor cells to grow and resist to chemotherapeutic treatment. One way to mimic and study the tumor microenvironment is by using three-dimensional (3D) co-culture models (spheroids). In this study, a melanoma heterospheroid model composed of cancer cells, fibroblasts, and macrophages was produced by liquid-overlay technique using the agarose gel. The size, growth, viability, morphology, cancer stem-like cells population and inflammatory profile of tumor heterospheroids and monospheroids were analyzed to evaluate the influence of stromal cells on these parameters. Furthermore, dacarbazine cytotoxicity was evaluated using spheroids and two-dimensional (2D) melanoma model. After finishing the experiments, it was observed the M2 macrophages induced an anti-inflammatory microenvironment in heterospheroids; fibroblasts cells support the formation of the extracellular matrix, and a higher percentage of melanoma CD271 was observed in this model. Additionally, melanoma spheroids responded differently to the dacarbazine than the 2D melanoma culture as a result of their cellular heterogeneity and 3D structure. The 3D model was shown to be a fast and reliable tool for drug screening, which can mimic the in vivo tumor microenvironment regarding interactions and complexity.

Graphic abstract

Insights into Differentiation of Melanocytes from Human Stem Cells and Their Relevance for Melanoma Treatment

Simple Summary

The reactivation of embryonic developmental programs is crucial for melanoma cells to grow and to metastasize. In order to understand this process better, we first summarize the melanocytic differentiation process both in vivo and in vitro. Secondly, we compare and highlight important similarities between neural crest cell fate during differentiation and tumor cell characteristics during melanoma mestastasis. Finally, we suggest possible therapeutic targets, which could be used to inhibit phenotype switching by developmental cues and hence also suppress the metastatic melanoma spread.

Abstract

Malignant melanoma represents a highly aggressive form of skin cancer. The metastatic process itself is mostly governed by the so-called epithelial mesenchymal transition (EMT), which confers cancer cells migrative, invasive and resistance abilities. Since EMT represents a conserved developmental process, it is worthwhile further examining the nature of early developmental steps fundamental for melanocyte differentiation. This can be done either in vivo by analyzing the physiologic embryo development in different species or by in vitro studies of melanocytic differentiation originating from embryonic human stem cells. Most importantly, external cues drive progenitor cell differentiation, which can be divided in stages favoring neural crest specification or melanocytic differentiation and proliferation. In this review, we describe ectopic factors which drive human pluripotent stem cell differentiation to melanocytes in 2D, as well as in organoid models. Furthermore, we compare developmental mechanisms with processes described to occur during melanoma development. Finally, we suggest differentiation factors as potential co-treatment options for metastatic melanoma patients.

Decoding the Role of CD271 in Melanoma

The evolution of melanoma, the most aggressive type of skin cancer, is triggered by driver mutations that are acquired in the coding regions of particularly BRAF (rat fibrosarcoma serine/threonine kinase, isoform B) or NRAS (neuroblastoma-type ras sarcoma virus) in melanocytes. Although driver mutations strongly determine tumor progression, additional factors are likely required and prerequisite for melanoma formation. Melanocytes are formed during vertebrate development in a well-controlled differentiation process of multipotent neural crest stem cells (NCSCs). However, mechanisms determining the properties of melanocytes and melanoma cells are still not well understood. The nerve growth factor receptor CD271 is likewise expressed in melanocytes, melanoma cells and NCSCs and programs the maintenance of a stem-like and migratory phenotype via a comprehensive network of associated genes. Moreover, CD271 regulates phenotype switching, a process that enables the rapid and reversible conversion of proliferative into invasive or non-stem-like states into stem-like states by yet largely unknown mechanisms. Here, we summarize current findings about CD271-associated mechanisms in melanoma cells and illustrate the role of CD271 for melanoma cell migration and metastasis, phenotype-switching, resistance to therapeutic interventions, and the maintenance of an NCSC-like state.

Insulin Reduces the Efficacy of Vemurafenib and Trametinib in Melanoma Cells

Background

Despite the progress made in the clinical management of metastatic melanoma, a patient’s response to treatment cannot be fully predicted, and intrinsic or acquired resistance that is developed in most melanoma patients warrants further research efforts. In addition to genetic factors, microenvironmental input should be considered to explain the diversity of response to treatment among melanoma patients. In this study, we evaluated the impact of insulin on patient-derived BRAF^V600E melanoma cells, either untreated or treated with vemurafenib or trametinib, inhibitors of BRAF^V600 and MEK1/2, respectively.

Methods

Cells were cultured in serum-free conditions, either with or without insulin. The activity of the MAPK/ERK and PI3K/AKT pathways was assessed by Western blotting, cell viability, and percentages of Ki-67- and NGFR-positive cells by flow cytometry. Transcript levels were analyzed using qRT-PCR, and γ-H2AX levels by immunoblotting and confocal microscopy. A luminescence-based assay was used to measure glutathione content.

Results

While insulin did not influence the MAPK/ERK pathway activity, it had a strong influence on melanoma cells, in which this pathway was suppressed by either vemurafenib or trametinib. In the presence of insulin, both drugs were much less efficient in 1) inhibiting proliferation and reducing the percentage of Ki-67-positive cells, and 2) inducing apoptosis and phosphorylation of histone H2AX in melanoma cells. Changes induced by vemurafenib and trametinib in glutathione homeostasis and DNA repair gene expression were also attenuated by insulin. Moreover, insulin impaired the combined effects of targeted drugs and doxorubicin in melanoma cells. In addition to insulin-induced PI3K/AKT activity, which was either transient or sustainable depending on the cell line, an insulin-triggered increase in the percentage of cells expressing NGFR, a marker of neural crest stem-like cells, may contribute to the reduced drug efficacy.

Conclusion

Our results demonstrate the role of insulin in reducing the efficacy of vemurafenib and trametinib. This needs clinical assessment.

Inactivating p53 is essential for nerve growth factor receptor to promote melanoma-initiating cell-stemmed tumorigenesis

Nerve growth factor receptor (NGFR, CD271, or p75NTR) is highly expressed in melanoma-initiating cells (MICs) and is critical for their proliferation and tumorigenesis, and yet the underlying mechanism(s) remain incompletely understood. We previously showed that NGFR inhibits p53 activity in a negative feedback manner in various cancer cells. Here we report that this feedback inhibition of p53 by NGFR plays an essential role in maintaining the sphere formation (stem-like phenotype) and proliferation of MICs, and in promoting MIC-derived melanoma growth in vivo. Knockdown of NGFR markedly reduced the size and number of spheroid formation of melanoma cells, which can be rescued by ectopically expressed NGFR. This reduction was also reversed by depleting p53. Consistently, knockdown of NGFR led to the suppression of MIC-derived xenograft tumor growth by inducing the p53 pathway. These results demonstrate that the NGFR-p53 feedback loop is essential for maintaining MIC stem-like phenotype and MIC-derived tumorigenesis, and further validates NGFR as a potential target for developing a molecule-based therapy against melanoma.

Pre-clinical modeling of cutaneous melanoma

Metastatic melanoma is challenging to manage. Although targeted- and immune therapies have extended survival, most patients experience therapy resistance. The adaptability of melanoma cells in nutrient- and therapeutically-challenged environments distinguishes melanoma as an ideal model for investigating therapy resistance. In this review, we discuss the current available repertoire of melanoma models including two- and three-dimensional tissue cultures, organoids, genetically engineered mice and patient-derived xenograft. In particular, we highlight how each system recapitulates different features of melanoma adaptability and can be used to better understand melanoma development, progression and therapy resistance.

Despite the new targeted and immunotherapies for metastatic melanoma, several patients show therapeutic plateau. Here, the authors review the current pre-clinical models of cutaneous melanoma and discuss their strengths and limitations that may help with overcoming therapeutic plateau.

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.

Metabolic rewiring in melanoma drug-resistant cells

Several evidences indicate that melanoma, one of the deadliest types of cancer, presents the ability to transiently shift its phenotype under treatment or microenvironmental pressure to an invasive and treatment-resistant phenotype, which is characterized by cells with slow division cycle (also called slow-cycling cells) and high-OXPHOS metabolism. Many cellular marks have been proposed to track this phenotype, such as the expression levels of the master regulator of melanocyte differentiation (MITF) and the epigenetic factor JARID1B. It seems that the slow-cycling phenotype does not necessarily present a single gene expression signature. However, many lines of evidence lead to a common metabolic rewiring process in resistant cells that activates mitochondrial metabolism and changes the mitochondrial network morphology. Here, we propose that mitochondria-targeted drugs could increase not only the efficiency of target therapy, bypassing the dynamics between fast-cycling and slow-cycling, but also the sensitivity to immunotherapy by modulation of the melanoma microenvironment.

Epigenetics and metabolism at the crossroads of stress-induced plasticity, stemness and therapeutic resistance in cancer

Despite the recent advances in the treatment of cancers, acquired drug resistance remains a major challenge in cancer management. While earlier studies suggest Darwinian factors driving acquired drug resistance, recent studies point to a more dynamic process involving phenotypic plasticity and tumor heterogeneity in the evolution of acquired drug resistance. Chronic stress after drug treatment induces intrinsic cellular reprogramming and cancer stemness through a slow-cycling persister state, which subsequently drives cancer progression. Both epigenetic and metabolic mechanisms play an important role in this dynamic process. In this review, we discuss how epigenetic and metabolic reprogramming leads to stress-induced phenotypic plasticity and acquired drug resistance, and how the two reprogramming mechanisms crosstalk with each other.

Cancer stem cells-driven tumor growth and immune escape: the Janus face of neurotrophins

Cancer Stem Cells (CSCs) are self-renewing cancer cells responsible for expansion of the malignant mass in a dynamic process shaping the tumor microenvironment. CSCs may hijack the host immune surveillance resulting in typically aggressive tumors with poor prognosis.In this review, we focus on neurotrophic control of cellular substrates and molecular mechanisms involved in CSC-driven tumor growth as well as in host immune surveillance. Neurotrophins have been demonstrated to be key tumor promoting signaling platforms. Particularly, Nerve Growth Factor (NGF) and its specific receptor Tropomyosin related kinase A (TrkA) have been implicated in initiation and progression of many aggressive cancers. On the other hand, an active NGF pathway has been recently proven to be critical to oncogenic inflammation control and in promoting immune response against cancer, pinpointing possible pro-tumoral effects of NGF/TrkA-inhibitory therapy.A better understanding of the molecular mechanisms involved in the control of tumor growth/immunoediting is essential to identify new predictive and prognostic intervention and to design more effective therapies. Fine and timely modulation of CSCs-driven tumor growth and of peripheral lymph nodes activation by the immune system will possibly open the way to precision medicine in neurotrophic therapy and improve patient's prognosis in both TrkA- dependent and independent cancers.

Diabetes impairs the angiogenic capacity of human adipose-derived stem cells by reducing the CD271+ subpopulation in adipose tissue

Type 2 diabetes mellitus is an important risk factor for cardiovascular diseases (CVDs). Therapeutic angiogenesis using adipose-derived stem cells (ADSCs) is attractive for CVD therapy. However, although it would be critical for ADSC application on CVD therapy, whether and how diabetes impairs human ADSC therapeutic potential is still uncertain. In this study, we aimed to investigate the impact of diabetes on the angiogenic potential of ADSCs in patients with CVDs, with special focus on stemness-related genes and cellular alteration of ADSCs. We established cultured ADSCs from diabetic (DM-ADSCs) and non-diabetic patients (nonDM-ADSCs) with CVDs. DM-ADSCs demonstrated limited proliferative capacity and reduced paracrine capacity of VEGF, with lower expression of the stemness gene SOX2. Angiogenic capacity and ADSC engraftment were assessed using xenograft experiments in a hindlimb ischemia model of athymic nude mice. Consistent with the results of in vitro assays, DM-ADSCs did not rescue limb ischemia. In contrast, nonDM-ADSCs induced neovascularization with enhanced engraftment. To elucidate the mechanism underlying these ADSC changes, we compared the surface marker profiles of freshly isolated ADSCs obtained from diabetic and non-diabetic patients by flow cytometry. Among studied subsets, the CD34⁺CD31^-CD271⁺ subpopulation was reduced in the adipose tissues of diabetic patients. In addition, SOX2 expression and proliferative capacity were considerably reduced in nonDM-ADSCs derived from the stromal vascular fraction (SVF) with depletion of CD271⁺ cells (p < 0.01). Our observations elucidated that reduced CD271⁺ subpopulation is critical for the impairment of ADSCs in diabetic patients. Further investigations on the CD271⁺ subset of ADSCs might provide novel insights into the mechanisms and solutions for diabetes-related ADSC dysfunction in cell therapy.

Cellular and molecular biology of cancer stem cells in melanoma: Possible therapeutic implications

Malignant melanoma is a tumor characterized by a very high level of heterogeneity, responsible for its malignant behavior and ability to escape from standard therapies. In this review we highlight the molecular and biological features of the subpopulation of cancer stem cells (CSCs), well known to be characterized by self-renewal properties, deeply involved in triggering the processes of tumor generation, metastasis, progression and drug resistance. From the molecular point of view, melanoma CSCs are identified and characterized by the expression of stemness markers, such as surface markers, ATP-binding cassette (ABC) transporters, embryonic stem cells and intracellular markers. These cells are endowed with different functional features. In particular, they play pivotal roles in the processes of tumor dissemination, epithelial-to-mesenchymal transition (EMT) and angiogenesis, mediated by specific intracellular signaling pathways; moreover, they are characterized by a unique metabolic reprogramming. As reported for other types of tumors, the CSCs subpopulation in melanoma is also characterized by a low immunogenic profile as well as by the ability to escape the immune system, through the expression of a negative modulation of T cell functions and the secretion of immunosuppressive factors. These biological features allow melanoma CSCs to escape standard treatments, thus being deeply involved in tumor relapse. Targeting the CSCs subpopulation is now considered an attractive treatment strategy; in particular, combination treatments, based on both CSCs-targeting and standard drugs, will likely increase the therapeutic options for melanoma patients. The characterization of CSCs in liquid biopsies from single patients will pave the way towards precision medicine.

CD271 is a molecular switch with divergent roles in melanoma and melanocyte development

Dysregulation of signaling networks controlling self-renewal and migration of developmental cell lineages is closely linked to the proliferative and invasive properties of tumors. Identification of such signaling pathways and their critical regulators is vital for successful design of effective targeted therapies against neoplastic tissue growth. The neurotrophin receptor (CD271/NGFR/p75NTR) is a key regulator of the melanocytic cell lineage through its ability to mediate cell growth, survival, and differentiation. Using clinical melanoma samples, normal melanocytes and global gene expression profiling we have investigated the role of CD271 in rewiring signal transduction networks of melanoma cells during neoplastic transformation. Our analysis demonstrates that depending on the cell fate of tumor initiation vs normal development, elevated levels of CD271 can serve as a switch between proliferation/survival and differentiation/cell death. Two divergent arms of neurotrophin signaling hold the balance between positive regulators of tumor growth controlled by E2F, MYC, SREBP1 and AKT3 pathways on the one hand, and differentiation, senescence, and apoptosis controlled by TRAF6/IRAK-dependent activation of AP1 and TP53 mediated processes on the other hand. A molecular network map revealed in this study uncovers CD271 as a context-specific molecular switch between normal development and malignant transformation.

Invasiveness-triggered state transition in malignant melanoma cells

Cancer cells are considered to have high morphological heterogeneity in human melanoma tissue. Here, we report that epithelial cancer cells are dominant in different development stages of human melanoma tissues. The cellular and molecular mechanisms that maintain melanoma cells in the epithelial state are further investigated in the A2058 cell line. We find that micropore (8 µm) transwell invasion, but not superficial migration in the scratch assay, can induce remarkable morphological changes between epithelial and mesenchymal melanoma cells within 4 days. The morphological switch is associated with dynamic changes of epithelial-mesenchymal transition (EMT) hallmarks E-cadherin and vimentin. Further immunoflurencent staining and co-immunoprecipitation assay showed the uncoupling of the M3 muscarinic acetylcholine receptor (mAChR) and the p75 neurotrophin receptor (p75NTR) in epithelial melanoma cells. Specific knockdown of M3 mAChR by small interfering RNA (siRNA) significantly abrogates the transition of spindle-shaped mesenchymal cells to epithelial cells. Collectively, we report a cellular model of invasiveness-triggered state transition (ITST) in which melanoma cell invasion can induce morphological changes between epithelial and mesenchymal cells. ITST is one of the biological basis for maintaining metastatic melanoma cells in the epithelial state. Furthermore, M3 mAChR receptor-mediated ITST provides a novel therapeutic strategy to inhibit the development of malignant melanoma.

Immunohistochemical expression and prognostic role of CD10, CD271 and Nestin in primary and recurrent cutaneous melanoma

BACKGROUND

CD10, CD271 and Nestin, which are proteins associated with tumor-initiating properties and/or progression potential, have not been specifically studied on malignant melanoma (MM) with cutaneous recurrences.

METHODS

We evaluated the expression of CD10, CD271 and Nestin in 27 tumor samples from 16 patients. These tumor samples corresponded to 6 primary melanomas which developed 11 ITM and 10 primary melanomas without recurrences at 10-year follow-up from specimens obtained from surgical excisions of patients referred to the Unit of Dermatology, Department of Medical-Surgical and Transplant Physiopathology, University of Milan, between 2006 and 2016.

RESULTS

We demonstrated a higher expression of CD271 and Nestin in primary tumors which recurred than control population, Nestin was expressed with significantly higher percentages in primary tumors than recurrences, and CD10 expression was statistically significant correlated with disease-free survival: cases with a lower score recurred lately than cases with higher scores.

CONCLUSIONS

Our preliminary results suggested that CD271 and Nestin can be considered early biomarkers for the development of ITM, Nesting can be useful in differentiating primary MM from cutaneous recurrences and CD10 is associated with a rapid disease progression and may be considered a potential prognostic marker.

ALDH1A3 upregulation and spontaneous metastasis formation is associated with acquired chemoresistance in colorectal cancer cells

Background

Efficiency of colorectal carcinoma treatment by chemotherapy is diminished as the resistance develops over time in patients. The same holds true for 5-fluorouracil, the drug used in first line chemotherapy of colorectal carcinoma.

Methods

Chemoresistant derivative of HT-29 cells was prepared by long-term culturing in increasing concentration of 5-fluorouracil. Cells were characterized by viability assays, flow cytometry, gene expression arrays and kinetic imaging. Immunomagnetic separation was used for isolation of subpopulations positive for cancer stem cells-related surface markers. Aldehyde dehydrogenase expression was attenuated by siRNA. In vivo studies were performed on SCID/bg mice.

Results

The prepared chemoresistant cell line labeled as HT-29/EGFP/FUR is assigned with different morphology, decreased proliferation rate and 135-fold increased IC₅₀ value for 5-fluorouracil in comparison to parental counterparts HT-29/EGFP. The capability of chemoresistant cells to form tumor xenografts, when injected subcutaneously into SCID/bg mice, was strongly compromised, however, they formed distant metastases in mouse lungs spontaneously. Derived cells preserved their resistance in vitro and in vivo even without the 5-fluorouracil selection pressure. More importantly, they were resistant to cisplatin, oxaliplatin and cyclophosphamide exhibiting high cross-resistance along with alterations in expression of cancer-stem cell markers such as CD133, CD166, CD24, CD26, CXCR4, CD271 and CD274. We also detected increased aldehyde dehydrogenase (ALDH) activity associated with overexpression of specific ALDH isoform 1A3. Its inhibition by siRNA approach partially sensitized cells to various agents, thus linking for the first time the ALDH1A3 and chemoresistance in colorectal cancer.

Conclusion

Our study demonstrated that acquired chemoresistance goes along with metastatic and migratory phenotype and can be accompanied with increased activity of aldehyde dehydrogenase. We describe here the valuable model to study molecular link between resistance to chemotherapy and metastatic dissemination.

Deciphering mechanisms of brain metastasis in melanoma - the gist of the matter

Metastasis to distant organs and particularly the brain still represents the most serious obstacle in melanoma therapies. Melanoma cells acquire a phenotype to metastasize to the brain and successfully grow there through complex mechanisms determined by microenvironmental than rather genetic cues. There do appear to be some prerequisites, including the presence of oncogenic BRAF or NRAS mutations and a loss of PTEN. Further mediators of the brain metastatic phenotype appear to be the high activation of the PI3K/AKT or STAT3 pathway or high levels of PLEKHA5 and MMP2 in metastatic cells. A yet undefined subset of brain metastases exhibit a high level of expression of CD271 that is associated with stemness, migration and survival. Hence, CD271 expression may determine specific properties of brain metastatic melanoma cells. Environmental cues - in particular those provided by brain parenchymal cells such as astrocytes - seem to help specifically guide melanoma cells that express CCR4 or CD271, potential "homing receptors". Upon entering the brain, these cells interact with brain parenchyma cells and are thereby reprogrammed to adopt a neurological phenotype. Several lines of evidence suggest that current therapies may have a negative effect by activating a program that drives tumor cells toward stemness and metastasis. Yet significant improvements have expanded the therapeutic options for treating brain metastases from melanoma, by combining potent BRAF inhibitors such as dabrafenib with checkpoint inhibitors or stereotactic surgery. Further progress toward developing new therapeutic strategies will require a more profound understanding of the mechanisms that underlie brain metastasis in melanoma.

Toward Minimal Residual Disease-Directed Therapy in Melanoma

Many patients with advanced cancers achieve dramatic responses to a panoply of therapeutics yet retain minimal residual disease (MRD), which ultimately results in relapse. To gain insights into the biology of MRD, we applied single-cell RNA sequencing to malignant cells isolated from BRAF mutant patient-derived xenograft melanoma cohorts exposed to concurrent RAF/MEK-inhibition. We identified distinct drug-tolerant transcriptional states, varying combinations of which co-occurred within MRDs from PDXs and biopsies of patients on treatment. One of these exhibited a neural crest stem cell (NCSC) transcriptional program largely driven by the nuclear receptor RXRG. An RXR antagonist mitigated accumulation of NCSCs in MRD and delayed the development of resistance. These data identify NCSCs as key drivers of resistance and illustrate the therapeutic potential of MRD-directed therapy. They also highlight how gene regulatory network architecture reprogramming may be therapeutically exploited to limit cellular heterogeneity, a key driver of disease progression and therapy resistance.

low neurotrophin receptor CD271 regulates phenotype switching in melanoma

Cutaneous melanoma represents the most fatal skin cancer due to its high metastatic capacity. According to the “phenotype switching” model, the aggressive nature of melanoma cells results from their intrinsic potential to dynamically switch from a high-proliferative/low-invasive to a low-proliferative/high-invasive state. Here we identify the low affinity neurotrophin receptor CD271 as a key effector of phenotype switching in melanoma. CD271 plays a dual role in this process by decreasing proliferation, while simultaneously promoting invasiveness. Dynamic modification of CD271 expression allows tumor cells to grow at low levels of CD271, to reduce growth and invade when CD271 expression is high, and to re-expand at a distant site upon decrease of CD271 expression. Mechanistically, the cleaved intracellular domain of CD271 controls proliferation, while the interaction of CD271 with the neurotrophin receptor Trk-A modulates cell adhesiveness through dynamic regulation of a set of cholesterol synthesis genes relevant for patient survival.

The aggressive nature of melanoma cells relies on their ability to switch from a high-proliferative/low-invasive to a low-proliferative/high-invasive state; however, the mechanisms governing this switch are unclear. Here, using in vivo models of human melanoma, the authors show that CD271 is a key regulator of phenotype switching and metastasis formation.

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.

SOX10-MITF pathway activity in melanoma cells

Melanoma is one of the most dangerous and lethal skin cancers, with a considerable metastatic potential and drug resistance. It involves a malignant transformation of melanocytes. The exact course of events in which melanocytes become melanoma cells remains unclear. Nevertheless, this process is said to be dependent on the occurrence of cells with the phenotype of progenitor cells - cells characterized by expression of proteins such as nestin, CD-133 or CD-271. The development of these cells and their survival were found to be potentially dependent on the neural crest stem cell transcription factor SOX10. This is just one of the possible roles of SOX10, which contributes to melanomagenesis by regulating the SOX10-MITF pathway, but also to melanoma cell survival, proliferation and metastasis formation. The aim of this review is to describe the broad influence of the SOX10-MITF pathway on melanoma cells.

CD271 determines migratory properties of melanoma cells

Melanoma cell expression of the nerve growth factor receptor CD271 is associated with stem-like properties. However, the contributing role of the receptor in melanoma cell migration is elusive. Here, we explored extracranial (skin, soft tissue, lymph node and liver, n = 13) and matched brain metastases (BM, n = 12) and observed a heterogeneous distribution of phenotypically distinct subsets of CD271⁺ cells. In addition, we observed that CD271 expression gradually rises along with melanoma progression and metastasis by exploration of publicly available expression data of nevi, primary melanoma (n = 31) and melanoma metastases (n = 54). Furthermore, we observed highest levels of CD271 in BM. Sub-clustering identified 99 genes differentially expressed among CD271^high and CD271^low (p < 0.05) BM-subgroups. Comparative analysis of subsets revealed increased ( ≥ 1.5fold, log2) expression of migration-associated genes and enrichment of CD271-responsible genes involved in DNA-repair and stemness. Live cell-imaging based scratch-wound assays of melanoma cells with stable knock-down of CD271 revealed a significantly reduced cell migration (3.9fold, p = 1.2E-04) and a reduced expression of FGF13, CSPG4, HMGA2 and AKT3 major candidate regulatory genes of melanoma cell migration. In summary, we provide new insights in melanoma cell migration and suggest that CD271 serves as a candidate regulator, sufficient to determine cellular properties of melanoma brain metastatic cells.

Cancer stem cell research in Iran: potentials and challenges

Treatment modalities can reduce cancer-related mortality; however, a majority of patients develop drug resistance, metastasis and relapse. It has been proposed that tumorigenic characteristics of tumors are related to a proportion of cancer cells, termed cancer stem cells (CSCs). Following the first evidence regarding the existence of CSC population in acute myeloid leukemia in 1997, publications in CSCs field showed an explosive trend in all cancer types around the world. First research paper in the field of CSCs in Iran was published in 2004 on prostate cancer. Subsequently, an annual number of publications in the field of CSCs displayed a rapidly growing trend. Therefore, in the current review, we have presented a comprehensive evaluation of the CSCs research in Iran.

A Multikinase and DNA-PK Inhibitor Combination Immunomodulates Melanomas, Suppresses Tumor Progression, and Enhances Immunotherapies

Combination therapies have the potential to improve outcomes in melanoma patients but have not yet been clinically efficacious. Here, we used high-throughput flow cytometry-based screening to identify and characterize candidate therapies that might synergize with and augment T-cell immunotherapy efficacy. Two lead therapies, regorafenib (Reg) and NU7441, were selected based on their ability to alter a variety of immunomodulatory proteins, including CD55, CD73, CD155, programmed death-ligand 1 (PD-L1), nerve growth factor receptor (NGFR), and HLA class I in a heterogeneous panel of melanomas. The therapies also upregulated several melanoma antigens, inhibited proliferation, and perturbed activation of oncogenic signaling pathways in melanomas. T cells treated with the therapies proliferated normally and exhibited a favorably altered phenotype, including increased CD25, CD28, inducible T-cell costimulator (ICOS), and reduced expression of coinhibitory receptors. Cytokine production was also increased in treated T cells. When administered in mice, REg suppressed melanoma progression in a CD8⁺ T cell-dependent manner when used alone and with various immunotherapies. Additionally, Reg altered the number, phenotype, and function of various T-cell subsets in the tumor microenvironment. These studies reveal that Reg and NU7441 influence the immunobiology of both tumor cells and T cells and enhance the efficacy of various immunotherapies. Cancer Immunol Res; 5(9); 790-803. ©2017 AACR.

How Schwann cells facilitate cancer progression in nerves

Recent studies have demonstrated a critical role for nerves in enabling tumor progression. The association of nerves with cancer cells is well established for a variety of malignant tumors, including pancreatic, prostate and the head and neck cancers. This association is often correlated with poor prognosis. A strong partnership between cancer cells and nerve cells leads to both cancer progression and expansion of the nerve network. This relationship is supported by molecular pathways related to nerve growth and repair. Peripheral nerves form complex tumor microenvironments, which are made of several cell types including Schwann cells. Recent studies have revealed that Schwann cells enable cancer progression by adopting a de-differentiated phenotype, similar to the Schwann cell response to nerve trauma. A detailed understanding of the molecular and cellular mechanisms involved in the regulation of cancer progression by the nerves is essential to design strategies to inhibit tumor progression.

Vemurafenib and trametinib reduce expression of CTGF and IL-8 in V600EBRAF melanoma cells

Clinical evidence has revealed that while RAS/RAF/MEK/ERK pathway is a crucial component of melanomagenesis, other signaling pathways can also contribute to the malignant growth and development of resistance to targeted therapies. We explored the response of ^V600EBRAF melanoma cells derived from surgical specimens and grown in stem cell medium to vemurafenib and trametinib, drugs targeting the activity of ^V600EBRAF and MEK1/2, respectively. Cell growth and apoptosis were monitored by real-time imaging system, immunophenotype and cell cycle by flow cytometry, gene expression by quantitative real-time PCR, immunoblotting and enzyme-linked immunosorbent assay. The ^V600EBRAF melanoma cell populations were diverse. Differences in morphology, pigmentation, cell cycle profiles, and immunophenotype were observed. At the molecular level, melanoma cells differed in the phosphorylation of ERK1/2, NF-κB, and β-catenin, and expression of several relevant genes, including MITF-M, DKK1, CCND1, BRAF, CXCL8, and CTGF. Despite having different characteristics, melanoma cells responded similarly to vemurafenib and trametinib. Both drugs reduced ERK1/2 phosphorylation and percentages of cells expressing Ki-67 at high level, inhibited expression of CCND1 and induced cell cycle arrest in the G_o/G₁ phase. These expected cytostatic effects were accompanied by increased CD271 expression, a marker of stem-like cells. NF-κB activity was reduced by both drugs, however, not completely abolished, whereas the level of active β-catenin was increased by drugs in three out of six cell populations. Interestingly, expression of IL-8 and CTGF was significantly reduced by treatment with vemurafenib and trametinib. Simultaneous inhibition of NF-κB activity and induction of ERK1/2 phosphorylation revealed that CTGF expression depends on ERK1/2 activity but not on NF-κB activity. Both, the positive effects of treatment with vemurafenib and trametinib such as the newly identified CTGF suppression and undesired effects such as increased CD271 expression suggesting selection of melanoma stem-like cells should be considered in the development of combination treatment for melanoma patients.

The role of the cancer stem cell marker CD271 in DNA damage response and drug resistance of melanoma cells

Several lines of evidence have suggested that stemness and acquired resistance to targeted inhibitors or chemotherapeutics are mechanistically linked. Here we observed high cell surface and total levels of nerve growth factor receptor/CD271, a marker of melanoma-initiating cells, in sub-populations of chemoresistant cell lines. CD271 expression was increased in drug-sensitive cells but not resistant cells in response to DNA-damaging chemotherapeutics etoposide, fotemustine and cisplatin. Comparative analysis of melanoma cells engineered to stably express CD271 or a targeting short hairpin RNA by expression profiling provided numerous genes regulated in a CD271-dependent manner. In-depth analysis of CD271-responsive genes uncovered the association of CD271 with regulation of DNA repair components. In addition, gene set enrichment analysis revealed enrichment of CD271-responsive genes in drug-resistant cells, among them DNA repair components. Moreover, our comparative screen identified the fibroblast growth factor 13 (FGF13) as a target of CD271, highly expressed in chemoresistant cells. Further we show that levels of CD271 determine drug response. Knock-down of CD271 in fotemustine-resistant cells decreased expression of FGF13 and at least partly restored sensitivity to fotemustine. Together, we demonstrate that expression of CD271 is responsible for genes associated with DNA repair and drug response. Further, we identified 110 CD271-responsive genes predominantly expressed in melanoma metastases, among them were NEK2, TOP2A and RAD51AP1 as potential drivers of melanoma metastasis. In addition, we provide mechanistic insight in the regulation of CD271 in response to drugs. We found that CD271 is potentially regulated by p53 and in turn is needed for a proper p53-dependent response to DNA-damaging drugs. In summary, we provide for the first time insight in a CD271-associated signaling network connecting CD271 with DNA repair, drug response and metastasis.