1、Contents lists available at ScienceDirectSeminars in Cancer Biologyjournal homepage: the crosstalk between melanoma and immune cells in the tumormicroenvironmentMonica Marzagallia,Nancy D.Ebeltb,Edwin R.Manuelb,aDepartment of Pharmacological and Biomolecular Sciences,Universit degli Studi di Milano,
2、Milano,ItalybDepartment of Immuno-Oncology,Beckman Research Institute of City of Hope,Duarte,California,USAA R T I C L E I N F OKeywords:Cutaneous melanomaTumor microenvironmentInnate and adaptive immunityImmunotherapyImmune escapeSuppressionMetastasisCheckpoint inhibitionCytokine therapyVaccination
3、microRNAMetabolitesTregMDSCNKDCT cellsA B S T R A C TCutaneous melanoma is the most common skin cancer with an incidence that has been rapidly increasing in thepast decades.Melanomas are among the most immunogenic tumors and,as such,have the greatest potential torespond favorably to immunotherapy.Ho
4、wever,like many cancers,melanomas acquire various suppressivemechanisms,which generally act in concert,to escape innate and adaptive immune detection and destruction.Intense research into the cellular and molecular events associated with melanomagenesis,which ultimately leadto immune suppression,has
5、 resulted in the discovery of new therapeutic targets and synergistic combinations ofimmunotherapy,targeted therapy and chemotherapy.Tremendous effort to determine efficacy of single andcombination therapies in pre-clinical and clinical phase I-III trials has led to FDA-approval of several im-munoth
6、erapeutic agents that could potentially be beneficial for aggressive,highly refractory,advanced andmetastatic melanomas.The increasing availability of approved combination therapies for melanoma and morerapid assessment of patient tumors has increased the feasibility of personalized treatment to ove
7、rcome patientand tumor heterogeneity and to achieve greater clinical benefit.Here,we review the evolution of the immunesystem during melanomagenesis,mechanisms exploited by melanoma to suppress anti-tumor immunity andmethods that have been developed to restore immunity.We emphasize that an effective
8、 therapeutic strategy willrequire coordinate activation of tumor-specific immunity as well as increased recognition and accessibility ofmelanoma cells in primary tumors and distal metastases.This review integrates available knowledge on mela-noma-specific immunity,molecular signaling pathways and mo
9、lecular targeting strategies that could be utilizedto envision therapeutics with broader application and greater efficacy for early stage and advanced metastaticmelanoma.1.IntroductionThe recent rise of immunotherapies has led to an old,but revolu-tionary,concept of cancer treatment based on the imp
10、roved activationof the endogenous immune system against cancer cells 13.The re-levance of the field is well represented by the joint contribution of the2018 Nobel Prize recipients for Physiology or Medicine James P.Allisonand Tasuku Honjo for their discovery of cancer therapy by inhibition ofnegativ
11、e immune checkpoint regulation 4,5.The first immune-checkpoint inhibitors,antibodies that specifically target the im-munoregulatory molecules cytotoxic T-lymphocyte-associated protein 4(anti-CTLA-4,Ipilimumab)and programmed cell death protein 1(anti-PD-1,Nivolumab),were approved by the US Food and D
12、rug Adminis-tration(FDA)in 2011 and 2014,respectively,for the treatment of un-resectable or metastatic melanoma,thus enormously improving themanagement of this aggressive cancer,and doubling the median sur-vival for metastatic disease 6,7.(Table 1)Malignant melanoma represents one of the most immuno
13、genic tu-mors due to its incredibly high genomic mutational load,and has thehighest potential to elicit specific adaptive antitumor immune re-sponses.It serves as an excellent model for the evaluation of innovativeimmunotherapies such as checkpoint inhibitors as well as anticancervaccines and engine
14、ered chimeric antigen receptor T cells(CAR T cells)810.Moreover,melanoma may be vulnerable to a newer cohort ofcheckpoint inhibitors targeting B-and T-lymphocyte attenuator(BTLA),T-cell immunoglobulin and mucin domain-3(TIM-3)and lymphocyte-activation gene 3(LAG-3)that continue to be areas of intens
15、e research11.Despite these major advances in cancer immunotherapy,a largesubset of melanoma patients do not respond or relapse due to primaryor acquired resistance,resulting in 4065%treatment failure forhttps:/doi.org/10.1016/j.semcancer.2019.08.002Received 29 March 2019;Received in revised form 10
16、July 2019;Accepted 4 August 2019Corresponding author at:City of Hope,1500 E.Duarte Rd,Duarte,California,91010,USA.E-mail address:emanuelcoh.org(E.R.Manuel).Seminars in Cancer Biology xxx(xxxx)xxxxxx1044-579X/Published by Elsevier Ltd.Please cite this article as:Monica Marzagalli,Nancy D.Ebelt and Ed
17、win R.Manuel,Seminars in Cancer Biology,https:/doi.org/10.1016/j.semcancer.2019.08.002patients treated with anti-PD-1,and treatment failure in over 70%ofpatients treated with anti-CTLA-4 12.The plasticity of melanoma cells leads to a phenomenon called“immune escape”,whereby cancer cells acquire a le
18、ss immunogenicphenotype and the ability to suppress anti-tumor immune cells withinthe tumor microenvironment(TME)13,14.While many factors con-tributing to immune escape have been elucidated,a therapeuticstrategy to completely re-instill curative anti-tumor immunity has notyet been realized.This revi
19、ew will describe the immune landscapeparticipating in the initial control of pre-malignant cells and then willhighlight the molecular and cellular“crosstalk”exploited by melanomato reprogram immune cells and the TME to cause immune escape andprogression to advanced disease.Finally,this review will s
20、hed light onthe innovative immunotherapies that are currently under investigationwith the aim to rescue anti-tumor immunity.2.Immune surveillance in melanoma2.1.Immunity and melanomaThe immune system is generally thought to keep the body in a stateof homeostasis by defending against infection and di
21、sease caused bybacteria,viruses,fungi,and parasites.However,it is now generallyaccepted that the immune system also functions to constantly surveyand eliminate pre-cancerous cells to prevent progression to melanoma1519.In most cases,intracellular check points are engaged within amalfunctioning cell
22、that leads to a process of self-destruction,orapoptosis,negating the need for immunity.However,in instances whenpre-malignant cells do not properly undergo apoptosis,the immunesystem must quickly act to prevent further transformation and the po-tential for immune escape 2022.As in infection,both the
23、 innate and adaptive arms of immunity mustwork together to eliminate both pre-malignant and early stages ofmelanoma,and to provide long-term protection from potential relapse2326.For this to occur,the innate compartment must quicklyeliminate tumor cells and act to recruit adaptive immune cells,prese
24、nttumor antigens through major histocompatibility complexes(MHC)andprovide the proper co-stimulatory signaling through surface receptorsand/or cytokines to generate a long-term,tumor-specific memory po-pulation.Cytokines involved in this process include interleukins(IL),interferons(IFN)and colony st
25、imulating factors(CSF),which can beactivating or suppressive in nature.Orchestrating an effective,anti-tu-moral response,especially after negative selection in the thymus thatleads to self-tolerance of tumor cells,seems to be a nearly impossibletask.However,melanoma tends to be incredibly immunogeni
26、c,gen-erating neoantigens through chromosomal rearrangements or geneticpolymorphisms that can mimic“foreign”infection and thus potentiallyelicit cytotoxic responses 2731.Many of the key innate and adaptivesubsets capable of anti-tumor activity have been identified in in-dependent studies of melanoma
27、 and other solid malignancies 23,32.The most effective therapeutic strategy should integrate as many ofthese immune subsets,without causing significant toxicity,for thegreatest clinical benefit 33.Here,we focus on the inherent anti-tumorfunctions of both innate and adaptive immune subsets that are p
28、ostu-lated to control pre-malignant cells during early stages of melanoma-genesis.2.2.Innate immunityThe fast and non-specific anti-tumor responses elicited by innateimmunity are not only critical in preventing and controlling early stagesof melanoma,but also in priming robust adaptive immunity to p
29、rovidelong-term,tumor-specific immune surveillance.Several therapeuticstrategies to inhibit melanoma growth have specifically focused on theactivation of the anti-tumor activities of naive or differentiated innatesubsets found within tumors,which includes,but are not limited to,macrophages,polymorph
30、onuclear neutrophils(PMN),natural killer(NK)cells and dendritic cells(DC)33,34.These innate cells comprisean immune system within the skin known as the skin-associated lym-phoid tissue(SALT)35.It is important to note that innate cells areincredibly plastic and can acquire both pro-and/or anti-tumor
31、func-tions depending on cell-cell or tumor-cell engagement and solublefactors present in the microenvironment 36,37.Here,we first discussthe anti-tumor activities that can be exerted by innate immune cells.Tumor-resident macrophages,PMN,NK and DC are among the firstto contribute to immediate,non-spe
32、cific cytotoxicity against melanomacells.Through activating NK receptors(NKG2D,NKp30,NKp46,DNAM-1)and agonists present on the surface of melanoma cells,NK areindependently activated to eliminate melanoma cells that have sig-nificantly downregulated their MHC class I molecules 23,38.Indeed,previous s
33、tudies have found that IL-15 stimulation of NK cells is suffi-cient to cause regression of MHC class I low melanomas in mice.It hasbeen demonstrated that the expression of NK receptor ligands by mel-anoma cells can be both dependent on tumor progression(acute vs.laterecognition)and localization(prim
34、ary vs.metastatic and in differentmetastatic sites).For example,NKp44 and NKp46 are expressed onlymph node metastases but to a lesser extent in skin metastasis.Theexpression of DNAM-1 ligands,such as nectin-2(CD112)and PVRTable 1Immunotherapies for cutaneous melanoma treatment.TargetEffectsTreatment
35、FDA ApprovedCTLA-4Bypass immune checkpointIpilimumabYesPD-1Bypass immune checkpointNivolumab,PembrolizumabYesPD-L1/B7-H1Bypass immune checkpointAtezolizumab,Avelumab,Durvalumab,CK-301In Trials:NCT02535078,NCT02027961,NCT03212404,NCT03167177,NCT03138889,NCT03178851DCs/T cellsStimulate anti-tumorimmun
36、ityIFN alpha-2bYesDCs/T cellsStimulate anti-tumorimmunityInterleukin-2YesDCs/T cellsStimulate anti-tumorimmunitySylatron(PEG-Intron)YesTLR7/8Stimulate anti-tumorimmunityResiquimobIn Trials:NCT02650635,NCT00960752,NCT02320305TregsDepletion of TregsOntakYesT cellsStimulate anti-tumorimmunitygp100 Vacc
37、ineIn Trials:NCT01744171,NCT02889861,NCT00960752,NCT00470015,NCT01176461,NCT01176474,NCT02535078Melanoma cellsDirect cytotoxicityCAR T cellIn Trials:NCT02107963,NCT03060356,NCT02830724Melanoma cellsDirect lysis of tumor cellsTalimogene laherparepvecYesAbbreviations:CTLA-4cytotoxic T-lymphocyte antig
38、en 4;PD-1programmed death 1;PD-L1programmed death ligand 1;IFNinterferon;TLRtoll-like receptor;DCdendritic cell;Tregsregulatory T cells;gp100glycoprotein 100;PEG-Intronpeginterferon alfa-2b;CARchimeric antigen receptor.M.Marzagalli,et al.Seminars in Cancer Biology xxx(xxxx)xxxxxx2(poliovirus recepto
39、r),is independent of the anatomical site and tumorstage,and the disruption of their interaction with DNAM-1 is re-sponsible of the loss of cytotoxicity and of failed tumor rejection.DNAM-1+NK cells showed higher cytotoxicity with respect to DNAM-1NK cells,despite the two populations sharing the same
40、 positivity forboth NKp46 and NKG2D,suggesting the relevance of DNAM-1 signalingin activating NK cells against melanoma,at least during early re-cognition and lymph node metastasis 38.In addition to direct tumor interactions,NK cytolytic activity can beinduced through DCs activated by soluble antige
41、nic peptides present inthe TME 23,39.In general,NK cells poorly infiltrate primary cuta-neous melanomas and mostly accumulate in the peritumoral space,however,during regression,they can be observed more dispersedthroughout the tumor tissue 4042.Intratumoral NK cells(activated)can then indirectly con
42、tribute to recruitment and maturation of an-tigen-presenting cells through the secretion of cytokines such as CXCL1(CXC-motif ligand 1)and CCL5(CC-motif ligand 5).Macrophages,PMNand DC that are recruited to tumor tissue can then phagocytize apop-totic or dead melanoma cells or debris and cross-prese
43、nt tumor antigensthat drive secondary adaptive immune responses involving CD4 helperand CD8 effector T cells(CD4 Th and CD8 Teffcells,respectively)4345.Interestingly,several studies in pre-clinical melanoma modelshave shown that soluble factors secreted by activated T cells in turninduce anti-tumor
44、activity of innate immune cells(macrophages andgranulocytes)to assist in primary tumor growth control and minimizelung metastases 46.As professional antigen-presenting cells(APCs),DCs are among themost efficient in eliciting cytotoxic T cell responses against infectionand malignancy.DCs circulate an
45、d survey various tissues throughoutthe entire body,ultimately migrating to lymph nodes where interac-tions with naive or memory T cells occur 39.Mature DCs express aplethora of co-stimulatory markers,including CD80 and CD86(clusterof differentiation 80 and 86,respectively),which are essential for ac
46、-tivation of melanoma-specific T cells 47,48.The T cell receptor(TCR)-MHC class I interaction,co-stimulatory markers and proper cy-tokines(IL-12,IFN-)produced by DCs and helper T cells are requisitefor the proper development of melanoma-specific,cytotoxic T cells49,50.Ultimately,functional effector
47、T cells must be recruited tomelanomas through a chemokine gradient(CXCL9,CXCL10,CXCL11)generated by DCs or tumor-associated stroma 51,52.Inefficiency inany or all of these steps can lead to compounding deficiencies inadaptive tumor-specific immunity.Overall,DCs exert a protective roleagainst melanom
48、a tumors as evidenced by high frequency of DCs intumor-negative sentinel lymph nodes 5355.Anti-tumor macrophages and neutrophils,designated M1 and N1,respectively,have been studied extensively for their potential use asimmunotherapy for melanoma 5661.These innate subsets exert anti-tumoral effects t
49、hrough phagocytosis,secretion of tumoricidal agents(reactive oxygen species,nitric oxide,IFN-,Fas ligand/FasL)or as-semble other tumor-specific immune cells through secretion of che-motactic factors.Interestingly,while macrophages can stimulateadaptive T cell responses,a reciprocal relationship also
50、 exists wherebyactivated Th1 cells generate tumor-killing macrophages through theexpression of IFN-,CD40 ligand and lymphotoxin-alpha.Use of mi-crobial agents(Bacillus Calmette-Guerin(BCG)and vaccinia virus)havebeen shown to be effective against melanoma by inducing the anti-microbial,cytotoxic func
