Topical imidazoquinoline therapy of cutaneous squamous cell carcinoma polarizes lymphoid and monocyte/macrophage populations to a Th1 and M1 cytokine pattern

From neglect to necessity: the role of innate immunity in cutaneous squamous cell carcinoma therapy

As the second most common non-melanoma skin cancer, cutaneous squamous cell carcinoma (cSCC) has experienced a significant increase in incidence. Although clinical detection is relatively easy, a considerable number of patients are diagnosed at an advanced stage, featuring local tissue infiltration and distant metastasis. Cemiplimab, along with other immune checkpoint inhibitors, enhances T cell activation by blocking the PD-1 pathway, resulting in notable improvements in clinical outcomes. Nonetheless, approximately 50% of the patients with advanced cSCC remain unresponsive to this therapeutic approach. It emphasizes the importance of finding innovative therapeutic targets and strategies to boost the success of immunotherapy across a wider range of patients. Therefore, we focused on frequently neglected functions of innate immune cells. Emerging evidence indicates that innate immune cells exhibit considerable heterogeneity and plasticity, fundamentally contributing to tumor initiation and development. The identification and eradication of cancer cells, along with the modulation of adaptive immune responses, are essential roles of these cells. Consequently, targeting innate immune cells to activate anti-tumor immune responses presents significant potential for enhancing immunotherapeutic strategies in cSCC.

Toll-like receptor 4 in pancreatic damage and immune infiltration in acute pancreatitis

Acute pancreatitis is a complex inflammatory disease resulting in extreme pain and can result in significant morbidity and mortality. It can be caused by several factors ranging from genetics, alcohol use, gall stones, and ductal obstruction caused by calcification or neutrophil extracellular traps. Acute pancreatitis is also characterized by immune cell infiltration of neutrophils and M1 macrophages. Toll-like receptor 4 (TLR4) is a pattern recognition receptor that has been noted to respond to endogenous ligands such as high mobility group box 1 (HMGB1) protein and or exogenous ligands such as lipopolysaccharide both of which can be present during the progression of acute pancreatitis. This receptor can be found on a variety of cell types from endothelial cells to resident and infiltrating immune cells leading to production of pro-inflammatory cytokines as well as immune cell activation and maturation resulting in the furthering of pancreatic damage during acute pancreatitis. In this review we will address the various mechanisms mediated by TLR4 in the advancement of acute pancreatitis and how targeting this receptor could lead to improved outcomes for patients suffering from this condition.

Local Chemotherapy as an Adjuvant Treatment in Unresectable Squamous Cell Carcinoma: What Do We Know So Far?

Background: Squamous cell carcinoma (SCC) is one of the most common cancers involving skin and oral mucosa. Although this condition's gold-standard treatment is the surgical removal of the lesions, the physician must propose alternative treatments in some cases due to the patient's ineligibility for surgery. Among the available alternative therapies, local chemotherapy may represent an initial treatment in combination with radiotherapy or systemic chemotherapy due to the low frequency of side-effects and the lack of necessity for expensive devices. Methods: In this paper, we review all available literature in various databases (PubMed, Scopus-Embase, Web of Science), proposing local chemotherapy as a treatment for cutaneous and oral SCC. Exclusion criteria included ocular lesions (where topical treatments are common), non-English language, and non-human studies. Results: We included 14 studies in this review. The majority were case reports and case series describing the treatment of non-resectable localized SCC with either imiquimod or 5-fluorouracil. We also analyzed small studies proposing combination treatments. Almost all studies reported an excellent clinical outcome, with a low risk of relapses in time. Conclusions: Resection of the lesion remains the gold-standard treatment for SCC. When this approach is not feasible, local chemotherapy may represent a treatment alternative, and it may also be associated with radiotherapy or systemic chemotherapy.

Case Report: Combined Intra-Lesional IL-2 and Topical Imiquimod Safely and Effectively Clears Multi-Focal, High Grade Cutaneous Squamous Cell Cancer in a Combined Liver and Kidney Transplant Patient

Cutaneous squamous cell carcinoma (cSCC) is the second most common non-melanoma skin cancer worldwide, with ever increasing incidence and mortality. While most patients can be treated successfully with surgical excision, cryotherapy, or radiation therapy, there exist a subset of patients with aggressive cSCC who lack adequate therapies. Among these patients are solid organ transplant recipients who due to their immunosuppression, develop cSCC at a dramatically increased rate compared to the normal population. The enhanced ability of the tumor to effectively undergo immune escape in these patients leads to more aggressive tumors with a propensity to recur and metastasize. Herein, we present a case of aggressive, multi-focal cSCC in a double organ transplant recipient to frame our discussion and current understanding of the immunobiology of cSCC. We consider factors that contribute to the significantly increased incidence of cSCC in the context of immunosuppression in this patient population. Finally, we briefly review current literature describing experience with localized therapies for cSCC and present a strong argument and rationale for consideration of an IL-2 based intra-lesional treatment strategy for cSCC, particularly in this immunosuppressed patient population.

Targeted Repolarization of Tumor-Associated Macrophages via Imidazoquinoline-Linked Nanobodies

Tumor-associated macrophages (TAMs) promote the immune suppressive microenvironment inside tumors and are, therefore, considered as a promising target for the next generation of cancer immunotherapies. To repolarize their phenotype into a tumoricidal state, the Toll-like receptor 7/8 agonist imidazoquinoline IMDQ is site-specifically and quantitatively coupled to single chain antibody fragments, so-called nanobodies, targeting the macrophage mannose receptor (MMR) on TAMs. Intravenous injection of these conjugates result in a tumor- and cell-specific delivery of IMDQ into MMRhigh TAMs, causing a significant decline in tumor growth. This is accompanied by a repolarization of TAMs towards a pro-inflammatory phenotype and an increase in anti-tumor T cell responses. Therefore, the therapeutic benefit of such nanobody-drug conjugates may pave the road towards effective macrophage re-educating cancer immunotherapies.

Targeting macrophages: a novel avenue for cancer drug discovery

Introduction: Tumor-associated macrophages (TAMs) make up a significant portion of the tumor microenvironment. Emerging clinical evidence indicate that cytokines present in the tumor microenvironment influence TAMs to play an immunosuppressive role by acquiring a pro-tumoral phenotype. However, TAMs are inherently plastic cells that can be phenotypically reprogrammed to elicit an anti-tumoral response. Therapeutic strategies that focus on targeting TAMs have opened new avenues for drug discoveries.Areas covered: This review discusses recent developments in TAM targeted immunotherapy in both preclinical and clinical settings. This article highlights the potential signaling pathways that can be targeted for macrophage reprogramming and discusses the progress of current clinical trials involved in TAMs targeting. Novel nanoparticle-based drug delivery strategies involved in macrophage-based cancer therapeutics and diagnostics are also discussed.Expert opinion: TAM targeted therapies have limited success in clinics due to reasons such as insufficient inhibition of signaling pathways, lower drug accumulation in the tumor, activation of feedback signaling pathways that induce resistance to monotherapies and systemic dose-related toxicities. Nanoparticle-based delivery platforms could overcome these challenges since they enable encapsulation of multiple drugs that target different signaling pathways and enhance intratumoral delivery and can enable delivery of imaging agents.

M2-macrophage infiltration and macrophage traits of tumor cells in urinary bladder cancer

BACKGROUND

Tumor-associated macrophages (TAMs) constitute a subset of nonneoplastic cells in tumor stroma and influence cancer progression in solid tumors. The clinical significance of TAMs in urinary bladder cancer (UBC) is controversial.

METHODS

We prospectively studied 103 patients with stage pT1-T4 UBC treated with cystectomy and pelvic lymph node dissection. Tumor sections were immunostained with M2-specific macrophage marker CD163 and proliferation marker Ki-67. The expression of these markers in cancer cells as well as macrophage infiltration (MI) in tumor stroma was analyzed in relation to clinical data and outcome.

RESULTS

The mean rate of CD163 and Ki-67 expressed by cancer cells were 35% and 78%, respectively. With borderline significance, MI was associated with lower rate of lymph node metastasis (P = 0.06). CD163 expression in cancer cells was proportional to MI (P<0.014). Patients with CD163-positive tumors and strong MI had significantly longer cancer-specific survival (CSS) (76 months), compared to patient with CD163-positive tumors and weak MI (28 months) (P = 0.02).

CONCLUSIONS

M2-specific MI tends to be inversely correlated with LN metastasis and improved CSS in UBC. MI might have protective impact in CD163-positive tumors. Expression of CD163 in cancer cells is significantly correlated with MI and might have a tumor promoting impact.

Therapeutic IgE Antibodies: Harnessing a Macrophage-Mediated Immune Surveillance Mechanism against Cancer

IgG monoclonal antibodies have made significant contributions to cancer therapy, but suffer from several limitations that restrict their effectiveness in unleashing host immune system components against tumors. The development of monoclonal antibodies of an alternative class, namely IgE, may offer enhanced immune surveillance and superior effector cell potency against cancer cells. In our recent article, we elaborate our proof-of-concept studies of a mouse/human chimeric IgE antibody (MOv18 IgE), which is specific for the cancer-associated antigen folate receptor alpha. We demonstrate superior antitumor efficacy for IgE compared with an otherwise identical IgG in a syngeneic immunocompetent animal, and we identify TNFα/MCP-1 signaling as an IgE-mediated mechanism of monocyte and macrophage activation and recruitment to tumors. These findings draw parallels with powerful macrophage-activating functions employed by IgE against parasites, rather than allergic IgE mechanisms. The potential clinical application of IgE-derived drugs in clinical oncology is clear if the antitumor activity of MOv18 IgE in these preclinical experiments can be replicated in patients. In particular, different IgE antibodies with specificity for many other antigens already validated as targets for IgG suggest a wide potential for development of a novel class of antibody therapy. Cancer Res; 77(11); 2779-83. ©2017 AACR.

Tumor-associated macrophages: unwitting accomplices in breast cancer malignancy

Deleterious inflammation is a primary feature of breast cancer. Accumulating evidence demonstrates that macrophages, the most abundant leukocyte population in mammary tumors, have a critical role at each stage of cancer progression. Such tumor-associated macrophages facilitate neoplastic transformation, tumor immune evasion and the subsequent metastatic cascade. Herein, we discuss the dynamic process whereby molecular and cellular features of the tumor microenvironment act to license tissue-repair mechanisms of macrophages, fostering angiogenesis, metastasis and the support of cancer stem cells. We illustrate how tumors induce, then exploit trophic macrophages to subvert innate and adaptive immune responses capable of destroying malignant cells. Finally, we discuss compelling evidence from murine models of cancer and early clinical trials in support of macrophage-targeted intervention strategies with the potential to dramatically reduce breast cancer morbidity and mortality.

Macrophages modulate migration and invasion of human tongue squamous cell carcinoma

Oral tongue squamous cell carcinoma (OTSCC) has a high mortality rate and the incidence is rising worldwide. Despite advances in treatment, the disease lacks specific prognostic markers and treatment modality. The spreading of OTSCC is dependent on the tumor microenvironment and involves tumor-associated macrophages (TAMs). Although the presence of TAMs is associated with poor prognosis in OTSCC, the specific mechanisms underlying this are still unknown. The aim here was to investigate the effect of macrophages (Mfs) on HSC-3 tongue carcinoma cells and NF-kappaB activity. We polarized THP-1 cells to M1 (inflammatory), M2 (TAM-like) and R848 (imidazoquinoline-treated) type Mfs. We then investigated the effect of Mfs on HSC-3 cell migration and NF-kappaB activity, cytokine production and invasion using several different in vitro migration models, a human 3D tissue invasion model, antibody arrays, confocal microscopy, immunohistochemistry and a mouse invasion model. We found that in co-culture studies all types of Mfs fused with HSC-3 cells, a process which was partially due to efferocytosis. HSC-3 cells induced expression of epidermal growth factor and transforming growth factor-beta in co-cultures with M2 Mfs. Direct cell-cell contact between M2 Mfs and HSC-3 cells induced migration and invasion of HSC-3 cells while M1 Mfs reduced HSC-3 cell invasion. M2 Mfs had an excess of NF-kappaB p50 subunit and a lack of p65 subunits both in the presence and absence of HSC-3 cells, indicating dysregulation and pro-tumorigenic NF-kappaB activation. TAM-like cells were abundantly present in close vicinity to carcinoma cells in OTSCC patient samples. We conclude that M2 Mfs/TAMs have an important role in OTSCC regulating adhesion, migration, invasion and cytokine production of carcinoma cells favouring tumor growth. These results demonstrate that OTSCC patients could benefit from therapies targeting TAMs, polarizing TAM-like M2 Mfs to inflammatory macrophages and modulating NF-kappaB activity.

Direct Toll-Like Receptor 8 signaling increases the functional avidity of human CD8+ T lymphocytes generated for adoptive T cell therapy strategies

Adoptive transfer of in vitro activated and expanded antigen-specific cytotoxic T lymphocytes (CTLs) is a promising therapeutic strategy for infectious diseases and cancers. Obtaining in vitro a sufficient amount of highly specific cytotoxic cells and capable of retaining cytotoxic activity in vivo remains problematic. We studied the role of Toll-Like Receptor-8 (TLR8) engagement on peripheral CTLs activated with melanoma antigen MART-1-expressing artificial antigen-presenting cells (AAPCs). After a 3-week co-culture, 3–27% of specific CTLs were consistently obtained. CTLs expressed TLR8 in the intracellular compartment and at the cell surface. Specific CTLs activated with a TLR8 agonist (CL075) 24 h before the end of the culture displayed neither any change in their production levels of molecules involved in cytotoxicity (IFN-γ, Granzyme B, and TNF-α) nor major significant change in their cell surface phenotype. However, these TLR8-stimulated lymphocytes displayed increased cytotoxic activity against specific peptide-pulsed target cells related to an increase in specific anti-melanoma CTL functional avidity. TLR8 engagement on CTLs could, therefore, be useful in different immunotherapy strategies.

Targeting tumor-infiltrating macrophages to combat cancer

Tumor-associated macrophages are one of the major constituents of tumor stroma in many solid tumors and there is compelling preclinical and clinical evidence that macrophages promote cancer initiation and malignant progression. Therefore, these cells represent potential targets for therapeutic benefit. In this review, we will summarize macrophage phenotypic heterogeneity, the current understanding of how tumors take advantage of macrophage plasticity to generate immunosuppression, and how manipulation of specific macrophage populations can be used for therapeutic purposes through translational approaches.

Platelet-derived growth factor-C (PDGF-C) induces anti-apoptotic effects on macrophages through Akt and Bad phosphorylation

PDGF-C, which is abundant in the malignant breast tumor microenvironment, plays an important role in cell growth and survival. Because tumor-associated macrophages (TAMs) contribute to cancer malignancy, macrophage survival mechanisms are an attractive area of research into controlling tumor progression. In this study, we investigated PDGF-C-mediated signaling pathways involved in anti-apoptotic effects in macrophages. We found that the human malignant breast cancer cell line MDA-MB-231 produced high quantities of PDGF-C, whereas benign MCF-7 cells did not. Recombinant PDGF-C induced PDGF receptor α chain phosphorylation, followed by Akt and Bad phosphorylation in THP-1-derived macrophages. MDA-MB-231 culture supernatants also activated macrophage PDGF-Rα. PDGF-C prevented staurosporine-induced macrophage apoptosis by inhibiting the activation of caspase-3, -7, -8, and -9 and cleavage of poly(ADP-ribose) polymerase. Finally, TAMs isolated from the PDGF-C knockdown murine breast cancer cell line 4T1 and PDGF-C knockdown MDA-MB-231-derived tumor mass showed higher rates of apoptosis than the respective WT controls. Collectively, our results suggest that tumor cell-derived PDGF-C enhances TAM survival, promoting tumor malignancy.

Anti-tumour strategies aiming to target tumour-associated macrophages

Tumour-associated macrophages (TAMs) represent a predominant population of inflammatory cells that present in solid tumours. TAMs are mostly characterized as alternatively activated M2-like macrophages and are known to orchestrate nearly all stages of tumour progression. Experimental investigations indicate that TAMs contribute to drug-resistance and radio-protective effects, and clinical evidence shows that an elevated number of TAMs and their M2 profile are correlated with therapy failure and poor prognosis in cancer patients. Recently, many studies on TAM-targeted strategies have made significant progress and some pilot works have achieved encouraging results. Among these, connections between some anti-tumour drugs and their influence on TAMs have been suggested. In this review, we will summarize recent advances in TAM-targeted strategies for tumour therapy. Based on the proposed mechanisms, those strategies are grouped into four categories: (i) inhibiting macrophage recruitment; (ii) suppressing TAM survival; (iii) enhancing M1-like tumoricidal activity of TAMs; (iv) blocking M2-like tumour-promoting activity of TAMs. It is desired that further attention be drawn to this research field and more effort be made to promote TAM-targeted tumour therapy.

Topical treatment of actinic keratosis with imiquimod 5% cream

The viability and the efficiency of imiquimod 5% cream in a cat which suffered from nasal actinic keratosis were evaluated. The procedures were carried out at home by the owners themselves. Six packets of the cream were used, one per week, in three consecutive daily applications, with a four-day interval (without treatment). The cytological results were negative for neoplastic cells 30 days after the end of the treatment. A clinical revision was conducted 18 months later and the animal showed no signs of recurrence. The cream proved to be safe and efficient. There are no reports regarding efficiency in animals concerning the treatment with imiquimod 5% cream and also regarding other effects related to this treatment. A case report presenting a positive response can reveal with terapeutical possibilities that it would be easily available and applicable for all professionals. In the future it would be a new alternative to avoid progressions of this kind of neoplasia which is often observed in the small animal clinic.

Exogenous control of the expression of Group I CD1 molecules competent for presentation of microbial nonpeptide antigens to human T lymphocytes

Group I CD1 (CD1a, CD1b, and CD1c) glycoproteins expressed on immature and mature dendritic cells present nonpeptide antigens (i.e., lipid or glycolipid molecules mainly of microbial origin) to T cells. Cytotoxic CD1-restricted T lymphocytes recognizing mycobacterial lipid antigens were found in tuberculosis patients. However, thanks to a complex interplay between mycobacteria and CD1 system, M. tuberculosis possesses a successful tactic based, at least in part, on CD1 downregulation to evade CD1-dependent immunity. On the ground of these findings, it is reasonable to hypothesize that modulation of CD1 protein expression by chemical, biological, or infectious agents could influence host's immune reactivity against M. tuberculosis-associated lipids, possibly affecting antitubercular resistance. This scenario prompted us to perform a detailed analysis of the literature concerning the effect of external agents on Group I CD1 expression in order to obtain valuable information on the possible strategies to be adopted for driving properly CD1-dependent immune functions in human pathology and in particular, in human tuberculosis.

New perspective in immunotherapy: local imiquimod treatment

Az imikimod, az imidazol-kinolin-aminok családjába tartozó, kis, szintetikus, nukleotidszerű molekula. Ismert immunválasz-módosító, vírusellenes és tumorellenes hatása, amelyet a Toll-like receptorok (TLR7 és TLR8) közvetítenek. Az imikimod főként a TLR7-et kifejező plazmacitoid dendritikus sejteket és a Langerhans-sejteket célozza meg, és csak másodlagosan vesz részt egyéb gyulladásos sejtek aktiválásában. A TLR7 stimulációjakor indukálódó jelátviteli mechanizmusok mind a veleszületett, mind a szerzett immunrendszert aktiválják, különös tekintettel a sejt által közvetített immunreakciókra. Az 5%-os imikimodkrém (Aldara, MEDA Pharma) lokális alkalmazása hatékonynak bizonyult az aktinikus keratosisok, a superficialis basaliomák és a külső nemi szerveken és perianalisan elhelyezkedő condylomák kezelésében. Az imikimod különösen alkalmas kiterjedt, látszólag tünetmentes, de daganatsejteket tartalmazó mezők („field cancerization”) kezelésére. A beteg által alkalmazott otthoni kezelés kiváló kozmetikai eredményt ad. Irodalmi adatok utalnak továbbá az imikimod hatékonyságára nodularis basalioma és egyéb, nem melanomatípusú bőrdaganat kezelésében. Az imikimod lokális alkalmazása jól tolerálható, a krém az alkalmazás helyén enyhe vagy közepesen súlyos gyulladásos reakciót okozhat. Ez a dolgozat átfogó képet ad az imikimod alkalmazásával kapcsolatos eddigi tapasztalatokról és a potenciális jövőbeli felhasználási lehetőségekről.

Reciprocal regulation of activating and inhibitory Fc{gamma} receptors by TLR7/8 activation: implications for tumor immunotherapy

PURPOSE

Activation of Toll-like receptors (TLR) 7 and 8 by engineered agonists has been shown to aid in combating viruses and tumors. Here, we wished to test the effect of TLR7/8 activation on monocyte Fcgamma receptor (FcgammaR) function, as they are critical mediators of antibody therapy.

EXPERIMENTAL DESIGN

The effect of the TLR7/8 agonist R-848 on cytokine production and antibody-dependent cellular cytotoxicity by human peripheral blood monocytes was tested. Affymetrix microarrays were done to examine genomewide transcriptional responses of monocytes to R-848 and Western blots were done to measure protein levels of FcgammaR. Murine bone marrow-derived macrophages from WT and knockout mice were examined to determine the downstream pathway involved with regulating FcgammaR expression. The efficacy of R-848 as an adjuvant for antibody therapy was tested using a CT26-HER2/neu solid tumor model.

RESULTS

Overnight incubation with R-848 increased FcgammaR-mediated cytokine production and antibody-dependent cellular cytotoxicity in human peripheral blood monocytes. Expression of FcgammaRI, FcgammaRIIa, and the common gamma-subunit was increased. Surprisingly, expression of the inhibitory FcgammaRIIb was almost completely abolished. In bone marrow-derived macrophage, this required TLR7 and MyD88, as R-848 did not increase expression of the gamma-subunit in TLR7(-/-) nor MyD88(-/-) cells. In a mouse solid tumor model, R-848 treatment superadditively enhanced the effects of antitumor antibody.

CONCLUSIONS

These results show an as-yet-undiscovered regulatory and functional link between the TLR7/8 and FcgammaR pathways. This suggests that TLR7/8 agonists may be especially beneficial during antibody therapy.

Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topical imiquimod 5% cream

Imiquimod is a topical immune response modifier and stimulator used in humans to treat a number of cutaneous neoplasms. This case report describes a cat with actinic keratoses and squamous cell carcinoma of the pinnae. The pinnal lesions were treated with topical 5% imiquimod three times per week. Treatment was discontinued after 82 days of therapy. Twelve weeks of topical imiquimod application resulted in clinical resolution of the pinnal lesions. Although no post-treatment biopsies were performed, there was no relapse of the pinnal lesions in 5 months of clinical follow-up. Expected side effects were limited to erythema, crusting, alopecia, and mild discomfort at the sites of application during the first 3 weeks of application. These results suggest that topical imiquimod, although unproven, might be a therapeutic option or adjunct to therapy for cats with actinic keratoses and squamous cell carcinoma, especially those cats for whom surgery and radiation therapy are not an option.

Imidazoquinoline acts as immune adjuvant for functional alteration of thymic stromal lymphopoietin-mediated allergic T cell response

Atopic dermatitis is a major allergic disease that develops through dysregulation of Th2-mediated inflammation. Although dendritic cells (DCs) have been thought to play a critical role in the upstream phase of the allergic cascade, conventional drugs such as steroids and chemical mediator antagonists target the effector cells or factors in allergic inflammation. Recently, it has been demonstrated that interaction between thymic stromal lymphopoietin (TSLP) and human DCs plays an essential role in evoking inflammatory Th2 responses in allergy through OX40 ligand expression on DCs. In this study, we provide evidence that R848, an imidazoquinoline compound, which is a TLR ligand and a strong Th1 response-inducing reagent, is a potent adjuvant for the alteration of the Th2-inducing potency of human DCs activated by TSLP (TSLP-DCs). R848 inhibited the inflammatory Th2-inducing capacity of TSLP-DCs and redirected them to possessing an IL-10 and IFN-gamma-producing regulatory Th1-inducing capacity. This functional alteration depended on both repression of OX40 ligand expression and induction of IL-12 production from DCs by the addition of R848. Additionally, R848 had the ability to inhibit the TSLP-mediated expansion and maintenance of the Th2 memory response. These findings suggest that imidazoquinoline may be a useful in the treatment of allergic diseases that are triggered by TSLP.

Human squamous cell carcinomas evade the immune response by down-regulation of vascular E-selectin and recruitment of regulatory T cells

Squamous cell carcinomas (SCCs) of the skin are sun-induced skin cancers that are particularly numerous in patients on T cell immunosuppression. We found that blood vessels in SCCs did not express E-selectin, and tumors contained few cutaneous lymphocyte antigen (CLA)(+) T cells, the cell type thought to provide cutaneous immunosurveillance. Tumors treated with the Toll-like receptor (TLR)7 agonist imiquimod before excision showed induction of E-selectin on tumor vessels, recruitment of CLA(+) CD8(+) T cells, and histological evidence of tumor regression. SCCs treated in vitro with imiquimod also expressed vascular E-selectin. Approximately 50% of the T cells infiltrating untreated SCCs were FOXP3(+) regulatory T (T reg) cells. Imiquimod-treated tumors contained a decreased percentage of T reg cells, and these cells produced less FOXP3, interleukin (IL)-10, and transforming growth factor (TGF)-beta. Treatment of T reg cells in vitro with imiquimod inhibited their suppressive activity and reduced FOXP3, CD39, CD73, IL-10, and TGF-beta by indirect mechanisms. In vivo and in vitro treatment with imiquimod also induced IL-6 production by effector T cells. In summary, we find that SCCs evade the immune response at least in part by down-regulating vascular E-selectin and recruiting T reg cells. TLR7 agonists neutralized both of these strategies, supporting their use in SCCs and other tumors with similar immune defects.

Nature of inflammatory infiltrate in superficial cutaneous malignancies during topical imiquimod treatment

Topical imiquimod (IQ) is an effective treatment for genital warts and various malignant tumors of the skin. IQ acts through the Toll-like receptor 7 leading to the production of cytokines and chemokines such as interferons, interleukins, and growth factors. We investigated the composition of the inflammatory cell infiltrate before, during, and after the treatment of 10 superficial cutaneous malignancies (melanoma in situ (n = 4), melanoma metastasis (n = 1), squamous cell carcinoma in situ (n = 4), and basal cell carcinoma (n = 1) with 5% IQ cream. Immunophenotyping revealed in all cases during treatment an increased population of T-lymphocytes positive for CD3, CD4 and CD8, as well as a considerable number of cytotoxic cells (TIA-1+, granzyme B+) and plasmacytoid dendritic cells (CD 123+). These findings further support previous investigations that the antitumor effects of IQ result from an enhanced cytotoxic T-cell mediated immune response and from the recruitment of plasmacytoid dendritic cells to the skin. The population of infiltrative inflammatory cells was similar in all patients irrespective of the type of tumor.

Tumoricidal activity of TLR7/8-activated inflammatory dendritic cells

Imiquimod (IMQ), a synthetic agonist to Toll-like receptor (TLR) 7, is being successfully used for the treatment of certain skin neoplasms, but the exact mechanisms by which this compound induces tumor regression are not yet understood. While treating basal cell carcinoma (BCC) patients with topical IMQ, we detected, by immunohistochemistry, sizable numbers of both myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) within the inflammatory infiltrate. Surprisingly, peritumoral mDCs stained positive for perforin and granzyme B, whereas infiltrating pDCs expressed tumor necrosis factor–related apoptosis-inducing ligand (TRAIL). The biological relevance of this observation can be deduced from our further findings that peripheral blood–derived CD11c⁺ mDCs acquired antiperforin and anti–granzyme B reactivity upon TLR7/8 stimulation and could use these molecules to effectively lyse major histocompatibility complex (MHC) class I^lo cancer cell lines. The same activation protocol led pDCs to kill MHC class I–bearing Jurkat cells in a TRAIL-dependent fashion. While suggesting that mDCs and pDCs are directly involved in the IMQ-induced destruction of BCC lesions, our data also add a new facet to the functional spectrum of DCs, ascribing to them a major role not only in the initiation but also in the effector phase of the immune response.

Immune-mediated changes in actinic keratosis following topical treatment with imiquimod 5% cream

Background

The objective of this study was to identify the molecular processes responsible for the anti-lesional activity of imiquimod in subjects with actinic keratosis using global gene expression profiling.

Methods

A double-blind, placebo-controlled, randomized study was conducted to evaluate gene expression changes in actinic keratosis treated with imiquimod 5% cream. Male subjects (N = 17) with ≥ 5 actinic keratosis on the scalp applied placebo cream or imiquimod 3 times a week on nonconsecutive days for 4 weeks. To elucidate the molecular processes involved in actinic keratosis lesion regression by imiquimod, gene expression analysis using oligonucleotide arrays and real time reverse transcriptase polymerase chain reaction were performed on shave biopsies of lesions taken before and after treatment.

Results

Imiquimod modulated the expression of a large number of genes important in both the innate and adaptive immune response, including increased expression of interferon-inducible genes with known antiviral, anti-proliferative and immune modulatory activity, as well as various Toll-like receptors. In addition, imiquimod increased the expression of genes associated with activation of macrophages, dendritic cells, cytotoxic T cells, and natural killer cells, as well as activation of apoptotic pathways.

Conclusion

Data suggest that topical application of imiquimod stimulates cells in the skin to secrete cytokines and chemokines that lead to inflammatory cell influx into the lesions and subsequent apoptotic and immune cell-mediated destruction of lesions.

Apoptotic Responses in Squamous Carcinoma and Epithelial Cells to Small-Molecule Toll-like Receptor Agonists Evaluated with Automated Cytometry

The authors describe an assay to quantitate DNA fragmentation using terminal deoxynucleotidyl transferase-mediated deoxyuri-dine triphosphate nick end-labeling (TUNEL) stain, adapted to a 96-well microplate format for adherent cells, and an automated high-content screening imager. The apoptotic responses to actinomycin D (a known antineoplastic agent) to imiquimod (a small-molecule toll-like receptor [TLR] 7 agonist used in skin cancer treatment) and to several structurally related TLR 7/8 agonists were evaluated in squamous carcinoma SCC15 and SCC25 cells and normal human keratinocytes. Potent proapoptotic and growth-impairing (as determined by reduced cell numbers) actions of actinomycin D (1-300 ng/mL) were discerned with the assay. Consistent with previous reports, imiquimod (at 300 μM; ∼75 μg/mL) induced TUNEL positivity of malignant cell cultures, but this effect also occurred in normal keratinocytes. Two related TLR agonists induced apoptosis at lower concentrations. However, the concentrations of these and the imiquimod necessary to elicit cancer cell apoptosis were 300 to 1000 times higher relative to their ability to induce the secretion of an antineoplastic protein, interferon-α, from human blood monocytes. This TUNEL analysis allows the quantitative comparison of compounds’ apoptotic activity toward adherent malignant and normal cells and may be useful for hit characterization after a screen.

Imiquimod-induced regression of actinic keratosis is associated with infiltration by T lymphocytes and dendritic cells: a randomized controlled trial

BACKGROUND

Imiquimod 5% cream is a topically applied immune response modifier that has been shown to give effective treatment of actinic keratosis (AK). The therapeutic effects of imiquimod are likely to involve the provocation of a cutaneous immune response against abnormal cells, an assumption based on a strong correlation between complete clearance rates and the severity of the local skin reactions (erythema, oedema, erosion/ulceration, weeping/exudation and scabbing/crusting); however, no clinical studies have conclusively proved this mechanism.

OBJECTIVES

To determine the nature of cellular infiltrates induced by the application of imiquimod to AK lesions and to study cells involved in the cutaneous immune response.

METHODS

Eighteen patients participated in this phase I, randomized, double-blind, parallel group, vehicle-controlled study. Enrolled patients were randomized in a 2 : 1 ratio to receive imiquimod cream or vehicle cream and applied study cream to five lesions on the scalp, forearm or upper trunk once daily, three days per week for up to 16 weeks. Each patient had punch biopsies of two distinct AK lesions: a lesion was biopsied before treatment to obtain baseline biomarker levels, and a different lesion was biopsied after 2 weeks of treatment. Biopsy specimens were examined using routine and immunohistochemical staining.

RESULTS

The imiquimod group showed statistically significant increases from baseline to week 2 in tissue biomarker levels for CD3, CD4, CD8, CD11c, CD86/CD11c, CD68, HLA-DR and TUNEL. No significant differences were seen for the vehicle group. Complete clearance of all treated AK lesions was achieved in five of 11 (45%) imiquimod patients and in none of six vehicle patients.

CONCLUSIONS

Imiquimod stimulates a cutaneous immune response characterized by increases in activated dendritic cells and CD4+ and CD8+ T cells.