Imiquimod induced regression of clinically diagnosed superficial basal cell carcinoma is associated with early infiltration by CD4 T cells and dendritic cells

Immunotherapy for keratinocyte cancers. Part I: Immune-related epidemiology, risk factors, pathogenesis, and immunotherapy management of keratinocyte cancers

The important role of the immune system in the surveillance and control of keratinocyte cancers (KCs), namely squamous and basal cell carcinomas, is increasingly appreciated, as new immunotherapies have recently become available. As the field of immunotherapy is rapidly evolving, this review synthesizes key concepts and highlights important cellular components within the immune system responsible for attacking KCs. We review the most current data on the epidemiology, risk factors, and immunotherapy management for KCs. Patients will seek advice from dermatologists to help explain why immunotherapies work for KCs and whether they might be appropriate for different clinical scenarios. Collaboration with medical colleagues across different disciplines to evaluate KCs for response to immunotherapy and early recognition of immune-related adverse events will help to optimize patient outcomes.

Pre-existing inflammatory immune microenvironment predicts the clinical response of vulvar high-grade squamous intraepithelial lesions to therapeutic HPV16 vaccination

BACKGROUND

Vulvar high-grade squamous intraepithelial lesion (vHSIL) is predominantly induced by high-risk human papilloma virus type 16 (HPV16). In two independent trials, therapeutic vaccination against the HPV16 E6 and E7 oncoproteins resulted in objective partial and complete responses (PRs/CRs) in half of the patients with HPV16+ vHSIL at 12-month follow-up. Here, the prevaccination and postvaccination vHSIL immune microenvironment in relation to the vaccine-induced clinical response was investigated.

METHODS

Two novel seven-color multiplex immunofluorescence panels to identify T cells (CD3, CD8, Foxp3, Tim3, Tbet, PD-1, DAPI) and myeloid cells (CD14, CD33, CD68, CD163, CD11c, PD-L1, DAPI) were designed and fully optimized for formalin-fixed paraffin-embedded tissue. 29 prevaccination and 24 postvaccination biopsies of patients with vHSIL, and 27 healthy vulva excisions, were stained, scanned with the Vectra multispectral imaging system, and automatically phenotyped and counted using inForm advanced image analysis software.

RESULTS

Healthy vulvar tissue is strongly infiltrated by CD4 and CD8 T cells expressing Tbet and/or PD-1 and CD14+HLA-DR+ inflammatory myeloid cells. The presence of such a coordinated pre-existing proinflammatory microenvironment in HPV16+ vHSIL is associated with CR after vaccination. In partial responders, a disconnection between T cell and CD14+ myeloid cell infiltration was observed, whereas clinical non-responders displayed overall lower immune cell infiltration. Vaccination improved the coordination of local immunity, reflected by increased numbers of CD4+Tbet+ T cells and HLA-DR+CD14+ expressing myeloid cells in patients with a PR or CR, but not in patients with no response. CD8+ T cell infiltration was not increased after vaccination.

CONCLUSION

A prevaccination inflamed type 1 immune contexture is required for stronger vaccine-induced immune infiltration and is associated with better clinical response. Therapeutic vaccination did not overtly increase immune infiltration of cold lesions.

Intratumoral immunotherapy with TLR7/8 agonist MEDI9197 modulates the tumor microenvironment leading to enhanced activity when combined with other immunotherapies

Background

Immune checkpoint blockade (ICB) promotes adaptive immunity and tumor regression in some cancer patients. However, in patients with immunologically “cold” tumors, tumor-resident innate immune cell activation may be required to prime an adaptive immune response and so exploit the full potential of ICB. Whilst Toll-like receptor (TLR) agonists have been used topically to successfully treat some superficial skin tumors, systemic TLR agonists have not been well-tolerated.

Methods

The response of human immune cells to TLR7 and 8 agonism was measured in primary human immune cell assays. MEDI9197 (3M-052) was designed as a novel lipophilic TLR7/8 agonist that is retained at the injection site, limiting systemic exposure. Retention of the TLR7/8 agonist at the site of injection was demonstrated using quantitative whole-body autoradiography, HPLC-UV, and MALDI mass spectrometry imaging. Pharmacodynamic changes on T cells from TLR7/8 agonist treated B16-OVA tumors was assessed by histology, quantitative real time PCR, and flow cytometry. Combination activity of TLR7/8 agonism with immunotherapies was assessed in vitro by human DC-T cell MLR assay, and in vivo using multiple syngeneic mouse tumor models.

Results

Targeting both TLR7 and 8 triggers an innate and adaptive immune response in primary human immune cells, exemplified by secretion of IFNα, IL-12 and IFNγ. In contrast, a STING or a TLR9 agonist primarily induces release of IFNα. We demonstrate that the TLR7/8 agonist, MEDI9197, is retained at the sight of injection with limited systemic exposure. This localized TLR7/8 agonism leads to Th1 polarization, enrichment and activation of natural killer (NK) and CD8⁺ T cells, and inhibition of tumor growth in multiple syngeneic models. The anti-tumor activity of this TLR7/8 agonist is enhanced when combined with T cell-targeted immunotherapies in pre-clinical models.

Conclusion

Localized TLR7/8 agonism can enhance recruitment and activation of immune cells in tumors and polarize anti-tumor immunity towards a Th1 response. Moreover, we demonstrate that the anti-tumor effects of this TLR7/8 agonist can be enhanced through combination with checkpoint inhibitors and co-stimulatory agonists.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0724-8) contains supplementary material, which is available to authorized users.

Regression of Periocular Basal Cell Carcinoma: A Report of Four Cases with Clinicopathologic Correlation

Objectives

To describe the spectrum of clinical and histopathological features of a case series of basal cell carcinoma (BCC) with spontaneous regression and to discuss this phenomenon.

Method

Four cases of BCC with complete/substantial regression were retrospectively identified. Patients' records were analyzed for demographic data, clinical appearance, and the postoperative course. Formalin-fixed, paraffin-embedded specimens were routinely processed and stained with hematoxylin and eosin and periodic acid Schiff.

Results

Complete (n = 1) or partial (n = 3) regression of BCC was observed in 4 patients. Two lesions at the medial canthus were histologically diagnosed as nodular BCC with significant regression. One lesion at the lower eyelid exhibited a complete regression which did not require surgical intervention. The other lesion at the lower eyelid presenting with ulceration and madarosis was excised. Scar tissue without evidence for a neoplasm was present histologically. Subsequently, the patient developed a recurrence with a histologically proven micronodular BCC.

Conclusions

BCC can show spontaneous substantial or complete regression. Histological tumor absence in lesions which are clinically suspicious for a neoplasm can be a hint for a regressive BCC. Recurrences may develop from remaining tumor islands warranting periodical clinical visits in cases of clinically as well as histologically suspected regressive BCC.

Transcriptome and proteome profiling reveals stress-induced expression signatures of imiquimod-treated Tasmanian devil facial tumor disease (DFTD) cells

As a topical cancer immunotherapy, the toll-like receptor 7 ligand imiquimod activates tumor regression via stimulation of immune cell infiltration and cytotoxic responses. Imiquimod also exerts direct pro-apoptotic effects on tumor cells in vitro, but a role for these effects in imiquimod-induced tumor regression remains undefined. We previously demonstrated that cell lines derived from devil facial tumor disease (DFTD), a transmissible cancer threatening the survival of the Tasmanian devil (Sarcophilus harrisii), are sensitive to imiquimod-induced apoptosis. In this study, the pro-apoptotic effects of imiquimod in DFTD have been investigated using RNA-sequencing and label-free quantitative proteomics. This analysis revealed that changes to gene and protein expression in imiquimod treated DFTD cells are consistent with the onset of oxidative and endoplasmic reticulum stress responses, and subsequent activation of the unfolded protein response, autophagy, cell cycle arrest and apoptosis. Imiquimod also regulates the expression of oncogenic pathways, providing a direct mechanism by which this drug may increase tumor susceptibility to immune cytotoxicity in vivo. Our study has provided the first global analysis of imiquimod-induced effects in any tumor cell line. These findings have highlighted the potential of cell stress pathways as therapeutic targets in DFTD, and will allow for improved mechanistic use of imiquimod as a therapy in both the Tasmanian devil and human cancers.

The Immunomodulatory Small Molecule Imiquimod Induces Apoptosis in Devil Facial Tumour Cell Lines

The survival of the Tasmanian devil (Sarcophilus harrisii) is threatened by devil facial tumour disease (DFTD). This transmissible cancer is usually fatal, and no successful treatments have been developed. In human studies, the small immunomodulatory molecule imiquimod is a successful immunotherapy, activating anti-tumour immunity via stimulation of toll-like receptor-7 (TLR7) signaling pathways. In addition, imiquimod is a potent inducer of apoptosis in human tumour cell lines via TLR7 independent mechanisms. Here we investigate the potential of imiquimod as a DFTD therapy through analysis of treated DFTD cell lines and Tasmanian devil fibroblasts. WST-8 proliferation assays and annexin V apoptosis assays were performed to monitor apoptosis, and changes to the expression of pro- and anti-apoptotic genes were analysed using qRT-PCR. Our results show that DFTD cell lines, but not Tasmanian devil fibroblasts, are sensitive to imiquimod-induced apoptosis in a time and concentration dependent manner. Induction of apoptosis was accompanied by down-regulation of the anti-apoptotic BCL2 and BCLX_L genes, and up-regulation of the pro-apoptotic BIM gene. Continuous imiquimod treatment was required for these effects to occur. These results demonstrate that imiquimod can deregulate DFTD cell growth and survival in direct and targeted manner. In vivo, this may increase DFTD vulnerability to imiquimod-induced TLR7-mediated immune responses. Our findings have improved the current knowledge of imiquimod action in tumour cells for application to both DFTD and human cancer therapy.

The use of reflectance confocal microscopy for monitoring response to therapy of skin malignancies

SUMMARY

Reflectance confocal microscopy (RCM) is a new non-invasive imaging technique that enables visualizing cells and structures in living skin in real-time with resolution close to that of histological analysis. RCM has been successfully implemented in the assessment of benign and malignant lesions. Most importantly, it also enables monitoring dynamic changes in the skin over time and in response to different therapies, e.g., imiquimod, photodynamic therapy, and others. Given the often traumatic nature of skin cancer that affects both the physiology and the psychology of the patients, it is crucial to have methods that enable monitoring the response to treatment but that minimize the distress and discomfort associated with such process. This article provides a very brief overview of the fundamentals of RCM and then focuses on its recent employment as a monitoring tool in skin cancer and other pathologies that may require frequent follow-up.

The mechanisms and consequences of ultraviolet-induced immunosuppression in the skin and eye

Ultraviolet radiation (UVR) of the skin results in immune suppression to antigens encountered shortly after the exposure. The pathways leading to the downregulation in immunity are complex, initiated by chromophores located at the surface of the skin and ending with the generation of immunosuppressive mediators and regulatory cells. Ultraviolet-induced immunosuppression can be considered not only as beneficial, such as in preventing chronic inflammatory responses and allergic and automimmune reactions, but it can also be detrimental, such as in the lack of control of skin tumors and infectious diseases. The eye is an immune privileged site through a wide variety of mechanisms that allow selected immune responses without causing inflammation. The role of UVR in altering immune responses in the eye is not clear and is discussed in relation to photokeratitis, herpetic stromal keratitis, and pterygium.

Immunomodulation by imiquimod in patients with high-risk primary melanoma

Imiquimod is a synthetic Toll-like receptor 7 (TLR7) agonist approved for the topical treatment of actinic keratoses, superficial basal cell carcinoma, and genital warts. Imiquimod leads to an 80–100% cure rate of lentigo maligna, but studies of invasive melanoma are lacking. We conducted a pilot study to characterize the local, regional, and systemic immune responses induced by imiquimod in patients with high-risk melanoma. After treatment of the primary melanoma biopsy site with placebo or imiquimod cream, we measured immune responses in the treated skin, sentinel lymph nodes (SLN), and peripheral blood. Treatment of primary melanomas with 5% imiquimod cream was associated with an increase in both CD4+ and CD8+ T cells in the skin, and CD4+ T cells in the SLN. Most of the CD8+ T cells in the skin were CD25 negative. We could not detect any increases in CD8+ T cells specifically recognizing HLA-A*0201-restricted melanoma epitopes in the peripheral blood. The findings from this small pilot study demonstrate that topical imiquimod treatment results in enhanced local and regional T cell numbers in both the skin and SLN. Further research into TLR7 immunomodulating pathways as a basis for effective immunotherapy against melanoma in conjunction with surgery is warranted.

Lupus erythematosus-like imiquimod reaction: a diagnostic pitfall

Imiquimod (AldaraTM), a Toll-like receptor 7 agonist (TLR7), is known for its unique properties of being an immune response modifier and stimulator. Upon topical application, this TLR7 agonist triggers a cell-mediated immune response predominantly expressed by dendritic cells and monocytes. Local skin irritation at the application site involving erythema, pain, crusting and erosions is common and well documented. On the contrary, the specific histopathologic features associated with these treatment site reactions is not. Herein reported is a case where historical omission of imiquimod use for actinic keratosis complicated the histologic interpretation. We highlight a lupus erythematosus-like microscopic pattern and explore histopathologic features that could help in avoiding a diagnostic pitfall, as well as the relationship between TLR activation, cell-mediated immunity and skin histology.

Update on vaccine development for renal cell cancer

Renal cell carcinoma (RCC) remains a significant health concern that frequently presents as metastatic disease at the time of initial diagnosis. Current first-line therapeutics for the advanced-stage RCC include antiangiogenic drugs that have yielded high rates of objective clinical response; however, these tend to be transient in nature, with many patients becoming refractory to chronic treatment with these agents. Adjuvant immunotherapies remain viable candidates to sustain disease-free and overall patient survival. In particular, vaccines designed to optimize the activation, maintenance, and recruitment of specific immunity within or into the tumor site continue to evolve. Based on the integration of increasingly refined immunomonitoring systems in both translational models and clinical trials, allowing for the improved understanding of treatment mechanism(s) of action, further refined (combinational) vaccine protocols are currently being developed and evaluated. This review provides a brief history of RCC vaccine development, discusses the successes and limitations in such approaches, and provides a rationale for developing combinational vaccine approaches that may provide improved clinical benefits to patients with RCC.

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.

Tumor stroma-derived Wnt5a induces differentiation of basal cell carcinoma of Ptch-mutant mice via CaMKII

Basal cell carcinoma (BCC) is the most common skin tumor in humans. Although BCCs rarely metastasize, they can cause significant morbidity due to local aggressiveness. Approximately 20% of BCCs show signs of spontaneous regression. The understanding of molecular events mediating spontaneous regression has the potential to reduce morbidity of BCC and, potentially, other tumors, if translated into tumor therapies. We show that BCCs induced in conditional Ptch(flox/flox)ERT2(+/-) knockout mice regress with time and show a more differentiated phenotype. Differentiation is accompanied by Wnt5a expression in the tumor stroma, which is first detectable at the fully developed tumor stage. Coculture experiments revealed that Wnt5a is upregulated in tumor-adjacent macrophages by soluble signals derived from BCC cells. In turn, Wnt5a induces the expression of the differentiation marker K10 in tumor cells, which is mediated by Wnt/Ca(2+) signaling in a CaMKII-dependent manner. These data support a role of stromal Wnt5a in BCC differentiation and regression, which may have important implications for development of new treatment strategies for this tumor. Taken together, our results establish BCC as an easily accessible model of tumor regression. The regression of BCC despite sustained Hedgehog signaling activity seems to be mediated by tumor-stromal interactions via Wnt5a signaling.

Intravesical Toll-like receptor 7 agonist R-837: optimization of its formulation in an orthotopic mouse model of bladder cancer

OBJECTIVE

To study the immune response caused by the intravesical administration of the immunomodulator R-837 in various formulations and to estimate its therapeutic potential for bladder cancer.

METHODS

Female C57BL/6 mice were intravesically treated with different formulations of R-837, a Toll-like receptor 7 agonist used for treating genital warts and skin malignancy. The tested formulation mixtures contained different ratios of lactic acid, a thermosensitive poloxamer polymer (Lutrol F127) and 2-(hydroxypropyl)-beta-cyclodextrin (HPbetaCD). Induction of tumor necrosis factor alpha (TNFalpha) and keratinocyte-derived chemokine (KC) was analyzed by Luminex microbeads assay. The therapeutic potential of intravesical administration of R-837 was assessed in an orthotopic, syngeneic mouse model of bladder cancer using MB49 cells.

RESULTS

Intravesical administration of R-837 in lactic acid alone induced systemic and bladder TNFalpha and KC in a dose-dependent manner. Formulations including poloxamer decreased systemic absorption of R-837 and significantly reduced systemic and local induction of KC. Addition of HPbetaCD in the poloxamer formulation particularly reversed levels of systemic and local levels of TNFalpha and KC. Histological examination showed that poloxamer-HPbetaCD formulation allowed infiltration of mononuclear cells into urothelium and lamina propria. In studies using orthotopic mouse bladder cancer, the tumor loads in R-837-treated mice were significantly lower than those in vehicle-treated or non-treated mice.

CONCLUSION

The optimized poloxamer-HPbetaCD formulation of R-837 shows therapeutic potential for bladder cancer while avoiding adverse side-effects.

In vivo characterization of the inflammatory infiltrate and apoptotic status in imiquimod-treated basal cell carcinoma

BACKGROUND

Imiquimod use in the treatment of basal cell carcinoma (BCC) has proven to be successful in a large percentage of cases, inducing tumor regression; however, the exact cellular mechanism has not been fully clarified.

AIM

To measure the morphological changes in the tumor microenvironment and the markers of apoptosis in skin biopsies from patients with BCC before and after imiquimod treatment.

METHODS

In this open label study, skin biopsies obtained from 11 patients with BCC were evaluated before and after imiquimod treatment for: (i) morphological changes in the tumor microenvironment, with specific emphasis on the immunophenotype of inflammatory cells around the tumor; and (ii) markers of apoptosis, including expression of death receptors.

RESULTS

Imiquimod treatment induced a significant increase in the mononuclear inflammatory response. In the majority of cases, the cellular infiltrate was predominantly composed of CD3(+)/CD4(+) T cells, suggesting that the effector response is mediated by CD3(+)/CD4(+) lymphocytes, with a minor cytotoxic and natural killer (NK) component. An increase in the cytotoxic CD3(+)/CD8(+) T-cell population was also observed. Imiquimod treatment was associated with a marked increased in CD20(+) B cells, and a less pronounced enhancement in cells of monocyte-macrophage origin (CD68(+)) surrounding, or within, the tumor. This finding indicates either that macrophages play a minor role in the imiquimod-induced response, or the recruitment of these cells is related to time and dose. Imiquimod treatment decreased CD1A(+) Langerhans cells in the epidermis and increased the number of CD1A(+) dendritic cells within the tumor aggregates. Imiquimod reduced Bcl-2 expression, but no difference was found in Bax, Fas/FasL, and p53 expression in BCC cells.

CONCLUSIONS

Our results support the hypothesis that imiquimod activity in the treatment of BCC is partly a result of a pro-inflammatory action mediated by CD3(+)/CD4(+) lymphoid cells and of a pro-apoptotic activity associated with decreased Bcl-2 expression.

Transforming growth factor-beta1-mediated Slug and Snail transcription factor up-regulation reduces the density of Langerhans cells in epithelial metaplasia by affecting E-cadherin expression

Epithelial metaplasia (EpM) is an acquired tissue abnormality resulting from the transformation of epithelium into another tissue with a different structure and function. This adaptative process is associated with an increased frequency of (pre)cancerous lesions. We propose that EpM is involved in cancer development by altering the expression of adhesion molecules important for cell-mediated antitumor immunity. Langerhans cells (LCs) are intraepithelial dendritic cells that initiate immune responses against viral or tumor antigens on both skin and mucosal surfaces. In the present study, we showed by immunohistology that the density of CD1a(+) LCs is reduced in EpM of the uterine cervix compared with native squamous epithelium and that the low number of LCs observed in EpM correlates with the down-regulation of cell-surface E-cadherin. We also demonstrated that transforming growth factor-beta1 is not only overexpressed in metaplastic tissues but also reduces E-cadherin expression in keratinocytes in vitro by inducing the promoter activity of Slug and Snail transcription factors. Finally, we showed that in vitro-generated LCs adhere poorly to keratinocytes transfected with either Slug or Snail DNA. These data suggest that transforming growth factor-beta1 indirectly reduces antigen-presenting cell density in EpM by affecting E-cadherin expression, which might explain the increased susceptibility of abnormal tissue differentiation to the development of cancer by the establishment of local immunodeficiency responsible for EpM tumorigenesis.

Resiquimod and other immune response modifiers as vaccine adjuvants

Synthetic immune response modifiers, such as resiquimod, are Toll-like receptor 7 and 8 agonists that act as vaccine adjuvants, enhancing antigen-specific antibody production and skewing immunity towards a Th1 response. These compounds stimulate dendritic cells to secrete cytokines, upregulate costimulatory molecule expression and enhance antigen presentation to T cells. The compounds have demonstrated vaccine adjuvant properties in a number of animal models. The adjuvant effects can be enhanced by measures that allow the drug to stay localized with the vaccine without quickly entering the systemic circulation. Clinical studies demonstrate that topical application of resiquimod and analogs is safe and effective at activating the local immune response. For injection, resiquimod or a similar compound may need to be formulated to allow for local immune activation without induction of systemic cytokines.

Possible mechanisms in the induction of vitiligo-like hypopigmentation by topical imiquimod

The pathogenesis of vitiligo was examined for clues to the pigmentary changes that may occur after treatment with topical imiquimod. The literature varies on the pigmentary changes induced by topical use of imiquimod. The US Food and Drugs Administration lists 68 reports of pigmentary changes out of a total of 1257 reports related to imiquimod lodged from 1997 to 2003. Some studies describe vitiligo-like hypopigmentation associated with imiquimod treatment of genital warts (as with the patient described in this report), molluscum contagiosum, basal cell carcinoma, extramammary Paget's disease and murine melanoma. Other studies report hyperpigmentation associated with imiquimod. The possible mechanisms of hypopigmentation associated with imiquimod treatment are discussed, including antibodies found in sera of patients with vitiligo to nonpigment cell antigens, cytoplasmic pigment cell antigens and pigment cell-surface antigens; stimulation by imiquimod of both the innate immune response and cell-mediated adaptive immunity; and increased sensitivity of melanocytes to oxidative stress. The vitiligo-like hypopigmentation following topical imiquimod treatment is in line with the mode of action of this drug.

Immune cell recruitment and cell-based system for cancer therapy

Immune cells, such as cytotoxic T lymphocytes, natural killer cells, B cells, and dendritic cells, have a central role in cancer immunotherapy. Conventional studies of cancer immunotherapy have focused mainly on the search for an efficient means to prime/activate tumor-associated antigen-specific immunity. A systematic understanding of the molecular basis of the trafficking and biodistribution of immune cells, however, is important for the development of more efficacious cancer immunotherapies. It is well established that the basis and premise of immunotherapy is the accumulation of effective immune cells in tumor tissues. Therefore, it is crucial to control the distribution of immune cells to optimize cancer immunotherapy. Recent characterization of various chemokines and chemokine receptors in the immune system has increased our knowledge of the regulatory mechanisms of the immune response and tolerance based on immune cell localization. Here, we review the immune cell recruitment and cell-based systems that can potentially control the systemic pharmacokinetics of immune cells and, in particular, focus on cell migrating molecules, i.e., chemokines, and their receptors, and their use in cancer immunotherapy.

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.

Papanicolaou smears and cervical inflammatory cytokine responses

In a case-control study among 2064 South African women to investigate the risk of clinically invasive cancer of the cervix, we found a marked reduction in the risk of cervical cancer among women who gave a history of ever having undergone even a single Pap smear, and a statistically significant decline in the HPV positivity rate correlated with the lifetime number of Pap smears received. HPV infections and their associated low-grade lesions commonly regress, indicating that most often there is an effective host immune response against HPV infection. We hypothesized that act of performing a Pap smear is associated with inflammatory responses at the site of trauma, the cervix, and that this inflammatory signalling may be an immunological factor initiating these productive anti-HPV responses. In the present study, a randomized controlled trial, we enrolled 80 healthy young women to investigate the impact of performing a Pap smear on cervical inflammation. Forty one women, in the intervention group, received a Pap smear at enrollment and cervicovaginal lavages (CVLs) were collected at baseline and 2 weeks later. Thirty nine women received no intervention at enrollment (control group) but CVLs were collected at enrolment and 2 weeks later. We assessed various markers of inflammation including IL-12 p70, TNF-α, IL-8, IL-6, IL-10, and IL-1β in CVL specimens. While CVL levels of IL-8, IL-1β and IL-6 remained unchanged following a Pap smear, markers of cell mediated immunity (IL-12 p70 and TNF-α) and T cell regulation (IL-10) were significantly elevated.

Targeting HER-2/neu in Early Breast Cancer Development Using Dendritic Cells with Staged Interleukin-12 Burst Secretion

Overexpression of HER-2/neu (c-erbB2) is associated with increased risk of recurrent disease in ductal carcinoma in situ (DCIS) and a poorer prognosis in node-positive breast cancer. We therefore examined the early immunotherapeutic targeting of HER-2/neu in DCIS. Before surgical resection, HER-2/neu(pos) DCIS patients (n = 13) received 4 weekly vaccinations of dendritic cells pulsed with HER-2/neu HLA class I and II peptides. The vaccine dendritic cells were activated in vitro with IFN-gamma and bacterial lipopolysaccharide to become highly polarized DC1-type dendritic cells that secrete high levels of interleukin-12p70 (IL-12p70). Intranodal delivery of dendritic cells supplied both antigenic stimulation and a synchronized preconditioned burst of IL-12p70 production directly to the anatomic site of T-cell sensitization. Before vaccination, many subjects possessed HER-2/neu-HLA-A2 tetramer-staining CD8(pos) T cells that expressed low levels of CD28 and high levels of the inhibitory B7 ligand CTLA-4, but this ratio inverted after vaccination. The vaccinated subjects also showed high rates of peptide-specific sensitization for both IFN-gamma-secreting CD4(pos) (85%) and CD8(pos) (80%) T cells, with recognition of antigenically relevant breast cancer lines, accumulation of T and B lymphocytes in the breast, and induction of complement-dependent, tumor-lytic antibodies. Seven of 11 evaluable patients also showed markedly decreased HER-2/neu expression in surgical tumor specimens, often with measurable decreases in residual DCIS, suggesting an active process of "immunoediting" for HER-2/neu-expressing tumor cells following vaccination. DC1 vaccination strategies may therefore have potential for both the prevention and the treatment of early breast cancer.

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.

Immune response modifiers--mode of action

The innate immune system governs the interconnecting pathways of microbial recognition, inflammation, microbial clearance, and cell death. A family of evolutionarily conserved receptors, known as the Toll-like receptors (TLRs), is crucial in early host defense against invading pathogens. Upon TLR stimulation, nuclear factor-kappaB activation and the interferon (IFN)-regulatory factor 3 pathway initiate production of pro-inflammatory cytokines, such as interleukin-1 and tumor necrosis factor-alpha, and production of type I IFNs (IFN-alpha and IFN-beta), respectively. The innate immunity thereby offers diverse targets for highly selective therapeutics, such as small molecular synthetic compounds that modify innate immune responses. The notion that activation of the innate immune system is a prerequisite for the induction of acquired immunity raised interest in these immune response modifiers as potential therapeutics for viral infections and various tumors. A scenario of dermal events following skin cancer treatment with imiquimod presumably comprises (i) an initial low amount of pro-inflammatory cytokine secretion by macrophages and dermal dendritic cells (DCs), thereby (ii) attracting an increasing number type I IFN-producing plasmacytoid DCs (pDCs) from the blood; (iii) Langerhans cells migrate into draining lymph nodes, leading to an increased presentation of tumor antigen in the draining lymph node, and (iv) consequently an increased generation of tumor-specific T cells and finally (v) an accumulation of tumoricidal effector cells in the treated skin area. The induction of predominately T helper (Th)1-type cytokine profiles by TLR agonists such as imiquimod might have further benefits by shifting the dominant Th2-type response in atopic diseases such as asthma and atopic dermatitis to a more potent Th1 response.

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.

The TLR-7 agonist, imiquimod, enhances dendritic cell survival and promotes tumor antigen-specific T cell priming: relation to central nervous system antitumor immunity

Immunotherapy represents an appealing option to specifically target CNS tumors using the immune system. In this report, we tested whether adjunctive treatment with the TLR-7 agonist imiquimod could augment antitumor immune responsiveness in CNS tumor-bearing mice treated with human gp100 + tyrosine-related protein-2 melanoma-associated Ag peptide-pulsed dendritic cell (DC) vaccination. Treatment of mice with 5% imiquimod resulted in synergistic reduction in CNS tumor growth compared with melanoma-associated Ag-pulsed DC vaccination alone. Continuous imiquimod administration in CNS tumor-bearing mice, however, was associated with the appearance of robust innate immune cell infiltration and hemorrhage into the brain and the tumor. To understand the immunological mechanisms by which imiquimod augmented antitumor immunity, we tested whether imiquimod treatment enhanced DC function or the priming of tumor-specific CD8+ T cells in vivo. With bioluminescent, in vivo imaging, we determined that imiquimod dramatically enhanced both the persistence and trafficking of DCs into the draining lymph nodes after vaccination. We additionally demonstrated that imiquimod administration significantly increased the accumulation of tumor-specific CD8+ T cells in the spleen and draining lymph nodes after DC vaccination. The results suggest that imiquimod positively influences DC trafficking and the priming of tumor-specific CD8+ T cells. However, inflammatory responses induced in the brain by TLR signaling must also take into account the local microenvironment in the context of antitumor immunity to induce clinical benefit. Nevertheless, immunotherapeutic targeting of malignant CNS tumors may be enhanced by the administration of the innate immune response modifier imiquimod.

Disease-Independent Skin Recruitment and Activation of Plasmacytoid Predendritic Cells Following Imiquimod Treatment

BACKGROUND

Imiquimod, an immune response modifier that is used topically to treat different types of skin cancer, induces the production of proinflammatory cytokines that stimulate an antitumor immune response. We assessed characteristics of the imiquimod-induced immune activation in epithelial and lymphoproliferative neoplasias of human skin. We focused on plasmacytoid predendritic cells (PDCs), the primary producer of interferon alpha (IFN-alpha) after imiquimod activation in vitro.

METHODS

We used Affymetrix oligonucleotide arrays to compare gene expression profiles from tumors from 16 patients, 10 with superficial basal cell carcinomas (sBCCs), five with cutaneous T-cell lymphomas (CTCLs), and one with Bowen's disease, before and after topical imiquimod treatment. We used quantitative immunohistochemistry with PDC-specific antibodies against BDCA-2 and CD123 to characterize the PDC population before and after imiquimod treatment in these specimens. Activation status of PDCs from four sBCC patients was assessed by intracellular IFN-alpha staining and flow cytometry.

RESULTS

Expression of various IFN-alpha-inducible genes (e.g., CIG5, G1P2, OASL, IFIT1, STAT1, IFI35, OAS1, ISG20, MxA, and IRF7), the so-called IFN-alpha signature, was increased similarly in both sBCC and CTCL lesions after imiquimod treatment. PDCs were recruited and activated in both lesion types, and they produced IFN-alpha after imiquimod treatment in vivo (mean percentage of PDCs producing IFN-alpha = 14.5%, 95% confidence interval [CI] = 4.9% to 24%; range = 3.3%-27%, n = 4 lesions). Imiquimod induced similar immune activation patterns in all three diseases, and these patterns were associated with the number of PDCs recruited to the treatment site. Two imiquimod-treated sBCC patients who did not mount an inflammatory response to imiquimod and whose lesions lacked the IFN-alpha signature after treatment had fewer PDCs in treated lesions compared with other treated patients with such a response.

CONCLUSIONS

Imiquimod induces immune activation patterns that relate to the number of the PDCs recruited to the treatment site, thus supporting the role of PDC in responsiveness to imiquimod in humans.