Expression of PD-L1 in keratoacanthoma and different stages of progression in cutaneous squamous cell carcinoma

Immune checkpoint inhibitors for children with xeroderma pigmentosum and advanced cutaneous squamous cell carcinoma: A case presentation and brief review

Patients with xeroderma pigmentosum (XP) frequently develop skin cancers early in life, including cutaneous squamous cell carcinoma (cSCC). The median age of death is 32 years and 60% of XP patients die before the age of 20 years. cSCC in patients with XP exhibits an exceptionally high mutation burden, suggesting a favorable response to immune checkpoint inhibitors (ICIs). We present the case of a 7-year-old boy with XP and a large facial cSCC complicated by cervical lymph node metastases. Following a tumor board recommendation, systemic immunotherapy with cemiplimab was initiated. Following therapy, the tumors rapidly and completely regressed. To date, only 10 XP patients worldwide have been reported to receive ICIs for inoperable and/or advanced cSCC, with all cases demonstrating tumor regression under ICI treatment. Among these, three were pediatric cases with XP-C (one 7-year-old and two 6-year-old children), one of whom had sarcomatoid cSCC. Incidence and nature of adverse events in XP patients were comparable to those observed in the general population. In line with the previously reported ICI-treated XP children, the present case confirms that anti-PD-1 inhibitors are highly effective in children with XP and advanced cSCC.

Low Intratumoral CD200 Protein Expression in Primary Merkel Cell Carcinoma Is a Strong Predictor for Disease Relapse

BACKGROUND

Merkel cell carcinoma (MCC) is a rare and frequently fatal form of skin cancer. Apart from Programmed Cell Death Protein 1 (PD-1)/Programmed Death-Ligand 1 (PD-L1) signaling, there is a lack of knowledge regarding other immune checkpoint molecules. Recent studies have observed elevated glycoprotein CD200 (also known as OX-2) mRNA expression in in different types of tumors, with CD200R-expressing myeloid cells present in the tumor microenvironment. However, the potential role of the CD200/CD200 axis as an additional checkpoint modulator remains widely unexplored. The aim of this study was to determine the intratumoral protein expression of CD200 as well as CD200R in a larger cohort of MCC patients and to correlate the expression levels with patients' outcomes.

METHODS

In this multicenter study, we investigated 68 patients with MCC (68 primary tumors and 15 corresponding metastases). Immunohistochemistry (IHC) was performed for CD200 as well as CD200R. Digital quantification and analysis of IHC were performed using QuPath-0.2.3.

RESULTS

CD200 and CD200R expression was observed in 100% of cases. Univariate analysis revealed that low CD200 expression in primary tumors (p = 0.0007, HR 9.35), male sex (p = 0.045, HR 2.41), and immunosuppression (p = 0.0031, HR 6.36) were significantly associated with MCC relapse. Low CD200 expression was also linked to prior immune checkpoint inhibitors (ICI) and/or chemotherapy treatment (p = 0.037). Multivariable analysis confirmed that low CD200 expression (p = 0.0012, HR 5.25) and immunosuppression (p = 0.0056, HR 4.11) were independent predictors of MCC relapse.

CONCLUSIONS

Expression of CD200/CD200R proteins is very high in MCC and may thus be of diagnostic value. More importantly, low intratumoral CD200 protein expression in primary MCC represents a robust independent predictor of MCC relapse.

FGFR2 in the Development and Progression of Cutaneous Squamous Cell Cancer

Cutaneous squamous cell carcinoma (cSCC) is an increasingly common malignancy of the skin and the leading cause of death from skin cancer in adults over the age of 85. Fibroblast growth factor receptor 2 (FGFR2) has been identified as an important effector of signaling pathways that lead to the growth and development of cSCC. In recent years, there have been numerous studies evaluating the role FGFR2 plays in multiple cancers, its contribution to resistance to anticancer therapy, and new drugs that may be used to inhibit FGFR2. This review will provide an overview of our current understanding of FGFR2 and potential mechanisms in which we can target FGFR2 in cSCC. The goals of this review are the following: (1) to highlight our current knowledge of the role of FGFR2 in healthy skin and contrast this with its role in the development of cancer; (2) to further explain the specific molecular mechanisms that FGFR2 uses to promote tumorigenesis; (3) to describe how FGFR2 contributes to more invasive disease; (4) to describe its immunosuppressive effects in skin; and (5) to evaluate its effect on current anticancer therapy and discuss therapies on the horizon to target FGFR2 related malignancy.

Identifying SCC Lesions Capable of Spontaneous Regression by Using Immunohistochemistry: A Systematic Review and Meta-Analysis

INTRODUCTION

Keratoacanthoma (KA) and squamous cell carcinoma (SCC) are two cutaneous conditions with morphological resemblance, which can complicate the diagnosis in some cases. Using immunohistochemistry staining of biomarkers could be beneficial in resolving this obstacle.

OBJECTIVES

We investigated a variety of biomarkers assessed in different studies in order to find the most important and helpful biomarkers for differentiation between SCC and lesions capable of spontaneous regression.

METHODS

MEDLINE via PubMed and Google Scholar database were used to identify relevant literature up to 15 June 2022. The aim of our analyses was to determine the capability of biomarkers to distinguish between SCC and lesions capable of spontaneous regression using calculated individual and pooled odds ratios (OR) and 95% confidence intervals (CI) and I2 tests.

RESULTS

Six potential biomarkers were CD10 with pooled OR= 0.006 (95% CI: 0.001-0.057) and I2=0%; COX-2 with pooled OR=0.089 (95% CI: 0.029-0.269) and I2=17.1%; elastic fibers with pooled OR= 6.69 (95% CI: 2.928-15.281) and I2=0%; IMP-3 with pooled OR=0.145 (95% CI: 0.021-1.001) and I2=44.5%; P53 with pooled OR=0.371 (95% CI: 0.188-0.733) and I2=55.9%; AT1R with OR=0.026 (95% CI: 0.006-0.107).

CONCLUSIONS

We suggest the utilization of the following IHC biomarkers for discrimination between lesions with spontaneous regression such as KA and SCC: CD10, COX-2, and elastic fibers.

Review: PD-L1 as an emerging target in the treatment and prevention of keratinocytic skin cancer

Recent advances in the understanding and targeting of immune checkpoints have led to great progress in immune therapies against many forms of cancer. While many types of immune checkpoints are currently targeted in the clinic, this review will focus on recent research implicating the programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) axis as an emerging focus for the treatment of keratinocytic tumors. PD-L1 is of particular interest in nonmelanoma skin cancer (NMSC), as it is not only upregulated in these tumors but is stimulated by environmental ultraviolet exposure. This response may also make PD-L1 an excellent target for photochemoprevention using topically applied small molecule inhibitors. Here, we summarize recent investigations on PD-L1 expression and clinically relevant immune checkpoint inhibitor treatment in cutaneous squamous cell carcinoma, basal cell carcinoma, and head and neck squamous cell carcinoma, as well as small molecule agents targeting PD-L1 that may be useful for clinical development aiming at treatment or prevention of NMSC.

The Role of Extracellular Matrix Remodeling in Skin Tumor Progression and Therapeutic Resistance

The extracellular matrix remodeling in the skin results from a delicate balance of synthesis and degradation of matrix components, ensuring tissue homeostasis. These processes are altered during tumor invasion and growth, generating a microenvironment that supports growth, invasion, and metastasis. Apart from the cellular component, the tumor microenvironment is rich in extracellular matrix components and bound factors that provide structure and signals to the tumor and stromal cells. The continuous remodeling in the tissue compartment sustains the developing tumor during the various phases providing matrices and proteolytic enzymes. These are produced by cancer cells and stromal fibroblasts. In addition to fostering tumor growth, the expression of specific extracellular matrix proteins and proteinases supports tumor invasion after the initial therapeutic response. Lately, the expression and structural modification of matrices were also associated with therapeutic resistance. This review will focus on the significant alterations in the extracellular matrix components and the function of metalloproteinases that influence skin cancer progression and support the acquisition of therapeutic resistance.

Expression of Programmed Cell Death Proteins in Kaposi Sarcoma and Cutaneous Angiosarcoma

Not only for cutaneous angiosarcoma (CAS) patients but also for advanced and therapy-refractory patients with classic Kaposi sarcoma (CKS) and human immunodeficiency virus (HIV)-associated Kaposi sarcoma (HIV-KS) there is a high need for more effective treatment modalities. The aim of this work was to study programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) protein expression and related immune parameters in CKS, HIV-KS, and CAS and correlate it with other immunologic parameters and clinical data. Immunohistochemistry was performed on formalin-fixed paraffin-embedded tumor tissue of 19 CKS, 7 HIV-KS, and 12 CAS patients using antibodies against the following (and they are): PD-1, PD-L1, CD4, CD8, CD56, and FOXP3. PD-1 expression significantly correlated with PD-L1 expression Moreover, PD-1 and PD-L1 expression significantly correlated with CD56 and FOXP3 expression. High intratumoral FOXP3 expression was significantly associated with disease relapse (P=0.029). CD4 and FOXP3 expression was significantly higher in CKS and CAS, as compared with HIV-KS. All in all, PD-1 and PD-L1 expression was relatively weak and did not significantly differ between CKS, HIV-KS, and CAS patients. Nevertheless, PD-1 was positive in 31.6% of CKS, 28.6% of HIV-KS, and 33.3% of CAS patients. PD-L1 was expressed in 36.6% of CKS, 28.6% of HIV-KS, and 41.7% of CAS patients. We have provided evidence that PD-1/PD-L1 signalling is of importance in angiosarcomas such as CKS, HIV-KS, and CAS. Our results support the notion that the use of PD-1/PD-L1 inhibitors may represent an effective strategy against these tumors.

A clinical and biological review of keratoacanthoma

Keratoacanthoma (KA) is a common skin tumour that remains controversial regarding classification, epidemiology, diagnosis, prognosis and management. Classically, a KA manifests as a rapidly growing, well-differentiated, squamoid lesion with a predilection for sun-exposed sites in elderly people and a tendency to spontaneously regress. Historically, KAs have been considered a variant of cutaneous squamous cell carcinoma (cSCC) and are often reported as KA-type cSCC. However, the penchant for regression has led many to categorize KAs as biologically benign tumours with distinct pathophysiological mechanisms from malignant cSCC. The clinical and histopathological similarities between KA and cSCC, particularly the well-differentiated variant of cSCC, have made definitive differentiation difficult or impossible in many cases. The ambiguity between entities has led to the general recommendation for surgical excision of KAs to ensure a potentially malignant cSCC is not left untreated. This current standard creates unnecessary surgical morbidity and financial strain for patients, especially the at-risk elderly population. There have been no reports of death from a definitive KA to date, while cSCC has an approximate mortality rate of 1·5%. Reliably distinguishing cSCC from KA would shift management strategies for KAs towards less-invasive treatment modalities, prevent unnecessary surgical morbidity, and likely reduce associated healthcare costs. Herein, we review the pathophysiology and clinical characteristics of KA, and conclude on the balance of current evidence that KA is a benign lesion and distinct from cSCC.

Histopathologic PD-L1 Tumor Expression and Prognostic Significance in Nonmelanoma Skin Cancers: A Systematic Review

ABSTRACT

PD-L1 and PD-1 inhibitors are being increasingly used to treat a variety of nonmelanoma skin cancers (NMSCs). This systematic review summarizes PD-L1 expression in NMSCs and determines its use for prognosis using targeted immunotherapy. A primary search of peer-reviewed English-language medical literature was conducted for studies on PD-L1 tumor expression in biopsied or excised NMSCs. Fifty-nine articles met criteria for inclusion. PD-L1 expression in advanced NMSCs ranged from 22%-89% for basal cell carcinomas, 42%-50% for Merkel cell carcinomas, and 26%-100% for squamous cell carcinomas. Study limitations included clone heterogeneity across studies, complicating comparison of PD-L1 expression. Differences were also noted in the selection of tumor reactivity threshold. We conclude that there is insufficient evidence to determine the prognostic significance of PD-L1 expression in NMSCs as a whole, but this remains a promising area. More investigation into the role of tumor PD-L1 as a biomarker for predicting clinical response to PD-L1 and PD-1 inhibitors in NMSCs is needed.

The Tumor Microenvironment in SCC: Mechanisms and Therapeutic Opportunities

Squamous cell carcinoma (SCC) is the second most common skin cancer worldwide and, despite the relatively easy visualization of the tumor in the clinic, a sizeable number of SCC patients are diagnosed at advanced stages with local invasion and distant metastatic lesions. In the last decade, immunotherapy has emerged as the fourth pillar in cancer therapy via the targeting of immune checkpoint molecules such as programmed cell-death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). FDA-approved monoclonal antibodies directed against these immune targets have provide survival benefit in a growing list of cancer types. Currently, there are two immunotherapy drugs available for cutaneous SCC: cemiplimab and pembrolizumab; both monoclonal antibodies (mAb) that block PD-1 thereby promoting T-cell activation and/or function. However, the success rate of these checkpoint inhibitors currently remains around 50%, which means that half of the patients with advanced SCC experience no benefit from this treatment. This review will highlight the mechanisms by which the immune checkpoint molecules regulate the tumor microenvironment (TME), as well as the ongoing clinical trials that are employing single or combinatory therapeutic approaches for SCC immunotherapy. We also discuss the regulation of additional pathways that might promote superior therapeutic efficacy, and consequently provide increased survival for those patients that do not benefit from the current checkpoint inhibitor therapies.

Tumor immunotherapy - A lot to learn from Keratoacanthoma

Dysfunctionalinty and exhaustion of T cells in the tumor microenvironment is a harsh reality of anti-tumor immune response where tumor cells can escape it. A considerable effort is going on in the field of research that tries to harness the power of T cells against cancer cells to design new anti-cancer immunotherapeutic designs. All these efforts are getting a setback due to the fact that T cells become dysfunctional in tumors while expressing exhaustion markers, so it is necessary to understand from the perspective of cancer itself that what is lacking in tumor-specific T cells in tumor microenvironment so they are getting evaded. Keratoacanthoma is a compelling case of a tumor where auto-regression is happening and many molecular mechanisms can be attributed to this fact. One of the possibilities is having non-exhausting T cells and a highly conducive environment for anti-tumor immune response. In this hypothesis, I am proposing a detailed strategy to decipher this peculiar type of possible immune response in keratoacanthoma and how it can be idolized to create successful anti-cancer T cell immunotherapies.

Expression of Programmed Death-Ligand 1 in Cutaneous Squamous Cell Carcinoma Arising in Sun-Exposed and Nonsun-Exposed Skin

Background

A recent clinical trial has shown the efficacy of an anti-programmed death-1 (PD-1) antibody against advanced squamous cell carcinoma (SCC). The expression of PD-ligand 1 (PD-L1) in tumor cells correlates with a favorable response to anti-PD-1 therapy in various malignancies. In recent studies, it has been shown that SCC frequently expresses PD-L1. However, there has been no previous study focusing on the difference in PD-L1 expression between SCC in sun-exposed skin and that in nonsun-exposed areas.

Aims

The purpose of this study was to investigate the relationship between sun-exposure status and PD-L1 expression in patients with SCC.

Materials and Methods

We investigated 80 patients with SCC (40 patients with SCC in sun-exposed skin and 40 patients with SCC in nonsun-exposed skin) by immunohistochemical staining for PD-L1. Fisher's exact test was used for statistical analyses of the differences between the two groups.

Results

Patients with SCC in sun-exposed skin showed a significantly higher expression level of PD-L1 in tumor cells than did patients with SCC in nonsun-exposed skin (P = 0.0133).

Conclusions

We found that the expression level of PD-L1 in patients with SCC in sun-exposed skin was higher than in patients with SCC in nonsun-exposed skin. Practical data are needed for appropriate applications of new therapeutic options for SCC.

p53-Regulated Long Noncoding RNA PRECSIT Promotes Progression of Cutaneous Squamous Cell Carcinoma via STAT3 Signaling

Long noncoding RNAs (lncRNAs) have emerged as putative biomarkers and therapeutic targets in cancer. The role of lncRNA LINC00346 in cutaneous squamous carcinoma (cSCC) was examined. The expression of LINC00346 was up-regulated in cSCC cells compared with normal human epidermal keratinocytes. Elevated expression of LINC00346 was noted in tumor cells in cSCC tissue sections in vivo, as compared with cSCC in situ, and actinic keratosis by RNA in situ hybridization; and the expression in seborrheic keratosis and normal skin was very low. Immunohistochemical analysis of cSCC tissue sections and functional assays of cSCC cells in culture showed that LINC00346 expression is down-regulated by p53. Knockdown of LINC00346 inhibited invasion of cSCC cells in culture and suppressed growth of human cSCC xenografts in vivo. Knockdown of LINC00346 inhibited expression of activated STAT3 and resulted in down-regulation of the expression of matrix metalloproteinase (MMP)-1, MMP-3, MMP-10, and MMP-13. Based on these observations LINC00346 was named p53 regulated carcinoma-associated STAT3-activating long intergenic non-protein coding transcript (PRECSIT). These results identify PRECSIT as a new p53-regulated lncRNA, which promotes progression of cSCC via STAT3 signaling.

PD-L1/PD1 Expression, Composition of Tumor-Associated Immune Infiltrate, and HPV Status in Conjunctival Squamous Cell Carcinoma

Purpose

Conjunctival squamous cell carcinoma (SCC), a type of ocular surface neoplasia, is primarily treated by surgical resection and topical immuno- or chemotherapy. Metastatic disease may be treated with systemic chemo- or immunotherapy, albeit with variable response. The purpose of this study was to determine whether immune checkpoint blockade might be considered in the management of conjunctival SCC.

Methods

In this retrospective study, we evaluated tumor programmed death-ligand 1 (PD-L1) expression, high-risk human papillomavirus (HPV) status, and immunohistochemical expression of cluster of differentiation 3 (CD3), cluster of differentiation 8 (CD8), and programmed death 1 (PD1) in tumor-associated immune infiltrate in a series of 31 conjunctival SCCs.

Results

PD-L1 expression in ≥1% of tumor cells was noted in 14 conjunctival SCCs (47%) and was more prevalent in invasive than in situ SCC and among tumors with higher American Joint Committee on Cancer (AJCC) T category (≥T3 versus ≤T2). The density of CD3-positive T cells was higher in primary than recurrent tumors and higher in invasive than in situ tumors. Density of CD3-positive and CD8-positive T cells was higher in higher AJCC stage tumors. Density of CD8-positive T cells was higher in HPV-positive than HPV-negative tumors. PD-L1 expression correlated with a higher density of CD3-, CD8-, and PD1-positive cells in the tumor-associated immune infiltrate but not with HPV status.

Conclusions

Our findings demonstrate that PD-L1 is expressed in almost half of conjunctival SCCs. The density of tumor-associated immune cells correlated with invasive SCC, stage, and HPV status in conjunctival SCC. Our findings support further studies to establish the potential application of immune checkpoint blockade in the management of conjunctival SCC.

CMTM6, the newly identified PD-L1 regulator, correlates with PD-L1 expression in lung cancers

Modulation of Immune check point regulators, especially the PD-1/PD-L1 axis, plays a critical role in successful management of a small proportion of lung cancer patients, but not so effective in the rest of lung cancer patients. A better understanding of immunotherapy non-responsive or resistant patients therefore warranted for future development of novel therapeutics. The newly identified regulator CMTM6 (CKLF-like MARVEL transmembrane domain containing 6) has been reported to serves as the stabilizer of PD-L1 and enhances the inhibitory effect of PD-L1 on immune system in both cell line and animal models, but its clinical relevance associated with PD-L1 is unknown and the current study is designed to address this question. The study using immunohistochemistry demonstrated that CMTM6 positivity from 15 out of 19 types of cancers with our in-house tissue microarray, and PD-L1 expression is always found only in CMTM6 positive cancers. CMTM6 and PD-L1 expression were analyzed in 81 lung cancer patient sample, and we observed that CMTM6 expression correlated with cancer histotypes and inversely correlated with cancer metastases, but not with patients’ age and gender. No PD-L1 expression was observed in negative CMTM6 samples. Higher expression PD-L1 is also associated with higher CMTM6 expression. In summary, CMTM6 expression is associated with PD-L1 expression, as well as lung cancer histotypes and metastasis. The results thus for the first time confirmed earlier reports on CMTM6/PD-L1 connection, from a clinical aspect of analysis.

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Confirmed the CMTM6 expression in different cancer tissues include lung cancers.

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Addressed the correlation of CMTM6 and PD-L1 expression in clinical samples.

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Demonstrated the correlation between CMTM6 expression and lung cancer histotypes.

Immune Checkpoint Inhibitors for Treating Advanced Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (CSCC) is one of the most common human malignancies, and the incidence is increasing with time. High mutational loads, known infiltration with lymphocytes, and programmed death (PD)-ligand 1 (PD-L1) expression suggest that immune checkpoint inhibitors, such as PD-1 inhibitors, may show utility in treating CSCC, similar to response see in other solid tumor types. Recently, the robust responsiveness of CSCCs to the PD-1 inhibitor cemiplimab was revealed in the results of a combined phase I/II clinical trial, with an overall response rate of 50% and a durable response exceeding 6 months in 57% of responders. Compared to prior systemic therapies with scant data for efficacy and safety, cemiplimab is a breakthrough therapy, the first systemic drug approved for advanced CSCCs. Other immune checkpoint inhibitors have shown promise through case reports and series, and are currently in clinical development for CSCCs.

PD-L1 Expression in Unresectable Locally Advanced or Metastatic Skin Squamous Cell Carcinoma Treated with Anti-Epidermal Growth Factor Receptor Agents

BACKGROUND

Recurrent or metastatic (R/M) skin squamous cell carcinoma (sSCC) not amenable of surgery or irradiation may benefit from systemic therapies. Epidermal growth factor receptor (EGFR) inhibitors and, more recently, immune checkpoint blockers (ICBs) showed activity in R/M sSCC. In this study, we aimed at exploring the possible role of PD-L1 expression in predicting response to anti-EGFR agents.

METHODS

Patients affected by R/M sSCC, treated with pan-HER inhibitor dacomitinib or with platinum-based chemotherapy with cetuximab (CT-cet) from 2010 to 2016, were considered. PD-L1 expression was assessed with immunohistochemistry on tumor cells (TCs) and on microenvironment (TC and tumor-infiltrating lymphocyte [IC] scores, respectively). Prognostic role of PD-L1 and the correlation with response to EGFR inhibitors and survival were analyzed.

RESULTS

Twenty-eight R/M sSCCs were analyzed (19 treated with dacomitinib, 9 with CT-cet). TC and IC were negative in 82 and 45% of cases, respectively; 15% sSCCs were both TC and IC positive. Progression-free survival (PFS) was longer in IC-positive cases (median 7.5 months vs. 2.1 in IC0, p = 0.02). No statistically significant differences were observed between PD-L1 expression and both overall survival and response rates.

CONCLUSION

PD-L1 expression in microenvironment predicted better PFS. The combination of EGFR inhibitors and ICB could help deepening the knowledge about the interrelations between the EGFR and PD-1/PD-L1 pathways.

PD-L1 Expression is Increased in Metastasizing Squamous Cell Carcinomas and Their Metastases

Programmed cell death ligand 1 (PD-L1) expression by tumor cells plays an important role in the inhibition of T cell-mediated immune response in cancer. PD-L1 expression by tumor cells has been linked to poor prognosis in a wide variety of cancers. However, PD-L1 expression in cutaneous squamous cell carcinoma (cSCC) has been scarcely studied, and its role as a prognosis biomarker remains controversial. The association of PD-L1 expression and the metastatic risk in a series of cSCC was assessed. PD-L1 and CD8 immunostainings of full excision sections of 99 primary tumors and 24 lymphatic metastases were semiquantitatively evaluated. Primary cSCCs were grouped according to the development of lymphatic metastatic spread [metastasizing squamous cell carcinoma (MSCC)] (n = 48) or the absence of progression [nonmetastasizing squamous cell carcinoma (NMSCC)] (n = 51). PD-L1-positive expression (cut off ≥1%) was found in 26% NMSCCs and in 50% MSCCs (P = 0.02). PD-L1 association with an increased metastatic risk was confirmed in the multivariate analysis (P < 0.05), along with the following features: recurrence, poor differentiation, and perineural invasion. Ninety percent of the metastases of PD-L1-positive tumors were also positive for PD-L1, displaying a trend toward a higher PD-L1 expression when compared with their primary tumors (P = 0.058). No significant differences in the peritumoral inflammatory infiltrate or in the expression of CD8 were found between metastasizing and nonmetastasizing primary tumors. Our results suggest that PD-L1 may play a relevant role in metastatic spread and may be a candidate prognostic biomarker in cSCC.

T-lymphocyte profiles differ between keratoacanthomas and invasive squamous cell carcinomas of the human skin

BACKGROUND

T-lymphocytes are involved in tumor progression and regression. Actinic keratoses (AK) are atypical proliferations of keratinocytes of the skin. Some AK progress into invasive cutaneous squamous cell carcinomas (cSCC). Keratoacanthomas (KA) are either classified as a cSCC subtype or a benign tumor with histologic resemblance to well-differentiated cSCC as it is supposed to regress spontaneously. In contrast, cSCC represent malignant tumors that may metastasize.

OBJECTIVES

To compare the T-lymphocyte profiles of AK, KA and cSCC in relation to PD-L1 expression.

METHODS

Tissue micro-arrays of 103 cases of AK, 43 cases of KA and 106 cases of cSCC were stained by immunohistochemistry for E-cadherin, CD3, CD4, CD8, FOXp3, and the receptor-ligand pair PD-1/PD-L1. Immunohistological scores were computationally determined to assess PD-L1 expression as well as the expression profiles of T-lymphocytes.

RESULTS

AK had lower numbers of CD3+ and PD-1+ cells compared to KA and lower numbers of CD3+, CD8+ and PD-1+ cells in comparison with cSCC. KA showed significantly higher numbers of CD4+ and FOXp3+ cells as well as lower numbers of CD8+ cells in comparison with invasive cSCC. cSCC expressed significantly more PD-L1 in comparison with AK and KA. Among cSCC PD-L1 expression was higher in moderately and poorly-differentiated cSCC than in well-differentiated cSCC. Increased PD-L1 expression also correlated with increased numbers of CD4+, CD8+ and FOXp3+ cells in cSCC.

CONCLUSIONS

Tumor-associated T-lymphocyte infiltrates showed significant differences between AK, KA and invasive cSCC. PD-L1 expression correlated with invasion of T-cell infiltrates in invasive cSCC.