The Novel Checkpoint Target Lymphocyte-Activation Gene 3 Is Highly Expressed in Cutaneous Squamous Cell Carcinoma

BACKGROUND

Lymphocyte activation-gene 3 (LAG-3) is an emerging next-generation immune checkpoint molecule. We aim to define the expression pattern of LAG-3 in cutaneous squamous cell carcinoma (cSCC) as a first step to understand the role of LAG-3 in cSCC prognosis and therapy.

OBJECTIVE

To define the expression pattern of LAG-3 in cSCC as a first step to understand the role of LAG-3 in cSCC prognosis and therapy.

METHODS

To test whether LAG-3 is expressed on cSCC infiltrating lymphocytes, we isolated CD8 + T lymphocytes from three SCC tumors using flow cytometry and performed single-cell RNA sequencing for LAG-3 and programmed cell death protein -1 (PD-1). In addition, we evaluated LAG-3 mRNA expression in formalin-fixed, paraffin-embedded tissue using NanoString technology.

RESULTS

Single-cell RNA sequencing showed that LAG-3 is expressed more than PD-1 in CD8 + tumor infiltrating lymphocytes (50.8% vs 35.2%, respectively). Quantifying LAG-3 mRNA expression showed that compared with normal skin, LAG-3 mRNA is approximately 8 fold higher in immunocompetent associated SCC tumors and approximately 2 fold higher in transplant associated SCC tumors ( p -values <.05). In addition, LAG-3 mRNA was expressed 7.2 fold higher in T2a SCC tumors compared with normal skin ( p -value <.05).

CONCLUSION

Lymphocyte activation-gene 3 is expressed on SCC infiltrating T lymphocytes at a higher percentage than PD-1. In addition, LAG-3 mRNA expression is significantly higher in SCC tumors. Ongoing studies will be performed to define its role as an immune-related biomarker and as a therapeutic target.

LINE-1 retrotransposon expression in cancerous, epithelial and neuronal cells revealed by 5' single-cell RNA-Seq

LINE-1 retrotransposons are sequences capable of copying themselves to new genomic loci via an RNA intermediate. New studies implicate LINE-1 in a range of diseases, especially in the context of aging, but without an accurate understanding of where and when LINE-1 is expressed, a full accounting of its role in health and disease is not possible. We therefore developed a method-5' scL1seq-that makes use of a widely available library preparation method (10x Genomics 5' single cell RNA-seq) to measure LINE-1 expression in tens of thousands of single cells. We recapitulated the known pattern of LINE-1 expression in tumors-present in cancer cells, absent from immune cells-and identified hitherto undescribed LINE-1 expression in human epithelial cells and mouse hippocampal neurons. In both cases, we saw a modest increase with age, supporting recent research connecting LINE-1 to age related diseases.

Understanding the squamous cell carcinoma immune microenvironment

Primary cutaneous squamous cell carcinoma (cSCC) is the second most common human cancer with a rising incidence of about 1.8 million in the United States annually. Primary cSCC is usually curable by surgery; however, in some cases, cSCC eventuates in nodal metastasis and death from disease specific death. cSCC results in up to 15,000 deaths each year in the United States. Until recently, non-surgical options for treatment of locally advanced or metastatic cSCC were largely ineffective. With the advent of checkpoint inhibitor immunotherapy, including cemiplimab and pembrolizumab, response rates climbed to 50%, representing a vast improvement over chemotherapeutic agents used previously. Herein, we discuss the phenotype and function of SCC associated Langerhans cells, dendritic cells, macrophages, myeloid derived suppressor cells and T cells as well as SCC-associated lymphatics and blood vessels. Possible role(s) of SCC-associated cytokines in progression and invasion are reviewed. We also discuss the SCC immune microenvironment in the context of currently available and pipeline therapeutics.

Deep learning automated pathology in ex vivo microscopy

Standard histopathology is currently the gold standard for assessment of margin status in Mohs surgical removal of skin cancer. Ex vivo confocal microscopy (XVM) is potentially faster, less costly and inherently 3D/digital compared to standard histopathology. Despite these advantages, XVM use is not widespread due, in part, to the need for pathologists to retrain to interpret XVM images. We developed artificial intelligence (AI)-driven XVM pathology by implementing algorithms that render intuitive XVM pathology images identical to standard histopathology and produce automated tumor positivity maps. XVM images have fluorescence labeling of cellular and nuclear biology on the background of endogenous (unstained) reflectance contrast as a grounding counter-contrast. XVM images of 26 surgical excision specimens discarded after Mohs micrographic surgery were used to develop an XVM data pipeline with 4 stages: flattening, colorizing, enhancement and automated diagnosis. The first two stages were novel, deterministic image processing algorithms, and the second two were AI algorithms. Diagnostic sensitivity and specificity were calculated for basal cell carcinoma detection as proof of principal for the XVM image processing pipeline. The resulting diagnostic readouts mimicked the appearance of histopathology and found tumor positivity that required first collapsing the confocal stack to a 2D image optimized for cellular fluorescence contrast, then a dark field-to-bright field colorizing transformation, then either an AI image transformation for visual inspection or an AI diagnostic binary image segmentation of tumor obtaining a diagnostic sensitivity and specificity of 88% and 91% respectively. These results show that video-assisted micrographic XVM pathology could feasibly aid margin status determination in micrographic surgery of skin cancer.

MAGE-A3 is a prognostic biomarker for poor clinical outcome in cutaneous squamous cell carcinoma with perineural invasion via modulation of cell proliferation

Perineural invasion is a pathologic process of neoplastic dissemination along and invading into the nerves. Perineural invasion is associated with aggressive disease and a greater likelihood of poor outcomes. In this study, 3 of 9 patients with cutaneous squamous cell carcinoma and perineural invasion exhibited poor clinical outcomes. Tumors from these patients expressed high levels of MAGE-A3, a cancer testis antigen that may contribute to key processes of tumor development. In addition to perineural invasion, the tumors exhibited poor differentiation and deep invasion and were subsequently classified as Brigham and Women's Hospital tumor stage 3. Cyclin E, A and B mRNA levels were increased in these tumors compared with normal skin tissues (102.93±15.03 vs. 27.15±4.59, 36.83±19.41 vs. 11.59±5.83, 343.77±86.49 vs. 95.65±29.25, respectively; p<0.05). A431 cutaneous squamous cell carcinoma cells pretreated with MAGE-A3 antibody exhibited a decreased percentage S-phase cells (14.13±2.8% vs. 33.97±1.1%; p<0.05) and reduced closure in scratch assays (43.88±5.49% vs. 61.17±3.97%; p = 0.0058). In a syngeneic animal model of squamous cell carcinoma, immunoblots revealed overexpression of MAGE-A3 and cyclin E, A, and B protein in tumors at 6 weeks. However, knockout of MAGE-A3 expression caused a reduction in tumor growth (mean tumor volume 155.3 mm3 vs. 3.2 mm3) compared with parental cells. These results suggest that MAGE-A3 is a key mediator in cancer progression. Moreover, elevated collagen XI and matrix metalloproteases 3, 10, 11, and 13 mRNA levels were observed in poorly differentiated cutaneous squamous cell carcinoma with perineural invasion compared with normal skin tissue (1132.56±882.7 vs. 107.62±183.62, 1118.15±1109.49 vs. 9.5±5, 2603.87±2385.26 vs. 5.29±3, 957.95±627.14 vs. 400.42±967.66, 1149.13±832.18 vs. 19.41±35.62, respectively; p<0.05). In summary, this study highlights the potential prognostic value of MAGE-A3 in clinical outcomes of cutaneous squamous cell carcinoma patients.

Current concepts and approaches to merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive and rare cutaneous cancer of the mechanoreceptor unit of the skin with a neuroendocrine origin. MCC incidence has been on the rise over the past two decades. Risk factors include old age, chronic UV exposure, and immunosuppression. Although MCC is a cutaneous malignancy that is often misdiagnosed as a benign nodule at the time of diagnosis, it has an aggressive disease course due to its high recurrence and metastatic potential. The PD-1/PD-L1 checkpoint blockade has recently shown promising results in the management of advanced MCC. Avelumab and pembrolizumab are considered the new standard of care for metastatic MCC. Despite advances in the field, studies are needed to elucidate the role of immunotherapy for patients who are resistant to treatment. Most ongoing clinical trials aim to assess the efficacy of checkpoint inhibitor combination therapies. This article reviews the most current literature on the surgical and medical management of MCC.

A 3D biofabricated cutaneous squamous cell carcinoma tissue model with multi-channel confocal microscopy imaging biomarkers to quantify antitumor effects of chemotherapeutics in tissue

Cutaneous squamous cell carcinoma (cSCC) causes approximately 10,000 deaths annually in the U. S. Current therapies are largely ineffective against metastatic and locally advanced cSCC. There is a need to identify novel, effective, and less toxic small molecule cSCC therapeutics. We developed a 3-dimensional bioprinted skin (3DBPS) model of cSCC tumors together with a microscopy assay to test chemotherapeutic effects in tissue. The full thickness SCC tissue model was validated using hematoxylin and eosin (H&E) and immunohistochemical histological staining, confocal microscopy, and cDNA microarray analysis. A nondestructive, 3D fluorescence confocal imaging assay with tdTomato-labeled A431 SCC and ZsGreen-labeled keratinocytes was developed to test efficacy and general toxicity of chemotherapeutics. Fluorescence-derived imaging biomarkers indicated that 50% of cancer cells were killed in the tissue after 1μM 5-Fluorouracil 48-hour treatment, compared to a baseline of 12% for untreated controls. The imaging biomarkers also showed that normal keratinocytes were less affected by treatment (11% killed) than the untreated tissue, which had no significant killing effect. Data showed that 5-Fluorouracil selectively killed cSCC cells more than keratinocytes. Our 3DBPS assay platform provides cellular-level measurement of cell viability and can be adapted to achieve nondestructive high-throughput screening (HTS) in bio-fabricated tissues.

Decreased cytotoxic T cells and TCR clonality in organ transplant recipients with squamous cell carcinoma

T-cell landscape differences between cutaneous squamous cell carcinoma (cSCC) tumors in immune competent (SCC in IC) and immunocompromised organ transplant recipients (TSCC in OTR) are unclear. We developed an analytical method to define tumor infiltrating lymphocyte (TIL) phenotype in cSCC from immune competent and immune suppressed patients using single-cell TCR sequencing and gene expression data. TSCC exhibits reduced proportions of cytotoxic and naïve TILs and similar numbers of regulatory TILs. Fewer, more heterogeneous TCR clonotypes are observed in TIL from OTR. Most TCR sequences for top ten clonotypes correspond to known antigens, while 24% correspond to putative neoantigens. OTR show increased cSCC events over 12 months possibly due to reduced cytotoxic T-cells. Our novel method of barcoding CD8+ T-cells is the first providing gene expression and TCR sequences in cSCC. Knowledge regarding putative antigens recognized by TCRs with phenotypic function of T-cells bearing those TCRs could facilitate personalized cSCC treatments.

Ruxolitinib inhibits cyclosporine-induced proliferation of cutaneous squamous cell carcinoma

Organ transplant recipients (OTRs) on cyclosporine A (CSA) are prone to catastrophic cutaneous squamous cell carcinoma (SCC). Allograft-sparing, cancer-targeting systemic treatments are unavailable. We have shown increased risk for catastrophic SCC in OTRs via CSA-mediated induction of IL-22. Herein, we found that CSA drives SCC proliferation and tumor growth through IL-22 and JAK/STAT pathway induction. We in turn inhibited SCC growth with an FDA-approved JAK1/2 inhibitor, ruxolitinib. In human SCC cells, the greatest proliferative response to IL-22 and CSA treatment occurred in nonmetastasizing lines. IL-22 treatment upregulated JAK1 and STAT1/3 in A431 SCC cells. JAK/STAT pathway genes were highly expressed in tumors from a cohort of CSA-exposed OTRs and in SCC with high risk for metastasis. Compared with immunocompetent SCC, genes associated with innate immunity, response to DNA damage, and p53 regulation were differentially expressed in SCC from OTRs. In nude mice engrafted with human A431 cells, IL-22 and CSA treatment increased tumor growth and upregulated IL-22 receptor, JAK1, and STAT1/3 expression. Ruxolitinib treatment significantly reduced tumor volume and reversed the accelerated tumor growth. CSA and IL-22 exacerbate aggressive behavior in SCC. Targeting the IL-22 axis via selective JAK/STAT inhibition may reduce the progression of aggressive SCC in OTRs, without compromising immunosuppression.

The unique molecular signatures of nodular and superficial spreading melanoma

9047

Background: Primary nodular melanoma (NM) patients have a relatively poor prognosis compared to superficial spreading melanoma (SSM) patients. The disparity is generally attributed solely to NM's advanced thickness at presentation. In this study we attempted to define molecular signatures of NM and SSM that may explain their clinical differences. Methods: We performed an in silico gene expression analysis of 2 public data sets consisting of 36NM and 54 SSM primary melanoma tissues (CCR 2007;13 and JNCI 2006;98). We then utilized DNA microarray to generate gene expression profiles of a panel of 22 melanoma cell lines (2SSM, 4 NM, 12 met, 4 melanocytes). Differentially expressed genes and over-represented pathways in NM and SSM were identified based on a pooled analysis of the 3 data sets. We then used SNP array to define genomic alterations unique to NM and SSM but not altered in normal melanocytes. Finally, we correlated SNP array with gene expression. Results: Genes significantly overexpressed (p<0.05) in NM showed over-representation of pathways related to MAPK signaling (p=0.05) and cytoskeleton organization (p=0.02), while SSM showed over-representation of cell communication (p=0.05) and primary metabolic processes (p=0.002). Notable correlations between gene expression and copy number alteration in NM include increased copy number/overexpression of SOX5 (transcription factor related to embryonic development and cell fate) and the downregulation/deletion of ST14 (suppression of tumorigenicity 14). SSM demonstrated concordance of increased copy number/overexpression of EZR (cell adhesion protein implicated in human cancer) as well as PALLD (a protein related to motility, adhesion, and extracellular matrix interactions). Notable SSM genes showing correlation between downregulation/deletion include BNIP3 (a pro-apoptotic protein) and MTAP (often co- deleted with tumor suppressor p16). Conclusions: Simultaneous integration of gene expression with SNP array revealed molecular signatures characteristic of NM and SSM. These results suggest that NM and SSM are distinct biologic entities and that molecularly targeted adjuvant therapy may be more effective if tailored to the molecular signatures of melanoma subtypes. Validation is necessary to draw further conclusions.

No significant financial relationships to disclose.

Inhibition of mitochondrial protein translation sensitizes melanoma cells to arsenic trioxide cytotoxicity via a reactive oxygen species dependent mechanism

PURPOSE

Current standard chemotherapeutic regimens for malignant melanoma are unsatisfactory. Although in vitro studies of arsenic trioxide (ATO) have demonstrated promise against melanoma, recent phase II clinical trials have failed to show any significant clinical benefit when used as a single agent. To enhance the efficacy of ATO in the treatment of melanoma, we sought to identify compounds that potentiate the cytotoxic effects of ATO in melanoma cells. Through a screen of 2,000 marketed drugs and naturally occurring compounds, a variety of antibiotic inhibitors of mitochondrial protein translation were identified.

METHODS

The mechanism of action for the most effective agent identified, thiostrepton, was examined in a panel of melanoma cells. Effects of combinatorial ATO and thiostrepton treatment on cytotoxicity, apoptosis, mitochondrial protein content, and reactive oxygen species (ROS) were assessed.

RESULTS

Thiostrepton (1 microM) sensitized three out of five melanoma cell lines to ATO-mediated growth inhibition. Treatment with thiostrepton resulted in reduced levels of the mitochondrial-encoded protein cytochrome oxidase I (COX1). Exposure to thiostrepton in combination with ATO resulted in increased levels of cleaved poly (ADP-ribose) polymerase and cellular ROS. The growth inhibitory and pro-apototic effects of addition of the ATO/thiostrepton combination were reversed by the free radical scavenger N-acetyl-L-cysteine.

CONCLUSIONS

Our data suggest that thiostrepton enhances the cytotoxic effects of ATO through a ROS-dependent mechanism. Co-administration of oxidative stress-inducing drugs such as thiostrepton in order to enhance the efficacy of ATO in the treatment of melanoma warrants further investigation.

Mebendazole induces apoptosis via Bcl-2 inactivation in chemoresistant melanoma cells

Most metastatic melanoma patients fail to respond to available therapy, underscoring the need for novel approaches to identify new effective treatments. In this study, we screened 2,000 compounds from the Spectrum Library at a concentration of 1 micromol/L using two chemoresistant melanoma cell lines (M-14 and SK-Mel-19) and a spontaneously immortalized, nontumorigenic melanocyte cell line (melan-a). We identified 10 compounds that inhibited the growth of the melanoma cells yet were largely nontoxic to melanocytes. Strikingly, 4 of the 10 compounds (mebendazole, albendazole, fenbendazole, and oxybendazole) are benzimidazoles, a class of structurally related, tubulin-disrupting drugs. Mebendazole was prioritized to further characterize its mechanism of melanoma growth inhibition based on its favorable pharmacokinetic profile. Our data reveal that mebendazole inhibits melanoma growth with an average IC(50) of 0.32 micromol/L and preferentially induces apoptosis in melanoma cells compared with melanocytes. The intrinsic apoptotic response is mediated through phosphorylation of Bcl-2, which occurs rapidly after treatment with mebendazole in melanoma cells but not in melanocytes. Phosphorylation of Bcl-2 in melanoma cells prevents its interaction with proapoptotic Bax, thereby promoting apoptosis. We further show that mebendazole-resistant melanocytes can be sensitized through reduction of Bcl-2 protein levels, showing the essential role of Bcl-2 in the cellular response to mebendazole-mediated tubulin disruption. Our results suggest that this screening approach is useful for identifying agents that show promise in the treatment of even chemoresistant melanoma and identifies mebendazole as a potent, melanoma-specific cytotoxic agent.