β-Catenin and CD44 Expression in Keratoacanthoma and Squamous Cell Carcinoma of the Skin

To treat or not to treat: PD-L1 inhibitor-induced keratoacanthoma and squamous cell carcinoma

Keratoacanthoma (KA) and squamous cell carcinoma (SCC) are rare side effects of programmed cell death ligand-1 (PD-L1) inhibitors that can disrupt therapy. There is no consensus on optimal treatment. We investigated the management strategy and factors influencing pathophysiology. An institutional cancer registry and literature search were used for this retrospective study. Only PD-L1-induced KA and SCC cases were included. Pathology specimens were stained with immune markers and management strategies were analyzed. Four cases were identified at our institution. Immunohistochemistry of atypical keratinocytes revealed PD-1/PD-L1 positivity, high p53, and low bcl-2 for all cases with differential expression of CD44 and beta-catenin for KA versus SCC. Nivolumab was continued or temporarily held with complete resolution. In addition, a literature search identified 30 additional cases of KA/SCC after PDL-1 inhibitor use. The most common treatment was excision/destruction followed by topical and/or intralesional corticosteroids. Therapy was definitely withheld in 22% of KA patients and in 9% of SCC cases. The expression of PD-L1 by atypical keratinocytes helps to explain the effects of nivolumab on the development of cutaneous neoplasms. The expression of immune markers provides mechanistic insights into pathophysiology. Management may be achieved with conservative therapy and without treatment interruption.

Epidermal YAP activity drives canonical WNT16/β-catenin signaling to promote keratinocyte proliferation in vitro and in the murine skin

The skin constantly self-renews throughout adult life. Wnt/β-catenin signaling plays a key role in promoting keratinocyte proliferation in the hair follicles and in the interfollicular epidermis. A recent report demonstrated that epidermal YAP activity drives β-catenin activation to promote keratinocyte proliferation in the murine skin. However, it remains unclear whether this is caused by paracrine activation of canonical Wnt signaling or through other YAP/β-catenin regulatory interactions. In the present study, we found that XAV939-inhibition of canonical WNT signaling in skin of YAP2-5SA-ΔC mice resulted in diminished β-catenin activation, reduced keratinocyte proliferation, and a mitigation of the hyperplastic abnormalities in the interfollicular epidermis, signifying a canonical WNT ligand-dependent mechanism. Our subsequent analyses determined that WNT16 is produced in response to YAP activity in keratinocytes both in vitro and in vivo, and that WNT16 drives HaCaT keratinocyte proliferation via canonical WNT16/β-catenin signaling. We conclude that under normal physiological conditions WNT16 is the paracrine WNT ligand secreted in response to epidermal YAP activity that promotes cell proliferation in the interfollicular epidermis. This study delineates a fundamental YAP-driven mechanism that controls normal skin regeneration, and that may be perturbed in human regenerative disease displaying increased YAP and WNT signaling activity.

Wnt/β-Catenin Signaling Pathway in Skin Carcinogenesis and Therapy

Cooperating with other signaling pathways, Wnt signaling controls cell proliferation, morphology, motility, and embryonic development destination and maintains the homeostasis of tissues including skin, blood, intestine, and brain by regulating somatic stem cells and their niches throughout adult life. Abnormal regulation of Wnt pathways leads to neoplastic proliferation in these tissues. Recent research shows that Wnt signaling is also associated with the regulation of cancer stem cells (CSCs) through a similar mechanism to that observed in normal adult stem cells. Thus, the Wnt/β-catenin signaling pathway has been intensively studied and characterized. For this review, we will focus on the regulation of the Wnt/β-catenin signaling pathway in skin cancer. With the important role in stemness and skin CSC proliferation, the Wnt/β-catenin signaling pathway and its elements have the potential to be targets for skin cancer therapy.

Pattern of TGFbeta receptor 1 expression differs between kras-mutated keratoacanthomas and squamous cell carcinomas of the skin

PURPOSE

Increasing evidence indicates that TGFbeta- and EGFR-signaling is involved in the pathogenesis of keratoacanthoma (KA) and squamous cell carcinoma (SCC) of the skin. We analyzed the expression pattern of TGFbeta-signaling components and screened for mutations in tgfbetaR1, egfr, kras and braf in KAs and SCCs.

METHODS

Immunohistochemical analysis of TGFbeta1, TGFbetaR1, TGFbetaR2 and phospho-SMAD2/3 was performed on skin tumors (29 KAs, 30 well and 31 moderately differentiated SCCs). Mutation screening in hotspot regions of tgfbetaR1, egfr, kras and braf was performed through pyrosequencing of tumor DNA.

FINDINGS

Expression of TGFbeta1, TGFbetaR1 and p-SMAD2/3 was increased in tumors as compared to surrounding skin. In KAs characteristic strong discontinuous membranous TGFbetaR1 expression pattern frequently associated with kras mutation was noted. SCCs showed continuous TGFbetaR1 expression, stronger p-SMAD2/3 expression and less frequent kras mutations. In tumors at sun-exposed sites stronger TGFbetaR1 expression was noted. One SCC showed tgfbetaR1 mutation, but no other mutations were found.

CONCLUSION

Although tgfbetaR1 germline mutations cause inherited KAs and our finding of strong discontinuous membranous expression in KAs suggests accumulation of functionally altered protein, we found no tgfbetaR1 mutations or influence on TGFbeta-signaling, but frequent kras mutations in this subgroup of KAs. Characteristic TGFbetaR1 expression pattern in KA can facilitate histopathologic distinction from SCC.

Monoallelic loss of tumor suppressor GRIM-19 promotes tumorigenesis in mice

Gene-associated with retinoid-interferon induced mortality-19 (GRIM-19), a STAT3-inhibitory protein, was isolated as a growth-suppressive gene product using a genome-wide expression knockdown screen. We and others have shown a loss of expression and occurrence of mutations in the GRIM-19 gene in a variety of primary human cancers, indicating its potential role as tumor suppressor. To help investigate its role in tumor development in vivo, we generated a genetically modified mouse in which Grim-19 can be conditionally inactivated. Deletion of Grim-19 in the skin significantly increased the susceptibility of mice to chemical carcinogenesis, resulting in development of squamous cell carcinomas. These tumors had high Stat3 activity and an increased expression of Stat3-responsive genes. Loss of Grim-19 also caused mitochondrial electron transport dysfunction resulting from failure to assemble electron transport chain complexes and altered the expression of several cellular genes involved in glycolysis. Surprisingly, the deletion of a single copy of the Grim-19 gene was sufficient to promote carcinogenesis and formation of invasive squamous cell carcinomas. These observations highlight the critical role of GRIM-19 as a tumor suppressor.

Surrogate variable analysis using partial least squares (SVA-PLS) in gene expression studies

MOTIVATION

In a typical gene expression profiling study, our prime objective is to identify the genes that are differentially expressed between the samples from two different tissue types. Commonly, standard analysis of variance (ANOVA)/regression is implemented to identify the relative effects of these genes over the two types of samples from their respective arrays of expression levels. But, this technique becomes fundamentally flawed when there are unaccounted sources of variability in these arrays (latent variables attributable to different biological, environmental or other factors relevant in the context). These factors distort the true picture of differential gene expression between the two tissue types and introduce spurious signals of expression heterogeneity. As a result, many genes which are actually differentially expressed are not detected, whereas many others are falsely identified as positives. Moreover, these distortions can be different for different genes. Thus, it is also not possible to get rid of these variations by simple array normalizations. This both-way error can lead to a serious loss in sensitivity and specificity, thereby causing a severe inefficiency in the underlying multiple testing problem. In this work, we attempt to identify the hidden effects of the underlying latent factors in a gene expression profiling study by partial least squares (PLS) and apply ANCOVA technique with the PLS-identified signatures of these hidden effects as covariates, in order to identify the genes that are truly differentially expressed between the two concerned tissue types.

RESULTS

We compare the performance of our method SVA-PLS with standard ANOVA and a relatively recent technique of surrogate variable analysis (SVA), on a wide variety of simulation settings (incorporating different effects of the hidden variable, under situations with varying signal intensities and gene groupings). In all settings, our method yields the highest sensitivity while maintaining relatively reasonable values for the specificity, false discovery rate and false non-discovery rate. Application of our method to gene expression profiling for acute megakaryoblastic leukemia shows that our method detects an additional six genes, that are missed by both the standard ANOVA method as well as SVA, but may be relevant to this disease, as can be seen from mining the existing literature.

Keratoacanthoma: facts and controversies

The keratoacanthoma and its variants are clinically and histologically heterogenous. Some consider the keratoacanthoma to be benign, whereas others classify it as a subtype of squamous cell carcinoma. The keratoacanthoma is generally treated rather than observed for spontaneous resolution. This hampers evaluation of the true natural history of lesions diagnosed as keratoacanthoma. In addition, studies have not found a reliable marker to differentiate keratoacanthoma from squamous cell carcinoma. It currently remains unclear how the keratoacanthoma relates to squamous cell carcinoma, and continued investigation is necessary.