Concordant overexpression of phosphorylated ATF2 and STAT3 in extramammary Paget's disease

Overexpression of Janus kinase 2 protein in extramammary Paget's disease

Extramammary Paget's disease is a rare malignant tumor of the skin that occurs primarily in the genitocrural region. Although the prognosis of extramammary Paget's disease with distant metastasis is poor, an effective therapy has not been established. Because Janus kinase 2 has attracted attention as a therapeutic target in several cancers, we investigated the expression of the Janus kinase 2 protein and the relationship between its level of expression and clinical significance in 53 patients with extramammary Paget's disease in our hospital. Immunohistochemistry showed that most extramammary Paget's disease tissues were positive for Janus kinase 2 (50/53, 94.3%), and the immunostaining intensity of Janus kinase 2 was correlated with the degree of invasiveness, lymph node metastasis and distant metastasis. Based on these findings, Janus kinase 2 may be a promising therapeutic target in extramammary Paget's disease.

Expression of laminin-5 gamma 2 chain predicts invasion of extramammary Paget's disease cell

Extramammary Paget's disease (EMPD) is a rare malignant skin neoplasm characterized by intraepidermal proliferation of tumor cells. The tumor cells of EMPD may sometimes invade into the dermis or metastasize into the regional lymph nodes. Several studies have proposed mechanisms underlying the increased invasiveness of EMPD; however, molecular markers indicating invasiveness have yet to be well characterized. Laminin-5 (Lam-5), a heterotrimer composed of three chains (α3, β3, and γ2), is a major component of the basement membrane in many tissues. One of the chains, Lam-5 γ2, is a marker of invasion, because it often develops as a monomer in malignant neoplasms. We investigated the expression of Lam-5 γ2 and its role for the invasiveness in EMPD. Paraffin-embedded specimens of EMPD obtained from 36 patients were examined immunohistochemically for Lam-5 γ2. The cases adopted into this study comprised 16 cases of intraepidermal lesions and 20 cases with dermal invasion. The basement membrane seen in normal skin disappeared in one-third of non-invasive cases and in most invasive cases. The disappearance of Lam-5 γ2 in the basement membrane and its cytoplasmic expression was more observed in the invasive cases than non-invasive cases. Expression of Lam-5 γ2 may be a biological marker to predict invasiveness of EMPD.

The Msi1-mTOR pathway drives the pathogenesis of mammary and extramammary Paget's disease

Mammary and extramammary Paget's Diseases (PD) are a malignant skin cancer characterized by the appearance of Paget cells. Although easily diagnosed, its pathogenesis remains unknown. Here, single-cell RNA-sequencing identified distinct cellular states, novel biomarkers, and signaling pathways - including mTOR, associated with extramammary PD. Interestingly, we identified MSI1 ectopic overexpression in basal epithelial cells of human PD skin, and show that Msi1 overexpression in the epidermal basal layer of mice phenocopies human PD at histopathological, single-cell and molecular levels. Using this mouse model, we identified novel biomarkers of Paget-like cells that translated to human Paget cells. Furthermore, single-cell trajectory, RNA velocity and lineage-tracing analyses revealed a putative keratinocyte-to-Paget-like cell conversion, supporting the in situ transformation theory of disease pathogenesis. Mechanistically, the Msi1-mTOR pathway drives keratinocyte-Paget-like cell conversion, and suppression of mTOR signaling with Rapamycin significantly rescued the Paget-like phenotype in Msi1-overexpressing transgenic mice. Topical Rapamycin treatment improved extramammary PD-associated symptoms in humans, suggesting mTOR inhibition as a novel therapeutic treatment in PD.

The activating transcription factor 2: an influencer of cancer progression

In contrast to the continuous increase in survival rates for many cancer entities, colorectal cancer (CRC) and pancreatic cancer are predicted to be ranked among the top 3 cancer-related deaths in the European Union by 2025. Especially, fighting metastasis still constitutes an obstacle to be overcome in CRC and pancreatic cancer. As described by Fearon and Vogelstein, the development of CRC is based on sequential mutations leading to the activation of proto-oncogenes and the inactivation of tumour suppressor genes. In pancreatic cancer, genetic alterations also attribute to tumour development and progression. Recent findings have identified new potentially important transcription factors in CRC, among those the activating transcription factor 2 (ATF2). ATF2 is a basic leucine zipper protein and is involved in physiological and developmental processes, as well as in tumorigenesis. The mutation burden of ATF2 in CRC and pancreatic cancer is rather negligible; however, previous studies in other tumours indicated that ATF2 expression level and subcellular localisation impact tumour progression and patient prognosis. In a tissue- and stimulus-dependent manner, ATF2 is activated by upstream kinases, dimerises and induces target gene expression. Dependent on its dimerisation partner, ATF2 homodimers or heterodimers bind to cAMP-response elements or activator protein 1 consensus motifs. Pioneering work has been performed in melanoma in which the dual role of ATF2 is best understood. Even though there is increasing interest in ATF2 recently, only little is known about its involvement in CRC and pancreatic cancer. In this review, we summarise the current understanding of the underestimated ‘cancer gene chameleon’ ATF2 in apoptosis, epithelial-to-mesenchymal transition and microRNA regulation and highlight its functions in CRC and pancreatic cancer. We further provide a novel ATF2 3D structure with key phosphorylation sites and an updated overview of all so-far available mouse models to study ATF2 in vivo.

ATF2 promotes urothelial cancer outgrowth via cooperation with androgen receptor signaling

We investigated the functional role of ATF2, a transcription factor normally activated via its phosphorylation in response to phospho-ERK/MAPK signals, in the outgrowth of urothelial cancer. In both neoplastic and non-neoplastic urothelial cells, the expression levels of androgen receptor (AR) correlated with those of phospho-ATF2. Dihydrotestosterone treatment in AR-positive bladder cancer cells also induced the expression of phospho-ATF2 and phospho-ERK as well as nuclear translocation and transcriptional activity of ATF2. Meanwhile, ATF2 knockdown via shRNA resulted in significant decreases in cell viability, migration and invasion of AR-positive bladder cancer lines, but not AR-negative lines, as well as significant increases and decreases in apoptosis or G0/G1 cell cycle phase and S or G2/M phase, respectively. Additionally, the growth of AR-positive tumors expressing ATF2-shRNA in xenograft-bearing mice was retarded, compared with that of control tumors. ATF2 knockdown also resulted in significant inhibition of neoplastic transformation induced by a chemical carcinogen 3-methylcholanthrene, as well as the expression of Bcl-2/cyclin-A2/cyclin-D1/JUN/MMP-2, in immortalized human normal urothelial SVHUC cells stably expressing AR, but not AR-negative SVHUC cells. Finally, immunohistochemistry in surgical specimens demonstrated significant elevation of ATF2/phospho-ATF2/phospho-ERK expression in bladder tumors, compared with non-neoplastic urothelial tissues. Multivariate analysis further showed that moderate/strong ATF2 expression and phospho-ATF2 positivity were independent predictors for recurrence of low-grade tumors (hazard ratio (HR) = 2.956, P = 0.045) and cancer-specific mortality of muscle-invasive tumors (HR = 5.317, P = 0.012), respectively. Thus, ATF2 appears to be activated in urothelial cells through the AR pathway and promotes the development and progression of urothelial cancer.

ATF2, a paradigm of the multifaceted regulation of transcription factors in biology and disease

Stringent transcriptional regulation is crucial for normal cellular biology and organismal development. Perturbations in the proper regulation of transcription factors can result in numerous pathologies, including cancer. Thus, understanding how transcription factors are regulated and how they are dysregulated in disease states is key to the therapeutic targeting of these factors and/or the pathways that they regulate. Activating transcription factor 2 (ATF2) has been studied in a number of developmental and pathological conditions. Recent findings have shed light on the transcriptional, post-transcriptional, and post-translational regulatory mechanisms that influence ATF2 function, and thus, the transcriptional programs coordinated by ATF2. Given our current knowledge of its multiple levels of regulation and function, ATF2 represents a paradigm for the mechanistic complexity that can regulate transcription factor function. Thus, increasing our understanding of the regulation and function of ATF2 will provide insights into fundamental regulatory mechanisms that influence how cells integrate extracellular and intracellular signals into a genomic response through transcription factors. Characterization of ATF2 dysfunction in the context of pathological conditions, particularly in cancer biology and response to therapy, will be important in understanding how pathways controlled by ATF2 or other transcription factors might be therapeutically exploited. In this review, we provide an overview of the currently known upstream regulators and downstream targets of ATF2.

PI3K, Rac1 and pPAK1 are overexpressed in extramammary Paget's disease

BACKGROUND

Phosphatidylinositol 3-kinase (PI3K), Ras-related C3 botulinum toxin substrate 1 (Rac1) and P21-activated protein kinase 1 (PAK1) appear to play important roles in the pathogenesis of several tumors, but their expressions in extramammary Paget's disease (EMPD) have not been investigated yet.

OBJECTIVES

To investigate the potential contribution of the PI3K, Rac1 and PAK1 to the development of EMPD.

METHODS

Thirty-five paraffin-embedded EMPD specimens were subjected to immunohistochemical staining for PI3K (85α), Rac1 and pPAK1.

RESULTS

All the 35 primary EMPD specimens, including 20 non-invasive EMPD, 13 invasive EMPD and 2 metastatic lymph nodes, showed cytoplasm overexpression of PI3K (85α), Rac1 and pPAK1. The expression (% positive cells) of PI3K(85α), Rac1 and pPAK1 (90.1 ± 8.6, 91.4 ± 9.5 and 89.6 ± 10.8% ) in EMPD were significantly higher than in apocrine glands of normal skin ( 20.1 ± 11.9, 29.8 ± 8.9, 41.1 ± 13.4%), and the expression in invasive EMPD with lymph node metastasis (98.2 ± 1.7, 98.8 ± 0.7 and 98.4 ± 0.9%) are significantly higher than in invasive EMPD without lymph node metastasis (94.1 ± 2.6, 96.5 ± 1.7 and 95.3 ± 1.1%) and non-invasive EMPD (85.2 ± 8.4, 87.1 ± 9.9 and 83.1 ± 10.6%). There were significant positive correlations of the expression levels between PI3K (85α) and Rac1, as well as between Rac1 and pPAK1 in EMPD.

CONCLUSIONS

These results indicate that PI3K, Rac1 and PAK1 may play important roles in the pathogenesis of EMPD.

Emerging roles of ATF2 and the dynamic AP1 network in cancer

Cooperation among transcription factors is central for their ability to execute specific transcriptional programmes. The AP1 complex exemplifies a network of transcription factors that function in unison under normal circumstances and during the course of tumour development and progression. This Perspective summarizes our current understanding of the changes in members of the AP1 complex and the role of ATF2 as part of this complex in tumorigenesis.