The oncogene ATF3 is potentiated by cyclosporine A and ultraviolet light A

Meta-stable state photoacid containing β-estradiol fragment with photomodulated biological activity and anti-cancer stem cells properties

Photopharmacology is a young and rapidly developing field of research that offers significant potential for new insights into targeted therapy. While it primarily focuses on cancer treatment, it also holds promise for other diseases. The key feature of photopharmacological agents is the presence of a photosensitive and biologically active component in the same molecule. In our current study, we synthesized a spiropyran-based meta-stable state photoacid containing a fragment of β-estradiol. This compound exhibits negative photochromism and photocontrolled fluorescence under visible-light irradiation due to the initial stabilization of its self-protonated form in solution. We conducted comprehensive biological studies on the HeLa cells model to assess the short- and long-term cytotoxicity of the photoacid, its metabolic effects, its influence on signaling and epithelial-mesenchymal transition super-system pathways, and the proportion of the population enriched with cancer stem cells. Our findings reveal that this derivative demonstrates low cytotoxicity to HeLa cells, yet it is capable of dramatically reducing malignant cells side population enriched in cancer stem cells. Additionally, appropriate structural modification lead to an increase in some other biological effects compared to β-estradiol. In particular, our substance possesses rare properties of AP-1 suppression and demonstrates some pro-oxidant and metabolic effects, which can be regulated by visible light irradiation. As a result, the new estradiol-based photoacid may be considered a promising multi-acting photopharmacological agent for the next-generation anti-cancer research & development.

Skin Cancer Precursors: From Cancer Genomics to Early Diagnosis

Skin cancers, including melanoma and keratinocyte carcinomas, are responsible for increasing health care burden internationally. Risk stratification and early detection are paramount for prevention and less risky treatment to overall improve patient outcomes and disease morbidity. Here, the authors discuss the key concepts leading to skin cancer initiation and progression. The authors also outline precursor and progression models for melanoma and keratinocyte carcinomas, including discussion of genetic alterations associated with the various stages of progression. Finally, the authors discuss the significance of immunoediting and the drivers behind increased risk of cutaneous malignancy in the state of immune dysregulation.

Immunity against Non-Melanoma Skin Cancer and the Effect of Immunosuppressive Medication on Non-Melanoma Skin Cancer Risk in Solid Organ Transplant Recipients

Non-melanoma skin cancers (NMSCs) occur frequently in the Caucasian population and are considered a burden for health care. Risk factors include ultraviolet (UV) radiation, ethnicity and immunosuppression. The incidence of NMSC is significantly higher in solid organ transplant recipients (SOTRs) than in immunocompetent individuals, due to immunosuppressive medication use by SOTRs. While the immunosuppressive agents, calcineurin inhibitors and purine analogues increase the incidence of NMSC in transplant recipients, mTOR inhibitors do not. This is most likely due to the different immunological pathways that are inhibited by each class of drug. This review will focus on what is currently known about the immune response against cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC), two of the main types of NMSC. Furthermore, we will describe the different classes of immunosuppressants given to SOTRs, which part of the immune system they target and how they can contribute to NMSC development. The risk of developing NMSC in SOTRs is the result of a combination of inhibiting immunological pathways involved in immunosurveillance against NMSC and the direct (pro/anti) tumor effects of immunosuppressants.

HSF1 and Its Role in Huntington's Disease Pathology

PURPOSE OF REVIEW

Heat shock factor 1 (HSF1) is the master transcriptional regulator of the heat shock response (HSR) in mammalian cells and is a critical element in maintaining protein homeostasis. HSF1 functions at the center of many physiological processes like embryogenesis, metabolism, immune response, aging, cancer, and neurodegeneration. However, the mechanisms that allow HSF1 to control these different biological and pathophysiological processes are not fully understood. This review focuses on Huntington's disease (HD), a neurodegenerative disease characterized by severe protein aggregation of the huntingtin (HTT) protein. The aggregation of HTT, in turn, leads to a halt in the function of HSF1. Understanding the pathways that regulate HSF1 in different contexts like HD may hold the key to understanding the pathomechanisms underlying other proteinopathies. We provide the most current information on HSF1 structure, function, and regulation, emphasizing HD, and discussing its potential as a biological target for therapy.

DATA SOURCES

We performed PubMed search to find established and recent reports in HSF1, heat shock proteins (Hsp), HD, Hsp inhibitors, HSF1 activators, and HSF1 in aging, inflammation, cancer, brain development, mitochondria, synaptic plasticity, polyglutamine (polyQ) diseases, and HD.

STUDY SELECTIONS

Research and review articles that described the mechanisms of action of HSF1 were selected based on terms used in PubMed search.

RESULTS

HSF1 plays a crucial role in the progression of HD and other protein-misfolding related neurodegenerative diseases. Different animal models of HD, as well as postmortem brains of patients with HD, reveal a connection between the levels of HSF1 and HSF1 dysfunction to mutant HTT (mHTT)-induced toxicity and protein aggregation, dysregulation of the ubiquitin-proteasome system (UPS), oxidative stress, mitochondrial dysfunction, and disruption of the structural and functional integrity of synaptic connections, which eventually leads to neuronal loss. These features are shared with other neurodegenerative diseases (NDs). Currently, several inhibitors against negative regulators of HSF1, as well as HSF1 activators, are developed and hold promise to prevent neurodegeneration in HD and other NDs.

CONCLUSION

Understanding the role of HSF1 during protein aggregation and neurodegeneration in HD may help to develop therapeutic strategies that could be effective across different NDs.

NLRP1 in Cutaneous SCCs: An Example of the Complex Roles of Inflammasomes in Cancer Development

Protein complexes termed inflammasomes ensure tissue protection from pathogenic and sterile stressors by induction of inflammation. This is mediated by different caspase-1-induced downstream pathways, including activation of the pro-inflammatory cytokines proIL-1β and -18, induction of a lytic type of cell death, and regulation of the release of other pro-inflammatory molecules. Aberrant inflammasome activation underlies the pathology of numerous (auto)inflammatory diseases. Furthermore, inflammasomes support or suppress tumor development in a complex cell-type- and stage-dependent manner. In human keratinocytes and skin, NLRP1 is the central inflammasome sensor activated by cellular perturbation induced, for example, by UVB radiation. UVB represents the main inducer of skin cancer, which is the most common type of malignancy in humans. Recent evidence demonstrates that activation of NLRP1 in human skin supports the development of cutaneous squamous cell carcinomas (cSCCs) by inducing skin inflammation. In contrast, the NLRP1 inflammasome pathway is restrained in established cSCCs, suggesting that, at this stage, the protein complex has a tumor suppressor role. A better understanding of the complex functions of NLRP1 in the development of cSCCs and in general of inflammasomes in cancer might pave the way for novel strategies for cancer prevention and therapy. These strategies might include stage-specific modulation of inflammasome activation or its downstream pathways by mono- or combination therapy.

Cutaneous squamous cell carcinoma arising in immunosuppressed patients: a systematic review of tumor profiling studies

As solid organ transplantation becomes more prevalent, more individuals are living as members of the immunosuppressed population with an elevated risk for cutaneous squamous cell carcinoma (cSCC). Although great progress has been made in understanding the pathogenesis of cSCC in general, little is known about the drivers of tumorigenesis in immunosuppressed patients and organ-transplant recipients, specifically. This systematic review sought to synthesize information regarding the genetic and epigenetic alterations as well as changes in protein and mRNA expression that place this growing population at risk for cSCC, influence treatment response, and promote tumor aggressiveness. This review will provide investigators with a framework to identify future areas of investigation and clinicians with additional insight into how to best manage these patients.

Repurposing econazole as a pharmacological autophagy inhibitor to treat pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by the highest mortality among carcinomas. The pathogenesis of PDAC requires elevated autophagy, inhibition of which using hydroxychloroquine has shown promise. However, current realization is impeded by its suboptimal use and unpredictable toxicity. Attempts to identify novel autophagy-modulating agents from already approved drugs offer a rapid and accessible approach. Here, using a patient-derived organoid model, we performed a comparative analysis of therapeutic responses among various antimalarial/fungal/parasitic/viral agents, through which econazole (ECON), an antifungal compound, emerged as the top candidate. Further testing in cell-line and xenograft models of PDAC validated this activity, which occurred as a direct consequence of dysfunctional autophagy. More specifically, ECON boosted autophagy initiation but blocked lysosome biogenesis. RNA sequencing analysis revealed that this autophagic induction was largely attributed to the altered expression of activation transcription factor 3 (ATF3). Increased nuclear import of ATF3 and its transcriptional repression of inhibitor of differentiation-1 (ID-1) led to inactivation of the AKT/mammalian target of rapamycin (mTOR) pathway, thus giving rise to autophagosome accumulation in PDAC cells. The magnitude of the increase in autophagosomes was sufficient to elicit ER stress-mediated apoptosis. Furthermore, ECON, as an autophagy inhibitor, exhibited synergistic effects with trametinib on PDAC. This study provides direct preclinical and experimental evidence for the therapeutic efficacy of ECON in PDAC treatment and reveals a mechanism whereby ECON inhibits PDAC growth.

Multifaceted roles of HSF1 in cell death: A state-of-the-art review

Cell death is a common and active process that is involved in various biological processes, including organ development, morphogenesis, maintaining tissue homeostasis and eliminating potentially harmful cells. Abnormal regulation of cell death significantly contributes to tumor development, progression and chemoresistance. The mechanisms of cell death are complex and involve not only apoptosis and necrosis but also their cross-talk with other types of cell death, such as autophagy and the newly identified ferroptosis. Cancer cells are chronically exposed to various stresses, such as lack of oxygen and nutrients, immune responses, dysregulated metabolism and genomic instability, all of which lead to activation of heat shock factor 1 (HSF1). In response to heat shock, oxidative stress and proteotoxic stresses, HSF1 upregulates transcription of heat shock proteins (HSPs), which act as molecular chaperones to protect normal cells from stresses and various diseases. Accumulating evidence suggests that HSF1 regulates multiple types of cell death through different signaling pathways as well as expression of distinct target genes in cancer cells. Here, we review the current understanding of the potential roles and molecular mechanism of HSF1 in regulating apoptosis, autophagy and ferroptosis. Deciphering HSF1-regulated signaling pathways and target genes may help in the development of new targeted anti-cancer therapeutic strategies.

ATF3 downmodulates its new targets IFI6 and IFI27 to suppress the growth and migration of tongue squamous cell carcinoma cells

Activating transcription factor 3 (ATF3) is a key transcription factor involved in regulating cellular stress responses, with different expression levels and functions in different tissues. ATF3 has also been shown to play crucial roles in regulating tumor development and progression, however its potential role in oral squamous cell carcinomas has not been fully explored. In this study, we examined biopsies of tongue squamous cell carcinomas (TSCCs) and found that the nuclear expression level of ATF3 correlated negatively with the differentiation status of TSCCs, which was validated by analysis of the ATGC database. By using gain- or loss- of function analyses of ATF3 in four different TSCC cell lines, we demonstrated that ATF3 negatively regulates the growth and migration of human TSCC cells in vitro. RNA-seq analysis identified two new downstream targets of ATF3, interferon alpha inducible proteins 6 (IFI6) and 27 (IFI27), which were upregulated in ATF3-deleted cells and were downregulated in ATF3-overexpressing cells. Chromatin immunoprecipitation assays showed that ATF3 binds the promoter regions of the IFI6 and IFI27 genes. Both IFI6 and IFI27 were highly expressed in TSCC biopsies and knockdown of either IFI6 or IFI27 in TSCC cells blocked the cell growth and migration induced by the deletion of ATF3. Conversely, overexpression of either IFI6 or IFI27 counteracted the inhibition of TSCC cell growth and migration induced by the overexpression of ATF3. Finally, an in vivo study in mice confirmed those in vitro findings. Our study suggests that ATF3 plays an anti-tumor function in TSCCs through the negative regulation of its downstream targets, IFI6 and IFI27.

Activating transcription factor 3 (ATF3), a stress response gene, has been shown to play either tumor promoting or tumor suppressing functions depending on the type of tumor cell and the stromal context. Here we discovered that ATF3 plays an anti-tumor role in tongue squamous cell carcinoma (TSCC) cells through the transcriptional suppression of its new downstream targets interferon alpha inducible proteins 6 (IFI6) and 27 (IFI27). This finding contributes to understanding how ATF3, a transcriptional repressor, can target specific downstream genes in different tumor cells to play anti-tumor or pro-tumor functions. A thorough understanding of ATF3 functions and its downstream signaling pathways provides a potential approach to develop new therapeutics for the treatment of tumors such as TSCCs.

Recurrent squamous cell carcinoma in a post cardiac transplant patient

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Patient having recurrent carcinomas following heart transplant due to possible immunosuppression.

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Early Cancer surveillance in transplant patients is necessary to detect and treat malignancies early.

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Unique in having two recurrences post-transplant.

Introduction and importance

Solid organ transplantation has evolved along with dramatic advancements in definitive treatment for irreversible and uncompensated organ failure. Transplanted organ survival has improved as a result of reduced allograft rejection. However, negative long-term outcomes which were largely due to the adverse effects of rapidly evolving immunosuppressive regimens are still evident. The emergence of malignancies following prolonged exposure to immunosuppression treatment has affected the quality of life in transplant recipients. They are approximately one hundred times more likely to develop squamous cell carcinoma (SCC) compared to the general population and the incidence of malignant melanomas, basal cell carcinomas, and Kaposi’s sarcomas are also on the rise. The incidence of de novo malignancies ranges from 9 to 21% and is commonly seen in the skin and the lymphoreticular system in these patients.

Case presentation

A 78-year-old male presented with a lump in the right axilla, which had grown in size over a 4-week period. Patient had received a cardiac transplant 9 years prior and was on a regimen of Tacrolimus and Mycophenolate Mofetil since then.

Clinical discussion

Following 4 years of immunosuppression therapy, the patient developed a non-healing ulcer on his right forearm and the biopsy confirmed SCC. The recent biopsy performed on the new axillary lump also confirmed SCC. Iatrogenic immune suppressive treatment is associated with the occurrence of de novo, non-melanoma skin cancers in the solid organ transplant recipients and this necessitates early and comprehensive cancer surveillance models to be included in the pre and post-transplant assessment.

Conclusion

Advances in immunology suggest that peripheral blood mononuclear cell sequencing and immune profiling to identify immune phenotypes associated with keratinocyte cancers allow us to recognize patients who are more susceptible for SCC following organ transplantation and immunosuppression.

NRF2 and the Ambiguous Consequences of Its Activation during Initiation and the Subsequent Stages of Tumourigenesis

NF-E2 p45-related factor 2 (NRF2, encoded in the human by NFE2L2) mediates short-term adaptation to thiol-reactive stressors. In normal cells, activation of NRF2 by a thiol-reactive stressor helps prevent, for a limited period of time, the initiation of cancer by chemical carcinogens through induction of genes encoding drug-metabolising enzymes. However, in many tumour types, NRF2 is permanently upregulated. In such cases, its overexpressed target genes support the promotion and progression of cancer by suppressing oxidative stress, because they constitutively increase the capacity to scavenge reactive oxygen species (ROS), and they support cell proliferation by increasing ribonucleotide synthesis, serine biosynthesis and autophagy. Herein, we describe cancer chemoprevention and the discovery of the essential role played by NRF2 in orchestrating protection against chemical carcinogenesis. We similarly describe the discoveries of somatic mutations in NFE2L2 and the gene encoding the principal NRF2 repressor, Kelch-like ECH-associated protein 1 (KEAP1) along with that encoding a component of the E3 ubiquitin-ligase complex Cullin 3 (CUL3), which result in permanent activation of NRF2, and the recognition that such mutations occur frequently in many types of cancer. Notably, mutations in NFE2L2, KEAP1 and CUL3 that cause persistent upregulation of NRF2 often co-exist with mutations that activate KRAS and the PI3K-PKB/Akt pathway, suggesting NRF2 supports growth of tumours in which KRAS or PKB/Akt are hyperactive. Besides somatic mutations, NRF2 activation in human tumours can occur by other means, such as alternative splicing that results in a NRF2 protein which lacks the KEAP1-binding domain or overexpression of other KEAP1-binding partners that compete with NRF2. Lastly, as NRF2 upregulation is associated with resistance to cancer chemotherapy and radiotherapy, we describe strategies that might be employed to suppress growth and overcome drug resistance in tumours with overactive NRF2.

Up-Regulation of Activating Transcription Factor 3 in Human Fibroblasts Inhibits Melanoma Cell Growth and Migration Through a Paracrine Pathway

The treatment of melanoma has remained a difficult challenge. Targeting the tumor stroma has recently attracted attention for developing novel strategies for melanoma therapy. Activating transcription factor 3 (ATF3) plays a crucial role in regulating tumorigenesis and development, but whether the expression of ATF3 in human dermal fibroblasts (HDFs) can affect melanoma development hasn't been studied. Our results show that ATF3 expression is downregulated in stromal cells of human melanoma. HDFs expressing high levels of ATF3 suppressed the growth and migration of melanoma cells in association with downregulation of different cytokines including IL-6 in vitro. In vivo, HDFs with high ATF3 expression reduced tumor formation. Adding recombinant IL-6 to melanoma cells reversed those in vitro and in vivo effects, suggesting that ATF3 expression by HDFs regulates melanoma progression through the IL-6/STAT3 pathway. More importantly, HDFs pretreated with cyclosporine A or phenformin to induce ATF3 expression inhibited melanoma cell growth in vitro and in vivo. In summary, our study reveals that ATF3 suppresses human melanoma growth and that inducing the expression of ATF3 in HDFs can inhibit melanoma growth, a new potential melanoma therapeutic approach.

Cutaneous squamous cell carcinoma in the organ transplant recipient

One in twenty solid organ transplant recipients (SOTRs) will develop a highly morbid or fatal cutaneous carcinoma after transplantation. The majority of these cases develop on the head and neck and may require intervention on the part of dermatology, dermatologic surgery, otolaryngology, transplant medicine, radiation oncology, and medical oncology. In this review, we discuss the problem of cutaneous squamous cell carcinoma (cSCC) in SOTRs as well as the prognostic factors and management strategies to care for this population.

Epidemiologic perspectives on immunosuppressed populations and the immunosurveillance and immunocontainment of cancer

The advent in the last several years of effective immunotherapy for cancer has renewed interest in the role of the immune system in controlling cancer. The idea that the immune system can help control cancer has a long history. Solid organ transplant recipients (SOTRs) as well as human immunodeficiency virus (HIV)-infected people are affected by cell-mediated immune dysfunction. Epidemiologic studies of these populations reveal a pattern characterized by a strongly increased incidence of virus-related cancers (eg, Kaposi sarcoma, non-Hodgkin lymphoma, and anogenital cancers). In addition, recent epidemiologic studies have evaluated cancer-specific mortality among SOTRs and HIV-infected people following a cancer diagnosis. For a wider range of cancers-not limited to those caused by viruses, and including melanoma and cancers of the colorectum, lung, and breast- these immunosuppressed cancer patients have higher cancer-specific mortality than other cancer patients. This latter group of cancers somewhat mirrors those for which immunotherapy with checkpoint inhibitors is approved. These epidemiologic observations suggest that there are 2 distinct immune selection processes in humans: immunosurveillance directed against premalignant cells before cancer diagnosis (most relevant for preventing virus-related cancers), and "immunocontainment" directed against established cancers. These processes thus appear relevant for different groups of malignancies and may have different mechanisms.

Nestin regulates cellular redox homeostasis in lung cancer through the Keap1-Nrf2 feedback loop

Abnormal cancer antioxidant capacity is considered as a potential mechanism of tumor malignancy. Modulation of oxidative stress status is emerging as an anti-cancer treatment. Our previous studies have found that Nestin-knockdown cells were more sensitive to oxidative stress in non-small cell lung cancer (NSCLC). However, the molecular mechanism by which Nestin protects cells from oxidative damage remains unclear. Here, we identify a feedback loop between Nestin and Nrf2 maintaining the redox homeostasis. Mechanistically, the ESGE motif of Nestin interacts with the Kelch domain of Keap1 and competes with Nrf2 for Keap1 binding, leading to Nrf2 escaping from Keap1-mediated degradation, subsequently promoting antioxidant enzyme generation. Interestingly, we also map that the antioxidant response elements (AREs) in the Nestin promoter are responsible for its induction via Nrf2. Taken together, our results indicate that the Nestin-Keap1-Nrf2 axis regulates cellular redox homeostasis and confers oxidative stress resistance in NSCLC.

Dissecting the Multiplicity of Immune Effects of Immunosuppressive Drugs to Better Predict the Risk of de novo Malignancies in Solid Organ Transplant Patients

De novo malignancies constitute an emerging cause of morbidity after solid organ transplant (SOT), significantly affecting the long-term survival of transplant recipients. Pharmacologic immunosuppression may functionally impair the immunosurveillance in these patients, thereby increasing the risk of cancer development. Nevertheless, the multiplicity and heterogeneity of the immune effects induced by immunosuppressive drugs limit the current possibilities to reliably predict the risk of de novo malignancy in SOT patients. Therefore, there is the pressing need to better characterize the immune dysfunctions induced by the different immunosuppressive regimens administered to prevent allograft rejection to tailor more precisely the therapeutic schedule and decrease the risk of de novo malignancies. We herein highlight the impact exerted by different classes of immunosuppressants on the most relevant immune cells, with a particular focus on the effects on dendritic cells (DCs), the main regulators of the balance between immunosurveillance and tolerance.

The antioxidant transcription factor Nrf2 modulates the stress response and phenotype of malignant as well as premalignant pancreatic ductal epithelial cells by inducing expression of the ATF3 splicing variant ΔZip2

Pancreatic ductal adenocarcinoma (PDAC) exhibits one of the worst survival rates of all cancers. While death rates show declining trends in the majority of cancers, PDAC registers rising rates. Based on the recently described crosstalk between TGF-β1 and Nrf2 in the PDAC development, the involvement of ATF3 and its splice variant ΔZip2 in TGF-β1- and Nrf2-driven pancreatic tumorigenesis was investigated. As demonstrated here, PDAC (Panc1, T3M4) cells or premalignant H6c7 pancreatic ductal epithelial cells differentially express ΔZip2- and ATF3, relating to stronger Nrf2 activity seen in Panc1 cells and TGF-ß1 activity in T3M4 or H6c7 cells, respectively. Treatment with the electrophile/oxidative stress inducer tBHQ or the cytostatic drug gemcitabine strongly elevated ΔZip2 expression in a Nrf2-dependent fashion. The differential expression of ATF3 and ΔZip2 in response to Nrf2 and TGF-ß1 relates to differential ATF3-gene promoter usage, giving rise of distinct splice variants. Nrf2-dependent ΔZip2 expression confers resistance against gemcitabine-induced apoptosis, only partially relating to interference with ATF3 and its proapoptotic activity, e.g., through CHOP-expression. In fact, ΔZip2 autonomously activates expression of cIAP anti-apoptotic proteins. Moreover, ΔZip2 favors and ATF3 suppresses growth and clonal expansion of PDAC cells, again partially independent of each other. Using a Panc1 tumor xenograft model in SCID-beige mice, the opposite activities of ATF3 and ΔZip2 on tumor-growth and chemoresistance were verified in vivo. Immunohistochemical analyses confirmed ΔZip2 and Nrf2 coexpression in cancerous and PanIN structures of human PDAC and chronic pancreatitis tissues, respectively, which to some extent was reciprocal to ATF3 expression. It is concluded that depending on selective ATF3-gene promoter usage by Nrf2, the ΔZip2 expression is induced in response to electrophile/oxidative (here through tBHQ) and xenobiotic (here through gemcitabine) stress, providing apoptosis protection and growth advantages to pancreatic ductal epithelial cells. This condition may substantially add to pancreatic carcinogenesis driven by chronic inflammation.

EGR1 is essential for deoxynivalenol-induced G2/M cell cycle arrest in HepG2 cells via the ATF3ΔZip2a/2b-EGR1-p21 pathway

Deoxynivalenol (DON) is a type B trichothecene mycotoxin that exerts multiple toxic effects on plants, animals and humans. Several reports have shown that DON leads to G2/M cell cycle arrest. However, its molecular mechanism is still unclear. In this study, we showed that DON induced strong G2/M cell cycle arrest in HepG2 cells, and the cell cycle-inhibitory protein p21 was highly upregulated by DON. Further analysis showed that the cell cycle regulating gene EGR1 was highly induced by DON and that EGR1 knockdown abolished the upregulation of p21 and G2/M cell cycle arrest. Furthermore, we showed that the induction of EGR1 was regulated by the stress-responsive transcription factor ATF3. ATF3ΔZip2a/2b, which is a DNA binding domain truncated isoform of ATF3, was upregulated by DON. ATF3 knockdown weakened the expression induction of EGR1 and G2/M cell cycle arrest by DON. Moreover, the upregulation of ATF3ΔZip2a/2 highly depended on the enhanced presence of histones H3K9ac and H3K27ac. H3K9ac and H3K27ac were enriched at the promoter region of ATF3 following the DON treatment, and the knocking down of the genes responsible for H3K9ac and H3K27ac abolished the upregulation of ATF3 by DON. In summary, we found that DON induced G2/M cell cycle arrest by sequentially inducing the expression of ATF3ΔZip2a/2b, EGR1 and p21, and EGR1 played an essential role in this process, which is a novel molecular mechanism of cell cycle arrest by DON and is important for understanding its toxicology.

The mTOR-inhibitor Sirolimus decreases the cyclosporine-induced expression of the oncogene ATF3 in human keratinocytes

BACKGROUND

Due to their immunosuppressive therapy, organtransplant recipients (OTRs) exhibit a high incidence for the development of cutaneous squamous cell carcinoma (cSCC). Randomized studies of kidney-transplanted patients indicate a significant lower susceptibility for cSCC among patients receiving the mTOR-inhibitor Sirolimus, compared to patients without mTOR-regimen. The exact mechanism, how mTOR inhibition affects keratinocyte carcinogenesis remains unclear.

OBJECTIVE

Our aim was to investigate the impact of Sirolimus on the expression level of the oncogene ATF3, which is involved in the development and progression of cSCC.

METHODS

We incubated human keratinocytes, cSSC cell lines and 3D skin equivalents with Sirolimus, exposed the cells to calcineurin inhibitors (CNI) and UVA-radiation and measured the expression level of ATF3 by real-time PCR and western blot.

RESULTS

We show that Sirolimus downregulates the expression of ATF3 induced by cyclosporine or cyclosporine plus UV-radiation in keratinocytes. In line with this we demonstrate a decrease in ATF3 expression, by incubating 3D skin equivalents with Sirolimus prior to cyclosporine and UV-light. However, Sirolimus has no significant impact on the ATF3 expression levels of cyclosporine stimulated cSCC cell lines.

CONCLUSION

Taken together, our study demonstrates that Sirolimus downregulates the CNI or UV-induced ATF3 expression in human keratinocytes, which could be a potential molecular mechanism how Sirolimus reduces cSCC in OTRs. The lack of ATF3 suppression by Sirolimus in cSCC cell lines fits to observations from clinical studies which demonstrated a clinical benefit from the switch to a mTOR-regimen in patients with low tumor burden in early stage of disease.

Skin Cancer Following Solid Organ Transplantation: A Review of Risk Factors and Models of Care

The number of solid organ transplants has been increasing annually worldwide. Advances in transplantation surgery and community awareness of organ donation have been key contributors. Combined with increased understanding of immunosuppression, there are a growing number of solid organ transplant recipients in the community as a result of improved long-term outcomes. There remains a high incidence of deaths worldwide post-transplant due to non-melanoma skin cancer (NMSC), which has greater morbidity and mortality in this population than in the general community. Many transplant candidates are not screened prior to organ transplantation and not followed up dermatologically after transplant. After a comprehensive review of the MEDLINE database, we present an update of literature on risk factors for melanoma and non-melanoma skin cancer development in transplant recipients. Medications used by transplant recipients, including immunosuppressants and antibiotics, are discussed along with their respective risks of skin cancer development. We conclude with evidence-based recommendations for models of care, including patient education and dermatological review of transplant recipients.

Cutaneous complications of immunosuppression in 812 transplant recipients: a 40-year single center experience

BACKGROUND

As a consequence of the improvement in survival after solid organ transplantation, to visit transplant recipients with neoplastic and non-neoplastic skin disorders due to immunosuppressive treatment has become common for dermatologists.

METHODS

Our endpoints were: 1) to investigate the most common skin diseases in a population of transplant recipients; 2) their associations with the type of immunosuppressant or transplant received; and 3) to compare our single center 40-year experience with the literature data. We retrospectively analyzed the clinical details of the adult patients transplanted in the years 1974-2014, visited for consultation at the Unit of Dermatology of our hospital.

RESULTS

Pathologic conditions were observed in more than 3/4 of 812 adults during the follow-up (mean 12.1 years): nonmelanoma skin cancers or actinic keratoses were seen in 44.0% (N.=357) of patients, non-neoplastic events in 55.2% (N.=448). Heart transplant had the statistically significant highest rate of NMSC and AK (52.6%, P=0.0352). Patients receiving cyclosporine A developed at least one non-melanoma skin cancer or actinic keratosis in 57.7% of cases (P=0.0001), while tacrolimus showed a lower risk (33%, P=0.0001).

CONCLUSIONS

As transplant recipients are susceptible to skin changes, especially after immunosuppressant treatments, a dermatological follow-up should be scheduled for each patient.

Sirolimus for Secondary Prevention of Skin Cancer in Kidney Transplant Recipients: 5-Year Results

Purpose Transplant recipients who develop cutaneous squamous cell carcinomas are at high risk for multiple subsequent skin cancers. Sirolimus has been shown to reduce the occurrence of secondary skin cancers, but no study included a follow-up exceeding 2 years. We extended at 5 years the TUMORAPA randomized trial of sirolimus-based immunosuppressive regimen versus calcineurin inhibitor-based immunosuppression. Methods Kidney transplant recipients receiving calcineurin inhibitors who had at least one cutaneous squamous cell carcinoma were randomly assigned to receive sirolimus as a substitute for calcineurin inhibitors (n = 64) or to maintain their initial treatment (n = 56). The primary end point was survival free of squamous cell carcinoma at 5 years. Secondary end points included the occurrence of other skin cancers, renal function, patient and graft survival, and treatment tolerance. Results Survival free of cutaneous squamous cell carcinoma was significantly longer in the sirolimus group than in the calcineurin inhibitor group ( P = .007). In the sirolimus group, the number of patients with new skin cancers was significantly lower compared with the calcineurin inhibitor group: 22% versus 59% for squamous cell carcinomas ( P < .001), 34% versus 66% for other skin cancers ( P < .001), and 20% versus 37.5% for basal cell carcinomas ( P < .05). Kidney graft function, patients, and graft survival were similar in both groups. In the sirolimus group, the mean number of serious adverse effects per patient decreased from 1.16 during the first 2 years, to 0.83 between years 2 and 5. Conclusion In kidney transplant recipients with previous cutaneous squamous cell carcinomas, the antitumoral effect of conversion from calcineurin inhibitors to sirolimus was maintained at 5 years, and sirolimus tolerance was satisfactory.

The ARE-binding protein Tristetraprolin (TTP) is a novel target and mediator of calcineurin tumor suppressing function in the skin

An increased incidence of skin inflammatory diseases is frequently observed in organtransplanted patients being treated with calcineurin inhibitor-based immunosuppressive agents. The mechanism of increased skin inflammation in this context has however not yet been clarified. Here we report an increased inflammation following inhibition of calcineurin signaling seen in both chemically induced mouse skin tumors and in tumors grafted from H-rasV12 expressing primary human keratinocytes (HKCs). Following UVB or TPA treatment, we specifically found that deletion of the calcineurin gene in mouse keratinocytes (MKCs) resulted in increased inflammation, and this was accompanied by the enhanced production of pro-inflammatory cytokines, such as TNFα, IL-8 and CXCL1. Furthermore, expression of the RNA-binding protein, tristetraprolin (TTP) was down-regulated in response to calcineurin inhibition, wherein TTP was shown to negatively regulate the production of pro-inflammatory cytokines in keratinocytes. The induction of TTP following TPA or UVB treatment was attenuated by calcineurin inhibition in keratinocytes, and correspondingly, disruption of calcineurin signaling down-regulated the amounts of TTP in both clinical and H-rasV12-transformed keratinocyte tumor models. Our results further demonstrated that calcineurin positively controls the stabilization of TTP in keratinocytes through a proteasome-dependent mechanism. Reducing the expression of TTP functionally promoted tumor growth of H-rasV12 expressing HKCs, while stabilizing TTP expression counteracted the tumor-promoting effects of calcineurin inhibition. Collectively these results suggest that calcineurin signaling, acting through TTP protein level stabilization, suppresses keratinocyte tumors by downregulating skin inflammation.

Downregulated TRPV1 Expression Contributes to Melanoma Growth via the Calcineurin-ATF3-p53 Pathway

Melanoma is the most lethal form of skin cancer with increasing incidence over the years. Because of its rapid proliferative and drastic metastatic capacity, the prognosis of melanoma remains dismal, although the targeted therapy and immunotherapy have gained revolutionary progress recently. Therefore, it is of necessity to further clarify the mechanism of melanoma pathogenesis for developing an alternative treatment strategy. Transient receptor potential vanilloid 1 (TRPV1) is a nonselective Ca²⁺ channel greatly involved in regulating cell apoptosis, proliferation, metabolism, and cancer development, but its role in melanoma remains unknown. Herein, we first found that TRPV1 expression was significantly decreased in melanoma tissues and cell lines, compared with nevus tissues and normal melanocytes, respectively. We then proved that TRPV1 overexpression or its agonist capsaicin treatment inhibited melanoma growth by activating p53 and inducing cell apoptosis. A subsequent mechanistic study revealed that TRPV1 induced Ca²⁺ influx to regulate p53 activation via calcineurin-ATF3 transcriptional cascade. Finally, the effect of TRPV1 on melanoma growth was proved in vivo. Altogether, our study demonstrates that TRPV1 is a potential tumor suppressor in melanoma.

Effects of mammalian target of rapamycin inhibitors on cytokine production and differentiation in keratinocytes

Risk factors for the development of cutaneous squamous cell carcinoma (cSCC) include ultraviolet radiation and immunosuppression. In particular, solid organ transplant recipients show a high incidence of cSCC, depending on the immunosuppressive regimen. While azathioprine or calcineurin inhibitors increase the risk of cSCC development, mammalian target of rapamycin (mTOR) inhibitors decreases this risk. At the moment, the mechanisms behind this protective effect of mTOR inhibitors are not fully understood. We evaluated effects of the mTOR inhibitors sirolimus and everolimus on keratinocytes, cSCC cell lines and an organotypic skin model in vitro in regard to proliferation, cytokine secretion and differentiation. We show that mTOR inhibitors block keratinocyte proliferation and alter cytokine and cytokeratin production: in particular, mTOR inhibition leads to upregulation of interleukin-6 and downregulation of cytokeratin 10. Therefore, mTOR inhibitors have effects on keratinocytes, which could play a role in the pathogenesis of cSCC.

The pathogenesis of cutaneous squamous cell carcinoma in organ transplant recipients

The pathogenesis of keratinocyte carcinoma following organ transplantation is multifactorial, and recent evidence suggests a complex and often synergistic interplay between the carcinogenic effects of ultraviolet radiation, compromised immune surveillance, direct pro- and anticarcinogenic effects of drugs, oncogenic viruses (in particular, beta-genus human papillomaviruses) and host genetic susceptibility factors. We present an overview of those factors for which there is currently the most convincing evidence and highlight important gaps in our knowledge. In particular, a clear understanding of the interdependence and relative contributions of these co-factors is currently lacking, yet has important implications for rational development of clinically relevant biomarkers and targeted strategies for treatment and prevention of post-transplant keratinocyte cancers.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare but highly aggressive skin cancer with neuroendocrine features. MCC pathogenesis is associated with either the presence of Merkel cell polyomavirus or chronic exposure to ultraviolet light (UV), which can cause a characteristic pattern of multiple DNA mutations. Notably, in the Northern hemisphere, the majority of MCC cases are of viral aetiology; by contrast, in areas with high UV exposure, UV-mediated carcinogenesis is predominant. The two aetiologies share similar clinical, histopathological and prognostic characteristics. MCC presents with a solitary cutaneous or subcutaneous nodule, most frequently in sun-exposed areas. In fact, UV exposure is probably involved in both viral-mediated and non-viral-mediated carcinogenesis, by contributing to immunosuppression or DNA damage, respectively. Confirmation of diagnosis relies on analyses of histological features and immunological marker expression profiles of the lesion. At primary diagnosis, loco-regional metastases are already present in ∼30% of patients. Excision of the tumour is the first-line therapy; if not feasible, radiotherapy can often effectively control the disease. Chemotherapy was the only alternative in advanced-stage or refractory MCC until several clinical trials demonstrated the efficacy of immune-checkpoint inhibitors.

TLR4 as a negative regulator of keratinocyte proliferation

TLR4 is an innate immune receptor with expression in human skin, keratinocytes as well as squamous cell carcinoma (SCC) of the skin. In the present study we investigate the role of TLR4 as a negative regulator of keratinocyte proliferation. We present here that the expression of TLR4 increased with the differentiation of cultured keratinocytes in a passage-dependent manner or under calcium-rich conditions. Moreover, the down-regulation of TLR4 by specific knockdown increased the proliferation of HaCaT keratinocytes in vitro. In addition, subcutaneously injected HaCaT keratinocytes with shTLR4 formed growing tumors in nude mice. In contrast, we observed lower proliferation and increased migration in vitro of the SCC13 cell line stably overexpressing TLR4 in comparison to SCC13 TLR4 negative cells. In vivo, SCC13 TLR4-overexpressing tumors showed delayed growth in comparison to TLR4 negative tumors. The overexpression of TLR4 in SCC13 tumor cells was followed by phosphorylation of ERK1/2 and JNK and increased expression of ATF3. In gene expression arrays, the overexpression of TLR4 in tumor cells correlated with gene expression of ATF-3, IL-6, CDH13, CXCL-1 and TFPI. In summary, TLR4 negatively regulates the proliferation of keratinocytes and its overexpression reduces tumor growth of SCC cells.

Black-odor water analysis and heavy metal distribution of Yitong River in Northeast China

The black-odor mechanism of Yitong River was analyzed based on survey and monitoring results. We found that organic matter is the main pollution source of Yitong River and its tributaries. A black-odor evaluation model that can describe the pollution of the Yitong River water system was developed, and this model has the parameters I = 0.21 [COD_Cr] + 0.18 [DO] - 0.36[NH₃-N] + 0.91. The model performance was satisfactory with a black-odor defining accuracy of 69%. Moreover, we found that COD_Cr, NH₃-N, and DO are the influential factors of the Yitong River black-odor water body and that their threshold values when the water body transitioned to black odor were 109.2, 1.90, and 7.50 mg·L^-1, respectively. We found that most of the Yitong River was polluted by six heavy metals, namely, As, Cd, Cr, Cu, Pb, and Zn. We used the Nemerow method to calculate the heavy metal pollution degree of each sampling point and found that 60% of the points were seriously polluted. Furthermore, we drew the heavy metal pollution distribution map of the Yitong River. Finally, we proposed an effective measure called new-type multistep constructed wetland to improve the water quality of Yitong River.

Differential induction of ATF3 and HO-1 in myeloid cells and keratinocytes via Dimethylfumarate or Cyclosporine A

BACKGROUND

Chronic inflammatory skin diseases are characterized by controlled proliferation of keratinocytes. Here, activating transcription factor 3 (ATF3) might play a fundamental role. In these inflammatory diseases, proliferation is controlled and only rarely leads to cancer development which can be supported by an inflammatory microenvironment. ATF3 is a dual function protein as it suppresses pro-inflammatory IL-6 and IL-8, but also acts as a pro-oncogenic factor by the suppression of p53. We therefore analyzed ATF3 expression comparing myeloid cells with keratinocytes.

OBJECTIVE

To dissect the bi-modal role of ATF3 we pharmacologically induced ATF3 and analyzed its influence on cytokine expression and secretion in a cell type specific manner.

METHODS

Since inflammatory skin diseases can be treated systemically with Cyclosporin A or Dimethylfumarate we stimulated myeloid cells and primary human keratinocytes with these drugs and analyzed gene expression by quantitative real-time PCR. Cytokine secretion was measured by ELISA.

RESULTS

In the present study, we could show that ATF3 is induced in PBMCs by DMF and weakly by Ebselen, while CsA is the most prominent inducer of ATF3 in keratinocytes without enhancing HO-1 transcription. Further we could show that induction of stress by LPS treatment elevates IL-1β and IL-6 and weakly ATF3 transcription in PBMCs. While transcription of both cytokines is elevated, LPS treatment mediates IL-6 secretion with only little IL-1β secretion. Treatment with DMF dampens LPS-induced transcription.

CONCLUSIONS

Taken together, our results shed light into the different carcinogenic potential of CsA and DMF, which both target ATF3. Collectively our data demonstrate that CsA strongly induces pro-carcinogenic ATF3 in keratinocytes, whereas ATF3 induction by DMF in myeloid cells acts anti-inflammatory.

Squamous Cell Cancers: A Unified Perspective on Biology and Genetics

Squamous cell carcinomas (SCCs) represent the most frequent human solid tumors and are a major cause of cancer mortality. These highly heterogeneous tumors arise from closely interconnected epithelial cell populations with intrinsic self-renewal potential inversely related to the stratified differentiation program. SCCs can also originate from simple or pseudo-stratified epithelia through activation of quiescent cells and/or a switch in cell-fate determination. Here, we focus on specific determinants implicated in the development of SCCs by recent large-scale genomic, genetic, and epigenetic studies, and complementary functional analysis. The evidence indicates that SCCs from various body sites, while clinically treated as separate entities, have common determinants, pointing to a unified perspective of the disease and potential new avenues for prevention and treatment.

Gankyrin has an antioxidative role through the feedback regulation of Nrf2 in hepatocellular carcinoma

Yang et al. identify a feedback loop between gankyrin, an oncoprotein overexpressed in human hepatocellular carcinoma (HCC), and Nrf2. The positive feedback modulates a series of antioxidant enzymes that lower intracellular reactive oxygen species to confer protection from mitochondrial damage and cell death.

Oxidative stress status has a key role in hepatocellular carcinoma (HCC) development and progression. Normally, reactive oxygen species (ROS) levels are tightly controlled by an inducible antioxidant program that responds to cellular stressors. How HCC cells respond to excessive oxidative stress remains elusive. Here, we identified a feedback loop between gankyrin, an oncoprotein overexpressed in human HCC, and Nrf2 maintaining the homeostasis in HCC cells. Mechanistically, gankyrin was found to interact with the Kelch domain of Keap1 and effectively competed with Nrf2 for Keap1 binding. Increased expression of gankyrin in HCC cells blocked the binding between Nrf2 and Keap1, inhibiting the degradation of Nrf2 by proteasome. Interestingly, accumulation and translocation of Nrf2 increased the transcription of gankyrin through binding to the ARE elements in the promoter of gankyrin. The positive feedback regulation involving gankyrin and Nrf2 modulates a series of antioxidant enzymes, thereby lowering intracellular ROS and conferring a steadier intracellular environment, which prevents mitochondrial damage and cell death induced by excessive oxidative stress. Our results indicate that gankyrin is a regulator of cellular redox homeostasis and provide a link between oxidative stress and the development of HCC.

Nrf2--A regulator of keratinocyte redox signaling

The skin is frequently exposed to environmental challenges, such as UV irradiation, toxic chemicals, and mechanical wounding. These insults cause an increase in the levels of reactive oxygen species, resulting in oxidative stress and concomitant inflammation, skin aging, and even cancer development. Therefore, an efficient antioxidant defense strategy is of major importance in this tissue. Since the Nrf2 transcription factor regulates a battery of genes involved in the defense against reactive oxygen species and in compound metabolism, it plays a key role in skin homeostasis, repair, and disease. In this review we summarize current knowledge on the expression and function of Nrf2 in normal skin and its role in the acute and chronic UV response as well as in the pathogenesis of epithelial skin cancer and of different inflammatory skin diseases. Finally, we discuss the potential of Nrf2-activating compounds for skin protection under stress conditions and for the treatment of major human skin disorders.

Ingenol Mebutate Signals via PKC/MEK/ERK in Keratinocytes and Induces Interleukin Decoy Receptors IL1R2 and IL13RA2

Squamous cell carcinoma (SCC) is the second most common human skin cancer and the second leading cause of skin cancer-related death. Recently, a new compound, ingenol mebutate, was approved for treatment of actinic keratosis, a precursor of SCC. As the mechanism of action is poorly understood, we have further investigated the mechanism of ingenol mebutate-induced cell death. We elucidate direct effects of ingenol mebutate on primary keratinocytes, patient-derived SCC cells, and a SCC cell line. Transcriptional profiling followed by pathway analysis was performed on ingenol mebutate-treated primary keratinocytes and patient-derived SCC cells to find key mediators and identify the mechanism of action. Activation of the resulting pathways was confirmed in cells and human skin explants and supported by a phosphorylation screen of treated primary cells. The necessity of these pathways was demonstrated by inhibition of certain pathway components. Ingenol mebutate inhibited viability and proliferation of all keratinocyte-derived cells in a biphasic manner. Transcriptional profiling identified the involvement of PKC/MEK/ERK signaling in the mechanism of action and inhibition of this signaling pathway rescued ingenol mebutate-induced cell death after treatment with 100 nmol/L ingenol mebutate, the optimal concentration for the first peak of response. We found the interleukin decoy receptors IL1R2 and IL13RA2 induced by ingenol mebutate in a PKC/MEK/ERK-dependent manner. Furthermore, siRNA knockdown of IL1R2 and IL13RA2 partially rescued ingenol mebutate-treated cells. In conclusion, we have shown that ingenol mebutate-induced cell death is mediated through the PKCδ/MEK/ERK pathway, and we have functionally linked the downstream induction of IL1R2 and IL13RA2 expression to the reduced viability of ingenol mebutate-treated cells.

S100A8/A9 stimulates keratinocyte proliferation in the development of squamous cell carcinoma of the skin via the receptor for advanced glycation-end products

Squamous cell carcinoma (SCC) is the most common neoplasm in organ transplant recipients (OTR) on long-term immunosuppression and occurs 60- to 100-fold more frequently than in the general population. Here, we present the receptor for advanced glycation end products (RAGE) and S100A8/A9 as important factors driving normal and tumor keratinocyte proliferation. RAGE and S100A8/A9 were transcriptionally upregulated in SCC compared to normal epidermis, as well as in OTR compared to immunocompetent patients (IC) with SCC. The proliferation of normal and SCC keratinocytes was induced by exposure to exogenous S100A8/A9 which in turn was abolished by blocking of RAGE. The migratory activities of normal and SCC keratinocytes were also increased upon exposure to S100A8/A9. We demonstrated that exogenous S100A8/A9 induces phosphorylation of p38 and SAPK/JNK followed by activation of ERK1/2. We hypothesize that RAGE and S100A8/A9 contribute to the development of human SCC by modulating keratinocyte growth and migration. These processes do not seem to be impaired by profound drug-mediated immunosuppression in OTR.

Transcription factors Hsf1 and Nrf2 engage in crosstalk for cytoprotection

Transcription factors heat shock factor (Hsf)1 and nuclear factor-erythroid 2 p45-related factor (Nrf)2 are critical for adaptation and survival. Each is maintained at low basal levels, but is robustly activated by various stimuli, including cysteine-reactive small molecules (inducers). Although each is regulated by distinct mechanisms, it is emerging that these transcription factors engage in crosstalk by sharing overlapping transcriptional targets, such as heat shock protein (HSP)70, p62, and activating transcription factor (ATF)3, and in certain cases, compensating for each other. Critically, activation of Hsf1 or Nrf2 affects the cellular redox balance by promoting the reduced state. Conversely, deletion of Hsf1 or Nrf2 is associated with oxidative stress and impaired mitochondrial function. Transient activation of Hsf1 and Nrf2 is cytoprotective, but their persistent upregulation may be detrimental, causing cardiomyopathy or accelerating carcinogenesis, and should be considered when designing strategies for disease prevention and treatment.