Virus-Induced Host Chemokine CCL2 in COVID-19 Pathogenesis: Potential Prognostic Marker and Target of Anti-Inflammatory Strategy.

A wide variety of inflammatory mediators, mainly cytokines and chemokines, are induced during SARS CoV-2 infection. Among these proinflammatory mediators, chemokines tend to play a pivotal role in virus-mediated immunopathology. The C-C chemokine ligand 2 (CCL2), also known as monocyte chemoattractant protein-1 (MCP-1) is a potent proinflammatory cytokine and strong chemoattractant of monocytes, macrophages and CD4+ T cells bearing C-C chemokine receptor type-2 (CCR2). Besides controlling immune cell trafficking, CCL2 is also involved in multiple pathophysiological processes including systemic hyperinflammation associated cytokine release syndrome (CRS), organ fibrosis and blood coagulation. These pathological features are commonly manifested in severe and fatal cases of COVID-19. Given the crucial role of CCL2 in COVID-19 pathogenesis, the CCL2:CCR2 axis may constitute a potential therapeutic target to control virus-induced hyperinflammation and multi-organ dysfunction. Herein we describe recent advances on elucidating the role of CCL2 in COVID-19 pathogenesis, prognosis, and a potential target of anti-inflammatory interventions.

Targeting oncogenic transcription factors in skin malignancies: An update on cancer stemness and therapeutic outcomes.

The skin is the largest organ of the human body and prone to various diseases, including cancer; thus, provides the first line of defense against exogenous biological and non-biological agents. Skin cancer, a complex and heterogenic process, with steep incidence rate often metastasizes due to poor understanding of the underlying mechanisms of pathogenesis and clinical challenges. Indeed, accumulating evidence indicates that deregulation of transcription factors (TFs) due to genetic, epigenetic and signaling distortions plays essential role in the development of cutaneous malignancies and therapeutic challenges including cancer stemness features and reprogramming. This review highlights the recent developments exploring underlying mechanisms how deregulated TFs (e.g., NF-κB, AP-1, STAT etc.,) orchestrates cutaneous onco-pathogenesis, reprogramming, stemness and poor clinical outcomes. Along this line, bioactive drugs, and their derivatives from natural and or synthetic origin has gained attention due to their multitargeting potential, potentially safer and effective therapeutic outcome for human malignancies. We also discussed therapeutic importance of targeting aberrantly expressed TFs in skin cancers with bioactive natural products and or synthetic agents.

Molecular pathogenesis of Cutaneous T cell Lymphoma: Role of chemokines, cytokines, and dysregulated signaling pathways.

Cutaneous T cell lymphomas (CTCLs) are a heterogeneous group of lymphoproliferative neoplasms that exhibit a wide spectrum of immune-phenotypical, clinical, and histopathological features. The biology of CTCL is complex and remains elusive. In recent years, the application of next-generation sequencing (NGS) has evolved our understanding of the pathogenetic mechanisms, including genetic aberrations and epigenetic abnormalities that shape the mutational landscape of CTCL and represent one of the important pro-tumorigenic principles in CTCL initiation and progression. Still, identification of the major pathophysiological pathways including genetic and epigenetic components that mediate malignant clonal T cell expansion has not been achieved. This is of prime importance given the role of malignant T cell clones in fostering T helper 2 (Th2)-bias tumor microenvironment and fueling progressive immune dysregulation and tumor cell growth in CTCL patients, manifested by the secretion of Th2-associated cytokines and chemokines. Alterations in malignant cytokine and chemokine expression patterns orchestrate the inflammatory milieu and influence the migration dynamics of malignant clonal T cells. Here, we highlight recent insights about the molecular mechanisms of CTCL pathogenesis, emphasizing the role of cytokines, chemokines, and associated downstream signaling networks in driving immune defects, malignant transformation, and disease progression. In-depth characterization of the CTCL immunophenotype and tumoral microenvironment offers a facile opportunity to expand the therapeutic armamentarium of CTCL, an intractable malignant skin disease with poor prognosis and in dire need of curative treatment approaches.

Role of non-coding RNAs in the progression and resistance of cutaneous malignancies and autoimmune diseases.

Skin, the largest organ of human body, is vital for the existence and survival of human beings. Further, developmental and physiological mechanisms associated with cutaneous biology are vital for homeostasis as their deregulations converge towards pathogenesis of a number of skin diseases, including cancer. It has now been well accepted that most of the transcribed human genome lacks protein translational potential and has been termed as non-coding RNAs (nc-RNAs), which includes circular RNA (circRNA), small nuclear RNA (snRNA), small nucleolar RNA (snoRNA), micro RNA (miRNA), long noncoding RNA (lncRNA), and piwi-interacting RNA (piRNAs). These nc-RNAs have gained great attention in both preclinical and clinical research as they are critical in most of the regulatory mechanisms of biological homeostasis and disease development by controlling the gene expression at transcriptional, post-transcriptional and epigenetic level. In this review we have illustrated how nc-RNAs are critical in the development and maintenance of cutaneous homeostasis and functioning and also, most importantly, how the dysregulated expression and functioning of nc-RNAs play critical role in the pathogenesis of cutaneous diseases including cancer and the autoimmune skin diseases. Considering the vital role of nc-RNAs in cancer resistance, metastasis and autoimmune diseases, we have also highlighted their role as promising prognostic and therapeutic targets for the cutaneous diseases.

The PLAUR signaling promotes chronic pruritus.

Chronic itch is a complex sensation of the skin frequently associated with skin diseases, such as atopic dermatitis (AD) and psoriasis. Although Serpin E1 is implicated in chronic itch, its receptor and signaling pathways involved in itch are not known. In this study, the clinical relevance of a putative Serpin E1 receptor PLAUR to chronic itch, and the neuro-cutaneous Serpin E1-PLAUR signaling are explored. We found that PLAUR is overexpressed in skin specimens of human lesional AD and lesional psoriasis, and sensory neurons innervating MC903-induced AD-like murine skin. Murine PLAUR+ sensory neurons responded to Serpin E1, resulting in enrichment of numerous itch- and inflammation-related genes and their protein release. PLAUR resides in TLR2+ neurons and Serpin E1 stimulus led to transcriptional upregulation of TLR2 and its co-signaling proteins. Agonists of TLR2 propagated itch-related gene transcription including BNP, OSM, and PAR2. OSM induced acute itch in mice and promoted G-CSF and IL-8 release from human keratinocytes. Serpin E1 inhibitor reduced MC903-induced itch, epidermal hyperplasia, immunocyte infiltration, and resulted in lower transcription/expression levels of Serpin E1 and OSM. Taken together, the PLAUR-TLR2-OSM signaling promotes skin-nerve communication, cutaneous inflammation, and itch, all feeding into an aggravation of AD and exaggerated itch circuits.

Neuroimmune communication regulating pruritus in atopic dermatitis.

Atopic dermatitis (AD) is a common, chronic-relapsing inflammatory skin disease with significant disease burden. Genetic and environmental trigger factors contribute to AD, activating 2 of our largest organs, the nervous system and the immune system. Dysregulation of neuroimmune circuits plays a key role in the pathophysiology of AD, causing inflammation, pruritus, pain, and barrier dysfunction. Sensory nerves can be activated by environmental or endogenous trigger factors, transmitting itch stimuli to the brain. On stimulation, sensory nerve endings also release neuromediators into the skin, contributing again to inflammation, barrier dysfunction, and itch. In addition, dysfunctional peripheral and central neuronal structures contribute to neuroinflammation, sensitization, nerve elongation, and neuropathic itch, thus chronification and therapy resistance. Consequently, neuroimmune circuits in skin and central nervous system may be targets to treat pruritus in AD. Cytokines, chemokines, proteases, lipids, opioids, and ions excite/sensitize sensory nerve endings, which not only induces itch but further aggravates/perpetuates inflammation, skin barrier disruption, and pruritus as well. Thus, targeted therapies for neuroimmune circuits as well as pathway inhibitors (eg, kinase inhibitors) may be beneficial to control pruritus in AD either in systemic and/or in topical form. Understanding neuroimmune circuits and neuronal signaling will optimize our approach to control all pathological mechanisms in AD, inflammation, barrier dysfunction, and pruritus.

Efficacy of Dupilumab in severe Atopic Dermatitis (AD) using the AD Control Tool (ADCT) Score in the population of Qatar.

Atopic Dermatitis (AD) is a high-burden disease that affects approximately 2-5% of adults. AD patients experience intense pruritus and often report sleep and mental health disturbances accompanied by a diminished quality of life. The patients' perceptions of their treatment benefits are becoming increasingly important in the benefit/risk assessment of therapeutics such as the gold standard in AD therapy, Dupilumab. A survey questionnaire (ADCT) has been recently developed to assess the control of AD symptoms using subjective patient-based reporting only. This study aimed to investigate the self-reported efficacy of Dupilumab in Qatari patients with severe AD using the new ADCT evaluation tool. Methods: 30 patients completed a baseline survey before starting Dupilumab, and ADCT was assessed at four weeks post-therapy initiation. ADCT evaluates six AD symptoms in a severity grading from 0 to 3 (max. 24 points). The impact is assessed over the past week, including overall severity of symptoms, days with intense episodes of itching, the intensity of bother, problems with sleep, impact on daily activities, and impact on mood or emotions. In addition, itch severity was also assessed using a numeric rating scale (NRS11) ranging from 0 to 10. Results: The overall mean ADCT score at baseline was 17.6, and at week 4, it was reduced to 4.1. Patients reported a dramatic change in the overall symptoms already in this early phase. The parried t-test showed a significant difference in ADCT Score before and after therapy. There was a substantial decline in experiencing the associated AD symptoms: overall severity of symptoms (mean baseline =3.1, Dupilumab week 4 =0.9 (3.1/0.9), days with intense episodes of itching (3.2/0.7), the intensity of bother (3.2/0.8), the problem with sleep (2.7/0.4), impact on daily activities (2.5/0.6), and impact on mood or emotions (2.9/0.6). The itch score also reduced from 8/10 at baseline to 0-3 at week 4. Conclusion: Treatment of adult Asian/Arabic patients with severe AD treated with Dupilumab with or without topical steroids was highly effective and significantly improved overall well-being and pruritus as early as after 4 weeks of treatment.

Epidemiology of Geriatric-Dermatology virtual clinic: Teledermatology-Based care for elderly patients with skin diseases in Qatar.

Background: The 'GeriDerm' (geriatric dermatology) clinic, is a new dermatology-based service at Hamad Medical Corporation (HMC), accommodating the needs of our elderly population living in the State of Qatar. Due to the global demographic transition towards an elderly population (≥65 years of age), incidences of chronic diseases, including dermatologic conditions, rise in parallel. Patients of older age are at higher risk of using multiple medications, seeing multiple care providers, often receiving multiple diverging pieces of information, and feeling lost within the system. Taking into consideration the elderly unique characteristics, the Geriatric Dermatology telemedicine clinic is a novel approach to meeting the many challenges our elderly patients face via providing quick, accurate assessments of cognition, functional status, frailty screening, and assessment for polypharmacy. Methods: Data of 1080 elderly patients with various skin disorders from June 2020 to July 2021 was received from the Dermatology Geriatric clinic, and then reviewed. Results: There were 521(48.2%) new cases and 559(51.8%) follow-up cases who attended the clinic either virtually or face to face consultation. A total of 587(54.4%) female and 493(45.6%) male elderly patients attended the clinic. The mean age was 74.6, with a minimum age of 60 and a maximum age of 106 years. 57.9%(625) of GeriDerm patients were Qatari, followed by Palestinian 75(6.9%), Syrian 51(4.7%), Egyptian 46(4.3%), and Indian 44(4.1%); while other nationalities constituted 239(22.1%). The majority of the cases were Contact Dermatitis 146(13%), Bullous Pemphigoid 107 (10%), and Pruritis 101(9.4%). Conclusion: The 'GeriDerm' service at HMC aimed to achieve the best healthcare standards for the elderly population of Qatar during COVID-19 pandemic, and is now established as a continuous advanced technology-based framework facilitating caring for older patients with skin disease via providing a clear pathway for adequate triaging, identification of severe conditions (red flag) requiring in-person clinic visits, while managing non-life threatening dermatoses via a teledermatology based approach.

Interleukin-31: The "itchy" cytokine in inflammation and therapy.

The cytokine interleukin-31 has been implicated in the pathophysiology of multiple atopic disorders such as atopic dermatitis (AD), allergic rhinitis, and airway hyper-reactivity. In AD, IL-31 has been identified as one of the main "drivers" of its cardinal symptom, pruritus. Here, we summarize the mechanisms by which IL-31 modulates inflammatory and allergic diseases. TH 2 cells play a central role in AD and release high levels of TH 2-associated cytokines including IL-31, thereby mediating inflammatory responses, initiating immunoregulatory circuits, stimulating itch, and neuronal outgrowth through activation of the heterodimeric receptor IL-31 receptor A (IL31RA)/Oncostatin M receptor (OSMRß). IL31RA expression is found on human and murine dorsal root ganglia neurons, epithelial cells including keratinocytes and various innate immune cells. IL-31 is a critical cytokine involved in neuroimmune communication, which opens new avenues for cytokine modulation in neuroinflammatory diseases including AD/pruritus, as validated by recent clinical trials using an anti-IL-31 antibody. Accordingly, inhibition of IL-31-downstream signaling may be a beneficial approach for various inflammatory diseases including prurigo. However, as to whether downstream JAK inhibitors directly block IL-31-mediated-signaling needs to be clarified. Targeting the IL-31/IL31RA/OSMRß axis appears to be a promising approach for inflammatory, neuroinflammatory, and pruritic disorders in the future.

Exosomes: Emerging Diagnostic and Therapeutic Targets in Cutaneous Diseases.

Skin is the largest human organ and is continuously exposed to various exogenous and endogenous trigger factors affecting body homeostasis. A number of mechanisms, including genetic, inflammatory and autoimmune ones, have been implicated in the pathogenesis of cutaneous diseases. Recently, there has been considerable interest in the role that extracellular vesicles, particularly exosomes, play in human diseases, through their modulation of multiple signaling pathways. Exosomes are nano-sized vesicles secreted by all cell types. They function as cargo carriers shuttling proteins, nucleic acids, lipids etc., thus impacting the cell-cell communications and transfer of vital information/moieties critical for skin homeostasis and disease pathogenesis. This review summarizes the available knowledge on how exosomes affect pathogenesis of cutaneous diseases, and highlights their potential as future targets for the therapy of various skin diseases.

New mechanism underlying IL-31-induced atopic dermatitis.

BACKGROUND: TH2 cell-released IL-31 is a critical mediator in patients with atopic dermatitis (AD), a prevalent and debilitating chronic skin disorder. Brain-derived natriuretic peptide (BNP) has been described as a central itch mediator. The importance of BNP in peripheral (skin-derived) itch and its functional link to IL-31 within the neuroimmune axis of the skin is unknown. OBJECTIVE: We sought to investigate the function of BNP in the peripheral sensory system and skin in IL-31-induced itch and neuroepidermal communication in patients with AD. METHODS: Ca2+ imaging, immunohistochemistry, quantitative real-time PCR, RNA sequencing, knockdown, cytokine/phosphokinase arrays, enzyme immune assay, and pharmacologic inhibition were performed to examine the cellular basis of the IL-31-stimulated, BNP-related itch signaling in dorsal root ganglionic neurons (DRGs) and skin cells, transgenic AD-like mouse models, and human skin of patients with AD and healthy subjects. RESULTS: In human DRGs we confirmed expression and co-occurrence of oncostatin M receptor ß subunit and IL-31 receptor A in a small subset of the neuronal population. Furthermore, IL-31 activated approximately 50% of endothelin-1-responsive neurons, and half of the latter also responded to histamine. In murine DRGs IL-31 upregulated Nppb and induced soluble N-ethylmaleimide-sensitive factor activating protein receptor-dependent BNP release. In Grhl3PAR2/+ mice house dust mite-induced severe AD-like dermatitis was associated with Nppb upregulation. Lesional IL-31 transgenic mice also exhibited increased Nppb transcripts in DRGs and the skin; accordingly, skin BNP receptor levels were increased. Importantly, expression of BNP and its receptor were increased in the skin of patients with AD. In human skin cells BNP stimulated a proinflammatory and itch-promoting phenotype. CONCLUSION: For the first time, our findings show that BNP is implicated in AD and that IL-31 regulates BNP in both DRGs and the skin. IL-31 enhances BNP release and synthesis and orchestrates cytokine and chemokine release from skin cells, thereby coordinating the signaling pathways involved in itch. Inhibiting peripheral BNP function might be a novel therapeutic strategy for AD and pruritic conditions.

A sensory neuron-expressed IL-31 receptor mediates T helper cell-dependent itch: Involvement of TRPV1 and TRPA1.

BACKGROUND: Although the cytokine IL-31 has been implicated in inflammatory and lymphoma-associated itch, the cellular basis for its pruritic action is yet unclear. OBJECTIVE: We sought to determine whether immune cell-derived IL-31 directly stimulates sensory neurons and to identify the molecular basis of IL-31-induced itch. METHODS: We used immunohistochemistry and quantitative real-time PCR to determine IL-31 expression levels in mice and human subjects. Immunohistochemistry, immunofluorescence, quantitative real-time PCR, in vivo pharmacology, Western blotting, single-cell calcium imaging, and electrophysiology were used to examine the distribution, functionality, and cellular basis of the neuronal IL-31 receptor α in mice and human subjects. RESULTS: Among all immune and resident skin cells examined, IL-31 was predominantly produced by TH2 and, to a significantly lesser extent, mature dendritic cells. Cutaneous and intrathecal injections of IL-31 evoked intense itch, and its concentrations increased significantly in murine atopy-like dermatitis skin. Both human and mouse dorsal root ganglia neurons express IL-31RA, largely in neurons that coexpress transient receptor potential cation channel vanilloid subtype 1 (TRPV1). IL-31-induced itch was significantly reduced in TRPV1-deficient and transient receptor channel potential cation channel ankyrin subtype 1 (TRPA1)-deficient mice but not in c-kit or proteinase-activated receptor 2 mice. In cultured primary sensory neurons IL-31 triggered Ca(2+) release and extracellular signal-regulated kinase 1/2 phosphorylation, inhibition of which blocked IL-31 signaling in vitro and reduced IL-31-induced scratching in vivo. CONCLUSION: IL-31RA is a functional receptor expressed by a small subpopulation of IL-31RA(+)/TRPV1(+)/TRPA1(+) neurons and is a critical neuroimmune link between TH2 cells and sensory nerves for the generation of T cell-mediated itch. Thus targeting neuronal IL-31RA might be effective in the management of TH2-mediated itch, including atopic dermatitis and cutaneous T-cell lymphoma.

Metabolomics analyses reveal the crucial role of ERK in regulating metabolic pathways associated with the proliferation of human cutaneous T-cell lymphoma cells treated with Glabridin.

Cutaneous T-cell lymphomas (CTC) are a heterogeneous group of T-cell lymphoproliferative malignancies of the skin with limited treatment options, increased resistance and remission. Metabolic reprogramming is vital in orchestrating the uncontrolled growth and proliferation of cancer cells. Importantly, deregulated signalling plays a significant role in metabolic reprogramming. Considering the crucial role of metabolic reprogramming in cancer-cell growth and proliferation, target identification and the development of novel and multi-targeting agents are imperative. The present study explores the underlying mechanisms and metabolic signalling pathways associated with Glabridin mediated anti-cancer actions in CTCL. Our results show that Glabridin significantly inhibits the growth of CTCL cells through induction of programmed cell death (PCD) such as apoptosis, autophagy and necrosis. Interestingly, results further show that Glabridin induces PCD in CTCL cells by targeting MAPK signalling pathways, particularly the activation of ERK. Further, Glabridin also sensitized CTCL cells to the anti-cancer drug, bortezomib. Importantly, LC-MS-based metabolomics analyses further showed that Glabridin targeted multiple metabolites and metabolic pathways intricately involved in cancer cell growth and proliferation in an ERK-dependent fashion. Overall, our findings revealed that Glabridin induces PCD and attenuates the expression of regulatory proteins and metabolites involved in orchestrating the uncontrolled proliferation of CTCL cells through ERK activation. Therefore, Glabridin possesses important features of an ideal anti-cancer agent.

Sanguinarine Triggers Apoptosis in Cutaneous Squamous Cell Carcinoma Cells through Reactive Oxygen Species-Dependent c-Jun N-Terminal Kinase Signaling Pathway.

BACKGROUND: The benzophenanthridine Sanguinarine (Sng) is one of the most abundant root alkaloids with a long history of investigation and pharmaceutical applications. The cytotoxicity of Sng against various tumor cells is well-established; however, its antiproliferative and apoptotic potential against the cutaneous squamous cell carcinoma (cSCC) cells remains unknown. In the present study, we investigated the anti-cancer potential of Sng against cSCC cells and elucidated the underlying mechanisms relevant to the drug action. METHODS: The inhibitory effect of Sng on cSCC cells was evaluated by analyzing cell viability, colony-forming ability and multi-caspase activity. Apoptosis was quantified through Annexin-V/Propidium iodide flow cytometric assay and antagonized by pan-caspase inhibitor z-VAD-FMK. Mitochondrial membrane potential (ΔΨm) dysfunction was analyzed by JC-1 staining, whereas reactive oxygen species (ROS) generation was confirmed by pretreatment with N-acetylcysteine (NAC) and fluorogenic probe-based flow cytometric detection. The expression of cell cycle regulatory proteins, apoptotic proteins and MAPK signaling molecules was determined by Western blotting. Involvement of JNK, p38-MAPK and MEK/ERK in ROS-mediated apoptosis was investigated by pretreatment with SP600125 (JNK inhibitor), SB203580 (p38 inhibitor) and U0126 (ERK1/2 inhibitor), respectively. The stemness-targeting potential of Sng was assessed in tumor cell-derived spheroids. RESULTS: Treatment with Sng decreased cell viability and colony formation in primary (A431) and metastatic (A388) cSCC cells in a time- and dose-dependent manner. Sng significantly inhibited cell proliferation by inducing sub-G0/G1 cell-cycle arrest and apoptosis in cSCC cells. Sng evoked ROS generation, intracellular glutathione (GSH) depletion, ΔΨm depolarization and the activation of JNK pathway as well as that of caspase-3, -8, -9, and PARP. Antioxidant NAC inhibited ROS production, replenished GSH levels, and abolished apoptosis induced by Sng by downregulating JNK. Pretreatment with z-VAD-FMK inhibited Sng-mediated apoptosis. The pharmacological inhibition of JNK by SP600125 mitigated Sng-induced apoptosis in metastatic cSCC cells. Finally, Sng ablated the stemness of metastatic cSCC cell-derived spheroids. CONCLUSION: Our results indicate that Sng exerts a potent cytotoxic effect against cSCC cells that is underscored by a mechanism involving multiple levels of cooperation, including cell-cycle sub-G0/G1 arrest and apoptosis induction through ROS-dependent activation of the JNK signaling pathway. This study provides insight into the potential therapeutic application of Sng targeting cSCC.

Neuronal BST2: A Pruritic Mediator alongside Protease-Activated Receptor 2 in the IL-27-Driven Itch Pathway.

Chronic itch is a common and complex symptom often associated with skin diseases such as atopic dermatitis (AD). Although IL-27 is linked to AD, its role and clinical significance in itch remain undefined. We sought to investigate IL-27 function in itch using tissue-specific transgenic mice, various itch models, behavior scoring, RNA sequencing, and cytokine/kinase array. Our findings show that IL-27 receptors were overexpressed in human AD skin. Intradermal IL-27 injection failed to directly induce itch in mice but upregulated skin protease-activated receptor 2 (PAR2) transcripts, a key factor in itch and AD. IL-27 activated human keratinocytes, increasing PAR2 transcription and activity. Coinjection of SLIGRL (PAR2 agonist) and IL-27 in mice heightened PAR2-mediated itch. In addition, IL-27 boosted BST2 transcription in sensory neurons and keratinocytes. BST2 was upregulated in AD skin, and its injection in mice induced itch-like response. BST2 colocalized with sensory nerve branches in AD skin from both human and murine models. Sensory neurons released BST2, and mice with sensory neuron-specific BST2 knockout displayed reduced itch responses. Overall, this study provides evidence that skin IL-27/PAR2 and neuronal IL-27/BST2 axes are implicated in cutaneous inflammation and pruritus. The discovery of neuronal BST2 in pruritus shed light on BST2 in the itch cascade.

Targeting of S-phase kinase associated protein 2 stabilized tumor suppressors leading to apoptotic cell death in squamous skin cancer cells.

S-phase kinase-associated protein 2 (Skp2) is an F-box protein overexpressed in human cancers and linked with poor prognosis. It triggers cancer pathogenesis, including stemness and drug resistance. In this study, we have explored the potential role of Skp2 targeting in restoring the expression of tumor suppressors in human cutaneous squamous cell carcinoma (cSCC) cells. Our results showed that genetic and pharmacological Skp2 targeting markedly suppressed cSCC cell proliferation, colony growth, spheroid formation, and enhanced sensitization to chemotherapeutic drugs. Further, western blot results demonstrated restoration of tumor suppressor (KLF4) and CDKI (p21) and suppression of vimentin and survivin in Skp2-knocked-down cSCC cells. Importantly, we also explored that Skp2 targeting potentiates apoptosis of cSCC cells through MAPK signaling. Moreover, co-targeting of Skp2 and PI3K/AKT resulted in increased cancer cell death. Interestingly, curcumin, a well-known naturally derived anticancer agent, also inhibits Skp2 expression with concomitant CDKI upregulation. In line, curcumin suppressed cSCC cell growth through ROS-mediated apoptosis, while the use of N-acetyl cysteine (NAC) reversed curcumin-induced cell death. Curcumin treatment also sensitized cSCC cells to conventional anticancer drugs, such as cisplatin and doxorubicin. Altogether, these data suggest that Skp2 targeting restores the functioning of tumor suppressors, inhibits the expression of genes associated with cell proliferation and stemness, and sensitizes cancer cells to anticancer drugs. Thus, genetic, and pharmacological ablation of Skp2 can be an important strategy for attenuating cancer pathogenesis and associated complications in skin squamous cell carcinoma.

Bortezomib exerts its anti-cancer activity through the regulation of Skp2/p53 axis in non-melanoma skin cancer cells and C. elegans.

Non-melanoma skin cancer (NMSC), encompassing basal and squamous cell carcinoma, is the most prevalent cancer in the United States. While surgical removal remains the conventional therapy with a 95% 5-year cure rate, there is a growing interest in exploring alternative treatment strategies. In this study, we investigated the role of Bortezomib (BTZ), a proteasome inhibitor, in NMSC. Using two NMSC cell lines (A431 and A388), we examined the effects of BTZ treatment. Our results demonstrated that 48 h of BTZ treatment led to downregulating Skp2 expression in both A431 and A388 cells while upregulating p53 expression, specifically in A388 cells. These alterations resulted in impaired cellular growth and caspase-dependent cell death. Silencing Skp2 in A388 cells with siRNA confirmed the upregulation of p53 as a direct target. Furthermore, BTZ treatment increased the Bax to Bcl-2 ratio, promoting mitochondrial permeability and the subsequent release of cytochrome C, thereby activating caspases. We also found that BTZ exerted its antitumor effects by generating reactive oxygen species (ROS), as blocking ROS production significantly reduced BTZ-induced apoptotic cell death. Interestingly, BTZ treatment induced autophagy, which is evident from the increased expression of microtubule-associated proteins nucleoporin p62 and LC-3A/B. In addition to cell lines, we assessed the impact of BTZ in an in vivo setting using Caenorhabditis elegans (C. elegans). Our findings demonstrated that BTZ induced germline apoptosis in worms even at low concentrations. Notably, this increased apoptosis was mediated through the activity of CEP-1, the worm's counterpart to mammalian p53. In summary, our study elucidated the molecular mechanism underlying BTZ-induced apoptosis in NMSC cell lines and C. elegans. By targeting the skp2/p53 axis, inducing mitochondrial permeability, generating ROS, and promoting autophagy, BTZ demonstrates promising anti-cancer activity in NMSC. These findings provide novel insights into potential therapeutic strategies for controlling the unregulated growth of NMSC.