Novel Therapeutic Targets in Cutaneous Squamous Cell Carcinoma

Update on the Molecular Pathology of Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer, originating from keratinocytes of the spinous layer. Numerous risk factors have been discovered for the initiation and growth of this type of cancer, such as exposure to UV and ionizing radiation, chemical carcinogens, the presence of immunosuppression states, chronic inflammation, infections with high-risk viral strains, and, last but not least, the presence of diseases associated with genetic alterations. The important socio-economic impact, as well as the difficulty associated with therapy for advanced forms, has made the molecular mechanisms underlying this neoplasia more and more intensively studied, with the intention of achieving a better understanding and advancing the treatment of this pathology. This review aims to provide a brief foray into the molecular, genetic, and epigenetic aspects of this cancer, as well as the treatment methods, ranging from the first used to the latest targeted therapies.

Circ_0001821 contributes to the development of cutaneous squamous cell carcinoma by regulating miR-148a-3p/EGFR axis and activating PI3K/Akt pathway

Background: Circular RNAs (circRNAs) are implicated in diverse human cancers. However, the effects of circRNAs on cutaneous squamous cell carcinoma (CSCC) are barely known. we focused on the function of circ_0001821 in CSCC. Methods: QRT-PCR assay was performed for the expression of circ_0001821, miR-148a-3p and epidermal growth factor receptor (EGFR). Cell Counting Kit-8 (CCK-8) assay and colony formation assay were conducted to evaluate cell viability and colony formation ability. Flow cytometry analysis was adopted to analyze cell cycle and apoptosis. Transwell assay was employed to detect cell motility. Dual-luciferase reporter assay, RIP assay and RNA pull-down assay were utilized to verify the interaction between miR-148a-3p and circ_0001821 or EGFR. Western blot assay was conducted for protein levels. Murine xenograft model assay was used to explore the function of circ_0001821 in vivo. Results: Circ_0001821 level was increased in CSCC tissues and cells. Circ_0001821 knockdown restrained cell viability, colony formation, cell cycle process and metastasis and facilitated cell apoptosis in vitro and restrained tumor growth in vivo. For mechanism analysis, circ_0001821 directly targeted miR-148a-3p to elevate EGFR expression. Downregulation of miR-148a-3p weakened the impacts of circ_0001821 deficiency on CSCC malignant phenotypes. Moreover, miR-148a-3p overexpression inhibited the malignant phenotypes of CSCC cells, with EGFR elevation abrogated the effects. In addition, circ_0001821 knockdown blocked the activation of PI3K/Akt pathway. Conclusion: Circ_0001821 functioned as a tumor promotor in CSCC via regulating miR-148a-3p/EGFR axis and PI3K/Akt pathway.

Loss of FAM83H promotes cell migration and invasion in cutaneous squamous cell carcinoma via impaired keratin distribution

BACKGROUNDS

FAM83H is essential for amelogenesis, but recent reports implicate that FAM83H is involved in the tumorigenesis. We previously clarified that TRIM29 binds to FAM83H to regulate keratin distribution and squamous cell migration. However, little is known about FAM83H in normal/malignant skin keratinocytes.

OBJECTIVE

To investigate the expression of FAM83H in cutaneous squamous cell carcinoma (SCC) and its physiological function.

METHODS

Immunohistochemical analysis and RT-PCR of human SCC tissues were performed. Next, we examined the effect of FAM83H knockdown/overexpression in SCC cell lines using cell proliferation, migration, and invasion assay. To investigate the molecular mechanism, immunoprecipitation of FAM83H was examined. Further, Immunofluorescence staining was performed. Finally, we examined the correlation between the expressions of FAM83H and the keratin distribution.

RESULTS

FAM83H expression was lower in SCC lesions than in normal epidermis and correlated with differentiation grade. The mRNA expression levels of FAM83H in SCC tumors were also lower than in normal epidermis. The knockdown of FAM83H enhanced SCC cell migration and invasion, whereas the overexpression of FAM83H led to decreases in both. Furthermore, the knockdown of FAM83H enhanced the cancer cell metastasis in vivo. FAM83H formed a complex with TRIM29 and keratins. The knockdown of FAM83H altered keratin distribution and solubility. Clinically, the loss of FAM83H correlates with an altered keratin distribution.

CONCLUSION

Our findings reveal a critical function for FAM83H in regulating keratin distribution, as well as in the migration/invasion of cutaneous SCC, suggesting that FAM83H could be a crucial molecule in the tumorigenesis of cutaneous SCC.

Extra-anogenital giant cutaneous squamous cell carcinomas require multidisciplinary management

Cutaneous squamous cell carcinoma (cSCC) is a highly prevalent cancer and the majority of cSCC have a good prognosis. However, a subset of cSCC can progress to advanced disease. We present the first reported case of a giant cSCC located on the breast. In addition, a systematic literature search on extra-anogenital giant (EAG) cSCC was performed using Pubmed and MEDLINE databases. Thirty-one articles could be retained which were relevant for this review. A total of 42 well-described cases were identified. Median age at presentation was 70 years (range 9-100 years). Twenty-four (57%) patients were male, eighteen were female (43%). The estimated median delay of treatment was 12 months (range 1 to >240 months). In 27 patients (64%) the giant cSCC was localized on the neck, face or scalp, 6 on the thoracic wall or back (14%), 4 on the lower limb (10%), 2 on the hip or buttock (5%), 2 on the upper limb (5%), one (2%) on the breast. Tumor stage at presentation was T2, T3 and T4 in respectively 26 (62%), 11 (26%) and 5 (12%) cases. Lymph node metastases were identified in 1 patient (2%) and distant metastases in another patient (2%). In 34 out of 42 cases (81%) primary radical surgical excision was performed, 3 received radiotherapy, 2 chemotherapy and 3 palliative care. In the cases with reported follow-up, four patients (4/30: 13%) died of disease. The treatment of EAG cSCC poses many problems, making a multidisciplinary approach of paramount importance.

Differences in the mitochondrial microsatellite instability of Keratoacanthoma and cutaneous squamous cell carcinoma

Keratoacanthoma (KA) is a common cutaneous neoplasm which often resembles typical squamous cell carcinoma (SCC) in both its clinical and historical presentation. Several studies have attempted to identify methods for distinguishing between KA and SCC, however, none of these have proven to play any obvious roles in these tumors. Given this we went on to evaluate mitochondrial microsatellite instability (mtMSI) in KA and SCC in an effort to understand these tumors better. DNA was isolated from paired normal and tumoral tissues donated by 57 KA patients and 43 SCC patients. MtMSI was then analyzed using eight microsatellite markers and was observed in 2 (3.5%) of the 57 KA patients and 8 (18.6%) of the 43 SCC patients, respectively. MtMSI was also shown to affect different locations depending on tumor type. In KA patients, mtMSI was detected at mitochondrial D514 D-loop and presented with (CA) n repeats, in contrast, all of the SCC patient experienced mtMSI at the D310 with (C)n repeats of the D-loop region. These differences in location were found to be significant, which may support the hypothesis that KA and SCC have different pathogenetic pathways. Our results also suggest that mtMSI may be a candidate for developing novel differential diagnostic methods for KA and SCC.

NIX initiates mitochondrial fragmentation via DRP1 to drive epidermal differentiation

The epidermis regenerates continually to maintain a protective barrier at the body’s surface composed of differentiating keratinocytes. Maturation of this stratified tissue requires that keratinocytes undergo wholesale organelle degradation upon reaching the outermost tissue layers to form compacted, anucleate cells. Through live imaging of organotypic cultures of human epidermis, we find that regulated breakdown of mitochondria is critical for epidermal development. Keratinocytes in the upper layers initiate mitochondrial fragmentation, depolarization, and acidification upon upregulating the mitochondrion-tethered autophagy receptor NIX. Depleting NIX compromises epidermal maturation and impairs mitochondrial elimination, whereas ectopic NIX expression accelerates keratinocyte differentiation and induces premature mitochondrial fragmentation via the guanosine triphosphatase (GTPase) DRP1. We further demonstrate that inhibiting DRP1 blocks NIX-mediated mitochondrial breakdown and disrupts epidermal development. Our findings establish mitochondrial degradation as a key step in terminal keratinocyte differentiation and define a pathway operating via the mitophagy receptor NIX in concert with DRP1 to drive epidermal morphogenesis.

Using live microscopy of human organotypic epidermis, Simpson et al. demonstrate how keratinocytes degrade their mitochondria in the upper tissue layers during their final stage of differentiation. By upregulating expression of the mitophagy receptor NIX, keratinocytes initiate DRP1- dependent mitochondrial fragmentation, a process critical for epidermal tissue maturation.

Thulium oxide nanoparticles as radioenhancers for the treatment of metastatic cutaneous squamous cell carcinoma

Metastases from cutaneous squamous cell carcinoma (cSCC) occur in 2%-5% of cases. Surgery is the standard treatment, often combined with adjuvant radiotherapy. Concurrent carboplatin treatment with post-operative radiotherapy may be prescribed, although it has not shown benefit in recent clinical trials in high-risk cSCC patients. The novel high-Z nanoparticle thulium (III) oxide has been shown to enhance radiation dose delivery to brain tumors by specific uptake of these nanoparticles into the cancerous tissue. As the dose-enhancement capacity of thulium oxide nanoparticles following radiotherapy against metastatic cSCC cells is unknown, its efficacy as a radiosensitizer was evaluated, with and without carboplatin. Novel and validated human patient-derived cell lines of metastatic cSCC were used. The sensitivity of the cells to radiation was investigated using short-term proliferation assays as well as clonogenic survival as the radiobiological endpoint. Briefly, cells were irradiated with 125 kVp orthovoltage x-rays (0-6 Gy) with and without thulium oxide nanoparticles (99.9% trace metals basis; 50 µg ml^-1) or low dose carboplatin pre-sensitization. Cellular uptake of the nanoparticles was first confirmed by microscopy and found to have no impact on short-term cell survival for the cSCC cells, highlighting the biocompatibility of thulium oxide nanoparticles. Clonogenic cell survival assays confirmed radio-sensitization when exposed to thulium nanoparticles, with the cell sensitivity increasing by a factor of 1.24 (calculated at the 10% survival fraction) for the irradiated cSCC cells. The combination of carboplatin with thulium oxide nanoparticles with irradiation did not result in significant further reductions in survival compared to nanoparticles alone. This is the first study to provide in vitro data demonstrating the independent radiosensitization effect of high-Z nanoparticles against metastatic cSCC with or without carboplatin. Further preclinical investigations with radiotherapy plus high-Z nanoparticles for the management of metastatic cSCC are warranted.

Molecular prediction of metastasis in cutaneous squamous cell carcinoma

PURPOSE OF REVIEW

Cutaneous squamous cell carcinoma (cSCC) is a highly prevalent malignancy frequently occurring on body surfaces chronically exposed to ultraviolet radiation. While a large majority of tumors remain localized to the skin and immediate subcutaneous tissue and are cured with surgical excision, a small subset of patients with cSCC will develop metastatic disease. Risk stratification for cSCC is performed using clinical staging systems, but given a high mutational burden and advances in targeted and immunotherapy, there is growing interest in molecular predictors of high-risk disease.

RECENT FINDINGS

Recent literature on the risk for metastasis in cSCC includes notable findings in genes involved in cell-cycle regulation, tumor suppression, tissue invasion and microenvironment, interactions with the host-immune system, and epigenetic regulation.

SUMMARY

cSCC is a highly mutated tumor with complex carcinogenesis. Regulators of tumor growth and local invasion are numerous and increasingly well-understood but drivers of metastasis are less established. Areas of importance include central system regulators (NOTCH, miRNAs), proteins involved in tissue invasion (podoplanin, E-cadherin), and targets of existing and emerging therapeutics (PD-1, epidermal growth factor receptor). Given the complexity of cSCC carcinogenesis, the use of machine learning algorithms and computational genomics may provide ultimate insight and prospective studies are needed to verify clinical relevance.

Widespread Hypertrophic Lichen Planus following Programmed Cell Death Ligand 1 Blockade

Hypertrophic lichen planus (HLP) may not have the typical histological findings of lichen planus and often mimics squamous cell carcinoma (SCC). Distinguishing between the two can pose a diagnostic challenge. Here, we present a case of eruptive HLP mimicking SCC in the context of programmed cell death ligand 1 (PD-L1) immune checkpoint inhibition. A 73-year-old woman recently treated with durvalumab, an anti-PD-L1 antibody, presented to our clinic with diffuse hyperkeratotic papules and plaques previously thought to be eruptive SCC. The lesions did not respond to topical fluorouracil and continued to appear despite discontinuation of immunotherapy. Further histological analysis revealed intraepidermal epithelial proliferation with lichenoid inflammation. Subsequent treatment with topical corticosteroids significantly improved the size and number of lesions. The diagnosis of HLP was made based on histological features and response to topical steroids in the context of recent immunotherapy. This case reveals HLP as a potential adverse effect of PD-L1 inhibition and highlights the need for additional diagnostic assessment in patients presenting with eruptive hyperkeratotic lesions, especially on the lower extremities.

Deciphering the Molecular Landscape of Cutaneous Squamous Cell Carcinoma for Better Diagnosis and Treatment

Cutaneous squamous cell carcinoma (cSCC) is a common type of neoplasia, representing a terrible burden on patients' life and clinical management. Although it seldom metastasizes, and most cases can be effectively treated with surgical intervention, once metastatic cSCC displays considerable aggressiveness leading to the death of affected individuals. No consensus has been reached as to which features better characterize the aggressive behavior of cSCC, an achievement hindered by the high mutational burden caused by chronic ultraviolet light exposure. Even though some subtypes have been recognized as high risk variants, depending on certain tumor features, cSCC that are normally thought of as low risk could pose an increased danger to the patients. In light of this, specific genetic and epigenetic markers for cutaneous SCC, which could serve as reliable diagnostic markers and possible targets for novel treatment development, have been searched for. This review aims to give an overview of the mutational landscape of cSCC, pointing out established biomarkers, as well as novel candidates, and future possible molecular therapies for cSCC.

Loss of dynamin-related protein 1 (Drp1) does not affect epidermal development or UVB-induced apoptosis but does accelerate UVB-induced carcinogenesis

BACKGROUND

Mitochondrial morphology is controlled by fission and fusion. Dynamin-related protein 1 (Drp1, dynamin-1-like protein (Dnml1)) regulates mitochondrial fission, which is associated with cell division and apoptosis. We previously reported that DRP1 is indispensable for cell growth in cutaneous squamous cell carcinoma. However, little is known about Drp1 in normal epidermis/keratinocytes.

OBJECTIVES

We investigated the function of Drp1 in normal epidermis/keratinocytes.

METHODS

Epidermis-specific Drp1 knockout (EKO) mice were analyzed.

RESULTS

Epidermal development in the EKO mice were indistinguishable from those in the wild-type (WT) mice. Ultrastructural analysis and immunohistochemistry revealed that the mitochondria of keratinocytes in the EKO mice were neither elongated nor constricted. Drp1 knockdown did not diminish the cell growth of normal human keratinocytes. Both in vivo and in vitro, UVB-induced apoptosis in the EKO epidermis and keratinocytes did not differ from that in the WT mice. In chronic UVB-irradiation, the loss of Drp1 sensitized the epidermis to the development of skin tumors. Clinically, DRP1 is expressed more highly in sun-exposed skin than in non-exposed skin in individuals under age 40, but not in those over age 60.

CONCLUSION

EKO mice demonstrate that Drp1 is dispensable for the development and apoptosis of the epidermis. Drp1 plays critical roles in malignant tumors; thus, the molecular machinery of mitochondrial dynamics involving Drp1 could be a novel therapeutic target for malignant keratinocytic lesions. On the other hand, the anti-tumorigenic role of Drp1 in chronic UVB-induced carcinogenesis need to be further investigated.

Nomogram for Preoperative Estimation of Orbit Invasion Risk in Periocular Squamous Cell Carcinoma

Importance: Orbital invasion occurs in some periocular squamous cell carcinoma (SCC), compromising surgical outcomes, and prognoses of patients. To date, however, there are no validation studies on the clinical features related to orbital invasion in patients with periocular SCC.

Objective: To explore clinical features that may be associated with orbital invasion and build a model for predicting the risk of orbital invasion.

Design, Setting, and Participants: In this retrospective mono-center case-control study, 90 patients with periocular SCC were treated at the Ninth People's Hospital Shanghai Jiao Tong University School of Medicine from January 2005 to August 2019. “Case” is defined as a SCC patient with orbit invasion prior to operation. “Exposure” is defined as the different sites of lesion.

Main Outcomes and Measures: Clinical features, including “time to relapse after surgery,” were collected. Multivariate logistic regression analysis was applied to identify the independent risk clinical features associated with orbital invasion, which was then incorporated into a nomogram.

Results: Of the 90 patients included in this study, 33 patients (36.7%) had orbital invasion. 14 of the 33 orbit-invasive patients had local recurrence, while 11 of 57 orbit non-invasive patients had local recurrence, suggesting that orbital invasion is a risk factor for local recurrence. The multivariate binary logistic regression indicated that the lesions at the medial canthus [odds ratio (OR), 5.024, 95% CI, 1.409–17.912, P = 0.013], the age at diagnosis (10-years intervals; OR, 0.590, 95% CI, 0.412–0.844, P = 0.004), and bleeding in the lesion (OR, 3.480, 95% CI, 1.254–9.660, P = 0.017) were three preoperative clinical features significantly associated with orbital invasion.

Conclusion: For periocular SCC, lesions at the medial canthus, the younger age of the patients at diagnosis, and bleeding in the lesion were the three main clinical features associated with orbital invasion. The risk score model for orbital invasion can act as a supportive tool for optimized clinical evaluation and treatment decisions.

Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma represents 20% of all skin cancers, resulting in 1 million cases in the United States each year. The lifetime risk of developing squamous cell carcinoma continues to increase annually and will likely continue to increase because of the aging population. Most cutaneous squamous cell carcinoma are treated locally, with a subset leading to recurrence, metastasis, and death. This review of cutaneous squamous cell carcinoma covers incidence, recurrence rates, mortality rates, risk factors, staging systems, treatment, prevention, and monitoring.

High Hydrostatic Pressure Therapy Annihilates Squamous Cell Carcinoma in a Murine Model

Cutaneous squamous cell carcinoma (cSCC) is one of the most common skin cancers. In the treatment of cSCC, it is necessary to remove it completely, and reconstructive surgery, such as a skin graft or a local or free flap, will be required, depending on the size, with donor-site morbidity posing a burden to the patient. The high hydrostatic pressure (HHP) technique has been developed as a physical method of decellularizing various tissues. We previously reported that HHP at 200 MPa for 10 min could inactivate all cells in the giant congenital melanocytic nevus, and we have already started a clinical trial using this technique. In the present study, we explored the critical pressurization condition for annihilating cSCC cells in vitro and confirmed that this condition could also annihilate cSCC in vivo. We prepared 5 pressurization conditions in this study (150, 160, 170, 180, and 190 MPa for 10 min) and confirmed that cSCC cells were killed by pressurization at ≥160 MPa for 10 min. In the in vivo study, the cSCC cells inactivated by HHP at 200 MPa for 10 min were unable to proliferate after injection into the intradermal space of mice, and transplanted cSCC tissues that had been inactivated by HHP showed a decreased weight at 5 weeks after implantation. These results suggested that HHP at 200 MPa for 10 min was able to annihilate SCC, so HHP technology may be a novel treatment of skin cancer.

Unraveling the ECM-Immune Cell Crosstalk in Skin Diseases

The extracellular matrix (ECM) is a complex network of proteins and proteoglycans secreted by keratinocytes, fibroblasts and immune cells. The function of the skin ECM has expanded from being a scaffold that provides structural integrity, to a more dynamic entity that is constantly remodeled to maintain tissue homeostasis. The ECM functions as ligands for cell surface receptors such as integrins, dystroglycans, and toll-like receptors (TLRs) and regulate cellular signaling and immune cell dynamics. The ECM also acts as a sink for growth factors and cytokines, providing critical cues during epithelial morphogenesis. Dysregulation in the organization and deposition of ECMs lead to a plethora of pathophysiological conditions that are exacerbated by aberrant ECM-immune cell interactions. In this review, we focus on the interplay between ECM and immune cells in the context of skin diseases and also discuss state of the art therapies that target the key molecular players involved.

miRNA-221 promotes cutaneous squamous cell carcinoma progression by targeting PTEN

Background

Cutaneous squamous cell carcinoma (CSCC) is a common type of skin malignancy. MicroRNA-221 (miRNA-221) is a critical non-coding RNA in tumor initiation and progression. However, the molecular mechanisms of miRNA-221 in the development of CSCC remain unknown. This study investigated the expression of miRNA-221 in CSCC and its potential tumor biological functions.

Methods

MTT assay, colony assay, PCR, and Western blot were adopted.

Results

In this study, miRNA-221 expression was significantly higher in CSCC tissues and cell lines than in normal tissues and cells (P < 0.05). Further functional experiments indicated that miRNA-221 knockdown inhibited the proliferation and cell cycle, while upregulation of miRNA-221 presented the opposite role. The dual reporter gene assays indicated that PTEN is a direct target gene of miRNA-221. PTEN protein or mRNA levels were decreased after the cells were transfected with miR-221 mimics.

Conclusions

Taken together, the obtained results indicated that miR-221 plays an oncogenic function in CSCC by targeting PTEN and further suggest that miR-221 may be a potential target for CSCC diagnosis and treatment.

Loss of TRIM29 Alters Keratin Distribution to Promote Cell Invasion in Squamous Cell Carcinoma

: TRIM29 (tripartite motif-containing protein 29) is a TRIM family protein that has been implicated in breast, colorectal, and pancreatic cancers. However, its role in stratified squamous epithelial cells and tumors has not been elucidated. Here, we investigate the expression of TRIM29 in cutaneous head and neck squamous cell carcinomas (SCC) and its functions in the tumorigenesis of such cancers. TRIM29 expression was lower in malignant SCC lesions than in adjacent normal epithelial tissue or benign tumors. Lower expression of TRIM29 was associated with higher SCC invasiveness. Primary tumors of cutaneous SCC showed aberrant hypermethylation of TRIM29. Depletion of TRIM29 increased cancer cell migration and invasion; conversely, overexpression of TRIM29 suppressed these. Comprehensive proteomics and immunoprecipitation analyses identified keratins and keratin-interacting protein FAM83H as TRIM29 interactors. Knockdown of TRIM29 led to ectopic keratin localization of keratinocytes. In primary tumors, lower TRIM29 expression correlated with the altered expression of keratins. Our findings reveal an unexpected role for TRIM29 in regulating the distribution of keratins, as well as in the migration and invasion of SCC. They also suggest that the TRIM29-keratin axis could serve as a diagnostic and prognostic marker in stratified epithelial tumors and may provide a target for SCC therapeutics. SIGNIFICANCE: These findings identify TRIM29 as a novel diagnostic and prognostic marker in stratified epithelial tissues.