Ángeles Juarranz

Background/Objectives: Vitamin D (VD), through the interaction with its receptor (VDR), plays essential roles in the skin. VDR-mediated signaling prevents cancer development and improves prognosis, making it an appealing target for therapy. However, VD cutaneous synthesis begins with solar exposure, which is the first etiological factor for cutaneous cancer and increases oxidative stress (OS). This complicates the dermatologist’s perspective when advising photoprotective strategies while aiming to consider the benefits of VD signaling. In this context, and in the absence of cutaneous data to date, this research aims to address VDR dynamics in skin cells and tissue subjected to OS. It also explores the potential of a natural photoprotectant with antioxidant properties (a specific combination of Polypodium leucotomos and Aspalathus linearis extracts) in preventing VDR depletion. Methods: HaCaT cell cultures and skin explants were used as experimental models. OS was induced by treatments with hydrogen peroxide (H₂O₂). The proteins of interest (VDR and Nuclear Factor Erythroid 2-Related Factor 2 (NRF2)) were analyzed by immunostaining. Cell viability, nuclear counterstaining, and Haematoxylin/Eosin staining were used as cyto/histochemical controls. Results: In both experimental models, we observed the reduction of VDR under OS. Pre-treatments with the botanical ingredient preserved VDR levels from that decline, probably through a mechanism involving NRF2. Conclusions: Cutaneous VDR levels are altered under oxidative stress, and certain photoprotectants could preserve them. This opens the door to preserving the benefits of VDR signaling while preventing solar radiation damage, bringing a new viewpoint for designing future strategies in skin cancer prevention and treatment.

Cutaneous squamous cell carcinoma (cSCC) is a highly prevalent skin cancer. While surgery remains the gold standard treatment, non-invasive methods like photodynamic therapy (PDT) stand out for their high efficacy and minimal cosmetic impact. However, resistance to PDT is still a challenge. Numerous cellular processes involved in cancer biology and therapy resistance are regulated by the TGFβ1/SMAD pathway. Using in vitro bidimensional and tridimensional cultures of cSCC cell lines, we studied the development of resistance to PDT in response to TGFβ1 secreted by cancer associated fibroblasts. Our results highlight the TGFβ1 co-receptor endoglin as a key molecular player in the process. Importantly, targeting endoglin expression with N-acetylcysteine (NAC) or raloxifene significantly reduced TGFβ1 levels and effectively prevented resistance. In addition, the combination of PDT with NAC resulted in an improved therapeutic outcome in vivo in SKH-1 mice with cSCC photogenerated by chronic exposition to ultraviolet light. In conclusion, the combination of PDT with NAC or raloxifene enhances PDT efficacy by mitigating resistance mechanisms, which can open new avenues for the treatment of cSCC.

Cutaneous and Head and Neck squamous cell carcinoma (CSCC, HNSCC) are among the most prevalent cancers. Both types of cancer can be treated with photodynamic therapy (PDT) by using the photosensitizer Temoporfin in HNSCC and the prodrug methyl-aminolevulinate (MAL) in CSCC. However, PDT is not always effective. Therefore, it is mandatory to correctly approach the therapy according to the characteristics of the tumour cells. For this reason, we have used cell lines of CSCC (A431 and SCC13) and HNSCC (HN5 and SCC9). The results obtained indicated that the better response to MAL-PDT was related to its localization in the plasma membrane (A431 and HN5 cells). However, with Temoporfin all cell lines showed lysosome localization, even the most sensitive ones (HN5). The expression of mesenchymal markers and migratory capacity was greater in HNSCC lines compared to CSCC, but no correlation with PDT response was observed. The translocation to the nucleus of β-catenin and GSK3β and the activation of NF-κβ is related to the poor response to PDT in the HNSCC lines. Therefore, we propose that intracellular localization of GSK3β could be a good marker of response to PDT in HNSCC. Although the molecular mechanism of response to PDT needs further elucidation, this work shows that the most MAL-resistant line of CSCC is more sensitive to Temoporfin.

This comprehensive review delves into various immunotherapeutic approaches for the management of actinic keratoses (AKs), precancerous skin lesions associated with UV exposure. Although there are treatments whose main mechanism of action is immune modulation, such as imiquimod or diclofenac, other treatments, apart from their main effect on dysplastic cells, exert some immunological action, which in the end contributes to their efficacy. While treatments like 5-fluorouracil, imiquimod, photodynamic therapy, and nicotinamide are promising in the management of AKs, especially in immunocompetent individuals, their efficacy is somewhat reduced in solid organ transplant recipients due to immunosuppression. The analysis extends to optimal combination, focusing on cryoimmunotherapy as the most relevant. New immunotherapies include resimiquimod, ingenol disoxate, N-phosphonacetyl-L-aspartate (PALA), or anti-PD1 that have shown promising results, although more studies are needed in order to standardize their use.

Squamous Cell Carcinoma (SCC) is a subtype of Non-Melanoma Skin Cancer, the most common group of malignancies worldwide. Photodynamic therapy (PDT) is a non-invasive treatment approved for specific subtypes of SCC. Some malignancies resist PDT, forming more aggressive tumors and multiple relapses. Thus, new approaches aimed at optimizing the response to PDT are needed. The mTORC1 inhibitor rapamycin, also known as Sirolimus (SRL), interferes with protein synthesis and cell metabolism. The use of SRL as an immunosuppressant is associated to lower rates of SCC in kidney-transplanted patients, which are frequently affected by this pathology. We have evaluated SRL pre-treatment efficacy to enhance the damage induced by PDT with Methyl 5-aminolevulinate in two different cutaneous SCC established cell lines (SCC13 and A431) in vitro and therapy sensitization in PDT-resistant cell lines. We tested for the first time the SRL + PDT combination in a SKH-1 mouse model of photocarcinogenesis, diminishing the frequency of lesions and restraining tumor growth. Molecular studies revealed that protoporphyrin IX and reactive oxygen species production induced by PDT were promoted by SRL pre-treatment. Lastly, SRL modifies the expression and intracellular location of NRF2, interfering with the downstream antioxidant response modulated by NQO1 and HO-1. In conclusion, we propose SRL as a potential adjuvant to enhance PDT efficacy for SCC treatment.

Exposure to sun radiation leads to higher risk of sunburn, pigmentation, immunosuppression, photoaging and skin cancer. In addition to ultraviolet radiation (UVR), recent research indicates that infrared radiation (IR) and visible light (VIS) can play an important role in the pathogenesis of some of these processes. Detrimental effects associated with sun exposure are well known, but new studies have shown that DNA damage continues to occur long after exposure to solar radiation has ended. Regarding photoprotection strategies, natural substances are emerging for topical and oral photoprotection. In this sense, Fernblock^®, a standardized aqueous extract of the fern Polypodium Leucotomos (PLE), has been widely administered both topically and orally with a strong safety profile. Thus, this extract has been used extensively in clinical practice, including as a complement to photodynamic therapy (PDT) for treating actinic keratoses (AKs) and field cancerization. It has also been used to treat skin diseases such as photodermatoses, photoaggravated inflammatory conditions and pigmentary disorders. This review examines the most recent developments in the clinical application of Fernblock^® and assesses how newly investigated action mechanisms may influence its clinical use.

Exposure to sun radiation leads to higher risk of sunburn, pigmentation, immunosuppression, photoaging and skin cancer. In addition to ultraviolet radiation (UVR), recent research indicates that infrared radiation (IR) and visible light (VIS) can play an important role in the pathogenesis of some of these processes. Detrimental effects associated to sun exposure are well known, but new studies have shown that DNA damage continues to occur long after exposure to solar radiation has ended. Regarding photoprotection strategies, natural substances are emerging for topical and oral photoprotection. In this sense, Fernblock®, a standardized aqueous extract of the fern Polypodium Leucotomos (PLE), has been widely administered both topically and orally with a strong safety profile. Thus, this extract has been used extensively in clinical practice, including as a complement to photodynamic therapy (PDT) for treating actinic keratoses (AKs) and field cancerization. It has also been used to treat skin diseases such as photodermatoses, photoaggravated inflammatory conditions and pigmentary disorders. This review examines the most recent developments in the clinical application of Fernblock® and assesses how newly investigated action mechanisms may influence its clinical use.