Tumour-infiltrating Langerhans cells in non-melanoma skin cancer, a clinical and immunohistochemical study

The roles of tissue resident macrophages in health and cancer

As integral components of the immune microenvironment, tissue resident macrophages (TRMs) represent a self-renewing and long-lived cell population that plays crucial roles in maintaining homeostasis, promoting tissue remodeling after damage, defending against inflammation and even orchestrating cancer progression. However, the exact functions and roles of TRMs in cancer are not yet well understood. TRMs exhibit either pro-tumorigenic or anti-tumorigenic effects by engaging in phagocytosis and secreting diverse cytokines, chemokines, and growth factors to modulate the adaptive immune system. The life-span, turnover kinetics and monocyte replenishment of TRMs vary among different organs, adding to the complexity and controversial findings in TRMs studies. Considering the complexity of tissue associated macrophage origin, macrophages targeting strategy of each ontogeny should be carefully evaluated. Consequently, acquiring a comprehensive understanding of TRMs' origin, function, homeostasis, characteristics, and their roles in cancer for each specific organ holds significant research value. In this review, we aim to provide an outline of homeostasis and characteristics of resident macrophages in the lung, liver, brain, skin and intestinal, as well as their roles in modulating primary and metastatic cancer, which may inform and serve the future design of targeted therapies.

Basal Cell Carcinoma in Xeroderma Pigmentosa: Reduced CD1a Expression as a Sensitive Predictor of Recurrence

Xeroderma pigmentosa (XP) is a rare genetic disorder that is characterized by defective DNA repair after ultraviolet induced damage with a great tendency for recurrent cutaneous malignancies including basal cell carcinoma (BCC). BCC is frequently linked to impaired local immune response with a major role played by Langerhans cells (LCs). The current study aims at investigating LCs in BCC specimens of XP and non-XP patients, in a trial to study its possible impact on tumor recurrence. It included 48 retrospective cases of primary facial BCC (18 for XP patients and 30 for non-XP controls). Each group was subdivided, based on the 5 years follow-up data, into recurrent and non-recurrent BCC groups. LCs were assessed immunohistochemically using the sensitive marker; CD1a. Results showed significantly reduced LCs count (intratumoral, peritumoral, and in perilesional epidermis) in XP patients compared with non-XP controls ( P ˂0.001 for all). Intratumoral ( P =0.008), peritumoral ( P =0.005), and perilesional epidermal ( P =0.02) LCs mean values were significantly lower in recurrent versus non-recurrent BCC specimens. Also, within each group (XP and controls), LCs were of significantly lower means in recurrent versus non-recurrent cases ( P ≤0.001 for all). Regarding recurrent BCC cases, peritumoral LCs showed a significant positive correlation with 1ry BCC duration ( P =0.05). Also, intratumoral and peritumoral LCs correlated positively with BCC relapse interval ( P =0.04 for both). Among non-XP controls, periocular tumors had the least LCs count (22.00±3.56), whereas tumors located in the rest of the face had the greatest count (29.00±0.00) ( P =0.02). Sensitivity and specificity of LCs to predict BCC recurrence in XP patients reached 100% in intartumoral area and perilesional epidermis when cutoff points were less than 9.5 and 20.5, respectively. In conclusion; reduced LC count in primary BCC specimens of XP patients and also in normal subjects could help to predict its recurrence. Thus, it might be identified as a risk factor for relapse to apply new strict therapeutic and preventive measures. This presents new avenue for the immunosurveillance against skin cancer relapse. However, being the first study to investigate that link in XP patients recommends further research to confirm.

Ross J, Scott Herron G. Genetic and Epigenetic Influences on Cutaneous Cellular Senescence

Skin is the largest human organ system, and its protective function is critical to survival. The epithelial, dermal, and subcutaneous compartments are heterogeneous mixtures of cell types, yet they all display age-related skin dysfunction through the accumulation of an altered phenotypic cellular state called senescence. Cellular senescence is triggered by complex and dynamic genetic and epigenetic processes. A senescence steady state is achieved in different cell types under various and overlapping conditions of chronological age, toxic injury, oxidative stress, replicative exhaustion, DNA damage, metabolic dysfunction, and chromosomal structural changes. These inputs lead to outputs of cell-cycle withdrawal and the appearance of a senescence-associated secretory phenotype, both of which accumulate as tissue pathology observed clinically in aged skin. This review details the influence of genetic and epigenetic factors that converge on normal cutaneous cellular processes to create the senescent state, thereby dictating the response of the skin to the forces of both intrinsic and extrinsic aging. From this work, it is clear that no single biomarker or process leads to senescence, but that it is a convergence of factors resulting in an overt aging phenotype.

The Roles of Skin Langerhans Cells in Immune Tolerance and Cancer Immunity

Langerhans cells (LC) are a unique population of tissue-resident macrophages with dendritic cell (DC) functionality that form a network of cells across the epidermis of the skin. Their location at the skin barrier suggests an important role for LC as immune sentinels at the skin surface. The classification of LC as DC over the past few decades has driven the scientific community to extensively study how LC function as DC-like cells that prime T cell immunity. However, LC are a unique type of tissue-resident macrophages, and recent evidence also supports an immunoregulatory role of LC at steady state and during specific inflammatory conditions, highlighting the impact of cutaneous environment in shaping LC functionality. In this mini review, we discuss the recent literature on the immune tolerance function of LC in homeostasis and disease conditions, including malignant transformation and progression; as well as LC functional plasticity for adaption to microenvironmental cues and the potential connection between LC population heterogeneity and functional diversity. Future investigation into the molecular mechanisms that LC use to integrate different microenvironment cues and adapt immunological responses for controlling LC functional plasticity is needed for future breakthroughs in tumor immunology, vaccine development, and treatments for inflammatory skin diseases.