Abstract 273: Extrinsic photoaging vs intrinsic aging in dermal fibroblasts: Its impact on the microenvironment and melanoma progression
Authors: Wang Vania , Chhabra Yash , Hueser Laura , Weeraratna Ashani 
Published: March 2024

Abstract
Melanoma is the deadliest form of skin cancer, with chronological aging as a major negative prognostic factor due to the influence of intrinsic aging on the tumor microenvironment (TME) to promote tumor initiation and progression. Ultraviolet radiation (UVR) exposure, which is a major risk factor for melanoma, also can cause a physical premature aging phenotype, known as extrinsic photoaging, from chronic UVA irradiation of the underlying dermis. Photoaging of the skin often occurs in tandem with chronological aging, and contributes to similar physical alterations in normal skin structure. However, the molecular mechanisms of how photoaging compares to chronological aging in changing the TME and on tumor progression is still lacking. Here we found that extrinsically photoaged fibroblasts have a higher level of secretion of lysosomal proteases, Cathepsins, which have been shown to be secreted via lysosomal exocytosis and play a functional role in extracellular matrix (ECM) remodeling at neutral PH levels. We found that Cathepsins B and D are secreted at higher levels in both extrinsically photoaged young fibroblasts and in intrinsically aged fibroblasts and upregulated at the endogenous protein level. Cathepsin B has been shown to be highly expressed in metastatic but not primary melanoma patient samples, and cleaves ECM proteins such as fibronectin and tenascin. Immunofluorescent staining of in-vitro fibroblast derived matrices (CDMs) confirmed that photoaging disrupts subsequent deposited extracellular matrix proteins similarly to that of intrinsically aged healthy fibroblasts and these matrix changes influences the growth pattern of melanoma lines plated on these CDMs. Mass spectrometry analysis of secreted proteomics confirmed that aged fibroblasts secrete more cathepsins than intrinsically young fibroblasts, and Cathepsins B and D were also detected in extracellular vesicle (EV) cargo proteomics. Single-Particle Interferometric Reflectance Imaging (SP-IRIS) of EVs showed that UVA irradiation induced a significant increase in the total number of secreted of exosomes and in expression of tetraspanin protein CD63, which plays a role in cargo sorting and has been detected in high levels in the plasma of melanoma patients. We hypothesize that extrinsic photoaging of fibroblasts induces the secretion of exosomes packaged with Cathepsins that play an integral role in ECM remodeling and matrix degradation in a beneficial manner for melanoma invasion. Further studies will assess the influence on secreted cathepsins on melanomagenesis and melanoma invasion through both mechanical and biochemical changes in the TME with in-vitro and in-vivo studies.
Citation Format: Vania Wang, Yash Chhabra, Laura Hueser, Ashani Weeraratna. Extrinsic photoaging vs intrinsic aging in dermal fibroblasts: Its impact on the microenvironment and melanoma progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 273.