Early detection of cancer via biomarkers is vital for improving patient survival rates. In the case of skin cancers, low-molecular-weight biomarkers can penetrate the skin barrier, enabling non-invasive sampling at an early stage. This study focuses on detecting tryptophan (Trp) and kynurenine (Kyn) on the surface of reconstructed 3D melanoma and melanocyte models. This is examined in connection with IDO-1 and IL-6 expression in response to IFN-γ or UVB stimulation, both crucial factors of the melanoma tumor microenvironment (TME). Using a polystyrene scaffold, full-thickness human skin equivalents containing fibroblasts, keratinocytes, and melanocytes or melanoma cells were developed. The samples were stimulated with IFN-γ or UVB, and Trp and Kyn secretion was measured using HPLC-PDA and HPLC-MS. The expression of IDO-1 and IL-6 was measured using RT-qPCR. Increased Trp catabolism to Kyn was observed in IFN-γ-stimulated melanoma and melanocyte models, along with higher IDO-1 expression. UVB exposure led to significant changes in Kyn levels but only in the melanoma model. This study demonstrates the potential of skin surface Trp and Kyn monitoring to capture TME metabolic changes. It also lays the groundwork for future in vivo studies, aiding in understanding and monitoring skin cancer progression.

Spherical, multicellular aggregates of tumor cells, or three-dimensional (3D) tumor models, can be grown from established cell lines or dissociated cells from tissues in a serum-free medium containing appropriate growth factors. Air–liquid interfaces (ALIs) represent a 3D approach that mimics and supports the differentiation of respiratory tract and skin 3D models in vitro. Many 3D tumor cell models are cultured in conjunction with supporting cell types, such as fibroblasts, endothelial cells, or immune cells. To further mimic the in vivo situation, several extracellular matrix models are utilized to support tumor cell growth. Scaffolds used for 3D tumor cell culture growth include both natural and synthetic hydrogels. Three-dimensional cell culture experiments in vitro provide more accurate data on cell-to-cell interactions, tumor characteristics, drug discovery, metabolic profiling, stem cell research, and diseases. Moreover, 3D models are important for obtaining reliable precision data on therapeutic candidates in human clinical trials before predicting drug cytotoxicity. This review focuses on the recent literature on three different tissue types of 3D tumor models, i.e., tumors from a colorectal site, prostate, and skin. We will discuss the establishment of 3D tumor cell cultures in vitro and the requirement for additional growth support.

Molecularly imprinted polymers (MIPs) and the imprinting technique provide polymeric material with recognition elements similar to natural antibodies. The template of choice (i.e., the antigen) can be almost any type of smaller or larger molecule, protein, or even tissue. There are various formats of MIPs developed for different medical purposes, such as targeting, imaging, assay diagnostics, and biomarker detection. Biologically applied MIPs are widely used and currently developed for medical applications, and targeting the antigen with MIPs can also help in personalized medicine. The synthetic recognition sites of the MIPs can be tailor-made to function as analytics, diagnostics, and drug delivery systems. This review will cover the promising clinical applications of different MIP systems recently developed for disease diagnosis and treatment.