Lysyl OXidase Family Members’ Expression Analysis in Melanomas: Preliminary Data for a Novel Therapeutic Nanoformulation Development

Abstract body: Malignant melanoma is the deadliest skin cancer due to its aggressive behavior with a non-negligible portion of patients showing significant resistance to treatment, despite important advances in target and ICIs therapies. The phenotypic plasticity of melanoma cells, supported by an epithelial-to-mesenchymal (EMT)-like program, has been identified as a crucial process in melanoma development and therapy resistance [1]. The lysyl oxidase (LOX) protein family members are involved in tumor progression through extracellular and intracellular actions. Recently, LOXL3 expression has been related to cell survival, progression, and invasion in melanoma patients [2-4]. We performed an in silico TCGA data analysis on LOX family members' expression in melanoma. We found that both LOXL3 and LOXL4 isoforms are overexpressed in human skin cutaneous melanoma (SKCM) compared to normal skin, their expression is associated with a poorer prognosis and is significantly higher in BRAF-mutated melanomas. To specifically target these tumors, we are developing a nanoparticle carrying anti-BRAF and anti-MEK drugs, coated with anti-LOXL3/L4 antibodies [5]. With this aim, we explored both isoforms’ expression at RNA and protein levels in four melanoma cell lines and one primary line. We observed a variable yet increased expression of both isoforms in BRAF-mutated lines compared to the wild-type ones. Cells' sensitivity to an in-house-synthesized nanoformulation (Lipo) and the combination of anti-BRAF and anti-MEK drugs through an MTT assay were tested. Cell growth and viability were not affected by nanoparticles, while they were significantly reduced in BRAF-mutated A375 cells after treatment, compared to the wild-type MeWo line. Conclusions: Our in silico data analysis corroborates recent findings from other studies on the role of LOXL3 and LOXL4 proteins in the aggressiveness and prognosis of melanoma. Our experimental data confirm these findings and suggest L3 and L4 isoforms as potential therapeutic targets in BRAF-mutated melanomas. Thus, by combining BRAF inhibition with the active targeting of LOX isoforms, functionalized nanoformulations could be at our disposal as a novel target therapy to be developed soon. References: [1] Rambow F. et al., Genes Dev., 33 (2019) 1295–1318. [2] Santamaría, P.G. et al., Cell Death Differ, 25 (2017) 935–950. [3] Vázquez-Naharro A. et al., Cancers (Basel), 14 (2022) 1200. [4] Jun Li et al., Nanomedicine, 11 (2015) 769–794. [5] De Vita, A. et al., Sci Rep, 11 (2021) 5107. Key Words: Melanoma, LOX protein family members, in silico analysis, nanoformulation-based active targeting.