Vemurafenib and dabrafenib are BRAF kinase inhibitors (BRAFi) used for the treatment of patients with melanoma carrying the V600E BRAF mutation. However, melanoma cells develop resistance to both drugs when used as monotherapy. Therefore, mechanisms of drug resistance are investigated, and new molecular targets are sought that could completely inhibit melanoma progression. Since receptor-interacting protein kinase (RIPK4) probably functions as an oncogene in melanoma and its structure is similar to the BRAF protein, we analyzed the impact of vemurafenib and dabrafenib on RIPK4 in melanomas. The in silico study confirmed the high similarity of BRAF kinase domains to the RIPK4 protein at both the sequence and structural levels and suggests that BRAFi could directly bind to RIPK4 even more strongly than to ATP. Furthermore, BRAFi inhibited ERK1/2 activity and lowered RIPK4 protein levels in BRAF-mutated melanoma cells (A375 and WM266.4), while in wild-type BRAF cells (BLM and LoVo), both inhibitors decreased the level of RIPK4 and enhanced ERK1/2 activity. The phosphorylation of phosphatidylethanolamine binding protein 1 (PEBP1)—a suppressor of the BRAF/MEK/ERK pathway—via RIPK4 observed in pancreatic cancer did not occur in melanoma. Neither downregulation nor upregulation of RIPK4 in BRAF- mutated cells affected PEBP1 levels or the BRAF/MEK/ERK pathway. The downregulation of RIPK4 inhibited cell proliferation and the FAK/AKT pathway, and increased BRAFi efficiency in WM266.4 cells. However, the silencing of RIPK4 did not induce apoptosis or necroptosis. Our study suggests that RIPK4 may be an off-target for BRAF inhibitors.

Nowadays, there is great interest in the use of plant waste to obtain materials for environmental protection. In this study, silica powders were prepared with a simple and low-cost procedure from biomass materials such as horsetail and common reed, as well as wheat and rye straws. The starting biomass materials were leached in a boiling HCl solution. After washing and drying, the samples were incinerated at 700 °C for 1 h in air. The organic components of the samples were burned leaving final white powders. These powders were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and low-temperature nitrogen sorption. The amorphous powders (biosilica) contained mainly SiO₂, as indicated by FTIR analysis. Horsetail-derived silica was chosen for testing the removal of dichromate ions from water solutions. This biosilica had a good ability to adsorb Cr(VI) ions, which increased after modification of the powder with the dodecylamine surfactant. It can be concluded that the applied procedure allowed obtaining high purity biosilica from plant waste with good efficiency. The produced biosilica was helpful in removing chromium ions and showed low cytotoxicity to human endothelial cells, suggesting that it can be safely used in environmental remediation.

Melanoma cells remain resistant to chemotherapy with cisplatin (CisPt) and doxorubicin (DOX). The abnormal expression of Receptor-Interacting Protein Kinase 4 (RIPK4) in certain melanomas contributes to tumour growth through the NFκB and Wnt/β-catenin signalling pathways, which are known to regulate chemoresistance and recurrence. Despite this, the role of RIPK4 in response to chemotherapeutics in melanoma has not been reported. In this study, we examined how the downregulation and overexpression of RIPK4 affect the sensitivity of BRAF-mutated melanoma cells (A375 and WM266.4) to CisPt and DOX along with determining the underlying mechanism. Using two RIPK4 silencing methods (siRNA and CRISPR/Cas9) and overexpression (dCas9-VPR), we assessed CisPt and DOX-induced apoptosis using caspase 3/7 activity, annexin V/7AAD staining, and FASC analysis. In addition, qRT-PCR and Western blotting were used to detect apoptosis-related genes and proteins such as cleaved PARP, p53, and cyclin D1. We demonstrated that the overexpression of RIPK4 inhibits, while its downregulation enhances, CisPt- or DOX-induced apoptosis in melanoma cells. The effects of downregulation are similar to those observed with pre-incubation with cyclosporin A, an ABCG2 inhibitor. Additionally, our findings provide preliminary evidence of crosstalk between RIPK4, BIRC3, and ABCG2. The results of these studies suggest the involvement of RIPK4 in the observed resistance to CisPt or DOX.