Evaluation of the potential of overcoming the chemoresistance of melanoma to BRAFV600E (Vemurafenib) and MEK (Trametinib) inhibitors using combinatory therapy with 4-nerolidylcatechol (4-NC)

Author(s)

Débora Kristina Alves Fernandes

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2018-06-21

Examining board members

Silvya Stuchi Maria Engler; Ana Campa; Carmen Verríssima Ferreira; Leticia Veras Costa Lotufo

• Advisor: Silvya Stuchi Maria Engler; Silvia Berlanga de Moraes Barros

Abstract

Melanoma accounts for only 4% of malignant neoplasms of the skin, but is considered the most serious because it is highly deadly. Because the MAPK (Mitogen activated protein kinase) pathway is closely linked to the lack of control of cell proliferation, especially in melanoma, this pathway has become a target for the development of oncogene-targeted therapies, such as the potent chemotherapeutic agents Vemurafenib (V600E mutation inhibitor in BRAF - BRAFV600E) and Trametinib (MEK inhibitor). Increasingly, better response rates have been achieved with the new drugs, but most patients are subject to relapses after 7 months of treatment due to several mechanisms, which justify the constant search for new therapeutic compounds. Data from our laboratory indicate that 4-nerolidylcatechol (4-NC) induces increased p53 expression, ROS production and DNA damage, culminating in caspase-3 dependent apoptosis in melanoma cells. The 4-NC compound demonstrated an inhibitory effect on melanoma cell proliferation in an organotypic skin culture model. Thus, this project aims to evaluate the possibility of overcoming the existing chemoresistance to BRAF and MEK inhibitors, using 4-NC combinatory therapies in human melanoma cells resistant to these inhibitors. Firstly, melanoma cell lines resistant to BRAF (R) and BRAF / MEK (DR) inhibitors were generated from naive cells mutated BRAF (N) and characterized by MTT, fluorescence microscopy and western blotting. These cells were submitted to 4-NC treatment that showed cytotoxicity with 30 µM, inhibition of colony formation and decrease in invasion in 2D and 3D in vitro models in all cell line studied (N, R and DR). Furthermore, 4-NC was able to induce endoplasmic reticulum stress with apoptosis induction. In order to explore the in vivo therapeutic effect of 4-NC, an additional study was conducted using xenograft model with NRAS-mutated melanoma cell line. After tumor development, the animals were treated 3 times per week for 3 weeks with 4-NC (10 mg / kg) by i.p. injection. 4-NC was able to inhibit up to 4- fold the growth of xenograft tumors (4/10) when compared to controls, with complete tumor remission in one animal. Cleaved PARP and p53 expression were increased in the tumors of treated animals, suggesting apoptosis. MMP2 and MMP14 gene expression were decreased in the same samples, demonstrating the role of 4-NC in inhibiting melanoma invasion in vivo. Finally, the systemic toxicity of 4-NC was evaluated at the same doses employed in the in vivo tumorigenesis assay. The low toxicity observed in the toxicological assays with sub-chronic 4- NC treatments and the demonstrated cytotoxicity in xenograft models leads us to consider this compound as promising for future studies and its application in the treatment of cutaneous human melanoma, including patients resistants to BRAF and MEK inhibitors. (AU)

• FAPESP's process: 14/06959-0 - Evaluation of the potential for overcoming melanoma chemoresistance to BRAF V600E (Vemurafenib) and MEK (Trametinib) inhibitors using combined therapy with 4-nerolidylcatechol (4-NC)
• Grantee: Débora Kristina Alves Fernandes
• Support Opportunities: Scholarships in Brazil - Doctorate