Abstract 60P
Background
Translation rewiring plays a crucial role during oncogenesis and is deregulated in several types of cancer, including melanoma. Cutaneous melanoma (CM), the deadliest form of skin cancer, is most commonly mutated in the BRAF gene. Targeted drugs against BRAF, although effective at first, quickly result in acquired resistance though mechanisms involving the translation process. The translation initiation factor eIF6 regulates the maturation of 60S ribosomal subunit and the 80S ribosome formation. Its involvement in CM progression was recently reported while a possible role in selective translation of mRNAs that could promote tumorigenesis has been proposed. However, its role in CM progression and response to targeted therapy remains unclear.
Methods
Generation of eIF6 stably overexpressing cell lines was performed using a lentiviral approach. Five different human and mouse melanoma cell lines were used, each representing a different subtype of CM. Determination of the IC50 of vemurafenib in each case was performed using resazurin assay. Puromycin staining and ribosome and polysome profile analyses using sucrose density gradients were used to examine the effects of eIF6 on protein synthesis. Key signaling pathways affected in each case were determined by Western immunoblotting.
Results
eIF6 led to elevated levels of 60S ribosomal subunits in all cases, while the response to vemurafenib varied among different subtypes. Notably, two of the cell lines exhibited enhanced resistance to vemurafenib in the presence of eFI6, whereas the remaining three demonstrated increased susceptibility to BRAF inhibition. This response was correlated with the differential expression pattern of the central mTOR kinase and the phosphorylation state of ERK. Additionally, opposite effects on the translation machinery were observed, suggesting a complex regulatory role of eIF6.
Conclusions
Acquired resistance to targeted therapies presents a significant challenge in the management of CM patients. Our findings indicate the involvement of eFI6 in the response of melanoma cells to BRAF inhibitors, offering potential insights for novel therapeutic approaches to overcome vemurafenib resistance.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Hellenic Foundation for Research & Innovation and the Fulbright Foundation in Greece.
Disclosure
All authors have declared no conflicts of interest.