Suppression of exosomal hsa_circ_0001005 eliminates the Vemurafenib resistance of melanoma.

Objectives: More and more evidences show that circular RNAs (circRNAs) can be used as miRNA sponge to regulate the drug resistance of malignancies, including melanoma. However, how exosomal circRNAs participate in the therapeutic resistance of melanoma remains ambiguous.

Methods: Vemurafenib-resistant A375 cells were cultured and then the circRNA profile of exosomes from the parental A375 and A375-resistant cells were sequenced. Transmission electron microscopy (TEM), exogenous nanoparticle tracking analysis (NTA) and Western Blot assays were leveraged to confirm the successful collection of exosomes from A375 and A375R cells. Another five published RNA-seq data and microRNA-seq data, and seven miRNA databases were collected to construct a competing endogenous RNA (ceRNA) network. Comprehensive bioinformatic analysis was adopted to identify key molecules related to the drug resistance, including multiscale embedded gene co-expression network analysis (MEGENA). Then, qRT-PCR, cell viability and colony formation were used to estimate the function of hub circRNAs. The role of has_circ_0001005 in vivo was verified via xenograft assay. The Tumor online Prognostic analyses Platform (ToPP) was leveraged to develop the has_circ_0001005-related prognostic models for melanoma patients based on TCGA data.

Results: Compared with parental cells, hsa_circ_0001005 expression was significantly increased in resistant cells and their exosomes. The elevated level of hsa_circ_0001005 was related to the poor clinical prognosis of melanoma patients. Hsa_circ_0001005 found in melanoma was mainly secreted by drug-resistant cells as exosomes. Exosomal hsa_circ_0001005 activated multiple canonical pathways related to drug resistance through sponging four miRNAs, thus suppressing the drug sensitivity of melanoma. Knocking down hsa_circ_0001005 in vitro, we found that the inhibition of hsa_circ_0001005 could hinder the clone formation of melanoma. Further in vivo animal experiments suggested that suppression of hsa_circ_0001005 can increase the sensitivity to Vemurafenib of melanoma cells. Finally, we also constructed the functional regulatory ceRNA network and prognostic risk models for hsa_circ_0001005, and further survival analysis reveals that the regulatory network and prognostic risk models obviously affected the prognosis of melanoma patients.

Conclusions: This study confirmed that the level of hsa_circ_0001005 in exosomes is the key factor affecting drug resistance of melanoma, which provides a new potential therapeutic target for melanoma patients.