dc.description.abstract | Melanoma is the most aggressive form of skin cancer. Vemurafenib (PLX4032) is an inhibitor of the V600E mutant form of BRAF gene (BRAFV600E) for the treatment of melanoma. However, melanoma patients treated with PLX4032 cause adverse reactions including resistance and the formation of secondary tumor. Most of the secondary tumors have 21%-60% RAS mutations, which enhances the BRAF-CRAF heterodimer formation to activate the MEK/ERK pathway. PLX8394, a novel BRAFV600E inhibitor, could inhibit BRAF-CRAF interaction. BRAFV600E inhibitor-induced secondary tumor development are not fully defined. Therefore, we hypothesized that exosomes released from melanoma treated with BRAFV600E inhibitors may affect the progression of secondary tumors which are originated from normal keratinocytes, epidermal cells.
In this study, the conditioned medium (CM) collected from keratinocytes, epithelial, melanoma cells and PLX4032-resistant melanoma cells treated with BRAFV600E inhibitor,
PLX4032 or PLX8394, were used to treat keratinocyte and epithelial cells to perform cell-based functional assay. The results showed that melanoma cells treated with PLX4032 enhanced the migration, anchorage-independent growth of keratinocyte or epidermal cells. Importantly, the migrative ability of keratinocyte cells cultured with the CM from resistant melanoma cells treated with PLX4032 was increased significantly as compared to parental melanoma cells. In
contrast, tumorigenesis of keratinocyte cells was not affected by cultured with the CM from parental or resistant melanoma cells treated with PLX8394.
Exosomes can transport cargo, including DNA, RNA, miRNA and proteins. We purified exosomes from CM and revealed the mechanism of the enhanced migration activity on keratinocytes are linked to exosomes transferred from melanoma cells. Moreover, exosomes derived from melanoma treated with PLX4032 increase BRAF-CRAF heterodimer expression of keratinocytes. Finally, we also collected CM from melanoma cells overexpressed miR-567 and observed that melanoma overexpression of miR-567 could decrease migration activity on keratinocytes.
In conclusion, exosomes derived from melanoma cells treated with PLX4032 enhanced migrative ability and BRAF-CRAF heterodimer expression of keratinocytes, in contrast, exosomes derived from melanoma cells treated with PLX8394 decreased migrative ability and BRAF-CRAF heterodimer expression of keratinocytes compared to melanoma cells treated with PLX4032. These results suggest that exosomes released from melanoma play a key role in secondary tumors progression. | en_US |