RESUMEN
The RET fusion is considered as the potential novel target in solid tumors. However, RET fusion is not well yet identified in colorectal cancer (CRC), and the effect of RET kinase inhibitor is also not evaluated in CRC with RET fusion. We established patient-derived tumor cells (PDCs) with RET fusion from recurrent brain metastatic lesion that newly appeared during the surveillance for stage III CRC patient. To investigate therapeutic options to CRC patient with a RET fusion, we performed cell viability assays using the PDCs. NCOA4-RET fusion was detected by FusionPlex using the resected brain metastatic tissue of CRC patient with solitary brain metastasis and then reconfirmed by fluorescence in situ hybridization (FISH) test. We also confirmed the RET fusions by a qPCR in matched PDCs. We tested whether the PDCs from RET fusion colon cancer were sensitive to carbozantinib, sorafenib, vandetanib, and PD0331992. Cell viability assays showed that carbozantinib, sorafenib, and PD0332991 did not suppress cell viability. Only, vandetanib revealed the significant inhibitory effect in MTT proliferation assay. Next, we analyzed regulation of targeted downstream pathways upon exposure to vandetanib by immunoblot assay. In colon cancer PDCs with NCOA4-RET fusion, vandetanib potently inhibited AKT and ERK phosphorylation. This study shows that vandetanib might be one of useful treatment strategies for CRC patient with NCOA4-RET fusion. Therefore, inhibition of the RET kinase is a promising targeted therapy for cancer patients whose tumors harbor a RET rearrangement.
RESUMEN
Mesenchymal stem cells (MSCs) are capable of self-renewal and differentiation and are thus a valuable source for the replacement of diseased or damaged organs. Previously, we reported that the tonsils can be an excellent reservoir of MSCs for the regeneration of skeletal muscle (SKM) damage. However, the mechanisms involved in the differentiation from tonsil-derived MSCs (T-MSCs) to myocytes via myoblasts remain unclear. To clarify these mechanisms, we analyzed gene expression profiles of T-MSCs during differentiation into myocytes compared with human skeletal muscle cells (hSKMCs). Total RNA was extracted from T-MSCs, T-MSC-derived myoblasts and myocytes, and hSKMCs and was subjected to analysis using a microarray. Microarray analysis of the three phases of myogenic differentiation identified candidate genes associated with myogenic differentiation. The expression pattern of undifferentiated T-MSCs was distinguishable from the myogenic differentiated T-MSCs and hSKMCs. In particular, we selected FNBP1L, which among the upregulated genes is essential for antibacterial autophagy, since autophagy is related to SKM metabolism and myogenesis. T-MSCs differentiated toward myoblasts and skeletal myocytes sequentially, as evidenced by increased expression of autophagy-related markers (including Beclin-1, LC3B and Atg5) and decreased expression of Bcl-2. Furthermore, we reconfirmed that autophagy has an effect on the mechanism of skeletal myogenic differentiation derived from T-MSCs by treatment with 5-azacytidine and bafilomycin A1. These data suggest that the transcriptome of the T-MSC-derived myocytes is similar to that of hSKMCs, and that autophagy has an important role in the mechanism of myogenic differentiation of T-MSCs.
