Supplemental Digital Content is available in the text

No abstract

Supplemental Digital Content is available in the text

Supplemental Digital Content is available in the text

Persistent cellular proliferation and metabolic reprogramming are essential processes in carcinogenesis. Here, we performed Gene Set Enrichment Analysis (GSEA) and found that that LETM1, a mitochondrial calcium transporter, is associated with cellular growth signals such as platelet-derived growth factor (PDGF) receptor signaling and insulin signaling pathways. These results were then verified by qRT-PCR and immnunoblotting. Mechanistically, up-regulation of LETM1 induced YAP1 nuclear accumulation, increasing the expression of PDGFB, PDGFRB and THBS4. Consistent with this, LETM1 silencing caused loss of YAP1 nuclear signal, decreasing the expression of PDGFB, PDGFRB and THBS4. Immunohistochemical staining consistently indicated a positive association between LETM1 up-regulation, YAP1 nuclear localization and high PDGFB expression. In clinical data analysis, LETM1 up-regulation in thyroid cancer was found to be related to aggressive tumor features such as lymphovascular invasion (LVI, P < 0.001) and lymph node metastasis (LNM, P = 0.011). Multivariate analysis demonstrated that LETM1 up-regulation increases the risk of LVI and LNM (OR = 3.455, 95% CI = 1.537–7.766 and OR = 3.043, 95% CI = 1.282–7.225, respectively). Collectively, these data suggest that up-regulation of LETM1 induces sustained activation of proliferative signaling pathways, such as PDGF signal pathway by AKT induced YAP1 transactivation, resulting in aggressive thyroid cancer phenotypes.

Kinase suppressor of RAS1 (KSR1) is a scaffold protein implicated in RAS-mediated RAF activation. However, the molecular function of KSR in papillary thyroid cancer (PTC) is unknown. Thus, this study aimed to characterize the role of KSR1 in patients with PTC. qRT-PCR and immunohistochemistry (IHC) revealed inter-tumor heterogeneities in the expression of KSR1 in PTC tissues. Interestingly, BRAFV600E-positive PTC showed higher KSR1 mRNA expression than BRAFV600E-negative PTC (P!0.001). Gene Set Enrichment Analysis (GSEA) using public repositories showed that high KSR1 expression coordinately upregulated Notch signaling (nominal PZ0.019, false discovery rate (FDR) q-valueZ0.165); this finding was supported by GeneNetwork analysis, indicating that KSR1 expression is positively correlated with NOTCH1 expression (rZ0.677, PZ6.15!10 K9 ). siRNA against KSR1 (siKSR1) significantly decreased ERK phosphorylation induced by BRAFV600E, resulting in reduced expression of NOTCH1 and HES1, targets of Notch signaling. GSEA revealed that high KSR1 expression was also associated with downregulation of genes related to oxidative phosphorylation (OxPhos). Consistent with this, electron microscopy showed that PTCs with high KSR1 expression exhibited structural defects of the mitochondrial cristae. Furthermore, siKSR1-transfected BCPAP and 8505C cells generated fewer colonies in colony-forming assays. In addition, GSEA showed that high expression of KSR2 and connector enhancer of KSR1 (CNKSR1) also coordinately upregulated Notch signaling (KSR2: nominal PZ0.0097, FDR q-valueZ0.154 and CNKSR1: nominal P!0.0001, FDR q-valueZ0.00554), and high CNKSR2 was associated with downregulation of the OxPhos gene set (nominal P!0.0001, FDR q-value !0.0001). In conclusion, KSR1 is coordinately regulated with Notch signaling and OxPhos in PTC, because its scaffold function might be required to sustain the proliferative signaling and metabolic remodeling associated with this type of cancer.

Non-small cell lung cancer (NSCLC) is a malignant lung tumor with a dismal prognosis. The activation of the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway is common in many tumor types including NSCLC, which results in radioresistance and changes in the tumor microenvironment. Although pan-PI3K inhibitors have been tested in clinical trials to overcome radioresistance, concerns regarding their excessive side effects led to the consideration of selective inhibition of PI3K isoforms. In this study, we assessed whether combining radiation with the administration of the PI3K isoform-selective inhibitors reduces radioresistance and tumor growth in NSCLC. Inhibition of the PI3K/AKT pathway enhanced radiosensitivity substantially, and PI3K-α inhibitor showed superior radiosensitizing effect similar to PI3K pan-inhibitor, both in vitro and in vivo. Additionally, a significant increase in DNA double-strand breaks (DSB) and a decrease in migration ability were observed. Our study revealed that combining radiation and the PI3K-α isoform improved radiosensitivity that resulted in a significant delay in tumor growth and improved survival rate.

No abstract