Activated E2F activity induces cell death in papillary thyroid carcinoma K1 cells with enhanced Wnt signaling

LMO3 promotes proliferation and metastasis of papillary thyroid carcinoma cells by regulating LIMK1-mediated cofilin and the β-catenin pathway

LIM domain only 3 (LMO3) interacts with transcription factors to regulate target genes involved in embryonic development. The oncogenic role of LMO3 in hepatocellular carcinoma, gastric cancer, and neuroblastoma has been reported recently. However, little is known about the biological function of LMO3 in papillary thyroid carcinoma (PTC). First, expression of LMO3 was dramatically enhanced in the PTC tissues and cell lines. Second, knockdown of LMO3 in PTC cells repressed cell proliferation and promoted cell apoptosis with downregulated Bcl-2 and upregulated cleaved caspase-3/PARP. In vitro cell migration and invasion of PTC were also retarded by siRNA-mediated silence of LMO3. Third, protein expression of LIM kinase (LIMK) 1-mediated phosphorylation of cofilin and nuclear translocation of β-catenin were reduced by the knockdown of LMO3. pcDNA-mediated overexpression of LIMK1 promoted cofilin phosphorylation and attenuated LMO3 silence-induced decrease of cofilin phosphorylation. Last, enhanced LIMK1 expression promoted PTC cell proliferation and metastasis and counteracted the suppressive effects of LMO3 silence on PTC cell proliferation and metastasis. In conclusion, LMO3 promoted PTC cell proliferation and metastasis by regulating LIMK1-mediated cofilin and the β-catenin pathway.

Salinomycin and its derivatives as potent RET transcriptional inhibitors for the treatment of medullary thyroid carcinoma

Rearranged during transfection kinase (RET) is a validated molecular target in medullary thyroid cancer (MTC), as activating mutations in RET are often associated with the development of MTC. The present study reports the first preclinical characterization of salinomycin and selected analogs as potent RET transcriptional inhibitors. Reverse transcription‑PCR and immunoblotting revealed that salinomycin profoundly decreased RET expression in the TT human MTC cell line by inhibiting RET transcription. Moreover, salinomycin resulted in remarkable anti‑proliferative activity against MTC that is driven by RET (gain of function mutation) by selectively inhibiting the intracellular PI3K/Akt/mTOR signaling pathway. Also, flow cytometry and fluorescence‑activated cell sorting showed that salinomycin induces G1 phase arrest and apoptosis by reducing the expression of retinoblastoma protein, E2F1, cyclin D and CDK4. The structure‑activity relationship of salinomycin was investigated in this study. Some of the salinomycin derivatives showed the ability to reduce RET expression where others fail to alter RET expression. These results suggest that the RET‑suppressing effect of salinomycin may be largely attributed to disruption of the Wnt pathway, presumably through interference with the ternary LRP6‑Frizzled‑Wnt complex. Furthermore, these findings support the further preclinical evaluation of salinomycin and its analogs as a promising new class of therapeutic agents for the improved treatment of MTC.

Long Noncoding RNA LOC100129940-N Is Upregulated in Papillary Thyroid Cancer and Promotes the Invasion and Progression

Thyroid cancer is the most common endocrine malignancy, and its incidence has increased rapidly in recent decades worldwide. Papillary thyroid cancer (PTC) is the most common type of all thyroid cancers. The molecular mechanisms underlying the disease still need to be further investigated. Long noncoding RNAs (lncRNAs), a class of noncoding RNAs (ncRNAs) longer than 200 nucleotides, are aberrantly expressed in malignant diseases, including PTC. Here, we identified a novel isoform of LOC100129940 and designated it as LOC100129940-N. We demonstrated that the expression level of LOC100129940-N was elevated in PTC, indicating that LOC100129940-N may be involved in PTC development and progression. Moreover, our results showed that overexpression of LOC100129940-N promoted, whereas silencing of LOC100129940-N suppressed, PTC cell proliferation, invasion, and migration. Mechanistically, LOC100129940-N played an important role in activating Wnt/β-catenin signaling and upregulating downstream target genes. Taken together, we demonstrate that LOC100129940-N promotes the activation of Wnt/β-catenin signaling, which in turn regulates the downstream target genes, thereby enhancing invasion and progression of PTC.

Telomerase reverse transcriptase induced thyroid carcinoma cell proliferation through PTEN/AKT signaling pathway

Thyroid carcinoma is the most common endocrine malignant tumor in the world, and so, there is a requirement to develop novel molecular targets for thyroid cancer diagnosis and treatment. Telomerase reverse transcriptase (TERT) was revealed to promote cell proliferation in a number of types of cell. To evaluate whether and how TERT functioned on papillary thyroid cancer (PTC) cell proliferation, the present study constructed TERT over‑expression [recombined (r)TERT plasmid group] and interference [small interfering RNA (si)‑TERT group] models by liposome transfection respectively to study the molecular mechanisms. The transfection efficiency was first detected by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting to analyze TERT levels compared with the negative control (NC) and control groups. Then MTT and carboxyfluorescein diacetate succinimidyl ester assays were performed to determine living cell proliferation and total cell proliferation respectively. Propidium iodide assay was used to detect alterations in cell cycle progression. RT‑qPCR and western blotting were performed to detect associated factor variation. The results demonstrated that, following the generation of TERT overexpression or silencing PTC cells, the living cells and also total cell proliferation increased significantly in the rTERT group, and decreased significantly in siTERT group, when compared with the NC and control groups. The cell cycle was accelerated in the rTERT group, and blocked in the G1/S transition in the siTERT group. The mRNA and protein levels of P27, P53 and phosphatase and tensin homolog (PTEN) decreased significantly in the rTERP group and increased in the siTERP group, while cyclin dependent kinase 2 and Cyclin D1 increased significantly in the rTERP group and decreased in the siTERP group. The expression of cell division cycle 25A did not alter significantly. The protein levels of β‑catenin and retinoblastoma were also unaltered. Protein kinase B (AKT) was detected once activated by TERT, and there were increased phosphorylated (p)‑AKT protein levels in the rTERT group, and decreased p‑AKT protein levels in the siTERT group. In conclusion, TERT could induce thyroid carcinoma cell proliferation mainly through the PTEN/AKT signaling pathway.