Opposing Effects of EGF Receptor Signaling on Proliferation and Differentiation Initiated by EGF or TSH/EGF Receptor Transactivation

Regulation of thyroid cells by thyrotropin (TSH) and epidermal growth factor (EGF) has been known but different effects of these regulators on proliferation and differentiation have been reported. We studied these responses in primary cultures of human thyroid cells to determine whether TSH receptor (TSHR) signaling may involve EGF receptor (EGFR) transactivation. We confirm that EGF stimulates proliferation and de-differentiation whereas TSH causes differentiation in the absence of other growth factors. We show that TSH/TSHR transactivates EGFR and characterize it as follows: (1) TSH-induced upregulation of thyroid-specific genes is inhibited by 2 inhibitors of EGFR kinase activity, AG1478 and erlotinib; (2) the mechanism of transactivation is independent of an extracellular EGFR ligand by showing that 2 antibodies, cetuximab and panitumumab, that completely inhibited binding of EGFR ligands to EGFR had no effect on transactivation, and by demonstrating that no EGF was detected in media conditioned by thyrocytes incubated with TSH; (3) TSH/TSHR transactivation of EGFR is different than EGFR activation by EGF by showing that EGF led to rapid phosphorylation of EGFR whereas transactivation occurred in the absence of receptor phosphorylation; (4) EGF caused downregulation of EGFR whereas transactivation had no effect on EGFR level; (5) EGF and TSH stimulation converged on the protein kinase B (AKT) pathway, because TSH, like EGF, stimulated phosphorylation of AKT that was inhibited by EGFR inhibitors; and (6) TSH-induced upregulation of thyroid genes was inhibited by the AKT inhibitor MK2206. Thus, TSH/TSHR causes EGFR transactivation that is independent of extracellular EGFR ligand and in part mediates TSH regulation of thyroid hormone biosynthetic genes.

Catestatin induces glycogenesis by stimulating the phosphoinositide 3-kinase-AKT pathway

AIM

Defects in hepatic glycogen synthesis contribute to post-prandial hyperglycaemia in type 2 diabetic patients. Chromogranin A (CgA) peptide Catestatin (CST: hCgA352-372 ) improves glucose tolerance in insulin-resistant mice. Here, we seek to determine whether CST induces hepatic glycogen synthesis.

METHODS

We determined liver glycogen, glucose-6-phosphate (G6P), uridine diphosphate glucose (UDPG) and glycogen synthase (GYS2) activities; plasma insulin, glucagon, noradrenaline and adrenaline levels in wild-type (WT) as well as in CST knockout (CST-KO) mice; glycogen synthesis and glycogenolysis in primary hepatocytes. We also analysed phosphorylation signals of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-dependent kinase-1 (PDK-1), GYS2, glycogen synthase kinase-3β (GSK-3β), AKT (a kinase in AKR mouse that produces Thymoma)/PKB (protein kinase B) and mammalian/mechanistic target of rapamycin (mTOR) by immunoblotting.

RESULTS

CST stimulated glycogen accumulation in fed and fasted liver and in primary hepatocytes. CST reduced plasma noradrenaline and adrenaline levels. CST also directly stimulated glycogenesis and inhibited noradrenaline and adrenaline-induced glycogenolysis in hepatocytes. In addition, CST elevated the levels of UDPG and increased GYS2 activity. CST-KO mice had decreased liver glycogen that was restored by treatment with CST, reinforcing the crucial role of CST in hepatic glycogenesis. CST improved insulin signals downstream of IR and IRS-1 by enhancing phospho-AKT signals through the stimulation of PDK-1 and mTORC2 (mTOR Complex 2, rapamycin-insensitive complex) activities.

CONCLUSIONS

CST directly promotes the glycogenic pathway by (a) reducing glucose production, (b) increasing glycogen synthesis from UDPG, (c) reducing glycogenolysis and (d) enhancing downstream insulin signalling.

An Immunohistochemical Study of the PTEN/AKT Pathway Involvement in Canine and Feline Mammary Tumors

Simple Summary

The PTEN/AKT pathway is involved in several human and animal tumors’ pathogenesis. This study investigates the PTEN/AKT pathway’s biological and prognostic values in canine and feline mammary tumors. PTEN, phospho-AKT (p-AKT) and Rictor expression was determined by immunohistochemistry in canine mammary adenomas and carcinomas and feline mammary carcinomas. In mammary tumors of both species p-Akt was inversely correlated with PTEN expression and positively with Rictor expression; p-Akt and Rictor expression correlated with poorer prognosis. This data could provide a rationale for further studies of this pathway in veterinary oncology due to prognostic and therapeutic implications.

Abstract

Phosphatase and tensin homolog deleted on chromosome10 (PTEN), phospho-v-Akt murine thymoma viral oncogene homolog (AKT), and the Rapamycin-Insensitive Companion of mTOR (Rictor) expression was investigated by immunohistochemistry in 10 canine mammary adenomas (CMAs), 40 canine mammary carcinomas (CMCs), and 30 feline mammary carcinomas (FMCs). All the CMAs, 25 of 40 CMCs (63%) and 7 of 30 FMCs (23%), were PTEN-positive. In dogs, no CMAs and 15 of 25 CMCs (37%) expressed phospho-AKT (p-AKT), while 24 of 30 FMCs (82%) were p-AKT-positive. One of 10 CMAs (10%), 24 of 40 CMCs (60%) and 20 of 30 FMCs (67%) were Rictor-positive. In the dog, PTEN expression correlated with less aggressive tumors, absence of lymphatic invasion, and longer survival. P-AKT expression correlated with more aggressive subtype, lymphatic invasion, and poorer survival and Rictor expression with lymphatic invasion. In cats, PTEN correlated with less aggressive carcinomas, absence of lymphatic invasion, and better survival. P-AKT and Rictor expression correlated with poorer survival. PTEN expression was inversely correlated with p-AKT and Rictor in both species, while p-AKT positively correlated with Rictor expression. A strong PTEN/AKT pathway involvement in behavior worsening of CMT and FMTs is demonstrated, providing a rationale for further studies of this pathway in veterinary oncology.

Human telomerase reverse transcriptase in papillary thyroid cancer: gene expression, effects of silencing and regulation by BET inhibitors in thyroid cancer cells

PURPOSE

Mutations in TERT promoter have been detected in the more aggressive papillary thyroid cancers (PTCs). To elucidate the role of TERT as an eligible molecular target in these tumors, the expression of hTERT was analyzed in a series of PTCs and the effects of both pharmacological and RNA-interference-induced hTERT silencing were investigated in two human PTC cell lines (K1 and BCPAP).

METHODS

The expression levels of hTERT mRNA and protein were evaluated by real-time PCR and western blot assays, respectively. Effects of hTERT silencing on PTC cell lines were analyzed by MTT, migration and western blot assays. Pharmacological inhibition of hTERT was performed using two bromodomain and extra-terminal (BET) inhibitors, JQ1 and I-BET762.

RESULTS

hTERT expression results increased in 20 out of 48 PTCs, including tumors either positive or negative for the presence of hTERT promoter and/or BRAF mutations. In K1 and BCPAP cells, hTERT silencing determined a reduction in cell viability (~50% for K1 and ~70%, for BCPAP, vs control) and migration properties that were associated with a decrease of AKT phosphorylation and β-Catenin expression. Moreover, hTERT mRNA levels were down-regulated by two BET inhibitors, JQ1 and I-BET762, which at the same dosage (0.5 and 5 µM) reduced the growth of these thyroid cancer cells.

CONCLUSIONS

These findings demonstrate that hTERT may represent an excellent therapeutic target in subgroups of aggressive PTCs.

Effects of Quercetin, Kaempferol, and Exogenous Glutathione on Phospho- and Total-AKT in 3T3-L1 Preadipocytes

Obesity has been reported to be a risk factor for some types of cancer, such as prostate and lung. The AKT or PI3K-AKT is a signal transduction pathway that promotes survival and growth in response to extracellular signals. The aim of this study was to investigate the effects of two flavonoids, quercetin and kaempferol, and exogenous glutathione (GSH) on the expressions of phospho- and total-AKT levels in 3T3-L1 preadipocytes. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) levels were measured in the treated samples and used as the internal standard. 3T3-L1 preadipocytes were exposed to each flavonoid and GSH at concentrations of 0, 5, 10, 15, 20, and 25 µM, and the levels of phospho- and total-Akt were measured by the MILLIPLEX MAP mates protocol, based on the Luminex xMAP technology (Millipore Corp., St. Charles, MI, USA). GAPDH levels in the preadipocytes were not significantly different at the doses tested for the flavonoids and exogenous GSH. However, significant (p <.05) decreases in phospho-AKT levels in cells treated with quercetin, kaempferol, and GSH at certain doses were observed compared to their respective controls. Total-AKT levels showed the same profile for all the tested compounds. Significant (p <.01) differences were observed for kaempferol (15-25 µM), quercetin at 10 and 20 µM, and GSH at 10 µM compared to their respective controls. Findings suggest that exposure of 3T3-L1 preadipocytes to quercetin, kaempferol, and GSH may block the activation of AKT, suggesting the role such compounds play in cell differentiation in 3T3-L1 cells.

A correlation analysis between tumor imaging changes and p-AKT and HSP70 expression in tumor cells after osteosarcoma chemotherapy

This study sought to investigate osteosarcoma property changes after neoadjuvant chemotherapy and to analyze any correlation between changes with phospho-AKT (p-AKT) and heat shock protein 70 (HSP70) expression in osteosarcoma cells. Thirty patients with osteosarcoma treated at Liaocheng People's Hospital between January and October, 2016 were given an imaging examination before and after neoadjuvant chemotherapy to examine osteosarcoma tumor properties, with images scored. Immunohistochemistry was used to determine p-AKT and HSP70 expression levels, as well as tumor cell necrosis rate (TCNR), in specimens obtained before and after chemotherapy. The correlation between the imaging changes of osteosarcoma after chemotherapy and the expressions of p-AKT and HSP70 in tumor cells. Compared with pre-chemotherapy, the imaging scores of the 30 patients significantly increased after chemotherapy (P<0.05). The radiographic score of the TCNR ≥90% group was 11.3±0.5, which was significantly higher than that of the TCNR <90% group (8.7±0.3, P<0.05). p-AKT expression in osteosarcoma cells was found in 13.3% of samples (4/30 cases) after chemotherapy, which was significantly lower than prior to chemotherapy (73.3%, 22/30 cases, P<0.05). After chemotherapy, HSP70 expression in osteosarcoma cells was found in 6.7% of samples (2/30 cases), which was significantly lower than prior to chemotherapy (83.3%, 25/30 cases, P<0.05). p-AKT and HSP70 expression levels were found to be correlated with TCNR after chemotherapy (P<0.05). After chemotherapy, p-AKT and HSP70 expression levels demonstrated a positive correlation with TCNR. Tumor property changes, as uncovered by imaging, were significantly inversely correlated with tumor cell p-AKT and HSP70 expression after chemotherapy. Therefore, osteosarcoma properties, as determined through X-ray imaging, were closely related to p-AKT and HSP70 expression in osteosarcoma cells after neoadjuvant chemotherapy. The effect of chemotherapy can be evaluated by observing the above examination results.