Inhibition of cPLA2-Mediated Arachidonic Acid Release by Cyclic AMP Defines a Negative Feedback Loop for P2Y-Receptor Activation in Mdck-D1 Cells

In Madin-Darby canine kidney D1cells extracellular nucleotides activate P2Y receptors that couple to several signal transduction pathways, including stimulation of multiple phospholipases and adenylyl cyclase. For one class of P2Y receptors, P2Y2 receptors, this stimulation of adenylyl cyclase and increase in cAMP occurs via the conversion of phospholipase A2 (PLA2)-generated arachidonic acid (AA) to prostaglandins (e.g. PGE2). These prostaglandins then stimulate adenylyl cyclase activity, presumably via activation of prostanoid receptors. In the current study we show that agents that increase cellular cAMP levels (including PGE2, forskolin, and the β-adrenergic agonist isoproterenol) can inhibit P2Y receptor-promoted AA release. The protein kinase A (PKA) inhibitor H89 blocks this effect, suggesting that this feedback inhibition occurs via activation of PKA. Studies with PGE2indicate that inhibition of AA release is attributable to inhibition of mitogen-activated protein kinase activity and in turn of P2Y receptor stimulated PLA2 activity. Although cAMP/PKA-mediated inhibition occurs for P2Yreceptor-promoted AA release, we did not find such inhibition for epinephrine (α1-adrenergic) or bradykinin-mediated AA release. Taken together, these results indicate that negative feedback regulation via cAMP/PKA-mediated inhibition of mitogen-activated protein kinase occurs for some, but not all, classes of receptors that promote PLA2 activation and AA release. We speculate that receptor-selective feedback inhibition occurs because PLA2activation by different receptors in Madin-Darby canine kidney D1 cells involves the utilization of different signaling components that are differentially sensitive to increases in cAMP or, alternatively, because of compartmentation of signaling components

Induction of Thyroid Gene Expression and Radioiodine Uptake in Melanoma Cells: Novel Therapeutic Implications

Both the MAP kinase and PI3K/Akt pathways play an important role in the pathogenesis of melanoma. We conducted the present study to test the hypothesis that targeting the two pathways to potently induce cell inhibition accompanied with thyroid iodide-handling gene expression for adjunct radioiodine ablation could be a novel effective therapeutic strategy for melanoma. We used specific shRNA approaches and inhibitors to individually or dually suppress the MAP kinase and PI3K/Akt pathways and examined the effects on a variety of molecular and cellular responses of melanoma cells that harbored activating genetic alterations in the two pathways. Suppression of the MAP kinase and PI3K/Akt pathways showed potent anti-melanoma cell effects, including the inhibition of cell proliferation, transformation and invasion, induction of G0/G1 cell cycle arrest and, when the two pathways were dually suppressed, cell apoptosis. Remarkably, suppression of the two pathways, particularly simultaneous suppression of them, also induced expression of genes that are normally expressed in the thyroid gland, such as the genes for sodium/iodide symporter and thyroid-stimulating hormone receptor. Melanoma cells were consequently conferred the ability to take up radioiodide. We conclude that dually targeting the MAP kinase and PI3K/Akt pathways for potent cell inhibition coupled with induction of thyroid gene expression for adjunct radioiodine ablation therapy may prove to be a novel and effective therapeutic strategy for melanoma

BRAF V600E Status Sharply Differentiates Lymph Node Metastasis-associated Mortality Risk in Papillary Thyroid Cancer

[Context]: How lymph node metastasis (LNM)-associated mortality risk is affected by BRAF V600E in papillary thyroid cancer (PTC) remains undefined. [Objective]: To study whether BRAF V600E affected LNM-associated mortality in PTC. [Design, Setting, and Participants]: We retrospectively analyzed the effect of LNM on PTC-specific mortality with respect to BRAF status in 2638 patients (2015 females and 623 males) from 11 centers in 6 countries, with median age of 46 [interquartile range (IQR) 35-58] years and median follow-up time of 58 (IQR 26-107) months. [Results]: Overall, LNM showed a modest mortality risk in wild-type BRAF patients but a strong one in BRAF V600E patients. In conventional PTC (CPTC), LNM showed no increased mortality risk in wild-type BRAF patients but a robustly increased one in BRAF V600E patients; mortality rates were 2/659 (0.3%) vs 4/321 (1.2%) in non-LNM vs LNM patients (P = 0.094) with wild-type BRAF, corresponding to a hazard ratio (HR) (95% CI) of 4.37 (0.80-23.89), which remained insignificant at 3.32 (0.52-21.14) after multivariate adjustment. In BRAF V600E CPTC, morality rates were 7/515 (1.4%) vs 28/363 (7.7%) in non-LNM vs LNM patients (P < 0.001), corresponding to an HR of 4.90 (2.12-11.29) or, after multivariate adjustment, 5.76 (2.19-15.11). Adjusted mortality HR of coexisting LNM and BRAF V600E vs absence of both was 27.39 (5.15-145.80), with Kaplan-Meier analyses showing a similar synergism. [Conclusions]: LNM-associated mortality risk is sharply differentiated by the BRAF status in PTC; in CPTC, LNM showed no increased mortality risk with wild-type BRAF but a robust one with BRAF mutation. These results have strong clinical relevance.This work was supported partly by the following funding at the individual participating centers: Polish National Center of Research and Development MILESTONE Project—molecular diagnostics and imaging in individualized therapy for breast, thyroid and prostate cancer, grant No. STRATEGMED2/267398/4/ NCBR/2015 (Poland, AC, BJ); Grants No. PID2019-105303RB-I00 (AEI from MICINN), GCB14142311CRES (AECC Foundation), and B2017/BMD-3724 TIRONET2-CM (Spain; PS and GR-E); Grant No. AZV 16-32665A and MH CZ-DRO (Institute of Endocrinology-EU, 00023761) (Czech Republic; BB, VS); NIH/ National Institute on Aging Grant No. 5R03AG042334-02 (LY); and grants from the Qingdao Science and Technology Project for People’s Livelihood No.13-1-3-58-nsh (China; FW) and the Innovative Platform Project of Qingdao No.12-1-2-15-jch (China; YW)

Somatic mutation and gain of copy number of PIK3CA in human breast cancer

INTRODUCTION: Phosphatidylinositol 3-kinases (PI3Ks) are a group of lipid kinases that regulate signaling pathways involved in cell proliferation, adhesion, survival, and motility. Even though PIK3CA amplification and somatic mutation have been reported previously in various kinds of human cancers, the genetic change in PIK3CA in human breast cancer has not been clearly identified. METHODS: Fifteen breast cancer cell lines and 92 primary breast tumors (33 with matched normal tissue) were used to check somatic mutation and gene copy number of PIK3CA. For the somatic mutation study, we specifically checked exons 1, 9, and 20, which have been reported to be hot spots in colon cancer. For the analysis of the gene copy number, we used quantitative real-time PCR and fluorescence in situ hybridization. We also treated several breast cancer cells with the PIK3CA inhibitor LY294002 and compared the apoptosis status in cells with and without PIK3CA mutation. RESULTS: We identified a 20.6% (19 of 92) and 33.3% (5 of 15) PIK3CA somatic mutation frequency in primary breast tumors and cell lines, respectively. We also found that 8.7% (8 of 92) of the tumors harbored a gain of PIK3CA gene copy number. Only four cases in this study contained both an increase in the gene copy number and a somatic mutation. In addition, mutation of PIK3CA correlated with the status of Akt phosphorylation in some breast cancer cells and inhibition of PIK3CA-induced increased apoptosis in breast cancer cells with PIK3CA mutation. CONCLUSION: Somatic mutation rather than a gain of gene copy number of PIK3CA is the frequent genetic alteration that contributes to human breast cancer progression. The frequent and clustered mutations within PIK3CA make it an attractive molecular marker for early detection and a promising therapeutic target in breast cancer

Induction of Sodium/Iodide Symporter (NIS) Expression and Radioiodine Uptake in Non-Thyroid Cancer Cells

Background: This study was designed to explore the therapeutic potential of suppressing MAP kinase and PI3K/Akt pathways and histone deacetylase (HDAC) to induce the expression of sodium/iodide symporter (NIS) and radioiodine uptake in non-thyroid cancer cells. Methods: We tested the effects of the MEK inhibitor RDEA119, the Akt inhibitor perifosine, and the HDAC inhibitor SAHA on NIS expression in thirteen human cancer cell lines derived from melanoma, hepatic carcinoma, gastric carcinoma, colon carcinoma, breast carcinoma, and brain cancers. We also examined radioiodine uptake and histone acetylation at the NIS promoter in selected cells. Results: Overall, the three inhibitors could induce NIS expression, to various extents, in melanoma and all the epithelial carcinoma-derived cells but not in brain cancer-derived cells. SAHA was most effective and its effect could be significantly enhanced by RDEA119 and perifosine. The expression of NIS, at both mRNA and protein levels, was most robust in the melanoma cell M14, hepatic carcinoma cell HepG2, and the gastric carcinoma cell MKN-7 cell. Radioiodine uptake was correspondingly induced, accompanied by robust increase in histone acetylation at the NIS promoter, in these cells when treated with the three inhibitors. Conclusions: This is the first demonstration that simultaneously suppressing the MAP kinase and PI3K/Akt pathways and HDAC could induce robust NIS expression and radioiodine uptake in certain non-thyroid human cancer cells, providing novel therapeutic implications for adjunct radioiodine treatment of these cancers

Identifying Genetic Alterations in Poorly Differentiated Thyroid Cancer: A Rewarding Pursuit

The concept of \u93poorly differentiated thyroid carcinoma\u94 (PDTC) was initially proposed more than 25 yr ago ( 1, 2). It described a subgroup of thyroid carcinomas that seemed to fall, in terms of clinicopathological behaviors and aggressiveness, between the classically defined differentiated papillary thyroid carcinomas (PTC)/follicular thyroid carcinomas (FTC) and the undifferentiated anaplastic thyroid carcinomas (ATC). Over the next 20 yr of research, numerous studies supported the existence of such a clinicopathological entity of thyroid carcinoma, leading to the official inclusion of PDTC as a separate tumor entity in the World Health Organization (WHO) classification of thyroid tumors several years ago ( 3). In recent years, much effort has been made to identify genetic alterations in PDTC. Most of the studies have been focused particularly on identifying genetic alterations in the MAPK and phosphatidylinositol 3-kinase (PI3K)/Akt pathways, two major signaling pathways that have been extensively studied for their fundamental roles in thyroid tumorigenesis ( 4, 5). Examples of these genetic alterations include the BRAF mutation and RET/PTC rearrangements in the former pathway and Ras mutations in the latter pathway. Less studied genetic alterations include PAX8/PPAR? rearrangement, f-catenin mutation, and a few others. A somewhat disturbing issue regarding the actual role of these genetic alterations in PDTC is the large variation of their prevalences and types in PDTC reported by different investigators. A possible reason for this is that, unlike PTC, FTC, and ATC, the diagnostic criteria used for PDTC varied considerably among different investigators. This may not be surprising because PDTC or PDTC-like tumors may display an intermediate spectrum of clinicopathological behaviors between differentiated and undifferentiated thyroid carcinomas. It is often, therefore, not a straightforward task to clearly define PDTC based on clinicopathological grounds, particularly when the classical WHO criteria are not uniformly followed. It is also likely that ..