p53 constrains progression to anaplastic thyroid carcinoma in a Braf-mutant mouse model of papillary thyroid cancer

Anaplastic thyroid carcinoma (ATC) has among the worst prognoses of any solid malignancy. The low incidence of the disease has in part precluded systematic clinical trials and tissue collection, and there has been little progress in developing effective therapies. v-raf murine sarcoma viral oncogene homolog B (BRAF) and tumor protein p53 (TP53) mutations cooccur in a high proportion of ATCs, particularly those associated with a precursor papillary thyroid carcinoma (PTC). To develop an adult-onset model of BRAF-mutant ATC, we generated a thyroid-specific CreER transgenic mouse. We used a Cre-regulated Braf^V600E mouse and a conditional Trp53 allelic series to demonstrate that p53 constrains progression from PTC to ATC. Gene expression and immunohistochemical analyses of murine tumors identified the cardinal features of human ATC including loss of differentiation, local invasion, distant metastasis, and rapid lethality. We used small-animal ultrasound imaging to monitor autochthonous tumors and showed that treatment with the selective BRAF inhibitor PLX4720 improved survival but did not lead to tumor regression or suppress signaling through the MAPK pathway. The combination of PLX4720 and the mapk/Erk kinase (MEK) inhibitor PD0325901 more completely suppressed MAPK pathway activation in mouse and human ATC cell lines and improved the structural response and survival of ATC-bearing animals. This model expands the limited repertoire of autochthonous models of clinically aggressive thyroid cancer, and these data suggest that small-molecule MAPK pathway inhibitors hold clinical promise in the treatment of advanced thyroid carcinoma.Mutations in the v-raf murine sarcoma viral oncogene homolog B (BRAF) kinase occur in ∼60% of papillary thyroid carcinomas (PTCs) (www.cbioportal.org/public-portal/data_sets.jsp). PTC generally exhibits an excellent prognosis with conventional therapy, including surgery and selective use of radioiodine (1). PTC may progress to clinically aggressive forms of thyroid cancer, including poorly differentiated thyroid carcinoma (PDTC), which exhibits more rapid growth and poorer clinical outcome. Less commonly, PTC progresses to undifferentiated (anaplastic) thyroid carcinoma (ATC) that is associated with a grim prognosis with a median survival of 5 mo and a 1-y survival of only 20% (2).Focused sequencing of clinically aggressive subsets of thyroid cancers including PDTC and ATC suggests acquired cooperating mutations drive thyroid cancer progression (3, 4). Mutations in tumor protein p53 (TP53) occur with increasing frequency in more aggressive forms of thyroid cancer, culminating in ATC, which harbors the highest frequency of TP53 mutations (5–7). ATC may progress from well-differentiated thyroid carcinomas and is also believed to arise spontaneously, possibly from clinically undetectable microscopic well-differentiated thyroid tumors. In the former scenario, ATCs frequently harbor mutations in BRAF, and these mutations are concordant between the anaplastic and papillary components. This implicates BRAF mutation as an initiating somatic genetic event and supports the hypothesis that loss of p53 function is important for progression to ATC (3, 8).Mouse models of thyroid cancer have supported the model of acquired mutations driving tumor progression. Although each study has technical limitations, including embryonic oncogene expression and/or elevated circulating thyroid-stimulating hormone (TSH) levels, this work generally supports the notion that BRAF^T1799A is sufficient to initiate PTC (9–12). In addition, deletion of p53 enabled tumor progression to high-grade thyroid carcinomas in a transgenic mouse model of translocations targeting the ret proto-oncogene (RET/PTC) driven PTC, and a model of follicular thyroid carcinoma initiated by tissue-specific phosphatase and tensin homolog (Pten) deletion (13, 14). These studies provide functional evidence of an important tumor suppressive role for p53 during thyroid carcinoma progression, although to date this has not been tested in models of BRAF-mutant PTC.Given the high frequency of BRAF and RAS mutations in thyroid carcinomas and the success of targeted therapy trials for advanced thyroid cancers, the potential utility of small-molecule inhibitors of the MAPK pathway has garnered much recent attention (15). These drugs have also been studied in models of BRAF-mutant thyroid carcinoma. Initial observations using a thyroid-specific doxycycline-inducible BRAF^T1799A allele suggested that BRAF or mapk/Erk kinase (MEK) inhibition induced thyroid carcinoma regression and differentiation (9). However, a recent study from the same laboratory showed a mitigated response to BRAF (PLX4032, vemurafenib) inhibition in human papillary and ATC cell lines and in an endogenous Braf^V600E-driven PTC mouse model. In response to PLX4032/vemurafenib, feedback inhibition of the human epidermal growth factor receptor 3 (HER3) receptor tyrosine kinase was abrogated, leading to reactivation of MAPK signaling (16). In addition, responses in patients treated with the BRAF inhibitor vemurafenib have exhibited modest activity (17).To develop an adult-onset autochthonous model of clinically aggressive thyroid carcinoma, we generate a thyroid-specific CreER transgenic mouse and use conditional Braf^T1799A and Trp53 alleles. We demonstrate that expression of BRAF^V600E is sufficient to initiate tumorigenesis in adult animals, and p53 loss enables progression to bona fide ATC recapitulating the cardinal features of the human disease including intrinsic resistance to BRAF inhibitors.     

Daily Mean Temperature and Clinical Kidney Stone Presentation in Five U.S. Metropolitan Areas: A Time-Series Analysis

Background: High ambient temperatures are a risk factor for nephrolithiasis, but the precise relationship between temperature and kidney stone presentation is unknown.Objectives: Our objective was to estimate associations between mean daily temperature and kidney stone presentation according to lag time and temperatures.Methods: Using a time-series design and distributed lag nonlinear models, we estimated the relative risk (RR) of kidney stone presentation associated with mean daily temperatures, including cumulative RR for a 20-day period, and RR for individual daily lags through 20 days. Our analysis used data from the MarketScan Commercial Claims database for 60,433 patients who sought medical evaluation or treatment of kidney stones from 2005–2011 in the U.S. cities of Atlanta, Georgia; Chicago, Illinois; Dallas, Texas; Los Angeles, California; and Philadelphia, Pennsylvania.Results: Associations between mean daily temperature and kidney stone presentation were not monotonic, and there was variation in the exposure–response curve shapes and the strength of associations at different temperatures. However, in most cases RRs increased for temperatures above the reference value of 10°C. The cumulative RR for a daily mean temperature of 30°C versus 10°C was 1.38 in Atlanta (95% CI: 1.07, 1.79), 1.37 in Chicago (95% CI: 1.07, 1.76), 1.36 in Dallas (95% CI: 1.10, 1.69), 1.11 in Los Angeles (95% CI: 0.73, 1.68), and 1.47 in Philadelphia (95% CI: 1.00, 2.17). Kidney stone presentations also were positively associated with temperatures < 2°C in Atlanta, and < 10°C in Chicago and Philadelphia. In four cities, the strongest association between kidney stone presentation and a daily mean temperature of 30°C versus 10°C was estimated for lags of ≤ 3 days.Conclusions: In general, kidney stone presentations increased with higher daily mean temperatures, with the strongest associations estimated for lags of only a few days. These findings further support an adverse effect of high temperatures on nephrolithiasis.Citation: Tasian GE, Pulido JE, Gasparrini A, Saigal CS, Horton BP, Landis JR, Madison R, Keren R, for the Urologic Diseases in America Project. 2014. Daily mean temperature and clinical kidney stone presentation in five U.S. metropolitan areas: a time-series analysis. Environ Health Perspect 122:1081–1087; http://dx.doi.org/10.1289/ehp.1307703     

Covarying alterations in Aβ deposition,glucose metabolism,and gray matter volume in cognitively normal elderly

β‐Amyloid (Aβ), a feature of Alzheimer's disease (AD) pathology, may precede reduced glucose metabolism and gray matter (GM) volume and cognitive decline in patients with AD. Accumulation of Aβ, however, has been also reported in cognitively intact older people, although it remains unresolved whether and how Aβ deposition, glucose metabolism, and GM volume relate to one another in cognitively normal elderly. Fifty‐two cognitively normal older adults underwent Pittsburgh Compound B–positron emission tomography (PIB‐PET), [¹⁸F]fluorodeoxyglucose‐PET, and structural magnetic resonance imaging to measure whole‐brain amyloid deposition, glucose metabolism, and GM volume, respectively. Covariance patterns of these measures in association with global amyloid burden measured by PIB index were extracted using principal component analysis–based multivariate methods. Higher global amyloid burden was associated with relative increases of amyloid deposition and glucose metabolism and relative decreases of GM volume in brain regions collectively known as the default mode network including the posterior cingulate/precuneus, lateral parietal cortices, and medial frontal cortex. Relative increases of amyloid deposition and glucose metabolism were also noted in the lateral prefrontal cortices, and relative decreases of GM volume were pronounced in hippocampus. The degree of expression of the topographical patterns of the PIB data was further associated with visual memory performance when controlling for age, sex, and education. The present findings suggest that cognitively normal older adults with greater amyloid deposition are relatively hypermetabolic in frontal and parietal brain regions while undergoing GM volume loss in overlapping brain regions. Hum Brain Mapp 35:297–308, 2014. © 2012 Wiley Periodicals, Inc.     

Genetic Privacy,Disease Prevention,and the Principle of Rescue

Suppose that you have deeply personal information that you do not want to share. Further suppose that this information could help others, perhaps even saving their lives. Should you reveal the information or keep it secret? With the increasing prevalence of genetic testing, more and more people are finding themselves in this situation. Although a patient's genetic results are potentially relevant to all her biological family members, her first‐degree relatives—parents, children, and full siblings—are most likely to be affected. This is especially true for genetic mutations—like those in the BRCA1 and BRCA2 genes—that are associated with a dramatically increased risk of disease. Fortunately, people are usually willing to share results with their at‐risk relatives. Occasionally, however, a patient refuses to disclose her findings to anyone outside her clinical team. Ethicists have written little on patients’ moral duties to their at‐risk relatives. Moreover, the few accounts that have been advanced are problematic. Some unnecessarily expose patients’ genetic information to relatives who are unlikely to benefit from it, and others fail to ensure that patients’ most vulnerable relatives are informed of their genetic risks. Patients’ duty to warn can be defended in a way that avoids these problems. I argue that the duty to share one's genetic results is grounded in the principle of rescue—the idea that one ought to prevent, reduce, or mitigate the risk of harm to another person when the expected harm is serious and the cost or risk to oneself is sufficiently moderate. When these two criteria are satisfied, a patient will most likely have a duty to warn.     

Minimal Disease in the Sentinel Lymph Node: How to Best Measure Sentinel Node Micrometastases to Predict Risk of Additional Non-Sentinel Lymph Node Disease

Background  

Volume of disease in the sentinel lymph node (SLN) is a significant predictor of additional nodal metastasis. This study assesses incidence of residual non-SLN disease in a large cohort of women with minimal SLN metastases and compares three methods of SLN micrometastasis volume measurement to determine which best predicts residual disease on completion axillary lymph node dissection (cALND).