GLI2-dependent c-MYC upregulation mediates resistance of pancreatic cancer cells to the BET bromodomain inhibitor JQ1.

JQ1 and I-BET151 are selective inhibitors of BET bromodomain proteins that have efficacy against a number of different cancers. Since the effectiveness of targeted therapies is often limited by development of resistance, we examined whether it was possible for cancer cells to develop resistance to the BET inhibitor JQ1. Here we show that pancreatic cancer cells developing resistance to JQ1 demonstrate cross-resistance to I-BET151 and insensitivity to BRD4 downregulation. The resistant cells maintain expression of c-MYC, increase expression of JQ1-target genes FOSL1 and HMGA2, and demonstrate evidence of epithelial-mesenchymal transition (EMT). However, reverting EMT fails to sensitize the resistant cells to JQ1 treatment. Importantly, the JQ1-resistant cells remain dependent on c-MYC that now becomes co-regulated by high levels of GLI2. Furthermore, downregulating GLI2 re-sensitizes the resistant cells to JQ1. Overall, these results identify a mechanism by which cancer cells develop resistance to BET inhibitors.

Snail cooperates with Kras G12D in vivo to increase stem cell factor and enhance mast cell infiltration.

UNLABELLED: Pancreatic ductal adenocarcinoma (PDAC) is associated with a pronounced fibro-inflammatory stromal reaction that contributes to tumor progression. A critical step in invasion and metastasis is the epithelial-to-mesenchymal transition (EMT), which can be regulated by the Snail family of transcription factors. Overexpression of Snail (Snai1) and mutant Kras(G12D) in the pancreas of transgenic mice, using an elastase (EL) promoter, resulted in fibrosis. To identify how Snail modulates inflammation in the pancreas, we examined the effect of expressing Snail in EL-Kras(G12D) mice (Kras(G12D)/Snail) on mast cell infiltration, which has been linked to PDAC progression. Using this animal model system, it was demonstrated that there are increased numbers of mast cells in the pancreas of Kras(G12D)/Snail mice compared with control Kras(G12D) mice. In addition, it was revealed that human primary PDAC tumors with increased Snail expression are associated with increased mast cell infiltration, and that Snail expression in these clinical specimens positively correlated with the expression of stem cell factor (SCF/KITLG), a cytokine known to regulate mast cell migration. Concomitantly, SCF levels are increased in the Kras(G12D)/Snail mice than in control mice. Moreover, overexpression of Snail in PDAC cells increased SCF levels, and the media conditioned by Snail-expressing PDAC cells promoted mast cell migration. Finally, inhibition of SCF using a neutralizing antibody significantly attenuated Snail-induced migration of mast cells. IMPLICATIONS: Together, these results elucidate how the EMT regulator Snail contributes to inflammation associated with PDAC tumors.

BET bromodomain inhibitors block growth of pancreatic cancer cells in three-dimensional collagen.

Pancreatic ductal adenocarcinoma (PDAC) is associated with pronounced fibrosis that contributes to chemoresistance, in part, through increased histone acetylation. Because bromodomain (BRD) and extra terminal domain (BET) proteins are "readers" of histone acetylation marks, we targeted BET proteins in PDAC cells grown in three-dimensional collagen. We show that treatment with BET inhibitors decreases growth of PDAC cells (AsPC1, CD18, and Panc1) in collagen. Transfection with siRNA against BRD4, which is increased in human PDAC tumors, also decreases growth of PDAC cells. BET inhibitors additionally decrease growth in collagen of PDAC cells that have undergone epithelial-to-mesenchymal transition or have become resistant to chemotherapy. Although BET inhibitors and BRD4 siRNA repress c-MYC only in AsPC1 and CD18 cells, downregulating c-MYC decreases growth of all three PDAC cell lines in collagen. FOSL1, which is also targeted by BET inhibitors and BRD4 siRNA in AsPC1, CD18, and Panc1 cells, additionally regulates growth of all three PDAC cell lines in collagen. BET inhibitors and BRD4 siRNA repress HMGA2, an architectural protein that modulates chromatin state and also contributes to chemoresistance, in PDAC cells grown in collagen. Importantly, we show that there is a statistically significant correlation between BRD4 and HMGA2 in human PDAC tumors. Significantly, overexpression of HMGA2 partially mitigates the effect of BET inhibitors on growth and c-MYC and/or FOSL1 expression in collagen. Overall, these results demonstrate that BET inhibitors block growth of PDAC cells in collagen and that BET proteins may be potential targets for the treatment of pancreatic cancer.

Gram-negative bacterial endocarditis in adults: state-of-the-heart.

Gram-negative endocarditis due to HACEK bacteria (Haemophilus species, Actinobacillus, Cardiobacterium, Eikenella and Kingella species) and non-HACEK organisms is an infrequent occurrence but is associated with significant morbidity and mortality. Traditionally, non-HACEK Gram-negative endocarditis has been associated with injection drug use. However, emerging data from more contemporary cohorts suggest changing epidemiology and risk factors for Gram-negative endocarditis, necessitating an updated review of this subject. Moreover, optimal management, including the need for surgical intervention, and strategies for the prevention of Gram-negative endocarditis need to be revisited.

Contemporary management of cardiovascular implantable electronic device infections.

Cardiovascular implantable electronic device (CIED) implantation rate has substantially risen in the foregoing decades. Unfortunately, this upsurge in CIED implantation rate has been accompanied by a disproportionate rise in the rate of CIED infections. Device infection is a major complication of CIED implantation, necessitating removal of an infected device followed by systemic antimicrobial therapy and reimplantation of a new system. In this article, we review the current epidemiology, risk factors, diagnostic strategy and contemporary management of CIED infection. In addition, we address the vexing question of how to best manage patients with Staphylococcus aureus bacteremia, in the setting of an implanted device, but no overt clinical signs of CIED infection. Lastly, we discuss the preventive strategies to minimize risk of CIED infection.

Smoking and inflammatory bowel disease: trends in familial and sporadic cohorts.

BACKGROUND: Ulcerative colitis (UC) and Crohn's disease (CD) result from genetic and environmental factors. Never smoking and formerly smoking increase the risk of UC, whereas smoking exacerbates the course of CD. We sought to define the age-dependent effects of smoking on the development of UC and CD in familial and sporadic cohorts. METHODS: University of Chicago patients diagnosed with UC or CD between 1990 and 2002 were surveyed about their tobacco use relative to their diagnosis. Smoking trends were used to estimate age-dependent odds ratios and the attributable risks of smoking in the IBD cohort compared to in the general population. RESULTS: One thousands and thirteen patients were included in the study: 245 with sporadic UC; 216 with sporadic CD; 249 with familial UC; and 303 with familial CD. Being an ex-smoker conferred an increased risk for UC in the 25-44 age group in both the sporadic and familial cohorts, but not in the 45-64 age group in the familial UC cohort. Furthermore, there was no difference in tobacco use between patients with sporadic CD and the general population, although there was a significant increase in smoking in younger patients with familial CD. CONCLUSIONS: Ex-smokers make up an increasing percentage of older patients diagnosed with UC, accounting for more than 35% of the attributable risk of late onset (>45 years) UC and a large component of the second peak in diagnosis. Current smokers account for a large percentage of patients diagnosed at a younger age with familial CD but not with sporadic CD. Families with IBD should be counseled that early tobacco use significantly increases the risk of developing CD or, if an ex-smoker, UC at a young age.