Genetic Study of Elf5 and Ehf in the Mouse Salivary Gland

Salivary gland (SG) development, maturation, and homeostasis require coordinated roles of transcription factors (TFs) that dictate specific cell identities and fate. The ETS family of proteins are important transcriptional drivers of diverse cell lineages, tissue development, and differentiation programs and hence are also likely to play an important role in the SG. Here we have leveraged genomic and epigenomic data of the SG to examine the expression profile of ETS genes and identified 2 closely related paralogs, Elf5 and Ehf, that are highly expressed in distinct epithelial subpopulations. By using a well-defined mouse knockout model of Elf5, we show that Elf5, despite its enriched expression in the acinar cells, is functionally dispensable for maintaining the homeostatic state of the adult SG epithelium. The lack of a discernible phenotype of the Elf5-null SG might be due to possible functional redundancy with Ehf or other ETS factors. To probe this possibility and to examine the specific consequences of Ehf loss in the SG, we used CRISPR-Cas9 to generate mice in which the DNA-binding ETS domain of Ehf is disrupted due to an insertion mutation. We demonstrate that the Ehf mutant (EhfMut) mice exhibit a distinct cellular phenotype with decreased granular convoluted tubules that are accompanied by an increased accumulation of the intercalated Sox9-positive ductal cell population. Interestingly, the ductal phenotype of the EhfMut animals is highly pronounced in males, reaffirming the established sexual dimorphism of the SG that exists in rodents. Our results show that unlike Elf5, Ehf plays a nonredundant role in directing ductal cell differentiation of the SG and highlights the phenotypic subtlety in mutant mice of closely related TFs and the importance of careful consideration of cell type-specific studies.

Transcriptomic and Single-Cell Analysis of the Murine Parotid Gland

The salivary complex of mammals consists of 3 major pairs of glands: the parotid, submandibular, and sublingual glands. While the 3 glands share similar functional properties, such as saliva secretion, their differences are largely based on the types of secretions they produce. While recent studies have begun to shed light on the underlying molecular differences among the glands, few have examined the global transcriptional repertoire over various stages of gland maturation. To better elucidate the molecular nature of the parotid gland, we have performed RNA sequencing to generate comprehensive and global gene expression profiles of this gland at different stages of maturation. Our transcriptomic characterization and hierarchical clustering analysis with adult organ RNA sequencing data sets has identified a number of molecular players and pathways that are relevant for parotid gland biology. Moreover, our detailed analysis has revealed a unique parotid gland-specific gene signature that may represent important players that could impart parotid gland-specific biological properties. To complement our transcriptomic studies, we have performed single-cell RNA sequencing to map the transcriptomes of parotid epithelial cells. Interrogation of the single-cell transcriptomes revealed the degree of molecular and cellular heterogeneity of the various epithelial cell types within the parotid gland. Moreover, we uncovered a mixed-lineage population of cells that may reflect molecular priming of differentiation potentials. Overall our comprehensive studies provide a powerful tool for the discovery of novel molecular players important in parotid gland biology.

Abstract 659: Overexpression of TPX2 accelerates cell cycle progression in melanoma and is an indicator of response to Aurora A kinase inhibitors

There is a tremendous need to identify more effective treatments for metastatic melanoma. In order to detect genetic changes in melanoma that might facilitate the development of novel therapies, we performed aCGH in melanoma cell lines and tumors and identified that Targeting Protein for Xklp2 (TPX2) was the most commonly amplified gene on 20q11.21, a region of frequent gain. Gene expression profiling studies also demonstrated overexpression of TPX2, suggesting a previously unknown role in the development of melanoma. TPX2 is a microtubule-associated protein that regulates bipolar spindle assembly and centrosome replication; the TPX2 - Aurora A interaction is essential for accurate segregation of chromosome and mitosis progression. We evaluated a potential role for TPX2 overexpression in melanoma using TPX2 overexpressing melanoma cell lines as a model. TPX2 overexpressing cell lines display accelerated cell cycle progression, increased CDK1/CDK2 activity, cyclin A/B1 levels, and constitutive activation and overexpression of Aurora A. We depleted TPX2 using shRNA to further dissect its role in melanoma. In unsynchronized cells, TPX2 depletion causes prolonged mitotic arrest accompanied by persistent activation of the spindle-assembly checkpoint (SAC) and caspase-3, and subsequent caspase-dependent cell death. In contrast, with G1/S synchronization, TPX2 depletion decreases S phase entry and delays S-G2-M phase transition followed by marked cell death. Accordingly, TPX2 depletion was associated with decreased CDK1 activity but not CDK2 activity, and activation of caspase and low activation of the SAC. Our data demonstrate that TPX2 overexpression is required for increased CDK1-cyclinB1 activity, thus accelerating cell cycle progression. Accordingly, TPX2-overexpressing melanoma cell lines are dependent on TPX2 for proliferation, whereas non-overexpressing cell lines and melanocytes are not. Additionally, TPX2-overexpressing cell lines are 3-10 time more sensitive to an Aurora A kinase inhibitor (VX680) than non-overexpressing cell line, suggesting that TPX2-activating Aurora A kinase could become a novel therapeutic target for treatment of melanoma with highly expressed TPX2, Finally, TPX2-IHC staining demonstrated that a significantly increased expression of TPX2 in primary and metastatic melanoma as compared to begin nevi, suggesting it is a marker of progression. Thus, we have identified TPX2 as a novel gene upregulated in melanoma. Overexpression of TPX2 may be a marker of tumors sensitive to Aurora A inhibitors allowing patient stratification for optimal therapeutic selection.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 659.

The treatment of advanced renal cell cancer with high-dose oral thalidomide

Thalidomide is reported to suppress levels of several cytokines, angiogenic and growth factors including TNF-alpha, basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6). The resulting anti-angiogenic, immunomodulatory and growth suppressive effects form the rationale for investigating thalidomide in the treatment of malignancies. We have evaluated the use of high-dose oral thalidomide (600 mg daily) in patients with renal carcinoma. 25 patients (all men; median age, 51 years; range 34-76 years) with advanced measurable renal carcinoma, who had either progressed on or were not suitable for immunotherapy, received thalidomide in an escalating schedule up to a maximum dose of 600 mg daily. Treatment continued until disease progression or unacceptable toxicity were encountered. 22 patients were assessable for response. 2 patients showed partial responses (9%; 95% CI: 1-29), 7 (32%; 95% CI: 14-55) had stable disease for more than 6 months and a further 5 (23%; 95% CI: 8-45) had stable disease for between 3 and 6 months. We also measured levels of TNF-alpha, bFGF, VEGF, IL-6 and IL-12 before and during treatment. In patients with SD > or = 3 months or an objective response, a statistically significant decrease in serum TNF-alpha levels was demonstrated (P = 0.05). The commonest toxicities were lethargy (> or = grade II, 10 patients), constipation (> or = grade II, 11 patients) and neuropathy (> or = grade II, 5 patients). Toxicities were of sufficient clinical significance for use of a lower and well tolerated dose of 400 mg in currently accruing studies.

The involvement of p38 mitogen-activated protein kinase in the alpha-melanocyte stimulating hormone (alpha-MSH)-induced melanogenic and anti-proliferative effects in B16 murine melanoma cells

Activation of p38 or p44/42 mitogen-activated protein (MAP) kinases has been shown to trigger differentiation in a number of cell types. The present study has investigated the roles of these kinases in the alpha-melanocyte stimulating hormone (alpha-MSH)-induced melanogenic and proliferative responses in B16 melanoma cells. Treatment of cells with alpha-MSH led to the time-dependent phosphorylation of both p38 and p44/42 MAP kinases. However, only inhibition of p38 MAP kinase activity with SB 203580 blocked both the alpha-MSH-induced melanogenic and anti-proliferative effects. It therefore appears that activation of the p38 pathway can promote melanogenesis and inhibit growth of B16 melanoma cells.

Operative venodilation: a previously unsuspected factor in the cause of postoperative deep vein thrombosis

Intraoperative venodilation in veins distant from the site of operation has been shown to occur in animals and has been directly correlated with focal venous endothelial damage. This exposure of subendothelial collagen could serve as initiation sites for thrombus formation. This study tests the hypothesis that human beings (1) significant operative venodilation occurs and that it correlates with postoperative deep venous thrombosis (DVT); (2) operative venodilation can be pharmacologically controlled; and (3) this control reduces the incidence of postoperative DVT. Twenty-one patients undergoing total hip replacement had their contralateral cephalic vein continuously monitored with modified ultrasonographic instrumentation, with a continuous on-line recorder graphing venous diameter. Patients were randomly assigned to receive 0.5 mg of dihydroergotamine and 5000 U of heparin (DHE/Hep) for prophylaxis or placebo, with investigators "blinded" Postoperatively, all patients underwent ascending phlebography. Patients in whom postoperative DVT developed (11) had a mean operative venodilation of 28.9% +/- 3.93%, and those in whom DVT did not develop (10) had a mean venodilation of 11.6% +/- 1.55% (p = 0.001). Only 17% (2/12) dilating less than 20% baseline diameter had DVT compared with 100% (9/9) dilating greater than 20% of baseline diameter (p = 0.002). Patients receiving venotonic agent DHE had significantly less venodilation and DVT (p less than 0.001) compared with patients receiving the placebo. Patients who had DVT and whose veins dilated greater than 20% were older than patients who did not have DVT and whose veins minimally dilated: p = 0.04 and p = 0.07, respectively. Although there was a trend toward increased venoconstriction in patients receiving DHE/Hep (p = 0.09), there was no correlation of venoconstriction with ultimate thrombotic outcome. Maximal venodilation occurs during handling of soft tissue (muscle), and this occurs significantly sooner than maximal venoconstriction, which occurs during bone manipulation. We conclude that excessive operative venodilation is a new and important etiologic factor that leads to postoperative DVT. Operative venodilation can be pharmacologically controlled with the venotonic agent DHE. The combination DHE/Hep reduces postoperative DVT by the reduction of operative venodilation in the presence of low doses of an anticoagulant. These findings offer a new approach for predicting postoperative DVT and an object rationale for developing effective prophylaxis.