Browsing by Subject "Peptide Fragments"
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Item Characterizing c-Myc Dependent Lung Cancers(2015-07-27) Dospoy, Patrick; Scaglioni, Pier Paolo; Shay, Jerry W.; White, Michael A.; Minna, John D.MYC is one of the most commonly deregulated oncogenes in human cancer, including breast, colorectal and lung. While mutations in myc are rare, MYC is overexpressed and in some cases amplified in these (and other) cancers. Recent reports demonstrate the utility of various drugs in selectively targeting MYC-driven cancers. However, given the lack of consistency across tissue types, particularly lung cancer, a multimodal approach to delineate MYC-dependent lung cancers is required. My goal is to characterize MYC deregulation in lung cancer, investigate the degree of differential dependence on MYC in lung cancer, and to elucidate the mechanism for resistance to MYC inhibition. A large panel of clinically and molecularly annotated NSCLC lines was investigated for MYC mRNA, protein expression, and DNA copy number. In addition, publically available databases were interrogated to characterize the degree of MYC deregulation in lung cancer. Functional tests were performed on a large panel of NSCLC cell lines (n = 83) using four drugs that were recently shown to selectively target MYC-driven cancers. Further, we utilized the dominant negative mini-protein OMOMYC for functional classification. In all cases, drug effects were monitored by colony forming efficiency (CFE) assays. OMOMYC results were confirmed via xenograft experiments. Each of the four MYC inhibitors tested elicited a variable response in a subset of the 83 NSCLC cell lines, though the sensitive subset was not similar between any two drugs (highest correlation coefficient of 0.24). In order to determine which, if any, of the drugs targeted MYC-driven lung cancers, we stably expressed OMOMYC in a subset of the NSCLC cell line panel and performed functional assays. Most of the cell lines were sensitive to OMOMYC (with up to 100 fold reduction in CFE), compared to 3/8 that were totally resistant. The variability in the presence of OMOMYC showed a significant correlation with one of the four MYC inhibitors tested. These results support the idea that this sensitive subset represents a truly MYC-dependent class of lung cancers. Surprisingly, there was no correlation between MYC dependence and either MYC mRNA, protein expression or DNA copy number. OMOMYC levels were normalized in all cell lines tested and quantified using qRT-PCR. Additionally, in all cases, exogenous OMOMYC expression led to down regulation of MYC target genes as measured by both qRT-PCR and microarray. These data could be interpreted to suggest that the observed phenotype was the result of decreased MYC activity. Last, the NSCLC probed with OMOMYC showed a variable response in the Wnt pathway, with some cell lines showing a dramatic activation of the Wnt pathway upon OMOMYC induction. This activation proved to be functionally important, as dual inhibition of β-catenin and MYC proved more effective than either approach alone. To investigate the clinical significance of this approach, a subset of the original panel of NSCLC (n = 15) was screened with the MYC inhibitor 10058-F4, Wnt inhibitor Wnt-C59, or a combination of both drugs. Here, 8/15 cell lines displayed a statistically significant increase in sensitivity to MYC inhibition when Wnt pathway inhibition was added. We conclude: there is a subset of NSCLCs that demonstrates dramatic growth inhibition by a single MYC-inhibitor, and these data are phenocopied by the more specific MYC-dominant negative protein, OMOMYC. We further conclude that activation of the Wnt pathway serves as a compensatory response in some cell lines that confers resistance to MYC inhibition. In conclusion, simultaneously targeting MYC and the Wnt pathway elicits superior sensitivity in a subset of NSCLCs, and thus provides rationale for a combinatorial approach in a subset of lung cancer patients.Item Donald W. Seldin, M.D., Research Symposium finalist presentations(2023-05-05) Eleazu, Ijeoma; Ramos, Lisandro Maya; Salcedo Betancourt, Juan; Singh, Sumitabh; Smith, AaronThis edition of the UT Southwestern Internal Medicine Grand Rounds features presentations by the six Foster Fellows selected as finalists from the Eighth Annual Donald W. Seldin, M.D. Research Symposium, which was held on April 28, 2023. These Foster Fellows presented work that spanned the breadth and depth of scholarly activity across the department, and at the close of Grand Rounds, one will be selected as the 2023 Seldin Scholar, in honor of Dr. Donald W. Seldin. The Grand Rounds presentation includes additional award presentations recognizing Clinical Vignettes, as well as the Award for Research in Quality of Care and Education at Parkland Hospital, the Social Impact Award, and the Award for Basic Science (non-GME).Item Role of NT-proBNP in Late-Onset Anthracycline-Induced Cardiotoxicity Screening in Adult Survivors of Pediatric Cancer(2018-01-23) Cullinan, Kylie; Orlino, Angela; Bowers, Daniel; Reisch, JoanPURPOSE: Anthracyclines are chemotherapeutic agents with well-characterized cardiotoxic effects that can occur years after treatment. Current screening techniques in the cancer survivorship population are centered upon noninvasive cardiac imaging; however, this is effective in identifying cardiomyopathy only after significant remodeling has occurred. This study is a continuation of efforts to identify early biomarkers, such as NT-proBNP, and characteristics of adult survivors of pediatric cancer at increased risk of progression to non-ischemic cardiomyopathy (NICM). METHODS: In this retrospective chart review, data was collected for 190 patients at the UT Southwestern After Cancer Experience clinic over the duration of their follow-up care (mean, 4.1 patient yrs, mean of 15 yrs after chemotherapy completion). Patient groups were determined based on absence of NICM (group 1, n=118), those who developed NICM during observation (group 2, n=16), and patients with pre-existing NICM (group 3, n=56). NICM was defined as ejection fraction (EF) <55%. These groups were compared based on demographic data, cardiovascular risk factors, maximum recorded NT-proBNP, and ΔEF ((Max EFMin EF )/ Max EF). Multivariate regression analysis for ΔEF was performed. RESULTS: Patients with established NICM were found to have a significantly younger age at diagnosis, greater time from chemotherapy completion, and larger cumulative anthracycline dosage (CAD) as compared to those without NICM (p=0.022, p=0.006, p=0.006). Mean greatest NT-proBNP was 69.4 ng/mL, 206.2 ng/mL, and 302.2 ng/mL for groups 1,2, and 3 respectively. Though group 3 was significantly elevated from group 1 (p=0.043), those who developed NICM (group 2) did not significantly vary from either subgroup. Group 2 did have a significantly elevated ΔEF as compared to group 1 and 3 (p <0.002). Regression analysis of ΔEF yielded 4 variables with limited predictive value (R2=0.35) with NT-proBNP most heavily weighted (partial R2= 0.23). CONCLUSIONS: NT-proBNP was not clearly implicated in early identification of patients at increased risk of progression to NICM. Traditional cardiovascular risk factors, such as HTN, elevated cholesterol, or low HDL were not supported as predictive measures as well. Further prospective data with a larger cohort would be beneficial in clarify the distinguishing characteristics of cancer survivors at elevated risk of developing late-onset NICM.Item Soluble Peptide Treatment Reverses CD8 T Cell-Induced Disease in a Mouse Model of Spontaneous Tissue-Selective Autoimmunity(2011-10-25) Paek, So Yeon; Katz, Stephen I.Autoimmunity is a complex process that involves recognition of self antigens by autoreactive T cells or tissue targeting by autoantibodies produced by B cells. Specific molecular targets have been identified in several autoimmune diseases but remain unknown in many others. Transgenic (Tg) mice have been utilized to express model antigens that can be recognized by T cells or by autoantibodies. To identify mechanisms by which CD8+ autoreactive T cells cause inflammation, we generated a double transgenic (DTg) murine model of autoimmunity by crossing K14-sOVA mice, which express soluble chicken ovalbumin (OVA), with OT-1 mice, whose CD8 T cells express V2/V5 regions of the T cell receptor that are specific for SIINFEKL peptide (OVA 257-264) in association with class I MHC molecules. The K14-SOVA/OT-1 (#5 and #17) DTg mice develop normally, except that they undergo a destructive process that selectively targets the external pinnae in the first 6 days of life. The purpose of this study was to elucidate the mechanism and attempt to obviate the resulting tissue-specific destruction. By light microscopy, the ear bud area displayed an intense inflammatory infiltrate of V2/V5+CD8+ OT-1 cells when characterized by FACS. Administration of the TCR-recognized SIINFEKL peptide i.v. to pregnant F1 mice on days E16 and E18 in utero and i.p. to newborn pups on days 2 and 4 prevented the inflammatory response and resulted in development of normal-looking ears in 100% of pups. Treatment with the SIINFEKL peptide was shown to down-regulate the CD8 coreceptor and activate T-cells to differentiate into memory T-cells. This model can inform us about mechanisms of peripheral tolerance and potential therapies for autoimmune diseases in which specific molecular targets are known.Item Utility of traditional cardiac biomarkers in patients with CKD(2014-10-31) Hedayati, Susan