Jason Powell

Essential Requirement for PP2A Inhibition by the Oncogenic Receptor c-KIT Suggests PP2A Reactivation as a Strategy to Treat c-KIT+ Cancers

Oncogenic mutations of the receptor tyrosine kinase c-KIT play an important role in the pathogenesis of gastrointestinal stromal tumors, systemic mastocytosis, and some acute myeloid leukemias (AML). Although juxtamembrane mutations commonly detected in gastrointestinal stromal tumor are sensitive to tyrosine kinase inhibitors, the kinase domain mutations frequently encountered in systemic mastocytosis and AML confer resistance and are largely unresponsive to targeted inhibition by the existing agent imatinib. In this study, we show that myeloid cells expressing activated c-KIT mutants that are imatinib sensitive (V560G) or imatinib resistant (D816V) can inhibit the tumor suppressor activity of protein phosphatase 2A (PP2A). This effect was associated with the reduced expression of PP2A structural (A) and regulatory subunits (B55alpha, B56alpha, B56gamma, and B56delta). Overexpression of PP2A-Aalpha in D816V c-KIT cells induced apoptosis and inhibited proliferation. In addition, pharmacologic activation of PP2A by FTY720 reduced proliferation, inhibited clonogenic potential, and induced apoptosis of mutant c-KIT(+) cells, while having no effect on wild-type c-KIT cells or empty vector controls. FTY720 treatment caused the dephosphorylation of the D816V c-KIT receptor and its downstream signaling targets pAkt, pSTAT5, and pERK1/2. Additionally, in vivo administration of FTY720 delayed the growth of V560G and D816V c-KIT tumors, inhibited splenic and bone marrow infiltration, and prolonged survival. Our findings show that PP2A inhibition is essential for c-KIT-mediated tumorigenesis, and that reactivating PP2A may offer an attractive strategy to treat drug-resistant c-KIT(+) cancers.

An evidence-based review of peritonsillar abscess

Clin. Otolaryngol. 2012, 37, 136–145

Blocking cytokine signaling along with intense Bcr-Abl kinase inhibition induces apoptosis in primary CML progenitors

In chronic myeloid leukemia (CML) cell lines, brief exposure to pharmacologically relevant dasatinib concentrations results in apoptosis. In this study, we assess the impact of intensity and duration of Bcr-Abl kinase inhibition on primary CD34+ progenitors of chronic phase CML patients. As CML cells exposed to dasatinib in vivo are in a cytokine-rich environment, we also assessed the effect of cytokines (six growth factors cocktail or granulocyte-macrophage colony-stimulating factor (CSF) or granulocyte-CSF) in combination with dasatinib. In the presence of cytokines, short-term intense Bcr-Abl kinase inhibition (⩾90% p-Crkl inhibition) with 100u2009nM dasatinib did not reduce CD34+ colony-forming cells (CFCs). In contrast, without cytokines, short-term exposure to dasatinib reduced CML-CD34+ CFCs by 70–80%. When cytokines were added immediately after short-term exposure to dasatinib, CML-CD34+ cells remained viable, suggesting that oncogene dependence of these cells can be overcome by concomitant or subsequent exposure to cytokines. Additional inhibition of Janus tyrosine kinase (Jak) activity re-established the sensitivity of CML progenitors to intense Bcr-Abl kinase inhibition despite the presence of cytokines. These findings support the contention that therapeutic strategies combining intense Bcr-Abl kinase inhibition and blockade of cytokine signaling pathways can be effective for eradication of CML progenitors.

FBXO31 Is the Chromosome 16q24.3 Senescence Gene, a Candidate Breast Tumor Suppressor, and a Component of an SCF Complex

A BAC located in the 16q24.3 breast cancer loss of heterozygosity region was previously shown to restore cellular senescence when transferred into breast tumor cell lines. We have shown that FBXO31, although located just distal to this BAC, can induce cellular senescence in the breast cancer cell line MCF-7 and is the likely candidate senescence gene. FBXO31 has properties consistent with a tumor suppressor, because ectopic expression of FBXO31 in two breast cancer cell lines inhibited colony growth on plastic and inhibited cell proliferation in the MCF-7 cell line. In addition, compared with the relative expression in normal breast, levels of FBXO31 were down-regulated in breast tumor cell lines and primary tumors. FBXO31 was cell cycle regulated in the breast cell lines MCF-10A and SKBR3 with maximal expression from late G(2) to early G(1) phase. Ectopic expression of FBXO31 in the breast cancer cell line MDA-MB-468 resulted in the accumulation of cells at the G(1) phase of the cell cycle. FBXO31 contains an F-box domain and is associated with the proteins Skp1, Roc-1, and Cullin-1, suggesting that FBXO31 is a component of a SCF ubiquitination complex. We propose that FBXO31 functions as a tumor suppressor by generating SCF(FBXO31) complexes that target particular substrates, critical for the normal execution of the cell cycle, for ubiquitination and subsequent degradation.

Identification of ANKRD11 as a p53 coactivator

The ability of p53 to act as a transcription factor is critical for its function as a tumor suppressor. Ankyrin repeat domain 11, ANKRD11 (also known as ANR11 or ANCO1), was found to be a novel p53-interacting protein that enhanced the transcriptional activity of p53. ANKRD11 expression was shown to be downregulated in breast cancer cell lines. Restoration of ANKRD11 expression in MCF-7 (wild-type p53) and MDA-MB-468 (p53R273H mutant) cells suppressed their proliferative and clonogenic properties through enhancement of CDKN1A (p21waf1/CIP1) expression. ShRNA-mediated silencing of ANKRD11 expression reduced the ability of p53 to activate CDKN1A expression. ANKRD11 was shown to associate with the p53 acetyltransferases and cofactors, P/CAF and hADA3. Exogenous ANKRD11 expression enhanced the levels of acetylated p53 in both MCF-7 and MDA-MB-468 cells. ANKRD11 enhanced the DNA-binding properties of mutant p53R273H to the CDKN1A promoter, suggesting that ANKRD11 can mediate the restoration of normal p53 function in some cancer-related p53 mutations. In addition, ANKRD11 itself was found to be a novel p53 target gene. These findings demonstrate a role for ANKRD11 as a p53 coactivator and suggest the involvement of ANKRD11 in a regulatory feedback loop with p53.

A review of the pathogenesis of adult peritonsillar abscess: time for a re-evaluation

OBJECTIVESnTo perform a multifactorial exploration of the aetiology of peritonsillar abscess (PTA) in adults, in order to develop greater clinical understanding of the condition and improve management.nnnDESIGNnA literature review exploring key pathogens, predisposing host factors and current pathogenic hypotheses.nnnMETHODSnA PubMed search for articles published between January 1980 and January 2012 using the terms peritonsillar abscess AND microbiology, peritonsillar abscess AND pathophysiology and peritonsillar abscess AND etiology.nnnRESULTSnMajor pathogens in PTA are opportunistic microflora. Group A streptococcal PTA infections present differently from polymicrobial PTA. A number of host factors influence the conditions required for the pathogenesis of PTA.nnnCONCLUSIONSnPTA is clinically distinct from acute tonsillitis and occurs in people with a chronic underlying susceptibility. Targeting host factors, including oral hygiene, antibiotic use and smoking, may prevent PTA. Re-education of clinicians concerning the aetiology of PTA is necessary for appropriate disease management.

Mucosal changes in laryngopharyngeal reflux--prevalence, sensitivity, specificity and assessment.

A literature review regarding the use of laryngopharyngeal mucosal signs in diagnosing laryngopharyngeal reflux (LPR).Objectives/Hypothesis: nA literature review regarding the use of laryngopharyngeal mucosal signs in diagnosing laryngopharyngeal reflux (LPR). n nStudy Design: nLiterature review. n nMethods: nA search of MEDLINE in February 2012 using the terms laryngopharyngeal reflux, laryngitis, mucosa, appearances, and signs (English language only). n nResults: nOne or more laryngopharyngeal mucosal signs associated with LPR were identified in 64% to 93% of healthy volunteers (3% >5 signs) and in 17% to 85% of gastroesophageal reflux disease sufferers (Reflux Finding Score [RFS] >7 in 24%). Reinkes edema, pseudosulcus, ventricular obliteration, vocal cord nodules, and granulomas have in some, but not all studies, been shown to be more prevalent in those with pH-proven pharyngeal reflux. Pseudosulcus, interarytenoid thickening, and Reinkes edema were more prevalent in those symptomatic of LPR than those not. The use of multiple mucosal signs may improve detection of reflux sufferers from asymptomatic controls. The RFS has a sensitivity and specificity of 87.8% and 37.5%, respectively, for picking up pH-proven pharyngeal reflux individuals. Inter- and intrarater reliability for identifying signs is fair to good in most studies. n nConclusions: nThe limited evidence for each mucosal finding should be considered in making the diagnosis of LPR. Further quality research in to mucosal findings in LPR is needed.

Is undergraduate medical education working for ENT surgery? A survey of UK medical school graduates

BACKGROUNDnDespite the patient numbers and scope of ENT surgery, it is under-represented in most undergraduate medical curricula.nnnMETHODnAn online questionnaire was e-mailed, at National Health Service trust level, to 3,544 newly qualified doctors from 30 UK medical schools. Undergraduate ENT exposure, confidence and educational value were measured on a Likert scale.nnnRESULTSnWe received 444 eligible responses. The mean undergraduate ENT exposure was 3.4 days of pre-clinical teaching plus 5.0 days of ENT departmental experience. However, 15.8 per cent of respondents reported no formal departmental ENT experience, and 65.8 per cent would have liked further undergraduate experience. Teaching modalities with a lower perceived educational value were generally offered more frequently than those with a higher perceived educational value. Graduates felt significantly less confident with ENT history-taking, examination and management, compared with their cardiology clinical competencies (p < 0.001).nnnCONCLUSIONnThese results highlight the lack of UK ENT undergraduate education, and the significant effect this has on junior doctors clinical confidence. In addition, commonly used teaching methods may not be optimally effective.

Injection laryngoplasty in the outpatient clinic under local anaesthetic: a case series of sixty‐eight patients

We aimed to assess self‐report and perceptual voice outcomes in patients undergoing local anaesthetic injection laryngoplasty in our outpatient clinic.

Tissue transfer to post chemoradiation salvage laryngectomy defects to prevent pharyngocutaneous fistula: single-centre experience

Background: In recent practice, we have used tissue transfer (pedicled or free flap) to augment the pharyngeal circumference of the neopharynx following salvage total laryngectomy, even in patients who have sufficient pharyngeal mucosa for primary closure. In this study, the rates of pharyngocutaneous fistula were compared in soft tissue flap reconstructed patients versus patients who underwent primary closure. Method: A retrospective assessment was carried out of all patients who had undergone a salvage total laryngectomy between 2000 and 2010. The presence or absence of a pharyngocutaneous fistula was compared in those who received reconstruction closure versus those who received primary closure. Results: The reconstruction closure group (nxa0=xa07) had no incidence of pharyngocutaneous fistula, whereas the primary closure group (nxa0=xa038) had 10 fistulas, giving pharyngocutaneous fistula rates of 0 per cent versus 26 per cent, respectively. Conclusion: The findings revealed a lower rate of pharyngocutaneous fistula with tissue transfer compared with primary closure of the neopharynx.