Photodynamic therapy enables tumor-specific ablation in preclinical models of thyroid cancer

The incidence of differentiated thyroid cancer has increased significantly during the last several decades. Surgical resection is the primary treatment for thyroid cancer and is highly effective, resulting in 5-year survival rates greater than 98%. However, surgical resection can result in short- and long-term treatment-related morbidities. Additionally, as this malignancy often affects women less than 40 years of age, there is interest in more conservative treatment approaches and, an unmet need for therapeutic options that minimize the risk of surgery-related morbidities while simultaneously providing an effective cancer treatment. Photodynamic therapy (PDT) has the potential to reduce treatment-related side effects by decreasing invasiveness and limiting toxicity. Owing to multiple advantageous properties of the porphyrin-HDL nanoparticle (PLP) as a PDT agent, including preferential accumulation in tumor, biodegradability and unprecedented photosensitizer packing, we evaluate PLP-mediated PDT as a minimally invasive, tumor-specific treatment for thyroid cancer. On both a biologically relevant human papillary thyroid cancer (K1) mouse model and an anatomically relevant rabbit squamous carcinoma (VX2)-implanted rabbit thyroid model, the intrinsic fluorescence of PLP enabled tracking of tumor preferential accumulation and guided PDT. This resulted in significant and specific apoptosis in tumor tissue, but not surrounding normal tissues including trachea and recurrent laryngeal nerve (RLN). A long-term survival study further demonstrated that PLP-PDT enabled complete ablation of tumor tissue while sparing both the normal thyroid tissue and RLN from damage, thus providing a safe, minimally invasive, and effective alternative to thyroidectomy for thyroid cancer therapies.

Navigation-guided osteotomies improve margin delineation in tumors involving the sinonasal area: A preclinical study

OBJECTIVES

To demonstrate and quantify, in a preclinical setting, the benefit of three-dimensional (3D) navigation guidance for margin delineation during ablative open surgery for advanced sinonasal cancer.

MATERIALS AND METHODS

Seven tumor models were created. 3D images were acquired with cone beam computed tomography, and 3D tumor segmentations were contoured. Eight surgeons with variable experience were recruited for the simulation of osteotomies. Three simulations were performed: 1) Unguided, 2) Guided using real-time tool tracking with 3D tumor segmentation (tumor-guided), and 3) Guided by 3D visualization of both the tumor and 1-cm margin segmentations (margin-guided). Analysis of cutting planes was performed and distance from the tumor surface was classified as follows: "intratumoral" when 0 mm or negative, "close" when greater than 0 mm and less than or equal to 5 mm, "adequate" when greater than 5 mm and less than or equal to 15 mm, and "excessive" over 15 mm. The three techniques (unguided, tumor-guided, margin-guided) were statistically compared.

RESULTS

The use of 3D navigation for margin delineation significantly improved control of margins: unguided cuts had 18.1% intratumoral cuts compared to 0% intratumoral cuts with 3D navigation (p < 0.0001).

CONCLUSION

This preclinical study has demonstrated the significant benefit of navigation-guided osteotomies for sinonasal tumors. Translation into the clinical setting - with rigorous assessment of oncological outcomes - would be the proposed next step.

The image-guided operating room-Utility and impact on surgeon's performance in the head and neck surgery

BACKGROUND

The image-guided operating room (OR) is an emerging standard for dealing with complex cases in many surgical disciplines including neurosurgery, thoracic surgery, maxillofacial trauma, and orthopedic surgery. Its use in head and neck oncological surgery is not well established. The primary aim of this study was to assess the image quality of cone-beam CT (CBCT) under real clinical conditions. The secondary aim was to assess the effect on surgical performance and decision making.

METHODS

Intraoperative 3D imaging was performed using a CBCT capable C-Arm mounted on a multi-axis robot (Siemens Zeego) in the image-guided OR. All patients had immediate preoperative imaging taken with further intraoperative imaging performed as required. Ten initial patients, comprising 28 intraoperative scans, were used for questionnaire-based image reviews conducted with experienced head and neck clinicians. Scans were assessed for aspects of both image quality and clinical utility, on separate 5-point Likert scales (1-5).

RESULTS

The median rating for bony detail was 4 out of 5. Vascular detail was increased (P < 10^-8 ) from 1 to 3 with the use of IV contrast (region of interest CT# was 284 HU [SD, 47 HU]). Images were rated as 4 for freedom from artifact. Soft tissue definition was 2, with no significant improvement (P = .2) with the addition of IV iodinated contrast. Surgeons rated the greatest clinical utility (4) for the CBCT when assessing postreconstruction imaging of a complex case.

CONCLUSIONS

The image quality of CBCT in the image-guided OR is good for bony detail and complex oncological reconstructions in the head and neck setting but probably has limited benefit for intraoperative soft tissue delineation. Future studies must also focus on clinical outcomes to help demonstrate the value of the image-guided OR.

Inequality in the Survival of Patients With Head and Neck Cancer in Scotland

Background: Socioeconomic inequalities impact on the survival of head and neck cancer (HNC) patients, but there is limited understanding of the explanations of the inequality, particularly in long-term survival. Methods: Patients were recruited from the Scottish Audit of Head and Neck Cancer between 1999 and 2001 and were linked to mortality data as at 30th September 2013. Socioeconomic status was determined using the area-based Carstairs 2001 index. Overall and disease-specific survival were calculated using the Kaplan-Meier method with 95% confidence intervals (CI's) at 1-, 5-, and 12-years. Net survival at 1-, 5-, and 12-years was also computed with 95% CIs. Cox proportional hazard models with 95% CIs were used to determine the explanations for the inequality in survival by all-cause mortality and disease-specific mortality with 95% CIs. Results: Most patients were from the most deprived group, and were more likely to smoke, drink, have cancer of a higher stage and have a lower WHO Performance Status. A clear gradient across Carstairs fifths for unadjusted overall and disease-specific survival was observed at 1-, 5-, and 12-years for patients with HNC. Following the adjustment for multiple patient, tumor and treatment factors, the inequality in survival for patients with HNC had attenuated and was no longer statistically significant at 1-, 5-, and 12-years. Conclusion: A clear gradient across Carstairs fifths for unadjusted overall, disease-specific and net survival was observed at 1-, 5-, and 12-years for HNC patients in Scotland from 1999 to 2001. This study concludes that explanations for the inequality in the survival of patients with HNC are not straightforward, and that many factors including various patient, tumor and treatment factors play a part in the inequality in the survival of patients with HNC.

Determinants of long-term survival in a population-based cohort study of patients with head and neck cancer from Scotland

BACKGROUND

We investigated long-term survival from head and neck cancer (HNC) using different survival approaches.

METHODS

Patients were followed-up from the Scottish Audit of Head and Neck Cancer. Overall survival and disease-specific survival were calculated using the Kaplan-Meier method. Net survival was calculated by the Pohar-Perme method. Mutually adjusted Cox proportional hazards models were used to determine the predictors of survival.

RESULTS

A total of 1820 patients were included in the analyses. Overall survival at 12 years was 26.3% (24.3%, 28.3%). Disease-specific survival at 12 years was 56.9% (54.3%, 59.4%). Net survival at 12 years was 41.4% (37.6%, 45.1%).

CONCLUSION

Determinants associated with long-term survival included age, stage, treatment modality, WHO performance status, alcohol consumption, smoking behavior, and anatomical site. We recommend that net survival is used for long-term outcomes for HNC patients-it disentangles other causes of death, which are overestimated in overall survival and underestimated in disease-specific survival.

Outcomes of urgent suspicion of head and neck cancer referrals in Glasgow

INTRODUCTION

Primary care patients with a suspected head and neck cancer are referred through the urgent suspicion of cancer referral pathway. Rates of cancer detection through this pathway are low. Evidence surrounding the pathway of these patients is lacking. This study aimed to determine the outcome of urgent suspicion of cancer referrals for head and neck cancer.

METHODS AND METHODS

All head and neck cancer urgent suspicion of cancer referrals in NHS Greater Glasgow and Clyde between June 2015 and May 2016 were analysed in regard to their clinical pathway.

RESULTS

There were 2116 urgent suspicion of cancer referrals in the one-year period. The overall cancer rate was 235 (11.8%), compared with 152 (7.6%) that resulted in a primary head and neck cancer diagnosis. Of the total, 851 (42.6%) were reassured and discharged after one clinic appointment; 536 (26.8%) were followed up for suspected benign pathology and 436 (21.8%) were actively investigated for cancer.

CONCLUSION

A significant proportion of patients attending urgent suspicion of cancer clinic appointments can be seen and discharged in one clinic appointment, provided there is same day imaging available. Cancer identification rates through urgent suspicion of cancer pathways remain low.

Patterns of hospital admission in 54 501 patients with epistaxis over a 20-year period in Scotland, UK

BACKGROUND

Epistaxis affects most people over their lifetime. It is the commonest ear, nose and throat emergency. Hospital admission and socio-economic deprivation have been associated with mental health disorders, respiratory illness and with emergency hospital admissions. Low socio-economic status has never previously been associated with epistaxis, a common reason for admission to ear, nose and throat departments throughout the UK.

METHODS

Demographics from Information Services Division Scotland were analysed over a period of 20 years. This focused on gender, number of admissions, number of bed days, socio-economic deprivation (Scottish Index of Multiple Deprivation) and mortality within 1 year.

RESULTS

Data from 54 501 patients were assessed. Admission numbers and length of stay have significantly decreased (P < 0.0001). Males are more frequently affected (P = 0.001). Admission numbers were higher for patients in more deprived areas (P < 0.001). Mean duration of stay has decreased by 1 bed day. Surgical intervention of epistaxis has increased significantly (P < 0.001). There is an associated 1-year mortality rate of 9.8% following epistaxis.

CONCLUSION

There has been a significant decrease in hospital admissions and length of hospital stay in patients admitted with epistaxis over the past 20 years. There is a significant association with deprivation and epistaxis admission.

Conventional fractionation should not be the standard of care for T2 glottic cancer

Background

The aim of this study was to report outcomes and late toxicity following hypofractionated accelerated radiotherapy for T2 glottic cancers. We highlight the importance of hypofractionated treatments with shorter overall treatment times, in improving outcomes for T2 glottic cancers. We also compare the biologically effective dose of hypofractionated regimes, with conventional fractionation.

Methods

One hundred twelve patients with T2 glottic cancer were treated between January 1999 and December 2005. All patients were prescribed a hypofractionated accelerated radiotherapy dose of 52.5 Gray in 3.28 Gray per fraction, delivered over 22 days. Radiobiological calculations were used to assess the relationship of fraction size and overall treatment time on local control outcomes and late toxicity.

Results

The 5-year overall survival was 67%, the 5-year local control was 82%, and the 5-year disease-specific survival was 90%. The respective 5-year local control for T2a and T2b disease was 88.8 and 70.8% (p = 0.032). Severe late toxicity occurred in two patients (1.8%). Radiobiological calculations showed an increase in local control of nearly 12%, with a 10 Gray increase in biologically effective dose.

Conclusion

This study has demonstrated that accelerated hypofractionated regimes have improved local control and similar late toxicity compared with conventional fractionation schedules. This supports the use of hypofractionated regimes as the standard of care for early glottic laryngeal cancers.

The hidden cost of deep neck space infections

Introduction The incidence of deep neck space infection (DNSI) is rising and appears to be related to falling rates of tonsillectomy. The purpose of this study was to assess demographics of patients presenting with DNSI and the financial burden to the National Health Service (NHS). Methods Data were collected retrospectively on patients aged over 16 years admitted to NHS Greater Glasgow and Clyde with DNSI between 2012 and 2016. Demographics, aetiology and use of hospital resources were reviewed. The cost of hospital admissions was calculated using data from NHS Scotland's Information Services Division, the local diagnostics division and the British National Formulary. Results Seventy-four patients were admitted with DNSI during the study period. Forty (54%) were male. The mean age was 44.0 years (range: 16-86 years). The most frequent source of infection was the tonsil (n=30, 40.5%). The most common infective organism was Streptococcus constellatus (n=9, 12.2%). The mean length of stay was 11 days. Fifty-five patients (74.3%) required operative intervention. The mean cost of admission per patient was £5,700 (range: £332-£46,700). Conclusions This study highlights the high cost burden of DNSI to the NHS. The incidence of DNSI in Glasgow has risen over the study period; contributing factors may include the reduced tonsillectomy rate and a reduction in antibiotic prescribing. As the incidence of DNSI continues to rise, there will be an increase in cost to the NHS, which must be planned for.

The effect of tonsillectomy on the morbidity from recurrent tonsillitis

BACKGROUND

Tonsillitis is a common condition with an incidence in UK general practice of 37 per 1000 population a year.¹ Recurrent tonsillitis results in significant morbidity and impacts on individuals' quality of life. This study assesses the morbidity and quality of life of adults with recurrent tonsillitis, and the impact of surgical intervention on their health state.

OBJECTIVES

To describe disease-specific and global quality of life for adults with recurrent tonsillitis 6 months after tonsillectomy, using two instruments: the health impact of throat problems (HITP) and EuroQol-visual analogue scale questionnaire. To assess the overall health benefit from tonsillectomy as an intervention using the Glasgow Benefit Inventory (GBI). To assess potential predictors of tonsillectomy benefit.

DESIGN

A prospective, observational cohort audit of patients who have fulfilled Scottish Intercollegiate Guideline Network (SIGN) criteria for tonsillectomy.² SETTING: Secondary care, teaching hospital.

PARTICIPANTS

Seventy patients (57 female), median age 20 years (range 13-41).

RESULTS

Median preoperative HITP was 47 (range 15-67), compared to 4 (0-72), (P<.001) 6 months following surgery. Median HITP difference was 39.5 (range -20 to 75). There was no significant change in global Quality of Life. Median overall 6 months GBI was 39 (-3 to 100). Patients had an average of 27 episodes of tonsillitis over a period of seven years before "achieving" tonsillectomy, significantly higher than the SIGN guidelines of three or more episodes over three years.

CONCLUSIONS

Recurrent tonsillitis causes a poor disease-specific quality of life. Patients experienced a median of three episodes per year for seven years before tonsillectomy. Following tonsillectomy, patients had a significant improvement in their disease-specific quality of life. Baseline HITP significantly improved after tonsillectomy. The results imply patients with recurrent acute tonsillitis may be experiencing undue delay.

Paediatric tracheostomy-An 11 year experience at a Scottish paediatric tertiary referral centre

AIMS

The aim of this paper was to review the indications, complications and outcomes for tracheostomy at a Scottish paediatric tertiary referral hospital.

METHODS

All patients undergoing tracheostomy between January 2001 and September 2012 were identified. A retrospective case note analysis was performed.

RESULTS

111 tracheostomies were done in the study period. The mean number per year was 11 (3-12). Full data was available for 95 patients. There were 56 (59%) males and 39 (41%) females. Age at time of tracheostomy ranged from one day to 15 years, the mean age of tracheostomy insertion was 69 weeks. The majority of patients, 75 (79%), were under one year old when they had their tracheostomy. The most common indication was long-term ventilation (20%), followed by craniofacial abnormality causing airway obstruction (18%), followed by subglottic stenosis (14%). 37% of patients were decannulated.

CONCLUSIONS

This series reflects current trends in the indications for paediatric tracheostomy, with chronic lung disease of prematurity being the most common indication.

Four-Year Experience of Day Case Hemithyroidectomy: Patient-Reported Outcomes

Objectives:

Assess the safety, patient satisfaction, and outcome of day case hemithyroidectomy in our department.

Methods:

A prospective audit of all patients undergoing hemithyroidectomy in a single institution over a 3-year period. All patients who undergo a hemithryoidectomy in our department have a bilateral superficial cervical block using 20 mL of 0.25% chirocaine, 10 mL of xylocaine with 1% adrenaline, and minimal opioid use. Bipolar dissection is used with meticulous hemostasis to avoid the use of a drain. All patients are reviewed 1 week postoperatively, and patient satisfaction questionnaires are completed.

Results:

One hundred fifty patients had a hemithyroidectomy over the 4-year period. Average age was 49 years (21-77). Male to female ratio was 3.9:1. Average length of stay was 0.47 days (0-6). Eighty-one percent of patients had their operation performed as a day case. The main reasons for patients not having surgery performed as a day case were patient choice, social reasons, and medical complications postoperatively. There were no hematomas requiring a return to theater and no drains inserted. No patient required readmission after discharge. Average patient satisfaction score for those discharged as a day case was 9.09 (0: not satisfied to be discharged as a day case - 10: very satisfied to be discharged as a day case). Average pain score day 1 postop was 3 (0: no pain at all - 10: worst pain imaginable).

Conclusions:

Day case hemithyroidectomy is very agreeable to patients and if appropriate analgesia is used then the postoperative pain is minimal.

Paediatric thyroid cancer: the Scottish experience

BACKGROUND AND AIMS

Paediatric thyroid cancer is a rare disease, making diagnosis and treatment particularly challenging. Here we present the Scottish experience of thyroid cancer in the paediatric population and give an overview of how a child or adolescent that presents with a thyroid nodule should be investigated and managed.

METHODS AND RESULTS

Data has been obtained from ISD Scotland, giving population-based information on paediatric thyroid cancer. A literature review has been performed on the management and treatment of thyroid cancer in the younger population. Paediatric thyroid cancer in Scotland is a rare disease, although the incidence is increasing each year. In general, differentiated paediatric thyroid cancer carries a good prognosis, while the results are more mixed in the rarer pathologies such as medullary cancer.

CONCLUSION

Due to the small numbers of patients diagnosed each year in Scotland, it is imperative that these patients are discussed at a multidisciplinary thyroid MDT and managed in a tertiary referral centre by consultants and medical/nursing support staff who have experience in treating these patients.

Lack of prognostic effect of carbonic anhydrase-9, hypoxia inducible factor-1α and bcl-2 in 286 patients with early squamous cell carcinoma of the glottic larynx treated with radiotherapy

AIMS

To evaluate the prognostic significance of potential tumour markers of hypoxia and apoptosis in early squamous cell carcinoma of the glottic larynx managed with radiotherapy.

MATERIALS AND METHODS

In total, 382 patients with T1 and T2 squamous cell carcinoma of the glottic larynx (vocal cords) received radical radiotherapy (50-55 Gy, in 16 fractions in 98% of cases). Pre-treatment haemoglobin was available for 328 patients; biopsy samples were available for 286. Immunohistochemistry was carried out for carbonic anhydrase-9 (CA-9), hypoxia inducible factor-1α (HIF-1α) and Bcl-2.

RESULTS

At 5 years, locoregional control was achieved in 88.2%, cancer-specific survival in 95.0% and overall survival in 78.7%. Adverse prognostic factors for locoregional tumour recurrence were pre-treatment haemoglobin <13.0 g/dl (P = 0.035, Log rank test; sensitivity 0.28, specificity 0.84) and stage T2 rather than T1 (P = 0.002). The effect of haemoglobin level on locoregional control was not significant when stratified by the median of 14.2 g/dl (P = 0.43) or as a continuous variable (P = 0.59). High CA-9 (P = 0.11), HIF-1α (P = 0.67) and Bcl-2 (P = 0.77) expression had no prognostic significance.

CONCLUSIONS

High CA-9, HIF-1α and Bcl-2 do not add to the prognostic significance of tumour stage and lower haemoglobin in predicting failure of local control in early glottic larynx squamous cell carcinoma managed with radiotherapy. The effect of haemoglobin was not strong enough to be useful as a prognostic biomarker.

Mucosal melanoma of the head and neck: radiotherapy or surgery?

INTRODUCTION

Head and neck mucosal melanoma (MuM) is rare, comprising < 1% of all melanomas in Western Europe.

METHODS

A retrospective analysis of case records of patients treated between 1965 and 2001 was carried out. (Survival outcomes were obtained from the case notes and cancer registry.) The median age of the 68 patients was 63 years (range 29-86 years). Thirty-nine percent were male, and 61% were female. (The minimum follow-up time was 15 months.) The two most common primary sites were the sinonasal complex (65%) and oral cavity (19%). Twenty-one percent of patients presented with metastases (nodal or distant). Fifty-five patients were treated with curative intent: 30 patients with primary radiotherapy and 25 patients with surgery +/- postoperative radiotherapy.

RESULTS

The overall survival was 22% at 5 years, and the cancer-specific survival was 32% at 5 years.

CONCLUSION

MuM has a poor overall prognosis. Poor prognostic indicators are site at presentation and presentation with metastasis. This series is unique in that a significant proportion of patients were given primary radiotherapy as definitive treatment. Surgery may have advantages, particularly for oral cavity MuM. In contrast to previous reports, definitive radiotherapy is worthy of consideration as curative treatment.

Nasal insertion of St John's wort: an unusual cause of epistaxis

We report a case of severe unilateral epistaxis requiring surgical arrest of bleeding, via endoscopic sphenopalatine artery ligation and anterior ethmoidal artery ligation. This followed recreational nasal insertion of St John's wort (Hypericum perforatum). Interactions between this substance and prescribed drugs have been described following oral ingestion. However, this unusual case highlights a further, worrying potential rhinological side effect of this substance.

Efficacy of caspofungin against Aspergillus flavus, Aspergillus terreus, and Aspergillus nidulans

The echinocandin caspofungin is a potent inhibitor of the activity of 1,3-beta-D-glucan synthase from Aspergillus flavus, Aspergillus terreus, and Aspergillus nidulans. In murine models of disseminated infection, caspofungin prolonged survival and reduced the kidney fungal burden. Caspofungin was at least as effective as amphotericin B against these filamentous fungi in vivo.

Specific substitutions in the echinocandin target Fks1p account for reduced susceptibility of rare laboratory and clinical Candida sp. isolates

An association between reduced susceptibility to echinocandins and changes in the 1,3-beta-d-glucan synthase (GS) subunit Fks1p was investigated. Specific mutations in fks1 genes from Saccharomyces cerevisiae and Candida albicans mutants are described that are necessary and sufficient for reduced susceptibility to the echinocandin drug caspofungin. One group of amino acid changes in ScFks1p, ScFks2p, and CaFks1p defines a conserved region (Phe 641 to Asp 648 of CaFks1p) in the Fks1 family of proteins. The relationship between several of these fks1 mutations and the phenotype of reduced caspofungin susceptibility was confirmed using site-directed mutagenesis or integrative transformation. Glucan synthase activity from these mutants was less susceptible to caspofungin inhibition, and heterozygous and homozygous Cafks1 C. albicans mutants could be distinguished based on the shape of inhibition curves. The C. albicans mutants were less susceptible to caspofungin than wild-type strains in a murine model of disseminated candidiasis. Five Candida isolates with reduced susceptibility to caspofungin were recovered from three patients enrolled in a clinical trial. Four C. albicans strains showed amino acid changes at Ser 645 of CaFks1p, while a single Candida krusei isolate had a deduced R1361G substitution. The clinical C. albicans mutants were less susceptible to caspofungin in the disseminated candidiasis model, and GS inhibition profiles and DNA sequence analyses were consistent with a homozygous fks1 mutation. Our results indicate that substitutions in the Fks1p subunit of GS are sufficient to confer reduced susceptibility to echinocandins in S. cerevisiae and the pathogens C. albicans and C. krusei.

Anthrax lethal factor inhibition

The primary virulence factor of Bacillus anthracis is a secreted zinc-dependent metalloprotease toxin known as lethal factor (LF) that is lethal to the host through disruption of signaling pathways, cell destruction, and circulatory shock. Inhibition of this proteolytic-based LF toxemia could be expected to provide therapeutic value in combination with an antibiotic during and immediately after an active anthrax infection. Herein is shown the crystal structure of an intimate complex between a hydroxamate, (2R)-2-[(4-fluoro-3-methylphenyl)sulfonylamino]-N-hydroxy-2-(tetrahydro-2H-pyran-4-yl)acetamide, and LF at the LF-active site. Most importantly, this molecular interaction between the hydroxamate and the LF active site resulted in (i) inhibited LF protease activity in an enzyme assay and protected macrophages against recombinant LF and protective antigen in a cell-based assay, (ii) 100% protection in a lethal mouse toxemia model against recombinant LF and protective antigen, (iii) approximately 50% survival advantage to mice given a lethal challenge of B. anthracis Sterne vegetative cells and to rabbits given a lethal challenge of B. anthracis Ames spores and doubled the mean time to death in those that died in both species, and (iv) 100% protection against B. anthracis spore challenge when used in combination therapy with ciprofloxacin in a rabbit "point of no return" model for which ciprofloxacin alone provided 50% protection. These results indicate that a small molecule, hydroxamate LF inhibitor, as revealed herein, can ameliorate the toxemia characteristic of an active B. anthracis infection and could be a vital adjunct to our ability to combat anthrax.

The antifungal echinocandin caspofungin acetate kills growing cells of Aspergillus fumigatus in vitro

Caspofungin acetate is an antifungal antibiotic that inhibits synthesis of 1,3-beta-D-glucan, an essential component of the fungal cell wall. While caspofungin causes cell death in yeasts and dimorphic fungi such as Candida albicans, its effect on Aspergillus fumigatus is less well understood. We used the fluorescent dyes 5,(6)-carboxyfluorescein diacetate (CFDA) and bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC), which stain live and dead cells, respectively, to further characterize the antifungal activity of caspofungin. For comparison, compounds whose mode of action was either fungistatic (fluconazole, itraconazole) or fungicidal (amphotericin B) were also evaluated. A correlation between caspofungin-induced loss of viability, decreased CFDA staining, and increased DiBAC staining was established first with C. albicans. For A. fumigatus, caspofungin caused similar dye-staining changes, which were quantified by fluorimetric analysis of stained hyphae grown in a medium that promoted dispersed growth. The minimum concentration of caspofungin required to produce these changes also decreased the level of growth-dependent reduction of the indicator dye Alamar Blue. We observed a differential effect of caspofungin as a function of cell position: 88% of apical cells and 61% of subapical branching cells failed to stain with the viable dye CFDA, but only 24% of subapical cells were unstained. Complementary results were seen with germlings from DiBAC-stained, caspofungin-treated cultures. Extended incubation of A. fumigatus with a single dose of caspofungin affected the same proportion of apical and subapical branching cells for up to 72 h. The dye-staining patterns illustrate that the cells at the active centers for new cell wall synthesis within A. fumigatus hyphae are killed when they are exposed to caspofungin.

Fungal beta(1,3)-D-glucan synthesis

The polysaccharide beta(1,3)-D-glucan is a component of the cell wall of many fungi. Synthesis of the linear polymer is catalysed by UDP-glucose beta(1,3)-D-glucan beta(3)-D-glucosyltransferase. Because this enzyme has a key role in fungal cell-wall synthesis, and because many organisms that are responsible for human mycoses, including Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans, produce walls that are rich in beta(1,3)-glucan, it has been and remains the focus of intensive study. From early characterization of the enzymatic activity in Saccharomyces cerevisiae, advances have been made in purification of the enzyme, identification of essential subunits and description of regulatory circuitry that controls expression and localization of different components of the multisubunit enzyme complex. Progress in each of these areas has been enhanced dramatically by the availability of specific inhibitors of the enzymatic reaction that produces beta(1,3)-glucan. These natural product inhibitors have utility both as tools to dissect the biology of beta(1,3)-glucan synthase and as sources for development of semisynthetic derivatives with clinical utility in treatment of human fungal disease. This review will focus on the biochemistry, genetics and regulation of the enzyme.

Quantitative PCR assay to measure Aspergillus fumigatus burden in a murine model of disseminated aspergillosis: demonstration of efficacy of caspofungin acetate

Caspofungin acetate (MK-0991) is an antifungal antibiotic that inhibits the synthesis of 1,3-beta-D-glucan, an essential component of the cell wall of several pathogenic fungi. Caspofungin acetate was recently approved for the treatment of invasive aspergillosis in patients who are refractory to or intolerant of other therapies. The activity of 1,3-beta-D-glucan synthesis inhibitors against Aspergillus fumigatus has been evaluated in animal models of pulmonary or disseminated disease by using prolongation of survival or reduction in tissue CFU as assay endpoints. Because these methods suffer from limited sensitivity or poor correlation with fungal growth, we have developed a quantitative PCR-based (qPCR) (TaqMan) assay to monitor disease progression and measure drug efficacy. A. fumigatus added to naïve, uninfected kidneys as either ungerminated conidia or small germlings yielded a linear qPCR response over at least 4 orders of magnitude. In a murine model of disseminated aspergillosis, a burden of A. fumigatus was detected in each of five different organs at 4 days postinfection by the qPCR assay, and the mean fungal load in these organs was 1.2 to 3.5 log(10) units greater than mean values determined by CFU measurement. When used to monitor disease progression in infected mice, the qPCR assay detected an increase of nearly 4 log(10) conidial equivalents/g of kidney between days 1 and 4 following infection, with a peak fungal burden that coincided with the onset of significant mortality. Traditional CFU methodology detected only a marginal increase in fungal load in the same tissues. In contrast, when mice were infected with Candida albicans, which does not form true mycelia in tissues, quantitation of kidney burden by both qPCR and CFU assays was strongly correlated as the infection progressed. Finally, treatment of mice with induced disseminated aspergillosis with either caspofungin or amphotericin B reduced the A. fumigatus burden in infected kidneys to the limit of detection for the qPCR assay. Because of its much larger dynamic range, the qPCR assay is superior to traditional CFU determination for monitoring the progression of disseminated aspergillosis and evaluating the activity of antifungal antibiotics against A. fumigatus.