Mechanism of Daunomycin Intercalation into DNA from Enhanced Sampling Simulations.

Daunomycin is a widely used anticancer drug, yet the mechanism underlying how it binds to DNA remains contested. 469 all-atom trajectories of daunomycin binding to the DNA oligonucleotide d(GCG CAC GTG CGC) were collected using weighted ensemble (WE)-enhanced sampling. Mechanistic insights were revealed through analysis of the ensemble of trajectories. Initially, the binding process involves a ubiquitous hydrogen bond between the DNA backbone and the NH3+ group on daunomycin. During the binding process, most trajectories exhibited similar structural changes to DNA, including DNA base pair rise, bending, and minor groove width changes. Variability within the ensemble of binding trajectories illuminates differences in the orientation of daunomycin as it initially intercalates; around 10% of trajectories needed minimal rearrangement from intercalation to reaching the fully bound configuration, whereas most needed an additional 1-5 ns to rearrange. The results here emphasize the utility of generating an ensemble of trajectories to discern biomolecular binding mechanisms.

Molecular Mechanism of Ligand Binding to the Minor Groove of DNA.

Although DNA-ligand binding is pervasive in biology, little is known about molecular-level binding mechanisms. Using all-atom, explicit-solvent molecular dynamics simulations in conjunction with weighted ensemble (WE)-enhanced sampling, an ensemble of 2562 binding trajectories of Hoechst 33258 (H33258) to d(CGC AAA TTT GCG) was generated from which the binding mechanism was extracted. In particular, the electrostatic interaction between the positively charged H33258 and the negatively charged DNA backbone drives the formation of initial H33258-DNA contacts. After this initial contact, a hinge-like intermediate state is formed in which one end of H33258 inserts into the minor groove of DNA. Following hinge state formation is a concerted motion whereby the second end of H33258 swings into the minor groove and the spine of hydration along the minor groove causing dehydration. This study illustrates how WE-enhanced simulations of biomolecular ligation processes can offer novel mechanistic insights by generating ensembles of binding events.

[Gastroesophageal reflux: a possible cause of paroxysmal laryngeal dyspnea]. / La dyspnée laryngée paroxystique: une manifestation extra-oesophagienne peu connue du reflux gastro-oesophagien.

An important number of patients are referred to the ENT specialist because of extraoesophageal manifestations of gastroesophageal reflux. The most alarming symptom is a paroxysmal dyspnea secondary to a laryngospasm. The patients report a laryngeal choking sensation associated to an aphonia. We report three cases of laryngospasm secondary to acid gastric reflux. The diagnosis was made with the clinical history, a laryngeal examination and a 24-hour pH-monitoring enabled us to demonstrate a clear temporal relation between the reflux episodes and the choking episodes. In conclusion, the pharyngo-laryngeal reflux is a possible cause of laryngospasm. In our three patients, a high dose antiacid treatment was efficient to bring a lasting relief of the symptoms.

Horizontal partial laryngectomy for supraglottic squamous cell carcinoma.

Between 1981-1999, 75 patients treated for supraglottic SCC with horizontal supraglottic laryngectomy (HSL) at the Otolaryngology Head and Neck Surgery Department of Lausanne University Hospital were retrospectively studied. There were 16 patients with T1, 46 with T2 and 13 with T3 tumors. Among these, 16 patients (21%) had clinical neck disease corresponding to stage I, II, III and IV in 12, 39, 18 and 6 patients, respectively. All patients had HSL. Most patients had either elective or therapeutic bilateral level II-IV selective neck dissection. Six patients (8%) with advanced neck disease had ipsilateral radical and controlateral elective II-IV selective neck dissections. Adjuvant radiotherapy was given to 25 patients (30%) for either positive surgical margins (n=8), pathological nodal status (n=14) or both (n=3). Median follow-up was 48 months (range, 24-199). Five-year disease-specific survival and locoregional and local control were 92, 90 and 92.5%, respectively. Among five patients who were diagnosed with local recurrence, one had a total laryngectomy (1.4%); the others were treated by endoscopic laser surgery. Two patients had both a local and regional recurrence. They were salvaged with combined surgery and radiotherapy, but eventually died of their disease. Cartilage infiltration seems to influence both local control (P=0.03) and disease-specific survival (P=0.06). There was a trend for worse survival with pathological node involvement (P=0.15) and extralaryngeal extension of the cancer (P=0.1). All patients except one recovered a close to normal function after the treatment. Aspiration was present in 16 patients (26%) in the early postoperative period. A median of 16 days (7-9) was necessary to recover a close to normal diet. Decannulation took a median of 17 days (8-93). Seven patients kept a tracheotomy tube for up to 3 months because of persistent aspiration. There was no permanent tracheostomy or total laryngectomy for functional purposes. Horizontal supraglottic laryngectomy remains an adequate therapeutic alternative for supraglottic squamous cell carcinoma, offering an excellent oncological outcome. The postoperative functional morbidity is substantial, indicating the need for careful patient selection, but good laryngeal function recovery is the rule. The surgical alternative is endoscopic laser surgery, which may offer comparable oncological results with less functional morbidity. Nevertheless, these two different techniques need to be compared prospectively.

Treatment of early stage squamous-cell carcinoma of the glottic larynx: endoscopic surgery or cricohyoidoepiglottopexy versus radiotherapy.

BACKGROUND: Both surgery and radiotherapy are recognized treatments of T1-T2 squamous cell carcinoma of the larynx. We retrospectively analyze and compare the oncological outcome of patients treated in a single institution, either by endoscopic surgery or partial supracricoid laryngectomy versus radiation therapy. METHODS: The medical records of 156 patients treated between 1983 and 1996 with either surgery (n = 75) or radiotherapy (n = 81) were reviewed. Male to female ratio, median age, and T-stage distribution were comparable. RESULTS: With a median follow-up time of 59 months, the 5-year cause-specific survival rate of 93% was identical for both groups. The actuarial incidence of metachronous second primaries was 7% at 5 years. Local control at 5 years remained 84% after surgery and 77% after radiotherapy. Anterior commissure infiltration was shown to represent a negative predictive factor of local control for radiotherapy (p =.01). Salvage treatment brought ultimate local control to 96% of patients after surgery and 94% after radiation therapy with long-term laryngeal preservation rate altered significantly (p =.05) in the group of patients who received radiotherapy (90.1% vs 97.4%). CONCLUSION: The treatment of laryngeal cancer is always a compromise between oncological efficiency and preservation of function. Our data suggest that, assuming proper selection of patients, radiation therapy and surgery yield similar local control and survival rates. The functional disadvantages after surgery are moderate and clearly counterbalanced by a significant decrease in long-term laryngeal preservation rate after radiotherapeutic treatment.

[Treatment of laryngeal cancer: cordectomy or crico-hyoido-epiglottopexy versus radiotherapy]. / Traitement du cancer laryngé: cordectomie ou crico-hyoïdoépiglottopexie versus radiothérapie.

INTRODUCTION: Both radiotherapy and endoscopic or open functional surgery are recognised treatments for laryngeal cancer stage I and II. A comparison between two groups of patients treated with either modality may clarify the indications for both treatments. METHODS: Over a period of 13 years two separate series of patients were treated for laryngeal cancer (stage I and II) by either surgery (n = 72) or radiotherapy (n = 81). We have analysed and compared the two groups. RESULTS: Statistical analyses show a better local control among patients treated with surgery, when the anterior commissure was involved (p < 0.01) or with extension of the tumour (T2). However, long-term survivals were not significantly different in the two groups. As postradiation recurrence was diagnosed at an early stage, salvage (requiring total laryngectomy in many cases) was efficient but contributed to an appreciable difference in the long-term laryngeal preservation rate between the two groups (91% after radiotherapy and 99% after surgery). CONCLUSION: The treatment of laryngeal cancer must always compromise between oncological efficiency and functional preservation. With anterior commissure involvement (T1b) or more extensive disease (T2), surgery appears to be better. Therefore, preservation of perfect laryngeal function should be subordinate to oncological safety.

Supracricoid partial laryngectomy with cricohyoidoepiglottopexy and cricohyoidopexy for glottic and supraglottic carcinomas.

OBJECTIVES: To review the patients operated in our department with supracricoid partial laryngectomy with either cricohyoidoepiglottopexy (CHEP) (59 cases) or cricohyoidopexy (CHP) (10 cases) technique, for primary or recurrent glottosupraglottic squamous cell carcinoma and compare the technique with other surgical or conservative approaches for treatment of laryngeal carcinoma. METHODS: From hospital charts, we retrospectively reviewed 69 patients who had undergone supracricoid partial laryngectomy with the CHEP or CHP technique between 1983 and 1996 for primary or recurrent glottosupraglottic squamous cell carcinoma in our department. Statistical evaluation of oncological and functional results were conducted. Results were compared with other surgical and conservative treatment for glottosupraglottic carcinoma of the larynx that were published previously in the literature. RESULTS: Sixty-nine patients had CHEP or CHP for glottosupraglottic carcinoma of the larynx. Thirteen percent of the patients received adjuvant radiotherapy. Minimum follow-up was 2 years or until death. Five-year actuarial survival (Kaplan-Meier method) was 68%. Global local control was achieved in 84% of cases. Among previously untreated patients (n = 54), local control rate was 94.5%. After 1 year, 92.7% of patients achieved normal swallowing and respiration. Salvage total laryngectomy had to be performed in four patients (5.7%) for persistent aspiration and in five patients (7.2%), who were previously treated with radiotherapy, for local recurrence. No permanent tracheostomy or gastrostomy was required. CONCLUSIONS: Our experience with supracricoid partial laryngectomy with either CHP or CHEP suggests that this technique is a valuable alternative to radiotherapy for T2-T4 glottosupraglottic carcinomas, particularly those with extension and invasion of the anterior commissure. It allows for preservation of a good laryngeal function without altering the long-term survival, keeping total laryngectomy as a salvage procedure.

[Indications and complications of free micro-flaps in ORL oncology]. / Indications et complications des lambeaux microanastomosés en carcinologie ORL.

Eighty-three free flaps were used to repair head and neck cancer defects between 1993 and 1995. The flaps used were 37 (44%) radial forearm flaps, 29 (35%) iliac crest flaps, 8 (10%) free jejunum flaps, 4 (5%) fibula flaps, 3 (3%) latissimus dorsi flaps and 2 (2%) rectus abdomini flaps. The indications for each flap are discussed. The flap loss rate was 4.8%, which led to reoperation with a new free flap in 3.6% of the cases. The other complications are discussed. Pre and post operative radiotherapy had no influence on the outcome of the free flaps. The mean duration of hospitalisation was 36 days. 78% of the patients who underwent a mandibular reconstruction were fitted with a fixed dental prosthesis and had normal mastication. 66% of the patients with oropharyngeal reconstruction had normal deglutition and 30% had a mixed diet. The acceptable complication rate, the good esthetic and functional results obtained with free flaps indicate that they should be used as a first choice technique in the reconstruction of head and neck cancer defects.

Percutaneous transtracheal jet ventilation for paediatric endoscopic laser treatment of laryngeal and subglottic lesions.

Percutaneous transtracheal high frequency jet ventilation (TTJV) in adults is frequently used during anaesthesia for laryngeal microsurgery. It provides excellent surgical operating conditions and safety for the patient. The technique has not been evaluated in infants and children. Accordingly, we studied 16 infants and children (mean age 5.5 +/- 3.8 yr, range 6 wk-12 yr) who underwent 28 consecutive endoscopic procedures with laser microsurgery of the glottic or subglottic space under general anaesthesia using a TTJV technique. All patients had a severe obstructive lesion of the larynx and/or upper trachea. The mean duration of the procedure was 70 +/- 27 min (range 30-140 min). Indications for TTJV were: subglottic stenosis: 5, haemangioma: 4, laryngeal papillomatosis: 5, pharyngeal cyst: 1, laryngomalacia: 1. Adequate control of the airway and satisfactory gas exchange were obtained in all cases. Surgery was performed without being impeded by anaesthetic equipment. Three complications occurred: one extensive surgical emphysema; one bilateral pneumothorax; one severe vagus-induced cardiovascular depression. Prompt and complete recovery without sequelae followed appropriate treatment. In 32% of the cases, the children were outpatients and in about half of the procedures (13/28) they left the hospital between the first and the third day. We conclude that percutaneous transtracheal jet ventilation is effective in paediatric endoscopic surgery. Procedures that might otherwise require a tracheostomy can be performed safely with this minimally invasive technique. Adequate indications and appropriate understanding of the technique and its potential problems are required for its correct application and successful use.

[Precancerous conditions of the esophagus]. / Les précancéroses de l'oesophage.

In the upper aerodigestive tract, carcinogenesis in squamous cell mucosa is characterized by a tendency to field carcinogenesis leading to multicentricity of lesions and synchronous or metachronous multiple tumoral lesions, namely multifocality. During pretherapy broncho-esophagoscopy carried out on ENT-cancer patients, the rate of synchronous second primary cancer is 24%. In 85% of the cases, these second primaries are detected at an early stage (in situ, microinvasive or submucosal carcinoma) and do not give rise to symptoms. Early diagnosis of cancer of the upper aerodigestive tract is possible provided that high risk patients are recognized and screening endoscopy of the whole mucosa is performed in every high risk patient. On the other hand, squamous cell carcinoma and adenocarcinoma may occur with increased frequency in patients with esophageal lesions such as achalasia, caustic stenosis and Barrett's esophagus. The premalignant potential of these three entities is discussed.