p53 mutations in deep tissues are more strongly associated with recurrence than mutation-positive mucosal margins.

Purpose: Application of ultrasensitive diagnostics has shown that small numbers of p53 mutation-positive cells may signify the presence of residual tumor in histologically normal tissues after resection of squamous cell carcinomas arising in the head and neck area. To date, most studies in this area have focused on analysis of tissues at the mucosal aspect of the resection and highlighted the importance of molecular changes in the field with respect to the risk of recurrence.

Experimental Design: In the present investigation, we analyzed normal tissues from mucosal and deep surgical margins, referred to as "molecular margins," for the presence of the signature p53 mutation identified for each tumor.

Molecular analysis of paired tumours: time to start treating the field.

Molecular analysis of paired tumours highlights the limitations of the current clinical criteria for identifying second primary tumours. At present the finding of identical novel microsatellite alleles in paired lesions provides a "gold standard" marker for establishing clonal origin. However, these aberrations occur at low frequency and other methods for determining clonality have been proposed.

Development of a facile fluorescent assay for the detection of 80 mutations within the p53 gene.

Background: Alterations in the p53 tumor suppressor gene constitute one of the most frequent genetic events associated with the development of human cancers. Determination of an individual's p53 status may be of value in early diagnosis, prediction of response to treatment, and for the detection of minimal residual cancer. Recent studies have also revealed that specific mutations affecting the p53 gene are associated with a poor outcome.

Profiling clonality and progression in multiple premalignant and malignant oral lesions identifies a subgroup of cases with a distinct presentation of squamous cell carcinoma.

A cohort of head and neck cancer patients, without exposure to tobacco and alcohol, presented with multiple preneoplastic and neoplastic lesions, the natural history of which may span several decades. Examination of these cases provides an opportunity to study the relationship between genetic, morphological, and clonal progression in these fields and establish whether they represent a unique presentation of squamous cell carcinoma. The presence of a common novel microsatellite allele, a common breakpoint or concordant allelic imbalance at multiple loci, reveals that a high proportion of these serial lesions arise due to spread of a precursor.

A case-control study confirms that microsatellite assay can identify patients at risk of developing oral squamous cell carcinoma within a field of cancerization.

Distinguishing true precursor lesions on the basis of clinical or histological features alone is unreliable but is important so that appropriate intervention can be instigated. Preliminary studies have shown that a microsatellite assay may provide important new prognostic information. To build on these observations, we have performed a case-control study to establish whether we can be confident about incorporating this new information into clinical practice.

Detection of minimal residual cancer to investigate why oral tumors recur despite seemingly adequate treatment.

Improvements in surgery and radiotherapy techniques have led to only a modest increase in the 5-year survival rate for patients with head and neck cancer. This is because the pattern of clinical disease is changing, such that locoregional recurrence now accounts for fewer treatment failures, but more patients develop a second primary cancer or distant metastatic disease. In this study, we have used the p53 phage plaque assay, immunocytochemistry, and mutational analysis to assess the contribution of minimal residual cancer and genetic aberrations in clinically normal upper aerodigestive tract mucosa to treatment failure.

The FHIT gene in oral squamous cell carcinoma: allelic imbalance is frequent but cDNA aberrations are uncommon.

The FHIT (fragile histidine triad) gene at chromosome 3p14.2 spans the FRA3B fragile site and encodes for a diadenosine triphosphate hydrolase-type protein. FHIT is frequently abnormal in solid tumours including those of the upper aerodigestive tract (UAT) and has therefore been proposed as a tumour-suppressor gene.

Location of candidate tumour suppressor gene loci at chromosomes 3p, 8p and 9p for oral squamous cell carcinomas.

To help define the location of tumour suppressor genes implicated in the pathogenesis of oral squamous cell carcinoma (SCC), we have used microsatellite assay and restriction fragment length polymorphism (RFLP) analysis to screen 48 primary SCC for allelic imbalance (AI) with 32 polymorphic markers at chromosome 3p, and prepared a detailed deletion map. The finding of a high frequency of AI at specific regions, together with the presence of multiple small interstitial deletions involving these loci, identifies 5 areas at this chromosome arm that may harbour tumour suppressor genes. No sequence aberrations affecting the von Hippel Lindau (VHL) and fragile histidine triad (FHIT) genes, which reside within the candidate tumour suppressor gene areas at this chromosome arm, were identified.

Patient-specific mutation databases for oral cancer.

Development of databases, summarising the genetic events associated with oral squamous cell carcinoma (SCC), should increase our understanding of the molecular basis of these lesions. Additionally, databases will help establish whether different cancer subtypes show different growth characteristics, because the multistage carcinogenic process is different in the various tumour subtypes. This new knowledge may also provide new prognostic information, as these aberrations represent fundamental biological characteristics of each tumour.

New insights into p53 protein stabilisation in oral squamous cell carcinoma.

p53 is a transcription factor which regulates cell proliferation and apoptosis to prevent division of potentially malignant cells. In many tumours mutation of the p53 gene leads to stabilisation of this protein which can be detected by immunohistochemistry (IHC). However, there are many reports describing detection of p53 by IHC in the absence of gene mutation, and in these cases other factors stabilise p53.

The prognostic significance of allelic imbalance at key chromosomal loci in oral cancer.

Forty-eight primary oral squamous cell carcinomas (SCC) were screened for allelic imbalance (AI) at 3p24-26, 3p21, 3p13, 8p21-23, 9p21, 9q22 and within the Rb, p53 and DCC tumour suppressor genes. AI was detected at all TNM stages with stage 4 tumours showing significantly more aberrations than stage 1-3. A factional allelic loss (FAL) score was calculated for all tumours and a high score was associated with development of local recurrence (P = 0.

Allelic imbalance at chromosomal loci implicated in the pathogenesis of oral precancer, cumulative loss and its relationship with progression to cancer.

A microsatellite assay was used to screen 31 potentially malignant oral lesions presenting as leukoplakia and erythroplakia, with histological evidence of dysplasia, for genetic abnormalities at loci which frequently show allelic imbalance when oral squamous cell carcinomas (SCC) are examined. The microsatellite and restriction fragment length polymorphism (RFLP) markers selected were at 3p21, 8p21-23, 9p21 and included sequences within the Rb (13q14.2), p53 (17p13.

Field cancerisation of the oral cavity: comparison of the spectrum of molecular alterations in cases presenting with both dysplastic and malignant lesions.

Dysplastic lesions and invasive oral squamous cell carcinoma (SCC) from patients with field change were screened by restriction fragment length polymorphism (RFLP) and microsatellite assay. All tumours contained more genetic changes than the matched dysplasia which are likely to represent progression. Four of the 15 dysplastic lesions harboured the same abnormalities detected in the tumour and some paired lesions showed identical novel microsatellite alleles.

Cardiorespiratory effects of intravascular injections of lidocaine in the anesthetized rat. Comparisons between arterial and venous routes of administration.

The consequences of two types of intravascular injections of lidocaine 1.5 to 15 mg/kg on three cardiorespiratory parameters were studied in 16 anesthetized rats. Administration of the local anesthetic via either the internal carotid artery (n = 8) or the external jugular vein (n = 8) caused hypotension, bradycardia, and respiratory slowdown.

Circulatory and respiratory effects of lidocaine administered into the rat maxillofacial circulation.

The inadvertent intra-arterial administration of local anesthetics is a serious hazard of oral operations. For this reason, the circulatory and respiratory consequences of introducing lidocaine into the maxillofacial (MF) arterial circulation were examined in anesthetized rats. Lidocaine boluses of 0.

Effects of mepivacaine, prilocaine and lidocaine on the induced constriction of the maxillofacial vasculature of the rat.

Infusions of mepivacaine 5 or 50 micrograms.min-1 and prilocaine 50 micrograms.min-1 for 10 min into the maxillofacial arterial vasculature of the anaesthetized rat curtailed significantly rises in infusion pressure induced by the administration of adrenaline via the same route.

Local anaesthesia efficacy: discrepancies between in vitro and in vivo studies.

Electrophysiological studies on isolated nerves have been used extensively in the past to assess the comparative efficiency of local anaesthetics as agents of peripheral nerve blockade. It is shown here that three closely related amide local anaesthetics behave differently in vitro and in vivo. In terms of onset of action and of maximum suppression of the evoked action potential, mepivacaine proved a less efficient anaesthetic than lidocaine or prilocaine on isolated nerves, but in parallel studies on the sciatic nerve of live animals and in the absence of vasoconstrictors: (a) mepivacaine's potency was superior to that of the other two agents, (b) its speed of onset of anaesthetic action was at least as good and (c) its duration of action was found to be considerably longer.

The effects of ornipressin and adrenaline on lignocaine nerve blocks.

An electrophysiological method measuring nerve conduction following the electrical stimulation of a sciatic nerve branch in anaesthetised rats was used to evaluate under strictly controlled conditions the effects of 1:100,000 adrenaline and of 0.03 IU X ml-1 ornipressin on the speed of onset, depth and duration of lignocaine anaesthesia. It was shown that compared with plain lignocaine, lignocaine with ornipressin produced shorter onset of anaesthesia and improved its depth and duration.

Effects of i.a. lignocaine on adrenaline-induced vasoconstriction.

The effects of i.a. administered lignocaine on the in vivo response of the vascular bed supplied by the lingual, external maxillary and posterior auricular branches of the common carotid artery were studied in the rat.

Prostaglandin E1-induced sensitization of A delta moderate pressure mechanoreceptors.

Prostaglandins of the E series (PGEs) have been detected in high quantities in inflamed tissues; when injected in the circulation that supplies the skin they cause inflammation and pain. Evidence of PGE sensitization of C-nociceptors (polymodals) already exists. The present work establishes that PGE1 has a wider sensitizing effect: when injected subdermally it affects mechanoreceptive elements as well.