Influence of cigarette smoking on the efficacy of radiation therapy in head and neck cancer

BACKGROUND

Smoking is a risk factor for several cancers and may also limit the efficacy of treatment. In this study, we evaluated the influence of cigarette smoking during radiation therapy on the efficacy of treatment in patients with head and neck cancer.

METHODS

Using a questionnaire, we obtained information on smoking behavior at base line and weekly during therapy in 115 patients with head and neck cancer who were treated with radiation therapy with or without fluorouracil. The side effects of therapy were evaluated weekly, and response was assessed 13 weeks after treatment was completed. The main outcomes measured were treatment response and survival.

RESULTS

The prognostic variables were similar among the patients who smoked and those who did not smoke during treatment. The 53 patients who continued to smoke during radiation therapy had a lower rate of complete response (45 percent vs. 74 percent, P = 0.008) and poorer two-year survival (39 percent vs. 66 percent, P = 0.005) than the 62 patients who did not smoke or who had quit before treatment. Among the nonsmoking patients, mortality was influenced by the length of time between quitting and treatment, with a risk reduction (relative to that for patients who continued to smoke) of 40 percent for patients who had quit less than 12 weeks before diagnosis and of 70 percent for patients who had quit more than 1 year before diagnosis. After adjustment for other variables with proportional-hazards regression analysis, smoking remained an independent prognostic factor (P = 0.002), with a relative risk of 2.5 (95 percent confidence interval, 1.4 to 4.4) favoring the patients who abstained from smoking. The results could not be explained by the type of chemotherapy received, the presence of coexisting morbid conditions, differences in the side effects of radiation, or the number of interruptions of treatment.

CONCLUSIONS

Patients with head and neck cancer who continue to smoke during radiation therapy have lower rates of response and survival than patients who do not smoke during radiation therapy.

Purification of recombinant Helicobacter pylori urease apoenzyme encoded by ureA and ureB

Helicobacter pylori, a gram-negative, microaerophilic, spiral-shaped bacterium, is an etiologic agent of human gastritis and peptic ulceration and is highly restricted to the gastric mucosa of humans. Urease, synthesized at up to 6% of the soluble cell protein, hydrolyzes urea, thereby releasing ammonia, which may neutralize acid, allowing survival of the bacterium and initial colonization of the gastric mucosa. The urease protein is encoded by two subunit genes, ureA and ureB; however, accessory genes are necessary for enzyme activity. H. pylori urease genes were isolated from a cosmid gene bank and subcloned on a 5.8-kb Sau3A partial fragment carrying ureCDAB, corresponding to four open reading frames described by A. Labigne, V. Cussac, and P. Courcoux (J. Bacteriol. 173:1920-1931, 1991). Clones were confirmed as ureas gene sequences by polymerase chain reaction amplification. The recombinant enzyme was purified from the soluble protein of French press lysates of Escherichia coli DH5 alpha(pHP402) by chromatography on DEAE-Sepharose, Phenyl-Sepharose, Mono-Q, and Superose 6 resins. Fractions containing a catalytically inactive apoenzyme were identified by an enzyme-linked immunosorbent assay (ELISA) by using antisera to native UreA (29.5 kDa) and UreB (66 kDa). Purified recombinant urease was indistinguishable from native enzyme on a Superose 6 column and on Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gels. The protein reacted specifically on Western blots (immunoblots) with anti-UreA and anti-UreB antibodies and was recognized with an intensity equal to that of the native enzyme in an ELISA using human sera. Clones containing only ureA and ureB also produced an assembled but inactive enzyme. Enzyme activity was not restored by in trans complementation with cloned urease accessory gene sequences from Proteus mirabilis or Morganella morganii. H. pylori urease genes (ureCDAB) subcloned into pACYC184 were also not complemented with any of 1,000 cosmid clones containing H. pylori chromosomal sequences. However, larger clones containing 4.5 kb of DNA downstream of ureB synthesized catalytically active urease when grown in minimal medium. These data indicate that the ureA and ureB genes encoding H. pylori urease are transcribed and translated in E. coli and that these genes alone are sufficient for the synthesis and assembly of the native size enzyme. Genes downstream of ureB, however, are necessary for production of a catalytically active urease.

Insertional inactivation of the Staphylococcus aureus beta-toxin by bacteriophage phi 13 occurs by site- and orientation-specific integration of the phi 13 genome

Lysogenization of Staphylococcus aureus by the serotype F converting bacteriophage phi 13 results in loss of beta-toxin expression. Sequence analysis of the S. aureus beta-toxin gene (hlb), the attachment site (attP)-containing region of phi 13 DNA and the chromosome/bacteriophage DNA junctions of a phi 13 lysogen, revealed that the molecular mechanism of loss of beta-toxin expression was due to insertion of the phi 13 genome into the 5' end of hlb. The insertion site (attB) within hlb contained a 14 base pair core sequence in common with attP and both ends of the integrated linear prophage genome of a phi 13 lysogen. These findings indicate that integration of the phi 13 genome into hlb is site- and orientation-specific.

Diarrhea in ciguatera fish poisoning: preliminary evaluation of pathophysiological mechanisms

Ciguatera fish poisoning is a clinical syndrome consisting of a combination of gastrointestinal and neurological symptoms occurring after eating toxin-containing tropical reef fish; it is a major cause of morbidity in Hawaii, the South Pacific, Australia, and the Caribbean. In an effort to define pathophysiological mechanisms responsible for the diarrheal component of the illness, we examined the effect of crude and fractionated toxin preparations on isolated rabbit ileal tissue in a Ussing chamber model. Both the crude toxin preparation (prepared from toxic Ctenochaetus strigosus) and 10% and 50% methanol-chloroform toxin fraction (prepared from a pool of toxic fish samples) gave a striking increase in transepithelial electrical potential difference and short-circuit current. Enterotoxic activity seemed to be mediated by calcium. When examined by light microscopy, the intestinal mucosa was not damaged by the toxin preparations used. Our data demonstrate that toxins involved in ciguatera fish poisoning directly stimulate intestinal fluid secretion without accompanying tissue damage and suggest that calcium is the "second messenger" mediating the process.

Cocaethylene: a neuropharmacologically active metabolite associated with concurrent cocaine-ethanol ingestion

High concentrations of cocaethylene (EC), the ethyl ester of benzoylecgonine, were measured in the blood of individuals who had concurrently used cocaine and ethanol. Since the powerful reinforcing effects of cocaine appear to be dependent on inhibition of dopamine reuptake in brain, we compared the effects of EC on the dopamine uptake system and its behavioral effects with those of cocaine. EC was equipotent to cocaine with respect to inhibition of binding of [3H]GBR 12935 to the dopamine reuptake complex, inhibition of [3H]dopamine uptake into synaptosomes and in its ability to increase extracellular dopamine concentration in the nucleus accumbens following its systemic administration to rats. Moreover, in rats, EC and cocaine each increased locomotor activity and rearing to the same extent following i.p. administration. In self-administration studies in primates, EC was approximately equipotent to cocaine in maintaining responding. The in vivo formation of this active, transesterified ethyl homolog of cocaine may contribute to the effects and consequences of combined cocaine and ethanol abuse.

Anti-thymocyte globulin induced thrombocytopenia

Anti-thymocyte globulin is strongly reactive with platelets as measured by flow cytometric analysis. This reactivity appears to be independent of human leukocyte antigen (HLA) phenotype, is dose-dependent with saturation of platelet binding sites readily achieved with concentrations of horse anti-thymocyte globulin (ATG) at 0.25 mg per ml, and cannot be blocked with human anti-PLA1 antibody nor with heat-aggregated human IgG. Results of immunoblot studies after electrophoresis of platelet membrane proteins are consistent with the proposal that horse ATG contains antibodies specific for platelet glycoproteins V and IIa.

Maternal platelet antibody levels in neonatal isoimmune thrombocytopenia

A case of neonatal isoimmune thrombocytopenia (NIT) is described in which maternal platelet antibody levels decreased during the course of pregnancy. It is suggested that if this disorder is clinically suspected, maternal serum should be assessed for anti-platelet specificity using immunoblot analysis.

Modulation of the antitumor effect of methotrexate by low-dose leucovorin in squamous cell head and neck cancer: a randomized placebo-controlled clinical trial

Randomized trials comparing high-dose methotrexate (HDMTX) plus leucovorin (LV) with standard-dose methotrexate (SDMTX) have not detected a therapeutic advantage for the HDMTX arm despite compelling evidence from experimental systems. We hypothesized that these negative trials might reflect modulation of the antitumor effect of methotrexate (MTX) by LV. To test this we randomized 61 patients with locally advanced and recurrent squamous cell head and neck cancer to receive SDMTX (40 mg/m2 weekly for 8 weeks) and either LV or placebo "rescue" starting 24 hours later. Of the 61 randomized patients, there were protocol violations in two cases, leaving 59 patients evaluable for response using standard criteria, and for toxicity using the Eastern Cooperative Oncology Group (ECOG) scale. Of the 29 patients randomized to MTX plus LV, there were five responders (17.2%) compared with 11 of 30 (36.7%) patients randomized to MTX plus placebo (P = .047). Response was influenced independently by age, gender, and by previous treatment. Toxicity overall was more severe in patients randomized to MTX plus placebo (P = .016). This was accounted for primarily by differences in toxicities related to bone marrow function (neutrophil and platelet counts), stomatitis, and elevations of liver function tests. MTX therapy was more often interrupted for toxicity in the placebo group (P = .007) and discontinued for progressive disease in the LV group (P = .07). These results indicate that at the doses of MTX and LV used, LV modulates the antitumor effect as well as the toxicity of MTX in patients with head and neck cancer.

Gradient high-performance liquid chromatography using alkylphenone retention indices of insecticidal extracts of Penicillium strains

Purified extracts of four Penicillium strains which were active against the insect pest Spodoptera littoralis were analysed by gradient high-performance liquid chromatography (HPLC) for secondary metabolites using alkylphenone retention indices. HPLC of pure secondary metabolite standards detected previously in the extracts by thin-layer chromatography (TLC) was undertaken in order to obtain bracketed retention indices. More metabolites were detected by HPLC than by TLC, although some compounds detected by TLC in some strains were not detected by this HPLC method. A minority of metabolites were exclusive to each strain, and most were produced by more than one strain. The profiles were more characteristic of each strain when only the larger peaks were considered. This emphasizes the importance of detection limits in secondary metabolite analysis. Some of the implications of these analyses to fungus toxicity and systematic mycology are discussed.

Depression of humoral responses and phagocytic functions in vivo and in vitro by fish oil and eicosapentanoic acid

Previous studies have demonstrated that eicosapentanoic acid (EPA) has anti-inflammatory properties in both humans and experimental animals and may also depress humoral immunity in experimental animals. Our investigations showed that the addition of eicosapentanoic acid to human peripheral blood mononuclear cell cultures inhibited B cell responses to mitogenic stimulation and depressed the expression of interleukin 2 receptors in pokeweed mitogen-stimulated lymphocytes. Neutrophils were also affected in their ability to release the contents of primary and secondary granules, particularly when stimulated with antigen-antibody complexes. Similar depressions of B cell responses and neutrophil functions were observed in a normal volunteer who ingested 6 g/day of a commercially available fish oil extract (equivalent to 2.1 g of EPA/day) during a 6-week period. Phagocytosis, enzymatic release, circulating immunoglobulin levels, and the response to tetanus toxoid both in vivo and in vitro were depressed during ingestion of fish oil. Most parameters showed a trend toward normalization 6 weeks after the suspension of fish oil supplementation. These effects of fish oil extracts and EPA on phagocytosis and humoral responses may be advantageously used in the therapy of chronic inflammatory diseases and autoimmune diseases but could be a cause for concern when these compounds are used for longer periods of time and with minimal medical supervision for the prophylaxis of atherosclerosis.

Clinicopathologic features of young and old sphha/sphha mice. Mutants with congenital hemolytic anemia

A colony of mice with congenital hemolytic anemia, sphha/sphha, were evaluated over a 3-year period. Prominent findings included decreased survivability, reticulocytosis, increased peripheral blood leukocytes, extramedullary hematopoiesis in liver and spleen, lymphoid hyperplasia and membranoproliferative glomerulonephritis. Older (12 to 21 months) anemic animals had elevated serum levels of IgG1 and IgA. There was deposition of C3, IgG, IgM, and IgA in renal glomeruli of both control and anemic mice, but deposition of IgM and IgA was more prominent and widely distributed in anemic animals and correlated with mesangial expansion and the presence of electron dense deposits in the mesangium and in glomerular capillary walls. Prominent renal tubular hemosiderosis was noted in young and old anemic mice. The relation between the hemolytic anemia and glomerular disease is unclear but these mice may be an animal model useful for exploration of changes attendant with chronic hemolysis and evaluation of renal disease that accompanies hemolytic anemia.