γ-Heptalactone is an endogenously produced quorum-sensing molecule regulating growth and secondary metabolite production by Aspergillus nidulans.

Microbes monitor their population density through a mechanism termed quorum sensing. It is believed that quorum-sensing molecules diffuse from the microbial cells and circulate in the surrounding environment as a function of cell density. When these molecules reach a threshold concentration, the gene expression of the entire population is altered in a coordinated manner. This work provides evidence that Aspergillus nidulans produces at least one small diffusible molecule during its growth cycle which accumulates at high cell density and alters the organism's behaviour. When added to low-density cell cultures, ethyl acetate extracts from stationary phase culture supernatants of A. nidulans resulted in the abolition of the lag phase, induced an earlier deceleration phase with 16.3 % decrease in the final cell dry weight and resulted in a 37.8 % increase in the expression of ipnA::lacZ reporter gene construct, which was used as a marker for penicillin production compared to non-treated controls. The bioactive molecule present in the stationary phase extract was purified to homogeneity and was identified by liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy to be γ-heptalactone. This study provides the first evidence that A. nidulans produces γ-heptalactone at a high cell density and it can alter the organism's behaviour at a low cell density. γ-Heptalactone hence acts as a quorum-sensing molecule in the producing strain.

A clinical study monitoring low-intensity anticoagulant therapy with a standard-sensitivity thromboplastin.

The ability of the prothrombin time to measure the anticoagulant effect of warfarin sodium varies depending on the particular tissue thromboplastin used in performing the test. Based on studies using sensitive thromboplastins, lower therapeutic ranges of anticoagulation are recommended. The adequacy of monitoring therapy in this lower range with the relatively insensitive thromboplastins commonly used in North America is unestablished. This 16-month prospective study used a standard North American thromboplastin to monitor 157 anticoagulated patients treated in a low therapeutic range. Of the 1734 prothrombin times generated, 876 (56%) were therapeutic, with 400 (23%) below and 458 (26%) above the therapeutic range. These results are comparable with those published in trials in which more sensitive thromboplastins were used in a similar therapeutic range. We conclude that standard North American thromboplastins are adequately suited to monitor therapy in this lower range.

Abnormalities of blood coagulation tests in patients with cancer.

Routine blood coagulation tests were performed on 431 consecutive patients enrolled in a study of the role of anticoagulation in cancer treatment (VA Cooperative Study #75). Two hundred sixteen control patients were treated with standard therapy, and 215 patients were treated with standard therapy plus sodium warfarin. At the time of entry into the study, the most common abnormalities were elevated fibrinogen levels, platelet counts, and fibrinopeptide A levels. Serial studies demonstrated a steady increase in platelet count and fibrinogen levels before death. Anticoagulation lowered FPA levels but had no significant effect on fibrinogen levels, platelet counts, or euglobulin clot lysis times. An unexpected finding was a dramatic increase in fibrin split product levels after institution of anticoagulation (means +/- SEM = 42.6 +/- 116.4 vs. 2.9 +/- 7.0 mg/L in control subjects; P less than 0.02). This study supports the presence of subclinical activation of blood coagulation in most patients with cancer. Moreover, the preferential activation of fibrinolysis in anticoagulated patients suggests a role for a vitamin K-dependent factor(s) in the regulation of fibrinolysis in patients with cancer.

Bleeding complications from warfarin anticoagulation in patients with malignancy.

Bleeding complications from warfarin anticoagulants were analyzed in 431 patients with carcinoma of the lung, colon, prostate and head and neck who were admitted to a randomized, controlled therapeutic trial of this agent. A total of 215 patients were randomized to the warfarin-treated group and 216 to the control groups. The mean prothrombin time was significantly prolonged (p = 0.0001) for warfarin-treated patients. The duration of warfarin administration was 64.9% of the total followup period providing 101 patient-years of experience with warfarin in cancer. Both the overall incidence of bleeding episodes (58% of warfarin-treated versus 30% of control) and the incidence of major bleeding episodes (42% versus 14%, respectively) were significantly increased in the warfarin-treated group (p = less than 0.001). The incidence of major bleeding was 1.86 per patient-year on warfarin. The most common sites of bleeding (in descending order) were the gastointestinal tract, the urinary tract, the nasal passages and skin. Hemorrhage occurred in association with the terminal event in 10 warfarin-treated and 12 control patients. Warfarin anticoagulation may have contributed to terminal bleeding in 3 (1.4%) patients. There was no difference in mean hemoglobin or hematocrit values for patients with versus patients without bleeding episodes.

Comparison of local versus central tumor measurements in a multicenter cancer trial.

Four hundred nineteen solid tumors from 92 patients were measured by a local team consisting of a physician and nurse oncologist or physician's assistant, and centrally by one radiologist. The central radiologist also remeasured 137 tumors on 30 patients to assess intraexaminer agreement. Tumor measurements at specific points in time as well as changes in tumor measurements over time were evaluated. When signed differences were calculated, there was little overall difference between local and central examiners, although three of the eight centers did show a significant difference. However, when absolute differences were calculated, the relative errors of the width times length products ranged from 35 to 55%. Although local and central examiners agreed 75% of the time on change in disease, there was only 42% agreement on the subset of patients who had a remission. In general, the intraexaminer agreement was slightly better than the interexaminer agreement. This study suggests that solid tumor measurements are not particularly reliable, and that survival time remains the most satisfactory endpoint in a cancer clinical trial.

Effect of warfarin anticoagulation on survival in carcinoma of the lung, colon, head and neck, and prostate. Final report of VA Cooperative Study #75.

VA Cooperative Study #75 was established to test in a controlled, randomized trial the hypothesis that warfarin anticoagulation would favorably affect the course of certain types of malignancy. No differences in survival were observed between warfarin-treated and control groups for advanced non-small cell lung, colorectal, head and neck and prostate cancers. However, warfarin therapy was associated with a significant prolongation in the time to first evidence of disease progression (P = 0.016) and a significant improvement in survival (P = 0.018) for patients with small cell carcinoma of the lung, including the subgroup of patients with disseminated disease at the time of randomization (P = 0.013). A trend toward improved survival with warfarin treatment was observed for the few patients admitted to this study with non-small cell lung cancer who had minimal disease at randomization. These results suggest that warfarin, as a single anticoagulant agent, may favorably modify the course of some, but not all, types of human malignancy, among which is small cell carcinoma of the lung. Further trials of warfarin may be indicated in patients with limited disease who have cell types that failed to respond when advanced disease was present.

Accrual of patients into a multihospital cancer clinical trial and its implications on planning future studies.

Little information exists on the population of cancer patients from which individual patients are selected for admission to a clinical trial. In fact, most reports of clinical trials of cancer chemotherapeutic agents begin by describing samples of treated patients but neglect to collect data and describe the population from which the samples were taken. In a multi-institutional VA Cooperative Study in which two different cancer treatments were compared, an attempt was made to screen all lung, colorectal, prostate, and head and neck patients seen at participating hospitals prior to randomization to a therapeutic regimen. Of a total of 2687 patients screened, 437 (16.3%) were randomized and 2250 (83.7%) were excluded for 2981 reasons. Protocol reasons were the basis for 68.6% of all exclusions, 21.3% were physician refusals, and 10.1% were patient refusals. The number of patients randomized did not correlate well with number of patients screened across participating centers. Patients admitted to the study tended to be younger and in better health than excluded patients. Overestimates of randomization rates projected initially from published information point to the need for improved screening data in the planning of future studies. Factors such as screening methods, physician acceptance of the experimental approach, number of competing protocols within each center, and cooperation among medical center departments and personnel all are important ingredients in any screening effort.

Effect of warfarin on survival in small cell carcinoma of the lung. Veterans Administration Study No. 75.

In a controlled, randomized study, survival of patients with small cell carcinoma of the lung (SCCL) was prolonged on addition of warfarin sodium to combination chemotherapy plus radiation therapy. Median survival for 25 control patients was 24 weeks and for 25 warfarin-treated patients was 50 weeks. This difference could not be accounted for by differences between groups in performance status, extent of disease, age, or sex. The survival advantage associated with warfarin administration was observed both for patients with extensive disease and for those who failed to achieve complete or partial remission. The warfarin-treated group also demonstrated a significantly increased time to first evidence of disease progression. These results suggest that warfarin may be useful in the treatment of SCCL and also support the hypothesis that the blood coagulation mechanism may be involved in the growth and spread of cancer in man.