Assessing antimicrobial resistance in Campylobacter jejuni and Campylobacter coli and its association with antimicrobial use in Canadian turkey flocks

Turkeys are important sources of antimicrobial-resistant Campylobacter. A total of 1063 isolates were obtained from 293 turkey flocks across Canada between 2016 and 2021 to evaluate their antimicrobial resistance (AMR) prevalence, patterns, distribution, and association with antimicrobial use (AMU). A high proportion of C. jejuni and C. coli isolates were resistant to tetracyclines and fluoroquinolones, despite the very low use of these drugs. C. jejuni isolates had a higher probability of being resistant to tetracyclines than C. coli isolates. The chance of C. jejuni isolates being resistant to fluoroquinolones, macrolides, and lincosamides was lower compared to C. coli. Isolates from the western region had a higher probability of being resistant to fluoroquinolones than isolates from Ontario. Isolates from Ontario had higher odds of being resistant to tetracyclines than isolates from Quebec. No associations were noted between the resistance and use of the same antimicrobial, but the use of certain antimicrobial classes may have played a role in the maintenance of resistance in Campylobacter (fluoroquinolone resistance - bacitracin and streptogramin use, tetracycline resistance - flavophospholipids and streptogramins use, macrolide resistance - flavophospholipid use). Low-level multidrug-resistant Campylobacter was observed indicating a stable AMR in turkeys. This study provided insights aiding future AMU and AMR surveillance.

Decrease in the prevalence of antimicrobial resistance in Escherichia coli isolates of Canadian turkey flocks driven by the implementation of an antimicrobial stewardship program

The emergence of antimicrobial-resistant organisms at the human-animal-environment interface has raised global concern prompting governments and various stakeholders to take action. As a part of the stewardship initiative, Canadian turkey producers have implemented an antimicrobial use (AMU) strategy to manage antimicrobial resistance (AMR) in their sector. This study evaluated farm-level AMU and AMR data collected between 2016 and 2021 in major turkey-producing provinces/regions through the Canadian Integrated Program for Antimicrobial Resistance Surveillance to assess the progress of the strategy by characterizing the prevalence of homologous and multidrug resistance (MDR) in Escherichia coli isolated from turkeys. Multivariable mixed-effect logistic regression models assessed temporal and provincial/regional variations in AMR and MDR. Negative binomial regression models examined the temporal and regional variations in the total AMU. The total AMU (measured in mg/kg turkey biomass) significantly decreased in all provinces/regions in 2020 and 2021. Escherichia coli isolates from turkey flocks showed a significant decrease in resistance to gentamicin, sulfisoxazole, and tetracyclines during the six-year study period, consistent with the timing of the AMU reduction strategy. The prevalence of MDR isolates was significantly lower in 2020 and 2021 compared to 2016. Higher prevalence was observed in the Western region compared to Québec and Ontario. Two common AMR patterns were identified: ampicillin-streptomycin-tetracyclines and streptomycin-sulfisoxazole-tetracyclines. These AMR patterns indicate possible cross-resistances (same class), co-selection (unrelated classes) for resistance, or potential carryover of resistance determinants from previous production cycles. The decreasing prevalence of resistance to homologous antimicrobials, MDR, and AMU quantity are suggestive that the turkey sector's AMU strategy is achieving its desired impact. However, antimicrobials previously eliminated for preventive use in turkey flocks and the use of highly important antimicrobials in human medicine suggest that the AMU reduction strategy should be monitored and re-evaluated periodically to mitigate the emergence of MDR bacteria and safeguard animal and public health.

Phylogenetic characterization of canine distemper virus from stray dogs in Kathmandu Valley

Canine distemper is a highly contagious, often fatal disease caused by canine distemper virus (CDV) in domestic dogs and wild carnivores. The virus has caused mass epidemics in both wild and captive carnivores of high conservation value such as tigers, lions and leopards. Hence, understanding and managing CDV outbreaks is particularly important in Nepal, which is home to many species of threatened wild carnivores including tigers, leopards, snow leopards, dholes and wolves, and also contains a large population of stray dogs. Previous studies have suggested that CDV may pose a threat to wild carnivores, but there have not been any studies characterizing the genetic strains of the virus circulating in Nepal's carnivores. We collected invasive and non-invasive biological samples from stray dogs in Kathmandu Valley and genetically characterized the strains of CDV in the dogs to belong to the Asia-5 lineage by using phylogenetic analysis. The same lineage also contained CDV strains sequenced from dogs, civets, red panda and lions in India. Based on our phylogenetic analysis, we think it is likely that CDV is maintained through sylvatic cycle among sympatric carnivores allowing the recurring spillovers and outbreaks. It is crucial to prevent the virus transmission from reservoir hosts to other species, especially threatened populations of large carnivores in Nepal. Hence, we recommend for regular surveillance of CDV targeting wild carnivores in addition to the domestic dogs.

Comparison of antimicrobial resistance among Salmonella enterica serovars isolated from Canadian turkey flocks, 2013-2021

The emergence of antimicrobial resistance (AMR) in Salmonella from turkeys has raised a food safety concern in Canada as certain serovars have been implicated in human salmonellosis outbreaks in recent years. While several studies evaluated AMR in broiler chickens in Canada, there are limited studies that assess AMR in turkey flocks. This study analyzed data collected between 2013 and 2021 by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) farm turkey surveillance program to determine the prevalence of AMR and differences in resistance patterns among Salmonella serovars recovered from turkey flocks. Salmonella isolates were tested for susceptibility to 14 antimicrobials using a microbroth dilution method. Hierarchical clustering dendrograms were constructed to compare the individual AMR status of Salmonella serovars. Differences in the probability of resistance between Salmonella serovars were determined using generalized estimating equation logistic regression models to account for farm-level clustering. Of the 1,367 Salmonella isolates detected, 55.3% were resistant to at least one antimicrobial and 25.3% were multidrug resistant (MDR) (resistant to ≥3 antimicrobial classes). The Salmonella isolates exhibited high resistance to tetracycline (43.3%), streptomycin (47.2%), and sulfisoxazole (29.1%). The 3 most frequently occurring serovars were S. Uganda (22.9%), S. Hadar (13.5%), and S. Reading (12.0%). Streptomycin-sulfisoxazole-tetracycline (n = 204) was the most frequent MDR pattern identified. Heatmaps showed that S. Reading exhibited coresistance to the quinolone class antimicrobials, ciprofloxacin, and nalidixic acid; S. Heidelberg to gentamicin and sulfisoxazole; and S. Agona to ampicillin and ceftriaxone. Salmonella Hadar isolates had higher odds of resistance to tetracycline (OR: 152.1, 95% CI: 70.6-327.4) while the probability of being resistant to gentamicin and ampicillin was significantly higher in S. Senftenberg than in all the other serovars. Moreover, S. Uganda had the highest odds of being MDR (OR: 4.7, 95% CI: 3.7-6.1). The high resistance observed warrants a reassessment of the drivers for AMR, including AMU strategies and other production factors. Differences in AMR patterns highlight the need to implement serovar-specific mitigation strategies.

Associations between antimicrobial resistance in fecal Escherichia coli isolates and antimicrobial use in Canadian turkey flocks

Antimicrobial resistance (AMR) in enteric bacteria continues to be detected in turkey flocks and retail products worldwide, including in Canada. However, studies assessing linkages between on-farm antimicrobial use (AMU) and the development of AMR are lacking. This study aims to identify AMU characteristics that impact the development of AMR in the indicator bacteria Escherichia coli in turkey flocks, building on the Canadian Integrated Program for Antimicrobial Resistance Surveillance methodology for farm-level AMU and AMR data integration. Two analytic approaches were used: (1) multivariable mixed-effects logistic regression models examined associations between AMU (any route, route-specific, and route-disease-specific indication) summarized as the number of defined daily doses in animals using Canadian standards ([nDDDvetCA]/1,000 kg-animal-days at risk) and AMR and (2) multivariable mixed-effects Poisson regression models studied the linkages between AMU and the number of classes to which an E. coli isolate was resistant (nCR_{E. coli}). A total of 1,317 E. coli isolates from a network of 16 veterinarians and 334 turkey producers across the five major turkey-producing provinces in Canada between 2016 and 2019 were used. Analysis indicated that AMR emerged with the use of related antimicrobials (e.g., tetracycline use-tetracycline resistance), however, the use of unrelated antimicrobial classes was also impacting AMR (e.g., aminoglycosides/streptogramins use-tetracycline resistance). As for studying AMU-nCR_{E. coli} linkages, the most robust association was between the parenteral aminoglycosides use and nCR_{E. coli}, though in-feed uses of four unrelated classes (bacitracin, folate pathway inhibitors, streptogramins, and tetracyclines) appear to be important, indicating that ongoing uses of these classes may slow down the succession from multidrug-resistant to a more susceptible E. coli populations. The analysis of AMU (route and disease-specific)-AMR linkages complemented the above findings, suggesting that treatment of certain diseases (enteric, late-stage septicemic conditions, and colibacillosis) are influential in the development of resistance to certain antimicrobial classes. The highest variances were at the flock level indicating that stewardship actions should focus on flock-level infection prevention practices. This study added new insights to our understanding of AMU-AMR linkages in turkeys and is useful in informing AMU stewardship in the turkey sector. Enhanced surveillance using sequencing technologies are warranted to explain molecular-level determinants of AMR.

MILK Symposium review: Improving control of mastitis in dairy animals in Nepal

Dairy animals are an important source of income, food, and nutritional security, and improvements in the productivity of dairy animals substantially improve the wellbeing of smallholder dairy farmers. As in other developing countries, dairy animals are key for rural livelihoods in Nepal but often suffer from mastitis-a production disease causing economic losses to farmers, challenges to the dairy processing industry, and possible health hazards to consumers. Studies show that the prevalence of subclinical mastitis in Africa and Asia typically exceeds 50%, threatening animal wellbeing, farmers, dairy processors, and consumers. We conducted a study in Nepal to develop a technology training package to control mastitis in dairy animals. Following identification of knowledge gaps, a technology package consisting of (1) developing good husbandry practices, implementing mastitis detection and control technologies; and (2) training technicians and farmers was implemented. A strategy was subsequently established to provide feedback to farmers in dairy cooperatives on the subclinical mastitis status of their cows. The package was applied in the mid-western region of Nepal. Six months after implementation, we observed a reduction in subclinical mastitis prevalence: from 55% (baseline) to 28% (endline; n = 432) in dairy cows and from 78% to 18% (n = 216) in buffalo. These positive study outcomes strongly suggest that the mastitis technology training package should be scaled across smallholder farmers within and beyond Nepal to control mastitis in dairy animals.

Metabolic changes in cimetidine treatment for scald injury on the peritoneo-serosal surface in far-advanced gastric cancer patients treated by intraperitoneal hyperthermic perfusion

Since pretreatment with cimetidine results in the prevention of scald injury on the peritoneo-serosal surface caused by intraperitoneal hyperthermic perfusion (IPHP) for advanced gastric cancer, the diverse influence of IPHP on patients who were either given or not given cimetidine was studied both during and after IPHP treatment. Cimetidine 50 mg/kg was injected intravenously into 12 patients immediately prior to IPHP. There were no statistical background differences between the cimetidine and control groups (those not given cimetidine). The inflow and outflow temperatures of the hyperthermic perfusate in the control and cimetidine groups were 46.1 +/- 0.1 degree C and 44.1 +/- 0.1 degree C and 46.3 +/- 0.1 degree C and 44.2 +/- 0.04 degree C, respectively. Either the pre-IPHP hypothermia or IPHP in the control group resulted in a considerable increase in serum noradrenaline and adrenaline. The intravenous administration of cimetidine led to a stransient but moderate drop in the mean blood pressure as well as a delayed appearance of high concentrations of noradrenaline and adrenaline, induced by high concentrations of circulating histamine released with cimetidine. These results suggest that the sympathetic nervous responses were activated either by hypothermia or hyperthermia. The transient hypotension and delayed increases of both serum catecholamines were attributed to a marked increase in circulating histamine, released with the intravenous cimetidine.

[The experimental and clinical study of hyperthermia with thermosensitizer for gastric cancer patients with peritoneal seeding]

We examined experimentally and clinically the effect of misonidazole (MISO), a hypoxic cell radiosensitizer, in combination with hyperthermia. First, tissue blood flow and tumor growth of xenoplanted human gastric cancer in nude mice were measured after treatment with MISO 500 mg/kg ip plus hyperthermia at 40.5, 42.0 and 43.5 degrees C. Also clinically, 17 advanced gastric cancer patients with peritoneal seeding underwent intraperitoneal hyperthermic perfusion (IPHP). They were given MISO 1.45 g/m2 po twice (12 hours and 5 hours before IPHP). And plasma MISO levels were measured. MISO plus hyperthermia produced a more prolonged decrease of the tumor blood flow than hyperthermia alone. At 43.5 degrees C, TbF recovered 2 days after the treatment. MISO plus hyperthermia also made tumor growth delay more marked than hyperthermia alone. In gastric cancer patients treated with MISO plus IPHP, T 1/2 of serum MISO was 7.7 hours and the AUC was 1,087 micrograms.hr/ml. There were no side effects observed which were caused by MISO. Thus MISO can be an effective thermosensitizer when used in combination with hyperthermia.

Effects on tumour microcirculation in mice of misonidazole and tumour necrosis factor plus hyperthermia

We examined the effects of misonidazole (MISO) and recombinant human tumour necrosis factor (rh-TNF) on tumour blood flow in mice given hyperthermic treatments. MISO (500 mg kg-1) or rh-TNF (6 x 10(4) unit kg-1) was administered intraperitoneally (i.p.) prior to hyperthermia to nude mice bearing a xenoplanted human gastric cancer and tumour blood flow was measured by a hydrogen diffusion method based on polarographic determinations. MISO plus hyperthermia produced a temperature-dependent decrease in blood flow and, at 43.5 degrees C, the flow decreased to 15-30% of control and remained low for up to 24 h. Blood flow following rh-TNF plus hyperthermia was less than that at the same temperatures following MISO plus hyperthermia, and, at 43.5 degrees C, the flow decreased to 10-20% of control and remained low for up to 48 h. Tumour growth delay was closely related to the duration of the decrease in blood flow. Thus, the profound decrease in tumour blood flow following hyperthermia plus MISO or rh-TNF and the consequential tumour regression may well be of potential clinical significance.

A novel anticancer treatment for xenoplanted human gastric cancer using polyamine antimetabolites in a low polyamine diet

The aim of the present study was to evaluate a new anticancer treatment for gastrointestinal cancer, using a combination of polyamine antimetabolites, an anticancer agent and a low-polyamine state. Two polyamine antimetabolites, given as either 40 mg/kg of methylglyoxal-bis-guanylhydrazone (MGBG) or ethylglyoxal-bis-guanylhydrazone (EGBG) and a normal diet (ND), or 20 mg/kg of each drug and a low polyamine diet (LPD), together with 1,000 mg/kg of alphadifluoromethylornithine (DFMO) were administered ip to nude mice for six consecutive days. Mitomycin C (MMC) at 2 mg/kg was then given ip for 3 alternate days. The combination of MGBG or EGBG with DFMO plus MMC resulted in an enhanced antitumor efficacy on LPD. However, the combination which included EGBG was much more enhanced than that which included MGBG and there was no evidence of any tumor regrowth. Weight loss was minimal or nil in the mice given the combination with EGBG, but was evident in those given the combination with MGBG. These results led to the conclusion that in mice, the combined therapy of EGBG with DFMO plus MMC and LPD is a safe and effective regimen for the treatment of gastric cancer.

[Clinical evaluation of intra-peritoneal hyperthermic perfusion under hypothermic general anesthesia for advanced gastric cancer]

Right after surgery, intra-peritoneal hyperthermic perfusion (IPHP) was performed under hypothermic general anesthesia for 41 gastric cancer patients with peritoneal dissemination or serosal invasion. The control group consisted of 40 patients given surgery alone. With respect to the direct antitumor efficacy of IPHP, there were no cancer cells in the peritoneal lavage from Douglas' pouch and, ascitic effusion disappeared in all patients with peritoneal dissemination. The 1- and 3-year survival rates for the IPHP group were 68% and 39%, whereas those of the control group were 30% and 0%, respectively. The survival rates for the IPHP group were better than those for the control group, with a statistically significant difference of p = 8.1 x 10(-7). As to prevention of recurrence, the incidence of peritoneal dissemination for the IPHP group was lower at p = 0.002 than the control group.

[Prevention of scald injury due to intraperitoneal hyperthermic perfusion for far-advanced gastric cancer]

In an attempt to prevent scald injury on the peritoneo-serosal surface due to intraperitoneal hyperthermic perfusion (IPHP) for far-advanced gastric cancer patients, a histamine H2-receptor antagonist, cimetidine, was prescribed for 9 patients. The IPHP treatment was carried out with a closed circuit using a heated perfusate, and intra-abdominal temperature was kept over 44 degrees C throughout IPHP, for 120 minutes. Of 18 patients given IPHP, 9 were administered intravenously cimetidine at a dose of 50 mg/kg just before IPHP (cimetidine group) and the remaining 9 were prescribed IPHP and not given cimetidine (control group). Amounts of exudate and protein from peritoneal cavity and serum histamine were compared between the two groups. The amount of intra-abdominal exudate was 768 +/- 95 ml for 24 hours in the control group, against 408 +/- 75 ml in the cimetidine group. The protein amounts in exudate throughout IPHP were 62.5 +/- 23.5 g in the control group, against 15.9 +/- 5.4 g in teh cimetidine group. Both the exudate and protein amounts were significantly decreased in the cimetidine group, compared with the controls (p = 1.416 x 10(-7), p = 5.358 x 10(-5)). Serum histamine levels in the cimetidine group increased 2.5 to 6.5 fold for over 12 hours after IPHP, compared to those in the control group. These findings suggest that cimetidine suppresses scald injury on the peritoneo-serosal surface by competitive inhibition with histamine. Consequently, histamine originated from the scald region was released into the circulating blood. Thus, cimetidine helped to prevent thermal injury due to the IPHP.

Prevention of scald injury on the peritoneo-serosal surface in advanced gastric cancer patients treated with intraperitoneal hyperthermic perfusion

In attempts to avoid the side-effects derived from a scald on the peritoneo-serosal surface during intraperitoneal hyperthermic perfusion (IPHP) for advanced gastric cancer, a randomized study using cimetidine, a histamine H2-receptor antagonist, was carried out on 18 patients with advanced gastric cancer. Cimetidine, 50 mg/kg, was administered intravenously and immediately before IPHP. The background characteristics of the patients and the types of surgical treatment used were almost the same between each group of patients, whether or not cimetidine was given. The perfusion time in the cimetidine and control groups was 123 +/- 9 and 117 +/- 9 min, respectively. The inflow and outflow temperatures of the perfusate were 46.3 +/- 0.4 and 44.2 +/- 0.1 degrees C in the cimetidine group, respectively, whereas in the control group the temperatures were 46.0 +/- 0.3 and 44.1 +/- 0.2 degrees C, respectively. In the nine patients who were given cimetidine, the histamine concentrations in the peripheral blood increased significantly, compared to those in the nine controls; this resulted from the release of histamine into the circulating blood. Higher concentrations of protein were observed in the post-hyperthermic intraperitoneal exudate of the control group for 3-24 h after IPHP and, consequently, post-hyperthermic hypoproteinaemia was remarkable in the control group. These data suggest that when pre-IPHP cimetidine was prescribed for patients with gastric cancer treated with IPHP, the peritoneo-serosal surface was protected from scald injury and the side-effects of IPHP were reduced.

Augmented antitumour effects of combined treatment with hyperthermia and tumour necrosis factor on human gastric cancer xenotransplanted into nude mice

Hyperthermia combined with recombinant human tumour necrosis factor (rH-TNF) was evaluated for antitumour efficacy in vivo. Use was made of human gastric cancer tissues xenografted into nude mice. When 100, 300, 600, and 1200 units of rH-TNF (2.4 x 10(6) units/mg protein) were given twice intraperitoneally, tumour regression did not occur in any animal. In contrast, a remarkable suppression of tumour growth was observed when 600 and 1200 units of rH-TNF was given in combination with hyperthermia at 43.5 +/- 0.1 degrees C. No effects were evident with the regimen of 100 and 300 units of rH-TNF plus hyperthermia at the same temperature, as compared with evidence obtained with hyperthermia alone. The tumoral blood flow, determined by the hydrogen diffusion method, decreased immediately after hyperthermia alone or hyperthermia plus 1200 units of rH-TNF, whereas a slight decrease was seen after rH-TNF alone. When hyperthermia plus 1200 units of rH-TNF were given, there was a remarkable delay in reversion to pretreatment values of tumoral blood flow, as compared to findings with rH-TNF only or heat only. These results are discussed in relation to the antitumour and side-effects of rH-TNF.

Positive results of combined therapy of surgery and intraperitoneal hyperthermic perfusion for far-advanced gastric cancer

To evaluate the clinical efficacy of intraperitoneal hyperthermic perfusion (IPHP) for far-advanced gastric cancer, particularly with peritoneal seeding, we investigated the survival times of 59 patients who underwent distal subtotal gastrectomy, total gastrectomy, or total gastrectomy combined with concomitant resection of some of the remaining intra-abdominal organs. In all the 30 patients given IPHP, no cancer cells were present posthyperthermically in the lavage from the Douglas pouch. The 30 patients given IPHP lived longer than the 29 patients not given IPHP (p = 0.001), with a 1-year survival rate of 80.4% in the former group compared to 34.2% in the latter. With respect to a comparison of survival time of patients with peritoneal seeding, 7 patients not given IPHP had a 6-month survival rate of 57.1% and did not survive more than 9 months, whereas 20 patients given IPHP had 1- and 2-year survival rates of 78.7% and 45.0%, respectively; here the difference was significant (p = 0.001). The IPHP and control groups without peritoneal metastasis included 10 and 22 patients, respectively, and the 1-year survival rates are 85.4% and 45.3%, respectively. The survival rates of the former exceeded those of the latter, with p = 0.015 by the generalized Wilcoxon test. Thus this combined therapy offers the promise of extended survival for patients with far-advanced gastric cancer.

[Clinical effect of intraperitoneal hyperthermochemotherapy on the survival rate for advanced gastric cancer patients]

Intraperitoneal hyperthermic perfusion (IPHP) was performed right after surgery for 31 advanced gastric cancer patients with serosal invasion and/or peritoneal dissemination. The survival rate in the IPHP group, was compared with that in the control group, 30 patients who underwent surgery alone within the same period of time. The 1-year survival rates for IPHP group and control group were 81.9% and 40.3%, respectively. The 2-year survival rates were 52.1% and 11.8%, and the 3-year survival rates were 26.1% and 0%, respectively. The survival rate for IPHP group was better than that for control group, with p = 1.46 x 10(-4). IPHP and control group with peritoneal dissemination included 21 and 9 patients respectively, and 50% survival rates were 18 months and 4.2 months, respectively. IPHP and control group with serosal invasion included 10 and 21 patients, respectively, and 8 out of 10 patients survived in the IPHP group, while 17 out of 21 patients died in the control group. These results suggest that IPHP is effective for gastric cancer patients with peritoneal dissemination and/or serosal invasion.

[Clinical evaluation of recurrent patterns of gastric cancer after intraperitoneal hyperthermic perfusion]

The patterns of recurrence and the prognosis of 24 gastric cancer patients with peritoneal seeding and/or serosal invasion, who underwent gastrectomy followed by intraperitoneal hyperthermic perfusion (IPHP), were studied in comparison with 23 gastric cancer patients given surgery alone (controls). With respect to 22 patients with peritoneal seeding, all of 8 patients in the control group died of re-accumulation of ascitic effusion, whereas of 14 patients in the IPHP group, 3 died of peritoneal recurrence, 2 of intraperitoneal tumors, 1 from pleural metastasis, and 1 of liver metastasis. The remaining 7 cases are alive without a sign of recurrence. Again, with respect to 25 patients with large serosal penetration of cancer, 7 of 15 patients in the controls died of peritoneal recurrence, whereas this was never observed in the IPHP group. As to the relation of histology and prognosis, while the poorly differentiated adenocarcinoma and signet ring cell carcinoma had poor prognosis in the controls, the same patterns in the IPHP group proved not to be so unfavorable. Since a few given IPHP resulted in hepatic metastasis and/or nodal involvement, adjuvant treatment will be required. The survival rate for the IPHP group was significantly better at p = 3.43 x 10(-2) than in controls.

[Clinical results of intraperitoneal hyperthermic perfusion combined with surgery in patients with peritoneal recurrence from gastric cancer]

Six patients with peritoneal recurrence after radical operation for gastric cancer were treated by an intraperitoneal hyperthermic perfusion (IPHP) combined with surgery (IPHP group). Immediately after surgery, a 2-hour IPHP was performed, using a perfusate containing 10 micrograms/ml of MMC, warmed at the inflow temperature of 46.5 +/- 1.1 degree C. Within the same period of time, 5 patients with intra-abdominal recurrent gastric cancer (control group) were treated by an intraperitoneal administration of MMC 10 mg combined with surgery. These 11 patients had malignant peritoneal effusion and, although in 3 of the control group, ascitic effusion did re-accumulate rapidly soon after surgery, the 6 patients of IPHP group did not re-accumulate post-hyperthermically. The average survival duration of IPHP group is 13.6 +/- 10. 6 months, whereas that for controls is 3.0 +/- 2.1 months. Again, the survival rate for IPHP group surpassed that for controls at p = 0.012 and p = 0.008, in a generalized Wilcoxon method and Logrank method, respectively. Post-hyperthermically, hypoproteinemia and thrombocytopenia occurred transitorily. These results show that IPHP using MMC combined with surgery is a safe, reliable treatment for patients with peritoneal recurrence due to gastric cancer.

[Effect of degradable starch microspheres (DSM) on hepatic hemodynamics]

The effect of intra-arterial infusion of degradable starch microspheres (DSM) on hepatic arterial blood flow was measured using a transit-time ultrasonic blood flow meter. Before the infusion of DSM, the mean hepatic arterial flows were 316 +/- 79 ml/min. After infusion, the mean flows decreased to 43 +/- 86 ml/min (86%). RI-angiography using 99mTc-macroaggregated albumin (MAA) was performed to measure hemodynamic changes in the liver. T/N ratio of 99mTc-MAA accumulation was increased from 0.37 to 0.62. Based on the peripheral MMC blood levels after combined infusion with DSM and MMC, the mean AUC with MMC plus DSM was decreased to 55% of that of AUC with MMC alone. These results show that combined use of DSM is effective for intra-arterial chemotherapy against the hepatic cancer.

[Clinical evaluation of intraperitoneal hyperthermic perfusion in far-advanced gastric cancer]

Nineteen far-advanced gastric cancer patients, including peritoneal dissemination, underwent surgical treatment followed by intraperitoneal hyperthermic perfusion (IPHP). Seven of them had cancerous ascites, 5 had ovarial metastasis, and in 7 the primary tumor extended to the adjacent organs. Postoperatively, ascitic effusion was absent after IPHP, and all patients were discharged. The survival of the IPHP group was compared with that of 27 advanced gastric cancer patients with serosal invasion (control group), who underwent gastrectomy without IPHP. In the IPHP group, the average and 50% survival was 400 and 520 days, respectively, and 1-year survival rate was 73.3%, against 273 days, 250 days, and 31.8%, respectively, in controls. The survival rate for the IPHP group was statistically better than that of the control group (p less than 0.01). In patients with peritoneal dissemination, the average survival and 50% survival for the IPHP group was 396 and 380 days, respectively, and 1-year survival rate was 62.5%, against 204 days, 170 days, and 16.6%, respectively, in controls. Based on these results, IPHP was suggested to be effective for gastric cancer with serosal invasion, especially with peritoneal dissemination.

Pharmacokinetic analysis in intraperitoneal hyperthermic chemotherapy of far-advanced gastric cancer patients

The pharmacokinetics of mitomycin C (MMC) has been evaluated in 10 far-advanced gastric cancer patients by means of an intraperitoneal hyperthermic perfusion (IPHP) using MMC to prevent and/or treat peritoneal dissemination. Further, misonidazole (MIS), which was used as a thermosensitizer, also was evaluated. The IPHP was performed for 120 min right after surgical procedure, using a closed-circuit with an inflow perfusate temperature from 46.3 approximately 47.5 degrees C and an outflow temperature of 44.0 approximately 46.0 degrees C. The MMC level in the perfusate was 10 micrograms/ml at the onset of IPHP and thereafter decreased to 1.7 +/- 0.4 micrograms/ml minutes later. The average AUC (area under the curve) in the perfusate was 3.3 micrograms/ml during the IPHP. The MMC level in the peripheral blood was 0.15 +/- 0.04 micrograms/ml 30 min after start of the IPHP and increased to 0.18 +/- 0.05 micrograms/ml at the end of IPHP. Additionally, the MIS level in the peripheral blood was 64.7 +/- 10.3 micrograms/ml 60 min after the IPHP, 60.6 +/- 9.2 micrograms/ml at 120 min, and then decreased to 32.8 +/- 10.3 micrograms/ml at 12 hours after IPHP. The AUC was calculated as being 975 micrograms.hr/ml. Again, the level in the portal vein blood was calculated from the peritoneal permeability and the peripheral blood level of the drug. From data, it was concluded that the perfusate and portal vein blood level of MMC, the peripheral blood level of MIS, as well as the perfusate temperature, are important in providing a favorable, safe, antitumoral treatment.

[Pharmacokinetic analysis in intraperitoneal hyperthermic perfusion using mitomycin C in far-advanced gastric cancer]

Postoperative intraperitoneal hyperthermic perfusion (IPHP) using MMC was performed with marked success on 15 gastric cancer patients with peritoneal dissemination or serosal invasion (first surgery group) and on 5 recurrent gastric cancer patients with ascitic retention (recurrent cancer group), and the MMC concentrations was studied in the perfusate and circulating blood. The perfusate contained MMC 10 micrograms/ml at the onset of IPHP, except one recurrent case of 20 micrograms/ml, and IPHP was performed for 120 minutes except in one case given 20 micrograms/ml of MMC. There was little difference in the hepatorenal functions and perfusate temperatures between the first surgery group and the recurrent cancer group. The drug levels were measured by HPLC method with minimal assay levels of 2 ng/ml. Perfusate drug levels in the first surgery group reduced by half at 12 minutes after the start of IPHP, whereas in the recurrent cancer group, they decreased by half about 60 minutes later. Perfusate drug levels in the first surgery group decreased twice as rapidly as in the recurrent cancer group. The area under the curve (AUC) and average drug levels in the first surgery group were 7,900 micrograms.hr/l and 3.3 micrograms/ml, respectively, and those in the recurrent cancer group were 12,620 micrograms.hr/l and 5.3 micrograms/ml, respectively. On the other hand, the drug levels in peripheral blood were almost the same between the two groups. These data suggest that although recurrent gastric cancer is well suited for IPHP because of high AUC, it is worthwhile performing IPHP combined with surgery for gastric cancer with peritoneal seeding, with due consideration for AUC of 7,900 micrograms.hr/l and the average drug level of 3.3 micrograms/ml.

Clinical trial with surgery and intraperitoneal hyperthermic perfusion for peritoneal recurrence of gastrointestinal cancer

To treat six patients with peritoneal recurrence after radical operation for gastrointestinal cancer, an intraperitoneal hyperthermic perfusion (IPHP), combined with surgical resection of recurrent tumors, intestinal by-pass anastomosis, or both, was carried out. Immediately after complete resection of the intraperitoneal recurrent tumors, a 2- to 3-hour IPHP was performed under hypothermic general anesthesia at about 32 degrees C, using a perfusate containing 10 micrograms/ml or 20 micrograms/ml of mitomycin C (MMC) warmed at the inflow temperature of 46.6 degrees C to 46.9 degrees C. The apparatus used for IPHP was designed for intraperitoneal perfusion as a closed circuit. Although five of the six patients had a malignant peritoneal effusion at the time of admission, the effusion disappeared soon after IPHP, and no cancer cell was present in the lavage from Douglas' pouch. The other patient had a recurrent tumor at the anastomotic region after low anterior resection for rectal cancer and complete resection of the recurrent tumor, combined with IPHP, was carried out. One patient with a recurrent gastric cancer died of hepatic metastasis and cancerous pleuritis 5 months after this treatment, and the other five are in good health 12.8 +/- 5.1 months after IPHP. On the other hand, five patients with intra-abdominal recurrent gastric cancer, who received only surgical treatment within the same period of time, died 3.0 +/- 2.1 months after the surgery. Postoperatively, in the six patients with IPHP, transitory hepatic dysfunction, hypoproteinemia, and thrombocytopenia occurred. These results show that IPHP using MMC combined with surgery is a safe, reliable treatment for patients with peritoneal recurrence of gastrointestinal cancer.

[Polarographic analysis of tumor tissue oxygen tension after hyperthermia combined with misonidazole]

For the purpose to analyse the influence of a thermosensitizing drug, misonidazole (MIS), on tissue oxygen tension (TpO2), TpO2 in human gastric cancer tissue (H-23) was measured by a polarographic method. MIS, 500 mg/kg, was given i.p. and then the heat treatment was done in a water bath at 43.5 +/- 0.1 degrees C for 23 minutes. A second treatment was performed to develop thermotolerance at the following intervals: 24 hours, 72 hours, 5 days, and 7 days. Tumor doubling time was shortest at 72-hour interval, i.e., the maximal thermotolerance of the tumor developed at 72-hour interval, whereas the tumor doubling time in case of combined use of MIS was shortest at 24-hour interval. TpO2 in the 72-hour interval treatment decreased soon after hyperthermia, and returned to a pre-heated value 3 hours after, whereas in the other 3 treatments the recovery time was 6 to 12 hours. On the other hand, in 24-hour interval of the combined use of MIS, the post-thermal value of TpO2 was about a half of the pre-thermal value and recovered 24 hours after. In the 5- and 7-day interval treatments, TpO2 declined notably and did not return to the pre-thermal value during 24 hours. These data suggest that the thermo-sensitizing effects of MIS were brought about by prolonged and extreme decrease in TpO2.

Thermotolerance of xenografted human gastric cancer

To compare the thermotolerance in vivo of two human gastric cancers with different doubling times, the xenografted tumors were warmed twice at 43.5 +/- 0.1 degree C in a water bath for 20 minutes at a predetermined interval. In the tumors with doubling times of 5.2 and 10.9 days, a 7-day interval heat treatment resulted in a prolongation in tumor tripling times by 156 per cent and 132 per cent, respectively, compared with a single heat treatment for 40 minutes. On the contrary, two heat treatments given at intervals of 3 to 5 days had a short tumor tripling time, compared to that of the 40-minute single treatment. Thus, the thermotolerance of these human gastric cancers gradually increased to a maximum within a 3- to 4-day interval and disappeared completely after a 7-day interval. These results indicate that the times required to reach maximal thermotolerance in these human gastric cancers were longer than those previously demonstrated for human and rodent cancer cell lines in vitro. The development and decay of thermotolerance in these human gastric cancers need to be considered in the design of multiple-fractionated regimens.

[The relationship between thermotolerance and the tissue oxygen tension in human gastric cancer tissue]

To study the relationship between thermotolerance and post-thermal phenomenon, tumor pO2 (TpO2) in xenoplanted gastric cancer tissue (H-23) has been measured by a polarographic method. The heat treatment was done in a water bath at 43.5 +/- 0.1 degrees C for 23 minutes. In order to produce thermotolerance, the second treatment was carried out at an interval of 24 hours, or, alternatively at 72 hours, or at 5 days or at 7 days. The thermotolerance of the H-23 tumor reached its maximum at the 72 hour-interval and was seen to disappear completely at 7 days. The TpO2 in the H-23 tumor decreased immediately after a single heat treatment and returned to its pre-treated value after 10 hours. In cases of the second heat treatment, the 72-hour interval group returned to its pre-treated value in 2-6 hours, whereas the 24-hour, 5-day, and 7-day interval groups showed a longer recovery time. The relationship between thermotolerance and TpO2 recovery was inverse at r = -0.858 and p = 0.035. Thus, our study suggests that not only is the thermotolerance affected by the alteration of the intra-cellular components, but also by the post-thermal changes in the tumor vessels.

[Extended treatment for gastric cancer patients with peritoneal seeding]

Fourteen patients with far-advanced gastric cancer were treated surgically followed by intraperitoneal hyperthermic perfusion (IPHP) with mitomycin C (MMC) and misonidazole (MIS), a thermosensitizing drug. Immediately after extensive resection of the abdominal tumors, a 2-hour IPHP was performed at the inflow temperature 47.4 +/- 0.5 degrees C and at the outflow temperature 45.3 +/- 0.5 degrees C, using equipment designed for treatment of cancerous peritoneal seeding, as a closed circuit, and under hypothermic general anesthesia at 31.2 +/- 0.5 degrees C. In 6 of the 14 patients, cancerous ascites was absent after IPHP. Repeated cytologic examination of the lavage from pelvic cul-de-sac were negative, in all cases. The postoperative courses were uneventful except for 2 patients, in whom slight leakage occurred. All patients were discharged, and 4 in the 14 patients died of recurrence in the liver, abdominal and/or pleural cavities 8.8 +/- 2.1 months after IPHP. The remaining 10 are in good health 12.1 +/- 3.1 months after IPHP. Transient hepatic dysfunction and hypoproteinemia occurred after hyperthermia in all cases. This extensive surgery combined with IPHP using MMC and MIS was well tolerated and is a safe anti-tumor treatment for gastric cancer with peritoneal dissemination. Neurotoxicity due to MIS was nil.

[Repeated intra-arterial chemotherapy combined with mitomycin C and degradable starch microspheres in inoperable metastatic hepatic cancer]

Intra-arterial chemotherapy combined with mitomycin C (MMC) and degradable starch microspheres (DSM) was prescribed repeatedly for 14 patients with inoperable hepatic metastasis. This intra-arterial treatment was repeated 2.7 times on the average. The average dose of DSM and MMC in a single infusion was 685 +/- 201 mg and 13.8 +/- 3.8 mg, respectively. To analyse the degradation time of DSM, MMC concentrations in the peripheral blood were measured by HPLC method. RI-angiography using 99mTc macroaggregated albumin(MAA) was performed to estimate the hemodynamic changes in the liver. Antitumor efficacy was evaluated in terms of tumor regression measured by CT scan. An objective tumor response was observed in 9/14 patients(64.2%): CR 1/14; PR 6/14; MR 2/14. Elevated CEA levels were decreased in 11/12 patients (91.7%). Based on the peripheral MMC blood levels after combined infusion with DSM and MMC, an occlusion of intrahepatic vessels with DSM continued at least for 30 minutes. Again, RI-angiography with 99mTc-MAA plus DSM revealed the increased accumulation in the tumor, compared to 99mTc-MAA only. Side effects possibly attributable to DSM were observed in 14/38 treatments, though they were slight and temporary. Thus, these results indicate that this combined intra-arterial infusion of DSM and MMC achieve, higher regional selectivity.

Intraperitoneal hyperthermic perfusion combined with surgery effective for gastric cancer patients with peritoneal seeding

Fifteen patients with far-advanced gastric cancer were given surgical treatment followed by intraperitoneal hyperthermic perfusion (IPHP) with mitomycin C (MMC) and misonidazole (MIS), a thermosensitizing drug. Immediately after extensive resection of the abdominal tumors, a 2-hour IPHP was performed at the inflow temperature of 44.7 to 48.7 C, using equipment designed for treatment of cancerous peritoneal seeding as a closed circuit, and under hypothermic general anesthesia at 30 to 31 C. In nine of the 15 patients with peritoneal seeding and/or ascites, cancerous ascites was absent after this treatment. In all cases, repeated cytologic examinations of the lavage from Douglas's pouch were negative. The postoperative courses were uneventful except for Patients 1 and 10, in whom slight leakage occurred. All patients were discharged and are in good health at the time of this writing, 7.2 +/- 4.6 months after the treatment. The Case 4 Patient recently died in a traffic accident. In all patients, transient hepatic dysfunction and hypoproteinemia occurred after the operation. This extensive surgery combined with IPHP using MMC and MIS was well tolerated and is a safe antitumor treatment for gastric cancer with peritoneal dissemination. Neurotoxicity due to MIS was nil.

Enhancement of hyperthermochemotherapy for human gastric cancer in nude mice by thermosensitization with nitroimidazoles

Hyperthermia for human gastric cancer xenotransplanted into the hindlegs of nude mice was performed to determine whether misonidazole (MISO) or metronidazole (MTR), derivatives of nitroimidazole, would intensify the antitumour effects of hyperthermia only, or combined with mitomycin C (MMC). MISO, MTR and MMC were given i.p. at doses of 500 mg kg-1, 500 mg kg-1 and 2.0 mg kg-1 respectively, and MISO or MTR was administered 45 min before MMC. Hyperthermia was applied twice at 48 h intervals, by means of a water bath at 43.5 +/- 0.1 degrees C for 23 min. Tumour tripling times following heat alone, MTR plus heat, and MISO plus heat were about 6.7, 8.0 and 7.9 days respectively, compared with 4.6 days for the control, but tumour regression occurred in the heat plus MISO group only. Tumour tripling times for MMC plus heat, MMC plus MTR plus heat, and MMC plus MISO plus heat were 9.6, 11.6 and 17.1 days respectively, compared to 4.6 days for the control and 6.7 days for heat alone. These data suggest that the antitumour activity of MMC plus MISO plus heat is an additive phenomenon.

[Chemosensitization with nitroimidazole to human gastric cancer transplanted into nude mice]

Combined chemotherapy for human gastric cancer Transplanted into nude mice has been performed to determine whether misonidazole (MIS) and metronidazole (MTR), derivatives of nitroimidazole, would enhance the antitumor activity of MMC. MTR, 500 mg/kg, MIS 500 mg/kg, and MMC 2.0 mg/kg were administered ip twice during a 48-hour interval. The antitumor efficacies of MMC only, MTR only, or MIS only were seen to be much the same as in the controls. The combined treatment with MMC and MTR surpassed the controls in antitumoral activity after the 12th day, whereas it did not surpass a regimen with MMC alone. The addition of MIS to MMC showed an enhanced antitumoral activity after the 10th day compared to the controls and, further, after the 10th day it exceeded the results of MMC only. Tumor tripling time in cases of MMC only, MTR only, MIS only, MMC plus MTR, and MMC plus MIS was 123, 132, 144, 144, and 178 hours, respectively, compared to 110 hours in the controls. Thus, these results suggest that MIS has a chemosensitizing activity under these conditions, while MTR has little activity.

[Antitumor efficacy of polyamine antimetabolites and mitomycin C under polyamine-free diet]

Treatment of nude mice xenografted with human gastric cancer was carried out by polyamine antimetabolites combined with mitomycin C (MMC) and polyamine-free diet. Polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) and ethylglyoxal-bis-guanylhydrazone (EGBG), were given ip in a daily dose of 1,000 mg/kg and 20 mg/kg, respectively, for 6 consecutive days. MMC 2.0 mg/kg was administered every other day. The polyamine-free diet was given from 4 days before start of the treatment through the end of the study. Although the tumor growth rate of the control group given polyamine-free diet was similar to that given normal diet, in the mice treated with EGBG, DFMO plus MMC, the antitumor effect in the polyamine-free diet group was superior to the normal diet group. In comparison with tumor growth suppression due to EGBG plus DFMO or MMC only, the polyamine-free diet group showed better result than the normal diet group to some extent. In mice treated with EGBG, DFMO plus MMC, tumor tissue spermine levels in the polyamine-free diet group were significantly depressed, compared to the normal diet group. Furthermore, marked suppression of DNA biosynthesis was observed in mice given EGBG, DFMO plus MMC together with the polyamine-free diet. These results suggest that combined treatments of polyamine antimetabolites and MMC revealed a marked enhancement of antitumor effects, under conditions of polyamine depletion, which may be responsible for the alteration in DNA structure.

The presence of an aberrant type of human chorionic gonadotropin in patients with gastric or colorectal cancer

Beta subunits of human chorionic gonadotropin (beta-hCG) and human chorionic gonadotropin-like substance (hCGLS) were measured radioimmunologically in the serum and malignant tissue from patients with gastrointestinal cancer. Since serum beta-hCG and hCGLS correlate closely to those in cancer tissues, it is assumed that these two gonadotropins originate from cancer tissues. The serum hCGLS levels in 54 patients with gastrointestinal cancer were significantly higher, when compared with the findings in 19 healthy volunteers and 10 peptic ulcer patients. The frequency of high levels of serum hCGLS accounted for 71 per cent of those with operable gastric cancer, 44 per cent of those with inoperable gastric cancer, 100 per cent of those with operable colorectal cancer, and 67 per cent of those with inoperable colorectal cancer. On the contrary, serum beta-hCG levels did not differ between the volunteers and the cancer patients. In the 17 sera and 15 cancer tissues assayed, beta-hCG did not correlate to hCGLS. Moreover, the high levels of beta-hCG in cancer patients occurred in only 1/14 (7.1 per cent) of the assayed serum, and in 5/14 (35.7 per cent) of the cancer tissue. The increased production of these two hCGs may result from neoplastic transformation of an unrestrained fetal genome responsible for hCG production during gestation. It is assumed that the increased producibility of a defective hCG, i.e., an aberrant hCG such as hCGLS, is characteristic of malignant tumors.

Gastric cancer with synchronous unresectable hepatic metastasis and a positive response to chemotherapy--report of two cases

We report herein the clinical events seen in two longterm survivors of gastric cancer with unresectable synchronous hepatic metastases. Partial gastrectomy was performed against the primary lesion and continuous intra-arterial infusion of anti-tumor drugs, followed by prolonged systemic antitumor drug treatment, were prescribed. A 43-year-old man with moderately-differentiated tubular adenocarcinoma had an uneventful course during his first 21 postoperative months. However, multiple liver metastases became manifest at 24 months and enlargement of the intrahepatic foci led to death 27 months after gastrectomy. A 51-year-old woman with moderately-differentiated tubular adenocarcinoma had an uneventful postoperative course and is now well with no signs of recurrence 6 years and 6 months after gastrectomy.

Contradictory antitumor efficacies produced by the combination of DNA attacking drugs and polyamine antimetabolites

The antitumor effects of two polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), when combined with cis-diamminedichlroplatinum (CDDP) or mitomycin C (MMC), were studied using human gastric cancer cells xenotransplanted into nude mice. DFMO 1000 mg/kg and MGBG 50 mg/kg were given intraperitoneally for 6 successive days, while CDDP 3 mg/kg or MMC 2 mg/kg was given every second day. Although DFMO and MGBG plus MMC did suppress the tumor growth, the combination with CDDP led to no suppression, and rapid growth occurred after the cessation of therapy. The inhibition of tumoral DNA biosynthesis and a decline in polyamine levels, were also not observed. The polyamine antimetabolites when used with CDDP did not produce the desired antitumor efficacy, even though the platinum concentration in the tumor tissue was high. On the contrary, however, DFMO and MGBG when combined with MMC did suppress tumor growth, inhibited DNA biosynthesis, and tissue polyamine levels were low. These results suggest that though CDDP and MMC belong to a similar category of DNA attacking, bifunctional alkylating agents, the findings of these two drugs are contradictory. Here, the mechanism of action no doubt plays a contributory role.

Enhanced antitumor efficacy with a combination of hyperthermochemotherapy and thermosensitization with polyamine antimetabolites in nude mice

In an attempt to enhance the antitumor effects of hyperthermochemotherapy, methylglyoxal-bis-guanylhydrazone (MGBG) and alpha-difluoromethylornithine (DFMO) were used in combination with hyperthermochemotherapy of 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a (ACNU) against human gastric cancer (ST-2) xenotransplanted into nude mice. After priming with DFMO and MGBG, ACNU was given ip and subsequently, a 23 minute-hyperthermia was carried out by placing the leg with the tumor into a water bath of a temperature of 43.5 +/- 0.1 degrees C. The second hyperthermic treatment was given in the same manner after 48 hours. MGBG and DFMO were administered for 4 successive days from the previous day of the first hyperthermia. In mice treated with DFMO plus MGBG, either tumor growth or tumor tripling time was much the same as in the control, while in mice given MGBG, DFMO plus heat, there was a diminution in tumor growth. Hyperthermia together with MGBG, DFMO plus ACNU brought about remarkable antiproliferative effects on ST-2 tumor growth, compared to three regimens with MGBG, DFMO plus heat, MGBG, DFMO plus ACNU, as well as ACNU plus heat. These data suggest that a combination of MGBG with DFMO leads to a favorable thermosensitization to the antitumor efficacy of ACNU.

[Combined efficacy of polyamine antimetabolites and cis-diamminedichloroplatinum]

The combined antitumor effects of the polyamine antimetabolites, alpha-difluoro methylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), with CDDP were studied using human gastric cancer cells xenotransplanted into nude mice. DFMO (1000 mg/kg in two divided doses) and MGBG (50 mg/kg) were given IP for six consecutive days from the time when the xenotransplanted tumor weighted about 100 mg, and CDDP (3.0 mg/kg) was given IP every other day from the same time. Animals treated with DFMO plus MGBG with or without CDDP as well as with CDDP only displayed suppressed tumor growth, compared to untreated mice. In mice treated with these three drugs, however, tumor growth was rather rapid compared to those treated with CDDP only, although tumoral CDDP levels in animals given DFMO, MGBG and CDDP were higher than those given CDDP only. When DFMO, MGBG and CDDP or DFMO and MGBG were administered, tumoral spermidine and spermine levels decreased markedly. On the other hand, tumor DNA biosynthesis in the CDDP only group dropped markedly 24 hours after the termination of therapy. These results suggest that an alteration in the DNA structure caused by polyamine deficiency may prevent cross-link formation in DNA by CDDP.

[Combined therapy of polyamine antimetabolite and nitrosourea in human gastric cancer]

Antitumor therapy using the polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), combined with ACNU was studied in human gastric cancer xenotransplanted into nude mice. DFMO 1,000 mg/kg (in two divided doses) and MGBG 50 mg/kg were given i.p. for 6 successive days from the time when the xenotransplanted tumor weighed about 100 mg, and ACNU 20 mg/kg was given i.p. every other day from the same time. Antitumor efficacy was assessed by the time course of tumor weight as well as of DNA biosynthesis and polyamine levels in tumor tissue. Tumor weight was estimated using Battelle's Columbus Institute protocol and DNA biosynthesis was assayed biochemically by 3H-TdR injection at a prescribed interval after termination of therapy. Furthermore, tumoral polyamine levels were assayed by HPLC. This three-drug regimen showed a favorable antitumor effect, compared to those of the other two therapies with DFMO plus MGBG as well as ACNU only. These data suggest that this combined regimen may have a synergistic efficacy judging from the action mechanisms of these three drugs.

Combined therapy of polyamine antimetabolites and antitumor drugs for human gastric cancer xenotransplanted into nude mice

Antitumor therapies using polyamine antimetabolites combined with 1-(4-amino-2-methyl-5-pyrimidyl)methyl-3(2-chloroethyl)-3-nitrosourea (ACNU) or fluorinated pyrimidines for human gastric cancer xenotransplanted into nude mice were studied to determine inhibiting post-therapeutic regrowth of the tumor after cessation of antitumor treatments with polyamine antimetabolites alone. ACNU 20 mg/kg, fluorinated pyrimidine, 5-FU 52.8 mg/kg and 5'-deoxy-5-fluorouridine (5'-DFUR) 100 mg/kg as well as polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) 1000 mg/kg and methylglyoxal-bis-guanylhydrazone (MGBG) 50 mg/kg were given intraperitoneally for 5 successive days. When DFMO and MGBG were combined with ACNU, the post-therapeutic regrowth was definitely inhibited, while combined treatments with 5-FU or 5'-DFUR did not inhibit the regrowth. Post-therapeutic DNA biosynthesis was suppressed in mice given DFMO, MGBG plus ACNU. On the contrary, in mice treated with DFMO, MGBG plus 5-FU or 5'-DFUR, suppression of DNA biosynthesis was not observed. Tumor tissue spermine levels in the DFMO, MGBG plus 5-FU or 5'-DFUR group remained unchanged, compared to those in the DFMO + MGBG group. In mice given DFMO, MGBG plus ACNU, however, spermine levels were markedly depressed; and the ACNU alone depressed also the tissue spermine levels. These different results between nitrosourea and fluorinated pyrimidines may relate to mechanisms of action of these antitumor drugs.

[Studies on hyperthermia by the use of a thermosensitizing drug]

Hyperthermic treatment using ACNU combined with a thermosensitizing drug, methylglyoxal-bis-guanylhydrazone (MGBG), was studied in human gastric cancer xenotransplanted into nude mice. In order to increase the intra-cellular MGBG content, intraperitoneal injection of alpha-difluoromethylornithine(DFMO) 1000 mg/kg was performed twice with an interval of 6 hours and 50 mg/kg of MGBG was given at the time of the second administration of DFMO. After 6 hours of MGBG administration, ACNU 20 mg/kg was given intraperitoneally and, subsequently a 23-minute hyperthermia was carried out in a water bath at 43.5 degrees C. After 48 hours a second hyperthermia was performed by the same method. Tumor weight was estimated using Battelle's Columbus Institute protocol and the inoculated tumors, which were extirpated 60 minutes after 3H-thymidine injection at a prescribed interval after cessation of hyperthermia, were assayed biochemically for the determination of DNA biosynthesis. In mice given ACNU, DFMO, MGBG plus heat, considerably superior results were obtained. Although the DFMO plus MGBG group was inferior in antitumor activity to the ACNU only or heat only group, the DFMO, MGBG plus heat group showed much the same antitumor effects, compared to the ACNU plus heat group. These data suggest that the thermosensitizing efficacy of MGBG may be applicable for clinical use.

[Anticancer treatment with a combination of antimetabolites of polyamine and pyrimidine]

A combined efficacy of the polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG) with two fluorinated pyrimidines was studied. DFMO, MGBG, 5-FU and 5'-deoxy-5-fluorouridine (5'-DFUR) were administered intraperitoneally to BALB/c nu/nu mice bearing xenotransplanted human gastric cancer for 5 consecutive days. Similar antitumor efficacies were observed in 3 groups treated with DFMO plus MGBG, DFMO, MGBG plus 5-FU as well as DFMO, MGBG plus 5'-DFUR. The two groups on 5-FU or 5'-DFUR alone did not differ in antitumor effects from the control, although reasonable levels of 5-FU were involved in tumor tissues. Hepatic and splenic 5-FU levels after 5-FU administration were significantly higher than those after 5'-DFUR, and marked decrease in mouse body weight was caused by 5-FU alone as well as 5-FU plus polyamine antimetabolites for 5 consecutive days. DNA biosynthesis and spermine levels in the tumor tissues on day 2 after cessation of the treatments dropped in 3 groups with DFMO plus MGBG, DFMO, MGBG plus 5'-DFUR as well as DFMO, MGBG plus 5-FU, while on day 6 there was little difference between the control and treated groups. These data suggest that combination with 5-FU or 5'-DFUR does not enhance the antitumor activity of polyamine antimetabolites by this experimental regimen.

Antitumor effects of two polyamine antimetabolites combined with mitomycin C on human stomach cancer cells xenotransplanted into nude mice

The antitumor effects of alpha-difluoromethylornithine (DFMO), methylglyoxal-bis-guanylhydrazone (MGBG) and mitomycin C (MMC), administered separately or in various combinations, on human stomach cancer cells xenotransplanted into BALB/c nude mice were studied using the protocol of Battelle's Columbus Laboratories (Ovejera et al., 1978). DFMO (1,000 mg/kg in 2 divided doses) and MGBG (50 mg/kg) were given intraperitoneally (i.p.) for 7 consecutive days from the time when the tumor weighed about 100 mg. MMC (2 mg/kg) was given i.p. every other day from the same time. Animals treated with either DFMO or MGBG alone displayed tumor growth comparable to that seen in untreated controls. In mice treated with DFMO plus MGBG with or without MMC, or in mice treated only with MMC, tumor growth was significantly lower than in untreated mice. In the group which received only combined DFMO/MGBG there was a rapid regrowth of the tumor after termination of therapy. Tumor putrescine levels decreased within 4 days following the administration of DFMO; however, spermidine levels did not decline with either DFMO or MGBG treatment even after 7 days. When combined DFMO/MGBG was given, there was a significant decline in spermidine levels 7 days after the initiation of treatment. In contrast, when MMC alone was administered, putrescine and spermidine levels in the tumor did not differ from those in control mice. Spermine decreased markedly in tumor with the combined administration of DFMO/MGBG as well as with combined DFMO/MGBG/MMC, but decreased only slightly when MMC alone or MMC plus either DFMO or MGBG was administered. By the 7th treatment day, DNA biosynthesis in the tumor had dropped markedly in all groups except those receiving DFMO or MGBG alone.

Effects of intra-arterially infused biodegradable microspheres containing mitomycin C

We prepared biodegradable microspheres containing about 5% mitomycin C (MMC) and of 45 +/- 8 microns in diameter. These preparations were infused into the rat hepatic artery as a preclinical model of intra-arterial infusion treatment for patients with inoperable hepatic tumor. The leaked MMC levels in the hepatic vein decreased below the assay limitation 2 hours after conventional MMC injection, whereas in the case of MMC microsphere the leaked drug levels were maintained at almost the same concentration for over 2 hours after infusion. The entrapped period of MMC microspheres within the hepatic artery was at least 2 weeks, and the necrobiotic foci due to antitumor effects of the condensed MMC released from the microspheres were observed in the area fed by these entrapped arterioles. This phenomenon was never observed in the case of conventional MMC and placebo microspheres. Intra-arterial infusion of MMC microspheres may be a promising clinical treatment for patients with malignant hepatic tumor.

[Experimental hyperthermo-chemotherapy for human gastric carcinoma transplanted in the nude mice]

Human gastric carcinomas serially xenotransplanted into BALB/c nu/nu mice were treated by hyperthermo-chemotherapy with mitomycin C (MMC). The antitumor efficacy was assessed by both single and double treatments of 25-minute hyperthermia (43.5 degrees C) and/or 2.0 mg/kg of MMC (ip). Tumor weight was estimated using Battelle's Columbus Laboratories protocol. To assess DNA biosynthesis in the tumor cells, the xenotransplanted tumors were excised at prescribed times after these treatments 60 minutes after 3H-thymidine injection (ip), and were examined microscopically. In the group treated twice by hyperthermo-chemotherapy marked growth inhibition and microscopic damage of the tumors were observed, while such features were not recorded in groups treated twice by hyperthermia only and chemotherapy only, nor in groups given single hyperthermo-chemotherapy, or hyperhermia and chemotherapy. In the single-treated groups, DNA biosynthesis was remarkably inhibited by hyperthermo-chemotherapy over 24 hours. The present results suggest that repeated treatments of hyperthermo-chemotherapy with MMC may be effective in the treatment of human gastrointestinal cancer.

[Combined therapy with polyamine biosynthesis inhibitors and mitomycin C]

An attempt was made to analyse tumor growth after cessation of combined therapy with the polyamine biosynthesis inhibitors, alpha-difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), as well as mitomycin C (MMC). DFMO 1000 mg/kg, MGBG 50 mg/kg and/or MMC 2 mg/kg were given intraperitoneally to BALB/c nu/nu mice xenotransplanted human gastric cancer, and its growth as well as DNA biosynthesis were measured daily, after cessation of these combined treatments. Histological observation of the tumor was also performed by hematoxylin-eosin staining. The combination with DFMO and MGBG stunted tumor growth during the treatment, but 3 days later its growth and DNA biosynthesis were accelerated distinctly. MMC injection halted tumor growth, and 5 days after termination of MMC injection its growth rate and DNA biosynthesis almost completely recovered. The microscopic findings on the 4th day after termination of MMC injection were similar to those of DFMO + MGBG treatment. The combination DFMO, MGBG and MMC suppressed not only tumor growth during the treatment, but also tumor growth and DNA biosynthesis over 7 days. The histologic observation 4 days later revealed extensive damage.

[Experimental studies on hepatic cancer chemo-embolization]

Mitomycin microspheres (MMC MS), which contain about 5% of MMC and have an average diameter of 45 +/- 8 microns, were administered into the rat hepatic artery in a preclinical study on antitumor treatment for human hepatic cancer. Plasma GOT and GPT activities increased markedly 24 hours after MMC MS injection; they decreased to within the normal range within 3 days of the injection. Hepatic necrobiosis was observed in the area adjacent to the hepatic arterioles containing MMC MS, but was not observed in rats injected with placebo microspheres. The hepatic vein blood of MMC MS treated rats contained a markedly high level of MMC, compared to rats treated in the conventional fashion with MMC. Furthermore, MMC MS remained within hepatic arterioles for over 3 weeks.

[Combined antitumor therapy with polyamine biosynthesis inhibitors and mitomycin C]

A combined effect of the polyamine biosynthesis inhibitors, alpha-difluoromethylornithine (DFMO) and methyglyoxal-bis-guanylhydrazone (MGBG) with mitomycin C (MMC) was studied. DFMO, MGBG and MMC were given intraperitoneally to nude mice xenotransplanted human gastric cancer. This new combination of the three drugs resulted in the complete halt of the xenotransplanted tumor growth and marked decline of spermine levels in the tumor tissues. The other treatments with DFMO and MGBG as well as MMC alone were inferior to this new combined therapy in suppression in both tumor growth and tissue spermine level. These data suggest that this new combined treatment be effective against human gastric cancer.

[Antitumor effects of polyamine synthesis inhibitors based on major premise of treatment for human malignant tumor]

The polyamine synthesis inhibitors--alpha-difluoromethylornithine (DFMO) and methylglyoxal bis (guanylhydrazone) (MGBG)--were put to antitumor tests based on the premise of treatment for human gastrointestinal cancer. The both drugs were administered intraperitoneally to BALB/c nude mice xenoplanted human gastric cancer for 10 consecutive days. Both marked antitumor effects and side effects were observed in mice treated at the dosage of DFMO 500 mg/kg/day and/or MGBG 50 mg/kg/day and/or MGBG 30 mg/kg/day brought about significant antitumor effects as well as less side effects. Microscopic observation revealed antitumor actions of these drugs as cytostatic rather than cytocidal. Tumor regrowth after the termination of this combined treatment, however, was noticed. Judging from these data, the both drugs may be effective against human gastrointestinal cancer with minor side effects.