Targeting immunotherapy using the avidin-biotin system for a human colon adenocarcinoma in vitro.

A new method of targeting immunotherapy using the avidin-biotin system in vitro was investigated. Both an anti-carcinoembryonic antigen monoclonal antibody (anti-CEA MAb) and an anti-cancer drug, neocarzinostatin (NCS), were biotinylated. A human colon adenocarcinoma cell line (LoVo) was immunized with biotinylated anti-CEA MAb; avidin was added, and the cell line was incubated with various concentrations of biotinylated NCS for either 72 h or 7 min. In the incubation for 72 h, the IC50 was similar (approximately 0.45 microgram/ml) for biotinylated NCS for LoVo cells immunized with biotinylated anti-CEA MAb and those without immunization. In the incubation for 7 min, the IC50 (concentration producing 50% cytotoxicity) of biotinylated NCS for LoVo cells immunized with biotinylated anti-CEA MAb (0.35 microgram/ml) was five times less than that of non-immunized LoVo cells (1.8 micrograms/ml). Thus the present system has the potential to reduce the dosage of anti-cancer drugs needed, and this strategy seems likely to be a valuable clinical tool in targeting immunotherapy.

Intestinal absorption of lithocholate and its sulfate and glucuronide in rats.

The absorption of lithocholate and its sulfate and glucuronide in rat jejunum and terminal ileum was studied. Tracer amounts of radiolabelled bile acids were administered to the ligated intestinal segments, and their absorption was monitored by biliary excretion through a bile duct catheter. Absorption of lithocholate was faster in the terminal ileum than in the jejunum. Although the sulfation reduced lithocholate absorption in the jejunum, it did not affect lithocholate absorption in the terminal ileum. This was due to the Na+-dependency of ileal absorption of lithocholate-sulfate assessed by perfusion studies. In contrast, the glucuronidation markedly reduced lithocholate absorption both in the jejunum and the terminal ileum. These findings indicate that the glucuronidation is more effective than sulfation in detoxifying lithocholate as far as the prevention of its intestinal absorption is concerned.

Inhibition of hepatic metastases of human colon cancer in nude mice by a chimeric SF-25 monoclonal antibody.

BACKGROUND/AIMS: Hepatic metastasis is one of the most serious complications of human colon cancer. A murine-human chimeric SF-25 monoclonal antibody was prepared, and this construct recognizes a cell surface antigen highly present in human colon adenocarcinoma. METHODS: This study determined if the chimeric SF-25 monoclonal antibody inhibits the outgrowth of hepatic metastases of human colon adenocarcinoma using an athymic nude mouse model. RESULTS: A single intravenous injection of chimeric SF-25 monoclonal antibody significantly inhibited the outgrowth of 5- and 7-day hepatic micrometastases (P = 0.0001 and 0.004, respectively, vs. untreated) and improved the survival of the animals. No detectable tumor was found in the liver when mice were treated by multiple injections of the antibody immediately after tumor cell grafting into the portal vein. In contrast, F(ab')2 fragments did not show antitumor effects, and the administration of natural killer cell or macrophage depleting agents (anti-asialo GM1 antibody and carrageenan, respectively) substantially inhibited the antitumor effects of chimeric SF-25 monoclonal antibody in vivo. CONCLUSIONS: Chimeric SF-25 monoclonal antibody inhibits growth of hepatic metastasis of human colon cancer, and cell-mediated host immune mechanisms seem to be important for its in vivo antitumor activity.

Metaiodobenzylguanidine: evaluation of its potential as a tracer for monitoring doxorubicin cardiomyopathy.

We evaluated alterations in cardiac adrenergic neuron activity and progression of left ventricular dysfunction in comparison with the severity of structural changes using a rat model of adriamycin cardiomyopathy. Rats were treated with adriamycin (2 mg/kg s.c. once a week) for 6, 7, 8 and 9 wk. Accumulation of 125I-metaiodobenzylguanidine (MIBG) 4 hr after intravenous administration was determined and left ventricular ejection fraction (LVEF) was calculated from gated blood-pool images. H & E and Masson-Trichrome stained specimens of the myocardium were examined by light microscopy. Histopathologic examination demonstrated dose-dependent myocyte damage, although there were no differences between the 8-wk and 9-wk groups. LVEF did not differ between controls and the 6-wk group (81.3% +/- 5.5% versus 82.1% +/- 4.8%, p = ns). LVEF began to decrease slightly in the 7-wk group (75.0% +/- 5.7%, p < 0.05) and showed a remarkable decrease in the 8-wk group (53.7% +/- 2.6%, p < 0.001). In the 9-wk group, LVEF diminished to 47.9% +/- 3.1% (p < 0.001), accompanied by massive pleural effusions and ascites. MIBG accumulation in the heart (%ID/heart) significantly and progressively diminished; 1.42% +/- 0.15% in the 6-wk group, 1.06% +/- 0.16% in the 7-wk group, 0.77% +/- 0.13% in the 8-wk group and 0.34% +/- 0.11% in the 9-wk group, respectively p < 0.001, compared to controls (1.99% +/- 0.30%). These results demonstrate that MIBG accumulation in the heart showed a greater and more linear dose-dependent decrease than LVEF. Furthermore, MIBG uptake was significantly reduced in the 6-wk group where only mild myocyte damage (isolated vacuolation or myofibrillar loss) was observed. Thus, MIBG may be a sensitive biochemical marker of adriamycin cardiomyopathy.

Serial course of left ventricular function, perfusion and fatty acid uptake in the cardiomyopathic hamster.

To determine the relationship of metabolic and perfusion changes to alterations in ventricular function in the course of cardiomyopathy, we performed serial measurements of ejection fraction, myocardial perfusion, fatty acid uptake of 3-methyl-p[123I]-phenyl-pentadecanoic acid ([123I]3MPDA) and myocardial histology in Syrian hamsters genetically predisposed to the development of congestive cardiomyopathy (Bio T0-2) (n = 30) and normal age-matched control animals (Bio F1B) (n = 13). To obtain high-resolution information about the myocardium at the time of onset of the first noticeable decrease in ventricular function, a multitracer autoradiographic study using 99mTc-pyrophosphate, 201Tl and [14C]3MPDA was obtained at 90 days of age. Baseline ejection fraction recorded at 60 days averaged 60.3%; by 90 days, it decreased to 54.3% (p < 0.05), falling to 41.3% at 180 days (p < 0.01) and declining to 30% at the end of the study. A progressive increase in the extent of myocytolysis, fibrosis and calcification was seen in the histologic studies as the animals aged. The ratio of fatty acid-to-thallium uptake dropped from 0.51 +/- 0.09 to 0.45 +/- 0.11 (p < 0.01), which is in parallel with the reduction in ejection fraction. The thallium lung-to-heart ratio increased from 0.51 at 90 days to 0.59 at 270 days (p < 0.05), which corresponds to the worsening of cardiac function. The macroautoradiographic studies demonstrated slight uptake of pyrophosphate in the myopathic hamster hearts and minimal changes in the regional distribution of fatty acid compared to that of perfusion. We conclude that the decrease in ventricular function parallels the severity of myocytolysis and fibrosis. Although decreased fatty acid uptake was apparent at an early stage, the extent of the change is modest and is difficult to detect from external images.