Inhibition of tumor angiogenesis

Angiogenesis and Cancer Control: From Concept to Therapeutic Trial

Background

There is extraordinary interest in developing angiosuppressive agents for cancer treatment. Several new agents appear promising for the treatment of a variety of human cancers. Current concepts and new agents in clinical trials are the focus of this article. In particular, the introduction of a new treatment for human brain tumors is presented in detail, using an antiangiogenic agent, penicillamine, and depletion of an obligatory cofactor of angiogenesis, copper.

Methods

The explosive increase in literature on antiangiogenesis is reviewed using computerized search, findings presented at the recent national cancer and angiogenesis meetings. A specific protocol, NABTT 97-04, “Penicillamine and Copper Reduction for Newly Diagnosed Glioblastoma,” is presented as an example of angiotherapeutic drug discovery.

Results

A number of promising molecular approaches are being introduced to suppress tumor angiogenesis. Major categories of angiogenesis antagonists include protease inhibitors, direct inhibitors of endothelial cell proliferation and migration, suppression of angiogenic growth factors, inhibition of endothelial-specific integrin/survival signaling, chelators of copper, and inhibitors with specific other mechanisms. The preliminary results of early trials offer a glimpse into how antiangiogenesis therapy will be integrated into future care of the patient with cancer.

Conclusions

Thirty-five antiangiogenesis therapies are currently being evaluated in clinical trials. As we learn more about the fundamental mechanisms of angiogenesis, eg, the role of copper in growth factor activation, effective methods of cancer control will be implemented.

Allograft survival enhancement using doxycycline in alkali-burned mouse corneas

PURPOSE

To explore the inhibitory effects of doxycycline on allograft rejection in alkali-burned cornea beds.

METHODS

The corneas of BALB/c mice were injured using a 1 mol/l NaOH solution. Following the injury, the corneas from C57BL/6 mice were transplanted into the eyes of BALB/c mice after being randomized into three groups: allogeneic corneal transplantation (group A), topical use of doxycycline after allogeneic corneal transplantation (group B) and syngeneic corneal transplantation (group C). Corneal angiogenesis was examined using whole-mount immunofluorescence, and corneal inflammation was evaluated using inflammation index scoring. The immune rejection of the grafts was examined using a slit lamp. In addition, the expression of vascular endothelial growth factor A and interleukin-1β in the transplanted corneas was examined using a real-time polymerase chain reaction, immunohistochemistry and an enzyme-linked immunosorbent assay.

RESULTS

The outgrowth of the corneal blood vessels in the group A mice was faster than that in the group B and group C mice. The inflammation index levels were highest in the group A mice, intermediate in the group B mice and lowest in the group C mice. Vascular endothelial growth factor and the interleukin-1β protein and mRNA levels decreased dramatically in the group B mice compared with the group A mice (all p-values < 0.01). In addition, the mean survival time in the group B mice (27.00 ± 2.00 days) was significantly longer than that in the group A mice (11.67 ± 1.51 days; p < 0.05).

CONCLUSIONS

Doxycycline may have had a significant role in preventing corneal angiogenesis and inflammation in alkali-burned corneal beds, which resulted in higher allograft survival rates.

Minocycline chelates Ca2+, binds to membranes, and depolarizes mitochondria by formation of Ca2+-dependent ion channels

Minocycline (an anti-inflammatory drug approved by the FDA) has been reported to be effective in mouse models of amyotrophic lateral sclerosis and Huntington disease. It has been suggested that the beneficial effects of minocycline are related to its ability to influence mitochondrial functioning. We tested the hypothesis that minocycline directly inhibits the Ca(2+)-induced permeability transition in rat liver mitochondria. Our data show that minocycline does not directly inhibit the mitochondrial permeability transition. However, minocycline has multiple effects on mitochondrial functioning. First, this drug chelates Ca(2+) ions. Secondly, minocycline, in a Ca(2+)-dependent manner, binds to mitochondrial membranes. Thirdly, minocycline decreases the proton-motive force by forming ion channels in the inner mitochondrial membrane. Channel formation was confirmed with two bilayer lipid membrane models. We show that minocycline, in the presence of Ca(2+), induces selective permeability for small ions. We suggest that the beneficial action of minocycline is related to the Ca(2+)-dependent partial uncoupling of mitochondria, which indirectly prevents induction of the mitochondrial permeability transition.

Dynamic imaging of cancer growth and invasion: a modified skin-fold chamber model

The metastatic invasion of cancer cells from the primary lesion into the adjacent stroma is a key step in cancer progression, and is associated with poor outcome. The principles of cancer invasion have been experimentally addressed in various in vitro models; however, key steps and mechanisms in vivo remain unclear. Here, we establish a modified skin-fold chamber model for orthotopic implantation, growth and invasion of human HT-1080 fibrosarcoma cells, dynamically reconstructed by epifluorescence and multiphoton microscopy. This strategy allows repeated imaging of tumor growth, tumor-induced angiogenesis and invasion, as either individual cells, or collective strands and cell masses that move along collagen-rich extracellular matrix and coopt host tissue including striated muscle strands and lymph vessels. This modified window model will be suited to address mechanisms of cancer invasion and metastasis, and related experimental therapy.

Inhibition of experimental angiogenesis of cornea by various doses of doxycycline and combination of triamcinolone acetonide with low-molecular-weight heparin and doxycycline

PURPOSE

To evaluate the effect of topically administered doxycycline in various doses; the combination of triamcinolone acetonide and low-molecular-weight heparin (LMWH); and the combination of triamcinolone acetonide and doxycycline on experimental corneal neovascularization in rats.

METHODS

This project is the combination of 2 separate studies. First, the chemical cauterization of corneas in 36 eyes of 36 Long Evans male rats was performed by using silver nitrate/potassium nitrate sticks. Topical instillation of doxycycline at 0.05% (pH = 3.3), 0.1% (pH = 3.1), 1% (pH = 2.3), 2% (pH = 2.1), 2% (pH neutralized to 7.4), and normal saline continued for 7 days. Second, the chemical cauterization of the corneas in 24 eyes of 24 rats was achieved by application of silver nitrate/potassium nitrate sticks. Topical instillation of triamcinolone acetonide (10 microg/mL) and either LMWH (10 mg/mL) or doxycycline (10 mg/mL) was compared with normal saline treatment of 7 days. For both studies, the percent area of the cornea covered by neovascularization and scar in each group was calculated separately by using computer software on digital photographs. All corneas were evaluated histopathologically in study and control groups.

RESULTS

The mean percent area of corneal neovascularization determined in the eyes given doxycycline 0.05%, 0.1%, 1%, 2%, and 2% (pH neutralized) study groups and control groups was 69.8% +/- 18.0%, 64.5% +/- 14.0%, 56.4% +/- 20.8%, 54.8% +/- 6.0%, 36.2% +/- 4.3%, and 69.4% +/- 5.7%, respectively. The mean of percent area of neovascularization in the 2% doxycycline (pH neutralized) doxycycline group was significantly less than that of the control group and the <1% doxycycline concentrations (P < 0.05). The percent corneal neovascularization in the 2% (pH neutralized) doxycycline group was not significantly different from that of the 1% and 2% doxycycline groups (P < 0.05). There was no significant difference in percent area of corneal scar between control and study groups (P > 0.05). The mean percent area of corneal neovascularization in triamcinolone acetonide and LMWH, triamcinolone acetonide and doxycycline, and control groups was 2.35% +/- 4.42%, 9.42% +/- 6.8%, and 64.7% +/- 10.0%, respectively. The mean percent area of neovascularization in the triamcinolone acetonide plus LMWH or triamcinolone acetonide plus doxycycline groups was significantly different from that of the control group (P = 0.001 for both). There was no significant difference between study groups with regard to percent area of neovascularization or percent area of corneal scar between the control and study groups.

CONCLUSIONS

Topically administered combinations of triamcinolone acetonide plus LMWH or triamcinolone acetonide plus doxycycline had effects that contributed to efficient suppression of corneal neovascularization; these drugs were ineffective at similar concentrations used alone. Topically administered 2% (pH neutralized) doxycycline has antiangiogenic effects, which contributed to significant suppression on corneal neovascularization. This drug may be therapeutically beneficial in treatment of corneal neovascularization in clinical trials.

Inhibition of breast adenocarcinoma growth by intratumoral injection of lipophilic long-acting lathyrogens

Prevention of the formation of crosslinks and/or disintegration of already formed collagen fibrils in the tumor by known lathyrogens, beta-aminopropionitrile or D-penicillamine, may result in the weakening of tumor support, decreasing angiogenesis and promoting tumor regression. This paper reviews our studies with a single intratumoral injection of lipophilic lathyrogens and others, using a systemic administration to investigate the effect of both lathyrogens. Details of our experimental results are also given.

Inhibition by doxycycline of angiogenesis in the chicken chorioallantoic membrane (CAM)

Doxycycline, a tetracycline derivative, has many properties in addition to its antibiotic activity, including inhibition of matrix metalloproteinases (MMPs) and the ability to chelate divalent cations including Ca(2+). It has been shown to inhibit endothelial cell growth in vitro, and reduce the development of experimental tumours, especially bone metastasis in a model of breast cancer. We examined the effects of doxycycline on angiogenesis in the chicken chorioallantoic membrane (CAM) model, and showed that doxycycline will cause loss of the chorionic plexus in CAMs when applied at day 8 of incubation, and the duration of this inhibition was dose-dependent. Repeated doses prolonged the inhibition, but following removal of the doxycycline there was rapid recovery of the chorionic plexus. The effects of doxycycline are in part mimicked by the MMP inhibitor 1,10-phenanthroline, and more closely by the Ca(2+)-chelating agent EGTA. Doxycycline was equally effective in causing loss of the chorionic plexus by day 11 in CAMs, a time at which the blood vessels are established. Doxycycline has important potential as an antiangiogenic treatment. It is capable of inhibiting angiogenesis in an in vivo model, including the removal of comparatively mature endothelial cells. The response is sensitive to the dosing regimen and the effect is rapidly reversible.

Pressure ulcers in the chronically critically ill patient

All chronically critically ill patients are at high risk for development and progression of pressure ulcers. Constant surveillance including daily examination of the skin must be part of the care protocol. All pressure ulcers are chronic wounds that have an inherent, physiologic impairment to healing. As soon as a pressure ulcer develops, intervention should begin immediately, and a treatment plan should be determined. We believe that early intervention and appropriate treatment, guided by the paradigm we have described, can retard progression and promote healing [49]. Treatment decisions should be made within the context of the patient's overall care goals.

Tumor regression of B16F10 melanoma in vivo by prevention of neovascularization: study on theophylline

The aim of this study was to determine the effect of theophylline on neovascularization and tumor regression in murine B16F10 melanoma. Theophylline had no direct toxicity to host and significantly reduced (p < 0.001) tumor volume and neovascularization in B16F10 melanoma implanted murine model. The effect of theophylline on neovascularization was observed distinctly in histologic analysis. This effect is mediated, in part by blocking endothelial cell proliferation, thereby preventing neovascularization of the tumor. Further investigations with theophylline can elucidate the exact mechanism of action which characterize neovascularization activity.

Inhibition of cell proliferation, invasion, tumor growth and metastasis by an oral non-antimicrobial tetracycline analog (COL-3) in a metastatic prostate cancer model

Antibiotic forms of tetracycline exhibit antitumor activity in some tumor models. However, their low in vivo efficacy and associated morbidity limit their long-term application in cancer therapy. This report appraises the efficacy of doxycycline (DC) and non-antimicrobial, chemically modified tetracyclines (CMTs) against prostate cancer. Both DC and several CMTs inhibited prostate tumor cell proliferation in vitro. Some of the CMTs were significantly more potent than DC. One of the CMTs, 6-deoxy, 6-demethyl, 4-de-dimethylamino tetracycline (CMT-3, COL-3), was the most potent inhibitor (50% inhibition dose [GI(50)] < or = 5.0 ,microg/ml). Exposure of tumor cells to CMT-3 induced both apoptosis and necrosis. Mitochondrial depolarization and increased levels of reactive hydroxyl radicals were also observed in cells treated with CMT-3. Cell cycle arrest at the G(0)/G(1) compartment was observed in CMT-3- and DC-treated cells. DC and CMTs also inhibited the invasive potential of the tumor cells in vitro, from 10% (CMT-6) to >90% (CMT-3). CMT-3 and DC decreased matrix metalloproteinase (MMP)-2, tissue inhibitor of MMP (TIMP)-1 and TIMP-2 secretion in treated cultures and inhibited activity of secreted MMPs, CMT-3 was a stronger inhibitor. Daily oral gavage of DC and CMT-3 inhibited tumor growth and metastasis in the Dunning MAT LyLu rat prostate tumor. Decreases in tumor growth (27-35%) and lung metastases were observed (28.9 +/- 15.4 sites/animal [CMT-3-treated] versus 43.6 +/- 18.8 sites/animal [DC-treated] versus 59.5 +/- 13.9 [control]; p < 0.01]. A delay in tumor growth (27 +/- 9.3%, p < 0.05), reduction in metastases (58 +/- 8%) and decrease in tumor incidences (55 +/- 9%, CMT-3-treated) were also observed, when rats were predosed for 7 days. No significant drug-induced morbidity was observed in any of the animals. These results, along with a recently concluded clinical trial, suggest a potential use of CMT-3 as an oral, nontoxic drug to treat metastatic prostate and other cancers.

Inhibitory effect on expression of angiogenic factors by antiangiogenic agents in renal cell carcinoma

Since it has been widely recognised that renal cell carcinoma is refractory to standard therapies such as chemotherapy and radiotherapy, a new modality of treatment is needed. One of the potential alternative therapies for renal cell carcinoma may be inhibition of angiogenesis. In this study, we analysed the inhibitory effects of several potential agents on expression of angiogenic factors such as vascular endothelial growth factor and basic fibroblast growth factor, which are the main mediators in angiogenesis of renal cell carcinoma. We used medroxyprogesterone acetate, interferon-alpha, interferon-gamma, minocycline hydrochrolide and genistein, which are known to be antiangiogeneic. Northern blot analyses revealed that, among the five agents examined, genistein had a strong inhibitory effect on expression of vascular endothelial growth factor mRNA and basic fibroblast growth factor mRNA. Medroxyprogesterone acetate and interferon-alpha did not significantly decrease the level of either vascular endothelial growth factor mRNA or basic fibroblast growth factor mRNA. Interferon-gamma and minocycline had mild inhibitory effects on vascular endothelial growth factor mRNA and basic fibroblast growth factor mRNA expression. Genistein also inhibited both vascular endothelial growth factor mRNA and basic fibroblast growth factor mRNA expression after treatment with epidermal growth factor and hypoxia. These findings suggest that one of the mechanisms of the inhibition of angiogenesis by genistein is suppression of the expression of the angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor in renal cell carcinoma.

Low plasma levels of matrix metalloproteinase 9 permit increased tumor angiogenesis

Angiogenesis is essential for tumor growth and blocking this process might be a valid tool for the control of cancer growth. We showed previously that tumor angiogenesis in integrin alpha1-null mice is reduced compared to that of wild type animals and that over-expression of matrix metalloproteinase 9 (MMP-9) in the alpha1-null and consequent generation of angiostatin (an inhibitor of endothelial cell growth) from circulating plasminogen was implicated in the mechanism of tumor inhibition. Our findings suggested that secretion of excess MMPs generates inhibitors of endothelial cell proliferation, including but not necessarily limited to angiostatin, resulting ultimately in auto-inhibition of angiogenesis. Thus MMP inhibitors used as anti-tumor drugs might in fact cause a paradoxical increase in tumor angiogenesis and tumor growth. In order to determine whether MMP-9 expression was directly involved in the regulation of tumor growth, we specifically inhibited or enhanced MMP-9 synthesis in vitro and in vivo, and subsequently analysed primary endothelial cell proliferation and angiostatin synthesis, as well as tumor vascularization and development. We provide evidence that reduction of plasma levels of MMP-9 in either normal or integrin alpha1-null mice leads to decreased synthesis of angiostatin and consequent increased tumor growth and vascularization. In contrast, specifically enhancing MMP-9 expression in vivo caused a reduction in tumor vascularization. These findings are the opposite to other studies suggesting a pro-tumorigenic role for MMP-9, and may account for some of the recently observed failures of anti MMP therapy in tumor treatment.

Suppressive effect of irsogladine maleate on N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-initiated and glyoxal-promoted gastric carcinogenesis in rats

The modifying effect of irsogladine maleate (IRG) on N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-initiated and glyoxal-promoted gastric carcinogenesis was examined in male Wistar rats. Six-week-old rats were divided into ten groups. Groups 1 through 6 were given MNNG (100 mg/l in drinking water) for 25 weeks from the start of the experiment, whereas groups 7 through 10 received distilled water in the initiation phase as the vehicle treatment. Groups 1 and 8 were kept on the basal diet and distilled water throughout the experiment (55 weeks). Groups 2-8 were given 0.5% glyoxal in the drinking water for 30 weeks from 26th week of the experiment. Group 3 was fed the diet mixed with 100 ppm IRG for 25 weeks from the start of experiment. Groups 4 and 8 were fed the diet mixed with 100 ppm IRG for 30 weeks from 26th week of experiment. Groups 5 and 9 or 6 were given 100 or 25 ppm IRG containing diet, respectively throughout the experiment. Group 10 was given the basal diet and distilled water as the vehicle treated control. Tumors of upper digestive tracts (stomach and duodenum) were developed in groups: 1 (12/17 rats, 71%), 2 (11/12 rats, 92%), 3 (9/16 rats, 56%), 4 (5/12 rats, 42%), 5 (6/15 rats, 40%) and 6 (7/12 rats, 58%). High dose of IRG in initiation and/or promotion phase significantly reduced the incidence of tumors of the upper digestive tracts. The average numbers of the digestive tracts neoplasms in groups 3,5 and 6 given glyoxal and IRG were less than those in group 2 which received only glyoxal. These results suggest that IRG could be a preventive agent against the occurrence of neoplasms of the upper digestive tract.

In vivo antitumor effect of vascular targeting combined with either ionizing radiation or anti-angiogenesis treatment

PURPOSE

Interference with the tumor blood vessels through anti-angiogenesis or vascular targeting can indirectly suppress tumor growth. Vascular targeting of solid tumors, using tubulin-compromising agents, seems a promising and selective novel treatment. We aimed to evaluate the potential (hypothesis-based) benefit from combinations of vascular targeting using combretastatin A-4 phosphate (combreAp) with either ionizing radiation or anti-angiogenesis.

METHODS AND MATERIALS

Rhabdomyosarcoma tumor pieces were inplanted subcutaneously (s.c.) in the lower flank region of syngeneic adult WAG/Rij rats. Tumors were grown until different sizes and stratified for the various treatment groups: small (1-3 cm3), medium (3.1-7 cm3), and large (7.1-14 cm3). CombreAp was injected i.p.; injections of TNP-470 were s.c. in the neck area. Localized single-dose (8 Gy) irradiations of tumors were done under Nembutal anesthesia, always 1 day before a single combreAp (25 mg/kg) injection. The TNP-470 treatment (3 times 30 mg/kg in 1 week) started 1 day after a double (8 days interval between both) combreAp administration. Tumor responses were evaluated by the growth delay assay, and statistical significance of tumor growth change was computed.

RESULTS

Large tumors responded better to combreAp treatment given alone than did the smaller ones, confirming our previous data with this tumor model. Combining irradiation with combreAp also resulted in a tumor size-dependent growth delay. With small and medium tumor volumes, a similar response was measured after the combination treatment when compared with irradiation only. Large tumors, however, showed a strong (at least additive) increase of the growth delay with the combined therapy; the difference in tumor growth between the two treatment groups was very significant (p < 0.0001). m When TNP-470 was combined with combreAp, no significant lengthening of the growth delay, irrespective of the tumor size, was present with the applied schedule.

CONCLUSION

The current data show a significant advantage in the combination of combreAp with irradiation in rhabdomyosarcomas having a large size (7-14 cm3) at treatment. Such a benefit in tumor response was not observed with the smaller tumors, seemingly because irradiation as such was very effective. No significant gain in growth delay for any tumor size was observed when TNP-470, showing efficacy on its own specifically with tumors measuring <7 cm3, was added to the combreAp treatment. This presumably reflects only little angiogenesis during the first week of rhabdomyosarcoma regrowth after the combreAp treatment.

Vascular targeting of solid tumours: a major 'inverse' volume-response relationship following combretastatin A-4 phosphate treatment of rat rhabdomyosarcomas

Tumour-specific vascularisation may be therapeutically approached in two different ways: by antiangiogenic treatments specifically directed to dividing and migrating endothelial cells, or by agents that target principally the inadequate and ill-structured tumour vasculature. Combretastatin A-4 phosphate (combreAp), a recently synthesised prodrug (OXiGENE, Lund, Sweden), is a vascular targeting agent of the latter kind. We evaluated the effect of a single intraperitoneal (i.p.) combreAp injection on the growth of rhabdomyosarcomas syngeneic in WAG/Rij rats. Different tumour volume groups, ranging between 0.1 and 27 cm(3), were selected to assess the relationship between the size at treatment time and the response to combreAp. A double combreAp treatment (2x25 mg/kg) was investigated within the same overall aim: the relationship between growth delay and tumour size. Our results show that the systemic administration of combreAp induces a clear-cut differential growth delay in the solid rat rhabdomyosarcomas: with very large tumours (>/= 14 cm(3)), a 17.6-fold stronger effect was measured than with very small tumours (<1 cm(3)). This is the 'inverse' of the volume-response seen with the conventional therapeutic approaches (radiotherapy, chemotherapy or surgery). These combreAp antitumour responses were observed without treatment limiting systemic toxicity in the rats. With clinical digital subtraction angiography, using microsurgical cannulation of a major tumour draining vessel, and with histopathology, we demonstrate that growth delay is related to an early (within 3-6 h) and extensive breakdown of tumour blood vessels. The experiments involving a second injection also indicate a volume-dependent effect of combreAp in reducing the regrowth rate of small or large rhabdomyosarcomas. This significant differential volume-response obtained with 'selective' vascular targeting, stronger in larger tumours than smaller ones, suggests the potential of broadening the therapeutic window.

Antiangiogenic, antitumoural and antimetastatic effects of two distamycin A derivatives with anti-HIV-1 Tat activity in a Kaposi's sarcoma-like murine model

The antiangiogenic, antitumoural and antimetastatic effects of two novel sulphonic derivatives of distamycin A, PNU145156E and PNU153429, were studied in a Kaposi's sarcoma-like tumour model obtained by injecting nude mice with cells releasing extracellular HIV-Tat protein, derived from a tumour which developed in a BK virus/tat transgenic mouse. Both PNU145156E and PNU153429 were administered intraperitoneally every fourth day for three weeks at doses of 100 or 50 mg/kg of body weight respectively, starting one day after injecting the tumour cells. Both drugs delayed tumour growth in nude mice, preventing neovascularization induced by the Tat protein. PNU153429 also significantly reduced the number and size of spontaneous tumour metastases. Both effects on tumour growth and metastases were augmented by treating simultaneously nude mice with 7.5 mg/kg of body weight of minocycline given per os daily for four weeks starting four days after injecting the tumour cells. Neither acute nor chronic toxic side-effects were observed during the life span of treated nude mice. Due to their antiangiogenic and anti-Tat effects, these drugs are promising for the treatment of Kaposi's sarcoma in AIDS patients.

MMP inhibition in prostate cancer

Matrix metalloproteinases (MMPs) play a significant role during the development and metastasis of prostate cancer (CaP). CaP cells secrete high levels of MMPs and low levels of endogenous MMP inhibitors (TIMPs), thus creating an excess balance of MMPs. Established CaP cell lines that express high levels of MMPs frequently metastasize to the bone and the lungs. Drugs such as Taxol and alendronate that reduce cell motility and calcium metabolism reduce bony metastasis of xenografted CaP tumors. We tested several synthetic, nontoxic inhibitors of MMPs that can be administered orally, including doxycycline (DC) and chemically modified tetracyclines (CMTs) on CaP cells in vitro and on a rat CaP model in vivo. Among several anti-MMP agents tested, CMT-3 (6-deoxy, 6-demethyl,4-de-dimethylamino tetracycline) showed highest activity against CaP cell invasion and cell proliferation. Micromolar concentration of CMT-3 and DC inhibited both the secretion and activity of MMPs by CaP cells. When tested for in vivo efficacy in the Dunning rat CaP model by daily oral gavage, CMT-3 and DC both reduced the lung metastases (> 50%). CMT-3, but not DC, inhibited tumor incidence (55 +/- 9%) and also reduced the tumor growth rate (27 +/- 9.3%). More significantly, the drugs showed minimum systemic toxicity. Ongoing studies indicate that CMT-3 may inhibit the skeletal metastases of CaP cells and delay the onset of paraplegia due to lumbar metastases. These preclinical studies provide the basis for clinical trials of CMT-3 for the treatment of metastatic disease.

Suppressive effect of irsogladine maleate on diethylnitrosamine-initiated and phenobarbital-promoted hepatocarcinogenesis in male F344 rats

Modifying effects of irsogladine maleate (IRG) on diethylnitrosamine (DEN)-induced hepatocarcinogenesis were examined in male F344 rats. Six-week-old rats were divided into 8 groups. Groups 1 through 4 were given a single i.p. injection of DEN (200 mg/kg body weight) at the start of the experiment, whereas groups 5 through 8 received a single i.p. injection of saline as the vehicle treatment. Groups 1 and 8 were kept on the basal diet and distilled water throughout the experiment (36 weeks). Groups 2 and 7 were exposed to 500 ppm phenobarbital (PB) in the drinking water, starting one week after the carcinogen or vehicle treatment. Groups 3 and 5 were fed the diet mixed with 125 ppm IRG from one week after DEN or vehicle treatment. Groups 4 and 6 were given 125 ppm IRG-containing diet and drinking water with 500 ppm PB after the carcinogen or vehicle treatment. Liver neoplasms developed in groups 1 (1/15 rats, 7%) and 2 (14/14 rats, 100%). However, no liver tumors were found in rats of groups 3 through 8. Incidence and average number of liver neoplasms in group 4 (0/14 rats, 0%) were less than those in group 2 (P < 0.0001). The number of glutathione S-transferase placental form (GST-P)-positive liver cell foci in group 3 or 4 was significantly smaller than that in the appropriate control (P < 0.01, P < 0.001, respectively). The average and unit areas of these foci in group 4 were also significantly smaller than those in group 2 (P < 0.001, P < 0.05, respectively). These results suggest that IRG could be a chemopreventive agent for rat liver carcinogenesis.

Removal of intracanal smear by doxycycline in vitro

Cleansing and shaping result in a smear layer on the instrumented canal wall surfaces. The smear layer may inhibit close contact between sealers and dentin, and inhibits diffusion of medicaments.

OBJECTIVE

This study assessed the effect of doxycycline hydrochloride (DH) on smear layer on intracanal walls.

STUDY DESIGN

Scanning electron microscopy was used to evaluate the remaining smear layer using different concentrations of DH. Single-canal palatal roots of extracted maxillary molars were irrigated with saline-15% EDTA; saline-25 mg/ml DH; saline-50 mg/ml DH; saline-100 mg/ml DH; NaOCl-15% EDTA; NaOCl-25 mg/ml DH; NaOCl-50 mg/ml DH; and NaOCl-100 mg/ml DH. The roots were fractured into halves and the amount of smear layer assessed in the middle and apical third.

RESULTS

Doxycycline-HCl of 100 mg/ml was the most effective in removing smear layer. In the saline group, 100 mg/ml of DH was more effective than EDTA. In the hypochlorite group, 50 mg/ml and 100 mg/ml of DH were more effective than EDTA (p < 0.05).

CONCLUSION

Doxycycline solution may be an effective irrigant.

Matrix metalloproteinases

BACKGROUND

The matrix metalloproteinases (MMPs) have a role in gastrointestinal malignancy. This role is reviewed, with particular reference to the gelatinase subgroup of enzymes.

METHODS

All relevant papers derived from the Medline and Enbase databases between 1984 and early 1996 were reviewed.

RESULT AND CONCLUSION

There is now strong evidence that MMPs play a major role in tumour invasion and metastasis. The development of MMP inhibitors may lead to important new treatment for the control of malignant disease.

The "cyclic" regimen of low-dose doxycycline for adult periodontitis: a preliminary study

Specially-formulated low-dose doxycycline (LDD) regimens have been found to reduce collagenase activity in the gingival tissues and crevicular fluid (GCF) of adult periodontitis subjects in short-term studies. In the current, double-blind, placebo-controlled study, adult periodontitis patients were administered for 6 months a "cyclical" regimen of either LDD or placebo capsules; and various clinical parameters of periodontal disease severity, and both collagenase activity and degradation of the serum protein, alpha 1-PI, in the GCF were measured at different time periods. No significant differences between the LDD- and placebo-treated groups were observed for plaque index and gingival index. However, attachment levels, probing depth, and GCF collagenase activity and alpha 1-PI degradation were all beneficially and significantly (P < 0.05) affected by the drug regimen. We propose: 1) that LDD inhibits tissue destruction in the absence of either antimicrobial or significant anti-inflammatory efficacy; and 2) that long-term LDD could be a useful adjunct to instrumentation therapy in the management of the adult periodontitis patient.