Periodontal tissue disposition of azithromycin

The tissue penetration of azithromycin, the prototype of a new class of macrolide antibiotics named azalides, was studied in patients undergoing surgery for third-molar removal. Drug concentrations in plasma, saliva, and periodontal tissues were evaluated in 28 patients treated with azithromycin 500 mg/day per os for 3 consecutive days. Samples of blood, saliva, gingiva, and alveolar bone were collected during oral surgery, 12 hours, and 2.5, 4.5, and 6.5 days after the last dosing, and the azithromycin concentration was measured microbiologically by using Micrococcus luteus NCTC 8440 as the reference organism. The highest concentrations of azithromycin were observed 12 hours after the last dose in plasma, saliva, gingiva, and bone (0.33 +/- 0.04 mg/l, 2.14 +/- 0.30 mg/l, 6.47 +/- 0.57 mg/kg, and 1.86 +/- 0.15 mg/kg, respectively) and then declined gradually. However, consistent levels of the drug in saliva and periodontal tissues could be detected up to 6.5 days, indicating that azithromycin was retained in target tissues and fluids for a long time after the end of treatment. Among the samples examined, the highest concentration of azithromycin was found in the gingiva at each time studied. Moreover, the ratios of salivary or periodontal tissue levels versus plasma concentrations remained nearly unmodified from 12 hours up to 6.5 days. Overall, these results indicate a favorable disposition of azithromycin into saliva and periodontal tissues and suggest that this macrolide antibiotic represents a valuable option in the pharmacologic treatment of odontogenic infections.

Chronic administration of suramin induces neurotoxicity in rats

In the present study, the ability of suramin 18 mg/kg i.p. twice a week to induce chronic neurotoxicity in rats was investigated. After 20 weeks of suramin treatment, morphological analysis of nerve fibers demonstrated that 57.7+/-3.2% of them presented vesicular disruption of myelin sheaths; their thickness was 0.23+/-0.07 microm in suramin-treated rats with respect to 0.43+/-0.07 microm of controls (P<0.05). To investigate the interaction between suramin and nerve tissue, the binding of the drug to partially purified myelin P0 protein obtained from sciatic nerves was analysed. The percentage of suramin bound to rat myelin P0 protein was 94.0+/-9.5%; this value was decreased to 55.0+/-7.6% when heparan sulfate was added to the myelin protein suspension before suramin. The analysis of tissue drug concentrations at 5, 10 and 20 weeks of treatment showed that suramin accumulated into the sciatic nerve in a time-dependent fashion (130.8+/-18.1, 219.7+/-17.1 and 449.3+/-15.6 microg/g of tissue, respectively). In conclusion, suramin induces a chronic peripheral neurotoxicity in rats characterized by myelin damage and high tissue levels of the drug. The high affinity of suramin for partially purified myelin P0 protein suggests a possible mechanism for drug-induced toxicity.

Dose-finding study and pharmacokinetics of epirubicin and paclitaxel over 3 hours: a regimen with high activity and low cardiotoxicity in advanced breast cancer

PURPOSE

To determine the maximum-tolerated dose (MTD) of paclitaxel over 3 hours with a fixed dose of epirubicin, to investigate the plasma pharmacokinetics of this combination, and to evaluate the toxicity and the activity in previously untreated metastatic breast cancer patients.

PATIENTS AND METHODS

Fifty patients with metastatic breast cancer, measurable disease, and normal left ventricular ejection fraction (LVEF) were eligible. Epirubicin was administered as an intravenous (I.V.) bolus at the fixed dose of 90 mg/m2 before the infusion of paclitaxel over 3 hours. The initial dose of paclitaxel was 135 mg/m2 and was increased by 20 mg/m2 in subsequent cohorts of six patients until dose-limiting toxicity (DLT). Plasma pharmacokinetics of paclitaxel and epirubicin was performed at cycle 1 in at least two patients per dose level of paclitaxel (175 up to 225 mg/m2).

RESULTS

The DLT of this combination was febrile neutropenia in two of eight patients who received paclitaxel at 225 mg/m2. The mean peak plasma concentration of paclitaxel ranged between 5.1 and 6.2 micromol/L at doses of 175 to 225 mg/m2. The concentration of epirubicinol decreased from 47.3 +/- 9.4 to 37.9 +/- 7.5 ng/mL in patients treated with paclitaxel 175 and 225 mg/m2. The most relevant toxicity was grade 4 neutropenia (61% of all courses). The pharmacokinetic data of paclitaxel, in particular the time above the threshold level of 0.05 micromol/L, were not significantly related to myelosuppression. Cardiac toxicity was mild: three patients (6%) developed mild congestive heart failure that was responsive to therapy. Among 49 assessable patients, 41 responses (84%; 95% confidence interval [CI], 70% to 92%) were observed, and nine (18%) of these were complete.

CONCLUSION

Our study demonstrates that (1) the MTD is epirubicin 90 mg/m2 and paclitaxel 200 mg/m2; (2) no clear relationship exists between pharmacokinetic data of paclitaxel and myelosuppression, while the increase in the dose of paclitaxel is associated with a reduction in epirubicinol plasma levels; and (3) the association is feasible, with low cardiotoxicity, and has a high activity in metastatic breast cancer.

Maximum tolerable doses of intravenous zidovudine in combination with 5-fluorouracil and leucovorin in metastatic colorectal cancer patients. Clinical evidence of significant antitumor activity and enhancement of zidovudine-induced DNA single strand breaks in peripheral nuclear blood cells

BACKGROUND

Experimental studies have demonstrated that 5-fluorouracil (5-FU) enhances zidovudine (AZT)-induced DNA strand breaks and cytotoxicity. Phase I studies have demonstrated that the maximum tolerable dose (MTD) of AZT is 8000 mg/sqm when administered i.v. over two hours after weekly 5-FU + l-leucovorin (LV), and that this combination has promising antitumor activity. The purpose of this study was therefore to evaluate the antitumor activity of weekly bolus 5-FU + LV + AZT, administered at its MTD, and to determine whether 5-FU enhances AZT-induced DNA strand breaks in blood nuclear cells.

PATIENTS AND METHODS

Twenty-nine chemotherapy-naïve metastatic colorectal cancer patients with measurable disease entered the study to evaluate the activity of a weekly 5-FU 500 mg/m2 i.v. bolus + LV 250 mg/m2 i.v. two-hour infusion + AZT 8000 mg/m2 i.v. two-hour infusion. In 10 different patients, who during three different weeks received 5-FU + LV, AZT and 5-FU + LV + AZT, DNA strand breaks in blood nuclear cells were determined by a fluorescent analysis of DNA unwinding.

RESULTS

Treatment was generally well tolerated and WHO grades III-IV toxicities, consisting mostly of diarrhea (17%), were uncommon. One patient died of severe diarrhea with consequent hypokalemia and cardiac arrhythmia. All patients were considered evaluable for response, and 3 (10%) complete and 10 (35%) partial responses were observed, for an objective response rate of 45% (95% confidence limit interval 26%-64%). Both 5-FU + LV and AZT decreased the percentage of double stranded DNA in nuclear blood cells. The greatest effect was observed with 5-FU + LV + AZT, which reduced the percentage of double stranded DNA to 50% and 36% after 24 and 48 hours, respectively, and this interaction between 5-FU + LV and AZT was found to be cumulative.

CONCLUSIONS

These studies demonstrate that the present dose and schedule of AZT in combination with 5-FU + LV has significant activity in metastatic colorectal cancer and that the combination of 5-FU + LV with AZT increases the amount of DNA damage. Therefore, AZT in combination with 5-FU + LV warrants further study in colorectal cancer.

Inhibition of experimental angiogenesis by the somatostatin analogue octreotide acetate (SMS 201-995)

The present study investigates the effect of the somatostatin analogue octreotide acetate (SMS 201-995) on experimental angiogenesis in vitro and in vivo. Octreotide reduced the proliferation of human HUV-EC-C endothelial cells (mean, -45.8% versus controls at 10(-9) M; P < 0.05) as well as the density of the vascular network of the chick chorioallantoic membrane (mean, -35.7% versus controls at 50 microgram; P < 0.05). Furthermore, octreotide significantly inhibited chick chorioallantoic membrane neovascularization by the human MCF-10Aint-2 mammary cells secreting the angiogenic protein FGF-3. The proliferation of endothelial and smooth muscle cells from rat aorta explants on fibronectin was reduced by octreotide 10(-8) M (mean, -32.6% versus controls; P < 0.05), and a similar effect was produced on cells sprouting from explants cultured in fibrin (mean, -52.9% versus controls; P < 0.05). Topical administration of octreotide 10 microgram/day for 6 days inhibited rat cornea neovascularization induced by AgNO3/KNO3 (mean, -50.6% versus controls; P < 0.05). Octreotide 40 microgram/day i.p was tested on angiogenesis in rat mesentery obtained by i.p. injections of compound 48/80, a mast cell degranulating agent, or conditioned medium from MCF-10Aint-2 cells and was able to reduce the extent of neovascularization (mean, -45.6 and -64.1%, respectively, versus controls; P < 0.05). These data provide evidence that octreotide is an inhibitor of experimental angiogenesis in vitro and in vivo.

Carbogen and nicotinamide combined with unconventional radiotherapy in glioblastoma multiforme: a new modality treatment

PURPOSE

A new radiotherapy schedule to treat glioblastoma multiforme after surgery, combining nicotinamide and carbogen.

METHODS AND MATERIALS

We analyzed 36 patients with glioblastoma multiforme treated after surgery with radiotherapy, Nicotinamide and Carbogen as follows: 7 patients were treated with accelerated fractionation: two fractions/day, 1.5 cGy/fraction, 6 h interval, 5 days/week, total dose 60 Gy in 4 weeks; 8 patients were treated with the same irradiation scheduling plus Nicotinamide at the dose of 4 g and 2 g in capsules, respectively, 1 h before the first and the second irradiation fraction; 21 patients were treated with accelerated radiotherapy, Nicotinamide, and Carbogen (inhaled 10 min before radiotherapy and during the whole course of irradiation). On the basis of surgical removal our patients were subdivided in three groups: totally resected, with residual tumor <50%, or >50%. Radiotherapy with accelerated fractionation was completed in the scheduled time without side effects on the whole group of patients and Carbogen inhalation did not cause significant change of cardiopulmonar parameters. The toxicity observed was predominant in the gastrointestinal tract and was related to Nicotinamide.

RESULTS

The median survival time (M.S.T.) was 10 months, as reported by others authors with conventional treatment, but in patients without surgical residual tumor and submitted to the complete treatment schedule, the survival at 35 months was around 25%.

CONCLUSIONS

We conclude that this method is feasible with acceptable toxicity; analyzing the survival curves appears to be a trend towards an improvement in survival in the subgroup of patients with gross total removal treated with the combination of Carbogen, Nicotinamide, and accelerated fractionation.

Nonrandom gain of chromosome 7 in central neurocytoma: a chromosomal analysis and fluorescence in situ hybridization study

Central neurocytoma is a benign, slow-growing neoplasm with favourable prognosis. Biomolecular analysis has failed to demonstrate significant alterations, and no cytogenetic alterations have been reported. In this study we demonstrate chromosome 7 gain in three of nine neurocytomas (33%). Traditional cytogenetic analysis performed in four of the nine cases identified trisomy 7 as the sole chromosomal abnormality in one case. Interphase cytogenetics utilizing fluorescent in situ hybridization (FISH) on cell suspensions from formalin-fixed paraffin-embedded tumour tissue performed in all nine cases detected trisomy 7 in two more cases and tetrasomy in another. Our results suggest that chromosome 7 gain is a feature of neuroectodermal tumorigenesis, possibly conferring growth advantage on the neoplastic cells. FISH on interphase nuclei is a valuable adjunct in the genetic evaluation of rare central nervous system neoplasms with low baseline proliferative activity.

The effects of the somatostatin analog octreotide on angiogenesis in vitro

This study examined the in vitro antiangiogenic effects of the somatostatin analog octreotide on the growth of human HUV-EC-C endothelial cells and vascular cells from explants of rat aorta cultured on fibronectin-coated dishes or included in fibrin gel. A total 10(-9) mol/L octreotide reduced the mean uptake of 3H-thymidine by HUV-EC-C cells by 37% compared with controls. The 10(-8) mol/L concentration of octreotide inhibited the proliferation of endothelial and smooth muscle cells growing on fibronectin by 32.6% and reduced the sprouting of cells from the adventitia of aortic rings in fibrin by 33.2% compared with controls, as measured by tetrazolium bioreduction and image analysis, respectively. These results demonstrate that octreotide is an effective inhibitor of vascular cell proliferation in vitro.

Azidothymidine in combination with 5-fluorouracil in human colorectal cell lines: in vitro synergistic cytotoxicity and DNA-induced strand-breaks

The in vitro cytotoxicity of the combination of azidothymidine (AZT) and 5-fluorouracil (5-FU) against the human colorectal cancer cells SW-480, SW-620 and COLO-320DM was evaluated. The cytotoxic effects of 5-FU and AZT were determined by the assay using 2,3-bis(2-methoxy-4-nitro-5-sulfophenil)-2H-tetrazolium-5-carbo xanilide inner salt (XXT), while drug-induced DNA strand-breaks were measured using a fluorometric analysis of DNA unwinding. After an exposure of 72 h, 5-FU and AZT induced a dose-dependent cytotoxicity against each cell line. The addition of 3, 10 and 30 microM AZT to various concentrations of 5-FU, as well as the addition of 0.5, 1 and 3 microns 5-FU to various concentrations of AZT, resulted in an enhanced cytotoxic effect. Isobologram analysis and the combination index (CI) method demonstrated that the interaction between 5-FU and AZT was clearly synergistic in each cell line, except for the 30% level of effect in SW-620, where borderline synergism was observed. The evaluation of DNA strand-breaks after an exposure of 16 h to 5-FU, AZT or 5-FU + AZT demonstrated that the 5-FU + AZT combination produced the greatest DNA damage, and that this interaction was synergistic in each cell line. In conclusion, our study supports the evidence that the potential antitumour activity of AZT can be modulated by combining it with agents which inhibit thymidylate (dTMP) formation, such as 5-FU, and that the increased cytotoxicity is related to enhanced DNA damage. These findings should encourage further experimental and clinical studies of the potential use of AZT in combination with inhibitors of de novo dTMP synthesis.

Phenylacetate inhibits protein isoprenylation and growth of the androgen-independent LNCaP prostate cancer cells transfected with the T24 Ha-ras oncogene

The refractoriness of prostate cancer to androgen suppression is the landmark of clinically aggressive disease. In this study, the androgen-dependent LNCaP prostate cancer cells were transfected with the mutated c-Ha-ras gene from the T24 human bladder cancer. The derivative clone overexpressing T24-ras (LNCaP(T24-ras)) proliferated in androgen-depleted medium and showed increased growth. Protein isoprenylation and p21ras farnesylation in LNCaP(T24-ras) cells were tested in the presence of phenylacetate to document a possible relationship with the drug-induced inhibition of cell proliferation. Phenylacetate is a differentiation inducer that down-regulates in vitro the expression of the myc oncogene and activates the human peroxisome proliferator-activated nuclear receptor involved in cell growth regulation. The drug inhibited protein isoprenylation and p21ras farnesylation in LNCaP(T24-ras) cells; IC50 values were 3.1 and 3.3 mM, respectively, compared with controls. The drug reduced the cellular levels of endogenous farnesyl-PP (mean IC50 = 3.5 mM) and inhibited activation of the p21ras downstream target, p42(MAPK)/ERK2. LNCaP(T24-ras) was more sensitive than the parental line to both growth inhibition (mean IC50 = 3.01 and 7.1 mM, respectively) and apoptosis by phenylacetate. Exogenous farnesyl- and geranylgeranyl-PP indeed reduced the effects of the drug on proliferation and apoptosis in LNCaP(T24-ras) cells. In conclusion, the inhibition of protein isoprenylation and p21ras farnesylation by phenylacetate resulted in increased chemosensitivity of the androgen-independent LNCaP(T24-ras) cells compared with LNCaP, and this effect might contribute to the pharmacological activity of the drug.

Clinical and experimental evidence of inhibition of testosterone production by suramin

The effect of suramin on testosterone production was evaluated in cancer patients, adult male rats, rat Leydig cells, and NCI-H295 human adrenal cancer cells. Testosterone plasma levels markedly decreased in 14 patients receiving suramin as a therapy for refractory cancer, and in 8 of them, the plasma LH and/or FSH levels increased beyond the normal range. The hCG stimulation test (5000 IU, im) was performed in 8 patients and induced an average 2.1-fold increase in testosterone levels over baseline values. Testicular histology after suramin treatment was available in 1 patient who died of progressive disease; this revealed atrophy of seminiferous tubules and reduced Leydig cells in the interstitium. A significant reduction in plasma testosterone was also observed in rats given 18 mg/kg suramin, ip, twice weekly for 8 weeks, whereas plasma LH and FSH levels did not change significantly. Cytohistochemistry of testes from suramin-treated rats showed a reduced number of 3 beta-hydroxysteroid dehydrogenase-positive cells within the interstitium compared to controls, and light microscopy revealed severe impairment of spermatogenesis. Suramin inhibited the production of testosterone by isolated rat Leydig cells as well as the conversion of pregnenolone to progesterone by the 3 beta-hydroxysteroid dehydrogenase enzyme extracted from rat testes, with 50% inhibitory concentrations (IC50 values) of 108.2 and 87.5 micrograms/mL, respectively. Furthermore, suramin reduced the release of testosterone into the culture medium of NCI-H295 adrenal cancer cells with IC50 values of 91.2 and 83.9 micrograms/mL after 6 and 12 days, respectively. These data provide the first evidence in patients that suramin treatment produces a marked reduction in the circulating levels of testosterone, a result that was also obtained in experimental models.

Geranylgeranyl diphosphate-based inhibitors of post-translational geranylgeranylation of cellular proteins

A novel series of stable analogs of geranylgeranyl diphosphate (GGdP) are described in which the biologically labile diphosphate moiety of GGdP is replaced by portions that can act as stable isosters. The compounds inhibited the geranylgeranyltransferase activity in whole PC-3 prostate cancer cells, as determined by the inhibition of post-translational isoprenylation of the small GTP-binding protein p21rap 1 and the accumulation of unprocessed p21rap 1 in the cytosolic fraction. However, the compounds did not affect the farnesylation of p21ras, as shown by protein immunoprecipitation after whole cell labeling with [3 H]-(R,S)-mevalonolactone. Despite the absence of effects of post-translational processing of p21ras, these compounds proved to be cytotoxic for prostate cancer cells, with half-maximal inhibition of cell growth obtained in the range 18.5-35.1 microM. The GGdP analogs described in the this study are novel, non-peptidic inhibitors of geranylgeranylation that may be active as antitumor agents.

Intravenous azidothymidine with fluorouracil and leucovorin: a phase I-II study in previously untreated metastatic colorectal cancer patients

PURPOSE

To determine the plasma pharmacokinetics and the maximum-tolerated dose (MTD) of intravenous (IV) azidothymidine (AZT) administered 90 to 120 minutes after fluorouracil (5-FU) and leucovorin and to preliminarily evaluate the antitumor activity of this combination in metastatic colorectal cancer.

PATIENTS AND METHODS

5-FU 500 mg/m2 IV bolus was administered once a week in the middle of a 2-hour infusion of leucovorin; AZT was given as a 90 to 120-minute IV infusion 60 minutes after 5-FU. Initial AZT dose was 0.5 g/m2, and it was escalated in successive cohorts of three patients by 0.5 to 2 g/m2.

RESULTS

Thirty-five chemotherapy-naive metastatic colorectal cancer patients were entered onto the study, and AZT doses ranged from 0.5 to 10 g/m2. The peak AZT plasma concentration increased from 21.9 to 995.6 micromol/L. The area under the concentration/time curve (AUC) also showed a progressive, but not linear increase from 40.34 to 3,108 h x micromol/L. The most relevant toxicity was diarrhea, which was severe in six patients (17%). Toxicities were not AZT-dose-related, except fpr hypotension, which occurred in patients treated at AZT doses > or = 7 g/m2 and became dose-limiting for AZT 10 g/m2. Among 34 assessable patients, 15 objective responses were observed (44%; 95% confidence interval 27 to 62), lasting a median of 44 weeks; five (15%) were complete.

CONCLUSION

AZT doses > or = 6 g/m2 administered IV over 90 to 120 minutes produce maximum plasma concentration and AUC similar to those previously reached in murine tumor models. Dose-limiting toxicity is hypotension, which occurs at AZT 10 g/m2. The recommended AZT dose for further studies is 8 g/m2. The combination of 5-FU plus leucovorin plus AZT is feasible with acceptable toxicities, and has promising activity in metastatic colorectal cancer.

Clinical and experimental pharmacokinetic interaction between 6-mercaptopurine and methotrexate

Clinical and experimental pharmacokinetic interaction between 6-mercaptopurine (6-MP) and methotrexate (MTX) was investigated in patients as well as in rats and in HL-60 human leukemic cells. Ten children affected by acute lymphoblastic leukemia (ALL) in remission received daily doses of 6-MP given at 25 mg/m2 and i.v. infusion of high-dose MTX at 2 or 5 g/m2 once every other week. When 6-MP was given alone, the mean peak plasma concentration (Cmax) and area under the curve (AUC) of 6-MP were 72.5 ng/ml and 225.3 h ng ml(-1). Concurrent treatment with MTX at 2 or 5 g/m2 resulted in a mean increase of 108% and 121% in the Cmax and of 69% and 93% in the AUC, respectively. In rats treated with an oral dose of 6-MP at 75 mg/m2, MTX given i.p. at 5 g/m2 produced mean increases of 110% and 230% in the Cmax and AUC of 6-MP, respectively. In HL-60 human leukemic cells incubated with 6-MP at 250 ng/ml, the cumulative intracellular concentration of 6-thioguanine and 6-MP nucleotides was not significantly modified by treatment with 20 micrograms/ml of MTX. The present findings indicate that high-dose MTX enhances the bioavailability of 6-MP as evidenced by the observed increases in the plasma Cmax and AUC of 6-MP in humans and animals.

Increased susceptibility of ras-transformed cells to phenylacetate is associated with inhibition of p21ras isoprenylation and phenotypic reversion

Alterations in the expression of ras oncogenes are characteristic of a wide variety of human neoplasms. Accumulating evidence has linked elevated ras expression with disease progression and with failure of tumors to respond to conventional therapies, including radiotherapy and certain chemotherapies. These observations led us to investigate the response of ras-transformed cells to the differentiation-inducer phenylacetate (PA). Using gene transfer models, we show that PA caused cytostasis in ras-transformed mesenchymal cells, associated with increased expression of 2',5'-oligoadenylate synthetase, an enzyme implicated in negative growth control. PA also induced phenotypic reversion characterized by loss of anchorage-independent growth, reduced invasiveness and increased expression of collagen alpha type I, a marker of cell differentiation. The anti-tumor activity of PA was observed in cases involving either Ha- or Ki-ras and was independent of the mode of oncogene activation. Interestingly, in contrast to their relative resistance to radiation and doxorubicin, ras-transformed cells were significantly more sensitive to PA than their parental cells. The profound changes in tumor cell and molecular biology were associated with reduced isoprenylation of the ras-encoded p21. Our results indicate that PA can suppress the growth of ras-transformed cells, resistant otherwise to free-radical based therapies, through interference with p21ras isoprenylation, critical to signal transduction and maintenance of the malignant phenotype.

Inhibitory effect of the somatostatin analogue SMS 201-995 and cytokines on the proliferation of human colon adenocarcinoma cell lines

The activity of the synthetic somatostatin analogue SMS 201-995 was investigated in vitro on the growth of SW480 and SW620 human colon adenocarcinoma cell lines. The inhibition of cell proliferation was significant in SW480 cells (-19.6 +/- 1.4% at SMS 201-995 10-9 M, P < 0.05), but not in SW620 cells (-5.5 +/- 0.8% at SMS 201-995 10-8 M) as compared to untreated cultures. Moreover, SMS 201-995 10-8 M decreased the mitogenic effect of epidermal growth factor (EGF) on the SW480 cell line (-26.6 +/- 3.4% vs. cells exposed to EGF 10 ng ml-1 alone, P < 0.05). The effect of combining SMS 201-995 plus the cytokines interleukin-2 (IL-2) or gamma-interferon (gamma-IFN) on SW480 and SW620 cancer cell growth was also evaluated. The treatment produced a synergistic antiproliferative effect against SW620 cells as compared to untreated cultures, with growth inhibition being -20.2 +/- 1.2 and -19.3 +/- 1.3%, at SMS 201-995 10-8 M plus IL-2 or gamma-IFN 100 IU ml-1, respectively, but did not increase the activity of SMS 201-995 against the SW480 cells. In conclusion, the effect of SMS 201-995 on colon cancer cell growth can be enhanced by its combination with cytokines in SW620 but not in SW480 colon adenocarcinoma cells.

Plasma and tissue disposition of paclitaxel (taxol) after intraperitoneal administration in mice

The pharmacokinetics of single intraperitoneal doses of paclitaxel (18 and 36 mg/kg) in mice were investigated in the present study. The analysis of drug concentrations by HPLC indicated that the plasma Cmax (13.0 +/- 3.1 and 25.7 +/- 2.8 micrograms/ml, respectively) were reached at the 2nd hr. The values of CL were low (0.06 and 0.1 ml/min, respectively), and t1/2 beta values of 3.0 and 3.7 hr were found, after 18 and 36 mg/kg, respectively. The highest tissue concentrations were observed in the liver (50.2 +/- 3.1 and 92.0 +/- 9.5 micrograms/g respectively), followed by the pancreas (39.3 +/- 9.9 micrograms/g) and the ovary (53.4 +/- 5.6 micrograms/g) after 18 and 36 mg/kg, respectively. In the case of the colic tissue, paclitaxel Cmax were 14.4 +/- 0.8 and 32.8 +/- 3.5 micrograms/g at the 3rd hr, respectively, with sustained drug levels still detectable 24 hr after treatment. Paclitaxel Cmax values of 12.7 +/- 3.0 and 53.4 +/- 5.6 micrograms/g were detected in the ovary after 18 and 36 mg/kg, respectively. The overall results provide evidence that, after intraperitoneal administration, paclitaxel concentrates in peritoneal organs; however, the intraperitoneal route does not prevent systemic drug exposure, allowing high and sustained levels of paclitaxel also in several extraperitoneal tissues.

Paclitaxel (taxol) inhibits protein isoprenylation and induces apoptosis in PC-3 human prostate cancer cells

Paclitaxel was examined for its effects on cell survival, internucleosomal DNA fragmentation, and protein isoprenylation in the human prostate cancer cell line PC-3. Treatment of cells with paclitaxel at 5-60 nM for 24 hr resulted in a dose-dependent inhibition of cell viability (IC50, 31.2 nM), which was partially prevented by supplementing the cell culture medium with two nonsterol polyisoprenyl compounds, farnesyl-pyrophosphate (-PP) and geranylgeranyl-PP (3 microM each). Furthermore, agarose gel electrophoresis of DNA extracted from cells treated with paclitaxel (15-60 nM) for 24 hr showed DNA laddering with production of fragments of 180-base pair multiples, indicating the occurrence of apoptotic cell death. Internucleosomal DNA fragmentation by paclitaxel was also detected by a photometric enzyme immunoassay using antihistone antibodies; if culture medium was supplemented with farnesyl-PP and geranylgeranyl-PP (3 microM each), a reduction in mono- and oligonucleosome production was observed. The post-translational incorporation of metabolites of (RS)-[5-3H]mevalonolactone (100 microCi/ml) into prenylated proteins of PC-3 cells was inhibited by paclitaxel at 30 and 60 nM. In addition, the immunoprecipitation of p21ras and p21rap-1 proteins from PC-3 cells exposed to paclitaxel (30 and 60 nM) and labeled with (RS)-[5-3H]mevalonolactone showed a substantial inhibition of the incorporation of farnesyl and geranylgeranyl prenoid groups, respectively, into the aforementioned proteins. These results indicate that the inhibition of protein isoprenylation is a novel component of the complex biochemical effects of the drug and plays an important role in the mechanism of paclitaxel cytotoxicity in PC-3 cells.

Specific labeling of isoprenylated proteins: application to study inhibitors of the post-translational farnesylation and geranylgeranylation

Specific labeling of either farnesylated or geranylgeranylated proteins in human PC-3 prostate cancer cell line was obtained by suppression of mevalonic acid biosynthesis with lovastatin, 50 microM, followed by supplementation of cell culture medium with either [3H]farnesyl- or [3H]geranylgeranyl-pyrophosphate. The immunoprecipitation of either a farnesylated (p21 ras) or geranylgeranylated (p21 rap 1) protein demonstrated that labeling was specific since proteins were detected only if the appropriate isoprenoid was added to the culture medium. TLC analysis indicated that no conversion of one isoprenoid to the other occurred in these conditions. The selective labeling of either farnesylated or geranylgeranylated proteins may be a valuable tool for the development of inhibitors of isoprenoid transferases as a potential new class of antitumor agents.

Suramin in patients with metastatic colorectal cancer pretreated with fluoropyrimidine-based chemotherapy. A phase II study

BACKGROUND

The results of conventional chemotherapy in metastatic colorectal cancer are discouraging, making it a logical target for new treatment approaches a necessary consideration. Suramin is a polysulfonated naphthylurea that binds to several cellular growth factors and has in vitro activity against human colorectal cancer cells. Therefore, this Phase II study of patients with metastatic colorectal cancer was conducted to evaluate its clinical activity.

METHODS

Suramin was administered as a 6-day continuous infusion every week for 8 consecutive weeks by using a computer-assisted dosing of Bayesan pharmacokinetics to maintain suramin plasma concentrations of 200-250 micrograms/ml. Twenty patients with metastatic colorectal cancer who were not responsive or in progression within 6 months after completing fluoropyrimidine-based chemotherapy entered the study.

RESULTS

Toxicities included mostly Grade 1 and 2 fatigue, nausea and vomiting, peripheral neurotoxicity, creatinine elevation, and proteinuria. No objective responses were observed, but three of three patients who received 5-fluorouracil plus folinic acid after suramin achieved a partial response.

CONCLUSIONS

These results indicate that suramin is inactive in patients with metastatic colorectal cancer pretreated with fluoropyrimidines. Pretreatment with suramin may have changed the biology of the tumor, sensitizing it to fluoropyrimidines. Studies to investigate this possibility are in progress.

Trapidil inhibits endothelial cell proliferation and angiogenesis in the chick chorioallantoic membrane and in the rat cornea

The effects of trapidil, a coronaro-active drug which has been shown to inhibit the mitogenic activity of platelet derived growth factor (PDGF), have been investigated on the proliferation of the human endothelial cells (HUV-EC-C), on the neovascularization in the chorioallantoic membrane of the chick embryo (CAM) as well as on the angiogenesis of rat cornea following chemical injury. The proliferation of HUV-EC-C in the presence of trapidil (25 and 250 micrograms/mL) was significantly inhibited by 19 and 25% respectively, compared to controls. On 2-days old CAMs, agarose disks containing 100-150 micrograms of trapidil produced an avascular zone indicating significant antiangiogenic activity, while control agarose disks were without effect. Corneal neovascularization was induced by applying a silver nitrate/potassium nitrate applicator to the rat eyes. A 6-day-treatment with eye drops of a solution of 10 mg/mL trapidil significantly decreased the rate of vessel growth compared with vehicle controls. The antiangiogenic activity of trapidil was markedly increased by the association with hydrocortisone (1.34 mg/mL). These results suggest that trapidil, alone or in combination with a steroid, could be a promising candidate for the therapy of corneal diseases in which alterations induced by neovascular growth play a substantial role.

Pharmacokinetics and tolerance of nicotinamide combined with radiation therapy in patients with glioblastoma multiforme

The pharmacokinetic properties of nicotinamide and its tolerance were studied in seven patients affected by glioblastoma multiforme and treated with two fractions per day of radiation therapy. Nicotinamide was given orally at two daily doses of 4 g and then 2 g separated by a 6-h-interval. The treatment was well tolerated in almost all patients and had no effect on blood pressure, cardiac rhythm or body temperature. Pharmacokinetic analysis showed peak plasma levels (Cmax) above 100 mg/l 45 minutes after the administration of both doses. This was followed by a biexponential decay of plasma concentrations with a thermal half life of 9.4h. Tumours were irradiated 1 hour after each drug dose to match with drug Cmax in plasma, and although it is too early to evaluate the tumour response, the drug levels achieved should be sufficient to improve radiation therapy.