Blockade of the MAP kinase pathway suppresses growth of colon tumors in vivo.

The mitogen-activated protein kinase pathway is thought to be essential in cellular growth and differentiation. Here we report the discovery of a highly potent and selective inhibitor of the upstream kinase MEK that is orally active. Tumor growth was inhibited as much as 80% in mice with colon carcinomas of both mouse and human origin after treatment with this inhibitor. Efficacy was achieved with a wide range of doses with no signs of toxicity, and correlated with a reduction in the levels of activated mitogen-activated protein kinase in excised tumors. These data indicate that MEK inhibitors represent a promising, noncytotoxic approach to the clinical management of colon cancer.

Feline diarrhoea associated with Tritrichomonas cf. foetus and Giardia co-infection in an Australian cattery.

A 10-week-old female Ocicat was presented at a primary care feline veterinary practice for failure to thrive and diarrhoea. Numerous trophozoites, atypical for Giardia sp., were detected on a direct faecal examination, in addition to Giardia cysts. Although the failure to thrive and diarrhoea resolved following treatment for giardiasis, further diagnostic tests performed on faecal specimens from the kitten and 15 other Ocicats from the same cattery, including culture of trophozoites in In Pouch medium, PCR testing and molecular sequencing of PCR amplicons, confirmed infection with Tritrichomonas cf. foetus. This is the first report in Australia of feline trichomoniasis, which appears to be an emerging infectious disease of cats. Pertinent information regarding the clinical features, diagnosis, therapy, and potential source of feline trichomoniasis within Australia are discussed.

Structure-activity relationships of cysteine-lacking pentapeptide derivatives that inhibit ras farnesyltransferase.

Mutational activation of ras has been found in many types of human cancers, including a greater than 50% incidence in colon and about 90% in pancreatic carcinomas. The activity of both native and oncogenic ras proteins requires a series of post-translational processing steps. The first event in this process is the farnesylation of a cysteine residue located in the fourth position from the carboxyl terminus of the ras protein, catalyzed by the enzyme farnesyltransferase (FTase). Inhibitors of FTase are potential candidates for development as antitumor agents. Through a high-volume screening program, the pentapeptide derivative PD083176 (1), Cbz-His-Tyr(OBn)-Ser(OBn)-Trp-DAla-NH2, was identified as an inhibitor of rat brain FTase, with an IC50 of 20 nM. Structure-activity relationships were carried out to determine the importance of the side chain and chirality of each residue. This investigation led to a series of potent FTase inhibitors which lack a cysteine residue as found in the ras peptide substrate. The parent compound (1) inhibited the insulin-induced maturation of Xenopus oocytes (concentration: 5 pmol/oocyte), a process which is dependent on the activation of the ras pathway.

Glomus tumor of the trachea.

Extracutaneous glomus tumors are uncommon and rarely occur in the trachea. We describe a 73-year-old man with a glomus tumor of the trachea who presented with cough, dyspnea, chest pain, and hemoptysis. A curative segmental tracheal resection with primary reconstruction was performed with no recurrence at 6-year follow-up. The clinicopathologic features of this unusual neoplasm are discussed with a review of the literature.

Thoracic complications of Lemierre syndrome.

Lemierre syndrome is a severe, septicemic illness most commonly caused by the anaerobic Gram-negative bacillus Fusobacterium necrophorum. It is characterized by an acute oropharyngeal infection, with secondary septic thrombophlebitis of the internal jugular vein and frequent metastatic infections. This report of a patient with the Lemierre syndrome is complemented by a review of the literature on the subject.

Prevalence of Bartonella species, Rickettsia felis, haemoplasmas and the Ehrlichia group in the blood of cats and fleas in eastern Australia.

OBJECTIVES: To define the prevalence of Bartonella spp., Rickettsia felis, Mycoplasma haemofelis, 'Candidatus Mycoplasma haemominutum' (Mhm) and 'Candidatus Mycoplasma turicensis' (Mtc) in cats and their fleas in eastern Australia. DESIGN AND PROCEDURE: Conventional PCR assays that detect Bartonella spp., M. haemofelis, Mhm, Mtc, Rickettsia spp., Ehrlichia spp., Anaplasma spp. and Neorickettsia spp. were performed on DNA extracted from blood and fleas collected from 111 cats. Cat sera were assayed by ELISA for IgG of Bartonella spp. RESULTS: DNA of M. haemofelis, Mtc and Mhm was amplified from 1 (0.9%), 1 (0.9%) and 17 cats (15.3%), respectively. Only DNA of Mhm was amplified from the 62 of 111 pooled flea samples (flea sets; 55.9%). Overall, the prevalence rates for Bartonella spp. DNA in the cats and the flea sets was 16.2% (18 cats) and 28.8% (32 flea sets), respectively. Bartonella spp. IgG was detected in 42 cats (37.8%), of which 11 (26.2%) were positive for Bartonella spp. DNA in their blood. R. felis DNA was amplified from 22 flea sets (19.8%), but not from cats. Overall, DNA of one or more of the organisms was amplified from 27% (30) of cats and 67.6% (75) of the flea sets. CONCLUSIONS: This is the first Australian study to determine the prevalence of R. felis and B. clarridgeiae in both fleas and the cats from which they were collected. Flea-associated infectious agents are common in cats and fleas in eastern Australia and support the recommendation that stringent flea control be maintained on cats.

A Double-Blind Placebo-controlled Trial of Ursodeoxycholic Acid in the Prevention of Gallstones during Weight Loss after Vertical Banded Gastroplasty.

One hundred and seven patients whose gallbladder was normal at the time of vertical banded gastroplasty (VBG) were considered for entry into a randomized placebo-controlled double-blind study to determine the effectiveness of ursodeoxycholic acid (UDCA) in preventing cholelithiasis during the period of weight loss. Twenty-one patients (20%) developed gallstones in the six-week period post-VBG and prior to randomization and were therefore excluded. Eighty-six patients were randomized at 6 weeks to active medication or placebo. Of these, 61 patients (71 %) completed the study. Twenty-five patients (29%) failed to complete the study because of incompliance, intolerance to the medication or pregnancy; 17 of these were in the active treatment group and eight were in the placebo group. None of the 27 patients treated with UDCA developed gallstones, whereas eight of 34 (24%) patients taking placebo developed gallstones. This difference was statistically significant (p = 0.0061). These results suggest that UDCA is fully effective in preventing gallstone formation following VBG in patients who follow the prescribed regimen.

Inhibitors of farnesyl:protein transferase--a possible cancer chemotherapeutic.

The recent interest in inhibitors of farnesyl:protein transferase (FPTase) has resulted in a better understanding of the enzymology of this protein. Rationally designed inhibitors of prenyl transfer have emerged as potential new drug candidates because of the insight gained over how a prenyl group is enzymatically transferred onto a peptide thiol. This paper will explore how advances in our understanding of FPTase mediated catalysis has affected the design of FPTase inhibitors as possible cancer therapeutic agents. Without structural information of the enzyme, substrate analogues comprise the first area of drug design: these include peptidomimetics of the four C-terminal amino acids of rasP21 as well as farnesyl diphosphate analogs. In addition, phosphate anion was found to enhance the inhibitory potency of certain compounds known to be competitive with respect to farnesyl diphosphate and therefore incorporation of the phosphate anion may also provide a basis for improved inhibitor design.

Synergy between anions and farnesyldiphosphate competitive inhibitors of farnesyl:protein transferase.

Investigation of the comparative activities of various inhibitors of farnesyl:protein transferase (FPTase) has led to the observation that the presence of phosphate or pyrophosphate ions in the assay buffer increases the potency of farnesyl diphosphate (FPP) competitive inhibitors. In addition to exploring the phenomenon of phosphate synergy, we report here the effects of various other ions including sulfate, bicarbonate, and chloride on the inhibitory ability of three FPP competitive compounds: Cbz-His-Tyr-Ser(OBn)TrpNH2 (2), Cbz-HisTyr(OPO42-)-Ser(OBn)TrpNH2 (3), and alpha-hydroxyfarnesyl phosphonic acid (4). Detailed kinetic analysis of FPTase inhibition revealed a high degree of synergy for compound 2 and each of these ions. Phosphorylation of 2 to give 3 completely eliminated any ionic synergistic effect. Moreover, these ions have an antagonistic effect on the inhibitory potency of compound 4. The anions in the absence of inhibitor exhibit non-competitive inhibition with respect to FPP. These results suggest that phosphate, pyrophosphate, bicarbonate, sulfate, and chloride ions may be binding at the active site of both free enzyme and product-bound enzyme with normal substrates. These bound complexes increase the potency of FPP competitive inhibitors and mimic an enzyme:product form of the enzyme. None of the anions studied here proved to be synergistic with respect to inhibition of geranylgeranyl transferase I. These findings provide insight into the mechanism of action of FPP competitive inhibitors for FPTase and point to enzymatic differences between FPTase and geranylgeranyl transferase I that may facilitate the design of more potent and specific inhibitors for these therapeutically relevant target enzymes.