Targeted cytotoxic analog of luteinizing hormone-releasing hormone AN-207 inhibits the growth of PC-82 human prostate cancer in nude mice

OBJECTIVE: To examine the effect of gender differences among older adults hospitalized for an acute myocardial infarction (AMI) on subsequent health outcomes. DESIGN: Secondary analysis of the Longitudinal Study on Aging. Data from baseline interviews (1984) and three biennial (1986, 1988, and 1990) re-interviews were linked to Medicare hospitalization and National Death Index records for 1984-1991. PARTICIPANTS: A total of 6071 community-dwelling adults aged 70 years or older at baseline. METHODS: Pooled and stratified multivariable models were used to examine gender differences in the independent effects of being hospitalized for an AMI on all-cause mortality, the risk and volume of subsequent hospitalization, and increases in the number of functional limitations. Two comparison groups were used. RESULTS: Three hundred fifty-seven AMI cases (6%; 172 women and 185 men) were compared with 3976 hospitalized controls and 1738 nonhospitalized controls. The risk of all-cause mortality for AMI cases was greater than that for either hospitalized controls or nonhospitalized controls (referent), and this increased risk was significantly (P < .001) stronger for women (adjusted hazards ratio (AHR) = 14.24, 95%CI = 10.99, 18.46) than for men (AHR = 9.91, 95%CI = 7.75, 12.67). Overall, AMI cases were also more likely to be hospitalized subsequently than the hospitalized controls (referent; adjusted odds ratio (AOR) = 1.47, 95%CI = 1.17, 1.85), although in the stratified analysis this association held for men (AOR = 1.73, 95%CI = 1.25, 2.41) but not for women (AOR = 1.25, 95%CI = .90, 1.73). Among those subsequently hospitalized, both women and men AMI cases consumed more hospital resources than the hospitalized controls, and there were gender differences suggesting that the effects on total charges and length of stay were greater for women than for men with AMI. Finally, although the AMI cases had greater adjusted mean increases in the number of instrumental activities of daily living limitations and lower body limitations than the nonhospitalized controls, they were no worse off than the hospitalized controls, and there were no gender differences in those effects. CONCLUSION: Relative to the appropriate comparison groups, hospitalization for an AMI increases the risk of death and the total costs and lengths of stay of subsequent hospitalizations for women more than for men. Therefore, increased primary prevention, diagnosis, and treatment efforts should be directed toward women.     

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.     

Effect of nucleoside analogue BCH-4556 on prostate cancer growth and metastases in vitro and in vivo

Prostate carcinoma is a common malignancy among males that results in high morbidity and mortality. Here, we have evaluated the capacity of nucleoside analogue BCH-4556 [beta-L-(-)-dioxolane-cytidine] to control prostate cancer progression in our syngeneic model of rat prostate cancer using the rat prostate cancer cell line Dunning R3227 Mat Ly Lu. Different concentrations (50 microM-1 mM) of BCH-4556 resulted in a marked decrease and, eventually, a complete arrest of Mat Ly Lu cell growth in vitro. Cells were inoculated via intracardiac (i.c.) route into the left ventricle or by s.c. injection into the right flank of male Copenhagen rats. Following i.c. inoculation, experimental animals were treated with 75 mg/kg BCH-4556 twice a day or with vehicle alone for 6 consecutive days, starting from day 1 or day 3 post-tumor cell inoculation. Control and experimental animals were monitored for the development of tumor metastases. Treatment with BCH-4556 did not significantly change the development of skeletal metastases and, hence, the time of development of hind limb paralysis. Experimental animals, however, did show a marked reduction in the incidence and size of tumor metastases at the adrenal glands. Following the development of palpable tumors after s.c. injection of Mat Ly Lu cells on day 8 post tumor cell inoculation, animals were treated i.p. with 25-75 mg/kg BCH-4556 twice a day or with vehicle alone for 6 consecutive days. Control animals developed large primary tumors and macroscopic metastasis to lungs, lymph nodes, kidneys, and spleen. In contrast, experimental animals receiving BCH-4556 showed a marked decrease in tumor volume and metastases after the last injection of BCH-4556. The maximum dose of BCH-4556 (75 mg/kg twice a day) caused a complete arrest in tumor growth that was maintained for up to 4-6 days without any evidence of cytotoxicity. These antitumor effects of BCH-4556 were more marked than those of doxorubicin in blocking tumor growth in this model of prostate cancer, and it continued to be effective following three cycles of treatment, without manifesting any signs of drug resistance.     

Luteinizing hormone-releasing hormone agonists interfere with the mitogenic activity of the insulin-like growth factor system in androgen-independent prostate cancer cells

We have previously shown that LHRH agonists exert a direct and specific inhibitory action on the proliferation of the androgen-independent DU 145 prostate cancer cell line; however, the cellular mechanisms mediating this antiproliferative action are not well defined. It is well known that the insulin-like growth factor (IGF) system plays a crucial role in the local regulation of the growth of androgen-independent prostate cancer. The present experiments were performed to evaluate whether LHRH agonists might exert their antimitogenic effect by interfering with the activity of the locally expressed IGF system. To this purpose, the effects of the LHRH agonist Zoladex (LHRH-A) on 1) the mitogenic action of IGF-I, 2) the tyrosine phosphorylation of type 1 IGF-I receptor (IGF-IR), 3) the concentration of IGF-IR, and 4) the secretion of IGF-binding protein-3 were studied. The results obtained show that in DU 145 cells, LHRH-A 1) counteracts the mitogenic action of IGF-I in a dose-dependent manner, 2) prevents the IGF-I-induced tyrosine phosphorylation of the IGF-IR, 3) reduces the concentration of IGF-IR without affecting its Kd value, and 4) does not affect the secretion of IGF-binding protein-3 in the conditioned medium from these cells. These data suggest that LHRH agonists may inhibit the proliferation of human androgen-independent prostate tumor cells by interfering with some of the cellular mechanisms mediating the stimulatory action of the IGF system.     

Epidermal growth factor (EGF) receptor blockade inhibits the action of EGF, insulin-like growth factor I, and a protein kinase A activator on the mitogen-activated protein kinase pathway in prostate cancer cell lines

For assays involving glycosyltransferases or transporters, several GDP-sugars are either commercially unavailable or expensive. We describe an enzymatic synthesis of GDP-d-[3H]arabinosep and GDP-l-[3H]fucose that yields 66-95% nucleotide-sugar from the appropriate radiolabeled sugar in less than 30 min. The coupled reaction requires Mg2+, ATP, and GTP along with the appropriate radioactive monosaccharide, sugar-1-kinase, and pyrophosphorylase. The latter two activities are present in a cytosolic fraction of Crithidia fasciculata, which is easily grown at room temperature in simple culture medium without serum or added CO2. Addition of commercial yeast inorganic pyrophosphatase shifts the equilibrium of the pyrophosphorylase reaction toward nucleotide-sugar formation. To verify that these nucleotide-sugars are biologically active, we tested their ability to serve as substrates for glycosyltransferases. GDP-l-[3H]fucose functions as the donor substrate for recombinant human fucosyltransferase V, and GDP-d-[3H]arabinosep serves as the donor substrate for the arabinosyltransferase activities present in Leishmania major microsomes.