MAT LyLu Research Articles

Prevention of prostate-cancer metastasis in vivo by a novel synthetic inhibitor of urokinase-type plasminogen activator (uPA).

Urokinase-type plasminogen activator (uPA) is a serine protease associated with tissue remodeling, cellular invasiveness, matrix degradation and tumor growth. Over-expression of uPA by the rat prostate-cancer cell line Dunning R3227, Mat LyLu, results in increased tumor metastasis to several non-skeletal and skeletal sites. Histological examination of these skeletal lesions has shown them to be primarily osteoblastic. In the present study we examined the capacity of a selective inhibitor of uPA enzymatic activity, 4-iodo benzo[b]thiophene-2-carboxamidine (B-428), to prevent the development of tumor growth and invasiveness in a syngeneic model of rat prostate cancer using a Dunning R3227 cell line over-expressing rat uPA. Male Copenhagen rats were inoculated s.c. with experimental cells into the right flank and continuously infused i.p. with either vehicle alone or uPA inhibitor for 2 to 3 weeks. Animals were killed at timed intervals and evaluated for the development of tumor growth and metastasis. Serum from these animals was collected to examine any signs of nephrotoxicity. Control animals receiving vehicle alone developed large tumors at the site of inoculation as well as macroscopic metastases in the lungs, kidney, spleen and lymph nodes. In contrast, experimental animals receiving uPA inhibitor showed a marked decrease in primary tumor volume and weight as well as in the development of tumor metastases. The occasional tumor metastases observed after infusion of B-428 were significantly smaller than those observed in vehicle controls. These effects of B-428 were found to be dose-dependent without any adverse effects on the renal function of experimental animals. These studies demonstrate that uPA-specific inhibitors can decrease primary tumor volume and invasiveness as well as metastasis in a model of prostate cancer where uPA has been implicated as a major pathogenetic factor.

Inhibition of prostate cancer growth by estramustine and colchicine.

Hormone-refractory prostate cancer continues to be associated with a very poor prognosis. Agents that inhibit microtubule function have been found to be cytotoxic to prostate cancer cells in preclinical and clinical settings. It was the aim of this study to assess the activity of estramustine and colchicine, two microtubule inhibitors, in hormone-refractory prostate cancer. In clinically achievable concentrations, the combination of estramustine and colchicine was cytotoxic to both the Dunning rat prostate adenocarcinoma cell line MAT-LyLu (MLL) and human prostate cancer cells (PC-3). Microtubule function was assessed in vitro to evaluate possible mechanisms of action. In motility and cell cycle analysis assays, estramustine and colchicine inhibited cellular motility but not cell cycle transit. In vivo, these two agents both inhibited the growth of implanted Dunning rat prostate adenocarcinoma MLL cells but did not appear to have additive effects. The use of oral colchicine in the treatment of hormone-refractory prostate cancer requires further investigation.

Inhibition of prostate cancer growth by vinblastine and tamoxifen

Hormone refractory prostate cancer continues to be an aggressive and fatal disease. Agents which inhibit microtubule function have been found to be cytotoxic to prostate cancer cells in preclinical and clinical settings. It was the aim of this study to assess the activity of tamoxifen and vinblastine, two microtubule inhibitors, in hormone refractory prostate cancer. In clinically achievable concentrations, the combination of tamoxifen and vinblastine was cytotoxic to both Dunning rat prostate adenocarcinoma cell line MAT-LyLu (MLL) and human prostate cancer cells (PC-3). In cell cycle analysis assays, tamoxifen and vinblastine inhibited cell cycle transit. In vivo, these two agents inhibited the growth of implanted MLL cells. It appears that tamoxifen and vinblastine may be effective agents for the treatment of patients with hormone refractory prostate cancer.

Effect of prostatic inhibin peptide (PIP) on prostate cancer cell growth in vitro and in vivo

Prostatic inhibin peptide (PIP), is a 94 amino acid protein which is secreted by the prostate gland in an androgen-independent manner. Previously, it has been demonstrated that PIP appears to inhibit follicle-stimulating-hormone (FSH) secretion by the pituitary and prostate glands. In vitro, the Dunning R3327 rat prostate cancer cell line MAT-LyLu (MLL) cells and the human prostate cancer cell line PC-3, are stimulated to grow in response to exogenous FSH and these effects are blocked by PIP. In vivo, PIP inhibits the growth of the highly metastatic MLL prostate cancer cell line. A comparison of hormone levels in control and PIP-treated rats demonstrates a significant inhibition of FSH in treated animals. It appears that, in vivo, PIP may inhibit prostate cancer growth by inhibiting FSH. PIP may represent a novel hormonal treatment for prostate cancer.

Immunomodulatory effect of cyclophosphamide on host humoral immunity in Dunning's R-3327 adenocarcinoma of the prostate

The object of the present investigations was delineation of the exclusive effects of cyclophosphamide (Cytoxan) on host humoral response to tumor, as evaluated by the level of circulating antigen/antibody complexes (AACs), which may reflect the chemo-responsiveness of hosts and provide a rationale for new therapeutic strategies. Our data, recorded in Copenhagen X Fischer rats bearing Dunning's R-3327 Mat Ly-Lu adenocarcinoma of the prostate, show no modulatory effect of cyclophosphamide at 10 mg/kg, a nonspecific immunosuppressive effect at 30 mg/kg, and a definite immunostimulatory effect on host humoral immunity at 100 mg/kg. Sequential determination of AAC levels at different stages of tumor growth, i.e. from the primary to the metastatic stage, performed with the original purpose of demonstrating that any disturbance in the immunoregulatory mechanism of the host was due to cyclophosphamide rather than to changes in tumor load, revealed that levels of AACs parallel disease progression in the initial stages of primary tumor growth but rapidly decrease to near-normal levels in the presence of heavy tumor burden.

Differences in Expression of Oligosaccharide Determinants by Phenotypically Distinct Sublines of the Dunning 3327 Rat Prostate Cancer

Oligosaccharides expressed by the 3327-H and 3327-MAT LyLu sublines of the Dunning rat prostate cancer model have been compared in formalin-fixed and routinely paraffin-embedded tumour tissues. Binding by lectins of defined specificity has been employed to identify expression of seven oligosaccharide structures by primary and metastatic prostatic carcinoma cells. Neuraminidase digestion was employed to reveal determinants masked by sialic acid.The presence of core Manα1→3(Manα1→6)Manβ1→4GlcNAcβ1→4 determinants recognised by Con-A (Canavalia ensiformis) confirmed expression of complex-type glycoconjugates by plasma membrane and cytoplasmic components of the 3327-H tumour but only by cytoplasmic determinants within 3327 MAT LyLu variant tumour-cells. The only other oligosaccharide freely expressed by either tumour-subline was (GlcNAcβ1→4GlcNAcβ1→4—)n, recognised by WGA (Triticum vulgaris). Prior to neuraminidase digestion, PNA (Arachis hypogaea) (which identifies Type I oligosaccharides: Galβ1→3GalNAc–) bound to pseudoluminal membranes of the 3327-H tumour. However, ECG (Erythrina cristagalli) (which identifies type II oligosaccharides: Galβ1→4GlcNAc–) did not bind to this tumour. Unmasked Type I (Galβ1→3GalNAc–) and Type II (Galβ1→4GlcNAc–) oligosaccharides were not identified in the MAT-LyLu variant. After neuraminidase digestion, PNA-binding was identified along pseudoluminal plasma membranes within 3327-H tumours but only within the cytoplasm of 3327-MAT LyLu primary and metastatic tumour cells. Following neuraminidase digestion, ECG-binding was observed along pseudoluminal plasma membranes of 3327-H tumours and heterogeneously within the cytoplasm of primary, but not metastatic 3327-MAT LyLu tumours. Terminal α/βGalNAc—residues recognised by SBA (Glycine max) were not freely expressed by either subline. These structures were readily detected along luminal membranes of 3327-H cells and weakly detected within the cytoplasm of primary but not metastatic MAT 3327-LyLu tumour cells following neuraminidase digestion. Fucosylated Type II structures (Fucα1→2Gal(GalNAc)–), recognised by UEA-1 (Ulex europaeus-1) and GalNAcα1→3GalNAc—structures recognised by DBF (Dolichos biflorus) were not identified as a component of either tumour subline. The different patterns of oligosaccharide expression, identified by lectin-binding, clearly differentiated between the two tumour sublines and distinguished them from normal prostatic epithelium.The Dunning 3327 rat prostatic cancer sublines offer a useful model with which to examine the relationship between cell-surface oligosaccharide structures and phenotypic variants within a defined tumour-cell population. Correlation with similar changes observed in human prostatic cancer may be of potential diagnostic and prognostic value.

Conventional chemotherapeutic agents combined with DMSO or DFMO in treatment of rat prostate carcinoma

Chemotherapy for prostatic carcinoma is usually reserved for those patients who have failed conventional therapy. These patients generally are in poor health and tolerate chemotherapy poorly. If doses of conventional agents could be decreased without altering cytotoxic activity, then conventional chemotherapy could become an attractive treatment modality. Dimethylsulfoxide and difluoromethylornithine have been shown to induce differentiation in some tumor systems. Growth alteration effects of these two agents were investigated individually and in association with conventional chemotherapeutic agents cyclophosphamide, cisplatin, and fluorouracil in an experimental prostatic cancer model. Copenhagen rats had subcutaneous tumors induced by injections of cells cultured in vitro from a subline of the Dunning rat prostatic tumor, MAT LyLu. Treatment with chemotherapeutic agents individually and associated with differentiation agents was initiated when tumors were palpable. Tumor growth rates and rat body weights were monitored in all groups. The differentiation agents used singly were not able to retard significantly tumor growth rates. In higher doses, each conventional agent used singly significantly retarded tumor growth. Used in combination, the differentiation agents induced cytodestructive properties of lower doses of conventional agents, but some combinations also increased host toxicity. These data suggest that differentiation agents may provide additional antineoplastic benefits when administered in combination with selected chemotherapeutic agents in the management of prostatic cancer.

The effects of polyamine antimetabolites on polyamine-responsive case in kinase activity

The effects of two inhibitors of ornithine decarboxylase activity, ∝-difluoromethylornithine (DMFO) and (2R,5R) 6-heptyne-2,5 diamine (HDA), and an inhibitor of S-adenosylmethionine decarboxylase, methylglyoxal bis-guanylhydrazone (MGBG), were tested on casein kinase activity and endogenous phosphorylation in the cytosol fractions of mouse thyroid and a rat prostate tumor model, Dunning R 3327 MAT LyLu subline. When tested at 5 mM, spermine, DMFO, HDA, and MGBG stimulated mouse thyroid casein kinase activity by 230%, 14%, 65% and 106%, respectively. Similar responses were observed in prostate tumor cytosol. In mouse thyroid cytosol, spermine stimulates 32p incorporation primarily into 3 proteins (MW: 107, 88, and 56 kDa). At 5 mM, MGBG partially reproduces the effects of spermine; HDA is less effective and DMFO is without effect. Similar effects were observed on 3 proteins in prostate tumor cytosol with molecular weights of 91, 41, and 32 kDa. These data provide additional support for the hypothesis that the observed synergistic inhibitory effect of DMFO and MGBG on cell growth may not be due solely to the inhibition of polyamine blosynthesis. Our findings suggest that MGBG-mediated reduction in the phosphorylation of casein kinase substrate should be considered as one locus of action.

In vitro growth inhibition of Dunning rat prostate tumor by bone marrow factor.

Normal Copenhagen rat bone marrow was assayed for growth inhibition of cultured MAT LyLu rat prostate tumor cells. A marrow-derived factor was identified that had significant growth inhibitory activity in vitro against MAT LyLu as well as against DU-145 human prostate tumor and MBT-2 mouse bladder tumor cells but that was noninhibitory to normal rat fibroblasts. The factor was stable to degradation by acid, heat, freezing, trypsin, and carboxypeptidase B. The factor was nonreactive with Coomassie blue, and the molecular weight was estimated as less than 620 daltons. A similar factor was identified in normal human and normal rat sera. The presence of this factor in bone marrow may explain the absence of osseous metastases in the Dunning rat prostate tumor model.

Adenylate kinase: an oncodevelopmental marker in an animal model for human prostatic cancer.

Data are presented demonstrating that adenylate kinase (AK; EC 2.7.4.3) is an oncodevelopmental enzyme in the prostate of Copenhagen rats. We selected the Dunning tumor (dorsal rat prostate) as a model system because it most nearly approximates the human pathology. Four sublines of the tumor (R3327-H, R3327-AT, MAT Lu, and MAT LyLu) were studied. The tumor sublines were maintained as solid tumors in syngeneic rats and as monolayers in tissue culture. AK activity appeared in conjunction with malignant transformation of the dorsal prostate. We also determined the normal developmental enzyme pattern: AK was present in prostates of newborns, but was undetectable in prostates of adults. However, AK increased after castration. Therefore, we propose AK as a potential oncofetal tumor marker in prostatic cancer.

Dimethylsulfoxide-induced changes in a rat prostate adenocarcinoma.

A variety of agents can induce mammalian tumor cell lines to acquire characteristics of the normal cell counterpart. Dimethylsulfoxide (DMSO) has been an effective differentiating agent in many tumor cell lines. In the present study a Dunning rat prostate tumor subline, MAT LyLu, available as an in vitro continuous cell culture was treated with 2.25% DMSO (vol/vol). Treated MAT LyLu cells had a decreased growth rate, saturation density, and clonogenicity, an increased doubling time, and alterations in enzyme activity and tumorigenicity when compared to untreated MAT LyLu cells. The cell viability of treated cells at the saturation density was greater than 90%. MAT LyLu cells treated with DMSO and then removed from DMSO (posttreated) when compared to untreated cells had similar growth rates, doubling times, clonogenicities, enzyme activities, and tumorigenicities. Posttreated MAT LyLu cells had a different growth pattern than untreated MAT LyLu cells. Posttreated cell viability at saturation density was greater than 90%. This investigation demonstrated that a rat prostate adenocarcinoma grown in medium containing 2.25% DMSO acquired characteristics consistent with differentiated prostate cells. Posttreated MAT LyLu cells were similar in many characteristics to untreated cells but were not identical. The alterations noted were not cytotoxic and were not completely reversible. The results of this study correlated with the observations of other investigators who have studied mammalian tumor cell lines exposed to DMSO.

In Vitro Characterization of MAT LyLu: A Dunning Rat Prostate Adenocarcinoma Tumor Subline

Prostate carcinoma has been a therapeutic challenge. The Dunning tumor, a rat prostate adenocarcinoma tumor model, has been used to evaluate prostate carcinoma treatment protocols. The Dunning tumor subline, MAT LyLu, as described in this report, has been established and characterized as an in vitro continuous cell culture. The cell culture has been stable for greater than 60 passages. The in vitro characteristics of the MAT LyLu cell culture, such as growth rate, loss of contact inhibition, clonogenicity, morphology and tumorigenicity, are consistent with the malignant characteristics of the Dunning tumor subline. The MAT LyLu cell culture has enzyme activities which can be used to characterize the cell line. The establishment of MAT LyLu as a continuous cell culture should provide a controlled approach to evaluate the etiology and treatment of prostate carcinoma.

Effect of surgery and adjuvant chemotherapy on the R3327 MAT-Ly Lu tumor.

The R3327 MAT-Ly Lu is a prostate derived, anaplastic, hormone independent carcinoma. It spreads primarily to regional lymph nodes, followed by lung metastases. Combination therapy with surgery (tumor removal with or without regional lymphadenectomy) and chemotherapy (ICRF-159) was more effective treatment than either one alone. Primary tumor excision plus lymphadenectomy appeared to reduce the number of pulmonary metastases.