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T C Hamilton

Publications and source records attributed to T C Hamilton.

At least 91 records · Page 5Linked to original sources
PubMed1992

Spontaneous transformation of rat ovarian surface epithelial cells: association with cytogenetic changes and implications of repeated ovulation in the etiology of ovarian cancer.

BACKGROUND: Ovarian surface epithelial cells undergo several rounds of division to repair the wound created by follicular rupture at the time of ovulation. This cyclical requirement for cell division, when not interrupted by the long anovulatory rest periods that occur during pregnancy and lactation, may contribute to the development of ovarian cancer. PURPOSE AND METHODS: To test this hypothesis, we isolated rat ovarian surface epithelial cells from 10 adult female Fisher rats, initiated two mixed-population and seven clonal cell lines, and repeatedly subcultured these cells in vitro for more than 20 passages. We then tested them for the acquisition of the following four features associated with transformation: 1) the loss of contact inhibition, 2) the capacity for substrate-independent growth, 3) the ability to form tumors when injected subcutaneously and/or intraperitoneally into athymic mice, and 4) cytogenetic abnormalities. RESULTS: Loss of contact inhibition was observed in all nine late-passage cell lines. Six of the nine late-passage, but none of the early-passage, cell lines tested exhibited a capacity for substrate-independent growth that was augmented in a dose-dependent manner by epidermal growth factor. Two late-passage cell lines (clone 2 and mixed-population 2) generated tumors in athymic BALB/c mice within 3 weeks following subcutaneous injection of 5 x 10(6) cells, whereas similar numbers of early-passage cells from the same cell lines failed to generate palpable tumors. Late-passage clone 7 cells were tumorigenic when 5 x 10(7) cells were injected intraperitoneally. Two of the cell lines analyzed exhibited alterations involving losses of part or all of one member of the chromosome 5 pair. Clone 2 possessed an interstitial deletion, del(5)(q21.3q24), consistent with the loss of an uncloned putative tumor suppressor gene at 5q22q23 previously reported to reside near the loci for the interferon alpha, interferon beta, and c-jun genes. Early-passage clone 7 cells exhibited chromosome 5 monosomy, while late-passage cells contained one normal chromosome 5 and a derivative (5q12q). Southern analysis of the three cell lines revealed no consistent loss of loci for the interferon and c-jun genes, although early-passage clone 7 cells had one half the gene copy number for the interferon beta and c-jun genes and both early- and late-passage clone 7 cells lacked DNA sequences hybridizing with the probe for interferon alpha. CONCLUSION: This pattern of passage-dependent spontaneous transformation of rat ovarian surface epithelial cells in vitro supports the hypothesis that repetitious ovulation contributes to the etiology of human ovarian cancer.

Animals↗
PubMed1992

High resistance to cisplatin in human ovarian cancer cell lines is associated with marked increase of glutathione synthesis.

Exposure of human ovarian tumor cell lines to cisplatin led to development of cell lines that exhibited increasing degrees of drug resistance, which were closely correlated with increase of the levels of cellular glutathione. Cell lines were obtained that showed 30- to 1000-fold increases in resistance; these cells also had strikingly increased (13- to 50-fold) levels of glutathione as compared with the drug-sensitive cells of origin. These levels of resistance to cisplatin and the cellular glutathione levels are substantially greater than previously reported. Very high cisplatin resistance was associated with enhanced expression of mRNAs for gamma-glutamylcysteine synthetase and gamma-glutamyl transpeptidase; immunoblots showed increase of gamma-glutamylcysteine synthetase but not of glutathione synthetase. Glutathione S-transferase activity was unaffected, as determined with chlorodinitrobenzene as a substrate. These studies suggest the potential value of examining regulation of glutathione synthesis as an indicator of clinical prognosis. The highly resistant cell lines are proving useful for studying the multiple mechanisms by which tumor cells acquire drug- and radiation-resistance.

Cisplatin↗
PubMed1992

In vitro interactions between platinum analogues in human ovarian-carcinoma cell lines.

In vitro and clinical data suggest that cisplatin and carboplatin resistance may be overcome in some cases by dose escalation, although clinical toxicities limit this approach. Administration of platinum analogues in combination is an alternative dose-intensification strategy that has been little studied. The cytotoxicities of cisplatin (CDDP), carboplatin (CBDCA), and tetraplatin (TP, ormaplatin) alone and in combination were assayed by inhibition of the clonogenic survival of human ovarian-carcinoma cell lines (a) from an untreated patient (A2780), (b) selected for CDDP resistance in vitro (2780-CP70), and (c) from patients presenting with clinically refractory disease (OVCAR3, OVCAR10). The sensitivity patterns of these cell lines to platinum analogues were consistent with the existence of at least two platinum-resistance phenotypes - one being moderately resistant to CDDP and CBDCA but highly resistant to TP and the other being highly resistant to CDDP and CBDCA but only partially cross-resistant with TP. Effects of drug combinations were determined by median-effect analysis. Interactions between platinum analogues were variable in different cell lines. Synergistic cytotoxicity was apparent for the CDDP-CBDCA combination in the A2780 and OVCAR-3 cell lines and for the CDDP-TP combination in 2780-CP70 and OVCAR-3. Strong antagonistic effects were seen for CBDCA-TP in 2780-CP70. Platinum analogues showed additive effects in the remaining cell lines. These data suggest that there may be distinct sensitivity phenotypes for platinum-analogue combinations. The demonstration of in vitro synergy between platinum analogues supports their combined clinical use.

Antineoplastic Agents↗
PubMed1992

Evaluation of in vitro drug screening leads using experimental models of human ovarian cancer.

Five compounds which were identified as potential new anticancer drugs in in vitro screening with the human tumor colony forming assay were selected for further evaluation using in vitro and in vivo models of human ovarian cancer. Three of five compounds were found to inhibit in vitro colony formation of ovarian cancer cell lines derived from both untreated and combination chemotherapy refractory patients. One compound was also found to prolong survival in a human ovarian carcinoma xenograft model system. This compound, chloroquinoxaline sulfonamide, was selected for development and has shown preliminary indication of activity in phase I clinical testing.

Animals↗
PubMed1992

Potentiation of cisplatin cytotoxicity in human ovarian carcinoma cell lines by trifluoperazine, a calmodulin inhibitor.

Chemotherapy for ovarian cancer is frequently limited by cisplatin (CDDP) resistance. Enhanced DNA repair is one of several mechanisms which may cooperate to produce resistance in human ovarian carcinoma cell lines. Published reports suggest that calmodulin inhibitors, such as trifluoperazine (TFP), may inhibit one or more steps in DNA repair. The effects of TFP alone or in combination with CDDP were determined by clonogenic assay of six human ovarian carcinoma cell lines, derived from untreated patients (some of which were selected for cisplatin resistance in vitro) and from patients clinically refractory to cisplatin-based chemotherapy. TFP produced dose-dependent cytotoxicity in all cell lines. In addition, TFP (10 microM) produced approximately two-fold enhancement of CDDP cytotoxicity in three of the six cell lines (A2780, 2780-CP8, and 2780-C30). TFP and CDDP had additive or synergistic cytotoxicity in four of the six cell lines by median effects analysis, while clear antagonism was apparent in the remaining cell lines. These results suggest that TFP may enhance CDDP cytotoxicity in some, but not all, human ovarian carcinoma cell lines. The potential utility of trifluoperazine in ovarian cancer, either alone or in combination with cisplatin, remains to be defined in xenograft models and in clinical trials.

Calmodulin↗
PubMed1992

Effects of BRL 38227 on neurally-mediated responses in the guinea-pig isolated bronchus.

1. In guinea-pig isolated bronchus treated with indomethacin (2.8 microM), electrical field stimulation (EFS; 10 Hz, 0.5 ms, 60-70 V, for 10 s) evoked a tetrodotoxin (3 microM)-sensitive, biphasic contraction comprising a rapid, atropine (1 microM)-sensitive cholinergic response succeeded by a slowly developing, capsaicin (10 microM)-sensitive, non-adrenergic, non-cholinergic excitatory (NANCe) response. 2. BRL 38227 (0.3-3 microM), salmeterol (0.003-3 microM) and ketotifen (1.0-300 microM) each produced concentration-dependent inhibition of both NANCe and cholinergic responses to EFS in guinea-pig isolated bronchus. 3. Substance P (SP; 1 microM) and neurokinin A (NKA; 0.07 microM) produced contractions equivalent in magnitude to the NANCe response to EFS, which were inhibited by salmeterol (1 microM), but not by BRL 38227 (3 microM) or ketotifen (100 microM). 4. Acetylcholine (ACh; 6 microM) was equi-effective with the electrical activation of cholinergic neurones. BRL 38227 (3 microM) slightly inhibited responses to ACh (6 microM). Salmeterol (1 microM) and ketotifen (100 microM) markedly inhibited responses to ACh (6 microM). 5. In bronchial rings pre-contracted with ACh (100 microM), BRL 38227 (0.1-30 microM), salmeterol (0.001-3 microM) and ketotifen (0.1-100 microM) each produced concentration-dependent relaxation. Unlike ketotifen, BRL 38227 and salmeterol only partially (18.8 +/- 2.1% and 51.8 +/- 3.9% respectively) reversed the ACh-induced contraction. 6. The (+)-analogue of BRL 38227, BRL 38226 (0.3-100 microM), was without effect on responses to EFS and had no effect on the inhibition caused by BRL 38227. The K+-channel activators pinacidil (3.0-30 microM) and RP 52891 (3.0-30 microM) exerted similar inhibitory actions on responses to EFS as BRL 38227, but were less potent. Glibenclamide (0.1-1.O microM) and phentolamine (3 microM) antagonized the inhibitory effects of BRL 38227 on responses to EFS.7. It is concluded that BRL 38227 and ketotifen can inhibit NANCe neuroeffector transmission at concentrations exerting little or no inhibitory effects on responses to exogenously applied tachykinins.By contrast, in addition to suppressing NANCe responses to EFS, salmeterol also markedly inhibits responses to SP and NKA. At concentrations markedly suppressing cholinergic neuroeffector transmission, BRL 38227 has only minor effects on responses to exogenously-applied ACh. Salmeterol and ketotifen both depress responses to ACh within the concentration-range over which they inhibit cholinergic responses to EFS. The inhibitory effects of BRL 38227 on responses to EFS exhibit stereo-specificity and may involve the opening of a neuronal K+-channel. This K+-channel is glibenclamide-and phentolamine-sensitive and appears similar to the smooth muscle K+-channel which is modulated by BRL 38227.

Albuterol↗
PubMed1992

Growth regulation of ovarian cancer.

The disease referred to as ovarian cancer is composed of those tumors derived from the ovarian surface epithelium. Ovarian cancer incidence peaks in postmenopausal women, when the hormonal milieu is in a state of flux. The ovarian carcinomas have histologic characteristics of classical endocrine responsive tissues. For example, the serous tumors are similar in appearance to the epithelium of the fallopian tube, the mucinous tumors to that of the endocervix, and the endometrioid tumors to that of the endometrium. These observations alone suggest a role for hormones in disease etiology and progression. In addition, much experimental evidence has accumulated that shows direct hormonal and growth factor effects on the normal and neoplastic ovarian surface epithelium and the potential for responsiveness based on the presence of specific receptors. The concept that growth stimulatory substances, by their impact on mitosis and cell number, may influence the rate of mutations that could confer malignant transformation serves as an additional mechanism by which growth stimulatory substances can influence ovarian cancer initiation. With the emergence of new molecular biology techniques, future studies should unravel the mechanisms by which steroid hormones, peptide hormones, and peptide growth factors influence the development of ovarian cancer.

Female↗
PubMed1991

Expression of insulin-like growth factor I, its binding proteins, and its receptor in ovarian cancer.

Insulin-like growth factor (IGF) I is a polypeptide hormone important in normal growth and development. Although IGF-I is a mitogen for many cancer cell lines, previous work has suggested that autocrine production of IGF-I is uncommon in cancers of epithelial origin. In this study, expression of IGF-I, its binding proteins, and its receptor were examined in ovarian cancer cell lines and tissues. Of 10 ovarian cancer cell lines, 3 (OVCAR-3, OVCAR-7, and PEO4) expressed IGF-I mRNA. RNase protection assays using probes derived from IGF-IA, IGF-IB, and alternate exon 1 IGF-I complementary DNAs demonstrated that these cells contained a predominant IGF-I transcript with an alternate first exon. RNA extracted from primary and metastatic ovarian cancer tissues also expressed IGF-I mRNAs (7 of 7) with the alternate first exon. IGF-I protein was detected in OVCAR-3-conditioned media; this activity was secreted in conjunction with several IGF-binding proteins (IGFBPs). IGFBP-2, IGFBP-3, an Mr 24,000 species, and an Mr 30,000 species could also be demonstrated in OVCAR-3. Type I IGF receptor mRNA was found in all 10 of the ovarian cancer cell lines and all 7 of the primary or metastatic ovarian cancer tissues. IGF-I was a mitogen for OVCAR-3, demonstrating the presence of a functional type I IGF receptor. These data show that all the necessary components for an IGF-I-mediated autocrine loop are expressed by ovarian cancer cells.

Blotting, Northern↗
PubMed1991

Comparative cytotoxicity of CI-973, cisplatin, carboplatin and tetraplatin in human ovarian carcinoma cell lines.

The clinical efficacy of cisplatin-based chemotherapy for ovarian cancer is frequently compromised by drug resistance or dose-limiting renal and neurologic toxicities. CI-973 (NK-121), a 2-methyl-1,4-butanediamine analogue of carboplatin, has shown little nephro- and neuro-toxicity in pre-clinical model systems and in phase-I trials. Its in vitro spectrum of activity against ovarian cancer cell lines has not been previously characterized. The in vitro activities of CI-973, cisplatin, carboplatin and tetraplatin were compared in several platinum-sensitive and -resistant human ovarian carcinoma cell lines. Cytotoxicity was assessed by inhibition of clonogenic survival in soft agar with continuous drug exposure. On a molar basis, cisplatin and tetraplatin were the most potent analogues, while carboplatin was consistently less potent. Cisplatin, carboplatin and CI-973 elicited a very similar response pattern by Spearman rank correlation, distinct from that seen with tetraplatin. The magnitude of resistance to CI-973 was comparable to cisplatin in 5 cell lines but was substantially lower in the highly cisplatin-resistant 2780-CP70 and OVCAR-10 cell lines. These results suggest that CI-973 and tetraplatin may have potential utility in some cases of cisplatin-resistant ovarian cancer. In addition, our data are consistent with the existence of at least 2 platinum-resistance phenotypes--one with moderate levels of resistance to cisplatin, carboplatin and CI-973 but highly resistant to tetraplatin, the other highly resistant to cisplatin and carboplatin but only partially cross-resistant with tetraplatin and CI-973. The recognition of different resistance phenotypes may facilitate the study of cellular resistance mechanisms to cisplatin and newer platinum analogues.

Antineoplastic Agents↗
PubMed1991

Antihypertensive and haemodynamic properties of the potassium channel activating (-) enantiomer of cromakalim in animal models.

The present studies describe the blood pressure lowering, and some other haemodynamic effects, of the potassium channel activator, BRL 38227 ((-) enantiomer of cromakalim, CAS 94470-67-4) in various animal models. BRL 38227 was a potent antihypertensive agent following oral administration to conscious spontaneously hypertensive rats, SHR, (0.038, 0.075 and 0.15 mg/kg), renal hypertensive cats (0.035 and 0.05 mg/kg) and renal hypertensive dogs (0.05 and 0.1 mg/kg). The (+) enantiomer of cromakalim (BRL 38226) was without effect on blood pressure in the conscious rat and cat confirming the stereospecific mode of action of this potassium channel activator. Tachycardia accompanied the antihypertensive effect of BRL 38227 in these models and in the rat this effect could be abolished by pretreatment with atenolol (conscious SHR), diltiazem, verapamil, propranolol and alinidine (anaesthetised rats). In addition to reflex tachycardia, BRL 38227 also increased plasma renin activity and aldosterone levels in the conscious renal hypertensive cat. In both the anaesthetised normotensive cat (0.001 mg/kg/min i.v.) and dog (0.0025 to 0.02 mg/kg i.v.) BRL 38227 lowered blood pressure and total peripheral resistance while increasing cardiac output via increased heart rate and stroke volume in the cat and via increased heart rate alone in the dog. BRL 38227 reduced renal vascular resistance in both conscious (0.01, 0.015 and 0.02 mg/kg p.o.) and anaesthetised (0.001 mg/kg/min i.v.) cats and the effect was maintained despite marked reductions in blood pressure. In the anaesthetised dog, BRL 38227 was a potent coronary arterial dilator and this effect was also maintained in the face of marked blood pressure lowering activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1991

Effects of synthetic peptides and protease inhibitors on the interaction of a human ovarian cancer cell line (NIH:OVCAR-3) with a reconstituted basement membrane (Matrigel).

We have investigated the adhesive properties and invasiveness of cells of the human ovarian carcinoma line, NIH:OVCAR-3, in vitro. OVCAR-3 cells exhibited a similar rate of adhesion to all substrates tested including laminin, fibronectin, and collagens I and IV. The synthetic peptide YIGSR-NH2, which corresponds to an attachment site in laminin, inhibited the adhesion of the cells to laminin, but not to fibronectin. In contrast, a GRGDS-NH2 peptide blocked adhesion to fibronectin but not to laminin. OVCAR-3 cells invaded and formed branched colonies on Matrigel. Colony formation was retarded by both YIGSR-NH2 and GRGDS-NH2 peptides. Serine protease inhibitors and human recombinant TIMP, the tissue inhibitor of metalloproteases, inhibited ovarian tumor cell invasion while a synthetic collagenase IV inhibitor (SC-44463) had no effect. These studies suggest that metalloproteases other than collagenase IV may be important for the invasive activity of ovarian cancer cells. It is possible that synthetic peptides with antiadhesive cellular activity and certain antiproteases could be used to control the progressive colonization and invasion of peritoneal surfaces by malignant ovarian cancer cells.

Amides↗
PubMed1990

Metallothionein gene expression and resistance to cisplatin in human ovarian cancer.

Intracellular thiols have been proposed as mediators of resistance to alkylating agents and cisplatin. As metallothionein is the predominant protein thiol, we examined its relationship to cisplatin resistance in human ovarian cancer cell lines. A human ovarian carcinoma cell line, A2780, derived from an untreated patient, was treated with cisplatin in several ways and the induced resistance to cisplatin ranged from 13- to 68-fold. The degree of resistance was dependent upon the method of selection. The drug-resistant cell lines also developed low levels of cross-resistance to cadmium. Additional cell lines established from untreated patients or ovarian cancer patients refractory to cisplatin- and/or carboplatin-containing combination chemotherapy were studied. The most cisplatin-resistant cell lines, OVCAR-8 and -10, were from patients previously treated with intensive chemotherapy. OVCAR-8 was relatively cross-resistant to cadmium while OVCAR-10 appeared relatively sensitive. Cell lines were examined for expression of metallothionein mRNA to evaluate the relationship between cisplatin resistance, cadmium cross-resistance and metallothionein expression. Only two of the cell lines with in vitro-induced resistance to cisplatin, 2780E80 and 2780CP70B3, had detectable metallothionein mRNA. The other cell lines selected in vitro for cisplatin resistance, as well as the parental A2780 ovarian cancer cell line, showed no expression at our level of detection. There was variable expression of metallothionein among the OVCAR cell lines. Cell lines from untreated patients, OVCAR-5 and -7, did express metallothionein, while the most cisplatin-resistant cell lines, OVCAR-8 and -10, did not. We also examined cisplatin induction of metallothionein mRNA in the cell lines. Only 2780CP70B3 among the cell lines with in vitro-induced cisplatin resistance showed increased expression after short-term exposure to cisplatin. OVCAR-4 also had a slight increase in expression after exposure to cisplatin. Mouse C127 cells transfected with a bovine papilloma virus-metallothionein gene construct were compared for cisplatin sensitivity to the same cell type transfected with bovine papilloma virus alone. In this model system, metallothionein expression did not influence cisplatin cytotoxicity. On the basis of these studies, we conclude that there is no causal relationship between metallothionein expression and cisplatin resistance.

Cadmium↗
PubMed1990

Resistance to alkylating agents and cisplatin: insights from ovarian carcinoma model systems.

The curative potential of chemotherapy for ovarian cancer is frequently not realized due to platinum and alkylating agent resistance. Mechanisms which may contribute to the resistant phenotype include alterations in drug transport, increased levels of sulfhydryl molecules (and/or related enzymes), and enhanced DNA repair. We have developed several ovarian cancer cell lines resistant to platinum compounds and alkylating agents. Increased levels of glutathione and enhanced DNA repair are major determinants of chemoresistance in these cells. Modulation of these processes with buthionine sulfoximine (BSO), aphidicolin, arc-C, etc. partially reverses in vitro resistance. Similar clinical treatment strategies are under investigation.

Alkylating Agents↗