Paracrine regulation of ovarian cancer by endothelin

Previous studies have demonstrated that endothelin (ET) isoforms (ET-1, ET-2 and ET-3) can act in an autocrine manner in ovarian cancer while in breast cancer their role has been proposed to be that of a paracrine mitogen. To explore the possibility that endothelin isoforms might function not only as autocrine regulators but also as paracrine mitogens in ovarian cancers, we investigated their effects on the growth of ovarian fibroblasts derived from ovarian carcinomas, the interaction between ovarian carcinoma and fibroblast cells and the location of the isoform expression in primary ovarian tumours. ET-1, ET-2 and ET-3 stimulated the growth of three ovarian fibroblast cell lines at concentrations ranging from 10(-12) M to 10(-7) M. Inhibition of 125I-ET binding by the ETA receptor antagonist BQ123 and the ETB receptor antagonist BQ788 suggested the presence of both types of ET receptors in fibroblast cells. In the absence of ET-1, neither BQ 123 nor BQ 788 inhibited growth. However, both antagonists inhibited ET-1 stimulated growth suggesting the involvement of both receptor types in ET-1 growth regulation. In contrast to carcinoma cells which secrete measurable levels of ET-1, fibroblast cell lines did not secrete detectable protein. Co-culture experiments (using porous membrane insert wells) of fibroblasts with carcinoma cells demonstrated that growth of both populations of cells was increased compared with either grown in isolation. In this system, growth of the fibroblast cell line was partially inhibited by both BQ123 and BQ788, whilst growth of the PE014 carcinoma cell line was inhibited by only BQ123. RT-PCR measurements detected the presence of the ETA receptor subtype in 10/10 primary ovarian cancers but the presence of ETB receptor in only 6/10 cancers. Using specific antibodies, ET-1 was found in 11/15, ET-2 in 5 of 7 and ET-3 in 5/7 primary ovarian cancers predominantly in the epithelial cells but with some stromal expression. These data indicate that the ET isoforms may stimulate growth of the fibroblast population within an ovarian cancer in addition to stimulating the epithelial cells and since the ETs are expressed in the majority of ovarian cancers, this paracrine effect may contribute to the overall growth of the tumour.

Regulation and function of the extracellular matrix protein tenascin-C in ovarian cancer cell lines

The extracellular matrix glycoprotein tenascin-C (TN) is overexpressed in the stroma of malignant ovarian tumours particularly at the interface between epithelia and stroma leading to suggestions that it may be involved in the process of invasion (Wilson et al (1996) Br J Cancer 74: 999-1004). To define regulation of TN further and investigate its function in ovarian cancer, a range of cell line models were studied. Concentrations of secreted TN in media from cultures of ovarian fibroblast cell lines were at least 100-fold greater than from carcinoma cell lines. Evidence for paracrine regulation of TN secretion was obtained by co-culture of carcinoma cells with fibroblast cells wherein secretion into the media was greater than from fibroblasts alone. Transforming growth factor (TGF)-beta1, insulin-like growth factor (IGF)-II and progesterone all stimulated TN secretion while human choriogonadotropin (hCG), follicle-stimulating hormone (FSH) and gamma-interferon inhibited secretion. TGF-beta1 produced the greatest stimulation of TN in cultured fibroblasts and its co-expression with TN was examined in primary ovarian tumours. There was a significant association between the presence of moderate-strong expression of TN and TGF-beta1. Evidence for TN having a functional role in ovarian carcinoma was obtained from adhesion and migration assays. The PE01, PE04, SKOV-3 and 59M cell lines all demonstrated marked adhesion to plastic coated with TN relative to the control protein bovine serum albumin (BSA) and expressed alpha2beta1 and alpha3beta1 integrins. The SKOV-3 cell line migrated more rapidly through TN than through BSA indicating that TN can facilitate migration of ovarian carcinoma cells.

Inhibition of transforming growth factor alpha (TGF-alpha)-mediated growth effects in ovarian cancer cell lines by a tyrosine kinase inhibitor ZM 252868

The modulating effects of the epidermal growth factor (EGF) receptor-specific tyrosine kinase inhibitor ZM 252868 on cell growth and signalling have been evaluated in four ovarian carcinoma cell lines PE01, PE04, SKOV-3 and PE01CDDP. Transforming growth factor alpha (TGF-alpha)-stimulated growth was completely inhibited by concentrations > or =0.3 microM in the PE01 and PE04 cell lines and by > or =0.1 microM in SKOV-3 cells. TGF-alpha inhibition of PE01CDDP growth was reversed by concentrations > or =0.1 microM ZM 252868. TGF-alpha-stimulated tyrosine phosphorylation of both the EGF receptor and c-erbB2 receptor in all four cell lines. The inhibitor ZM 252868, at concentrations > or =0.3 microM, completely inhibited TGF-alpha-stimulated tyrosine phosphorylation of the EGF receptor and reduced phosphorylation of the c-erbB2 protein. EGF-activated EGF receptor tyrosine kinase activity was completely inhibited by 3 microM ZM 252868 in PE01, SKOV-3 and PE01CDDP cells. These data indicate that the EGF receptor-targeted TK inhibitor ZM 252868 can inhibit growth of ovarian carcinoma cells in vitro consistent with inhibition of tyrosine phosphorylation at the EGF receptor.

Growth-inhibitory effects of the synthetic retinoid CD437 against ovarian carcinoma models in vitro and in vivo

The activity of CD437¿6-[3-(1-adamantyl)-4 hydroxyphenyl]-2-naphthalene carboxylic acid¿, a relatively selective activator of RAR-gamma, was evaluated against four human ovarian-carcinoma cell lines : PE01, PE04 (a Pt-resistant in vivo-derived counterpart of PE01), PE01CDDP (a Pt-resistant in vitro-derived model of PE01) and PE014. Growth inhibition was observed after 3 and 6 days of exposure to sub-micromolar concentrations as assessed by a reduction in cell number. IC50 values against PE01, PE04, PE01CDDP and PE014 were 0.09, 0.21, 0.12 and 0.28 microM (day 3) and 0.1, 0.14, 0.07 and 0.17 microM (day 6), respectively. Cisplatin-resistant cell lines were as responsive as cisplatin-sensitive lines, indicating potential activity in resistant disease. CD437 was also evaluated against the PE04 xenograft grown in nude mice using daily doses of 20 (days 0-4) and 10 mg/kg (days 0-4 and 7-11) given either by i.p. delivery or oral administration. Significant growth inhibition (P < 0.05) was obtained for both doses and by both routes. These data provide further support for the view that retinoids have value for the treatment of ovarian cancer.

Functionality of the progesterone receptor in ovarian cancer and its regulation by estrogen

Here, we sought to obtain evidence that the progesterone receptor (PR) may be functional in ovarian cancer and regulated by estrogen. Megestrol acetate inhibited growth of the PR-positive PE04 ovarian carcinoma xenograft but not the PR-negative HOX 60 xenograft. PR concentration was higher in early-stage (I/II) tumors than in advanced-stage (III/IV) tumors (P = 0.007) and in tumors of endometrioid histology compared to other carcinoma subtypes (P = 0.009). Patients with a tumor PR concentration of >40 fmol/mg protein had significantly improved survival over those patients whose tumors contained <40 fmol/mg (P = 0.0007; log-rank). Evidence of PR regulation by estrogen was obtained by endocrine manipulation of the PE04 xenograft. PR content of PE04 xenografts fell from 145 to 7 fmol/mg protein in ovariectomized mice and was 2 fmol/mg in male mice. Administration of 17-beta-estradiol increased PR content to 745 fmol/mg. In primary ovarian carcinomas, PR was significantly associated with ER concentrations (P < 0.0001), suggesting regulation of PR levels by estrogen. This association was present for tumors of endometrioid histology (P < 0.0001) but not for those with serous histology (P = 0.31). These data point to the regulation of PR levels by estrogen in ovarian cancer and to a mediatory role for PR in the inhibition of growth induced by progestin.

The antitumour activity of the prodrug N-L-leucyl-doxorubicin and its parent compound doxorubicin in human tumour xenografts

The antitumour activity of the investigational agent N-L-leucyl-doxorubicin (Leu-DOX) was compared with that of doxorubicin (DOX) in human tumour xenografts growing subcutaneously in athymic nude mice. Leu-DOX was developed as a prodrug of DOX, and may be converted into the clinically active parent compound by hydrolytic enzymes present in or on tumour cells. It has been suggested that a better therapeutic index with a reduced cardiac toxicity and higher efficacy might be obtained. Both compounds were administered intravenously weekly for 2 weeks, each at maximum tolerated doses of 8 mg/kg and 28 mg/kg for DOX and Leu-DOX, respectively. The panel of xenografts represented three different tumour types. Leu-DOX showed antitumour activity, defined as tumour growth inhibition > 50% and specific growth delay > 1.0, in 10 of the 16 tumours, including two of five breast, five of seven small cell and three of four non-small cell lung carcinomas. In comparison, DOX was active in one breast, four small cell lung and two lung adenocarcinoma xenografts. In all the DOX sensitive lung tumours, Leu-DOX showed higher efficacy than the parent compound. Based on the results of the present study, and since phase I clinical trials with Leu-DOX have already been performed, phase II clinical evaluation of Leu-DOX in patients with breast and lung cancer is recommended.

Antitumour activity and schedule dependency of 8-chloroadenosine-3',5'-monophosphate (8-ClcAMP) against human tumour xenografts

8-Chloroadenosine-3',5'-monophosphate (8-ClcAMP) is a novel antitumour agent currently undergoing phase I clinical trials in several European centres. In this study, its antitumour activity against human tumour xenografts and its dependence on schedule were investigated. When administered by continuous infusion at doses of 100 or 50 mg/kg/day to nude mice bearing human tumour xenografts, 8-ClcAMP inhibited the growth of the HT 29 colorectal, ZR-75-1 breast, HOX 60 and PE04 ovarian and PANC-1 pancreatic carcinoma xenografts. However, these infusion schedules produced hypercalcaemia and severe weight loss. In an attempt to optimise antitumour activity and minimise toxicity, several other schedules were studied. In comparison with continuous administration of 8-ClcAMP at 50 mg/kg/day for 14 days which, although producing complete growth inhibition in the HOX 60 model, was associated with a marked body weight loss, schedules in which the infusion was interrupted (infusion on either days 0-4; 7-11 or days 0-2; 6-8) produced minimal weight loss but also reduced antitumour activity. However, co-administration of salmon calcitonin with continuous infusion of 8-ClcAMP prevented both hypercalcaemia and body weight loss in 3/6 animals while still producing marked inhibition of tumour growth. These data indicate that 8-ClcAMP has broad-spectrum antitumour activity and the major side-effect of hypercalcaemia may at least in part be ameliorated by the use of salmon calcitonin.

Estrogen regulation of transforming growth factor-alpha in ovarian cancer

Transforming growth factor alpha (TGFalpha) may be induced by estrogen in estrogen responsive systems and can contribute to the growth-modulatory effects of this hormone. To test whether TGFalpha contributes to estrogen-regulated growth in ovarian cancers, we have compared the effects of 17beta-estradiol (E2) and TGFalpha in a range of ovarian carcinoma cell lines. Addition of E2 to the estrogen receptor (ER)-positive cell lines (PE01, PE04 and PE01CDDP) produced a 2-4 fold increase in TGFalpha protein concentrations in media conditioned by the cells. Both E2 and TGFalpha stimulated the growth of the PE01 and PE04 lines and inhibited the growth of the PE01CDDP line. Furthermore, the E2-mediated growth effects could be reversed by an epidermal growth factor (EGF) receptor-targeted antibody. E2 also down-regulated EGF receptor expression in ER-positive cell lines. In a series of primary ovarian tumors, higher concentrations of ER were associated with an increased percentage of tumors expressing TGFalpha mRNA and a decreased percentage expressing EGF receptor protein. All these data are consistent with E2 increasing production of TGFalpha in ER-positive ovarian cancer and this in turn acting through the EGF receptor to modulate growth in an autocrine manner.

Transforming growth factor-beta isoform expression in human ovarian tumours

The expression patterns of members of the transforming growth factor-beta (TGF-beta) family were analysed in 96 primary ovarian tumours by RNAse protection assay. mRNA for the three mammalian isoforms, TGF-beta 1, TGF-beta 2 and TGF-beta 3, was detected in 46, 66 and 66% of 74 malignant tumours, respectively, with the predominant patterns of expression being either dual or triple co-expression. TGF-beta II receptor expression, detected by reverse-transcription PCR, was present in 92% malignant tumours. Expression patterns were similar between malignant, borderline and benign tumours, although TGF-beta 1 incidence was reduced in benign tumours. In malignant tumours, the incidence of TGF-beta 1 expression was less than that of either TGF-beta 2 (P = 0.02) or TGF-beta 3 (P = 0.0014), while in both malignant and borderline tumours, TGF-beta 2 and TGF-beta 3 tended to be co-expressed. Aneuploid tumours were more likely than diploid tumours to express multiple rather than single forms of TGF-beta (P = 0.018). The incidence of TGF-beta 1 expression was reduced in PR-moderate/rich (PR > 20 fmol/mg protein) relative to PR-negative/poor tumours (P = 0.048), while TGF-beta 3 expression was increased in ER-moderate/rich (ER > 20 fmol/mg protein) tumours compared to ER-negative/poor tumours (P = 0.0012). Expression of TGF-beta 3, but not TGF-beta 1 or TGF-beta 2, was associated with advanced stage disease (P = 0.014) and, in the malignant group, reduced survival (P = 0.02) with a hazard ratio of 2.6. These data suggest a possible role for TGF-beta 3 in the progression of ovarian cancer.

Endothelin expression and responsiveness in human ovarian carcinoma cell lines

To elucidate the potential role of endothelins (ETs) as growth regulators in ovarian carcinoma cells in culture, expression of endothelins and their receptors were measured in two ovarian cancer cell lines (PEO4 and PEO14), together with the effect of the exogenous addition of endothelins on the growth of these cell lines in vitro. RT-PCR analysis of mRNA prepared from PEO4 and PEO14 indicated the presence of ET-1 and ET-3 mRNA. Immunoreactive ET-1-like peptide was found in media from cultures of both PEO4 (1.7 +/- 0.4 fmol/10(6) cells/72 h) and PEO14 (20.2 +/- 6.8 fmol/10(6) cells/72 h) cell lines. Radioligand binding studies using 125I-ET-1 and membrane fractions were consistent with PEO4 cells having two receptor sites of either high affinity (Kd = 0.065 nM, Bmax = 0.047 pmol/mg protein) or lower affinity sites (Kd = 0.49 nM, Bmax = 0.23 pmol/mg protein). Studies using membrane fractions of PEO14 cells indicated that this cell line has only a single lower affinity binding site (Kd = 0.56 nM, Bmax = 0.31 pmol/mg protein). However, RT-PCR analysis indicated the presence of mRNA from both ETA and ETB receptors in PEO4 and PEO14 cell lines. Exogenous addition of ETs to PEO4 and PEO14 cells at concentrations of 10(-10)-10(-7)M resulted in specific dose-dependent increases in cell number for ET-1 (with maximum effects at 10(-10) and 10(-9)M for PEO4 and PEO14, respectively) and ET-2 (maximum effects at 10(-8) and 10(-9)M for PEO4 and PEO14, respectively) but not for ET-3. Experiments on the growth of PEO14 cells using BQ123 (ETA-R) antagonist and "antisense" oligonucleotide against the ETA-R, in the absence of exogenous ETs, suggested that immunoreactive ET-1-like material secreted by PEO14 cells can affect their growth in an autocrine manner. These results would be consistent with ET-1 acting as a possible autocrine growth regulator in human ovarian carcinoma cells.

Steroid hormones and cancer: (III) observations from human subjects

Epidemiological evidence strongly suggests that steroid hormones are implicated in the risk of cancers of the breast, ovary and endometrium. However, it has proved difficult to implicate specific hormones or show that measurement of circulating hormones can identify women who will go on to develop malignant disease. There are, however, more convincing data that a proportion of established cancers are dependent upon steroid hormones for their continued growth and these underpin the use of endocrine manoeuvres in the treatment of these malignancies. Increased knowledge of the synthesis, release and mechanism of action of steroid hormones has led to the development of novel therapies for endocrine sensitive cancer and on-going research can reasonably be expected to identify tumour markers which can accurately predict hormone-dependency and provide better understanding of the mechanism by which response and resistance to therapy occur. The hope is that this knowledge will translate into more effective and rational endocrine treatment benefiting increased numbers of patients.

Preclinical studies on the broad-spectrum neuropeptide growth factor antagonist G

1. Antagonist G is a broad-spectrum neuropeptide growth factor antagonist that inhibits the growth of small cell lung cancer (SCLC) cells both in vitro and in vivo. 2. Antagonist G is metabolized in peripheral tissues by a chymotrypsin-like serine carboxypeptidase causing C-terminal deamidation and removal of the methionine residue. 3. The metabolites of Antagonist G retain neuropeptide antagonist properties and are thought to contribute to the parent peptide's antitumor activity. 4. Pharmacokinetic studies following systemic (IP) administration to nude mice revealed that the tissue distribution of Antagonist G is likely to be determined by vascular permeability. 5. Preclinical toxicology studies have been completed, and we have now started a phase I clinical trial.

BRCA1 5382insC mutation in sporadic and familial breast and ovarian carcinoma in Scotland

A restriction site-generating polymerase chain reaction (RG-PCR) assay was developed to detect the BRCA1 5382insC mutation that has been reported in multiple, apparently unrelated breast/ovarian carcinoma families. The assay has been used to screen tumour DNA from 250 breast cancer patients (aged 19-86 years) and from 80 ovarian cancer patients (aged 25-90 years) in a local population of patients with no known family history. Altogether, 0/80 (0%) ovarian and 1/250 (0.4%) breast tumour DNAs were found to have the 5382insC mutation. The sole positive case was a 26-year-old woman (BC185) with no known family history. One of the reasons for carrying out this analysis was that the 5382insC mutation had previously been shown to segregate with the disease in a very large Scottish 'West Lothian' kindred having breast/ovarian carcinoma. To investigate whether this apparently isolated case and the known family might be related, haplotypes for the markers D17S855, D17S1322, D17S1323 and D17S1327 were analysed. The mutant haplotype in the large kindred was identical to that reported in all other 5382insC mutation families for all markers with the exception of D17S1327. This implies that there has been a recombination event at the telomeric end of common ancestral haplotype in this family. Since the isolated case we identified carries the 'complete' common haplotype, it is unlikely that she is closely related to the West Lothian family.

Processing of [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P in xenograft bearing Nu/Nu mice

[D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P is a broad-spectrum neuropeptide growth factor antagonist that has exhibited in vitro activity against a range of human cancer cell lines. The fate of this compound in vivo following i.p. administration at 12 micrograms/g to nu/nu mice bearing the H69 small-cell lung cancer xenograft has been studied. Metabolism was confined to the C-terminus producing [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P acid and [D-Arg1,D-Phe5,D-Trp7,9]substance P(1-10). The peptide had a long half-life in plasma (45.9 min) and became widely distributed among the tissues studied with the highest accumulation observed in the liver (AUC 1102 micrograms/g x min) and the lowest in the brain (5 micrograms/g x min). Uptake into the tumor xenograft was poor (AUC 189 micrograms/g x min); however, uptake into the lungs was much greater (AUC 507 micrograms/g x min), offering encouragement that therapeutic concentrations may be targeted to primary lung tumors.

Expression of the extracellular matrix protein tenascin in malignant and benign ovarian tumours

The extracellular matrix protein tenascin (TN) is overexpressed in a number of solid tumours. Thi however, is the first study to examine TN expression in ovarian tumours. TN protein was examined in froze sections of 50 human ovarian tumours by immunohistochemistry. Malignant and borderline tumours showed significantly greater incidence and intensity of stromal staining than benign tumours (P < 0.0001 and P = 0.038 respectively). Seven omental metastases were also examined and showed a strikingly similar protein distribution to their primary tumour counterparts. The expression pattern of different RNA isoforms, created by alternative splicing of the primary transcript, was identified using reverse transcription-polymerase chain reactions (RT-PCR). The smallest TN RNA splice variant (284 bp) was found in all tumours examined, while the appearance of larger molecular weight transcripts (approximately 490 and 556 bp), as major forms, was predominantly limited to malignant tumours, with 9/12 malignant tumours showing this pattern compared with 1/6 benign tumours. These data suggest that malignant ovarian tumours have increased expression of TN compared with benign tumours and this may be associated with induction of specific isoforms.

Effect of Matrigel on the tumorigenicity of human breast and ovarian carcinoma cell lines

The effect of Matrigel, a solubilised tissue basement membrane extract, has been investigated on the tumorigenicity of 3 breast (MCF-7, T47D and MDA.MB.231) and 5 ovarian [PEO1, PEO1 cDDPr, PEO4, PEO14 and OV(hyg)CAR3] carcinoma cell lines. In the absence of Matrigel, the PEO14 and MDA.MB.231 cell lines produced take rates of 30% and 50%, respectively, while the other cell lines either did not develop or only occasionally developed as tumours. With Matrigel, 100% take rates were achieved for 7 of the 8 cell lines (MCF-7, T47D, MDA.MB.231, PEO1, PEO1 cDDPr, PEO4 and PEO14); in the remaining cell line [OV(hyg)CAR3] 2/6 (33%) tumours grew. Xenografts established with Matrigel could be transferred into recipient animals and grown in the absence of Matrigel, suggesting that Matrigel is necessary only for initial establishment of tumours. Furthermore, cells which had been re-established from a T47D xenograft and then inoculated into mice without Matrigel showed a take rate greater than that of the original cell line but less than that of the xenograft. In conclusion, Matrigel has proven to be extremely useful in establishing a variety of cell lines as xenografts.

Metabolism of the broad-spectrum neuropeptide growth factor antagonist: [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-substance P

Broad-spectrum neuropeptide growth factor antagonists, such as [D-Arg1, D-Phe5, D-Trp7,9, Leu11]substance P (antagonist D) and [Arg6, D-Trp7,9, NmePhe8]substance P(6-11) (antagonist G), are currently being investigated as possible anti-tumour agents. These compounds are hoped to be effective against neuropeptide-driven cancers such as small-cell lung cancer. Antagonist D possesses a broader antagonistic spectrum than antagonist G and hence may be of greater therapeutic use. The in vitro metabolism of antagonist D has been characterised and the structures of two major metabolites have been elucidated by amino acid analysis and mass spectrometry. Metabolism was confined to the C-terminus where serine carboxypeptidase action produced [deamidated]-antagonist D (metabolite 1) and [des-Leu11]-antagonist D (metabolite 2) as the major metabolites. Biological characterisation of the metabolites demonstrated that these relatively minor changes in structure resulted in a loss of antagonist activity. These results provide some of the first structure-activity information on the factors that determine which neuropeptides these compounds inhibit and on the relative potency of that inhibition.

Pharmacokinetics, metabolism and tumour disposition of 8-chloroadenosine 3',5'-monophosphate in breast cancer patients and xenograft bearing mice

BACKGROUND

8-Chloroadenosine 3',5'-monophosphate (8-Cl-cAMP) is undergoing phase I clinical trials as an anticancer drug. However, there is debate as to whether it is a prodrug for its 8-Cl-adenosine metabolite.

DESIGN

Pharmacokinetics, metabolism and tumour disposition studies have been performed in 7 breast cancer patients receiving continuous infusion (28 day) 8-Cl-cAMP (0.54 or 1.08 mg/kg/day) and tumour biopsies were obtained before and on the last day of infusion. Parallel studies were performed in nude mice bearing the HT29 human colon cancer xenograft after continuous infusion (7 day) of active drug doses (50 or 100 mg/kg/day).

RESULTS

Steady state plasma levels (Css) of 8-Cl-cAMP in patients ranged from 0.15-0.72 microM but 8-Cl-adenosine was not detected in plasma. In contrast, 8-Cl-cAMP was not detectable in 3 tumour biopsies but 8-Cl-adenosine was present in 2 samples at high concentrations (1.33 and 2.02 microM). In mice, Css of 8-Cl-cAMP ranged from 3.2-4.6 microM and 8-Cl adenosine was present in plasma only at the higher dose (100 mg/kg/day, peak concentration of 2.3 microM). In the HT29 xenograft, 8-Cl-cAMP levels were considerably lower than in plasma (0.37-1.22 microM) while 8-Cl-adenosine was present at 5.3-21.0 microM and 8-Cl-AMP was found at 11.3-35.7 microM.

CONCLUSIONS

The fate of 8-Cl-cAMP in human tumours is characterised by extensive metabolism to products which are not generally observed in plasma. These data raise the possibility that 8-Cl-cAMP is a prodrug for a product of its metabolism in human tumours.

The prognostic value of epidermal growth factor receptor mRNA expression in primary ovarian cancer

The expression of mRNA for the epidermal growth factor (EGF) receptor, EGF and transforming growth factor alpha (TGF-alpha) was determined in 76 malignant, six borderline and 15 benign primary ovarian tumours using the reverse transcriptase-polymerase chain reaction and related to clinical and pathological parameters. Of the malignant tumours, 70% (53/76) expressed EGF receptor mRNA, 31% (23/75) expressed EGF mRNA and 35% (26/75) expressed TGF-alpha mRNA. For the borderline tumours, four of six (67%) expressed EGF receptor mRNA, 1/6 (17%) expressed TGF-alpha mRNA and none expressed EGF mRNA. Finally, 33% (5/15) of the benign tumours expressed EGF receptor mRNA, whereas 40% (6/15) expressed EGF mRNA and 7% (1/15) expressed TGF-alpha mRNA. The presence of the EGF receptor in malignant tumours was associated with that of TGF-alpha (P = 0.0015) but not with EGF (P = 1.00), whereas there was no relationship between the presence of EGF and TGF-alpha (P = 1.00). EGF receptor mRNA expression was significantly and positively associated with serous histology (P = 0.006) but not with stage or grade. Neither EGF nor TGF-alpha showed any link with histological subtype or stage. The survival of patients with malignant tumours possessing EGF receptor mRNA was significantly reduced compared with that of patients whose tumours were negative (P = 0.030 for all malignant tumours; P = 0.007 for malignant epithelial tumours only). In contrast, neither the expression of TGF-alpha nor EGF was related to survival. These data suggest that the presence of EGF receptor mRNA is associated with poor prognosis in primary ovarian cancer.

Cyclic adenosine 3',5'-monophosphate-binding proteins in human ovarian cancer: correlations with clinicopathological features

The regulatory subunits of protein kinase A, or cyclic AMP-binding proteins, were measured in a series of 107 human ovarian tumors (89 malignant, 7 borderline, and 11 benign tumors) and related to tumor clinicopathological features and patient survival. Total cyclic AMP-binding protein levels were not significantly different between malignant tumors and either borderline or benign tumors. However, serous tumors showed significantly higher levels of total cyclic AMP-binding proteins than other malignant tumors (P = 0.007). Poorly differentiated tumors also possessed significantly higher levels of binding proteins as compared with well/moderately differentiated tumors (P < 0.01). Retrospective analysis of follow-up data also revealed a significant trend for patients with high tumor cyclic AMP-binding proteins to have poorer survival (P = 0.03). Individual binding proteins were identified by photoaffinity labeling, and the RI (Mr 48,000) protein was expressed as a percentage of total cyclic AMP-binding proteins detected. The percentage of the RI protein was not significantly different among malignant, borderline, or benign pathologies and was not associated with tumor stage, differentiation, or debulk status. The percentage of RI was significantly increased in serous tumors compared to other common epithelial malignancies (P = 0.01). In malignant tumors there was a significant positive correlation between the percentage of the RI protein and total cyclic AMP-binding proteins (P = 0.01). These data indicate that high tumor levels of cyclic AMP-binding proteins are associated with serous histology, poor differentiation, and poor patient survival.

Expression of the heat shock protein HSP27 in human ovarian cancer

The relationship of the heat shock protein HSP27 in ovarian cancer to several biological and clinical parameters was investigated in a series of primary tumors and cell lines. Analysis of 72 primary tumors (54 malignant, 5 borderline, and 13 benign neoplasms) indicated that malignant tumors expressed higher HSP27 concentrations than benign tumors (median values, 0.56 versus 0.25 ng/microgram cytosolic protein; P = 0.032). Tumors from patients with advanced stage (stages II, III, or IV) disease contained significantly higher HSP27 concentrations than tumors from stage I patients (P = 0.018), and an HSP27 content >2.0 ng/microgram cytosolic protein was associated with reduced survival (P = 0.03). Tumors that had demonstrated progressive growth after chemotherapy had a significantly higher HSP27 content than tumors that were static or responsive (P = 0.022). These data indicate that HSP27 is associated with more aggressive malignant ovarian disease and with inherent resistance to chemotherapy. Concentrations of HSP27 were also correlated with indicators of estrogen sensitivity. Therefore, the HSP27 concentration correlated with the estrogen receptor (all tumors, P = 0.0014; malignant tumors only, P = 0.047) but not with the progesterone receptor concentration. Analysis of ovarian cancer cell lines in vitro and in vivo indicated that the HSP27 content was higher in cell lines that were estrogen receptor rich and whose growth was modulated by estrogen as compared with those that were not. Additionally, two estrogen receptor-rich ovarian carcinoma lines demonstrated a small but significant decrease in HSP27 levels in response to 17beta-estradiol in culture. These results suggest that HSP27 may help identify tumors responsive to estrogens.

Loss of heterozygosity at 11q22 correlates with low progesterone receptor content in epithelial ovarian cancer

Forty-seven epithelial ovarian cancers were analyzed for loss of heterozygosity (LOH) at D11S35 (11q22), close to the progesterone receptor (PR) gene, and for tumoral estrogen receptor (ER) and PR content. Thirty-eight of 47 tumors were informative, and, of these, 14 exhibited LOH. There was a significant association (P = 0.014) between D11S35 LOH and low tumoral PR content. For all informative tumors, there was no correlation between ER and PR; however, exclusion of tumors with LOH from the informative series revealed a linear correlation between tumoral ER and PR (P = 0.013), and established ER (P = 0.025) and PR (P = 0.05) content as significant factors in relation to patient survival. Patients with ER-rich tumors with D11S35 LOH had particularly poor survival compared with ER-rich, D11S35 heterozygous, no loss patients (P = 0.014). Analysis of the same tumors using two other microsatellites, D11S935 (11p13) and NM23 (17q22), showed no statistically significant relationships, although there were nonsignificant trends for the correlation of ER and PR expression in informative tumors without allele loss at these loci. We propose that genomic structural alteration at or close to the PR gene locus has biological and clinical sequelae in ovarian cancer.

Growth-control of human ovarian-carcinoma cells by insulin-like growth-factors

The role of the insulin-like growth factors (IGFs) in 3 cultured human ovarian cancer cell lines (PEO1, PEO4, PEO14) was investigated. All three cell lines express mRNA for IGF-I and the PEO14 cell line expresses mRNA for IGF-II. Protein expression of IGF-II was demonstrated in the PEO14 and PEO4 cell lines. All 3 cell lines expressed mRNA for the IGF type I, IGF type II and insulin receptors; the presence of type I IGF receptors was confirmed by immuno-cytochemistry. IGF-I and insulin markedly stimulated the proliferation of PEO1 and PEO4 but not PEO14 cells while all 3 lines were insensitive to the addition of exogenous IGF-II.

Characterization of the deamidase enzyme responsible for the metabolism of the anticancer peptide: H-Arg-D-Trp-NmePhe-D-Trp-Leu-Met-NH2

H-Arg-D-Trp-NmePhe-D-Trp-Leu-Met-NH2, a broad spectrum neuropeptide growth factor antagonist (antagonist G), is soon to enter a phase I clinical trial for the treatment of small-cell lung cancer (SCLC). The pre-clinical pharmacology of this peptide has revealed that its metabolism proceeds from the C-terminus via deamidation. In this study the class of enzyme responsible for the degradation of antagonist G has been characterized. Tissue distribution studies on the enzyme have shown it to be very widespread with high specific activity being detected in the spleen, kidney, H69 SCLC xenograft and liver (12.64, 9.58, 8.00 and 6.94 nmols G/mg protein/hr, respectively). HPLC gel filtration indicated that the G-deamidase enzyme had an apparent molecular mass of 81 kDa. The sub-cellular distribution of the enzyme using differential centrifugation indicates that it is largely soluble with > 85% of the activity located in the cytosolic fraction. The distribution of activity towards antagonist G closely resembles that of esterase and acid carboxypeptidase activity, two activities, along with deamidase activity, known to be possessed by serine carboxypeptidases. Studies using a range of protease inhibitors showed clear inhibition of metabolism by phenylmethylsulphonylfluoride and benzyloxycarbonylphenylalanine chloromethylketone, indicating that the enzyme is a chymotrypsin-like serine carboxypeptidase. This knowledge of the enzyme will be invaluable in the further development of antagonist G and similar compounds. Moreover, the widespread distribution of this enzyme together with its broad specificity for C-terminal group suggests that it should be given serious consideration when designing C-terminally modified peptide drugs.