Epidermal and transforming growth factor alpha in patients with breast tumours

Transforming growth factor-α expression in benign and malignant human prostatic disease

Investigation of biological variables in prostatic disease may not only prevent patients with a good prognosis being overtreated, but allow better selection of appropriate therapy, and may identify potential targets for novel therapies. This study investigates the growth factor transforming growth factor-α (TGFα) expression in benign and malignant prostatic biopsies using both radioimmunoassay and immunohistochemistry, considering its role in malignant epithelial transformation and as a prognostic indicator. Biochemical methods were less satisfactory than the more selective immunohistochemical methods, due to the heterogeneity of prostatic tissue. Seventy-one percent of benign biopsies (range 0-18.62ng/mg DNA) and 69% of malignant biopsies (range 0-11.1ng/mg DNA) had detectable levels of TGFα using radioimmunoassay. Immunohistochemical staining for TGFaL identified expression in 15% of benign (4 out of 27) and 53% malignant biopsies (18 out of 34). Positive staining was also identified in premalignant lesions and within stromal elements, thus implying the factor's role in autocrine/paracrine growth and/or malignant transformation. Immunostaining for TGFα may enhance detection of premalignant lesions and small foci of malignant glands which are otherwise difficult to identify using standard histopathological techniques.

Breast Cancer Genetic and Molecular Subtype Impacts Response to Omega-3 Fatty Acid Ethyl Esters

Epidemiological studies have correlated frequent omega-3 (n-3) fatty acid consumption with a lower risk for breast cancer; however, recent prospective studies have been less conclusive. Efforts in the preventive setting have focused on the use of n-3 fatty acids, and the pharmaceutical ethyl esters (EE) of these natural compounds, for high-risk patient populations. Limited understanding of specific mechanisms by which these agents function has hampered identification of the cancer subtype(s) that would gain the greatest therapeutic benefit. In this study, we investigated the in vitro effects of n-3 EEs in four distinct breast cancer subtypes and explored how they affect not only breast cancer cell survival but also modulate the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) and peroxisome proliferator-activated receptor gamma signaling pathways. Similar to the high variance in response observed in human studies, we found that the effectiveness of n-3 EEs depends on the molecular characteristics of the MCF-7, CAMA-1, MDA-MB-231, and SKBR3 breast cancer cell lines and is closely associated with the suppression of NF-κB. These data strongly suggest that the use of n-3 fatty acids and their pharmaceutical ether esters in the prevention and therapeutic setting should be guided by specific tumor characteristics.

Transforming growth factor alpha dependent cancer progression is modulated by Muc1

Transforming growth factor alpha (TGFalpha) is a potent inducer of cellular transformation, through its binding and activation of the epidermal growth factor receptor (EGFR). Previous studies in our laboratory showed that EGFR could also be affected by the glycoprotein MUC1, which inhibits ligand-stimulated degradation of EGFR in breast epithelial cell lines. To determine the effect of Muc1 expression on TGFalpha/EGFR-dependent breast transformation, we crossed the WAP-TGFalpha transgenic mouse model of breast cancer onto a Muc1-null background. We found that the loss of Muc1 expression dramatically affects mammary gland transformation and progression. Although 100% of WAP-TGFalpha/Muc1(+/+) mice form mammary gland tumors by 1 year, only 37% of WAP-TGFalpha/Muc1(-/-) form tumors by this time. This difference is also associated with a delay in onset, with a doubling of onset time observed in the WAP-TGFalpha/Muc1(-/-) compared with the WAP-TGFalpha/Muc1(+/+) mice. Analysis of signal transduction pathways revealed that activation of cyclin D1 expression is significantly suppressed in tumors derived from WAP-TGFalpha/Muc1(-/-) animals compared with those expressing Muc1. The loss of Muc1 expression also results in a significant inhibition in the formation of hyperplastic lesions during tumor progression. On the C57Bl/6 inbred background, pulmonary lesions were observed in 28 of 29 WAP-TGFalpha/Muc1(+/+) animals (including one metastatic pulmonary adenocarcinoma and multiple perivascular lymphomas), although none were detected in the WAP-TGFalpha/Muc1(-/-) animals. Together, these data indicate that Muc1 is an important modulator of TGFalpha-dependent tumor progression.

Effects of tamoxifen on human squamous cell carcinoma lines of the head and neck

Tamoxifen (TAM) is a well-tolerated compound in the treatment of breast cancer and is primarily considered to act by competition with estrogen receptors (ER). Here we investigated the in vitro efficacy and potentially underlying mechanisms of TAM in established cell lines of squamous cell carcinomas of the head and neck (SCCHN). Using proliferation and apoptosis assays the antitumor activity of TAM in five SCCHN and the breast carcinoma line MCF-7 (positive control) was determined. MCF-7 was more sensitive to low-dose TAM (below 1 microM), whereas SCCHN showed significant growth inhibition at higher TAM concentrations (5-10 microM). Growth curve analysis and apoptosis assays were indicative for a cytostatic effect of low-dose TAM and high-dose TAM led to cell loss by apoptosis in sensitive SCCHN. In order to further characterize the observed antitumor effects we determined the amount of steroid hormone receptors with the dextran-coated charcoal method and immunocytochemistry. In addition, production of transforming growth factor (TGF-)-alpha, -beta1 and -beta2 was measured by ELISA, and protein kinase C (PKC) activity was assessed with a radioligand assay. Except MCF-7, none of the SCCHN lines was positive for ER. TAM caused decreased TGF-alpha and increased TGF-beta levels in MCF-7, but not in SCCHN supernatants. Furthermore, the antiestrogen reduced PKC activity in MCF-7, but not in SCCHN. In the present in vitro system, the observed antitumor activity of high-dose TAM in SCCHN cannot be explained by estrogen antagonism, alterations of TGF-alpha/beta levels or decreased PKC activity.

The primary use of endocrine therapies

Primary endocrine therapy is potentially superior to primary chemotherapy in patients with ER-positive tumors. The ability to give endocrine therapy perioperatively may be a better test than chemotherapy of the hypothesis that the events accompanying surgery affect prognosis. However, a major problem in all studies of primary endocrine therapy is that there has been no clear experimental test of preoperative versus postoperative therapy. This is because the major thrust of treatment has been in the elderly with the purpose of determining whether surgery can be avoided altogether. The fact that in ER-positive tumors primary endocrine therapy is associated with similar response rates to chemotherapy make it an attractive therapy for older women. This is the group where adjuvant chemotherapy has not been adequately tested (> or = 70 years of age). In contradistinction, adjuvant endocrine therapy shows marked survival benefits in patients with ER-positive tumors in these age groups (Table 1). It appears likely that primary endocrine therapy will allow breast conservation and prognostic information as is seen with chemotherapy. A major question which requires answering is whether primary endocrine therapy will improve survival more than adjuvant therapy alone. Although ER status is a good marker of responsiveness, its specificity, in particular, is not optimal. The ability to assess the dynamic effects of primary endocrine therapy by sequential biopsy and measurement of biological responses to oestrogen deprivation may allow us to predict precisely the patients likely to benefit from treatment. This clinical scenario allows us to use other potentially useful assessments such as the non-invasive estimation of angiogenesis using quantitative imaging techniques of blood flow. The newer anti-estrogens and aromatase inhibitors appear ideally suited to primary therapy since they have rapid and profound inhibitory activities, few or no agonist effects, and low side effect profiles. A preoperative trial of Faslodex is planned by the EORTC and another with Arimidex is under consideration by the ATAC (Arimidex, tamoxifen and combined) Trialist Group (Fig. 7). The precise design of these studies will require considerable thought.

EGF-related peptides in the pathophysiology of the mammary gland

Normal mammary gland development is the result of complex interactions between a number of hormones and growth factors. Normal and malignant human mammary epithelial cells are able to synthesize and to respond to various different, locally acting growth factors and growth inhibitors. Among these, the EGF-related peptides play an important role in regulating the proliferation and differentiation of human mammary epithelial cells. EGF4 and TGF4 are able to stimulate the lobulo-alveolar development of the mammary gland in vivo as well they are involved in the pathogenesis of human breast cancer. Experimental evidence suggests that estrogen-induced proliferation of breast carcinoma cells is mediated in part by EGF-related growth factors. It has also been demonstrated that activation of certain cellular protooncogenes such as c-Ha-ras in human mammary epithelial cells results in cellular transformation and in an increased production of several EGF-related growth factors such as TGFalpha and amphiregulin. Coexpression of both EGF-related peptides and their own receptors frequently occurs in human breast carcinomas and in human breast cancer cell lines, suggesting that an autocrine pathway of uncontrolled cell growth sustains neoplastic transformation.

Effect of a cytotoxic analog of LH-RH (T-98) on the growth of estrogen-dependent MXT mouse mammary cancers: correlations between growth characteristics and EGF receptor content of tumors

Female BDF mice bearing estrogen-dependent MXT mouse mammary cancers were treated for 4 weeks with a cytotoxic analog of luteinizing hormone-releasing hormone (LH-RH). T-98 (agonist [D-Lys6]LH-RH linked to glutaryl-2(hydroxymethyl)anthraquinone). The effects of T-98 were compared to those of equimolar amounts of the cytotoxic moiety 2-(hydroxymethyl)anthraquinone hemiglutarate (G-HMAQ) and carrier LH-RH agonist [D-Lys6]LH-RH. Both T-98 and [D-Lys6]LH-RH significantly inhibited the growth of MXT cancers, but G-HMAQ had only a minor non-significant effect. Cytotoxic analog T-98 and the carrier [D-Lys6]LH-RH had similar inhibitory hormonal activities on the pituitary-gonadal axis, but T-98 caused a larger reduction in tumor volume and decreased proliferation characteristics such as mitotic activity and AgNOR numbers in tumor cells to a greater extent than the carrier. Tumor inhibition by T-98, [D-Lys6]LH-RH, and ovariectomy was connected with a significant decrease in binding capacity of EGF receptors in tumor cell membranes. The concentration of EGF receptors remained high in tumors that continued to enlarge in spite of treatment and in all control untreated tumors, even those of small size. Thus, the changes in EGF receptors are likely to be the result of the therapy. Treatment with T-98 caused a greater reduction in the binding capacity of EGF receptors in tumors than [D-Lys6]LH-RH. This could explain the higher inhibitory effect of the cytotoxic analog on tumor growth. Since radiolabeled T-98 was shown to accumulate in MXT cancers 3 hours after a subcutaneous injection, this indicates that specific targeting might play a role in the antitumor effect exerted by this cytotoxic analog.

Serum transforming growth factor alpha level as a marker of hepatocellular carcinoma complicating cirrhosis

BACKGROUND

Transforming growth factor alpha (TGF alpha) is alleged to play a role in malignant progression as well as normal cell growth in an autocrine manner and its serum levels have been reported to increase during this progression. Most hepatocellular carcinomas (HCC) develop in cirrhotic livers in which hepatocyte necrosis and regeneration prevail. The significance of serum TGF alpha levels in the diagnosis of HCC complicating cirrhosis should be clarified.

METHODS

One hundred twenty-four patients with cirrhosis were studied, 80 with HCC (HCC) patients and 44 without (LC) patients. There was no difference in clinical features between the two groups. One hundred eighty-two healthy adults were also studied as controls. Serum TGF alpha levels were measured by enzyme-linked immunosorbent diffusion assay (ELISA).

RESULTS

Serum TGF alpha levels were significantly higher in HCC patients than in healthy adults or LC patients (mean +/- SD: 45 +/- 40 vs. 21 +/- 15 or 25 +/- 19 pg/ml, respectively). In LC patients, serum TGF alpha levels were significantly correlated with serum albumin and total bilirubin levels (r = -0.44 and 0.32, respectively). When the cutoff level was defined as 25 pg/ml from receiver operating characteristic curve, sensitivity and specificity for the diagnosis of HCC in the presence of cirrhosis were 69% and 66%, respectively. Serum TGF alpha levels were decreased after successful treatment for HCC in 60% of the HCC patients. Serum TGF alpha levels showed no correlation with serum alpha-fetoprotein levels; the levels were greater than 25 pg/ml in 67% of the HCC patients whose serum alpha-fetoprotein levels were within 20 ng/ml.

CONCLUSION

Serum TGF alpha levels may provide useful information for the diagnosis of HCC developing in the presence of cirrhosis.

Transforming growth factor alpha and epidermal growth factor levels in bladder cancer and their relationship to epidermal growth factor receptor

We have examined levels of epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) in neoplastic and non-neoplastic bladder tissue using a standard radioimmunoassay technique. Tumour samples had much higher TGF-alpha levels compared with EGF and TGF-alpha levels in malignant tissue were significantly higher than in benign bladder samples. There was, in addition, a difference in mean EGF levels from 'normal' bladder samples from non-tumour bearing areas of bladder in patients with bladder cancer compared with 'normal' bladder tissue obtained at the time of organ retrieval surgery. Levels of EGF and TGF-alpha did not correlate with levels of EGF receptor (EGFR) as determined by a radioligand binding method but levels of TGF-alpha > 10 ng gm-1 of tumour tissue did correlate with EGFR positivity defined using immunohistochemistry. These data suggest that TGF-alpha is the likely ligand for EGFR in bladder tumours.

Expression of endothelin-1 immunoreactivity in breast cancer

This study performed immunohistochemical staining for human ET-1, utilizing avidinbiotin-peroxidase complex detection to examine 47 surgically resected primary breast cancers. Positive immunoreactivity was demonstrated in 19 of the 47 breast cancers (40.4%). There was no significant relationship between the expression of ET-1 and clinicopathological findings. A significant difference was found between ET-1 positive and negative groups in the incidence of recurrence and distant metastasis (P < 0.05). The 5-year overall survival rate was significantly poorer in patients with ET-1-positive cancer (84.2%), compared to 96.4% in patients with ET-1 negative cancer (P < 0.01). The 5-year disease-free survival rate was significantly poorer in patients with ET-1-positive cancer (73.7%) compared to 96.4% in patients with ET-1-negative cancer (P < 0.05). These results suggest that the expression of ET-1 could be used as a possible indicator for predicting the metastatic potential of breast cancer.

Midkine and pleiotrophin expression in normal and malignant breast tissue

BACKGROUND

Some growth factors may promote tumor growth by affecting tumor angiogenesis. The angiogenic growth factor, pleiotrophin, was demonstrated previously in human breast carcinoma tissues; however, the pattern of pleiotrophin expression in normal breast tissues has not been established.

METHODS

The expression of pleiotrophin and the related growth factor, midkine, was examined by polymerase chain reaction amplification of reverse transcriptase copies of RNA transcripts (RT-PCR) from freshly resected normal and malignant human breast tissues. Northern blot analysis of midkine expression was performed on a limited number of the specimens and on human and canine breast carcinoma cell lines. Clinicopathologic variables from the breast cancer patients were examined in relation to the growth factor expression patterns.

RESULTS

The majority of both malignant and normal breast tissues expressed pleiotrophin. In contrast, midkine was expressed frequently in the malignant breast tissues but in only one of the normal specimens. Northern blot analysis of the breast carcinoma cells lines showed that they commonly expressed midkine transcripts. The only correlation of the growth factor expression patterns with the other clinical variables was the finding that the three midkine-negative breast carcinoma specimens also had low estrogen receptor levels.

CONCLUSIONS

By this analysis, the expression of pleiotrophin was equivalent in both malignant and normal human breast tissues. Midkine, on the other hand, exhibited increased expression in the breast carcinomas but showed much lower expression in the normal breast tissue. Although the cellular source of the midkine expression was not determined by the RT-PCR assay, the Northern blot analysis showed that isolated populations of breast cancer cells commonly express this growth factor. This is the first example of a tissue simultaneously expressing high amounts of both pleiotrophin and midkine, a finding of unclear pathophysiologic significance.

Immunolocalization of alpha-transforming growth factor in the developing rat mammary gland in vivo, rat mammary cells in vitro and in human breast diseases

Immunoreactive alpha-transforming growth factor (alpha-TGF) was shown by immunocytochemistry to be present in the rat mammary gland at various stages of development, the staining being most intense in mature myoepithelial cells. Alpha-TGF was also detected in the secretions of the mammary glands of pregnant and lactating rats. alpha-TGF in the extracts of rat mammary glands at each stage of development, and in several rat mammary cell lines and in culture medium in which they had been grown, was shown by Western blotting to consist primarily of a protein of molecular weight 50 kDa. The amount of this protein was greater in the mammary gland of the lactating rat than in resting or involuting glands. alpha-TGF was also found in some, but not all, human breast carcinomas, and in benign hyperplastic breast diseases.

Interaction of transforming growth factor-alpha and epidermal growth factor receptor in breast carcinoma. An immunohistologic study

BACKGROUND

Interaction of transforming growth factor-alpha (TGF-alpha) with its receptor, epidermal growth factor receptor (EGFR), has been implicated as an autoregulatory autocrine mechanism of breast epithelial proliferation.

METHODS

To examine the interrelationship and clinical relevance of TGF-alpha and EGFR in breast carcinoma, methanol-fixed cryostat sections from 73 patients were immunostained with monoclonal antibodies to epidermal growth factor (EGF), EGFR, and TGF-alpha.

RESULTS

Neither EGFR nor TGF-alpha staining was diagnostic or specific for the detection of malignant neoplastic cells. Both exhibited staining along the basal lamina of most benign ducts and lobules. TGF-alpha staining was observed in neoplastic cells in 41% and in non-neoplastic cells (peritumoral stroma and benign duct/lobular epithelium) in 36% of patients. Staining for EGF and TGF-alpha failed to correlate with node status or grade; however, TGF-alpha negative tumors were more frequently positive for estrogen receptor (ER) (70% versus 14%; P = 0.03). The presence of EGFR correlated with positive lymph node status (P = 0.004), poor differentiation (P = 0.001), and negative ER status (P = 0.0001). EGFR staining was more common in neoplasms which recurred, but this approached significance only in the group with node-negative disease (mean follow-up, 52 months; P = 0.06), and neoplastic cell TGF-alpha correlated with disease recurrence in patients with node-positive disease (no recurrence, -13% positive versus recurrence, -52% positive; P = 0.01). Concurrent TGF-alpha/EGFR staining, present in 18% of tumors, also was predictive of disease recurrence (no recurrence, 3% positive for both versus recurrence, 31% positive for both, P = 0.03).

CONCLUSIONS

TGF-alpha is heterogeneously expressed in neoplastic and host-derived components of breast tumors. Concurrent EGFR/TGF-alpha immunostaining may characterize a clinically aggressive subset of breast carcinomas, possibly reflecting autocrine interaction, and conferring growth advantage or metastatic phenotype.

Epidermal growth factor-related peptides in the pathogenesis of human breast cancer

A number of different epidermal growth factor (EGF)-related peptides such as EGF, transforming growth factor alpha (TGF alpha), amphiregulin (AR), heregulin (HRG), and cripto-1 (CR-1), are coexpressed to varying degrees in both normal and malignant mammary epithelial cells. However, in general the frequency and level of expression of TGF alpha, AR, and CR-1 are higher in malignant breast epithelial cells than in normal mammary epithelium. In addition, several of these peptides such as TGF alpha and AR can function as autocrine and/or juxtacrine growth factors in mammary epithelial cells, and their expression is stringently regulated by mammotrophic hormones such as estrogens, activated proto-oncogenes that have been implicated in the pathogenesis of breast cancer, and other growth factors. The redundancy of expression that is observed for a number of these structurally related peptides in both normal and malignant mammary epithelial cells suggests that some of these peptides may be involved in regulating other aspects of cellular behavior such as differentiation in addition to proliferation.

Urinary excretion of growth factors in patients with ovarian cancer

The levels of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) were analysed in 24-h urine samples from patients with ovarian malignancies, benign ovarian tumours, and healthy controls by specific radioimmunoassays. No significant difference in total urinary immunoreactive EGF excretion between the groups was detected. However, 79% (23/29) of the patients with ovarian carcinomas excreted TGF-alpha (median 12.6 pmol/24 h), whereas only 17% (2/12) of the patients with benign ovarian tumours and 23% (3/13) of the controls did so. The difference between cancer patients and controls was highly significant (P < 0.001). Analyses of the urine samples separated by gel filtration revealed a greater molecular heterogeneity of EGF and TGF-alpha in cancer patients than in controls. High and low molecular weight forms of EGF were able to bind to the EGF receptor and to induce anchorage-independent growth. After surgical reduction of the tumour, a distinct decrease of urinary high molecular weight forms was observed. Thus, some macromolecular growth factors seem to be associated with epithelial ovarian carcinomas.

Down-regulation of transforming growth factor-alpha by tamoxifen in human breast cancer

BACKGROUND

The influence of tamoxifen treatment on transforming growth factor-alpha (TGF-alpha) levels in human breast cancer rarely has been studied in vivo.

METHODS

Postmenopausal patients with estrogen receptor (ER)-positive and progesterone receptor (PR)-positive primary breast cancer underwent two fine-needle aspiration biopsies (FNA) of the tumors. Between the two FNAs, 10 patients received no treatment (control group), and the other 10 patients received tamoxifen (20 mg/day) for 10 (8-12) days (TAM group). TGF-alpha levels in FNA samples were assayed by enzyme immunoassay.

RESULTS

No significant difference was found in TGF-alpha levels between the first and second FNA samples in the control group. On the other hand, in the TAM group, TGF-alpha levels in the second FNA samples (2.5 +/- 0.5; mean +/- SEM ng/mg.DNA) were significantly (P < 0.01) lower than those in the first (4.5 +/- 0.8). Studies on the influence of tamoxifen treatment on TGF-alpha levels in ER-negative and PR-negative breast cancer showed that TGF-alpha levels were not affected by tamoxifen treatment. Positivity of epidermal growth factor receptor (EGFR) was 60% in ER-negative and PR-negative breast cancer and 30% in ER-positive and PR-positive breast cancer.

CONCLUSIONS

Tamoxifen downregulates TGF-alpha levels in ER-positive and PR-positive breast cancers through ER. The significance of TGF-alpha as an autocrine growth factor appears to be more important in ER-negative and PR-negative breast cancer with high EGFR positivity than in ER-positive and PR-positive breast cancer with low EGFR positivity.

TGF alpha and TGF beta expression in mammary carcinoma

TGF alpha and beta expression was examined using rabbit polyclonal antibodies and immunohistochemistry on a series of 195 breast carcinomas. TGF alpha immunoreactivity was observed in all but nine of the tumours, with over 50 per cent staining strongly. The polyclonal TGF alpha antibody (CIM1), when compared with a commercially available mouse monoclonal TGF alpha antibody used on the same sections, gave a good correlation (r = 0.52, P < 0.001). Both TGF alpha antibodies produced a granular cytoplasmic staining pattern, that with CIM1 being coarser, suggestive of binding to an aggregated protein or organelle. Eighty-one per cent of tumours stained with the TGF beta antibody, 35 per cent strongly. There was significant co-expression of TGF alpha and TGF beta (P < 0.001). However, they were not found to be useful prognostic indicators, lacking any significant correlation with histological classification, tumour size, nodal status, oestrogen receptor status, S-phase fraction, or overall survival over a 9-12 year period. The expression of these growth factors in most breast carcinomas suggests that they have important biological roles, but the exact nature of these roles remains unclear at the moment.

Epidermal growth factor in human breast cancer, endometrial carcinoma and lung cancer. Its relationship to epidermal growth factor receptor, estradiol receptor and tumor TNM

Epidermal growth factor (EGF) and its receptor (EGFR) were measured in 60 breast cancers (BC), 6 benign mammary tumors (BM), 8 samples of normal breast (NB), 6 endometrial carcinomas (EC) and 30 lung cancers (LC). EGF was measured in plasma, saliva and urine from 20 patients with BC, before and after tumor excision, and in 8 patients with metastatic disease. The median EGF in BM and BC was significantly higher (P < 0.05) than in NB. No significant correlation between EGF and EGFR was found in BC. Neither tumor excision nor the spreading of the disease significantly modified the EGF concentrations in biological fluids. In LC there was an inverse relationship between EGF and EGFR (rs = -0.36; P = 0.09), which disappeared in normal lung. It is concluded that EGF may play a role in malignant transformation; however, the weak correlation between EGF and EGFR lessens the importance of EGF in either autocrine or paracrine stimulation of tumor growth.

Tyrosine kinase receptor--nuclear protooncogene interactions in breast cancer

In summary, evidence is beginning to accumulate in support of a major role for tyrosine kinase receptors (and their activating growth factors) and steroid hormones and their receptors in normal development and differentiation of the mammary gland. A point of intersection of their mechanisms of action in growth control appears to be the induction of nuclear protooncogenes such as c-myc. When c-myc is amplified, as it is in many breast cancers, EGF and FGF receptor tyrosine kinase action becomes transforming, not simply mitogenic. A source of the transforming factors could be either stromal or epithelial. This mechanism could function early in the progression of breast cancer. c-erbB-2 and EGF receptor overexpression and amplification, when they occur, appear to render tumors even more malignant and of especially poor prognosis. These mechanisms could function late in the progression of breast cancer. Transgenic mouse studies have begun to echo these themes. They have established that a growth factor (TGF-alpha) and its receptor (EGF receptor), which appear to be important in normal mouse and human proliferation and gland development, and a protooncogene (c-myc), commonly amplified and overexpressed in human and mouse breast cancer, can each contribute to mammary carcinogenesis. The mechanisms of the two are likely to be distinct. myc is likely to be acting as a tumor initiator in combination with normal proliferative factors, whereas TGF-alpha is likely to be acting as a hyperproliferative (promotional) factor in combination with a normal background of mutational events. The role of unmutated but amplified erbB-2 in the transgenic mouse is not yet known.

Epidermal growth factor-like activity and epidermal growth factor-receptors in human primary breast cancer

Ligands binding to epidermal growth factor-receptors (EGF-Rs) as epidermal growth factor-like activity (EGF-like activity), along with EGF-R levels, were determined from human primary breast cancer samples. Receptor analysis revealed a single class of high affinity binding sites. Ng/mg protein EGF-like activity quantities were measured in cytosols, and were inversely correlated with EGF-R contents (p < 0.01), estimated by two-point assays.

Autocrine growth factors and solid tumor malignancy

The ability of malignant cells to escape the constraint that normally regulate cell growth and differentiation has been a primary focus of attention for investigators of cancer cell biology. An outcome of this attention has been the discovery that the protein products of oncogenes play a role in the activation of growth signal pathways. A second outcome, possibly related to abnormal oncogene expression, has been the discovery that malignant cells frequently show an ability to regulate their own growth by the release of autocrine growth modulatory substances. Most important, the growth of certain malignant cell types has been shown to depend on autocrine growth circuits. A malignant tumor whose continued growth depends on the release of an autocrine growth factor may be vulnerable to treatment with specific receptor antagonists or immunoneutralizing antibodies designed to break the autocrine circuit. Information is rapidly emerging concerning autocrine growth factors in selected human solid tissue malignancy.

Steroid receptors in breast cancer

Recent advances in steroid receptor structure and function now indicate that oestrogen binds to the oestrogen receptor (ER) molecule at a specific site, denoted region E. This allows binding of the oestrogen-ER complex to DNA via cysteine residues in region C of the ER molecule, which tetrahedrally co-ordinate zinc. This modulates transcription and stimulates cell growth. A number of newly discovered growth factors are also regulated by ER, as is the progesterone receptor. Steroid receptor concentrations in tissues can now be measured on smaller tissue samples using enzyme immunoassay or on cells obtained by fine needle aspiration using monoclonal antibody technology. The prognostic value of steroid receptor is limited, but still constitutes the best marker for predicting response to endocrine therapy. The role of steroid receptors in selecting patients for adjuvant therapy is discussed.

Expression of transforming growth factor alpha (TGF alpha) in breast cancer

Transforming growth factor alpha (TGF alpha) is one growth factor that has been circumstantially implicated in regulating the autocrine growth of breast cancer cells. Expression of TGF alpha can be modulated by activated cellular protooncogenes such as ras and by estrogens. For example, the epidermal growth factor (EGF)-responsive normal NOG-8 mouse and human MCF-10A mammary epithelial cell lines can be transformed with either a point-mutated c-Ha-ras protooncogene or with a normal or point-mutated c-neu (erbB-2) protooncogene. In ras transformed NOG-8 and MCF-10A cells but not in neu transformed cells there is a loss in or an attenuated response to the mitogenic effects of EGF. This response may be due in part to an enhanced production of endogenous TGF alpha that is coordinately and temporally linked to the expression of the activated ras gene and to the acquisition of transformation-associated properties in these cells. TGF alpha mRNA and TGF alpha protein can also be detected in approximately 50-70% of primary human breast tumors. In addition, approximately 2- to 3-fold higher levels of biologically active and immunoreactive TGF alpha can also be detected in the pleural effusions from breast cancer patients as compared with the TGF alpha levels in the serous effusions of noncancer patients. Over-expression of a full-length TGF alpha cDNA in NOG-8 and MCF-10A cells is capable of transforming these cells. Finally, expression of TGF alpha mRNA and production of biologically active TGF alpha protein is also found in normal rodent and human mammary epithelial cells.

Transforming growth factor alpha and epidermal growth factor in human pancreatic cancer

Overexpression of the epidermal growth factor receptor (EGFR) has been reported as an important molecular abnormality in human pancreatic cancer. There is in vitro evidence that simultaneous overproduction of one of its ligands, transforming growth factor alpha (TGF-alpha), might result in an autocrine loop with an increased proliferation signal. We analysed by immunocytochemical staining a retrospective series of human pancreatic cancers, chronic pancreatitis, and normal fetal and adult pancreatic tissues for the presence of TGF-alpha and epidermal growth factor (EGF). Ductal epithelial cells showed TGF-alpha immunoreactivity in both normal tissue and chronic pancreatitis, and 95 per cent of tumours showed strong immunoreactivity. In contrast, EGF immunoreactivity was not found in normal pancreas, but was expressed in 12 per cent of pancreatic carcinomas. Well-defined areas of EGF immunoreactivity in exocrine ducts showing reactive changes in pancreatitis might represent a benign response to tissue damage similar to that previously described in the gastric mucosa.

A comparison of the growth promoting properties of ascitic fluids, cyst fluids and peritoneal fluids from patients with ovarian tumours

The growth promoting properties of ascitic fluids, cyst fluids and peritoneal fluids from patients with ovarian malignancy, benign ovarian tumours and non-tumour related gynaecological conditions have been investigated using an ovarian carcinoma cell line (OAW 42), mesothelial cells (58MC) and rat kidney cells (NRK-49F). Colony stimulating activity (CSA) for tumour cells and transforming activity (TA) for mesothelial cells were weakly correlated, but whereas elevated TA was tumour-associated, CSA was not. However, TA was not cancer-associated and, although the difference between the mean TA values of benign and malignant cyst fluids was of borderline significance, some benign cyst fluids from cystadenomas showed high TA values. Higher levels of TA in the cystadenomas showed a significant correlation with the menopausal status of the patient and higher levels of TA in the malignant cyst fluid/peritoneal fluid groups were associated with more advanced disease. Results indicated that some fluids contained TGF-beta-like activity, but there was no direct evidence for the presence of TGF-alpha/EGF-like activity in the fluids. Heparin inhibited clonogenic growth of tumour cells but not mesothelial cells. The reduced CSA which was observed after treatment of fluids with both heparin and thrombin implicated coagulation factors in the manifestation of CSA. It was concluded that CSA in the fluids was due, at least partly, to fibrin coagulation, and TA was due to unknown growth factor(s) which may include TGF-beta-like activity. The results are discussed in the context of the aetiology of ovarian carcinoma, and the possible clinical significance of TA.

Stimulatory and inhibitory growth factors and breast cancer

While steroid hormones act as endocrine effectors of growth and development of normal breast and of carcinogenesis and progression of malignant breast, recent evidence suggests that local hormonal effectors also exist. These are the growth regulatory growth factors. This article summarizes current status of our understanding of structure and function of growth factors secreted by the normal and malignant mammary epithelium. While growth inhibitory factors and their receptors generally suppress development of the transformed phenotype and promote differentiation, growth stimulatory factors and their receptors may be necessary for both normal proliferation and early stages of malignant progression of breast cancer. Overexpression of two receptors, c-erbB-2 and EGF receptor, have also been associated with poor prognosis in the clinical disease.

Regulation of proliferation, invasion and growth factor synthesis in breast cancer by steroids

Endogenous ovarian estrogens and progestins appear to play a critical role in the development and progression of breast cancer. Local productions of growth factors probably also contribute to malignant proliferation, while production and activation of collagenolytic enzymes may be equally critical for local invasive processes. The current review focuses on characterization of growth factor-receptor systems operant in normal and malignant breast epithelium. In addition, the determinants of local invasion are reviewed: attachment, modality, and proteose secretion. Finally, data are discussed concerning the regulation of both proliferation and invasion by hormones and antihormonal agents in hormone-dependent breast cancer. The results suggest new potential pharmacologic targets to explore to suppress onset and progression of breast cancer.

Detection of transforming growth factor alpha in human urine and plasma

A sensitive enzyme-linked immunosorbent assay (ELISA) system for human transforming growth factor alpha (TGF alpha) was developed in combination with polyclonal and monoclonal antibodies. Employing this assay system, we detected TGF alpha like activity in normal human plasma as well as in cancer patients' urine and plasma. These TGF alpha were analyzed by chromatography, immunoreactivity, and EGF-TGF alpha receptor binding assay and found to be identical to authentic human TGF alpha. The presence of TGF alpha circulating in normal adult plasma suggests a new role of TGF alpha in the human body.

Growth factors and oncogenes in breast cancer

The growth of normal breast epithelial cells is regulated by a complex interacting system of polypeptide factors and by steroid hormones. The cells respond to these factors through receptors which generate mitogenic and other intracellular signals. These second messengers provoke complex responses which may ultimately result in DNA replication and cell division. A comparison of normal cells and tumour cells, either in culture or from primary tumour biopsies, has revealed differences in growth factor and growth factor receptor expression. Such changes may represent aspects of the process of malignant transformation. In addition some evidence suggests that changes in second messenger systems may also occur. Finally several changes in nuclear oncogenes have been observed in breast cancers. It has been proposed that changes in the nuclear oncogenes, perhaps involving the loss of function of tumour suppressor genes, may allow cells to enter the cell cycle. Changes in growth factors, their receptors or intracellular second messenger systems may stimulate unregulated growth. The combination of these events provide a model for the process of carcinogenesis.

The role of the epidermal growth factor receptor and the c-erbB-2 protein in breast cancer

Breast cancer cells are derived from epithelial cells lining the ducts of the breast. One of the fundamental characteristics that distinguish tumour cells from normal cells is that cancer cells grow in an apparently unregulated way. Understanding the mechanisms that regulate the growth and differentiation of normal breast epithelial cells and the differences between these systems in cancer cells is one of the central goals of research into the cell biology of breast cancer.

Approaches to studying the role of growth factors in the progression of breast tumours from the steroid sensitive to insensitive state

Progression from steroid sensitive to autonomous proliferation can be modelled in several cultured mammary tumour cell lines by long-term withdrawal of steroids. A feature of all the four systems studied thus far is that the basal growth in the absence of steroid increases with duration of steroid withdrawal until it reaches that obtained in the presence of steroid. It cannot be assumed that the increased proliferation in the absence of steroid is modulated by the same pathways as those stimulated by steroids in sensitive cells. Therefore, we feel that mechanisms of progression can best be studied via cell behaviour in the absence of steroid. With both the mouse S115 and human T-47-D systems, changes in sensitivity to several growth factors accompany progression; responses to TGF beta 1 are of particular interest in the T-47-D cells where this growth factor becomes stimulatory in the steroid insensitive state. This is accompanied by upregulation of TGF beta 1 mRNA. This upregulation of TGF beta agrees with the finding that ER - PR - primary human breast tumours contain more TGF beta 1 than do ER + PR + tumours; TGF alpha has the opposite pattern. Furthermore, only 40 and 30 kDa TGF beta species have been detected within cultured cells and primary tumours; TGF alpha exists in a 30 kDa form. The functions of these large forms of TGF alpha and TGF beta are unclear. Our conclusions from these experiments is that the increased proliferation in the absence of steroid accompanying progression may not be mediated by the same pathways as those perturbed by steroids in sensitive cells. Furthermore, TGF beta 1 may have different effects in steroid responsive and unresponsive cells.

Transforming growth factors in human breast cancer

Transforming growth factors alpha and beta (TGF alpha and TGF beta) are two growth factors which are frequently associated with a number of human breast cancer cell lines and with primary human breast carcinomas. Expression of TGF alpha protein and specific TGF alpha mRNA transcripts (4.8 and 1.6 kb) can be induced by estrogens in estrogen-responsive breast cancer cells, suggesting that the mitogenic effects of estrogen may in part be mediated through this potential autocrine growth factor. In contrast, anti-estrogens such as tamoxifen can increase the secreted levels of TGF beta, which is a potent growth-inhibitor for some human breast cancer cell lines. Anti-estrogens generally decrease TGF alpha production. TGF alpha mRNA expression has been detected in approximately 40-70% of primary human breast tumors, while expression of a 2.6 kb TGF beta mRNA transcript can be detected in 70-80% of breast tumors. Interference with (e.g. TGF alpha) or augmentation of (e.g. TGF beta) the effects of these two growth factors may have some potential clinical applications in the treatment of breast cancer.