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PubMed1997

The role of tumor-associated macrophages in the delivery of liposomal doxorubicin to solid murine fibrosarcoma tumors.

Murine fibrosarcoma tumors arising from subcutaneous inoculation of FSa-N cells exhibit 4-fold higher tumor-associated macrophage (TAM) levels than those from the FSa-R line. These solid tumors were used to assess the role of TAMs in the accumulation of liposomal anticancer drugs. Two liposomal formulations of doxorubicin were investigated: a conventional formulation composed of distearoylphosphatidylcholine (DSPC) and cholesterol and a sterically stabilized liposomal formulation composed of DSPC/cholesterol/poly (ethylene glycol)-modified distearoylphosphatidyethanolamine (PEG-PE). Circulating concentrations of PEG-PE containing liposomes 24 h after i.v. administration were 3-fold greater than those observed after administration of conventional liposomes. No differences were observed in drug retention or tumor (FSa-R or FSa-N) drug and liposomal lipid delivery when comparisons were made between different liposomal formulations. However, tumor doxorubicin concentrations were increased as much as 4-fold for liposomal formulations relative to free drug. Further, there was a 1.5- to 2-fold increase in doxorubicin delivery to TAM-enriched FSa-N tumors compared with FSa-R tumors. Fluorescence microscopy studies revealed a poor correlation between CD11b (Mac-1) positive cells (TAMs) and the appearance of doxorubicin fluorescence. These results suggest that uptake of liposomal drugs by TAMs does not account for the enhanced accumulation of liposomal drugs in solid tumors. Rather, the increased tumor drug delivery may be related to alternative TAM-mediated processes that increase tumor vascular permeability. Therapeutic studies demonstrated that increased tumor drug uptake observed for the liposomal doxorubicin formulations led to marginal improvements in antitumor activity, and it is suggested that much of the drug delivered in liposomal form is not biologically available.

Animals↗
PubMed1997

[Tamoxifen adjuvant delays early breast cancer. Results of a cooperative randomized trial].

Adjuvant tamoxifen (TAM) has been proved to reduce recurrence and mortality in early breast cancer, nevertheless many patients did not receive TAM as adjuvant therapy after local treatment. In order to study the efficacy of delayed TAM therapy in patients who were not given immediate adjuvant hormonal treatment, a multicenter randomized trial has been conducted by the French National Cancer Centers (FNCLCC). According to eligibility criterias all women with breast cancer who received curative local treatment at least 2 years before (surgery +/- radiotherapy) with or without adjuvant chemotherapy but no hormonal treatment could have been included. Between September 1986 and October 1989, 494 women were randomized to receive either TAM 30 mg/day for 5 years or no treatment. Patients' characteristics such as age, tumoral stage, number of positive nodes, receptors status and time from local treatment were equally distributed in the 2 groups. An improvement in the disease free survival in the TAM treated patients can be observed with a significative difference (p = 0.05), nevertheless the overall survival is not improved in the TAM group. In the same way, in nodes positive patients although no significative improvement in the overall survival can be observed, a significative improvement in the disease free survival (p = 0.05) can be noted. In estradiol receptors positive patients tamoxifen gives a significative reduction in the odds of death (p = 0.04) and recurrence (p = 0.03). The disease free improvement seems to be limited to 50 and more years old patients. The first results of this trial lead to prescribe tamoxifen to all postmenopausal women previously treated for an early breast cancer without adjuvant tamoxifen treatment.

Adult↗
PubMed1997

Prevention of breast cancer growth, invasion, and metastasis by antiestrogen tamoxifen alone or in combination with urokinase inhibitor B-428.

Urokinase (urokinase plasminogen activator, uPA) and its cell surface receptor (uPA receptor, uPAR) play an important role in a variety of physiological and pathological processes requiring cell migration and tissue remodeling. Using our syngeneic model of uPAR overexpression by the rat breast cancer cell line Mat B-III, we have examined the ability of the nonsteroidal antiestrogen, tamoxifen (TAM), and of a selective synthetic inhibitor of uPA, 4-iodo benzo[b]thiophene-2-carboxamidine (B-428), to inhibit expression of uPA and uPAR as well as cell growth, invasion, and metastasis of wild-type Mat B-III cells and of cells overexpressing uPAR (Mat B-III-uPAR). Both TAM and B-428 inhibited uPAR gene transcription, mRNA expression, protein production and also decreased the proliferative and invasive capacity of Mat B-III and Mat B-III-uPAR. The effects of TAM and B-428 were more pronounced when these agents were tested in combination. Both control and experimental cells (1 x 10(6) cells) were inoculated orthotopically into the mammary fat pad of syngeneic female Fisher rats, and animals were infused i.p. with either TAM and B-428 alone or in combination for 2 weeks. Control animals receiving vehicle alone developed large tumors and macroscopic metastases to lungs, liver, and lymph nodes. In contrast to this, experimental animals receiving TAM and B-428 showed a significant decrease in primary tumor volume and metastases. Combination therapy had especially marked effects in blocking progression of the primary tumor in experimental animals inoculated with highly aggressive Mat B-III-uPAR cells. These results underscore the utility of anti-proteolytic agents (B-428) in addition to standard hormone therapy (TAM) in advanced breast cancer patients where the uPA/uPAR system plays a key role in tumor progression.

Amidines↗
PubMed1998

Tamoxifen downregulates signal transduction and is synergistic with tiazofurin in human breast carcinoma MDA-MB-435 cells.

Breast carcinoma is a leading cause of cancer death in women in the US. Tamoxifen (TAM), an antiestrogen, is used as a chemopreventive and chemotherapeutic compound against human breast carcinoma. Tiazofurin (TR), an oncolytic C-nucleoside, inhibits IMP dehydrogenase activity, decreases cellular GTP pools, and downregulates ras gene expression. MDA-MB-435 cells are estrogen receptor negative human breast carcinoma cells that have elevated signal transduction activity. Because TR and TAM decrease signal transduction enzyme activity and inositol 1,4,5-trisphosphate (IP3) concentration via different mechanisms, we tested the hypothesis that the two compounds may be synergistic in human breast carcinoma cells. In MDA-MB-435 cells in growth inhibition assay, the IC50s for TR and TAM were (mean +/- SE) 17 +/- 1.2 and 12 +/- 1.1 microM; in clonogenic assays they were 4 +/- 0.3 and 0.7 +/- 0.3 microM, respectively. When TR was added to MDA-MB-435 cells, followed 12 h later by TAM, synergism was observed in growth inhibition and clonogenic assays and in the reduction of IP3 concentration. The latter may explain, at least in part, the synergistic action of TR and TAM in these cells. The synergistic action of TR and TAM may have implication in the clinical treatment of human breast carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

Monocyte chemoattractant protein-1 (MCP-1) expression in primary lymphoepithelioma-like carcinomas (LELCs) of the lung.

Lymphoepithelioma-like carcinoma (LELC) of the lung is a recently recognized primary non-small cell lung carcinoma with distinct clinicopathological features and an aetiological association with Epstein-Barr virus (EBV) infection. The tumour consists of clusters and sheets of poorly or undifferentiated tumour cells in close association with numerous mononuclear inflammatory cells, including a rich component of tumour-associated macrophages (TAMs). To investigate the molecular mechanism leading to the TAM-rich stroma, the expression of a monocyte-specific chemotactic and activating factor, monocyte chemoattractant protein-1 (MCP-1), was studied by reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization (ISH), and the presence of TAMs was demonstrated by immunohistochemistry in nine LELCs. The results were compared with those found in 17 conventional non-small cell lung carcinomas. RT-PCR showed specific MCP-1 amplification in both LELCs and non-LELCs, but ISH demonstrated a unique and extensive expression of MCP-1 transcripts by the tumour cells of LELCs only, while TAMs, stromal fibroblasts, and endothelial cells formed the major source of MCP-1 in non-LELCs. TAMs in LELCs were more abundant and showed a close topographical relationship with the MCP-1-expressing tumour cells. The results indicate that tumour cell expression of MCP-1 in LELCs is an important mechanism contributing to their distinctive morphological features. This is the first study that demonstrates the in vivo upregulation of a monocyte-specific chemokine by EBV-related carcinomas, illustrating an interesting aspect of tumour biology in EBV-related neoplasms.

Adult↗
PubMed1988

Effects of antiestrogen and progestin on immune functions in breast cancer patients.

Several immunologic variables were evaluated in 14 patients with untreated primary breast cancer and 20 postmastectomized patients undergoing tamoxifen (TAM) or high-dose medroxyprogesterone acetate (MPA) treatment. Immunologic evaluation in the peripheral blood included lymphocyte count, definition of T-lymphocyte subsets by monoclonal antibodies (OKT3, OKT11, OKT4, and OKT8), and lymphocyte blastogenic response to phytohemagglutinin (PHA) and Concanavalin A (Con A). Moreover, the in vitro effect of TAM and MPA on the blastogenic response of peripheral lymphocytes from normal female subjects was tested. Primary breast cancer patients did not differ from controls in any of the variables tested. Similarly, the immunologic variables of the group treated with TAM were normal, with the exception of a slight reduction of the OKT4+/OKT8+ ratio. In MPA-treated patients, a reduction of the percentage of OKT4+ cells and a decrease of the OKT4+/OKT8+ ratio were observed. Moreover, response to PHA was reduced sharply. However, the addition of interleukin-2 (IL-2) to the culture medium restored PHA response. Likewise, the in vitro addition of MPA to peripheral blood lymphocytes from normal female subjects resulted in a sharp dose-dependent depression of PHA response while TAM was ineffective completely. The inhibitory effect of MPA was not evident when IL-2 was added simultaneously to the culture medium. These results show that the administration of high-dose MPA may alter immunocompetence as defined by T-lymphocyte subsets and response to mitogens. The latter effect may be related to a diminished production of IL-2. In contrast, TAM does not appear to have a significant immunodepressant action either in vitro or in vivo.

Antigens, Differentiation, T-Lymphocyte↗
PubMed2003

K-ras mutation in tamoxifen-related endometrial polyps.

BACKGROUND: K-ras mutation is thought to occur at an early stage of neoplastic progression in the endometrium. The authors investigated mutations in codon 12 of K-ras in tamoxifen (TAM)-related endometrial polyps. METHODS: DNA was extracted from 11 frozen endometrial polyps from TAM-treated patients with breast carcinoma. Mutations were detected using the mutant allele-specific amplification method. The results subsequently were analyzed for correlations with immunohistochemical data that were obtained using antibodies against estrogen receptors (ERs; alpha and beta forms), progesterone receptors (PRs; A and B forms), and Ki-67. RESULTS: Mutations in codon 12 of K-ras were observed in 7 of 11 TAM-related endometrial polyps. Expression levels of ER-alpha and PR-B were high in the glandular epithelium and low in the stroma. PR-A expression was high in both the glandular epithelium and the stroma. In the glandular epithelium, expression of ER-beta appeared to be lower than expression of ER-alpha. The Ki-67 index in the glandular epithelium ranged from 2 to 38, whereas the index ranged from 0 to 4 in the stroma (P < 0.01). CONCLUSIONS: The incidence of mutations in codon 12 of K-ras in TAM-related endometrial polyps (64%) was greater than the incidence of these same mutations in sporadic endometrial hyperplasias (4.5-23%). High expression levels of ER-alpha, PR-A, and PR-B in the glandular epithelium were observed in all polyps, regardless of K-ras codon 12 mutation status and Ki-67 index. The authors' findings may support the hypothesis that the polyp-carcinoma sequence partly indicates the development of endometrial carcinoma in postmenopausal women who have been treated with TAM.

Aged↗
PubMed2005

Twelve-year mortality results of a randomized trial of 2 versus 5 years of adjuvant tamoxifen for postmenopausal early-stage breast carcinoma patients (SITAM 01).

BACKGROUND: This study evaluated the impact on overall survival (OS) of 2 versus 5 years adjuvant tamoxifen in early breast carcinoma patients after 12 years of follow-up. METHODS: Women with breast carcinoma T1-3, N0-3, M0, aged 50-70 years, were eligible for this multicenter randomized Phase III trial. Patients event-free after 2 years of tamoxifen therapy (TAM) were randomly assigned to stop or continue TAM (20 mg/day) for an additional 3 years. The primary endpoint was disease-free survival. Secondary endpoints included OS and toxicity. RESULTS: From 1989 through 1996, 1901 patients were randomly assigned either to stop treatment (n = 958) or to continue TAM (n = 943). Overall, 98% of patients alive at the previous report (n = 1611) had updated information about OS, of whom 549 had died. The median duration of postrandomization follow-up was 115 months (interquartile range, 86-137). No statistically significant differences between the two arms were detected in the whole population (hazard ratio [HR], 1.02; 95% confidence interval [CI], 0.86-1.22) and in estrogen receptor (ER)-positive patients (HR, 0.90; 95% CI, 0.72-1.13). In the latter group, survival curves started to diverge after 90 months, showing a trend in favor of the 5-year arm. In younger (age < or =55 yrs) ER-positive patients longer TAM was associated with a 44% decrease in the risk of death (HR, 0.56; 95% CI, 0.31-1.00), while no clear benefit was documented in women older than 55 years of age (HR, 0.98; 95% CI, 0.77-1.25). CONCLUSIONS: The benefits of longer TAM on OS start to emerge only after 9 years from diagnosis and seem to be more relevant in younger ER-positive women.

Age Factors↗
PubMed2007

Role of tumor-derived proinflammatory cytokines GM-CSF, TNF-alpha, and IL-12 in the migration and differentiation of antigen-presenting cells in cervical carcinoma.

BACKGROUND: Proinflammatory cytokines are important in modifying the activity, differentiation, and migration of antigen-presenting cells and may influence the survival of cancer patients. The study assessed whether GM-CSF, TNF-alpha, and IL-12, produced by cervical cancer cells, are important for the activity, differentiation, and migration of antigen-presenting cells. METHODS: In 90 patients with cervical carcinoma the number of monocytes/tumor-associated macrophages (TAM), mature dendritic cells (DC), and Langerhans cells (LHC) was determined using immunohistochemistry. An RNA in situ hybridization technique was used to measure the expression level of GM-CSF, TNF-alpha, IL-12p35, and IL-12p40. RESULTS: TAM were detected intraepithelial as well as in the stroma of the tumor. LHC were only detected intraepithelial and mature DC only in the tumor stroma. The number of TAM correlated positively with the number of mature DC. The expression levels of GM-CSF and TNF-alpha correlated positively with the number of TAM and DC. TNF-alpha showed a negative correlation with the number of LHC. A significant correlation between the expression of functional IL-12 (IL-12p40) and stromal TAM was found. The expression of GM-CSF, TNF-alpha, and IL-12p40 did not correlate significantly with disease-free survival. However, high IL-12p40 expression was associated with a favorable cumulative overall survival. CONCLUSIONS: The results suggest that GM-CSF as well as TNF-alpha, produced by cervical carcinoma cells, may play a role in the differentiation of monocytes into mature DC. Furthermore, TNF-alpha may influence the migration of LHC from the tumor.

Adenocarcinoma↗
PubMed2002

Prolactin regulates antitumor immune response through induction of tumoricidal macrophages and release of IL-12.

The involvement of PRL in regulating monocyte/macrophage functions is suggested by the presence of PRL-Rs in these cells. Here, we show that PRL, though it failed to activate mouse peritoneal resident macrophages (RMs), acted as a second signal and activated mouse peritoneal inflammatory macrophages (EMs) to a tumoricidal state. The cytotoxicity of mouse tumor-associated macrophages (TAMs) isolated at day 1 of tumor (Ehrlich ascites carcinoma, EAC) growth was enhanced by PRL. However, with progression of tumor growth, TAMs became nonresponsive to the hormone. PRL-induced killing of P815 target cells by EMs and TAMs was independent of TNF but correlated with the hormone-induced augmentation of NO2(-) and O2(-) release in these macrophages. Administration of PRL in vivo inhibited EAC growth and augmented NO2(-) release by TAMs. PRL synergized with the TH1 cytokine IFN-gamma, a known activator of macrophages, in inducing tumor killing and release of NO2(-) from EMs and TAMs. The hormone might activate macrophages at least partially, through the release of IFN-gamma as anti-IFN-gamma blocked IFN-gamma- as well as PRL-induced cytotoxicity in EMs. The TH2 cytokine IL-4 suppressed PRL-induced activation of macrophages. PRL induced release of IL-12 from EMs also, which suggested that the hormone might drive the TH1 response through IL-12. Our observations further suggest that PRL alone and in synergy with IFN-gamma, released through induction of IL-12, may generate tumoricidal macrophages and thus regulate the antitumor immune response of tumor hosts.

Adjuvants, Immunologic↗
PubMed1984

Procoagulant activity of macrophages associated with different murine neoplasms.

Mononuclear phagocytes, an integral part of the lymphoreticular infiltrate of human and experimental tumors, might contribute to tumor-associated fibrin deposition through the development of procoagulant activity (PCA). We have investigated PCA of tumor-associated macrophages (TAM) in 6 transplanted murine tumors in syngeneic hosts; peritoneal macrophages from tumor-bearing and control animals were studied also, as reference cell populations. PCA was evaluated by a one-stage clotting assay immediately after preparation and following incubation in the absence and in the presence of endotoxin. TAM from 5 poorly immunogenic tumors (mFS6, MN/MCA1, R 80/44, M109 and MS2) had basal PCA levels comparable to or somewhat lower than those of peritoneal macrophages from the same animals. Similar PCA was found in peritoneal macrophages from both control and tumor-bearing animals. Unlike peritoneal macrophages, TAM in all instances failed to respond with increased PCA when exposed to endotoxin in vitro. Failure to respond to endotoxin could not be ascribed to contaminating tumor cells or their products, to the presence of suppressive macrophage populations or to the lack of lymphocyte "help". TAM from a strongly immunogenic, regressing tumor (MSV sarcoma), in contrast to its non-immunogenic variant, MS2, and to the 4 other tumors mentioned above, expressed high levels of PCA immediately after isolation. The latter did not increase further following in vitro stimulation with endotoxin. When MSV sarcomas were induced in nude mice, TAM showed PCA levels similar to those of the euthymic hosts, suggesting that the procoagulant response was largely independent of T-cell-mediated immunity.

Animals↗
PubMed1999

Urokinase plasminogen activator receptor (CD87) expression of tumor-associated macrophages in ductal carcinoma in situ, breast cancer, and resident macrophages of normal breast tissue.

UNLABELLED: Macrophages concentrate urokinase-type plasminogen activator (uPA) at the cell surface by expressing urokinase receptors (uPAR) in order to focus the pericellular space plasminogen-dependent proteolysis important in matrix remodeling and cell movement. This study examines the uPAR levels of tumor-associated macrophages (TAM) of invasive breast carcinomas, of TAMs from ductal carcinoma in situ (DCIS) and of macrophages derived from normal (non-tumor) breast tissue. TAMs from invasive breast carcinomas (n = 30), from DCIS (n = 12), and macrophages from normal breast tissue (n = 30) were cultured and immunocytochemically phenotyped by using a panel of antibodies. Urokinase receptor levels were determined by Western blot analysis and in cell-free supernatants by enzyme-linked immunosorbent assay. Urokinase receptor cell surface fluorescence intensity was determined by FACS and by confocal laser scan microscopy. Urokinase-receptor mRNA was detected by in situ hybridization. TAMs of invasive breast carcinomas and of DCIS possess significantly elevated uPAR levels compared with macrophages derived from normal breast tissue. CONCLUSIONS: activated macrophages with elevated uPAR levels belong to inflammatory areas in close vicinity of infiltrating and non-infiltrating (DCIS) tumor cells. Blood monocytes that possess elevated uPAR-levels may be selectively recruited from the bloodstream to inflammatory sites close to carcinoma cells, and/or breast cancer and precursor lesions may induce elevated uPAR-levels in TAMs by paracrine interactions.

Breast Neoplasms↗
PubMed1996

Macrophages and apoptotic cells in human colorectal tumours.

The numerical relationship between tumour associated macrophages (TAM) and apoptotic cells in 12 human colorectal tumours was evaluated. TAM were labelled immunohistochemically and apoptotic cells were visualized by counterstaining with haematoxylin and eosin (H&E). The stereological techniques, Cavalieri's estimator of volume and the Disector were used to estimate both tumour volume and numerical density of both cell types. The occurrence of TAM per unit volume of tissue increased with increasing tumour volume to a maximum in a tumour of 110.5 cm3, after which numbers declined. Levels of apoptosis also increased with tumour volume though more erratically than levels of TAM and declined for tumour volumes greater than 80 cm3. This is the first report of an attempt to assess the relationship between apoptotic cells and TAM in human tumours.

Apoptosis↗
PubMed1993

Uterine malignant mixed müllerian tumor in a patient on long-term tamoxifen therapy for breast cancer.

A case of malignant mixed müllerian tumor of the uterus, heterologous type, in an 83-year-old woman on tamoxifen (TAM) therapy for 9 years for breast cancer is presented. Benign endometrial polyps were diagnosed on endometrial curettings for postmenopausal bleeding after the patient had been on TAM for 5 years. Recurrent postmenopausal bleeding developed 4 years later. Endometrial curettings and hysterectomy revealed a 10-cm polypoid malignant mixed müllerian tumor (MMMT) and endometrial polyps. There was no invasion of the myometrium or endocervix and no evidence of metastatic tumor in 13 pelvic lymph nodes, peritoneal washings, or omentum. TAM has been associated with the development of endometrial polyps, hyperplasia, and adenocarcinoma possibly mediated through its agonistic estrogenic properties. Only one other case of MMMT arising in patients on TAM therapy has been previously reported, but may also be a consequence of the estrogenic effects of TAM therapy.

Aged↗
PubMed1985

Autologous tumor killing and natural cytotoxic activity of tumor-associated macrophages in cancer patients.

Tumor-associated macrophages (TAM) isolated from pleural effusions and ascites fluids of cancer patients were tested for cytotoxicity against freshly isolated autologous tumor cells and K562 in a 4-h 51Cr-release assay, and in vitro effects of OK432 (a streptococcal preparation) and partially purified human leukocyte interferon (IFN) on their cytotoxicities were examined. Positive cytotoxicities against K562 were recorded for TAM samples from 2 of 23 pleural effusions and 3 of 10 ascites specimens. Tumor-associated macrophages were not cytotoxic to autologous tumor cells, while low but significant lysis was observed with tumor-associated lymphocytes (TAL) samples from 2 of 13 pleural effusions and 1 of 6 ascites specimens. In vitro treatment with OK432 resulted in an enhancement of natural cytotoxicity in 4 of 13 TAM and 10 of 15 TAL samples. An induction or augmentation of autologous tumor killing activity by OK432 was observed in 2 of 10 TAM and 8 of 11 TAL samples. In contrast, IFN failed to induce autologous tumor killing activity, although IFN-enhanced lysis of K562 was detected in 1 of 7 TAM and 2 of 9 TAL samples. These results indicated that autologous tumor killing and natural cytotoxic activities were defective in macrophages and lymphocytes at the site of the tumor growth, and both activities were strongly enhanced by OK432 rather than IFN.

Antibodies, Monoclonal↗
PubMed1994

4-Hydroxytamoxifen, an active metabolite of tamoxifen, does not alter the radiation sensitivity of MCF-7 breast carcinoma cells irradiated in vitro.

The effect of 4-hydroxytamoxifen (4OH-TAM), the potent anti-estrogenic metabolite of tamoxifen, on the radiosensitivity of MCF-7 cells irradiated in vitro was determined. Radiation dose response curves were generated for MCF-7 cells maintained and irradiated in phenol red-free medium containing 10(-10) M estradiol (E2) with or without 10(-7) M 4OH-TAM. Immediately after irradiation cells were transferred to medium containing 10(-10) ME2 supplemented with bovine serum to stimulate colony formation. Estradiol-stimulated cell proliferation was inhibited by 10(-7) M 4OH-TAM, but radiation sensitivity was not significantly altered (p > 0.3). Continued incubation in the absence of E2 for an additional 24 hours after irradiation likewise failed to alter the radiosensitivity of 4OH-TAM-treated MCF-7 cells. These studies indicate that growth-inhibitory concentrations of the anti-estrogen 4OH-TAM do not modify the in vitro radiation sensitivity of this line of human breast carcinoma cells.

Breast Neoplasms↗
PubMed1995

Effect of tamoxifen on mitoxantrone cytotoxicity in drug-sensitive and multidrug-resistant MCF-7 cells.

The influence of the antiestrogen tamoxifen (TAM) on the activity of mitoxantrone (MXN), was evaluated against wild-type MCF-7/WT and their multidrug-resistant variant MCF-7/ADR cells. Multidrug resistance (MDR) in this cell line which was selected for resistance to Adriamycin (ADR), is associated with increased expression of P-glycoprotein (P-gp). In a clonogenic assay it was observed that TAM (1-10 microM) significantly enhanced the activity of MXN in the MCF-7/ADR but not in the drug-sensitive cell line. Isobologram analysis indicated that the effect of the combination was additive in the parental MCF-7/WT cells and strongly synergistic in the MDR MCF-7/ADR cells. Also, TAM (10 microM) caused a three-fold increase in the steady-state levels (Css) of MXN in MCF-7/ADR cells but did not modulate MXN levels in MCF-7/WT cells. The observed synergism in MCF-7/ADR cells was perhaps due to the increase in Css of MXN that may involve interaction of TAM with P-gp. The combination of MXN and TAM may be useful in the treatment of drug-sensitive and drug-resistant breast cancer.

Breast Neoplasms↗
PubMedDate not supplied

Modulation of human breast cancer cell adhesion by estrogens and antiestrogens.

In order to study the effect of estrogens and antiestrogens on the adhesive properties of human breast cancer cells, the attachment on endothelial cells (EC), on subendothelial extracellular matrix (ECM) and on ECM components (collagen I and IV, laminin, fibronectin) of estrogen-dependent (MCF-7, ZR75-1) and estrogen-independent (BT-20) breast cancer cell lines was investigated. The cells were grown under conditions of controlled exposure to estrogen [17 beta-estradiol (E2)] and/or antiestrogens [tamoxifen (Tam) or 4-hydroxytamoxifen (OH-Tam)]. Treatment by E2 enhanced the ability of ZR75-1 cells to adhere to the various substrates, which contrasts with the observed absence of effects with the BT-20 cells. Similarly, Tam or OH-Tam induced a reduction of the adhesion of ZR75-1 tumor cell, but not of BT-20 cells. This effect was reversed by competing concentrations of E2. The effects on MCF-7 cell adhesion were similar to those described for ZR75-1 cells, but could not be reproducibly observed. Adhesion assays carried out with ZR75-1 cells grown in the absence or presence of phenol red, a pH indicator which behaves as a weak estrogen, led to a similar pattern of cell attachment. Conditioned media harvested from E2- or Tam-treated ZR75-1 cells failed to induce any effect on adhesion of other ZR75-1 cells grown in E2-deprived medium, suggesting that secretory activities are not required for the control of cell adhesiveness. The results suggest that estrogens and antiestrogens can control the adhesive behavior of breast tumor cells through their hormone responsive structures possibly by regulating expression of cell adhesion proteins and/or their cell surface receptors.

Breast Neoplasms↗