thromboxane-a2 and Breast-Neoplasms

Clinical evidence recently suggests that the regular use of aspirin is associated with a lower risk of breast cancer metastasis, but mechanisms remain unclear. Resistance to anoikis has been implicated in malignant transformation and metastasis. Here, we investigated whether aspirin might prevent breast cancer metastasis to lung by targeting anoikis resistance. Aspirin sensitized breast cancer cells to anoikis in vitro and lowered the circulating tumor cells as well as distant metastasis in vivo. Mechanistically, thromboxane A2 (TXA2) pathway was identified as the relevant molecular target for aspirin in anoikis sensitization. Upon detachment, both thromboxane A2 receptor (TP) and thromboxane A2 synthase 1 (TBXAS1) were up-regulated in metastatic breast cancer cells, conferred anoikis resistance through persistent activation of Akt, thereby facilitated breast cancer metastasis to lung. Consistently, either knockdown of TP in cancer cells or genetic deletion of TP in mice protected against lung metastasis in vivo. Collectively, TXA2 pathway plays a critical role in anoikis resistance and might serve as potential target for chemoprevention of breast cancer metastasis.

Topics: Animals; Anoikis; Aspirin; Breast Neoplasms; Cell Line, Tumor; Female; Humans; Lung; Lung Neoplasms; Mice; Neoplasm Metastasis; Neoplasms, Second Primary; Signal Transduction; Thromboxane A2

Tumor cell-induced platelet aggregation represents a critical process both for successful metastatic spread of the tumor and for the development of thrombotic complications in cancer patients. To get further insights into this process, we investigated and compared the molecular mechanisms of platelet aggregation induced by two different breast cancer cell lines (MDA-MB-231 and MCF7) and a colorectal cancer cell line (Caco-2). All the three types of cancer cells were able to induce comparable platelet aggregation, which, however, was observed exclusively in the presence of CaCl

Topics: Amino Acid Chloromethyl Ketones; Aspirin; Blood Platelets; Breast Neoplasms; Caco-2 Cells; Calcium Chloride; Colorectal Neoplasms; Female; Fibrin; Fibrinogen; Humans; Integrin alpha2; MCF-7 Cells; Platelet Activation; Platelet Aggregation; Thromboxane A2; Type C Phospholipases

An association between platelets, angiogenesis, and cancer has long been recognized, but the mechanisms linking them remains unclear. Platelets regulate new blood vessel growth through numerous stimulators and inhibitors of angiogenesis by several pathways, including differential exocytosis of angiogenesis regulators. Herein, we investigated the differential release of angiogenesis stimulators and inhibitors from platelets. Activation of human platelets with adenosine diphosphate (ADP) stimulated the release of VEGF, but not endostatin whereas, thromboxane A(2) (TXA(2)) released endostatin but not VEGF. Platelet releasates generated by activation with ADP promoted migration and formation of capillary structures by human umbilical vein endothelial cells (HUV-EC-Cs) in in vitro angiogenesis models. Conversely, TXA(2)-stimulated platelet releasate inhibited migration and formation of capillary structures. Because tumor growth beyond 1-2 mm(3) is angiogenesis-dependent, we hypothesized that cancer cells preferentially stimulate platelets to secrete their pro-angiogenic payload. In support of this, the breast cancer cell line MCF-7 stimulated secretion of VEGF and a pro-angiogenic releasate from platelets. Furthermore, the antiplatelet agent aspirin inhibited platelet-mediated angiogenesis after exposure to ADP or MCF-7 cells providing a potential mechanism for how aspirin may impact malignancy. Manipulation of differentially mediated release of angiogenic factors from platelets may provide a new modality for cancer treatment.

Topics: Adenosine Diphosphate; Angiogenesis Modulating Agents; Aspirin; Blood Platelets; Breast Neoplasms; Carcinoma; Cells, Cultured; Endostatins; Endothelial Cells; Female; Humans; Models, Biological; Neovascularization, Pathologic; Neovascularization, Physiologic; Secretory Vesicles; Thromboxane A2; Vascular Endothelial Growth Factor A

To explore the mechanism(s) by which antiestrogens may protect against the development of cardiovascular disorders, we measured the production of vasodilatory, antiaggregatory prostacyclin (PGI2) and that of vasoconstrictive, proaggregatory thromboxane A2 (TxA2) before and after 6 months' use of antiestrogens in postmenopausal patients after operation for stage II breast cancer (n = 38). Urine samples were assayed by high performance liquid chromatography and radio-immunoassays for 2,3-dinor-6-ketoprostaglandin F1 alpha (= metabolite of PGI2, dinor-6-keto) and for 2,3-dinor-thromboxane B2 (= metabolite of TxA2, dinor-TxB2). In addition, in 35 of these 38 patients we assayed the capacity of platelets to produce thromboxane A2 during standardized blood clotting. The 4 patients using low-dose aspirin had low thromboxane production, and were excluded from further analysis of the data. An antiestrogen regimen consisting either of tamoxifen (n = 15) or of toremifene (n = 19) caused no changes in production of PGI2 or TxA2, or in their ratio, and in this regard, these antiestrogens behaved similarly. Hypertensive patients (n = 7) using different anti-hypertensive agents were characterized by reduced urinary out-put of dinor-6-keto (18.5 +/- 6.1 vs 35.5 +/- 18.5 ng/mmol, mean +/- SD, p < 0.05) and reduced platelet capacity to produce TxA2 (62.6 +/- 67.8 vs 134.6 +/- 75.6 ng/mL, p < 0.05). The patients (n = 15) who had used estrogen replacement therapy (ERT) up until diagnosis of breast cancer showed reduced dinor-TxB2 excretion (15.5 +/- 12.7 vs 29.9 +/- 20.9 ng/mmol, p < 0.05) before initiation of antiestrogens, and elevated dinor-6-keto output during the antiestrogen regimen (32.4 +/- 21.2 vs 22.7 +/- 8.7 ng/mmol, p = 0.07). Smokers (n = 6) had elevated dinor-TxB2 output before and during antiestrogen use. Thus we conclude that the cardiovascular protection provided by an antiestrogen regimen is unlikely to be mediated through vaso- and platelet active PGI2 and TxA2.

Topics: Aged; Breast Neoplasms; Epoprostenol; Estrogen Antagonists; Estrogens; Female; Humans; Hypertension; Menopause; Middle Aged; Molecular Structure; Smoking; Tamoxifen; Thromboxane A2; Toremifene

Topics: Breast Neoplasms; Humans; Neoplasm Metastasis; Thromboxane A2; Thromboxane-A Synthase

Topics: Breast Neoplasms; Dinoprost; Dinoprostone; Epoprostenol; Female; Humans; Prognosis; Prostaglandins E; Prostaglandins F; Thromboxane A2

To study the production and significance of prostacyclin (PGI2) and thromboxane A2 (TxA2) in breast cancer, tissue fragments of breast cancer (n=23) and mastopathy (n=10) were superfused in vitro and the release of 6-keto-PGF1 alpha (a metabolite of PG12) and TxB2 (a metabolite of TxA2) measured by radioimmunoassay. Breast cancer formed more 6-keto-PGF1 alpha (4.5 +/- 0.9 ng min-1 g-1 of tissue dry weight, mean +/- s.e.) and TxB2 (2.5 +/- 0.6 ng min-1 g-1) (P less than 0.01) than did mastopathic breast (1.4 +/- 0.5 and 0.4 +/- 0.1 ng min-1 g-1, respectively). These productions were similar in steroid receptor positive and negative tumours. Breast cancer metastasized in 15 patients during the follow-up time of 3.7 +/- 0.7 years, but the initial prostanoid productions in these patients were not different from those in nonmetastatic patients. Two patients died from metastases, but their initial mammary production of prostanoids was not profoundly different from those in the survivors. In 8 patients (4 with steroid receptor positive and 4 with negative tumour), the cancer tissue was superfused in the presence or absence of medroxyprogesterone acetate (100-5000 ng ml-1), which is commonly used for treatment of breast cancer. This hormone had no effect on mammary PGI2 and TxA2 production. We thus conclude that the PGI2 and TxA2 productions are increased in mammary cancer but that this may not be of primary significance for metastastic spread.

Topics: 6-Ketoprostaglandin F1 alpha; Aged; Antineoplastic Agents; Breast Diseases; Breast Neoplasms; Carcinoma, Intraductal, Noninfiltrating; Epoprostenol; Female; Humans; In Vitro Techniques; Medroxyprogesterone; Medroxyprogesterone Acetate; Middle Aged; Receptors, Steroid; Thromboxane A2; Thromboxane B2; Thromboxanes

The production of PGI2 (determined by bioassay) and TXB2 (determined by radioimmunoassay) was studied in the supernatant solutions obtained after incubation of vessel rings prepared from veins draining and not draining benign and malignant tumours of the breast. A significant increase (p less than 0.01) was found in the production of PGI2 by vessels draining the malignant tumours as compared to those not draining such tumours or vessels draining benign tumours. The changes in PGI2, and the tendency for TXB2 to be higher in vessels draining malignant tumours, were in the same direction so that they balanced out when the ratio PGI2/TXB2 was calculated: in consequence no significant changes in this ratio were found in malignant tumours as compared to the benign. A significant difference (p less than 0.01) was observed in the ratios of vessels draining tumours:vessels not draining tumours between malignant and benign tumours in relation to the production of PGI2. The present data demonstrate that the production of PGI2 by vessels draining malignant tumours of the breast is different to that obtained with vessels from patients with benign tumours, although the mechanism responsible for this difference is not known.

Topics: Adult; Aged; Breast Neoplasms; Epoprostenol; Female; Humans; Middle Aged; Radioimmunoassay; Thromboxane A2; Thromboxanes; Veins