dehydrothyrsiferol and Breast-Neoplasms

The fact that disruption of integrin-extracellular matrix contacts leads to cell death, has converted cell adhesion into a potential target for the control of invasive cancer. In this work, we studied the functional consequences of the interference with the activity of the very late activation antigen (VLA) family of integrins in human breast cancer cell lines of distinct malignancy. The alpha2beta1-mediated adhesion reduced the entry of highly malignant, hormone-independent breast cancer cells into apoptosis. Adhesion of breast cancer cells through the VLA integrins alpha2beta1 and alpha5beta1 was significantly reduced by an apoptosis-inducing natural triterpenoid, dehydrothyrsiferol (DT), when studied on low amounts of extracellular matrix. This effect was dose-dependent, not related to cell toxicity and not shared with apoptosis-inducing standard chemotherapeutics, such as doxorubicin and taxol. The compound did not affect either the cell surface expression level of VLA integrins or cell distribution of vinculin and actin during cell spreading. In addition, neither phosphorylation of the focal adhesion kinase pp125FAK on Tyr397 nor the protein kinase B (Akt/PKB) on Ser473 was significantly altered by DT. The integrin activation level, assessed by binding of soluble collagen to the alpha2beta1 integrin, was reduced upon cell treatment with DT. Importantly, the TS2/16, an anti-beta1 activating monoclonal antibody was able to rescue DT-treated cells from apoptosis. Since the activation state of integrins is increasingly recognized as an essential factor in metastasis formation, findings presented herein reveal that the chemical regulation of integrin affinity may be a potential therapeutic strategy in cancer therapy.

Topics: Actins; Apoptosis; Breast Neoplasms; Cell Adhesion; Cell Line, Tumor; Extracellular Matrix; Focal Adhesion Kinase 1; Humans; Integrin alpha2beta1; Integrin alpha5beta1; Integrins; Phosphorylation; Proto-Oncogene Proteins c-akt; Pyrans; Receptors, Very Late Antigen; Vinculin

Breast cancer (BCA) represents the highest incidence of death in 35- to 60-year-old women. Above all, hormone unresponsive BCA is still associated with poorer prognosis than hormone receptor expressing malign, mammary tumors. There is a consistent need for effective compounds to treat especially the first variant of this disease. Therefore, we investigated the cytotoxic effects of the marine polyether triterpenoid dehydrothyrsiferol (DT) in four BCA cell lines. Annexin V labeling revealed higher rates of DT-induced apoptosis in hormone insensitive than in estrogen receptor expressing cells. Flow cytometric analysis of combined DNA fragmentation and total DNA labeling allowed us to ascribe apoptotic cells to their cell cycle stage. Although, high cell mortality was detected in mitogen dependent G(1)-phase, time, concentration, and cell line dependent populations of apoptotic cells were also found to be of S-phase and G(2)/M-phase origin. These results suggest that the induction of apoptosis by DT might be transduced through more than one effector pathway. Cell cycle distributions and 5-bromo-2'-deoxyuridine incorporation varied in a treatment dependent manner and differed from control experiments with colchicine and doxorubicin which exclude that DT functions as a mitosis inhibitor. In summary, we propose that DT might be an interesting candidate for an antitumor drug development regimen.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Bromodeoxyuridine; Camptothecin; Cell Cycle; Cell Division; Colchicine; DNA; Doxorubicin; Estrogens; Humans; Phosphatidylserines; Pyrans; Tumor Cells, Cultured

The novel marine terpenoid dehydrothyrsiferol (DHT) has been isolated from a Canarian red alga Laurencia viridis sp. nov (Ceramiales, Rhodomelaceae) (1). Its cytotoxicity against three human breast cancer cell lines, namely T47D, ZR-75-1, and Hs578T was examined and compared with the chemotherapeutic compound doxorubicin and the mitosis-inhibitor colchicine. Primary breast carcinomas exhibit MDR1 gene expression (3). As the investigated mammary cell lines did not exhibit rhodamine 123 efflux we proved in a P-glycoprotein (Pgp) overexpressing human epidermoid cancer cell line that the marine metabolite does not modulate Pgp mediated drug transport. Therefore, it could be used in Pgp expressing cancer cells without interference.

Topics: Antineoplastic Agents, Phytogenic; ATP Binding Cassette Transporter, Subfamily B; Biological Transport; Breast Neoplasms; Cell Division; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Eukaryota; Fluorescent Dyes; Humans; KB Cells; Marine Biology; Pyrans; Rhodamine 123; Tumor Cells, Cultured