RESUMEN
Tamoxifen resistance has been largely attributed to genetic alterations in the epithelial tumor cells themselves, such as overexpression of HER-2/Neu. However, in the clinic, only about 15-20% of cases of HER-2/Neu amplification has actually been correlated to the acquisition of endocrine resistance, suggesting that other mechanisms must be involved as well. Using the epithelial LM05-E and the fibroblastic LM05-F cell lines, derived from the estrogen dependent spontaneous M05 mouse mammary tumor, as well as MCF-7 cells, we analyzed whether soluble stromal factors or extracellular matrix components protected against tamoxifen induced cell death. Involvement of signaling pathways was determined by using specific inhibitors and western blot, and phosphorylation of the estrogen receptor alpha by western blot and immunofluorescence. Soluble factors produced by the fibroblastic cells protect the epithelial tumor cells from tamoxifen-induced cell death through a mechanism that involves EGFR and matrix metalloproteinases upstream of PI3K/AKT. Exogenous fibronectin by itself confers endocrine resistance through interaction with ß1 integrin and activation of PI3K/AKT and MAPK/ERK 1/2 pathways. The conferred resistance is reversed by blocking ß1 integrin. We show also that treatment with both conditioned medium and fibronectin leads to the phosphorylation of the estrogen receptor at serine-118, suggesting stromal factors as modulators of ER activity. Our results show that the tumor microenvironment can modulate tamoxifen resistance, providing an alternative explanation for why patients become refractory to hormone-therapy.
Asunto(s)
Antineoplásicos Hormonales/farmacología , Neoplasias de la Mama/metabolismo , Fibronectinas/metabolismo , Integrina beta1/metabolismo , Tamoxifeno/farmacología , Microambiente Tumoral , Línea Celular Tumoral , Resistencia a Antineoplásicos , Células Epiteliales/metabolismo , Receptores ErbB/metabolismo , Receptor alfa de Estrógeno/metabolismo , Femenino , Fibroblastos/metabolismo , Humanos , Metaloproteinasas de la Matriz/metabolismo , Modelos Biológicos , Fosfatidilinositol 3-Quinasas/metabolismo , Fosforilación , Unión Proteica , Proteínas Proto-Oncogénicas c-akt/metabolismoRESUMEN
Several novel bioactive components isolated from Chinese medicinal plants will be presented. These include novel maytansinoid tumor, inhibitors, some new ent-kaurane and rosane diterpenoids from Mallotus anomalus Meer et Chun (Euphorbiaceae), as well asnovel insecticide, stemona alkaloids from Stemona parviflora C. H. Wright (Stemonaceae). Both are native plants of Hainan island, Chine. 2D NMR techniques such as mono and hetero-COSY, NOESY, COLOC as well as H-NMR line broadening effect were utilized for structure elucidation. The separation techniques, struture elucidations and bioassay results will be reported.