Paradoxical Hormone Responses of KPL-1 Breast Cancer Cells in vivo: A Significant Role of Angiogenesis in Tumor Growth

Abstract

In our previous study, the growth of KPL-1 human breast cancer cells was found to be stimulated by an antiestrogen, ICI 182, 780, and inhibited by 17 β-estradiol (E2) in vivo but not in vitro. To investigate the action mechanisms of these paradoxical responses, the effects of E2, ovariectomy (Ovex) and medroxyprogesterone acetate (MPA) on the growth, angiogenesis, apoptosis and expression of vascular endothelial growth factor (VEGF) were investigated. E2 stimulated the growth of KPL-1 cells but MPA inhibited it in vitro. In contrast, E2 propionate inhibited the growth of KPL-1 cells in female nude mice but Ovex and MPA stimulated it. E2 propionate suppressed angiogenesis and increased apoptosis in KPL-1 tumors, but Ovex and MPA promoted angiogenesis and decreased apoptosis. Both mRNA expression and secretion of VEGF were stimulated by MPA in KPL-1 cells, but in E2-dependent ML-20 cells they were both inhibited by MPA. E2 did not significantly influence VEGF expression in either cell line. These findings suggest that the abnormal modulation of VEGF expression by MPA and of the other angiogenic factor by E2 are responsible for the paradoxical growth responses of KPL-1 cells in vivo. To support this hypothesis, an antiangiogenic agent, TNP-470, was administered to mice bearing KPL-1 tumors. TNP-470 significantly inhibited the growth of KPL-1 tumors stimulated by MPA. Antiangiogenic agents may be effective for the treatment of hormone-refractory breast cancer.

Additive antitumour effect of the epidermal growth factor receptor tyrosine kinase inhibitor gefitinib (Iressa, ZD1839) and the antioestrogen fulvestrant (Faslodex, ICI 182,780) in breast cancer cells

“…KPL-1 cells are derived from a postmenopausal patient with hormone-refractory breast cancer. This cell line is ERa-positive and oestrogen responsive in vitro but not in vivo (Kurebayashi et al, 2000a). KPL-3C cells are derived from a premenopausal patient with breast cancer associated with humoral hypercalcemia.…”

“…KPL-1 and KPL-3C cells expressed a high level of ER and undetectable PgR in the oestrogen-deprived condition (but PgR is inducible by an E2 supplementation) (Kurebayashi et al, 1996;Kurebayashi et al, 2000a). T47D cells expressed a low level of ER associated with a very high level of PgR in the oestrogen-deprived condition.…”

Hypoxia Reduces Hormone Responsiveness of Human Breast Cancer Cells

“…In vitro experiments To reduce endogenous estrogenic activity, phenol red-free RPMI-1640 medium (Gibco BRL, Bethesda, MD) supplemented with 5% dextran-coated charcoal-stripped fetal bovine serum (FBS) (Hyclone, UT) (estrogen-deprived medium) was used for in vitro experiments. 5) Because half of solid tumors have median oxygen concentrations less than 10 mmHg (approximately 1% O 2 ) 12) and a putative key factor of cellular hypoxic reaction, HIF-1α, is easily induced by a hypoxic condition of 1% O 2 , 6) 1% O 2 was chosen as a hypoxic condition in the present study. Approximately 2×10 5 KPL-1 or ML-20 cells/well were inoculated into 12-well plates (Costar Corning, Inc., Corning, NY) and cultured in Dulbecco's modified essential medium supplemented with 5% FBS for 2 days.…”

A Radicicol Derivative, KF58333, Inhibits Expression of Hypoxia‐inducible Factor‐1α and Vascular Endothelial Growth Factor, Angiogenesis and Growth of Human Breast Cancer Xenografts

“…24) The number of dots inside the structures per field (approximately 0.43 mm 2 ) was counted using a transparent plastic grid to evaluate the vascular area of each tumor sample. 25) DNA breaks were detected by nick end labeling using an ApopTag in situ apoptosis detection kit (Oncor, Inc., Gaithersburg, MD) as described elsewhere.…”

“…VEGF secretion The VEGF concentrations in the culture medium were measured with an enzyme-linked immunosorbent assay kit (Otsuka Assay Laboratory, Tokushima). 25) Briefly, a mouse anti-human VEGF monoclonal antibody was used as the first antibody and a rabbit antihuman VEGF polyclonal antibody labeled with alkaline phosphatase as the second antibody. After removal of the unbound second antibody, horseradish peroxidase solution was added.…”