Emerging principles for the development of resistance to antihormonal therapy: Implications for the clinical utility of fulvestrant

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• 作者：Eric A. Ariazi ; Joan S. Lewis-Wambi ; Shaun D. Gill ; Jennifer R. Pyle ; Jennifer L. Ariazi ; Helen R. Kim ; Catherine G.N. Sharma ; Fern ; o Cordera ; Heather A. Shupp ; Tianyu Li ; et al.
• 关键词：Breast cancer ; Estradiol ; Tamoxifen ; Raloxifene ; Fulvestrant
• 刊名：The Journal of Steroid Biochemistry and Molecular Biology
• 出版年：2006
• 出版时间：December 2006
• 年：2006
• 卷：102
• 期：1-5
• 页码：128-138
• 全文大小：700 K

文摘

We seek to evaluate the clinical consequences of resistance to antihormonal therapy by studying analogous animal xenograft models. Two approaches were taken: (1) MCF-7 tumors were serially transplanted into selective estrogen receptor modulator (SERM)-treated immunocompromised mice to mimic 5 years of SERM treatment. The studies in vivo were designed to replicate the development of acquired resistance to SERMs over years of clinical exposure. (2) MCF-7 cells were cultured long-term under SERM-treated or estrogen withdrawn conditions (to mimic aromatase inhibitors), and then injected into mice to generate endocrine-resistant xenografts. These tumor models have allowed us to define Phase I and Phase II antihormonal resistance according to their responses to E₂ and fulvestrant. Phase I SERM-resistant tumors were growth stimulated in response to estradiol (E₂), but paradoxically, Phase II SERM and estrogen withdrawn-resistant tumors were growth inhibited by E₂. Fulvestrant did not support growth of Phases I and II SERM-resistant tumors, but did allow growth of Phase II estrogen withdrawn-resistant tumors. Importantly, fulvestrant plus E₂ in Phase II antihormone-resistant tumors reversed the E₂-induced inhibition and instead resulted in growth stimulation. These data have important clinical implications. Based on these and prior laboratory findings, we propose a clinical strategy for optimal third-line therapy: patients who have responded to and then failed at least two antihormonal treatments may respond favorably to short-term low-dose estrogen due to E₂-induced apoptosis, followed by treatment with fulvestrant plus an aromatase inhibitor to maintain low tumor burden and avoid a negative interaction between physiologic E₂ and fulvestrant.