Delineating the molecular mechanisms of tamoxifen’s oncolytic actions in estrogen receptor-negative cancers
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- 作者：Daniel P. Radin<sup>asup><sup> ; sup><sup>danradin1@gmail.com" class="auth_mail" title="E-mail the corresponding authorsup> ; Parth Patel<sup>bsup><sup> ; sup><sup>parth.patel115@gmail.com" class="auth_mail" title="E-mail the corresponding authorsup>
- 关键词：Apoptosis ; Calcium influx ; JNK1 ; Oxidative stress ; Protein kinase C ; Tamoxifen
- 刊名：European Journal of Pharmacology
- 出版年：2016
- 出版时间：15 June 2016
- 年：2016
- 卷：781
- 期：Complete
- 页码：173-180
- 全文大小：567 K
文摘
Since its clinical inception, tamoxifen (TAM) has proved to be a powerful tool in treating estrogen receptor-positive breast cancers while exhibiting manageable side effects. Although TAM was synthesized as an estrogen receptor antagonist, reports have found that a significant fraction of women with estrogen receptor-negative cancers have benefitted from TAM treatment, suggesting the possibility of an alternate anti-cancer mechanism. In this paper, we present a review of recent and past literature in an attempt to clarify how TAM inhibits cell proliferation and induces apoptosis in cells lacking the estrogen receptor. Our analysis indicates that micromolar concentrations of TAM selectively elevate intracellular calcium concentrations in malignant cells, possibly by inversely agonizing cannabinoid receptors, producing considerable mitochondrial distress followed by the rapid production of reactive oxygen species. In response, cytoplasmic proteins such as JNK1 are activated, which mediates the activation of caspase-8. Fyn kinase auto phosphorylates in response to increased reactive oxygen species and directs the ubiquitin ligase c-Cbl to tag growth factor receptors for ubiquitination, potentially abrogating constitutively active survival pathways that are hallmarks of cancer progression. We attempt to differentiate the effect that TAM has on purified Protein Kinase C (PKC) compared to that in an intact cell, suggesting that low micromolar concentrations of TAM indirectly inhibit PKC by inducing EGFR destruction and high micromolar concentrations of TAM inhibits PKC through a direct binding mechanism.