Design, Synthesis, and Mechanistic Investigations of Bile Acid鈥揟amoxifen Conjugates for Breast Cancer Therapy

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• 作者：Vedagopuram Sreekanth ; Sandhya Bansal ; Rajender K. Motiani ; Somanath Kundu ; Sravan Kumar Muppu ; Tapodhara Datta Majumdar ; Kuppusamy Panjamurthy ; Sagar Sengupta ; Avinash Bajaj
• 刊名：Bioconjugate Chemistry
• 出版年：2013
• 出版时间：September 18, 2013
• 年：2013
• 卷：24
• 期：9
• 页码：1468-1484
• 全文大小：806K
• 年卷期：v.24,no.9(September 18, 2013)
• ISSN：1520-4812

文摘

We have synthesized two series of bile acid tamoxifen conjugates using three bile acids lithocholic acid (LCA), deoxycholic acid (DCA), and cholic acid (CA). These bile acid鈥搕amoxifen conjugates possess 1, 2, and 3 tamoxifen molecules attached to hydroxyl groups of bile acids having free acid and amine functionalities at the tail region of bile acids. The in vitro anticancer activities of these bile acid鈥搕amoxifen conjugates show that the free amine headgroup based cholic acid鈥搕amoxifen conjugate (CA-Tam₃-Am) is the most potent anticancer conjugate as compared to the parent drug tamoxifen and other acid and amine headgroup based bile acid鈥搕amoxifen conjugates. The cholic acid鈥搕amoxifen conjugate (CA-Tam₃-Am) bearing three tamoxifen molecules shows enhanced anticancer activities in both estrogen receptor +ve and estrogen receptor 鈭抳e breast cancer cell lines. The enhanced anticancer activity of CA-Tam₃-Am is due to more favorable irreversible electrostatic interactions followed by intercalation of these conjugates in hydrophobic core of membrane lipids causing increase in membrane fluidity. Annexin-FITC based FACS analysis showed that cells undergo apoptosis, and cell cycle analysis showed the arrest of cells in sub G₀ phase. ROS assays showed a high amount of generation of ROS independent of ER status of the cell line indicating changes in mitochondrial membrane fluidity upon the uptake of the conjugate that further leads to the release of cytochrome c, a direct and indirect regulator of ROS. The mechanistic studies for apoptosis using PCR and western analysis showed apoptotsis by intrinsic and extrinsic pathways in ER +ve MCF-7 cells and by only an intrinsic pathway in ER 鈭抳e cells. In vivo studies in the 4T1 tumor model showed that CA-Tam₃-Am is more potent than tamoxifen. These studies showed that bile acids provide a new scaffold for high drug loading and that their anticancer activities strongly depend on charge and hydrophobicity of lipid鈥揹rug conjugates.