Dataset Information

Endoxifen Downregulates AKT Phosphorylation Through Protein Kinase C Beta 1 in ER+/HER2- Breast Cancer

ABSTRACT: In phase I/II clinical trials, Z-endoxifen demonstrated substantial oral bioavailability and promising antitumor activity in endocrine-refractory estrogen-receptor positive breast cancer (ER+ BC) and other solid tumors, with plasma concentrations reportedly as high as 5 ï�M. Therefore, we explored the potential mechanisms of Z-endoxifen antitumor activity that extends beyond ERÎ± inhibition. In estrogen unstimulated aromatase-expressing ER+/human epidermal growth factor 2 receptor negative (HER2-) MCF7AC1 BC cells, Z-endoxifen at 5 ï�M, but not ERï�¡-targeting 0.01 and 0.1 ï�M concentrations inhibited growth and induced apoptosis, suggesting an ERÎ±-independent effect. Utilizing an unbiased mass spectrometry approach, we explored Z-endoxifen effects on other signaling pathways. Z-endoxifen at 5 ÂµM profoundly altered the phosphoproteome with minimal impact on total proteome. Computational analysis revealed Protein kinase C beta (PKCï�¢) and AKT1 as the prevalent upstream kinases for Z-endoxifen-downregulated protein phosphorylations. Notably, in ER+/HER2- BC models, Z-endoxifen at 5 ï�M attenuated AKTSer473 and AKT substrates in vitro in the presence of insulin and PKC agonist PMA and in vivo. Further, Z-endoxifen inhibited PKCï�¢1 kinase activity compared to other PKC isoforms in vitro and bound to PKCÎ²1. While PMA stimulated PKCï�¢1Ser661 phosphorylation correlated with AKTSer473 and AKT substrate phosphorylation, Z-endoxifen at 5 ï�M uniquely blocked these effects and induced PKCÎ²1 protein degradation. siRNA-mediated PKCï�¢1 knockdown attenuated AKTSer473 phosphorylation, suggesting PKCÎ²1-mediated suppression of AKT signaling by Z-endoxifen. Further, Z-endoxifen at 5 ï�M replicates the pan-AKT inhibitor MK-2206 effects on apoptosis. These findings implicate PKCÎ²1 as a novel Z-endoxifen substrate responsible for suppressing AKT signaling and inducing apoptosis in breast cancer.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Breast, Cell Culture

DISEASE(S): Breast Cancer

SUBMITTER: Akhilesh Pandey

LAB HEAD: Akhilesh Pandey

PROVIDER: PXD035007 | Pride | 2024-01-26

REPOSITORIES: Pride

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Dataset's files

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			Action	DRS
	XWU_MCF7_EDX_TMTPro_TP_041420_F01-24.mzML	Mzml
	XWU_MCF7_EDX_TMTPro_TP_041420_F01-24.mzid.gz	Mzid
	XWU_MCF7_EDX_TMTPro_TP_041420_F01-24.pdResult	Other
	XWU_MCF7_EDX_TMTPro_TP_041420_F01.raw	Raw
	XWU_MCF7_EDX_TMTPro_TP_041420_F02.raw	Raw

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Publications

Endoxifen downregulates AKT phosphorylation through protein kinase C beta 1 inhibition in ERα+ breast cancer.

Jayaraman Swaathi S Wu Xinyan X Kalari Krishna R KR Tang Xiaojia X Kuffel Mary J MJ Bruinsma Elizabeth S ES Jalali Shahrzad S Peterson Kevin L KL Correia Cristina C Kudgus Rachel A RA Kaufmann Scott H SH Renuse Santosh S Ingle James N JN Reid Joel M JM Ames Matthew M MM Fields Alan P AP Schellenberg Matthew J MJ Hawse John R JR Pandey Akhilesh A Goetz Matthew P MP

NPJ breast cancer 20231219 1

Endoxifen, a secondary tamoxifen metabolite, is a potent antiestrogen exhibiting estrogen receptor alpha (ERα) binding at nanomolar concentrations. Phase I/II clinical trials identified clinical activity of Z-endoxifen (ENDX), in endocrine-refractory metastatic breast cancer as well as ERα+ solid tumors, raising the possibility that ENDX may have a second, ERα-independent, mechanism of action. An unbiased mass spectrometry approach revealed that ENDX concentrations achieved clinically with direc ...[more]

PMID: 38114522

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