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Association of tamoxifen resistance and lipid reprogramming in breast cancer.

ABSTRACT: BACKGROUND:Tamoxifen treatment of estrogen receptor (ER)-positive breast cancer reduces mortality by 31%. However, over half of advanced ER-positive breast cancers are intrinsically resistant to tamoxifen and about 40% will acquire the resistance during the treatment. METHODS:In order to explore mechanisms underlying endocrine therapy resistance in breast cancer and to identify new therapeutic opportunities, we created tamoxifen-resistant breast cancer cell lines that represent the luminal A or the luminal B. Gene expression patterns revealed by RNA-sequencing in seven tamoxifen-resistant variants were compared with their isogenic parental cells. We further examined those transcriptomic alterations in a publicly available patient cohort. RESULTS:We show that tamoxifen resistance cannot simply be explained by altered expression of individual genes, common mechanism across all resistant variants, or the appearance of new fusion genes. Instead, the resistant cell lines shared altered gene expression patterns associated with cell cycle, protein modification and metabolism, especially with the cholesterol pathway. In the tamoxifen-resistant T-47D cell variants we observed a striking increase of neutral lipids in lipid droplets as well as an accumulation of free cholesterol in the lysosomes. Tamoxifen-resistant cells were also less prone to lysosomal membrane permeabilization (LMP) and not vulnerable to compounds targeting the lipid metabolism. However, the cells were sensitive to disulfiram, LCS-1, and dasatinib. CONCLUSION:Altogether, our findings highlight a major role of LMP prevention in tamoxifen resistance, and suggest novel drug vulnerabilities associated with this phenotype.

SUBMITTER: Hultsch S

PROVIDER: S-EPMC6109356 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Association of tamoxifen resistance and lipid reprogramming in breast cancer.

Hultsch Susanne S Kankainen Matti M Paavolainen Lassi L Kovanen Ruusu-Maaria RM Ikonen Elina E Kangaspeska Sara S Pietiäinen Vilja V Kallioniemi Olli O

BMC cancer 20180824 1

<h4>Background</h4>Tamoxifen treatment of estrogen receptor (ER)-positive breast cancer reduces mortality by 31%. However, over half of advanced ER-positive breast cancers are intrinsically resistant to tamoxifen and about 40% will acquire the resistance during the treatment.<h4>Methods</h4>In order to explore mechanisms underlying endocrine therapy resistance in breast cancer and to identify new therapeutic opportunities, we created tamoxifen-resistant breast cancer cell lines that represent th ...[more]

PMID: 30143015

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Project description:Background: The amplification event occurring at chromosome locus 11q13, reported in several different cancers, includes a number of potential oncogenes. We have previously reported amplification of one such oncogene, CCND1, to be correlated with an adverse effect of tamoxifen in premenopausal breast cancer patients. Overexpression of cyclin D1 protein however, confers tamoxifen resistance but not a tamoxifen induced adverse effect. Potentially, co-amplification of an additional 11q13 gene, with a resulting protein overexpression, is required to cause an agonistic effect. Moreover, during 11q13 amplification a deletion of the distal 11q region has been described. In order to assess the potential impact of the deletion we have examined a selected marker for this event. Methods: Array CGH analysis was employed to identify and confirm changes in the gene expression of a number of different genes mapping to the 11q chromosomal region, associated with CCND1 amplification. The subsequent protein expression of these candidate genes was then examined in a clinical material of 500 primary breast cancers from premenopausal patients randomized to either tamoxifen or no adjuvant treatment. The protein expression was also compared to the CGH data in a subset of 56 breast cancer samples. Results: Cortactin and FADD overexpression was linked to CCND1 amplification, determined by FISH, but was not associated with a diminished effect of tamoxifen. However, deletion of distal chromosome 11q, defined as downregulation of the marker Chk1, was associated with an impaired tamoxifen response, and interestingly, also with low proliferative breast cancer of low grade. For Pak1 and cyclin D1 the protein expression corresponded to the gene expression data from the CGH analysis. Conclusions: The results indicate that many 11q13 associated gene products are overexpressed in conjunction with cyclin D1 but not linked to an agonistic effect of tamoxifen. Finally, the deletion of distal 11q, linked to 11q13 amplification, might be an important event affecting breast cancer outcome and tamoxifen response. Keywords: comparative genomic hybridisation 56 samples with 11q13 amplification have been analysed and compared with protein expression results from immunohistochemical analyses.

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Association of tamoxifen resistance and lipid reprogramming in breast cancer.

Publications

Association of tamoxifen resistance and lipid reprogramming in breast cancer.

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