Autoantibodies Specific to ERα are Involved in Tamoxifen Resistance in Hormone Receptor Positive Breast Cancer

Tamoxifen resistance is a major hurdle in the treatment of estrogen receptor (ER)-positive breast cancer. The mechanisms of tamoxifen resistance are not fully understood although several underlying molecular events have been suggested. Recently, we identified autoantibodies reacting with membrane-associated ERα (anti-ERα Abs) in sera of breast cancer patients, able to promote tumor growth. Here, we investigated whether anti-ERα Abs purified from sera of ER-positive breast cancer patients could contribute to tamoxifen resistance. Anti-ERα Abs inhibited tamoxifen-mediated effects on cell cycle and proliferation in MCF-7 cells. Moreover, anti-ERα Abs hampered the tamoxifen-mediated reduction of tumor growth in SCID mice xenografted with breast tumor. Notably, simvastatin-mediated disaggregation of lipid rafts, where membrane-associated ERα is embedded, restored tamoxifen sensitivity, preventing anti-ERα Abs effects. In conclusion, detection of serum anti-ERα Abs may help predict tamoxifen resistance and concur to appropriately inform therapeutic decisions concerning hormone therapy in ER-positive breast cancer patients.

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O-56 High expression of sphingosine 1-phosphate receptors, S1P1 and S1P3, sphingosine kinase 1 and ERK-1/2 is associated with development of tamoxifen resistance in ER positive breast cancer patients

European Journal of Cancer Supplements ◽

10.1016/j.ejcsup.2010.06.057 ◽

2010 ◽

Vol 8 (6) ◽

pp. 21 ◽

Cited By ~ 1

Author(s):

Carol Watson ◽

Jaclyn S. Long ◽

Clare Orange ◽

Claire L. Tannahill ◽

Elizabeth Mallon ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Patients ◽

Tamoxifen Resistance ◽

Sphingosine Kinase ◽

High Expression ◽

Sphingosine Kinase 1 ◽

Breast Cancer Patients ◽

Sphingosine 1 Phosphate ◽

Er Positive ◽

Positive Breast Cancer

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The Utility of SOX2 and AGR2 Biomarkers as Early Predictors of Tamoxifen Resistance in ER-Positive Breast Cancer Patients

International Journal of Surgical Oncology ◽

10.1155/2021/9947540 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Yomna Zamzam ◽

Yosra Abdelmonem Zamzam ◽

Marwa Aboalsoud ◽

Heba Harras

Keyword(s):

Breast Cancer ◽

Cancer Patients ◽

Tamoxifen Resistance ◽

Tamoxifen Treatment ◽

Time To Failure ◽

Breast Cancer Patients ◽

Early Predictors ◽

Er Positive ◽

Group 1 ◽

Positive Breast Cancer

Background. Despite the undeniable benefit of tamoxifen therapy for ER-positive breast cancer patients, approximately one-third of those patients either do not respond to tamoxifen or develop resistance. Thus, it is a crucial step to identify novel, reliable, and easily detectable biomarkers indicating resistance to this drug. Objective. The aim of this work is to explore SOX2 and AGR2 biomarker expression in the tumor tissue of ER-positive breast cancer patients in combination with the evaluation of serum AGR2 level of these patients in order to validate these biomarkers as early predictors of tamoxifen resistance. Methods. This study was conducted on 224 ER-positive breast cancer patients. All patients were primarily subjected to serum AGR2 levelling by ELISA and their breast cancer tissue immunostained for SOX2 and AGR2. After 5 years of follow-up, the patients were divided into 3 groups: group 1 was tamoxifen sensitive and groups 2 and 3 were tamoxifen resistant. Time to failure of tamoxifen treatment was considered the time from the beginning of tamoxifen therapy to the time of discovery of breast cancer recurrence or metastases (in months). Results. SOX2 and AGR2 biomarkers expression and serum AGR2 level were significantly higher in groups 2 and 3 in comparison to group 1, while the relationship between Her2 neu expression and Ki67 index in the 3 different groups was statistically nonsignificant. Lower SOX2 and AGR2 expression and low AGR2 serum levels in the studied patients of groups 2 and 3 were significantly associated with longer time-to-failure of tamoxifen treatment. According to the ROC curve, the combined use of studied markers validity was with a sensitivity of 100%, specificity of 96%, PPV 96%, and NPV 100% ( p < 0.001 ; AUC: 0.984). Conclusions. Integrated use of SOX2 and AGR2 biomarkers with serum AGR2 assay holds a promising hope for their future use as predictive markers for early detection of tamoxifen resistance in ER-positive breast cancer patients.

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Clinical CYP2D6 Genotyping to Personalize Adjuvant Tamoxifen Treatment in ER-Positive Breast Cancer Patients: Current Status of a Controversy

Cancers ◽

10.3390/cancers13040771 ◽

2021 ◽

Vol 13 (4) ◽

pp. 771

Author(s):

Tessa A. M. Mulder ◽

Mirjam de With ◽

Marzia del Re ◽

Romano Danesi ◽

Ron H. J. Mathijssen ◽

...

Keyword(s):

Breast Cancer ◽

Clinical Outcome ◽

Cancer Patients ◽

Plasma Concentrations ◽

Tamoxifen Treatment ◽

Current Status ◽

Endocrine Treatment ◽

Breast Cancer Patients ◽

Er Positive ◽

Positive Breast Cancer

Tamoxifen is a major option for adjuvant endocrine treatment in estrogen receptor (ER) positive breast cancer patients. The conversion of the prodrug tamoxifen into the most active metabolite endoxifen is mainly catalyzed by the enzyme cytochrome P450 2D6 (CYP2D6). Genetic variation in the CYP2D6 gene leads to altered enzyme activity, which influences endoxifen formation and thereby potentially therapy outcome. The association between genetically compromised CYP2D6 activity and low endoxifen plasma concentrations is generally accepted, and it was shown that tamoxifen dose increments in compromised patients resulted in higher endoxifen concentrations. However, the correlation between CYP2D6 genotype and clinical outcome is still under debate. This has led to genotype-based tamoxifen dosing recommendations by the Clinical Pharmacogenetic Implementation Consortium (CPIC) in 2018, whereas in 2019, the European Society of Medical Oncology (ESMO) discouraged the use of CYP2D6 genotyping in clinical practice for tamoxifen therapy. This paper describes the latest developments on CYP2D6 genotyping in relation to endoxifen plasma concentrations and tamoxifen-related clinical outcome. Therefore, we focused on Pharmacogenetic publications from 2018 (CPIC publication) to 2021 in order to shed a light on the current status of this debate.

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