Abstract
Biomarkers can be used for diagnosis, prognosis, and prediction in targeted therapy. The estrogen receptor α (ERα) and human epidermal growth factor receptor 2 (HER2) are standard biomarkers used in breast cancer for guiding disease treatment. The androgen receptor (AR), a nuclear hormone receptor, contributes to the development and progression of prostate tumors and other cancers. With increasing evidence to support that AR plays an essential role in breast cancer, AR has been considered a useful biomarker in breast cancer, depending on the context of breast cancer sub-types. The existing survival analyses suggest that AR acts as a tumor suppressor in ER + ve breast cancers, serving as a favorable prognostic marker. However, AR functions as a tumor promoter in ER-ve breast cancers, including HER2 + ve and triple-negative (TNBC) breast cancers, serving as a poor prognostic factor. AR has also been shown to be predictive of the potential of response to adjuvant hormonal therapy in ER + ve breast cancers and to neoadjuvant chemotherapy in TNBC. However, conflicting results do exist due to intrinsic molecular differences between tumors and the scoring method for AR positivity. Applying AR expression status to guide treatment in different breast cancer sub-types has been suggested. In the future, AR will be a feasible biomarker for breast cancer. Clinical trials using AR antagonists in breast cancer are active. Targeting AR alone or other therapeutic agents provides alternatives to existing therapy for breast cancer. Therefore, AR expression will be necessary if AR-targeted treatment is to be used.
Highlights
Biomarkers can be used for diagnosis, prognosis, and prediction in targeted therapy
In a study of 559 triple-negative breast cancer (TNBC) cases, the results indicated that androgen receptor (AR) expression was associated with a worse prognostic outcome in terms of overall survival (OS); for patients without lymph node metastasis, AR + ve patients had poor OS and disease-free survival (DFS), in which the risks of mortality and recurrence were three times higher compared with the AR-ve patients [58]
AR functions as a tumor suppressor mainly by antagonizing with estrogen receptor α (ERα) in ER + ve breast cancer, and the mechanisms that may be involved in this process have been updated by recently published studies
Summary
The word “biomarker” is derived from the term “biological marker”, referring to a specific indicator of disease in patients that differ from a healthy person, reflecting the connection between a health hazard and a biological state. The well-accepted concept of a biomarker is defined by the US National Cancer Institute (NCI), stating that a biomarker is a biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, condition, or disease. Depending on different clinical applications, cancer biomarkers can be classified into three major types: diagnostic, prognostic, and predictive biomarkers to help narrow down the diagnostic conditions for a specific diagnosis, to provide information regarding the aggressiveness of identified tumors for monitoring disease progression, and estimating. Biomolecules 2022, 12, 72 the overall outcome of the patient without treatment, and to predict treatment response in order to determine the most effective therapeutic strategy, respectively, each of which provides information for optimizing the clinical care of patients. This review will mainly focus on discussing the use of androgen receptor (AR) as a prognostic and predictive biomarker for breast cancer management and treatment
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