Proteolysis Targeting Chimera (PROTAC) as a promising novel therapeutic modality for the treatment of triple-negative breast cancer (TNBC)

Breast cancer (BC) is considered one of the most prevalent malignancies impacting women worldwide, constituting 15% of all new cancer cases. It is classified according to its molecular targets into three subtypes; HR+/ERBB2-, ERBB2+/HR+, or HR- and triple-negative breast cancer (TNBC). TNBC is considered aggressive cancer with bad prognosis and poor clinical outcomes. It lacks estrogen, progesterone, and ERBB2 receptors rendering its treatment more challenging. Owing to its unresponsiveness to hormonal therapy, quick tumor growth, and the high probability to have spread at the time of discovery, it is more likely to recur following therapy. Proteolysis Targeting Chimeric molecules (PROTACs) are hetero-bifunctional molecules that are able to hijack the ubiquitin-proteasome system, a major physiological proteolytic mechanism. This leads to ubiquitination through endogenous E3 ligases and subsequent degradation through 26-S proteasome. Since its discovery in 2001, PROTACs have been considered an important therapeutic modality due to their ability to target and degrade undruggable proteins. In vitro studies have been conducted to investigate the possibility of using PROTACs as a therapeutic modality in TNBC. Data available propose great potential of PROTACs technology as a major candidate in TNBC management. Further in vitro and in vivo clinical trials are required to establish a definitive decision. In this review, we aim to give a brief overview of TNBC and PROTACs and highlight the rationale behind using PROTACs as a therapeutic modality in patients with TNBC.