Abstract
Breast cancer is the most prevalent cancer in women worldwide. Triple-negative breast cancer (TNBC) is characterized by the lack of expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. It is the most aggressive subtype of breast cancer and accounts for 12–20% of all breast cancer cases. TNBC is associated with younger age of onset, greater metastatic potential, higher incidence of relapse, and lower overall survival rates. Based on molecular phenotype, TNBC has been classified into six subtypes (BL1, BL2, M, MES, LAR, and IM). TNBC treatment is challenging due to its heterogeneity, highly invasive nature, and relatively poor therapeutics response. Chemotherapy and radiotherapy are conventional strategies for the treatment of TNBC. Recent research in TNBC and mechanistic understanding of disease pathogenesis using cutting-edge technologies has led to the unfolding of new lines of therapies that have been incorporated into clinical practice. Poly (ADP-ribose) polymerase and immune checkpoint inhibitors have made their way to the current TNBC treatment paradigm. This review focuses on the classification, features, and treatment progress in TNBC. Histological subtypes connected to recurrence, molecular classification of TNBC, targeted therapy for early and advanced TNBC, and advances in non-coding RNA in therapy are the key highlights in this review.
Highlights
The two major classes of non‐coding RNA studied in triple‐negative breast cancer (TNBC) development and treatment are miRNA and Long non‐coding RNA
MicroRNA is a small non‐coding RNA, usually 20‐22 nucleotides in length, regulating gene expres‐ sion. miRNA is known to bind to the 3'untranslated region of mRNA
Tumour suppressor miRNAs, involved in tumour develop‐ ment, miR‐190a, miR‐136‐5p, miR‐126‐5p, miR‐135b‐5p and miR‐182‐5p are downregulated in TNBC [158]. miR‐22 is downregulation in TNBC, is associated with migration and metastasis. miR‐22 exerts its effect through eukaryotic elonga‐ tion factor 2 kinase expression, which activates PI3K signaling pathway [159]
Summary
Most TNBC is categorized as no special type (IDC‐NST) [17]. Most IDC is characterized by pleomorphic cells with prominent nucleoli. The rest of the tumors are categorized into 47 specific subtypes, such as invasive lobular carcinoma (relatively common), metaplastic carcinoma, medullary carcinoma, mucinous carci‐ noma, adenoid cystic carcinoma, secretory carcinoma, acinic cell carcinoma, neuroendocrine tumors, as well as the rarest glycogen‐rich clear cell carcinoma [19,20] Among these specific subtypes (Fig. 1), medullary breast carcinoma occurs in
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