Abstract
Breast cancer is one of the most prevalent diseases among women worldwide and is highly associated with cancer-related mortality. Of the four major molecular subtypes, HER2-positive and triple-negative breast cancer (TNBC) comprise more than 30% of all breast cancers. While the HER2-positive subtype lacks estrogen and progesterone receptors and overexpresses HER2, the TNBC subtype lacks estrogen, progesterone and HER2 receptors. Although advances in molecular biology and genetics have substantially ameliorated breast cancer disease management, targeted therapies for the treatment of estrogen-receptor negative breast cancer patients are still restricted, particularly for TNBC. On the other hand, it has been demonstrated that microRNAs, miRNAs or small non-coding RNAs that regulate gene expression are involved in diverse biological processes, including carcinogenesis. Moreover, circulating miRNAs in serum/plasma are among the most promising diagnostic/therapeutic tools as they are stable and relatively easy to quantify. Various circulating miRNAs have been identified in several human cancers including specific breast cancer subtypes. This review aims to discuss the role of circulating miRNAs as potential diagnostic and prognostic biomarkers as well as therapeutic targets for estrogen-receptor negative breast cancers, HER2+ and triple negative.
Highlights
Breast cancer is the second most common cancer worldwide, and it affects more than two million women accounting for around half a million deaths annually [1]
Analysis by qPCR in triple-negative breast cancer (TNBC) patients revealed that the expression of ci-miRNA-34a/34b/34c is significantly reduced in TNBC patients compared to controls; while, low miRNA-34a/c expression correlate with tumor progression and worse prognosis and miRNA-34b is significantly associated with lymph node positivity [133]
Several studies have shown that ci-miRNAs play a crucial role in dysregulating gene expression via several major pathways involved in inhibiting apoptosis and inducing breast cancer invasion and metastasis [142,143]
Summary
Breast cancer is the second most common cancer worldwide, and it affects more than two million women accounting for around half a million deaths annually [1]. Other ci-miRNAs are found to be involved in the onset and development of tumor progression as well as in the invasion and metastasis of cancer [80] In this regard, release of immunosuppressive miRNAs allows cancer cells damage by T and B cells; on the other hand, vital role in carcinogenesis and its progression [87]. Release of immunosuppressive miRNAs allows cancer cells damage by T and B cells; on the other hand, vital role in carcinogenesis and its progression [87] Based on these studies it is clear that ci-miRNAs could be used as promising biomarkers and therapeutic targets for different types of cancers including estrogen-receptor negative breast cancers (Figure 1)
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