PIWI-interacting RNAs: new biomarkers for diagnosis and treatment of breast cancer

Abstract

Cancer is one of the most important reasons of mortality in the world. However, there are several therapeutic platforms to treat patients who suffering from cancer common treatments such as surgery, chemotherapy and etc. The current therapeutic approaches are related to some limitations. Hence, more understanding about molecular mechanisms that involved in cancer particularly in breast cancer pathogenesis, could contribute to provide better therapeutic platforms. Recently, non-coding RNAs such as microRNAs have attracted researchers' attention in the field of cancer due to their functions in gene expression's regulation and functional interactions with other molecules. Interestingly, great advances in next-generation sequencing lead to considering other roles for another non-coding RNAs subgroup called PIWI-interacting RNAs (piRNAs) in addition to their functions in the germline. Novel studies investigated the role of piRNAs in several cancers including lung cancer, hepatocellular carcinoma, gastric cancer, multiple myeloma and colorectal cancer. Hopefully, based on new findings, piRNAs may be a potential biomarker which can be used as a tool to diagnose or treat breast cancer. Thus, this review aimed to discuss the role of piRNAs in breast cancer progression and metastasis as well as its molecular mechanisms.

Breast Cancer and the Other Non-Coding RNAs

“…The piRNAs are 26–31 nucleotides long and associated with PIWI proteins which are a clade in the Argonaute protein family [ 120 , 121 ]. Piwi indicates “P-element–induced wimpy testes’, and their presence in eukaryotic cells was discovered in mouse sperm cells in 2006 [ 122 ].…”

“…Piwi indicates “P-element–induced wimpy testes’, and their presence in eukaryotic cells was discovered in mouse sperm cells in 2006 [ 122 ]. While their initial presence in human cells was demonstrated in germline and stem-cells [ 123 ], they are also present in differentiated somatic cells, but in significantly smaller numbers [ 120 , 121 ]. However, over 30,000 piRNAs are currently described in the eukaryotic genome [ 122 ].…”

“…The main piRNA role is silencing of transposable elements (TE) in the germline cells at both transcriptional and post-transcriptional levels. Although this function is conserved in most animal species, different proteins and mechanisms can be involved [ 120 , 121 , 122 ]. Post transcriptional gene silencing (PTGS) of TE elements occurs in the cytoplasm, where the target transcript is sliced, and cleavage-competent Piwi-proteins are required for this processing.…”

Increased Expression of DNA2 Was Linked to Poor Prognosis in Breast Cancer

“…According to the expression status of three receptors: the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor (HER2), breast cancer has been classified into Luminal A (LumA), Luminal B (LumB), epidermal growth factor receptor ERBB2/HER2-overexpressing (HER2+), and basal epithelial-like (BL). This can be helpful to predict patient outcomes and provide new choices for treatment [ 3 – 5 ]. In current practice, treatment options for breast cancer patients consist of surgery, chemotherapy, radiotherapy or targeting of classical markers of breast cancer subtype, and emerging new therapy [ 5 ].…”

“…In current practice, treatment options for breast cancer patients consist of surgery, chemotherapy, radiotherapy or targeting of classical markers of breast cancer subtype, and emerging new therapy [ 5 ]. However, these treatments have some limitations, and new studies are needed [ 3 , 6 , 7 ]. So uncovering and improved understanding of novel biomarkers could effectively contribute to improving patient stratification and treatment.…”