Enhancer-Driven lncRNA BDNF-AS Induces Endocrine Resistance and Malignant Progression of Breast Cancer through the RNH1/TRIM21/mTOR Cascade

Long noncoding RNAs in triple-negative breast cancer: A new frontier in the regulation of tumorigenesis

In recent years, triple-negative breast cancer (TNBC) has emerged as the most aggressive subtype of breast cancer and is usually associated with increased mortality worldwide. The severity of TNBC is primarily observed in younger women, with cases ranging from approximately 12%-24% of all breast cancer cases. The existing hormonal therapies offer limited clinical solutions in completely circumventing the TNBC, with chemoresistance and tumor recurrences being the common hurdles in the path of TNBC treatment. Accumulating evidence has correlated the dysregulation of long noncoding RNAs (lncRNAs) with increased cell proliferation, invasion, migration, tumor growth, chemoresistance, and decreased apoptosis in TNBC. Various clinical studies have revealed that aberrant expression of lncRNAs in TNBC tissues is associated with poor prognosis, lower overall survival, and disease-free survival. Due to these specific characteristics, lncRNAs have emerged as novel diagnostic and prognostic biomarkers for TNBC treatment. However, the underlying mechanism through which lncRNAs perform their actions remains unclear, and extensive research is being carried out to reveal it. Therefore, understanding of mechanisms regulating the modulation of lncRNAs will be a substantial breakthrough in effective treatment therapies for TNBC. This review highlights the association of several lncRNAs in TNBC progression and treatment, along with their possible functions and mechanisms.

Progress of Breast Cancer basic research in China

Breast cancer is the most commonly diagnosed and the most lethal cancer in females both in China and worldwide. Currently, the origin of cancer stem cells, the heterogeneity of cancer cells, the mechanism of cancer metastasis and drug resistance are the most important issues that need to be addressed. Chinese investigators have recently made new discoveries in basic breast cancer researches, especially regarding cancer stem cells, cancer metabolism, and microenvironments. These efforts have led to a deeper understanding of drug resistance and metastasis and have also indicated new biomarkers and therapeutic targets. These findings emphasized the importance of the cancer stem cells for targeted therapy. In this review, we summarized the latest important findings in this field in China.

Molecular Mechanism of Secondary Endocrine Resistance in Luminal Breast Cancer

OBJECTIVE

The molecular mechanism of secondary resistance in Luminal breast cancer was studied to provide new ideas for the treatment of breast cancer.

METHODS

The sensitivity of the downregulation of myeloid leukemia factor 1-interacting proteins (MLF1IP) to Tamoxifen (TAM) was tested by the Cell Counting Kit-8 (CCK-8). The apoptosis of MLF1IP-mediated resistance was analyzed by flow cytometry (FCM) with/without TAM. Western blot was used in detecting various kinds of apoptosis and the expression of the protein related to the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway to study the molecular mechanism of secondary endocrine resistance in Luminal breast cancer.

RESULTS

The downregulation of MLF1IP could significantly increase the drug sensitivity of Michigan Cancer Foundation-7 (MCF-7) cells and also inhibit the proliferation of MCF-7 cells under the stimulation of drugs. Western blot results showed that the expression of Bcl-2-associated X (BAX), Caspase3, Caspase7, and Caspase9 proteins increased when MLF1IP was downregulated. The results of the PI3K/AKT signaling pathway revealed that the phosphatase and tensin homolog deleted on chromosome ten (PTEN) protein expression of MCF7-shRNA was higher than that of MCF7-NC cells, while the expression of p-AKT was lower than that of MCF7-NC cells.

CONCLUSIONS

(1) MLF1IP-related apoptosis resistance plays an essential role in MLF1IP-mediated secondary resistance of breast cancer cells. (2) MLF1IP promotes AKT phosphorylation by inhibiting the PTEN expression, thus activating the PI3K/AKT signaling pathway and causing the secondary resistance of Luminal breast cancer. (3) MLF1IP can be used as a factor to predict the endocrine resistance of Luminal breast cancer.

Multidimensional crosstalk between RNA-binding proteins and noncoding RNAs in cancer biology

RNA-binding proteins (RBPs) are well-known to bind RNA via a set of RNA-binding domains (RBDs) and determine the fate and function of their RNA targets; inversely, some RBPs, in certain cases, may be modulated by the bound RNAs rather than regulate their RNA partners. Current proteome-wide studies reveal that almost half of RBPs have no canonical RBDs, and the discovery of tens of thousands of noncoding RNAs (ncRNAs), especially those with the size larger than 200 nt (namely long noncoding RNAs, lncRNAs), makes the crosstalk between RBPs and RNAs more complicated. It is clear that macromolecular complexes formed by RBP and RNA are not only a form of existence of their RBP and RNA components in cells, but also represent a functional entity through which those RBPs and regulatory ncRNAs participate in the construction of regulatory networks in organism. In this review, we summarize the multidimensional crosstalk between RBPs and ncRNAs in cancer and discuss how RBPs achieve their function via the bound ncRNAs in different aspects of gene expression as well as how RBPs direct modification and processing of ncRNAs, in order to better understand tumor biology and provide new insights into development of strategies for cancer therapy and early detection.

Angiogenin (ANG)-Ribonuclease Inhibitor (RNH1) System in Protein Synthesis and Disease

Protein synthesis is a highly complex process executed by well-organized translation machinery. Ribosomes, tRNAs and mRNAs are the principal components of this machinery whereas RNA binding proteins and ribosome interacting partners act as accessory factors. Angiogenin (ANG)-Ribonuclease inhibitor (RNH1) system is one such accessory part of the translation machinery that came into focus afresh due to its unconventional role in the translation. ANG is conventionally known for its ability to induce blood vessel formation and RNH1 as a "sentry" to protect RNAs from extracellular RNases. However, recent studies suggest them to be important in translation regulation. During cell homeostasis, ANG in the nucleus promotes rRNA transcription. While under stress, ANG translocates to the cytosol and cleaves tRNA into fragments which inhibit ribosome biogenesis and protein synthesis. RNH1, which intimately interacts with ANG to inhibit its ribonucleolytic activity, can also bind to the 40S ribosomes and control translation by yet to be known mechanisms. Here, we review recent advancement in the knowledge of translation regulation by the ANG-RNH1 system. We also gather information about this system in cell homeostasis as well as in pathological conditions such as cancer and ribosomopathies. Additionally, we discuss the future research directions and therapeutic potential of this system.

Non-coding RNAs rewire cancer metabolism networks

Non-coding RNAs (ncRNAs) are functional RNAs with limited or no protein-coding ability. These interact with their target molecules and participate in the precise regulation of disease development. Metabolic reprogramming is a hallmark in cancer, and is considered essential in meeting increased macromolecular biosynthesis and energy generation of tumors. Recent studies have revealed the involvement of ncRNAs in several metabolic regulations of cancer through direct modulation of metabolic enzyme activities or participation of metabolism-related signaling pathways. Elucidation of how ncRNAs regulate metabolic reprogramming of cancers has opened up a novel intention to understand the mechanism of metabolic rewiring and also the opportunities of utilizing ncRNA-based therapeutics for targeting the metabolism in cancer treatment.

Emerging Roles of Long Noncoding RNAs in the Cytoplasmic Milieu

While the important functions of long noncoding RNAs (lncRNAs) in nuclear organization are well documented, their orchestrating and architectural roles in the cytoplasmic environment have long been underestimated. However, recently developed fractionation and proximity labelling approaches have shown that a considerable proportion of cellular lncRNAs is exported into the cytoplasm and associates nonrandomly with proteins in the cytosol and organelles. The functions of these lncRNAs range from the control of translation and mitochondrial metabolism to the anchoring of cellular components on the cytoskeleton and regulation of protein degradation at the proteasome. In the present review, we provide an overview of the functions of lncRNAs in cytoplasmic structures and machineries und discuss their emerging roles in the coordination of the dense intracellular milieu. It is becoming apparent that further research into the functions of these lncRNAs will lead to an improved understanding of the spatiotemporal organization of cytoplasmic processes during homeostasis and disease.

The roles of long noncoding RNAs in breast cancer metastasis

Breast cancer is the most significant threat to female health. Breast cancer metastasis is the major cause of mortality in breast cancer patients. To fully unravel the molecular mechanisms that underlie the breast cancer cell metastasis is critical for developing strategies to improve survival and prognosis in breast cancer patients. Recent studies have revealed that the long noncoding RNAs (lncRNAs) are involved in breast cancer metastasis through a variety of molecule mechanisms, though the precise functional details of these lncRNAs are yet to be clarified. In the present review, we focus on the functions of lncRNAs in breast cancer invasion and metastasis, with particular emphasis on the functional properties, the regulatory factors, the therapeutic promise, as well as the future challenges in studying these lncRNA.