The Role of MicroRNAs in HER2-Positive Breast Cancer: Where We Are and Future Prospective.

Breast cancer that highly expresses human epidermal growth factor receptor 2 (HER2+) represents one of the major breast cancer subtypes, and was associated with a poor prognosis until the introduction of HER2-targeted therapies such as trastuzumab. Unfortunately, up to 30% of patients with HER2+ localized breast cancer continue to relapse, despite treatment. MicroRNAs (miRNAs) are small (approximately 20 nucleotides long) non-coding regulatory oligonucleotides. They function as post-transcriptional regulators of gene expression, binding complementarily to a target mRNA and leading to the arrest of translation or mRNA degradation. In the last two decades, translational research has focused on these small molecules because of their highly differentiated expression patterns in blood and tumor tissue, as well as their potential biological function. In cancer research, they have become pivotal for the thorough understanding of oncogenic biological processes. They might also provide an efficient approach to early monitoring of tumor progression or response to therapy. Indeed, changes in their expression patterns can represent a flag for deeper biological changes. In this review, we sum up the recent literature regarding miRNAs in HER2+ breast cancer, taking into account their potential as powerful prognostic and predictive biomarkers, as well as therapeutic tools.

What if the future of HER2-positive breast cancer patients was written in miRNAs? An exploratory analysis from NeoALTTO study.

BACKGROUND: Neoadjuvant therapy with dual HER2 blockade improved pathological complete response (pCR) rate in HER2-positive breast cancer patients. Nevertheless, it would be desirable to identify patients exquisitely responsive to single agent trastuzumab to minimize or avoid overtreatment. Herein, we evaluated the predictive and prognostic value of basal primary tumor miRNA expression profile within the trastuzumab arm of NeoALTTO study (ClinicalTrials.gov Identifier: NCT00553358). METHODS: RNA samples from baseline biopsies were randomized into training (n = 45) and testing (n = 47) sets. After normalization, miRNAs associated with Event-free survival (EFS) and pCR were identified by univariate analysis. Multivariate models were implemented to generate specific signatures which were first confirmed, and then analyzed together with other clinical and pathological variables. RESULTS: We identified a prognostic signature including hsa-miR-153-3p (HR 1.831, 95% CI: 1.34-2.50) and hsa-miR-219a-5p (HR 0.629, 95% CI: 0.50-0.78). For two additional miRNAs (miR-215-5p and miR-30c-2-3p), we found a statistically significant interaction term with pCR (p.interaction: 0.017 and 0.038, respectively). Besides, a two-miRNA signature was predictive of pCR (hsa-miR-31-3p, OR 0.70, 95% CI: 0.53-0.92, and hsa-miR-382-3p, OR: 1.39, 95% CI: 1.01-1.91). Notably, the performance of this predictive miRNA signature resembled that of the genomic classifiers PAM50 and TRAR, and did not improve when the extended models were fitted. CONCLUSION: Analyses of primary tumor tissue miRNAs hold the potential of a parsimonious tool to identify patients with differential clinical outcomes after trastuzumab based neoadjuvant therapy.

Breast Cancer Drug Resistance: Overcoming the Challenge by Capitalizing on MicroRNA and Tumor Microenvironment Interplay.

The clinical management of breast cancer reaches new frontiers every day. However, the number of drug resistant cases is still high, and, currently, this constitutes one of the major challenges that cancer research has to face. For instance, 50% of women affected with HER2 positive breast cancer presents or acquires resistance to trastuzumab. Moreover, for patients affected with triple negative breast cancer, standard chemotherapy is still the fist-line therapy, and often patients become resistant to treatments. Tumor microenvironment plays a crucial role in this context. Indeed, cancer-associated stromal cells deliver oncogenic cues to the tumor and vice versa to escape exogenous insults. It is well known that microRNAs are among the molecules exploited in this aberrant crosstalk. Indeed, microRNAs play a crucial function both in the induction of pro-tumoral traits in stromal cells and in the stroma-mediated fueling of tumor aggressiveness. Here, we summarize the most recent literature regarding the involvement of miRNAs in the crosstalk between tumor and stromal cells and their capability to modulate tumor microenvironment characteristics. All up-to-date findings suggest that microRNAs in the TME could serve both to reverse malignant phenotype of stromal cells, modulating response to therapy, and as predictive/prognostic biomarkers.

Circulating miRNAs as Novel Non-Invasive Biomarkers to Aid the Early Diagnosis of Suspicious Breast Lesions for Which Biopsy Is Recommended.

In population-based screens, tissue biopsy remains the standard practice for women with imaging that suggests breast cancer. We examined circulating microRNAs as minimally invasive diagnostic biomarkers to discriminate malignant from benign breast lesions. miRNAs were analyzed by OpenArray in a retrospective cohort of plasma samples including 100 patients with malignant (T), 89 benign disease (B), and 99 healthy donors (HD) divided into training and testing sets and a prospective cohort (BABE) of 289 women with suspicious imaging findings who underwent tissue biopsy. miRNAs associated with disease status were identified by univariate analysis and then combined into signatures by multivariate logistic regression models. By combining 16 miRNAs differentially expressed in the T vs. HD comparison, 26 signatures were also able to significantly discriminate T from B disease. Seven of them, involving 5 specific miRNAs (miR-625, miR-423-5p, miR-370-3p, miR-181c, and miR-301b), were statistically validated in the testing set. Among the 7 signatures, the discriminatory performances of 5 were confirmed in the prospective BABE Cohort. This study identified 5 circulating miRNAs that, properly combined, distinguish malignant from benign breast disease in women with a high likelihood of malignancy.

Mexican Ganoderma Lucidum Extracts Decrease Lipogenesis Modulating Transcriptional Metabolic Networks and Gut Microbiota in C57BL/6 Mice Fed with a High-Cholesterol Diet.

Prevention of hyperlipidemia and associated diseases is a health priority. Natural products, such as the medicinal mushroom Ganoderma lucidum (Gl), have demonstrated hypocholesterolemic, prebiotic and antidiabetic properties. However, the underlying transcriptomic mechanisms by which Gl exerts bioactivities are not completely understood. We report a comprehensive hepatic and renal transcriptome profiling of C57BL/6 mice under the consumption of a high-cholesterol diet and two standardized Gl extracts obtained from basidiocarps cultivated on conventional substrate (Gl-1) or substrate containing acetylsalicylic acid (ASA; Gl-2). We showed that Gl extracts modulate relevant metabolic pathways involving the restriction of lipid biosynthesis and the enrichment of lipid degradation and secretion. The Gl-2 extract exerts a major modulation over gene expression programs showing the highest similarity with simvastatin druggable-target-genes and these are enriched more in processes related to human obesity alterations in the liver. We further show a subset of Gl-modulated genes correlated with Lactobacillus enrichment and the reduction of circulating cholesterol-derived fats. Moreover, Gl extracts induce a significant decrease of macrophage lipid storage, which occurs concomitantly with the down-modulation of Fasn and Elovl6. Collectively, this evidence suggests a new link between Gl hypocholesterolemic and prebiotic activity, revealing thereby that standardized Mexican Gl extracts are a novel transcriptome modulator to prevent metabolic disorders associated with hypercholesterolemia.

miR-205 in Breast Cancer: State of the Art.

Despite its controversial roles in different cancer types, miR-205 has been mainly described as an oncosuppressive microRNA (miRNA), with some contrasting results, in breast cancer. The role of miR-205 in the occurrence or progression of breast cancer has been extensively studied since the first evidence of its aberrant expression in tumor tissues versus normal counterparts. To date, it is known that the expression of miR-205 in the different subtypes of breast cancer is decreasing from the less aggressive subtype, estrogen receptor/progesterone receptor positive breast cancer, to the more aggressive, triple negative breast cancer, influencing metastasis capability, response to therapy and patient survival. In this review, we summarize the most important discoveries that have highlighted the functional role of this miRNA in breast cancer initiation and progression, in stemness maintenance, in the tumor microenvironment, its potential role as a biomarker and its relevance in normal breast physiology-the still open questions. Finally, emerging evidence reveals the role of some lncRNAs in breast cancer progression as sponges of miR-205. Here, we also reviewed the studies in this field.

miR-9-Mediated Inhibition of EFEMP1 Contributes to the Acquisition of Pro-Tumoral Properties in Normal Fibroblasts.

Tumor growth and invasion occurs through a dynamic interaction between cancer and stromal cells, which support an aggressive niche. MicroRNAs are thought to act as tumor messengers to "corrupt" stromal cells. We previously demonstrated that miR-9, a known metastamiR, is released by triple negative breast cancer (TNBC) cells to enhance the transition of normal fibroblasts (NFs) into cancer-associated fibroblast (CAF)-like cells. EGF containing fibulin extracellular matrix protein 1 (EFEMP1), which encodes for the ECM glycoprotein fibulin-3, emerged as a miR-9 putative target upon miRNA's exogenous upmodulation in NFs. Here we explored the impact of EFEMP1 downmodulation on fibroblast's acquisition of CAF-like features, and how this phenotype influences neoplastic cells to gain chemoresistance. Indeed, upon miR-9 overexpression in NFs, EFEMP1 resulted downmodulated, both at RNA and protein levels. The luciferase reporter assay showed that miR-9 directly targets EFEMP1 and its silencing recapitulates miR-9-induced pro-tumoral phenotype in fibroblasts. In particular, EFEMP1 siRNA-transfected (si-EFEMP1) fibroblasts have an increased ability to migrate and invade. Moreover, TNBC cells conditioned with the supernatant of NFs transfected with miR-9 or si-EFEMP1 became more resistant to cisplatin. Overall, our results demonstrate that miR-9/EFEMP1 axis is crucial for the conversion of NFs to CAF-like cells under TNBC signaling.

MiR-302b as a Combinatorial Therapeutic Approach to Improve Cisplatin Chemotherapy Efficacy in Human Triple-Negative Breast Cancer.

Introduction: Chemotherapy is still the standard of care for triple-negative breast cancers (TNBCs). Here, we investigated miR-302b as a therapeutic tool to enhance cisplatin sensitivity in vivo and unraveled the molecular mechanism. Materials and Methods: TNBC-xenografted mice were treated with miR-302b or control, alone or with cisplatin. Genome-wide transcriptome analysis and independent-validation of Integrin Subunit Alpha 6 (ITGA6) expression was assessed on mice tumor samples. Silencing of ITGA6 was performed to evaluate cisplatin response in vitro. Further, potential transcription factors of ITGA6 (E2F transcription facor 1 (E2F1), E2F transcription factor 2 (E2F2), and Yin Yang 1 (YY1)) were explored to define the miRNA molecular mechanism. The miR-302b expression was also assessed in TNBC patients treated with chemotherapy. Results: The miR-302b-cisplatin combination significantly impaired tumor growth versus the control through indirect ITGA6 downregulation. Indeed, ITGA6 was downmodulated in mice treated with miR-302b-cisplatin, and ITGA6 silencing increased drug sensitivity in TNBC cells. In silico analyses and preclinical assays pointed out the regulatory role of the E2F family and YY1 on ITGA6 expression under miR-302b-cisplatin treatment. Finally, miR-302b enrichment correlated with better overall survival in 118 TNBC patients. Conclusion: MiR-302b can be exploited as a new therapeutic tool to improve the response to chemotherapy, modulating the E2F family, YY1, and ITGA6 expression. Moreover, miR-302b could be defined as a new prognostic factor in TNBC patients.

MicroRNA and Oxidative Stress Interplay in the Context of Breast Cancer Pathogenesis.

Oxidative stress is a pathological condition determined by a disturbance in reactive oxygen species (ROS) homeostasis. Depending on the entity of the perturbation, normal cells can either restore equilibrium or activate pathways of cell death. On the contrary, cancer cells exploit this phenomenon to sustain a proliferative and aggressive phenotype. In fact, ROS overproduction or their reduced disposal influence all hallmarks of cancer, from genome instability to cell metabolism, angiogenesis, invasion and metastasis. A persistent state of oxidative stress can even initiate tumorigenesis. MicroRNAs (miRNAs) are small non coding RNAs with regulatory functions, which expression has been extensively proven to be dysregulated in cancer. Intuitively, miRNA transcription and biogenesis are affected by the oxidative status of the cell and, in some instances, they participate in defining it. Indeed, it is widely reported the role of miRNAs in regulating numerous factors involved in the ROS signaling pathways. Given that miRNA function and modulation relies on cell type or tumor, in order to delineate a clearer and more exhaustive picture, in this review we present a comprehensive overview of the literature concerning how miRNAs and ROS signaling interplay affects breast cancer progression.

MicroRNAs and DNA-Damaging Drugs in Breast Cancer: Strength in Numbers.

MicroRNAs are a class of small non-coding regulatory RNAs playing key roles in cancer. Breast cancer is the most common female malignancy worldwide and is categorized into four molecular subtypes: luminal A and B, HER2+ and triple-negative breast cancer (TNBC). Despite the development of multiple targeted therapies for luminal and HER2+ breast tumors, TNBC lacks specific therapeutic approaches, thus they are treated mainly with radio- and chemotherapy. The effectiveness of these therapeutic regimens is based on their ability to induce DNA damage, which is differentially resolved and repaired by normal vs. cancer cells. Recently, drugs directly targeting DNA repair mechanisms, such as PARP inhibitors, have emerged as attractive candidates for the future molecular targeted-therapy in breast cancer. These compounds prevent cancer cells to appropriate repair DNA double strand breaks and induce a phenomenon called synthetic lethality, that results from the concurrent inhibition of PARP and the absence of functional BRCA genes which prompt cell death. MicroRNAs are relevant players in most of the biological processes including DNA damage repair mechanisms. Consistently, the downregulation of DNA repair genes by miRNAs have been probe to improve the therapeutic effect of genotoxic drugs. In this review, we discuss how microRNAs can sensitize cancer cells to DNA-damaging drugs, through the regulation of DNA repair genes, and examine the most recent findings on their possible use as a therapeutic tools of treatment response in breast cancer.

Loss of function of miR-342-3p results in MCT1 over-expression and contributes to oncogenic metabolic reprogramming in triple negative breast cancer.

Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive neoplasia lacking the expression of hormonal receptors and human epidermal growth factor receptor-2. Accumulating evidence has highlighted the importance of miRNAs dysregulation in the establishment of cancer programs, but the functional role of many miRNAs remains unclear. The description of miRNAs roles might provide novel strategies for treatment. In the present work, an integrated analysis of miRNA transcriptional landscape was performed (N = 132), identifying the significant down-modulation of miR-342-3p in TNBC, probably because of the aberrant activity of estrogen receptor, which serves as a transcription factor of the miRNA, as demonstrated by a siRNA-knockdown approach. The enhanced expression of miR-342-3p significantly decreased cell proliferation, viability and migration rates of diverse TN cells in vitro. Bioinformatic and functional analyses revealed that miR-342-3p directly targets the monocarboxylate transporter 1 (MCT1), which promotes lactate and glucose fluxes alteration, thus disrupting the metabolic homeostasis of tumor cells. Optical metabolic imaging assay defined a higher optical redox ratio in glycolytic cells overexpressing miR-342-3p. Furthermore, we found that hypoxic conditions and glucose starvation attenuate miR-342-3p expression, suggesting a crosstalk program between these metabolic factors. Consistently, miR-342-3p down-modulation is associated with an increased MCT1 expression level and glycolytic score in human triple negative tumors. Overall, we described for the first time the regulatory activity of miR-342-3p on relevant metabolic carcinogenic pathways in TN breast cancers.