Circulating microRNAs and therapy-associated cardiac events in HER2-positive breast cancer patients: an exploratory analysis from NeoALTTO

PURPOSE

The relevance of cardiotoxicity in the context of HER2-positive breast cancer is likely to increase with increasing patient treatment exposure, number of treatment lines, and prolonged survival. Circulating biomarkers to early identify patients at risk of cardiotoxicity could allow personalized treatment and follow-up measures. The aim of this study is to examine the relationship between circulating microRNAs and adverse cardiac events in HER2-positive breast cancer patients.

METHODS

We based our work on plasma samples from NeoALTTO trial obtained at baseline, after 2 weeks of anti-HER2 therapy, and immediately before surgery. Eleven patients experienced either a symptomatic or asymptomatic cardiac event. Circulating microRNAs were profiled in all patients presenting a cardiac event (case) and in an equal number of matched patients free of reported cardiac events (controls) using microRNA-Ready-to-Use PCR (Human panel I + II). Sensitivity analyses were performed by increasing the number of controls to 1:2 and 1:3. Normalized microRNA expression levels were compared between cases and controls using the non-parametric Kruskal-Wallis test.

RESULTS

Eight circulating microRNAs resulted differentially expressed after 2 weeks of anti-HER2 therapy between patients experiencing or not a cardiac event. Specifically, the expression of miR-125b-5p, miR-409-3p, miR-15a-5p, miR-423-5p, miR-148a-3p, miR-99a-5p, and miR-320b increased in plasma of cases as compared to controls, while the expression of miR-642a-5p decreases. Functional enrichment analysis revealed that all these microRNAs were involved in cardiomyocyte adrenergic signaling pathway.

CONCLUSION

This study provides proof of concept that circulating microRNAs tested soon after treatment start could serve as biomarkers of cardiotoxicity in a very early stage in breast cancer patients receiving anti-HER2 therapy.

Genetic Loss of miR-205 Causes Increased Mammary Gland Development

MiRNAs play crucial roles in a broad spectrum of biological processes, both physiological and pathological. Different reports implicate miR-205 in the control of breast stem cell properties. Differential miR-205 expression has been observed in different stages of mammary gland development and maturation. However, a functional role in this process has not been clearly demonstrated. We generated an miR-205 knockout in the FVB/N mouse strain, which is viable and characterized by enhanced mammary gland development. Indeed, mammary glands of miR-205-/- female mice at different ages (1.5 and 5.5 months) show increased outgrowth and branching. This evidence is consistent with our previously reported data demonstrating the direct miR-205-mediated targeting of HER3, a master regulator of mammary gland development, and the oncosuppressive activity of this microRNA in different types of breast cancer.

End-of-neoadjuvant treatment circulating microRNAs and HER2-positive breast cancer patient prognosis: An exploratory analysis from NeoALTTO

Background

The absence of breast cancer cells in surgical specimens, i.e., pathological complete response (pCR), is widely recognized as a favorable prognostic factor after neoadjuvant therapy. In contrast, the presence of disease at surgery characterizes a prognostically heterogeneous group of patients. Here, we challenged circulating microRNAs (miRNAs) at the end of neoadjuvant therapy as potential prognostic biomarkers in the NeoALTTO study.

Methods

Patients treated within the trastuzumab arm (i.e., pre-operative weekly trastuzumab for 6 weeks followed by the addition of weekly paclitaxel for 12 weeks; post-operative FEC for 3 cycles followed by trastuzumab up to complete 1 year of treatment) were randomized into a training (n= 54) and testing (n= 72) set. RT-PCR-based high-throughput miRNA profile was performed on plasma samples collected at the end of neoadjuvant treatment of both sets. After normalization, circulating miRNAs associated with event free survival (EFS) were identified by univariate and multivariate Cox regression model.

Results

Starting from 23 circulating miRNAs associated with EFS in the training set, we generated a 3-circulating miRNA prognostic signature consisting of miR-185-5p, miR-146a-5p, miR-22-3p, which was confirmed in the testing set. The 3-circulating miRNA signature showed a C-statistic of 0.62 (95% confidence interval [95%CI] 0.53-0.71) in the entire study cohort. By resorting to a multivariate Cox regression model we found a statistical significant interaction between the expression values of miR-194-5p and pCR status (p.interaction =0.005) with an estimate Hazard Ratio (HR) of 1.83 (95%CI 1.14- 2.95) in patients with pCR, and 0.87 (95%CI 0.69-1.10) in those without pCR. Notably, the model including this interaction along with the abovementioned 3-circulating miRNA signature provided the highest discriminatory capability with a C-statistic of 0.67 (95%CI 0.58-0.76).

Conclusions

Circulating miRNAs are informative to identify patients with different prognosis among those with heterogeneous response after trastuzumab-based neoadjuvant treatment, and may be an exploitable tool to select candidates for salvage adjuvant therapy.

Abstract 1229: miRNA and response to trastuzumab

The implementation of trastuzumab has revolutionized the clinical management of HER2 positive breast cancers. Unfortunately, 50% of patients are resistant to the treatment. Researchers have already designed alternative anti-HER2 agents, such as pertuzumab and lapatinib. Still, predicting which patients will benefit from the therapy would prevent overtreatment and avoid unnecessary risks of side effects. MiRNAs are small non-coding RNAs involved in post-transcriptional gene regulation, and participate in almost all biological processes, including cancer. Since aberrant miRNA levels can be detected both at tissue level and in the circulation, they are good candidates as predictive and prognostic biomarkers. This study had access to tumor tissue samples from the phase III NeoALTTO trial, aimed at evaluating the efficacy of a HER2 dual blockade with trastuzumab and Lapatinib vs single blocking, in concomitance with chemotherapy, in a pre-operative setting. The primary end-point of the study was pathologic complete response (pCR); the secondary end-point event-free survival (EFS). Focusing on the trastuzumab arm, we identified both a predictive signature (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) with an AUC value of 0.73 (95%CI: 0.60-0.87), and a prognostic signature (miR-153-3p, HR 1.83, 95%CI: 1.34-2.50 and miR-219a-5p, HR 0.629, 95%CI: 0.51-0.79) leading to a C-statistics of 0.730 (95%CI: 0.63-0.83). Moreover, we identified 2 miRNAs (miR-215-5p and miR-30c-2-3p) associated to EFS with a statistically significant interaction term with pCR (p.interaction: 0.017 and 0.038, respectively). Aiming at deepening the understanding of resistance mechanism, we modulated the expression of miR-31-3p and miR-382-3p in vitro, upon trastuzumab treatment in HER2 positive breast cancer cell lines. Given that miR-31-3p negatively correlates with pCR, we transfected it in HER2-addicted SKBr3 cells to appreciate a possible gain of resistance to trastuzumab; conversely, miR-382-3p positively correlates with pCR and was transfected in HER2 non-addicted HCC1954 cells. Western blot analysis of HER2 signaling pathway highlighted that overexpression of miR-31-3p was able to counteract the reduction of phosphorylated HER2 levels induced by trastuzumab treatment in SKBR3 cells compared to control. Interestingly, miR-31-3p upmodulation increased the proliferation of both treated and non-treated SKBr3 cell in a 3D setting. Conversely, miR-382-3p overexpression in HCC1954 cells only slightly increased responsiveness to trastuzumab in the 3D setting, compared to control. Trastuzumab efficacy also relies on the immune system reaction, thus, in vivo experiments will likely provide further insights into the mechanism of action of these miRNAs.

Citation Format: Giulia Cosentino, Sara Pizzamiglio, Chiara M. Ciniselli, Loris De Cecco, Alessandra Cataldo, Ilaria Plantamura, Tiziana Triulzi, Sarra El-abed, Yingbo Wang, Mohammed Bajji, Paolo Nuciforo, Jens Huober, Susan L. Ellard, David L. Rimm, Andrea Gombos, Mariagrazia Daidone, Paolo Verderio, Elda Tagliabue, Serena Di Cosimo, Marilena V. Iorio. miRNA and response to trastuzumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1229.

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.

Early Modulation of Circulating MicroRNAs Levels in HER2-Positive Breast Cancer Patients Treated with Trastuzumab-Based Neoadjuvant Therapy

Circulating microRNA (ct-miRNAs) are able to identify patients with differential response to HER2-targeted therapy. However, their dynamics are largely unknown. We assessed 752 miRNAs from 52 NeoALTTO patients with plasma pairs prior and two weeks after trastuzumab. Increased levels of ct-miR-148a-3p and ct-miR-374a-5p were significantly associated with pathological complete response (pCR) (p = 0.008 and 0.048, respectively). At a threshold ≥ the upper limit of the 95%CI of the mean difference, pCR resulted 45% (95%CI 24%–68%), and 44% (95%CI 22%–69%) for ct-miR-148a-3p and ct-miR-374a-5p, respectively. Notably, ct-miR-148a-3p retained its predictive value (OR 3.42, 95%CI 1.23–9.46, p = 0.018) in bivariate analysis along with estrogen receptor status. Combined information from ct-miR-148a-3p and ct-miR140-5p, which we previously reported to identify trastuzumab-responsive patients, resulted in greater predictive capability over each other, with pCR of 54% (95%CI 25%–81%) and 0% (95%CI 0%–31%) in ct-miR-148a/ct-miR-140-5p high/present and low/absent, respectively. GO and KEGG analyses showed common enriched terms between the targets of these ct-miRNAs, including cell metabolism regulation, AMPK and MAPK signaling, and HCC progression. In conclusion, early modulated ct-miR-148-3p may inform on the functional processes underlying treatment response, integrate the information from already available predictive biomarkers, and identify patients likely to respond to single agent trastuzumab-based neoadjuvant therapy.

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.

Plasma miRNA Levels for Predicting Therapeutic Response to Neoadjuvant Treatment in HER2-positive Breast Cancer: Results from the NeoALTTO Trial

PURPOSE

To investigate the potential of circulating-miRNAs (ct-miRNA) as noninvasive biomarkers to predict the efficacy of single/dual HER2-targeted therapy in the NeoALTTO study.

EXPERIMENTAL DESIGN

Patients with plasma samples at baseline (T0) and/or after 2 weeks (T1) of treatment were randomized into training (n = 183) and testing (n = 246) sets. RT-PCR-based high-throughput miRNA profiling was employed in the training set. After normalization, ct-miRNAs associated with pathologic complete response (pCR) were identified by univariate analysis. Multivariate logistic regression models were implemented to generate treatment-specific signatures at T0 and T1, which were evaluated by RT-PCR in the testing set. Event-free survival (EFS) according to ct-miRNA signatures was estimated by Kaplan-Meier method and Cox regression model.

RESULTS

In the training set, starting from 51 ct-miRNAs associated with pCR, six signatures with statistically significant predictive capability in terms of area under the ROC curve (AUC) were identified. Four signatures were confirmed in the testing set: lapatinib at T0 and T1 [AUC 0.86; 95% confidence interval (CI), 0.73-0.98 and 0.71 (0.55-0.86)], respectively; trastuzumab at T1 (0.81; 0.70-0.92); lapatinib + trastuzumab at T1 (0.67; 0.51-0.83). These signatures were confirmed predictive after adjusting for known variables, including estrogen receptor status. ct-miRNA signatures failed to correlate with EFS. However, the levels of ct-miR-140-5p, included in the trastuzumab signature, were associated with EFS (HR 0.43; 95% CI, 0.22-0.84).

CONCLUSIONS

ct-miRNAs discriminate patients with and without pCR after neoadjuvant lapatinib- and/or trastuzumab-based therapy. ct-miRNAs at week two could be valuable to identify patients responsive to trastuzumab, to avoid unnecessary combination with other anti-HER2 agents, and finally to assist deescalating treatment strategies.

Expression of long non-coding RNA ENSG00000226738 (LncKLHDC7B) is enriched in the immunomodulatory triple-negative breast cancer subtype and its alteration promotes cell migration, invasion, and resistance to cell death

Triple negative breast cancer (TNBC) represents an aggressive phenotype with poor prognosis compared with ER, PR, and HER2‐positive tumors. TNBC is a heterogeneous disease, and gene expression analysis has identified seven molecular subtypes. Accumulating evidence demonstrates that long non‐coding RNA (lncRNA) are involved in regulation of gene expression and cancer biology, contributing to essential cancer cell functions. In this study, we analyzed the expression profile of lncRNA in TNBC subtypes from 156 TNBC samples, and then characterized the functional role of LncKLHDC7B (ENSG00000226738). A total of 710 lncRNA were found to be differentially expressed between TNBC subtypes, and a subset of these altered lncRNA were independently validated. We discovered that LncKLHDC7B (ENSG00000226738) acts as a transcriptional modulator of its neighboring coding gene KLHDC7B in the immunomodulatory subtype. Furthermore, LncKLHDC7B knockdown enhanced migration and invasion, and promoted resistance to cellular death. Our findings confirmed the contribution of LncKLHDC7B to induction of apoptosis and inhibition of cell migration and invasion, suggesting that TNBC tumors with enrichment of LncKLHDC7B may exhibit distinct regulatory activity, or that this may be a generalized process in breast cancer. Additionally, in silico analysis confirmed for the first time that the low expression of KLHDC7B and LncKLHDC7B is associated with poor prognosis in patients with 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.

MiR-205 as predictive biomarker and adjuvant therapeutic tool in combination with trastuzumab

Trastuzumab is the standard treatment for HER2+ breast cancer (BC) patients, and even though it significantly improved their clinical outcome, 50% of them do not benefit from this drug and disease recurs, underlining the need of reliable predictive biomarkers and new therapeutic strategies. Strikingly, despite all the molecular analyses performed to identify the escape mechanisms behind this resistance, it still represents a question point. MiRNAs have been correlated with occurrence and progression of human cancer, and their potential as clinical tools has emerged in the last years. We previously reported that oncosuppressive miR-205 targets HER3, thus increasing the responsiveness to TKIs lapatinib and gefitinib in preclinical models.

Here we demonstrate that HER3 inhibition by miR-205 ectopic expression or siRNA-mediated silencing improves the responsiveness to Trastuzumab in vitro in HER2+ BC cell lines, and that this effect is exerted through impairment of AKT-mediated pathway. Moreover, evaluating a series of 52 HER2+ BC patients treated with adjuvant Trastuzumab, we observed that higher miR-205 expression is significantly associated with better outcome (disease-free survival).

In summary, our data indicate that miR-205 could predict Trastuzumab efficacy and that its modulation might be useful as adjuvant treatment to improve the response to the drug.

Abstract 5437: miR-302b as adjuvant therapeutic tool to improve chemotherapy efficacy in human triple-negative breast cancer

Introduction: Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer cases, with the worst outcome of all subtypes. For TNBC, still lacking targeted therapies, the only therapeutic option is currently chemotherapy, and despite a good initial response, patients often develop drug resistance. MiRNAs can modulate chemoresistance by affecting DNA repair, cell cycle progression, apoptosis and also tumor microenvironment. Macrophages constitute a major component of the immune microenvironment of cancer and pro-tumor M2 macrophages have been associated with resistance to chemotherapeutic treatments. Our previous data showed that miR-302b over-expression enhances sensitivity to cisplatin in breast cancer cell lines by targeting directly E2F1 and indirectly ATM.

Here, we investigated the potential of miR-302b as a therapeutic tool to enhance cisplatin response in a TNBC mouse model and which pathways are involved in this mechanism both in tumor cells and microenvironment. Moreover, miR-302b prognostic value was assessed in a cohort of TNBC patients with available clinical outcome . Finally, we evaluated if miR-302b enhances the sensitivity to doxorubicin, another chemotherapeutic agent used as first-line therapy in TNBC patients.

Material and method: MDA-MB-231 TNBC cells were injected into the mammary fat pad of female SCID mice and then treated with lipid nanoparticles containing miR-302b or cel-miR-67 control, alone or in combination with cisplatin. Gene expression profile on collected tumors was performed by microarray and tumor sections were stained with anti-arginase 1 (M2 marker) to evaluate the number of M2 macrophages. MiR-302b expression was assessed in 39 TNBC treated with chemotherapy in adjuvant setting, and associated with prognosis. Finally, MDA-MB-231 cells were transfected with miR-302b precursor or control treated with doxorubicin for 24h and then assessed for cell viability.

Results: Our results show that miR-302b combination with cisplatin significantly impaired tumor growth in comparison with cel-67 control and cisplatin (p= 0.03), and reduced the number of M2 macrophages in the tumor microenvironment (p=0.005). Moreover, gene expression profile of collected tumors confirm immune system modulation.

Notably, miR-302b expression was associated with disease-free survival and overall survival in TNBC patients treated with adjuvant chemotherapy. Furthermore, we found that miR-302b also enhances sensitivity to doxorubicin in vitro, affecting cell viability and cell cycle transition through E2F1 regulation.

Conclusion: Our data demonstrate that miR-302b can be exploited as a new therapeutic tool to improve the response to chemotherapy, modulating tumor microenvironment. Moreover, this miRNA has prognostic significance in TNBC patients, and might also represent an useful predictive biomarker for response to chemotherapy.

Citation Format: Alessandra Cataldo, Ilaria Plantamura, Elvira D'Ippolito, Sandra Romero-Cordoba, Sara Baroni, Valeria Cancilia, Claudio Tripodo, Dario Palmieri, Marilena V. Iorio. miR-302b as adjuvant therapeutic tool to improve chemotherapy efficacy in human triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5437. doi:10.1158/1538-7445.AM2017-5437

miR-302b enhances breast cancer cell sensitivity to cisplatin by regulating E2F1 and the cellular DNA damage response

The identification of the molecular mechanisms involved in the establishment of the resistant phenotype represents a critical need for the development of new strategies to prevent or overcome cancer resistance to anti-neoplastic treatments.Breast cancer is the leading cause of cancer-related deaths in women, and resistance to chemotherapy negatively affects patient outcomes. Here, we investigated the potential role of miR-302b in the modulation of breast cancer cell resistance to cisplatin.miR-302b overexpression enhances sensitivity to cisplatin in breast cancer cell lines, reducing cell viability and proliferation in response to the treatment. We also identified E2F1, a master regulator of the G1/S transition, as a direct target gene of miR-302b. E2F1 transcriptionally activates ATM, the main cellular sensor of DNA damage. Through the negative regulation of E2F1, miR-302b indirectly affects ATM expression, abrogating cell-cycle progression upon cisplatin treatment. Moreover miR-302b, impairs the ability of breast cancer cells to repair damaged DNA, enhancing apoptosis activation following cisplatin treatment.These findings indicate that miR-302b plays a relevant role in breast cancer cell response to cisplatin through the modulation of the E2F1/ATM axis, representing a valid candidate as therapeutic tool to overcome chemotherapy resistance.

miR-9 and miR-200 Regulate PDGFRβ-Mediated Endothelial Differentiation of Tumor Cells in Triple-Negative Breast Cancer

Organization of cancer cells into endothelial-like cell-lined structures to support neovascularization and to fuel solid tumors is a hallmark of progression and poor outcome. In triple-negative breast cancer (TNBC), PDGFRβ has been identified as a key player of this process and is considered a promising target for breast cancer therapy. Thus, we aimed at investigating the role of miRNAs as a therapeutic approach to inhibit PDGFRβ-mediated vasculogenic properties of TNBC, focusing on miR-9 and miR-200. In MDA-MB-231 and MDA-MB-157 TNBC cell lines, miR-9 and miR-200 promoted and inhibited, respectively, the formation of vascular-like structures in vitro Induction of endogenous miR-9 expression, upon ligand-dependent stimulation of PDGFRβ signaling, promoted significant vascular sprouting of TNBC cells, in part, by direct repression of STARD13. Conversely, ectopic expression of miR-200 inhibited this sprouting by indirectly reducing the protein levels of PDGFRβ through the direct suppression of ZEB1. Notably, in vivo miR-9 inhibition or miR-200c restoration, through either the generation of MDA-MB-231-stable clones or peritumoral delivery in MDA-MB-231 xenografted mice, strongly decreased the number of vascular lacunae. Finally, IHC and immunofluorescence analyses in TNBC specimens indicated that PDGFRβ expression marked tumor cells engaged in vascular lacunae. In conclusion, our results demonstrate that miR-9 and miR-200 play opposite roles in the regulation of the vasculogenic ability of TNBC, acting as facilitator and suppressor of PDGFRβ, respectively. Moreover, our data support the possibility to therapeutically exploit miR-9 and miR-200 to inhibit the process of vascular lacunae formation in TNBC. Cancer Res; 76(18); 5562-72. ©2016 AACR.

Abstract 5207: miR-491 and miR-218: Two possible tools to reduce FOXP3 expression in breast carcinomas

The Forkhead box P3 (FOXP3) gene is a member of the forkhead/winged-helix family of transcription factors implicated in the regulation of immune system development and function. However, FOXP3 is also expressed in human epithelial cancers, where it has been reported to be associated with poor prognosis and in particular with metastasis. Aim of our work is to identify microRNAs able to regulate FOXP3 expression in breast tumors.

To discover microRNAs able to regulate FOXP3 expression in breast cancer cells, an in silico analysis has been performed. Among microRNAs harboring FOXP3 seed regions, we focused our attention on miR-218 and miR-491, described to have oncosuppressive properties. Indeed, it has been reported that miR-218 expression stimulates activation of tumor suppressor genes and miR-491 expression inversely correlates with migratory potential in HCC cell lines and in vivo with metastatic potential.

We therefore evaluated the ability of these microRNAs to act as oncosuppressors by targeting FOXP3 in a breast cancer model. After transient co-transfection either of miR-218 or miR-491 with FOXP3 in MDA-MB-231 cells, a significant decrease in FOXP3 expression at protein level by WB was found.

To perform functional studies both in vitro and in vivo, we generated a breast cancer cell model by stable transfection of MDA-MB-231 with inducible Tet-off plasmid encoding for FOXP3 encompassing 3′UTR region, thus maintaining microRNA-mediated regulation. We demonstrated that FOXP3 expressing clones display an increased migration capacity as compared with their respective non-induced cells. Also in these stable clones a reduction of FOXP3 expression after transfection of miR-491 and miR-218 has been demonstrated by WB. Moreover, FOXP3 was confirmed to be a direct target of both microRNAs by luciferase reporter assay.

We also found an inverse correlation between miR-491 levels and FOXP3 expression in human breast carcinoma specimens.

Overall, these preliminary results demonstrate that microRNAs can regulate FOXP3 expression, and encourage to further investigate the biological and functional consequences of this targeting, and to exploit microRNAs as a potential therapeutic tool for FOXP3 expressing breast carcinomas.

Citation Format: Martina Di Modica, Tiziana Triulzi, Viola Regondi, Marilena V. Iorio, Andrea Balsari, Elda Tagliabue, Patrizia Casalini. miR-491 and miR-218: Two possible tools to reduce FOXP3 expression in breast carcinomas. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5207. doi:10.1158/1538-7445.AM2014-5207

Abstract 530: MicroRNA expression profiling in MMTV-neu breast cancer mouse model

In addition to mRNA gene expression profiling, miRNA expression analyses of human breast cancers have further demonstrated another layer of the molecular diversity of this disease and may potentially be a useful diagnostic and prognostic tool for breast cancer therapy and treatment. The development and use of relevant mouse models that closely reflect genetic alterations found in human breast cancers is critical to understand malignant progression in this disease and to test developmental therapeutics. The Mammary Tumour Virus (MMTV) Long Terminal Repeat (LTR) promoter-driven HER2/neu transgenic mouse model was developed to directly assess the effects of mammary gland specific expression of the neu protooncogene.

Global miRNA expression profiling was performed on tumours derived from the MMTV-HER2/neu model. Normal mammary glands from FVB wild-type mice, HER2 overexpressing mammary glands from MMTV-HER2/neu transgenic mice and tumours derived from this model at different stages of the tumourigenic process were collected and microRNA expression profiling performed on them by Nanostring analysis. Differential expression of selected miRNAs, obtained by Nanostring screening, was further confirmed by quantitative Real Time analysis.

By analyzing global miRNA expression profile on tissues collected from MMTV-HER2/neu mice at different stages of the tumourigenesis, we identified significant differences in miRNA expression patterns between tumours and normal mammary tissue and between non-metastatic and metastatic tumours. miRNA expression characterization of tumours at various stages of development along with gene expression in mouse models would profoundly enhance our knowledge of progressive genetic changes associated with oncogene-induced events in breast cancer.

Citation Format: Claudia Piovan, Gianpiero Di Leva, Douglas Cheung, Matteo Fassan, Arpan Kumar, Dario Palmieri, Marilena V. Iorio, Carlo M. Croce. MicroRNA expression profiling in MMTV-neu breast cancer mouse model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 530. doi:10.1158/1538-7445.AM2014-530

PDGFRβ and FGFR2 mediate endothelial cell differentiation capability of triple negative breast carcinoma cells

Triple negative breast cancer (TNBC) is a very aggressive subgroup of breast carcinoma, still lacking specific markers for an effective targeted therapy and with a poorer prognosis compared to other breast cancer subtypes. In this study we investigated the possibility that TNBC cells contribute to the establishment of tumor vascular network by the process known as vasculogenic mimicry, through endothelial cell differentiation. Vascular-like functional properties of breast cancer cell lines were investigated in vitro by tube formation assay and in vivo by confocal microscopy, immunofluorescence or immunohistochemistry on frozen tumor sections. TNBCs express endothelial markers and acquire the ability to form vascular-like channels in vitro and in vivo, both in xenograft models and in human specimens, generating blood lacunae surrounded by tumor cells. Notably this feature is significantly associated with reduced disease free survival. The impairment of the main pathways involved in vessel formation, by treatment with inhibitors (i.e. Sunitinib and Bevacizumab) or by siRNA-mediating silencing, allowed the identification of PDGFRβ and FGFR2 as relevant players in this phenomenon. Inhibition of these tyrosine kinase receptors negatively affects vascular lacunae formation and significantly inhibits TNBC growth in vivo. In summary, we demonstrated that TNBCs have the ability to form vascular-like channels in vitro and to generate blood lacunae lined by tumor cells in vivo. Moreover, this feature is associated with poor outcome, probably contributing to the aggressiveness of this breast cancer subgroup. Finally, PDGFRβ and FGFR2-mediated pathways, identified as relevant in mediating this characteristic, potentially represent valid targets for a specific therapy of this breast cancer subgroup.

Abstract P4-07-18: PDGFRbeta-induced miR-9 is up-regulated in triple negative breast cancer

miR-9 has been described as an oncogenic microRNA associated to a metastatic phenotype and able to induce EMT (epithelial-to-mesenchymal transition) through direct targeting of E-cadherin. However, data available concerning the expression and the role of this microRNA in different subgroups of breast cancer are still not exhaustive.

Evaluating miR-9 expression by Real-Time PCR in a series of 92 breast cancer specimens (35 luminal, 36 HER2, 21 triple negative), we found that this microRNA is increasingly higher in HER2 and Triple Negative versus ER positive patients (fold change 3 and 8 respectively).

Moreover, preliminary analysis of miR-9 expression in correlation with bio-pathological features and clinical data also indicates a trend in association with disease progression.

Triple Negative Breast Cancers represent a very aggressive breast cancer subgroup, still lacking specific markers for an effective targeted therapy; we investigated whether miR-9 might play a role in the biology of this tumor subtype. Preliminary data indicate that miR-9 is activated downstream PDGFRbeta, which represents a crucial player in the aggressive phenotype of Triple Negative Breast Cancer.

In summary, here we show that miR-9 is significantly upregulated in triple negative breast cancer in comparison with other breast cancer subgroups and is activated downstream PDGFRbeta.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-07-18.

MicroRNAs and triple negative breast cancer

Triple Negative Breast Cancer (TNBC) is a very aggressive tumor subtype, which still lacks specific markers for an effective targeted therapy. Despite the common feature of negativity for the three most relevant receptors (ER, PgR and HER2), TNBC is a very heterogeneous disease where different subgroups can be recognized, and both gene and microRNA profiling studies have recently been carried out to dissect the different molecular entities. Moreover, several microRNAs playing a crucial role in triple negative breast cancer biology have been identified, providing the experimental basis for a possible therapeutic application. Indeed, the causal involvement of microRNAs in breast cancer and the possible use of these small noncoding RNA molecules as biomarkers has been extensively studied with promising results. Their application as therapeutic tools might represent an innovative approach, especially for a tumor subgroup still lacking an efficient and specific therapy such as TNBC. In this review, we summarize our knowledge on the most important microRNAs described in TNBC.

Estrogen mediated-activation of miR-191/425 cluster modulates tumorigenicity of breast cancer cells depending on estrogen receptor status

MicroRNAs (miRNAs), single-stranded non-coding RNAs, influence myriad biological processes that can contribute to cancer. Although tumor-suppressive and oncogenic functions have been characterized for some miRNAs, the majority of microRNAs have not been investigated for their ability to promote and modulate tumorigenesis. Here, we established that the miR-191/425 cluster is transcriptionally dependent on the host gene, DALRD3, and that the hormone 17β-estradiol (estrogen or E2) controls expression of both miR-191/425 and DALRD3. MiR-191/425 locus characterization revealed that the recruitment of estrogen receptor α (ERα) to the regulatory region of the miR-191/425-DALRD3 unit resulted in the accumulation of miR-191 and miR-425 and subsequent decrease in DALRD3 expression levels. We demonstrated that miR-191 protects ERα positive breast cancer cells from hormone starvation-induced apoptosis through the suppression of tumor-suppressor EGR1. Furthermore, enforced expression of the miR-191/425 cluster in aggressive breast cancer cells altered global gene expression profiles and enabled us to identify important tumor promoting genes, including SATB1, CCND2, and FSCN1, as targets of miR-191 and miR-425. Finally, in vitro and in vivo experiments demonstrated that miR-191 and miR-425 reduced proliferation, impaired tumorigenesis and metastasis, and increased expression of epithelial markers in aggressive breast cancer cells. Our data provide compelling evidence for the transcriptional regulation of the miR-191/425 cluster and for its context-specific biological determinants in breast cancers. Importantly, we demonstrated that the miR-191/425 cluster, by reducing the expression of an extensive network of genes, has a fundamental impact on cancer initiation and progression of breast cancer cells.

MicroRNAs are small noncoding RNAs that act as posttranscriptional repressors of gene expression. A pivotal role for miRNAs in all the molecular processes driving initiation and progression of various malignancies, including breast cancer, has been described. Divergent miRNA expression between normal and neoplastic breast tissues has been demonstrated, as well as differential miRNA expression among the molecular subtypes of breast cancer. Over half of all breast cancers overexpress ERα, and several studies have shown that miRNA expression is controlled by ERα. We assessed the global change in microRNA expression after estrogen starvation and stimulation in breast cancer cells and identified that miR-191/425 and the host gene DALRD3 are positively associated to ERα-positive tumors. We demonstrated that ERα regulates the miR-191/425 cluster and verified the existence of a transcriptional network that allows a dual effect of estrogen on miR-191/425 and their host gene. We show that estrogen induction of miR-191/425 supports in vitro and in vivo the estrogen-dependent proliferation of ERα positive breast cancer cells. On the contrary, miR-191/425 cluster reprograms gene expression to impair tumorigenicity and metastatic potential of highly aggressive ERα negative breast cancer cells.

Increased sensitivity to chemotherapy induced by CpG-ODN treatment is mediated by microRNA modulation

We recently reported that peritumoral CpG-ODN treatment, activating TLR-9 expressing cells in tumor microenvironment, induces modulation of genes involved in DNA repair and sensitizes cancer cells to DNA-damaging cisplatin treatment. Here, we investigated whether this treatment induces modulation of miRNAs in tumor cells and their relevance to chemotherapy response. Array analysis identified 20 differentially expressed miRNAs in human IGROV-1 ovarian tumor cells from CpG-ODN-treated mice versus controls (16 down- and 4 up-regulated). Evaluation of the role of the 3 most differentially expressed miRNAs on sensitivity to cisplatin of IGROV-1 cells revealed significantly increased cisplatin cytotoxicity upon ectopic expression of hsa-miR-302b (up-modulated in our array), but no increased effect upon reduced expression of hsa-miR-424 or hsa-miR-340 (down-modulated in our array). Accordingly, hsa-miR-302b expression was significantly associated with time to relapse or overall survival in two data sets of platinum-treated ovarian cancer patients. Use of bio-informatics tools identified 19 mRNAs potentially targeted by hsa-miR-302b, including HDAC4 gene, which has been reported to mediate cisplatin sensitivity in ovarian cancer. Both HDAC4 mRNA and protein levels were significantly reduced in IGROV-1 cells overexpressing hsa-miR-302b. Altogether, these findings indicate that hsa-miR-302b acts as a “chemosensitizer” in human ovarian carcinoma cells and may represent a biomarker able to predict response to cisplatin treatment. Moreover, the identification of miRNAs that improve sensitivity to chemotherapy provides the experimental underpinning for their possible future clinical use.

Breast cancer and microRNAs: therapeutic impact

Despite advances in detection and therapies, breast cancer is still the leading cause of cancer death in women worldwide. The etiology of this neoplasm is complex, and both genetic and environmental factors contribute to the complicate scenario. Gene profiling studies have been extensively used over the last decades as a powerful tool to define the signature of different cancers and to predict outcome and response to therapies. More recently, a new class of small (19-25 nucleotides) non-coding RNAs, microRNAs (miRs or miRNAs) has been linked to several human diseases, included cancer. MicroRNAs are involved in temporal and tissue-specific eukaryotic gene regulation,(1) either by translational inhibition or exonucleolytic mRNA decay, targeted through imperfect complementarity between the microRNA and the 3' untranslated region (3'UTR) of the mRNA.(2) Since their ability to potentially target any human mRNA, it is likely that microRNAs are involved in almost every biological process, including cell cycle regulation, cell growth, apoptosis, cell differentiation and stress response.(3) The involvement of microRNAs in the biology of human cancer is supported by an increasing body of experimental evidence, that has gradually switched from profiling studies, as the first breast cancer specific signature reported in 2005 by our group(4) describing an aberrant microRNA expression in different tumor types, to biological demonstrations of the causal role of these small molecules in the tumorigenic process, and the possible implications as biomarkers or therapeutic tools.(5) These more recent studies have widely demonstrated that microRNAs can modulate oncogenic or tumor suppressor pathways, and that, at the same time, their expression can be regulated by oncogenes or tumor suppressor genes. The possibility to modulate microRNA expression both in vitro and in vivo by developing synthetic pre-microRNA molecules or antisense oligonucletides has at the same time provided a powerful tool to a deeper comprehension of the molecular mechanisms regulated by these molecules, and suggested the intriguing and promising perspective of a possible use in therapy. Here we review our current knowledge about the involvement of microRNAs in cancer, focusing particularly on breast cancer, and their potential as diagnostic, prognostic and therapeutic tools.

Oncosuppressive role of p53-induced miR-205 in triple negative breast cancer

An increasing body of evidence highlights an intriguing interaction between microRNAs and transcriptional factors involved in determining cell fate, including the well known "genome guardian" p53. Here we show that miR-205, oncosuppressive microRNA lost in breast cancer, is directly transactivated by oncosuppressor p53. Moreover, evaluating miR-205 expression in a panel of cell lines belonging to the highly aggressive triple negative breast cancer (TNBC) subtype, which still lacks an effective targeted therapy and characterized by an extremely undifferentiated and mesenchymal phenotype, we demonstrated that this microRNA is critically down-expressed compared to a normal-like cell line. Re-expression of miR-205 where absent strongly reduces cell proliferation, cell cycle progression and clonogenic potential in vitro, and inhibits tumor growth in vivo, and this tumor suppressor activity is at least partially exerted through targeting of E2F1, master regulator of cell cycle progression, and LAMC1, component of extracellular matrix involved in cell adhesion, proliferation and migration.

microRNA involvement in human cancer

When, ∼20 years ago, investigators first determined that components of the genome considered nonfunctional had, in fact, gene regulatory capacity, they probably had no idea of their potential in controlling cell fate and were forced to revise and somehow reorganize their view of the molecular biology. Indeed, it is currently well documented how a class of small non-coding RNAs, microRNAs, are conserved among the species, expressed in different tissues and cell types and involved in almost every biological process, including cell cycle, growth, apoptosis, differentiation and stress response, exerting a finely tuned regulation of gene expression by targeting multiple molecules. As a consequence of the widespread range of processes they are able to influence, it is not surprising that miRNA deregulation is a hallmark of several pathological conditions, including cancer. Indeed, the aberrant expression of these tiny molecules in human tumors is not just a casual association, but they can exert a causal role, as oncogenes or tumor suppressors, in different steps of the tumorigenic process, from initiation and development to progression toward the acquisition of a metastatic phenotype. An increasing body of evidence has indeed proved the importance of miRNAs in cancer, suggesting their possible use as diagnostic, prognostic and predictive biomarkers and leading to exploit miRNA-based anticancer therapies, either alone or in combination with current targeted therapies, with the goal to improve disease response and increase cure rates. Here, we review our current knowledge about miRNA involvement in cancer.

MicroRNA dysregulation in cancer: diagnostics, monitoring and therapeutics. A comprehensive review

Early studies have shown how aberrantly expressed microRNAs are a hallmark of several diseases like cancer. MicroRNA expression profiling was shown to be associated with tumour development, progression and response to therapy, suggesting their possible use as diagnostic, prognostic and predictive biomarkers. Moreover, based on the increasing number of studies demonstrating that microRNAs can function as potential oncogenes or oncosuppressor genes, with the goal to improve disease response and increase cure rates, miRNA-based anticancer therapies have recently been exploited, either alone or in combination with current targeted therapies. The advantage of using microRNA approaches is based on its ability to concurrently target multiple effectors of pathways involved in cell differentiation, proliferation and survival. Here, we review our current knowledge about the involvement of microRNAs in cancer, and their potential as diagnostic, prognostic and therapeutic tools.

MicroRNA dysregulation in cancer: diagnostics, monitoring and therapeutics. A comprehensive review

Early studies have shown how aberrantly expressed microRNAs are a hallmark of several diseases like cancer. MicroRNA expression profiling was shown to be associated with tumour development, progression and response to therapy, suggesting their possible use as diagnostic, prognostic and predictive biomarkers. Moreover, based on the increasing number of studies demonstrating that microRNAs can function as potential oncogenes or oncosuppressor genes, with the goal to improve disease response and increase cure rates, miRNA-based anticancer therapies have recently been exploited, either alone or in combination with current targeted therapies. The advantage of using microRNA approaches is based on its ability to concurrently target multiple effectors of pathways involved in cell differentiation, proliferation and survival. Here, we review our current knowledge about the involvement of microRNAs in cancer, and their potential as diagnostic, prognostic and therapeutic tools.

Abstract P6-08-01: Endothelial-Like Phenotype of Triple-Negative Breast Carcinoma Cells and Implications for New Molecular Targets

Background. Triple Negative Breast Cancers (TNBCs) still represent a question mark in breast cancer biology and a primary issue in clinics. A promising approach for an efficient targeted treatment of TNBCs seems to be represented by antiangiogenic therapies.

Methods. Effects of different compounds on proliferation of TNBC was evaluated in vivo and in vitro respectively by xenograft tumor volume analysis and SRB assay. Vasculogenic Mimicry (VM) properties were evaluated in vitro and in vivo respectively by tube formation assay and Transmission Electron Microscopy (TEM).

Results. Treatment of triple negative (TN) MDA-MB-231 xenografts with Sunitinib induced tumor regression, versus only a slight growth inhibition in tumors derived from MCF7 luminal cell line, whereas Bevacizumab determined only a modest decrease in tumor growth in both models. Accordingly, the efficacy of Sunitinib in blocking in vitro growth of breast cancer cell lines was higher in MDA-MB-231 cells in comparison with MCF7 cells (IC50 at 72h in MDA-MB-231 was 5 uM vs 25 uM in MCF7, as evaluated by SRB), and sensitivity to Bevacizumab was comparable between the two different cell lines. Investigating the undifferentiated nature of TNBCs, we observed that these tumors present an endothelial like phenotype and behavior, as supported respectively by the expression of endothelial markers, and the formation of vascular-like channels in vitro. In fact, all six TN cell lines evaluated (MDA-MB-231, MDA-MB-157, MDA-MB-468, BT-549, BT-20 and HCC1937) were able to form vascular channels when seeded on the murine tumor-derived basement membrane (Matrigel), whereas luminal (MCF7, T47D and ZR-75-1) and HER2- positive (MDA-MB-361, BT474 and SKBr3) breast carcinoma cell lines did not exhibit vascular structures. Then, we evaluated the VM in xenograft tumors derived from MDA-MB-231, MCF7 and MDA-MB-361 using transmission electron microscopy (TEM). MDA-MB-231 xenografts displayed channel-like structures formed by tumor cells encompassing erytrocytes, whereas in MCF7 and MDA-MB-361 xenografts the endothelial lining delimiting blood vessels was clearly visible. Notably, blood vessels surrounded by tumor cells were also identified in human TN specimens processed for TEM, and these structures were significantly more frequent in TN compared to non-TN tumors. 60% reduction in TN vascular channel formation in vitro by an anti-bFGF monoclonal antibody along with no effect using anti-VEGF antibody indicated that TN breast carcinoma cells can generate vascular channels through bFGF-mediated pathway. Silencing of different receptors involved in bFGF signal (i.e. FGFR2 and PDGFR β) abrogated VM in TN cells. Finally, TNBC cells able to perform vascular-like channels were found to express significantly higher (p= 0.003) levels of FGFR related genes, described associated with basal-like BC aggressiveness, compared to all the other tested cell lines. Conclusions. Our findings point to the possibility that TNBC cells are maintained by proangiogenic signals and that increased sensitivity to Sunitinib probably relies on the specific impairment of PDGFRβ and FGFR2-mediated pathways, which might represent a possible specific therapeutic target. Partially supported by AIRC and Italian Bureau of Health.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-08-01.

Reprogramming of miRNA networks in cancer and leukemia

We studied miRNA profiles in 4419 human samples (3312 neoplastic, 1107 nonmalignant), corresponding to 50 normal tissues and 51 cancer types. The complexity of our database enabled us to perform a detailed analysis of microRNA (miRNA) activities. We inferred genetic networks from miRNA expression in normal tissues and cancer. We also built, for the first time, specialized miRNA networks for solid tumors and leukemias. Nonmalignant tissues and cancer networks displayed a change in hubs, the most connected miRNAs. hsa-miR-103/106 were downgraded in cancer, whereas hsa-miR-30 became most prominent. Cancer networks appeared as built from disjointed subnetworks, as opposed to normal tissues. A comparison of these nets allowed us to identify key miRNA cliques in cancer. We also investigated miRNA copy number alterations in 744 cancer samples, at a resolution of 150 kb. Members of miRNA families should be similarly deleted or amplified, since they repress the same cellular targets and are thus expected to have similar impacts on oncogenesis. We correctly identified hsa-miR-17/92 family as amplified and the hsa-miR-143/145 cluster as deleted. Other miRNAs, such as hsa-miR-30 and hsa-miR-204, were found to be physically altered at the DNA copy number level as well. By combining differential expression, genetic networks, and DNA copy number alterations, we confirmed, or discovered, miRNAs with comprehensive roles in cancer. Finally, we experimentally validated the miRNA network with acute lymphocytic leukemia originated in Mir155 transgenic mice. Most of miRNAs deregulated in these transgenic mice were located close to hsa-miR-155 in the cancer network.

Interplay between microRNAs and the epigenetic machinery: an intricate network

microRNAs take their place into the epigenetic world revealing a complicated network of reciprocal interconnections: not only they are able to control gene expression at a post-transcriptional level, thus representing a new important class of regulatory molecules, but they are also directly connected to the epigenetic machinery through a regulatory loop. Indeed, if epigenetic modifications, such as DNA methylation or histone acetylation, have been demonstrated to affect microRNA expression, and to be potentially responsible for the aberrant miRNA regulation observed in cancer, the other side of the coin is represented by the capacity of microRNAs to control the epigenetic machinery directly targeting its enzymatic components. This review will analyze and describe the regulatory loop interconnecting microRNAs and epigenetics, describing either how epigenetics can affect the miRNome, as well as how epi-miRNAs can control the epigenome, particularly focusing on the alterations observed in human cancer.

Abstract 2089: MiR-205 role in triple negative breast cancer

An increasing number of experimental evidences show that microRNAs can have a causal role in breast cancer tumorigenesis as a novel class of oncogenes or tumor suppressor genes, depending on the targets they regulate. miR-205, down-modulated in breast cancer versus normal breast tissue, was originally associated to absence of vascular invasion and shown to be involved in the EMT. Moreover, we recently demonstrated that miR-205 directly targets HER3 receptor and impairs the Akt-mediated survival pathway, thus inhibiting clonogenic potential of SKBr3 cells and increasing the responsiveness to tyrosin-kinase inhibitors.

Considering the striking evidences of a major role of miR-205 as oncosuppressor in breast cancer, we decided to investigate its possible involvement in another tumor subgroup, extremely aggressive and still lacking a specific therapy: triple negative breast tumors. Here we show that re-introduction of miR-205 in the triple negative breast cancer cell line MDA-MB-231 led to a dramatic reduction of both proliferation and clonogenic potential as well as migration capability. Notably, miR-205 also significantly inhibited the in vivo growth in xenograft models obtained injecting stable clones of MDA-MB-231 cells transfected with a miR-205-encoding plasmid or the empty vector.

Investigating alternative pathways potentially regulated by miR-205 in this model, we noticed that many of the predicted targets are actually interconnected and related to adhesion and migration processes. Indeed, this microRNA seems to be involved in the control of cell-cell and cell-matrix adhesion regulating the expression of extracellular matrix-related molecules. Among them, we focused on LAMC1, reported to be involved in cell adhesion, differentiation, migration, signaling and metastasis. By Western Blot and Luciferase assay, we demonstrated that miR-205 directly targets LAMC1 in MDA-MB-231 cells.

In conclusion, miR-205 exerts a role as oncosuppressor gene also in triple negative breast cancer: it exerts a dramatic inhibition of proliferation and migration in triple negative MDA-MB-231 cell line, at least partially through direct regulation of LAMC1. These evidences not only underline the consistent role of miR-205 in the biology of different breast cancer subgroups, but provide the rational bases for a therapeutic intervention miRs-based.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2089.

Abstract 1598: Vasculogenic properties of triple negative breast carcinoma cells: possible implication for new molecular target

Triple negative (TN) breast cancers account for about 15-20% of breast cancers and are associated with aggressiveness, poor prognosis and shorter survival.

Because of the lack of specific therapy guidelines for this subgroup there is an urgent need to define specific markers for therapeutic targeting in these tumors.

We observed that TN breast cancer cells lines are able to perform “Vasculogenic Mimicry” (VM) in vitro. In fact, all four TN cell lines evaluated (MDA-MB-231, MDA-MB-157, MDA-MB-468 and HCC1937) were able to form vascular channels when seeded on the murine tumor-derived basement membrane (Matrigel), whereas luminal (MCF7 and ZR-75-1) and HER2-positive (MDA-MB-361 and SKBr3) breast carcinoma cell lines did not exhibit vascular structures. Then, we evaluated the VM in xenograft tumors derived from MDA-MB-231, MCF7 and MDA-MB-361 using transmission electron microscopy (TEM). In MDA-MB-231 xenografts it has been revealed channel-like structures formed by tumor cells encompassing erytrocytes, whereas in MCF7 and MDA-MB-361 xenografts the endothelial lining delimiting blood vessels was clearly visible. Notably, blood vessels surrounded by tumor cells were also identified in human TN specimens processed for TEM, and these structures were significantly more frequent in TN compared to non-TN tumors. 60% reduction in TN vascular channel formation in vitro by an anti-bFGF monoclonal antibody together with no effect using anti-VEGF antibody indicated that TN breast carcinoma cells can generate vascular channels through bFGF-mediated pathway. Silencing different receptors involved in bFGF signal (i.e. FGFR2 and PDFGR) abrogated VM in TN cells.

Treatment of MDA-MB-231 xenografts with a TKI able to block both FGFR and PDGFR induced tumor regression, versus only slight growth inhibition in tumors derived from MCF7 luminal cell line.

In conclusion our findings point to the possibility that TN tumors generate vascular channels independent of tumor angiogenesis and that targeting this VM capability may represent a valid therapeutic tool. (Partially supported by AIRC).

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1598.

MicroRNA cluster 221-222 and estrogen receptor alpha interactions in breast cancer

BACKGROUND

Several lines of evidence have suggested that estrogen receptor alpha (ERalpha)-negative breast tumors, which are highly aggressive and nonresponsive to hormonal therapy, arise from ERalpha-positive precursors through different molecular pathways. Because microRNAs (miRNAs) modulate gene expression, we hypothesized that they may have a role in ER-negative tumor formation.

METHODS

Gene expression profiles were used to highlight the global changes induced by miRNA modulation of ERalpha protein. miRNA transfection and luciferase assays enabled us to identify new targets of miRNA 206 (miR-206) and miRNA cluster 221-222 (miR-221-222). Northern blot, luciferase assays, estradiol treatment, and chromatin immunoprecipitation were performed to identify the miR-221-222 transcription unit and the mechanism implicated in its regulation.

RESULTS

Different global changes in gene expression were induced by overexpression of miR-221-222 and miR-206 in ER-positive cells. miR-221 and -222 increased proliferation of ERalpha-positive cells, whereas miR-206 had an inhibitory effect (mean absorbance units [AU]: miR-206: 500 AU, 95% confidence interval [CI]) = 480 to 520; miR-221: 850 AU, 95% CI = 810 to 873; miR-222: 879 AU, 95% CI = 850 to 893; P < .05). We identified hepatocyte growth factor receptor and forkhead box O3 as new targets of miR-206 and miR-221-222, respectively. We demonstrated that ERalpha negatively modulates miR-221 and -222 through the recruitment of transcriptional corepressor partners: nuclear receptor corepressor and silencing mediator of retinoic acid and thyroid hormone receptor.

CONCLUSIONS

These findings suggest that the negative regulatory loop involving miR-221-222 and ERalpha may confer proliferative advantage and migratory activity to breast cancer cells and promote the transition from ER-positive to ER-negative tumors.

MicroRNAs in cancer: small molecules with a huge impact

Every cellular process is likely to be regulated by microRNAs, and an aberrant microRNA expression signature is a hallmark of several diseases, including cancer. MicroRNA expression profiling has indeed provided evidence of the association of these tiny molecules with tumor development and progression. An increasing number of studies have then demonstrated that microRNAs can function as potential oncogenes or oncosuppressor genes, depending on the cellular context and on the target genes they regulate. Here we review our current knowledge about the involvement of microRNAs in cancer and their potential as diagnostic, prognostic, and therapeutic tools.

MicroRNAs and future therapeutic applications in cancer

Every cellular process is likely to be regulated by microRNAs (miRNAs), and an aberrant expression signature of these small non-coding RNAs is a hallmark of several diseases, including cancer. miRNA expression profiling by microarray techniques has provided a powerful tool to reveal the involvement of these tiny molecules in tumor development and progression, showing that they are differentially expressed in tumors as compared to normal tissues. Moreover, specific miRNA signatures have been associated with histopathological and clinical features, suggesting a potential role of these molecules as prognostic and predictive markers. Focusing then on their biological effects and role in cancer, it has been shown that miRNAs can function as potential oncogenes or oncosuppressor genes, depending on the cellular context and on the target genes they regulate. The possibility to modulate miRNA expression either in vitro and in vivo by developing synthetic pre-miRNA molecules or antisense oligonucleotides have at the same time provided a powerful tool to a deeper comprehension of the molecular mechanisms regulated by these molecules, and suggested the intriguing and promising perspective of their possible use in therapy. Herein we review our current knowledge about the involvement of miRNAs in cancer, and their potential as diagnostic, prognostic and therapeutic tools.

microRNA-205 regulates HER3 in human breast cancer

An increasing amount of experimental evidence shows that microRNAs can have a causal role in breast cancer tumorigenesis as a novel class of oncogenes or tumor suppressor genes, depending on the targets they regulate. HER2 overexpression is a hallmark of a particularly aggressive subset of breast tumors, and its activation is strictly dependent on the trans-interaction with other members of HER family; in particular, the activation of the PI3K/Akt survival pathway, so critically important in tumorigenesis, is predominantly driven through phosphorylation of the kinase-inactive member HER3. Here, we show that miR-205, down-modulated in breast tumors compared with normal breast tissue, directly targets HER3 receptor, and inhibits the activation of the downstream mediator Akt. The reintroduction of miR-205 in SKBr3 cells inhibits their clonogenic potential and increases the responsiveness to tyrosine-kinase inhibitors Gefitinib and Lapatinib, abrogating the HER3-mediated resistance and restoring a potent proapoptotic activity. Our data describe miR-205 as a new oncosuppressor gene in breast cancer, able to interfere with the proliferative pathway mediated by HER receptor family. Our study also provides experimental evidence suggesting that miR-205 can improve the responsiveness to specific anticancer therapies.

MicroRNA profiling as a tool to understand prognosis, therapy response and resistance in breast cancer

Despite advances in detection and therapies, breast cancer is still the leading cause of cancer death in women worldwide. The etiology of this neoplasm is complex, and both genetic and environmental factors contribute to the complicated scenario. Gene profiling studies have been extensively used over the past decades as a powerful tool in defining the signature of different cancers and in predicting outcome and response to therapies. More recently, a new class of small non-coding RNAs, microRNAs (miRNAs), able to regulate gene expression binding seed sequences on the 3'UTR of mRNA targets, has been linked to several human diseases, including cancer. An increasing amount of experimental evidence shows that miRNAs are aberrantly expressed in different tumour types, and that they can have a causal role in tumourigenesis. Here, we describe and discuss the evidence supporting the association between miRNAs and breast cancer, underlining their role in the development of this neoplasia, and the impact on putative innovative therapeutical approaches.

UCbase & miRfunc: a database of ultraconserved sequences and microRNA function

Four hundred and eighty-one ultraconserved sequences (UCRs) longer than 200 bases were discovered in the genomes of human, mouse and rat. These are DNA sequences showing 100% identity among the three species. UCRs are frequently located at genomic regions involved in cancer, differentially expressed in human leukemias and carcinomas and in some instances regulated by microRNAs (miRNAs). Here we present UCbase & miRfunc, the first database which provides ultraconserved sequences data and shows miRNA function. Also, it links UCRs and miRNAs with the related human disorders and genomic properties. The current release contains over 2000 sequences from three species (human, mouse and rat). As a web application, UCbase & miRfunc is platform independent and it is accessible at http://microrna.osu.edu/.UCbase4.

Relationship between p53 and p27 expression following HER2 signaling

HER2, frequently associated with low p27 expression in breast tumors, when activated has been found to upmodulate p53 in tumor cells. The aim of this work was to investigate the role of p53 in the connection between HER2 and p27. Fifty-two breast tumor specimens, characterized for p53 mutations, were analyzed immunohistochemically (IHC) for HER2, p53 and p27 expression. p27, inversely associated with HER2, was found in 29% of tumors with IHC-negative mutated p53 versus 93% of tumors with accumulation of p53 protein and 59% with wild-type p53 (p=0.001), indicating a direct association between p53 and p27 expression. HER2-overexpressing cell lines carrying wild-type or null p53 protein, and treated with heregulin beta1 (HRG), were analyzed for expression and subcellular localization of p53 and p27. In HER2-overexpressing cells stimulated with HRG, p27 protein expression increased in parallel with p53 with no corresponding increase in p27 transcript. No p27 increase was observed in p53-null cells. Transfection with wild-type p53 restored p27 upmodulation in HRG-stimulated cells, indicating a crucial role of p53 in determining p27 upmodulation following HER2 activation. Together, our data demonstrate the crucial role of p53 in determining p27 upmodulation following HER2 activation. This could have implications in the response to Transtuzumab therapy.

MicroRNA signatures in human ovarian cancer

Epithelial ovarian cancer (EOC) is the sixth most common cancer in women worldwide and, despite advances in detection and therapies, it still represents the most lethal gynecologic malignancy in the industrialized countries. Unfortunately, still relatively little is known about the molecular events that lead to the development of this highly aggressive disease. The relatively recent discovery of microRNAs (miRNA), a class of small noncoding RNAs targeting multiple mRNAs and triggering translation repression and/or RNA degradation, has revealed the existence of a new level of gene expression regulation. Multiple studies involving various types of human cancers proved that miRNAs have a causal role in tumorigenesis. Here we show that, in comparison to normal ovary, miRNAs are aberrantly expressed in human ovarian cancer. The overall miRNA expression could clearly separate normal versus cancer tissues. The most significantly overexpressed miRNAs were miR-200a, miR-141, miR-200c, and miR-200b, whereas miR-199a, miR-140, miR-145, and miR-125b1 were among the most down-modulated miRNAs. We could also identify miRNAs whose expression was correlated with specific ovarian cancer biopathologic features, such as histotype, lymphovascular and organ invasion, and involvement of ovarian surface. Moreover, the levels of miR-21, miR-203, and miR-205, up-modulated in ovarian carcinomas compared with normal tissues, were significantly increased after 5-aza-2'-deoxycytidine demethylating treatment of OVCAR3 cells, suggesting that the DNA hypomethylation could be the mechanism responsible for their overexpression. Our results indicate that miRNAs might play a role in the pathogenesis of human EOC and identify altered miRNA gene methylation as a possible epigenetic mechanism involved in their aberrant expression.

MicroRNA gene expression deregulation in human breast cancer

MicroRNAs (miRNAs) are a class of small noncoding RNAs that control gene expression by targeting mRNAs and triggering either translation repression or RNA degradation. Their aberrant expression may be involved in human diseases, including cancer. Indeed, miRNA aberrant expression has been previously found in human chronic lymphocytic leukemias, where miRNA signatures were associated with specific clinicobiological features. Here, we show that, compared with normal breast tissue, miRNAs are also aberrantly expressed in human breast cancer. The overall miRNA expression could clearly separate normal versus cancer tissues, with the most significantly deregulated miRNAs being mir-125b, mir-145, mir-21, and mir-155. Results were confirmed by microarray and Northern blot analyses. We could identify miRNAs whose expression was correlated with specific breast cancer biopathologic features, such as estrogen and progesterone receptor expression, tumor stage, vascular invasion, or proliferation index.

A MicroRNA signature associated with prognosis and progression in chronic lymphocytic leukemia

BACKGROUND

MicroRNA expression profiles can be used to distinguish normal B cells from malignant B cells in patients with chronic lymphocytic leukemia (CLL). We investigated whether microRNA profiles are associated with known prognostic factors in CLL.

METHODS

We evaluated the microRNA expression profiles of 94 samples of CLL cells for which the level of expression of 70-kD zeta-associated protein (ZAP-70), the mutational status of the rearranged immunoglobulin heavy-chain variable-region (IgV(H) ) gene, and the time from diagnosis to initial treatment were known. We also investigated the genomic sequence of 42 microRNA genes to identify abnormalities.

RESULTS

A unique microRNA expression signature composed of 13 genes (of 190 analyzed) differentiated cases of CLL with low levels of ZAP-70 expression from those with high levels and cases with unmutated IgV(H) from those with mutated IgV(H) . The same microRNA signature was also associated with the presence or absence of disease progression. We also identified a germ-line mutation in the miR-16-1-miR-15a primary precursor, which caused low levels of microRNA expression in vitro and in vivo and was associated with deletion of the normal allele. Germ-line or somatic mutations were found in 5 of 42 sequenced microRNAs in 11 of 75 patients with CLL, but no such mutations were found in 160 subjects without cancer (P<0.001).

CONCLUSIONS

A unique microRNA signature is associated with prognostic factors and disease progression in CLL. Mutations in microRNA transcripts are common and may have functional importance.

miR-15 and miR-16 induce apoptosis by targeting BCL2

Chronic lymphocytic leukemia (CLL) is the most common human leukemia and is characterized by predominantly nondividing malignant B cells overexpressing the antiapoptotic B cell lymphoma 2 (Bcl2) protein. miR-15a and miR-16-1 are deleted or down-regulated in the majority of CLLs. Here, we demonstrate that miR-15a and miR-16-1 expression is inversely correlated to Bcl2 expression in CLL and that both microRNAs negatively regulate Bcl2 at a posttranscriptional level. BCL2 repression by these microRNAs induces apoptopsis in a leukemic cell line model. Therefore, miR-15 and miR-16 are natural antisense Bcl2 interactors that could be used for therapy of Bcl2-overexpressing tumors.

Role of HER receptors family in development and differentiation

Members of the epidermal growth factor receptor family of receptor tyrosine kinases play a critical role in both development and oncogenesis. The latter is suggested by the frequent overexpression of HER-2, EGFR, and HER-3 in some human carcinomas, primarily breast and squamous cancer. The biological activities of the EGFR family are exerted through various ligand-receptor and receptor-receptor interactions. One receptor that plays a central role in this signaling network is HER-2/Neu, which is considered the preferred heterodimerization partner for other members of the EGFR family. The role of these receptors and their ligands in development is discussed, with particular emphasis on their ability to mediate a variety of pathways and cellular responses, including proliferation, differentiation, and apoptosis.