miRNA-based Cancer Therapeutics Research Articles

Unraveling Therapeutic Opportunities and the Diagnostic Potential of microRNAs for Human Lung Cancer.

Lung cancer is a major public health problem and a leading cause of cancer-related deaths worldwide. Despite advances in treatment options, the five-year survival rate for lung cancer patients remains low, emphasizing the urgent need for innovative diagnostic and therapeutic strategies. MicroRNAs (miRNAs) have emerged as potential biomarkers and therapeutic targets for lung cancer due to their crucial roles in regulating cell proliferation, differentiation, and apoptosis. For example, miR-34a and miR-150, once delivered to lung cancer via liposomes or nanoparticles, can inhibit tumor growth by downregulating critical cancer promoting genes. Conversely, miR-21 and miR-155, frequently overexpressed in lung cancer, are associated with increased cell proliferation, invasion, and chemotherapy resistance. In this review, we summarize the current knowledge of the roles of miRNAs in lung carcinogenesis, especially those induced by exposure to environmental pollutants, namely, arsenic and benzopyrene, which account for up to 1/10 of lung cancer cases. We then discuss the recent advances in miRNA-based cancer therapeutics and diagnostics. Such information will provide new insights into lung cancer pathogenesis and innovative diagnostic and therapeutic modalities based on miRNAs.

Applications of nanotechnologies for miRNA-based cancer therapeutics: current advances and future perspectives.

MicroRNAs (miRNAs) are short (18-25nt), non-coding, widely conserved RNA molecules responsible for regulating gene expression via sequence-specific post-transcriptional mechanisms. Since the human miRNA transcriptome regulates the expression of a number of tumor suppressors and oncogenes, its dysregulation is associated with the clinical onset of different types of cancer. Despite the fact that numerous therapeutic approaches have been designed in recent years to treat cancer, the complexity of the disease manifested by each patient has prevented the development of a highly effective disease management strategy. However, over the past decade, artificial miRNAs (i.e., anti-miRNAs and miRNA mimics) have shown promising results against various cancer types; nevertheless, their targeted delivery could be challenging. Notably, numerous reports have shown that nanotechnology-based delivery of miRNAs can greatly contribute to hindering cancer initiation and development processes, representing an innovative disease-modifying strategy against cancer. Hence, in this review, we evaluate recently developed nanotechnology-based miRNA drug delivery systems for cancer therapeutics and discuss the potential challenges and future directions, such as the promising use of plant-made nanoparticles, phytochemical-mediated modulation of miRNAs, and nanozymes.

MicroRNAs and Their Big Therapeutic Impacts: Delivery Strategies for Cancer Intervention.

Three decades have passed from the initial discovery of a microRNA (miRNA) in Caenorhabditis elegans to our current understanding that miRNAs play essential roles in regulating fundamental physiological processes and that their dysregulation can lead to many human pathologies, including cancer. In effect, restoration of miRNA expression or downregulation of aberrantly expressed miRNAs using miRNA mimics or anti-miRNA inhibitors (anti-miRs/antimiRs), respectively, continues to show therapeutic potential for the treatment of cancer. Although the manipulation of miRNA expression presents a promising therapeutic strategy for cancer treatment, it is predominantly reliant on nucleic acid-based molecules for their application, which introduces an array of hurdles, with respect to in vivo delivery. Because naked nucleic acids are quickly degraded and/or removed from the body, they require delivery vectors that can help overcome the many barriers presented upon their administration into the bloodstream. As such, in this review, we discuss the strengths and weaknesses of the current state-of-the-art delivery systems, encompassing viral- and nonviral-based systems, with a specific focus on nonviral nanotechnology-based miRNA delivery platforms, including lipid-, polymer-, inorganic-, and extracellular vesicle-based delivery strategies. Moreover, we also shed light on peptide carriers as an emerging technology that shows great promise in being a highly efficacious delivery platform for miRNA-based cancer therapeutics.

An Analysis of Mechanisms for Cellular Uptake of miRNAs to Enhance Drug Delivery and Efficacy in Cancer Chemoresistance.

Up until recently, it was believed that pharmaceutical drugs and their metabolites enter into the cell to gain access to their targets via simple diffusion across the hydrophobic lipid cellular membrane, at a rate which is based on their lipophilicity. An increasing amount of evidence indicates that the phospholipid bilayer-mediated drug diffusion is in fact negligible, and that drugs pass through cell membranes via proteinaceous membrane transporters or carriers which are normally used for the transportation of nutrients and intermediate metabolites. Drugs can be targeted to specific cells and tissues which express the relevant transporters, leading to the design of safe and efficacious treatments. Furthermore, transporter expression levels can be manipulated, systematically and in a high-throughput manner, allowing for considerable progress in determining which transporters are used by specific drugs. The ever-expanding field of miRNA therapeutics is not without its challenges, with the most notable one being the safe and effective delivery of the miRNA mimic/antagonist safely to the target cell cytoplasm for attaining the desired clinical outcome, particularly in miRNA-based cancer therapeutics, due to the poor efficiency of neo-vascular systems revolting around the tumour site, brought about by tumour-induced angiogenesis. This acquisition of resistance to several types of anticancer drugs can be as a result of an upregulation of efflux transporters expression, which eject drugs from cells, hence lowering drug efficacy, resulting in multidrug resistance. In this article, the latest available data on human microRNAs has been reviewed, together with the most recently described mechanisms for miRNA uptake in cells, for future therapeutic enhancements against cancer chemoresistance.

MiR-1293, a Candidate for miRNA-Based Cancer Therapeutics, Simultaneously Targets BRD4 and the DNA Repair Pathway.

BRD4, a member of the bromodomain and extra-terminal domain (BET) protein family, plays a role in the organization of super-enhancers and transcriptional activation of oncogenes in cancer and is recognized as a promising target for cancer therapy. microRNAs (miRNAs), endogenous small noncoding RNAs, cause mRNA degradation or inhibit protein translation of their target genes by binding to complementary sequences. miRNA mimics simultaneously targeting several tumor-promoting genes and BRD4 may be useful as therapeutic agents of tumor-suppressive miRNAs (TS-miRs) for cancer therapy. To investigate TS-miRs for the development of miRNA-based cancer therapeutics, we performed function-based screening in 10 cancer cell lines with a library containing 2,565 human miRNA mimics. Consequently, miR-1293, miR-876-3p, and miR-6571-5p were identified as TS-miRs targeting BRD4 in this screening. Notably, miR-1293 also suppressed DNA repair pathways by directly suppressing the DNA repair genes APEX1 (apurinic-apyrimidinic endonuclease 1), RPA1 (replication protein A1), and POLD4 (DNA polymerase delta 4, accessory subunit). Concurrent suppression of BRD4 and these DNA repair genes synergistically inhibited tumor cell growth invitro. Furthermore, administration of miR-1293 suppressed invivo tumor growth in a xenograft mouse model. These results suggest that miR-1293 is a candidate for the development of miRNA-based cancer therapeutics.

Abstract 4403: Development of 5-FU modified tumor suppressor miRNAs as a platform for miRNA based cancer therapeutics

Abstract Despite extensive efforts to develop effective delivery technologies for nucleic acid based therapeutic agents, it remains a challenge to deliver therapeutic miRNAs to cancer cells. We have recently developed a novel approach to modify miRNAs by replacing uracil with 5-Fluorouracil (5-FU) in the guide strand of the miRNA molecule (e.g. miR-129, miR-15a). This modification combines the power of 5-FU with tumor suppressor miRNAs to create a potent, and multi-targeted therapeutic molecule without altering the function of the native miRNA. miRNA with this modification have a number of unique features such as retaining target specificity, vehicle free delivery, enhanced potency, and stability. To demonstrate the general applicability of this approach to other tumor suppressor miRNAs, in this study, we have screened a number of miRNA mimics incorporating this modification (e.g. miR-215, miR-140, miR-200c, miR-194, let-7g, miR-502, miR-506) in several major cancer types including colon cancer, pancreatic cancer, and breast cancer. Our results show that the 5-FU modified miRNAs are more potent (low nM range) at inhibiting cancer cell proliferation than the native miRNAs. More importantly, the miRNA mimics are able to eliminate chemoresistant cancer stem like cells. These modified mimics can be delivered into cancer cells without the aid of a delivery vehicle. The modification also did not alter target specificity of the miRNAs, a critical feature of these miRNA mimics. This work demonstrates the potential of this modification to be applied to a broad spectrum of miRNAs in different cancers, and represents a significant advancement in the development of therapeutic miRNAs for cancer treatment. Citation Format: Andrew Fesler, Shixiang Guo, Zachary Ye, Matthew Godwin, Hyaizha Wang, Jingfang Ju. Development of 5-FU modified tumor suppressor miRNAs as a platform for miRNA based cancer therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4403.

Abstract LB-385: miR-3140 suppresses tumor cell growth by targeting BRD4 via its coding sequence and downregulates the BRD4-NUT fusion oncoprotein

Abstract Bromodomain Containing 4 (BRD4) mediates transcriptional elongation of the oncogene MYC by binding to acetylated histones. BRD4 has been shown to play a critical role in tumorigenesis in several cancers, and the BRD4-NUT fusion gene is a driver of NUT midline carcinoma (NMC), a rare but highly lethal cancer. microRNAs (miRNAs) are endogenous small non-coding RNAs that suppress target gene expression by binding to complementary mRNA sequences. Here, we show that miR-3140, which was identified as a novel tumor suppressive miRNA by function-based screening of a library containing 1090 miRNA mimics, directly suppressed BRD4 by binding to its coding sequence (CDS). miR-3140 concurrently downregulated BRD3 by bind to its CDS as well as CDK2 and EGFR by binding to their 3' untranslated regions. miR-3140 inhibited tumor cell growth in vitro in various cancer cell lines, including EGFR tyrosine kinase inhibitor-resistant cells. Interestingly, we found that miR-3140 downregulated the BRD4-NUT fusion protein and suppressed in vitro tumor cell growth in a NMC cell line, Ty-82 cells. Furthermore, administration of miR-3140 suppressed in vivo tumor growth in a xenograft mouse model. Our results suggest that miR-3140 is a candidate for the development of miRNA-based cancer therapeutics. Citation Format: Tomoki Muramatsu, Erina Tonouchi, Yasuyuki Gen, Hidekazu Hiramoto, Kousuke Tanimoto, Jun Inoue, Johji Inazawa. miR-3140 suppresses tumor cell growth by targeting BRD4 via its coding sequence and downregulates the BRD4-NUT fusion oncoprotein [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-385.

Abstract 4656: Development of an RNA-based cancer therapeutic targeting the let-7-LIN28 interaction

Abstract Based on the knowledge that microRNAs (miRNAs) are dysregulated in diseases such as cancer, various attempts have been explored to develop miRNA-based cancer therapeutics. Although many strategies have been used to restore the levels of therapeutically relevant microRNAs, clinical delivery of the processed or mature miRNA to cancer cells still remains a challenge. To overcome this challenge, innovative methods are being explored to increase the pools of tumor-suppressive miRNAs, such as enhancing miRNA biogenesis. This is especially true for the let-7 family of tumor-suppressive miRNAs, which has an additional layer of regulation over the canonical miRNA biogenesis pathway. In particular, the DROSHA and DICER cleavage steps are blocked when unprocessed let-7 is bound by the RNA-binding protein LIN28. LIN28 interacts specifically with unprocessed let-7 via a sequence-specific motif, GGAG, contained in most let-7 family members. Because previous attempts to restore mature let-7 levels through increasing let-7 pools have been quite successful at reducing tumor burden, identifying novel and clinically relevant ways to increase the level of this tumor-suppressive miRNA represents a critical need. In this study, we hypothesize that small-molecule inhibitors that disrupt the LIN28-let-7 interaction will lead to enhanced processing and increased levels of mature, tumor-suppressive let-7. Thus, an in vitro high-throughput fluorescence polarization screen has been conducted using His-tagged LIN28 and a Cy5 fluorophore-tagged let-7 RNA probe. The nine-nucleotide RNA probe was designed through in silico modeling to include the GGAG motif, which associates with LIN28 through the zinc knuckle domain of LIN28. Due to the size difference between unbound let-7 probe and LIN28-bound let-7 probe, a wide window of polarization values was achieved, resulting in a Z′ score of 0.61, indicating that the assay was robust to proceed with the screen. The screen was performed against 23,680 compounds, which consist of FDA-approved LOPAC and blood-brain barrier-permeable CNS library compounds. Eight compounds were identified as positive hits from the screen. These compounds are currently being characterized in secondary assays both in vitro and in cell culture. The significance of this research is that small-molecule inhibitors may provide novel therapeutic strategies to increase the pool of mature, tumor-suppressive let-7 in tumors with elevated LIN28. Citation Format: Sunghyun Myoung, Sergey Savinov, Lan Chen, Gaurav Chopra, Larisa Avramova, James Welch, Bradley Loren, David Thompson, Andrea L. Kasinski. Development of an RNA-based cancer therapeutic targeting the let-7-LIN28 interaction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4656.

MiR-3140 suppresses tumor cell growth by targeting BRD4 via its coding sequence and downregulates the BRD4-NUT fusion oncoprotein

Bromodomain Containing 4 (BRD4) mediates transcriptional elongation of the oncogene MYC by binding to acetylated histones. BRD4 has been shown to play a critical role in tumorigenesis in several cancers, and the BRD4-NUT fusion gene is a driver of NUT midline carcinoma (NMC), a rare but highly lethal cancer. microRNAs (miRNAs) are endogenous small non-coding RNAs that suppress target gene expression by binding to complementary mRNA sequences. Here, we show that miR-3140, which was identified as a novel tumor suppressive miRNA by function-based screening of a library containing 1090 miRNA mimics, directly suppressed BRD4 by binding to its coding sequence (CDS). miR-3140 concurrently downregulated BRD3 by bind to its CDS as well as CDK2 and EGFR by binding to their 3’ untranslated regions. miR-3140 inhibited tumor cell growth in vitro in various cancer cell lines, including EGFR tyrosine kinase inhibitor-resistant cells. Interestingly, we found that miR-3140 downregulated the BRD4-NUT fusion protein and suppressed in vitro tumor cell growth in a NMC cell line, Ty-82 cells. Furthermore, administration of miR-3140 suppressed in vivo tumor growth in a xenograft mouse model. Our results suggest that miR-3140 is a candidate for the development of miRNA-based cancer therapeutics.

Cancer Hallmarks and MicroRNAs: The Therapeutic Connection.

Human cancers are characterized by a number of hallmarks, including sustained proliferative signaling, evasion of growth suppressors, activated invasion and metastasis, replicative immortality, angiogenesis, resistance to cell death, and evasion of immune destruction. As microRNAs (miRNAs) are deregulated in virtually all human cancers, they show involvement in each of the cancer hallmarks as well. In this chapter, we describe the involvement of miRNAs in cancer from a cancer hallmarks and targeted therapeutics point of view. As no miRNA-based cancer therapeutics are available to date, and the only clinical trial on miRNA-based cancer therapeutics (MRX34) was terminated prematurely due to serious adverse events, we are focusing on protein-coding miRNA targets for which targeted therapeutics in oncology are already approved by the FDA. For each of the cancer hallmarks, we selected major protein-coding players and describe the miRNAs that target them.

Exploiting Nanotechnology for the Development of MicroRNA-Based Cancer Therapeutics.

MicroRNAs (miRNAs/miRs) represent a novel class of small non-coding RNAs that post-transcriptionally regulate gene expression by base pairing with complementary sequences in the 3' untranslated region (UTR) of target mRNAs. Functional studies suggest that miRNAs control almost every biological process, and their aberrant expression leads to a disease state, such as cancer. Differential expression of miRNAs in cancerous versus normal cells have generated enormous interest for the development of miRNA-based cancer cell-targeted therapeutics. Depending on the miRNA function and expression in cancer, two types of miRNA-based therapeutic strategies can be utilized that either restore or inhibit miRNA function through exogenous delivery of miRNAs mimics or inhibitors (anti-miRs). However, hydrophilic nature of miRNA mimics/anti-miRs, sensitivity to nuclease degradation in serum, poor penetration and reduced uptake by the tumor cells are chief hurdles in accomplishing their efficient in vivo delivery. To overcome these barriers, several nanotechnology-based systems are being developed and tested for delivery efficacy. This review summarizes the importance of miRNAs-based therapeutics in cancer, associated translational challenges and novel nanotechnology-assisted delivery systems that hold potential for next-generation miRNA-based cancer therapeutics.

MP36-13 DEEP SEQUENCING OF MICRORNA EXPRESSION SIGNATURE OF BLADDER CANCER: THE FUNCTIONAL SIGNIFICANCE OF MIR-145/145∗ AND ITS REGULATED MOLECULAR PATHWAYS

INTRODUCTION AND OBJECTIVES: Generally in microRNA (miRNA) biogenesis, one strand (guide strand) of the duplex may potentially act as a functional miRNA and incorporated into the RNA-induced silencing complex and regulating target genes. In contrast, other strand (passenger strand: miRNA*) is disintegrated quickly. Our miRNA expression signature of bladder cancer (BC) by using deep-sequencing revealed that tumor-suppressive miRNA-145 and its passenger strand of miRNA-145* were significantly reduced in cancer tissues, suggesting these function as tumor suppressors in BC cells. The aim of the study was to investigate functional significance of miRNA-145* and its regulated molecular targets/ pathways in BC. METHODS: We evaluated the expression levels of miR-145/ miR-145* in 43 BC clinical specimens and 12 normal bladder epithelia by real-time PCR. The functional analysis of the miRNA and molecular targets/pathways searching strategies were described as our previous studies (J Urol,192:1822-1830,2014; FEBS Lett,588:3170-3179,2014; PLoS One,9:e84311,2014). RESULTS: Expression levels of miR-145 and miR-145* were significantly lower than that in normal bladder epithelia (P < 0.0001). Gain-of-function studies revealed that cell proliferation, migration, and invasion were significantly inhibited in both miR-145 and miRNA-145* transfection into BC cell lines (each, P < 0.001). Combination of gene expression analysis of miR-145*-transfectants and in silico analysis showed that several oncogenic genes (HK2, YES1, FOSL1 etc.) were identified as miR-145* regulation in BC cells. CONCLUSIONS: Our genome-wide miRNA expression signature showed that miR-145* as a tumor-suppressive miR-145 passenger strand frequently reduced in BC cells and acts as a tumorsuppressor. Elucidation of miR-145/145*-mediated novel cancer pathways provide new insights of the potential mechanisms of BC oncogenesis. Furthermore, tumor-suppressive miR-145/145* might be contributed to development of miRNA-based cancer therapeutics in the disease.

230 Toll-like receptor 4-dependent, urine-induced activation of the stress sensor inositol-requiring protein 1 (IRE1) pathway in bladder cancer

INTRODUCTION AND OBJECTIVES: Generally in microRNA (miRNA) biogenesis, one strand (guide strand) of the duplex may potentially act as a functional miRNA and incorporated into the RNA-induced silencing complex and regulating target genes. In contrast, other strand (passenger strand: miRNA*) is disintegrated quickly. Our miRNA expression signature of bladder cancer (BC) by using deep-sequencing revealed that tumor-suppressive miRNA-145 and its passenger strand of miRNA-145* were significantly reduced in cancer tissues, suggesting these function as tumor suppressors in BC cells. The aim of the study was to investigate functional significance of miRNA-145* and its regulated molecular targets/ pathways in BC. METHODS: We evaluated the expression levels of miR-145/ miR-145* in 43 BC clinical specimens and 12 normal bladder epithelia by real-time PCR. The functional analysis of the miRNA and molecular targets/pathways searching strategies were described as our previous studies (J Urol,192:1822-1830,2014; FEBS Lett,588:3170-3179,2014; PLoS One,9:e84311,2014). RESULTS: Expression levels of miR-145 and miR-145* were significantly lower than that in normal bladder epithelia (P < 0.0001). Gain-of-function studies revealed that cell proliferation, migration, and invasion were significantly inhibited in both miR-145 and miRNA-145* transfection into BC cell lines (each, P < 0.001). Combination of gene expression analysis of miR-145*-transfectants and in silico analysis showed that several oncogenic genes (HK2, YES1, FOSL1 etc.) were identified as miR-145* regulation in BC cells. CONCLUSIONS: Our genome-wide miRNA expression signature showed that miR-145* as a tumor-suppressive miR-145 passenger strand frequently reduced in BC cells and acts as a tumorsuppressor. Elucidation of miR-145/145*-mediated novel cancer pathways provide new insights of the potential mechanisms of BC oncogenesis. Furthermore, tumor-suppressive miR-145/145* might be contributed to development of miRNA-based cancer therapeutics in the disease.

Abstract 1457: Development of miRNA-loaded polymeric nanoformulation for pancreatic cancer therapy

Abstract MicroRNAs (miRNAs) are small (18-22 nucleotide long) non-coding RNAs that play important roles in biological processes through post-transcriptional regulation of gene expression. Their aberrant expression and functional significance are reported in several human malignancies, including pancreatic cancer (PC). Recently, we identified miR-150 as a novel tumor suppressor microRNA in PC and demonstrated that its overexpression inhibits growth and malignant behavior of PC cells suggesting that restoration of miR-150 could serve as an effective therapeutic approach for pancreatic cancer. In the present study, we have developed a nanoparticle-based miR-150 delivery system and tested its therapeutic efficacy by in vitro assays. Using double emulsion solvent evaporation method, we developed a poly (D, L-lactide-co-glycolide) (PLGA)-based nanformulation (NF) of miR-150 (miR-150-NF). Polyethyleneimine (a cationic polymer) was incorporated in PLGA matrix to increase the encapsulation of miR-150. Physical characterization of miR-150-NF demonstrated that miR-150-loaded nanoparticles were spherical in shape, had high encapsulation efficiency (&amp;gt;75%), were stable at room temperature and exhibited sustained release profile. miR-150-NF efficiently delivered miR-150 mimics to PC cells and led to the downregulation of its target gene (MUC4) expression. Downregulation of MUC4 correlated with a concomitant decrease in the expression of its interacting partner, HER2, and repression of its downstream signaling. Furthermore, treatment of PC cells with miR-NF suppressed their growth, clonogenicity, motility and invasion. Together, these findings suggest that PLGA-based nanovector platform could be a potential candidate for systemic delivery of miR-150 to the pancreatic tumor cells and can be a step forward in miRNA-based cancer therapeutics. Citation Format: Sumit Arora, Suresh K. Swaminathan, Sanjeev K. Srivastava, Seema Singh, Jayanth Panyam, Ajay P. Singh. Development of miRNA-loaded polymeric nanoformulation for pancreatic cancer therapy. [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 1457. doi:10.1158/1538-7445.AM2014-1457

MicroRNAs as therapeutic targets in chemoresistance

Despite substantial progress in understanding the cancer signaling network, effective therapies remain scarce due to insufficient disruption of oncogenic pathways, drug resistance and drug-induced toxicity. New and more creative approaches are therefore required for the treatment of cancer. MicroRNAs (miRNAs) are a family of small noncoding RNAs that regulate gene expression by sequence-selective targeting of mRNAs, leading to a translational repression or mRNA degradation. Experimental evidence demonstrates that dysregulation of specific miRNAs leads to drug resistance in different cancers and correction of these miRNAs using miRNA mimics or antagomiRs can normalize the gene regulatory network and signaling pathways and sensitize cancerous cells to chemotherapy. Therefore, miRNA-based gene therapy provides an attractive anti-tumor approach for integrated cancer therapy. Here, we will discuss the involvement of microRNAs in chemotherapy resistance and focus on recent advancements in the development and delivery of miRNA-based cancer therapeutics.

The Therapeutic Potential of MicroRNAs in Cancer

MicroRNAs (miRNAs) have been uncovered as important posttranscriptional regulators of nearly every biological process in the cell. Furthermore, mounting evidence implies that miRNAs play key roles in the pathogenesis of cancer and that many miRNAs can function either as oncogenes or tumor suppressors. Thus, miRNAs have rapidly emerged as promising targets for the development of novel anticancer therapeutics. The development of miRNA-based cancer therapeutics relies on restoring the activity of tumor suppressor miRNAs using double-stranded miRNA mimics or inhibition of oncogenic miRNAs using single-stranded antisense oligonucleotides, termed antimiRs. In the present review, we focus on recent advancements in the discovery and development of miRNA-based cancer therapeutics using these 2 approaches. In addition, we summarize selected studies, in which modulation of miRNA activity in preclinical cancer models in vivo has demonstrated promising therapeutic potential.

35 Intermittent hormonal therapy in the treatment of prostate cancer

BRD4, a member of the bromodomain and extra-terminal domain (BET) protein family, plays a role in the organization of super-enhancers and transcriptional activation of oncogenes in cancer and is recognized as a promising target for cancer therapy. microRNAs (miRNAs), endogenous small noncoding RNAs, cause mRNA degradation or inhibit protein translation of their target genes by binding to complementary sequences. miRNA mimics simultaneously targeting several tumor-promoting genes and BRD4 may be useful as therapeutic agents of tumor-suppressive miRNAs (TS-miRs) for cancer therapy. To investigate TS-miRs for the development of miRNA-based cancer therapeutics, we performed function-based screening in 10 cancer cell lines with a library containing 2,565 human miRNA mimics. Consequently, miR-1293, miR-876-3p, and miR-6571-5p were identified as TS-miRs targeting BRD4 in this screening. Notably, miR-1293 also suppressed DNA repair pathways by directly suppressing the DNA repair genes APEX1 (apurinic-apyrimidinic endonuclease 1), RPA1 (replication protein A1), and POLD4 (DNA polymerase delta 4, accessory subunit). Concurrent suppression of BRD4 and these DNA repair genes synergistically inhibited tumor cell growth in vitro. Furthermore, administration of miR-1293 suppressed in vivo tumor growth in a xenograft mouse model. These results suggest that miR-1293 is a candidate for the development of miRNA-based cancer therapeutics.

27 Quality of life in metastatic renal cell carcinoma patients with ECOG PS >2 receiving targeted therapy

BRD4, a member of the bromodomain and extra-terminal domain (BET) protein family, plays a role in the organization of super-enhancers and transcriptional activation of oncogenes in cancer and is recognized as a promising target for cancer therapy. microRNAs (miRNAs), endogenous small noncoding RNAs, cause mRNA degradation or inhibit protein translation of their target genes by binding to complementary sequences. miRNA mimics simultaneously targeting several tumor-promoting genes and BRD4 may be useful as therapeutic agents of tumor-suppressive miRNAs (TS-miRs) for cancer therapy. To investigate TS-miRs for the development of miRNA-based cancer therapeutics, we performed function-based screening in 10 cancer cell lines with a library containing 2,565 human miRNA mimics. Consequently, miR-1293, miR-876-3p, and miR-6571-5p were identified as TS-miRs targeting BRD4 in this screening. Notably, miR-1293 also suppressed DNA repair pathways by directly suppressing the DNA repair genes APEX1 (apurinic-apyrimidinic endonuclease 1), RPA1 (replication protein A1), and POLD4 (DNA polymerase delta 4, accessory subunit). Concurrent suppression of BRD4 and these DNA repair genes synergistically inhibited tumor cell growth in vitro. Furthermore, administration of miR-1293 suppressed in vivo tumor growth in a xenograft mouse model. These results suggest that miR-1293 is a candidate for the development of miRNA-based cancer therapeutics.

33 Pure red cell dysplasia in a patient with metastatic cancer prostate

BRD4, a member of the bromodomain and extra-terminal domain (BET) protein family, plays a role in the organization of super-enhancers and transcriptional activation of oncogenes in cancer and is recognized as a promising target for cancer therapy. microRNAs (miRNAs), endogenous small noncoding RNAs, cause mRNA degradation or inhibit protein translation of their target genes by binding to complementary sequences. miRNA mimics simultaneously targeting several tumor-promoting genes and BRD4 may be useful as therapeutic agents of tumor-suppressive miRNAs (TS-miRs) for cancer therapy. To investigate TS-miRs for the development of miRNA-based cancer therapeutics, we performed function-based screening in 10 cancer cell lines with a library containing 2,565 human miRNA mimics. Consequently, miR-1293, miR-876-3p, and miR-6571-5p were identified as TS-miRs targeting BRD4 in this screening. Notably, miR-1293 also suppressed DNA repair pathways by directly suppressing the DNA repair genes APEX1 (apurinic-apyrimidinic endonuclease 1), RPA1 (replication protein A1), and POLD4 (DNA polymerase delta 4, accessory subunit). Concurrent suppression of BRD4 and these DNA repair genes synergistically inhibited tumor cell growth in vitro. Furthermore, administration of miR-1293 suppressed in vivo tumor growth in a xenograft mouse model. These results suggest that miR-1293 is a candidate for the development of miRNA-based cancer therapeutics.

MicroRNAs, cancer and cancer stem cells

MicroRNAs regulate self-renewal, differentiation, and division of cells via post-transcriptional gene silencing. Aberrant microRNA levels, specifically an overall downregulation, are present in many cancers, as compared to their normal tissue counterparts. Therefore, a potential therapeutic use of microRNAs is to correct these aberrant transcript levels involved in the signaling pathways of cancer. This review focuses on the current knowledge of microRNAs and their involvement with cancer cells and cancer stem cells. The methods currently being used to develop miRNA-based cancer therapeutics are examined, and the limitations halting further progress are also discussed.