*MiRNA-Based Therapeutics in Oncology, Realities, and Challenges DOI: http://dx.doi.org/10.5772/intechopen.81847*

*Antisense Therapy*

*5.1.5 miR-16*

*5.1.6 miR-155*

Based on these results, encapsulating miR-34a mimics into liposomes (MRX34, Mirna

miR-16 represents another TS-miR whose decreased expression has been observed among different types of cancers, as well as in nonsmall cell lung cancer (NSCLC) [69], prostate cancer [70], or malignant pleural mesothelioma [71], making it a strong candidate for replacement therapy in future studies with potential use in clinical trials. The data presented by Takeshita et al. [72] revealed that systemic delivery of synthetic miR-16, conjugated to atelocollagen, significantly reduced bone metastases and tumor development in a prostate cancer animal model. Moreover, their *in vitro* data suggest that miR-16 suppresses prostate tumor growth by regulating the expression of genes associated with cell-cycle control and cellular proliferation such as CDK1 and CDK2. The Hao group has also revealed that miR-16-1/atelocollagen-aptamer complex used in a mice model of human prostate cancer with bone metastasis enhanced anticancer efficacy. They also demonstrated that the efficacy of this complex, including aptamers, was higher, both *in vitro* and *in vivo* models than the other atelocollagen complexes that do not include aptamers. Re-expression of miR-16 mimic in malignant pleural mesothelioma cell lines and nude mouse models has caused the inhibition of tumor growth, correlated with downregulation of target genes Bcl-2 and CCND1 [71].

miR-155, one of the first described oncomiRs [73], was identified as highly expressed in a wide range of tumors including chronic lymphocytic leukemia [74], lung cancer [75], breast cancer [76], acute myeloid leukemia [77], solid tumor

ogous recombination DNA repair pathway, and the clinical study of Gasparini et al. [80] for triple negative breast cancer revealed that low miR-155 expression level correlated with worse progression-free survival. Moreover, Pouliot et al. [81] reported a reduced expression of miR-155 in human epidermoid carcinoma cisplatin-resistant cell lines. Dysregulated expression of this miRNA sensitizes the cells to cisplatin-induced apoptosis by targeting WEE1 and CHK1 kinases. Based on these results, future studies are encouraged with the focus on the use of exogenous agents, such as mimics or anti-miRs to sensitize cancer cells to chemo- or radio-

OncomiR-155 was discovered to target RAD51, an important gene in the homol-

Alexander et al. [82] found that endogenous miR-155, an important microRNA that regulates inflammation, is released from dendritic cells within exosomes and transferred to recipient dendritic cells. Administration of miR-155 containing exosomes enhances inflammatory gene expression as a response to endotoxin-induced inflammation in mice. Their findings provide strong evidence that endogenous microRNAs follow a functional transfer between immune cells and represent a

More examples of tumor-suppressor miRNA mimics, which target multiple

Given the results provided by *in vitro* and *in vivo* studies, several clinical trials including miRNA-based therapy in human cancers were subsequently initiated

oncogenic transcripts, were recently presented by Hosseinahli et al. [41].

including stomach, prostate, colon, pancreas [78], and melanoma [79].

therapy, thus overcoming resistance to therapy.

regulatory mechanism for inflammatory response.

**5.2 Clinical studies involving miRNA-based therapy**

Therapeutics Inc.) was later proposed to be investigated in clinical trials [68].

**40**

(**Table 1**).

In April 2013, Mirna Therapeutics, Inc., a publicly traded company based in Carlsbad, California, which primarily focuses on anti-miRNAs technology, announced that their leading product candidate, MRX34, a mimic of miR-34 encapsulated in a liposomal nanoparticle formulation, called NOV40, was the first microRNA mimic to enter clinical development. The multicenter phase I trial of MRX34 included patients diagnosed with primary liver cancer, nonsmall cell lung cancer (NSCLC), lymphoma, melanoma, multiple myeloma, or renal cell carcinoma. The trial aimed to increase the number of intravenously doses with two times per week or five times per day schedule. In June 2016, a total of 99 patients suffering from HCC, NSCLC, or pancreatic cancer had been enrolled in the study [83]. The phase I clinical trial confirmed partial responses in a patient with metastasized hepatocellular carcinoma (HCC), a patient with advanced acral melanoma, and a patient with advanced renal cell carcinoma (RCC), evaluated through Response Evaluation Criteria in Solid Tumors (RECIST). Also, 14 patients were detected with stable disease (median duration 136 days; range 79–386 days). Results from white blood cell analysis indicated a significant reduction in two miR-34 target genes FOXP1 and BCL2. Nonetheless, because of the immune-related adverse responses involving patient deaths, the trial was finished. Since the cause of these immune reactions remains still unclear, preclinical trials will be need in order to better understand the immune-related toxicities. After passing successfully the phase I clinical trial, they intended to advance into two phase II clinical studies: one for patients diagnosed with advanced malignant melanoma and another for patients diagnosed with advanced renal cell carcinoma (RCC). In concordance with the advancements made by MRX34, their lead product candidate, through the clinical development, miR-34 mimics represent a new promising class of replacement therapy used in cancer. Additionally, Cortez et al. [84] reported that p53 regulated PDL1 expression via miR-34 in nonsmall-cell lung cancer. Administration of miR-34a mimics (MRX34), alone or in combination with radiotherapy (XRT), reduced PDL1 expression in the tumor and antagonized T-cell exhaustion.

In November 2014, EnGeneIC, a privately held Australian company in collaboration with Asbestos Diseases Research Institute, Sydney, Australia, announced the start of phase I clinical trial using miR-16 mimic charged in nanocells, a bacterial-derived transfection system EDV™. The trial included patients suffering from malignant pleural mesothelioma (MPM) and advanced nonsmall cell lung cancer (NSCLC), refractory to standard therapy. miR-16 mimic-based therapy were delivered intravenously, using EnGeneIC Delivery Vehicle (EDV)-Packaging, and were surface conjugated with an EGFR-targeting antibody in order to facilitate the target of tumor site [85]. Preliminary data presented by Van Zandwijk et al. [86] show manageable safety in response to infusion of 5 billion nanocells loaded with 1.5 μg miR-15/16 mimics as a first-dose level in the first five patients that had been enrolled. Because of the fact that this targomiR trial using miR-16 as a replacement therapy did not present adverse immune response and toxic effects, it is expected to continue to phase II study [86].

In March 2016, MiRagen Therapeutics, Inc., a privately held company based in Boulder, Colorado, announced the initiation of phase I clinical trial to investigate the anticancer product candidate: MRG-106, a synthetic microRNA antagonist of microRNA-155 (LNA anti-miR). The phase I clinical trial is currently tested in patients diagnosed with cutaneous T-cell lymphoma (CTCL) of the mycosis fungoides (MF) subtype [89].

Despite some promising preclinical results, the outcome of MRX34 translational clinical trial using miR-16 as a replacement therapy, designed to restore the expression of miR-34 in patients diagnosed with different types of cancer, was discouraging due to adverse toxic effects. At present, this clinical trial is finished, and its suitability to further development to phase II study remains under question.

**43**

**Figure 3.**

*MiRNA-Based Therapeutics in Oncology, Realities, and Challenges*

applying organ-specific administration routes [41].

However, this drawback can be addressed by optimizing therapeutic doses and

Epithelial-to-mesenchymal transition (EMT) allows tumor cells to enter the metastatic cascade by changing their morphological and molecular characteristics, and it represents a wide spectrum that cancer cells keep transiting. The EMT program relies on an intricate network of signaling pathways that dictate a series of phenotypic changes in epithelial cells. One clearly visible aspect is the loss of apical-basal polarity and cell-to-cell interaction caused by the destabilization of tight junctions, decreased claudin, occludin, and E-cadherin repression by SNAIL, SLUG, ZEB, TWIST, and SMAD, and its interchange with N-cadherin, a process known as the "cadherin switch" [90, 91]. Moreover, the overexpression of vimentin, a cytoskeleton intermediate-filament protein of mesenchymal origin that connects the nucleus to the plasma membrane, enables filopodia formation and a fibroblastic spindle-like morphology. Vimentin was proved to be induced through Slug and Ras signaling, and it promotes cell movement and migration [92]. The next step is the degradation of extracellular matrix components under the activity of matrix metal-

**6. Future challenges: new reliable miRNAs for target therapies**

loproteinases and the invasion of the surrounding stroma (**Figure 3**).

regulatory noncoding RNAs, especially micro-RNAs [93].

potential in becoming microRNA therapy targets (**Table 2**).

The EMT is coordinated by a series of signaling pathways triggered by either the tumor microenvironment or the intrinsic factors, and it falls under the incidence of

This is the reason why finding potential microRNA targets for blocking EMT could support the efforts already made in blocking metastasis and improving cancer therapy strategies. Right below, we are succinctly reviewing the results of several studies that investigated the role of microRNAs in EMT and metastasis and their

The influence of cancer-associated fibroblasts (CAFs) secreted exosomes over endometrial cancer progression was questioned in a study by Li et al. [94]. CAFs secreted exosomes contained significantly lower levels of miR-148b than normal fibroblasts, and miR-148b expression was lower in endometrial cancer specimens than in normal adjacent tissues. miR-148b was correlated with improved prognosis, *in vitro* and *in vivo* studies suggesting its role as an EMT inhibitor. Downregulation of DNMT1 oncogene was the mechanism proposed for miR-148b-mediated suppression of endometrial cancer progression. Also, relating to the tumor microenvironment, emerging evidence shows the prometastatic effect of a hypoxic

*The EMT-MET plasticity of tumor cells, their migration, and invasion as tumor circulating cells (CTCs).*

*DOI: http://dx.doi.org/10.5772/intechopen.81847*

*Antisense Therapy*

In April 2013, Mirna Therapeutics, Inc., a publicly traded company based in Carlsbad, California, which primarily focuses on anti-miRNAs technology, announced that their leading product candidate, MRX34, a mimic of miR-34 encapsulated in a liposomal nanoparticle formulation, called NOV40, was the first microRNA mimic to enter clinical development. The multicenter phase I trial of MRX34 included patients diagnosed with primary liver cancer, nonsmall cell lung cancer (NSCLC), lymphoma, melanoma, multiple myeloma, or renal cell carcinoma. The trial aimed to increase the number of intravenously doses with two times per week or five times per day schedule. In June 2016, a total of 99 patients suffering from HCC, NSCLC, or pancreatic cancer had been enrolled in the study [83]. The phase I clinical trial confirmed partial responses in a patient with metastasized hepatocellular carcinoma (HCC), a patient with advanced acral melanoma, and a patient with advanced renal cell carcinoma (RCC), evaluated through Response Evaluation Criteria in Solid Tumors (RECIST). Also, 14 patients were detected with stable disease (median duration 136 days; range 79–386 days). Results from white blood cell analysis indicated a significant reduction in two miR-34 target genes FOXP1 and BCL2. Nonetheless, because of the immune-related adverse responses involving patient deaths, the trial was finished. Since the cause of these immune reactions remains still unclear, preclinical trials will be need in order to better understand the immune-related toxicities. After passing successfully the phase I clinical trial, they intended to advance into two phase II clinical studies: one for patients diagnosed with advanced malignant melanoma and another for patients diagnosed with advanced renal cell carcinoma (RCC). In concordance with the advancements made by MRX34, their lead product candidate, through the clinical development, miR-34 mimics represent a new promising class of replacement therapy used in cancer. Additionally, Cortez et al. [84] reported that p53 regulated PDL1 expression via miR-34 in nonsmall-cell lung cancer. Administration of miR-34a mimics (MRX34), alone or in combination with radiotherapy (XRT), reduced

PDL1 expression in the tumor and antagonized T-cell exhaustion.

In November 2014, EnGeneIC, a privately held Australian company in collaboration with Asbestos Diseases Research Institute, Sydney, Australia, announced the start of phase I clinical trial using miR-16 mimic charged in nanocells, a bacterial-derived transfection system EDV™. The trial included patients suffering from malignant pleural mesothelioma (MPM) and advanced nonsmall cell lung cancer (NSCLC), refractory to standard therapy. miR-16 mimic-based therapy were delivered intravenously, using EnGeneIC Delivery Vehicle (EDV)-Packaging, and were surface conjugated with an EGFR-targeting antibody in order to facilitate the target of tumor site [85]. Preliminary data presented by Van Zandwijk et al. [86] show manageable safety in response to infusion of 5 billion nanocells loaded with 1.5 μg miR-15/16 mimics as a first-dose level in the first five patients that had been enrolled. Because of the fact that this targomiR trial using miR-16 as a replacement therapy did not present adverse immune response and toxic effects, it is expected to continue to phase II study [86]. In March 2016, MiRagen Therapeutics, Inc., a privately held company based in Boulder, Colorado, announced the initiation of phase I clinical trial to investigate the anticancer product candidate: MRG-106, a synthetic microRNA antagonist of microRNA-155 (LNA anti-miR). The phase I clinical trial is currently tested in patients diagnosed with cutaneous T-cell lymphoma (CTCL) of the mycosis fungoi-

Despite some promising preclinical results, the outcome of MRX34 translational clinical trial using miR-16 as a replacement therapy, designed to restore the expression of miR-34 in patients diagnosed with different types of cancer, was discouraging due to adverse toxic effects. At present, this clinical trial is finished, and its suitability to further development to phase II study remains under question.

**42**

des (MF) subtype [89].

However, this drawback can be addressed by optimizing therapeutic doses and applying organ-specific administration routes [41].
