Transferrin-Conjugated SNALPs Encapsulating 2 -O-Methylated miR-34a for the Treatment of Multiple Myeloma

Stable nucleic acid lipid vesicles (SNALPs) encapsulating miR-34a to treat multiple myeloma (MM) were developed. Wild type or completely 2 -O-methylated (OMet) MiR-34a was used in this study. Moreover, SNALPs were conjugated with transferrin (Tf) in order to target MM cells overexpressing transferrin receptors (TfRs). The type of miR-34a chemical backbone did not significantly affect the characteristics of SNALPs in terms of mean size, polydispersity index, and zeta potential, while the encapsulation of an OMet miR-34a resulted in a significant increase of miRNA encapsulation into the SNALPs. On the other hand, the chemical conjugation of SNALPs with Tf resulted in a significant decrease of the zeta potential, while size characteristics and miR-34a encapsulation into SNALPs were not significantly affected. In an experimental model of MM, all the animals treated with SNALPs encapsulating miR-34a showed a significant inhibition of the tumor growth. However, the use of SNALPs conjugated with Tf and encapsulating OMet miR-34a resulted in the highest increase of mice survival. These results may represent the proof of concept for the use of SNALPs encapsulating miR-34a for the treatment of MM

Mir-34: A New Weapon Against Cancer?

The microRNA(miRNA)-34a is a key regulator of tumor suppression. It controls the expression of a plethora of target proteins involved in cell cycle, differentiation and apoptosis, and antagonizes processes that are necessary for basic cancer cell viability as well as cancer stemness, metastasis, and chemoresistance. In this review, we focus on the molecular mechanisms of miR-34a-mediated tumor suppression, giving emphasis on the main miR-34a targets, as well as on the principal regulators involved in the modulation of this miRNA. Moreover, we shed light on the miR-34a role in modulating responsiveness to chemotherapy and on the phytonutrients-mediated regulation of miR-34a expression and activity in cancer cells. Given the broad anti-oncogenic activity of miR-34a, we also discuss the substantial benefits of a new therapeutic concept based on nanotechnology delivery of miRNA mimics. In fact, the replacement of oncosuppressor miRNAs provides an effective strategy against tumor heterogeneity and the selective RNA-based delivery systems seems to be an excellent platform for a safe and effective targeting of the tumor

Inhibition of miR-21 restores RANKL/OPG ratio in multiple myeloma-derived bone marrow stromal cells and impairs the resorbing activity of mature osteoclasts

miR-21 is an oncogenic microRNA (miRNA) with an emerging role as therapeutic target in human malignancies, including multiple myeloma (MM). Here we investigated whether miR-21 is involved in MM-related bone disease (BD). We found that miR-21 expression is dramatically enhanced, while osteoprotegerin (OPG) is strongly reduced, in bone marrow stromal cells (BMSCs) adherent to MM cells. On this basis, we validated the 3'UTR of OPG mRNA as miR-21 target. Constitutive miR-21 inhibition in lentiviral-transduced BMSCs adherent to MM cells restored OPG expression and secretion. Interestingly, miR-21 inhibition reduced RANKL production by BMSCs. Overexpression of protein inhibitor of activated STAT3 (PIAS3), which is a direct and validated target of miR-2, antagonized STAT3-mediated RANKL gene activation. Finally, we demonstrate that constitutive expression of miR-21 inhibitors in BMSCs restores RANKL/OPG balance and dramatically impairs the resorbing activity of mature osteoclasts. Taken together, our data provide proof-of-concept that miR-21 overexpression within MM-microenviroment plays a crucial role in bone resorption/ apposition balance, supporting the design of innovative miR-21 inhibition-based strategies for MM-related BD

Targeting miR-21 inhibits in vitro and in vivo multiple myeloma cell growth

Purpose: Deregulated expression of miRNAs plays a role in the pathogenesis and progression of multiple myeloma. Among upregulated miRNAs, miR-21 has oncogenic potential and therefore represents an attractive target for the treatment of multiple myeloma. Experimental Design: Here, we investigated the in vitro and in vivo anti-multiple myeloma activity of miR-21 inhibitors. Results: Either transient-enforced expression or lentivirus-based constitutive expression of miR-21 inhibitors triggered significant growth inhibition of primary patient multiple myeloma cells or interleukin-6-dependent/independent multiple myeloma cell lines and overcame the protective activity of human bone marrow stromal cells. Conversely, transfection of miR-21 mimics significantly increased proliferation of multiple myeloma cells, showing its tumor-promoting potential in multiple myeloma. Importantly, upregulation of miR-21 canonical validated targets (PTEN, Rho-B, and BTG2), together with functional impairment of both AKT and extracellular signal-regulated kinase signaling, were achieved by transfection of miR-21 inhibitors into multiple myeloma cells. In vivo delivery of miR-21 inhibitors in severe combined immunodeficient mice bearing human multiple myeloma xenografts expressing miR-21induced significant antitumor activity. Upregulation of PTEN and downregulation of p-AKT were observed in retrieved xenografts following treatment with miR-21 inhibitors. Conclusion: Our findings show the first evidence that in vivo antagonism of miR-21 exerts anti-multiple myeloma activity, providing the rationale for clinical development of miR-21 inhibitors in this still incurable disease

In vitro and in vivo activity of a novel locked nucleic acid (LNA)-inhibitor-miR-221 against multiple myeloma cells.

BACKGROUND & AIM: The miR-221/222 cluster is upregulated in malignant plasma cells from multiple myeloma (MM) patients harboring the t(4;14) translocation. We previously reported that silencing of miR-221/222 by an antisense oligonucleotide induces anti-MM activity and upregulates canonical miR-221/222 targets. The in vivo anti-tumor activity occurred when miR-221/222 inhibitors were delivered directly into MM xenografts. The aim of the present study was to evaluate the anti-MM activity of a novel phosphorothioate modified backbone 13-mer locked nucleic acid (LNA)-Inhibitor-miR-221 (LNA-i-miR-221) specifically designed for systemic delivery. METHODS: In vitro anti-MM activity of LNA-i-miR-221 was evaluated by cell proliferation and BrdU uptake assays. In vivo studies were performed with non-obese diabetic/severe combined immunodeficient (NOD.SCID) mice bearing t(4;14) MM xenografts, which were intraperitoneally or intravenously treated with naked LNA-i-miR-221. RNA extracts from retrieved tumors were analyzed for miR-221 levels and modulation of canonical targets expression. H&E staining and immunohistochemistry were performed on retrieved tumors and mouse vital organs. RESULTS: In vitro, LNA-i-miR-221 exerted strong antagonistic activity against miR-221 and induced upregulation of the endogenous target p27Kip1. It had a marked anti-proliferative effect on t(4;14)-translocated MM cells but not on MM cells not carrying the translocation and not overexpressing miR-221. In vivo, systemic treatment with LNA-i-miR-221 triggered significant anti-tumor activity against t(4;14) MM xenografts; it also induced miR-221 downregulation, upregulated p27Kip1 and reduced Ki-67. No behavioral changes or organ-related toxicity were observed in mice as a consequence of treatments. CONCLUSIONS: LNA-i-miR-221 is a highly stable, effective agent against t(4;14) MM cells, and is suitable for systemic use. These data provide the rationale for the clinical development of LNA-i-miR-221 for the treatment of MM

In vivo activity of miR-34a mimics delivered by stable nucleic acid lipid particles (SNALPs) against multiple myeloma.

Multiple myeloma (MM) is a disease with an adverse outcome and new therapeutic strategies are urgently awaited. A rising body of evidence supports the notion that microRNAs (miRNAs), master regulators of eukaryotic gene expression, may exert anti-MM activity. Here, we evaluated the activity of synthetic miR-34a in MM cells. We found that transfection of miR-34a mimics in MM cells induces a significant change of gene expression with relevant effects on multiple signal transduction pathways. We detected early inactivation of pro-survival and proliferative kinases Erk-2 and Akt followed at later time points by caspase-6 and -3 activation and apoptosis induction. To improve the in vivo delivery, we encapsulated miR-34a mimics in stable nucleic acid lipid particles (SNALPs). We found that SNALPs miR-34a were highly efficient in vitro in inhibiting growth of MM cells. Then, we investigated the activity of the SNALPs miR-34a against MM xenografts in SCID mice. We observed significant tumor growth inhibition (p<0.05) which translated in mice survival benefits (p=0.0047). Analysis of miR-34a and NOTCH1 expression in tumor retrieved from animal demonstrated efficient delivery and gene modulation induced by SNALPs miR-34a in the absence of systemic toxicity. We here therefore provide evidence that SNALPs miR-34a may represent a promising tool for miRNA-therapeutics in MM

LNA-i-miR-221 antiproliferative activity and target silencing in retrieved MM xenografted tumors.

<p>A) q-RT-PCR of p27Kip1 mRNA levels in treated tumors retrieved from mice after intravenous LNA-i-miR-221 treatment. Raw Ct values were normalized to GAPDH housekeeping mRNA and expressed as ΔΔCt values calculated using the comparative cross threshold method (miRNA expression in LNA-i-miR-NC treated animals) ±SD. B) Western blot analysis of p27Kip1 protein in retrieved tumors from mice treated with LNA-i-miR-221 inhibitors or LNA-i-miR-NC. GAPDH was the protein loading control. C) H&E (200-fold magnification), p27Kip1 (200-fold magnification) and Ki-67 (10–fold magnification) immunohistochemistry staining of xenografted tumors retrieved from treated animals. Representative images are shown.</p

Molecular effects induced by LNA-i-miR-221 transfection in MM cells.

<p>miR-221(A) q-RT-PCR 24, 48 and 72 hours after transfection with LNA-i-miR-221 and LNA-i-miR-NC in NCI-H929 cells. The results are shown as miRNA expression levels after normalization with RNU44 and ΔΔCt calculations. Data represent the average of 3 independent experiments ±SD. B) q-RT-PCR of p27Kip1 mRNA expression 24 and 48 hours after transfection with LNA-i-miR-221 or scrambled control in NCI-H929 cells. Data represent the average of 3 independent experiments ±SD after normalization with GAPDH mRNA and ΔΔCt calculations. (*) P<0.05, (**) P<0.01. C) Western blot analysis of p27Kip1 protein in NCI-H929 cells 24, 48 and 72 hours after transfection with LNA-i-miR-221 or control. GAPDH was used as protein loading control.</p