Characterizing exogenous mRNA delivery, trafficking, cytoplasmic release and RNA-protein correlations at the level of single cells

The use of synthetic messenger ribonucleic acid (mRNA) to express specific proteins is a highly promising therapeutic and vaccine approach that avoids many safety issues associated with viral or DNA-based systems. However, in order to optimize mRNA designs and delivery, technology advancements are required to study fundamental mechanisms of mRNA uptake and localization at the single-cell and tissue level. Here, we present a single RNA sensitive fluorescent labeling method which allows us to label and visualize synthetic mRNA without significantly affecting function. This approach enabled single cell characterization of mRNA uptake and release kinetics from endocytic compartments, the measurement of mRNA/protein correlations, and motivated the investigation of mRNA induced cellular stress, all important mechanisms influencing protein production. In addition, we demonstrated this approach can facilitate near-infrared imaging of mRNA localization in vivo and in ex-vivo tissue sections, which will facilitate mRNA trafficking studies in pre-clinical models. Overall, we demonstrate the ability to study fundamental mechanisms necessary to optimize delivery and therapeutic strategies, in order to design the next generation of novel mRNA therapeutics and vaccines.

Strategies for modulating innate immune activation and protein production of in vitro transcribed mRNAs

Synthetic mRNA has recently shown great potential as a tool for genetic introduction of proteins. Its utility as a gene carrier has been demonstrated in several studies for both the introduction of therapeutic proteins and subunit vaccines. At one point, synthetic mRNA was believed to be too immunogenic and labile for pharmaceutical purposes. However, the development of several strategies have enabled mRNA technology to overcome these challenges, including incorporation of modified nucleotides, codon optimization of the coding region, incorporation of untranslated regions into the mRNA, and the use of delivery vehicles. While these approaches have been shown to enhance performance of some mRNA constructs, gene-to-gene variation and low efficiency of mRNA protein production are still significant hurdles. Further mechanistic understanding of how these strategies affect protein production and innate immune activation is needed for the widespread adoption for both therapeutic and vaccine applications. This review highlights key studies involved in the development of strategies employed to increase protein expression and control the immunogenicity of synthetic mRNA. Areas in the literature where improved understanding is needed will also be discussed.

Abstract 1235: Inducible overexpression of bHLH transcriptional regulator Id4 abrogates tumorigenicity of prostate cancer xenografts

Introduction: Inhibitor of DNA binding/differentiation 4 (Id4) has been shown to be highly expressed during prostate development. However, in many cancers including prostate, Id4 is epigenetically silenced due to promoter hyper-methylation. In this study we developed a doxycycline inducible system for Id4 overexpression and show that controlled increase of Id4 in an aggressive metastatic prostate cancer cell line DU145, which lacks Id4 expression results in attenuation of tumor forming ability of this cell line and confirming its role as a tumor suppressor.

Methods: Tetracycline inducible system was used to stably overexpress Id4 in DU145 cells. Empty vector backbone was used as a control. The Id4 overexpressed (DU(+)iId4) and vector control (DU(+)iVC) cells were used to investigate migration (scratch wound assay) and anchorage independent growth (soft agar assay). Tumorigenicity of DU(+)iId4 and DU(+)iVC cells was investigated in Scid beige mice. The gene expression profile between DU(+)iId4 and DU(+)iVC cells was analyzed by RNAseq. The DU(+)iId4 and DU(+)iVC tumors from mice were used for immunohistochemistry to validate prostate cancer pathways and RNAseq data.

Results: Id4 was cloned in pcDNA4/TO/myc-His version A and stably transfected and clonally selected for overexpression in DU145 cells stably expressing pcDNA6/TR. The overexpression of Id4 on induction by doxycycline (a tetracycline analogue) was confirmed by qRT-PCR and western blotting. A clone with maximum expression was selected for further studies. On inducing the DU145 cells with doxycycline, an increase in apoptosis was observed as compared to un-induced DU145 as well as cells expressing the empty control vector. Decrease in migration and anchorage independent colony forming ability was also observed upon induction of Id4 in scratch wound and soft agar assay, respectively. Subcutaneous injection of DU145 cells in Scid beige mice resulted in formation of tumors, however upon induction of Id4 expression by doxycycline from day 0 or 2 weeks after injection of the cells showed a significant decrease in the tumor forming ability of the DU145 cells as evident from the reduction in the tumor weight and volume. Immunohistochemistry on tumor tissues was found to be in support of the RNAseq data.

Conclusion: This study reports for the first time that conditional overexpression of tumor suppressor Id4 in prostate cancer cell lines DU145 results in diminution of tumor formation. The data describes use of a system that allows for the temporal regulation of Id4 expression in vivo which could act as a preliminary step in mimicking controlled delivery of Id4 for therapeutic purpose.

Acknowledgement: This study was supported by NIH/NCI RO1 CA128914 and NIH/NCRR/RCMI G12MD007590.

Citation Format: Divya Patel, Derrick J. Morton, Maxwell Korang-Yeboah, Yamini Gorantla, Sushma Bhosle, Perri Nagappan, Nathen Bowen, Jaideep Chaudhary. Inducible overexpression of bHLH transcriptional regulator Id4 abrogates tumorigenicity of prostate cancer xenografts. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1235. doi:10.1158/1538-7445.AM2015-1235

Interferon inducible antiviral MxA is inversely associated with prostate cancer and regulates cell cycle, invasion and Docetaxel induced apoptosis

BACKGROUND

The interferon inducible Myxovirus (influenza virus) resistance A (MxA) is considered as a key mediator of the interferon-induced antiviral response. Mx proteins contain the typical GTP-binding motif and show significant homology to dynamin family of GTPases. Strong interaction of MxA with tubulin suggests that Mx proteins could be involved in mitosis. Studies have shown that MxA inhibit tumor motility/metastasis and virus induced apoptosis. However, the clear association between MxA expression and cancer remains unknown. Meta-analysis suggested that MxA expression was inversely correlated with prostate cancer (PCa). In this study, we demonstrate the expression MxA in PCa and its functional significance on the cancer phenotype.

METHODS

The expression of MxA protein in prostate cancer was examined by immuno-histochemistry. MxA was knocked down (shMxA) or over-expressed (pMxA) in DU145 or LNCaP PCa cell lines respectively. These cell lines were used to study proliferation, apoptosis, invasion, migration, and anchorage independent growth. Co-localization of MxA with tubulin was performed by immuno-cytochemistry following Docetaxel treatment.

RESULTS

The expression of MxA protein was significantly decreased in PCa as compared to the normal tissues. DU145 cells lacking MxA (DU145 + chMxA) showed significant increase in proliferation, associated with decreased expression of CDKN1A and B. Increased migration, anchorage independent growth in DU145 + shMxA cells was associated with increased MMP13 expression. Tubulin organization was also dependent on MxA expression. Tubulin polymerizing agents such as Docetaxel was less effective in promoting apoptosis in cells lacking MxA due to altered tubulin organization. Gain of MxA expression in LNCaP cells (LNCaP + pMxA) resulted in cell cycle arrest that was associated with increased expression of CDKN1A. MxA expression was also down-regulated by dihydrotestosterone in LNCaP cells.

CONCLUSIONS

MxA expression is inversely correlated with prostate cancer. Down-regulation of MxA in LNCaP cells by DHT suggests that MxA could play a significant role in disease progression. Loss of MxA expression results in increased metastasis and decreased sensitivity to Docetaxel suggesting that MxA expression could determine the outcome of chemo-therapeutic treatment. Additional studies will be required to fully establish the cross-talk between androgen receptor-IFN pathway in regulating MxA expression in the normal prostate and prostate cancer. Prostate 75:266-279, 2015. © 2014 Wiley Periodicals, Inc.

Antibody responses against xenotropic murine leukemia virus-related virus envelope in a murine model

BACKGROUND

Xenotropic murine leukemia virus-related virus (XMRV) was recently discovered to be the first human gammaretrovirus that is associated with chronic fatigue syndrome and prostate cancer (PC). Although a mechanism for XMRV carcinogenesis is yet to be established, this virus belongs to the family of gammaretroviruses well known for their ability to induce cancer in the infected hosts. Since its original identification XMRV has been detected in several independent investigations; however, at this time significant controversy remains regarding reports of XMRV detection/prevalence in other cohorts and cell type/tissue distribution. The potential risk of human infection, coupled with the lack of knowledge about the basic biology of XMRV, warrants further research, including investigation of adaptive immune responses. To study immunogenicity in vivo, we vaccinated mice with a combination of recombinant vectors expressing codon-optimized sequences of XMRV gag and env genes and virus-like particles (VLP) that had the size and morphology of live infectious XMRV.

RESULTS

Immunization elicited Env-specific binding and neutralizing antibodies (NAb) against XMRV in mice. The peak titers for ELISA-binding antibodies and NAb were 1:1024 and 1:464, respectively; however, high ELISA-binding and NAb titers were not sustained and persisted for less than three weeks after immunizations.

CONCLUSIONS

Vaccine-induced XMRV Env antibody titers were transiently high, but their duration was short. The relatively rapid diminution in antibody levels may in part explain the differing prevalences reported for XMRV in various prostate cancer and chronic fatigue syndrome cohorts. The low level of immunogenicity observed in the present study may be characteristic of a natural XMRV infection in humans.

Isolation and Confirmation of Listeria Species from Seafood off Goa Region by Polymerase Chain Reaction

Several food borne outbreaks have highlighted the importance of Listeria monocytogenes to the public health and have been recognized as an emerging, important food borne pathogen, and a causative agent of listerioses. A number of genes are involved in the manifestation of Listeria virulence, hlyA is one among them. In the present study, 111 marine fish samples including prawns, finfishes and bivalves were screened for the presence of Listeria species. The isolates were characterized biochemically and further L. monocytogenes were confirmed by polymerase chain reaction (PCR) technique using the hlyA gene as a tool to differentiate between L. monocytogenes and other non-pathogenic Listeria species. Out of 111 samples 5 (4.5%) samples were positive for L. monocytogenes. Among the three different types of samples bivalves were found to have maximum percent (12.5) of L. monocytogenes followed by prawns (3.84) and finfishes (2.9). Among all the 111 samples, 15 (13.51%) samples were positive for other Listeria species. It was observed that Listeria occurrence is more in shellfishes than in fin fishes. All the isolates were sensitive towards five different antibiotics in sequence ciprofloxacin > sulphafurazole > norfloxacin > ampicillin and gentamicin.

Molecular Rearrangement of Longifolene by Arthrobacter ilicis T 2

Arthrobacter ilicis T 2 brings about a unique type of cometabolic structural rearrangement of longifolene, a sesquiterpene, resulting in the formation of an acid. Infrared, nuclear magnetic resonance, mass spectrometry, and decoupling studies indicate that the acid product has a sativenelike structure, which is confirmed by conversion of the acid to its methyl ester and hydrocarbon.