Biomedical subjects

Mahaveer Swaroop Bhojani

Publications and source records attributed to Mahaveer Swaroop Bhojani.

4 recordsLinked to original sources

PubMed2002

Noninvasive real-time imaging of apoptosis.

Strict coordination of proliferation and programmed cell death (apoptosis) is essential for normal physiology. An imbalance in these two opposing processes results in various diseases including AIDS, neurodegenerative disorders, myelodysplastic syndromes, ischemiareperfusion injury, cancer, autoimmune disease, among others. Objective and quantitative noninvasive imaging of apoptosis would be a significant advance for rapid and dynamic screening as well as validation of experimental therapeutic agents. Here, we report the development of a recombinant luciferase reporter molecule that when expressed in mammalian cells has attenuated levels of reporter activity. In cells undergoing apoptosis, a caspase-3-specific cleavage of the recombinant product occurs, resulting in the restoration of luciferase activity that can be detected in living animals with bioluminescence imaging. The ability to image apoptosis noninvasively and dynamically over time provides an opportunity for high-throughput screening of proapoptotic and antiapoptotic compounds and for target validation in vivo in both cell lines and transgenic animals.

Animals↗

PubMedDate not supplied

Molecular imaging of gene expression and efficacy following adenoviral-mediated brain tumor gene therapy.

Cancer gene therapy is an active area of research relying upon the transfer and subsequent expression of a therapeutic transgene into tumor cells in order to provide for therapeutic selectivity. Noninvasive assessment of therapeutic response and correlation of the location, magnitude, and duration of transgene expression in vivo would be particularly useful in the development of cancer gene therapy protocols by facilitating optimization of gene transfer protocols, vector development, and prodrug dosing schedules. In this study, we developed an adenoviral vector containing both the therapeutic transgene yeast cytosine deaminase (yCD) along with an optical reporter gene (luciferase). Following intratumoral injection of the vector into orthotopic 9 L gliomas, anatomical and diffusion-weighted MR images were obtained over time in order to provide for quantitative assessment of overall therapeutic efficacy and spatial heterogeneity of cell kill, respectively. In addition, bioluminescence images were acquired to assess the duration and magnitude of gene expression. MR images revealed significant reduction in tumor growth rates associated with yCD/5-fluorocytosine (5FC) gene therapy. Significant increases in mean tumor diffusion values were also observed during treatment with 5FC. Moreover, spatial heterogeneity in tumor diffusion changes were also observed revealing that diffusion magnetic resonance imaging could detect regional therapeutic effects due to the nonuniform delivery and/or expression of the therapeutic yCD transgene within the tumor mass. In addition, in vivo bioluminescence imaging detected luciferase gene expression, which was found to decrease over time during administration of the prodrug providing a noninvasive surrogate marker for monitoring gene expression. These results demonstrate the efficacy of the yCD/5FC strategy for the treatment of brain tumors and reveal the feasibility of using multimodality molecular and functional imaging for assessment of gene expression and therapeutic efficacy.

Adenoviridae↗

PubMedDate not supplied

TRAIL and anti-tumor responses.

The therapeutic use of TRAIL as an inducer of tumor specific cell death prove to be an useful strategy to overcome resistant of cancer cells to conventional chemotherapeutic agents. Although five death receptors have been identified which bind TRAIL and a number of checkpoint involved in TRAIL pathway are known, the molecular mechanism underlying the resistant or sensitivity of normal/transformed cells remains poorly understood. The key to the clinical use of TRAIL is that normal cells are resistant to its cytotoxic activity and that it specifically targets cancer cells thus resulting in large therapeutic index. In spite of this observation, TRAIL will probably not be viable as single agent as there are numerous reports that have demonstrated the resistance of various tumor cells to TRAIL. The concept of combination therapy is therefore key for the use of TRAIL against tumors that are refractory to treatment with either agent alone. Results from preclinical studies on TRAIL have been very promising for cancer treatment; however, outcome from phase I/II clinical trials is eagerly awaited to assess its safety. Only time will tell whether the search for the Holy Grail for treatment of cancer will end with TRAIL?

Animals↗

PubMedDate not supplied

Imaging of proteolytic activity using a conditional cell surface receptor.

Programmed cell death (apoptosis) is a ubiquitous means utilized by multicellular organisms for elimination of unwanted cells during development and homeostasis. Dysregulated apoptosis is implicated in an array of clinical disorders including cancer, autoimmune diseases, neurodegenerative disorders, and ischemia. During programmed cell death, a series of proteases, known as caspases, with different specificities play crucial roles in the apoptotic process. Caspase-3, a group II cysteine aspartate protease, recognizes and cleaves substrates harboring the amino acid sequence aspartic acid-glutamic acid-valine-aspartic acid (DEVD), and it plays an important role in the terminal phase of apoptosis. Here we report the development of a novel imaging platform for sensing the activation of cellular proteases. A recombinant chimeric protein was constructed, composed of a cell-surface-targeted single-chain antibody (sFv) fused to a Golgi retention signal. The DEVD tetrapeptide sequence was included between the single-chain antibody and the Golgi retention signal as a caspase-3 protease cleavage site. When expressed in cultured cells this fusion protein was localized to Golgi bodies and was not detected on the cell surface. Induction of apoptosis resulted in cleavage of the fusion protein releasing the single-chain antibody from the Golgi retention signal in a caspase-dependent manner. As a result, in cells undergoing apoptosis the single-chain antibody was visualized at the cell surface by immunofluorescence microscopy. The expression of sFv on the surface of cells in a protease-dependent manner provides a unique opportunity for real-time imaging through the use of targeted nanoparticles. This methodology may provide for a multimodal noninvasive real-time imaging of apoptosis and a new opportunity for high-throughput screening of cell-death-modulating therapeutic agents.

Animals↗