A: Combination of Anticancer Drugs and Gene Therapy for the Arrest of Brain Tumors
Malignant brain tumors or glioblastomas are highly invasive and life threatening. The prognosis for patients diagnosed with brain tumor is very poor, with a mean survival rate of 12-18 months even after the combination regimens of surgery, radiation and chemotherapy. The conventional dose of traditional anticancer drugs induces cell death in normal cells also causing undesirable, often debilitating side effects. Dr. George's research focuses on the selective killing of brain cancer cells using a combination of gene therapy and a low dose of anticancer drugs which induce tumor cell differentiation and apoptosis. This unique treatment modality affects normal cells minimally because low doses of anticancer drugs induce selective differentiation of cancer cells due to the immunosuppression in tumor cells and heterogeneity. Tumor cells evade immunosurveillance through active participation in inducing tumor-specific immunosuppression, which facilitates selective killing of tumor cells. In addition, Dr. George's research also concentrates on restoration of lost or mutated tumor suppressor genes, which facilitates the effect of low doses of anticancer agents.
RNA interference through small interfering (siRNA) is a powerful technique to knockdown a gene’s message and subsequently the protein level of the targeted gene. The application of siRNAs to prevent cell invasion, angiogenesis and tumor progression is not yet explored fully. Matrix metalloproteinases (MMPs), especially MMP-9 plays a crucial role in the degradation of the extracellular matrix and thus promotes cell invasion and angiogenesis. Cancer cells evade apoptosis through upregulation of antiapoptotic molecules. Knockdown of cell survival signaling molecules such as Bcl-2 and survivin at the mRNA level triggers apoptosis in cancer cells and decreases both cell proliferation and tumor invasion. The siRNA mediated knockdown of gene messages for several molecules, such as MMP-9 and survivin, which are pivotal for tumor cell invasion, angiogenesis and tumor progression, offers potential therapeutic strategy for malignant brain tumors (Neuro-Oncology 2010; 12:1088-1101 PDF, Glioblastoma; Springer Science 2010; 282-298 PDF, Clinical Cancer Research 2009; 15:7186-7195 PDF, Journal of Cellular and Molecular Medicine 2009; 13:4205-4218 PDF, Clinical Cancer Research 2007; 13:3507-3517 PDF).
B: Molecular Pathogenesis of Hepatic Fibrosis and Applications of Gene Therapy
Hepatic fibrosis refers to the accumulation of connective tissue proteins, especially interstitial collagens, in the extracellular matrix of liver parenchyma. Hepatic fibrosis is a dynamic process and involves the interplay of different cell types in the hepatic tissue. Several factors, such as oxidative stress, toxins, viruses, necrosis, and growth factors, are responsible for the activation and transformation of hepatic stellate cells. A cascade of signaling and transcriptional events in the activated stellate cells underlies the pathogenesis of hepatic fibrosis. Regulation of the several steps involved in the activation and transformation of hepatic stellate cells offers a potential therapeutic target for the arrest of hepatic fibrosis and liver cirrhosis.
Connective Tissue Growth Factor (CTGF) is a multifunctional cytokine involved in the regulation of cell growth and tissue remodeling. CTGF plays a key role in the pathogenesis of hepatic fibrosis and stimulates the differentiation of restive hepatic stellate cells into myofibroblasts, which leads to production of more CTGF. CTGF also stimulates production of collagens, fibronectin, and laminin, the predominant molecules of present in extracellular matrix of liver.
Transforming growth factor-β1 (TGF-β1) is involved in various pathophysiological processes, including cell proliferation, differentiation, angiogenesis, and fibrosis. TGF-β1 stimulates the synthesis of connective tissue components and inhibits extracellular matrix degradation through autocrine and paracrine mechanisms and performs a key role in the pathogenesis of hepatic fibrosis. TGF-β1 also plays a crucial role in triggering the cascade of events that culminates in production of CTGF, which causes formation of nodular fibrosis in the liver. Silencing the upregulation of both CTGF and TGF-β1 using small interfering RNAs (siRNAs) or microRNAs (miRNAs) offers a promising therapeutic strategy for the prevention and treatment of hepatic fibrosis (Chemico-Biological Interactions 2011; 193: 225-231 PDF, Gene Therapy 2007:14;790-803 PDF).
C: Tissue Engineering and Regenerative Medicine Involving Stem Cells
The use of tissue engineered biological substitutes employing living cells is emerging as an alternative to conventional tissue or organ transplantation. Using this technology, tissue loss or organ failure can be treated by implantation of an engineered biological substitute that is either functional at the time of implantation or has the potential to integrate and form the expected functional tissue or organ at a later stage. Three dimensional (3-D) cell cultures on biodegradable scaffolds are the basis of tissue engineering, where the specific cells can grow and multiply into a structure similar to tissues or organs in the living body. Collagen-hyaluronan-based biodegradable scaffolds are an excellent substratum for cell adhesion, differentiation and proliferation. The application of biodegradable 3-D scaffolds in the field of tissue engineering and regenerative medicine is highly promising.
Adult mesenchymal and cord blood stem cells are pluripotent, with the ability to differentiate into multi-lineage cells such as neurons, adipocytes, chondrocytes or osteoblasts when cultured in a special media with specific growth factors. The differentiated cells on a 3-D scaffold have the potential to form a variety of mesenchymal tissues such as cartilage, tendon, ligament, muscle or adipose tissue. Surgical implantation of such artificial organs derived from human stem cells has the potential to replace the impaired or damaged tissue or organ. The 3-D culture of hepatocytes on a specially designed collagen scaffold offers a method to develop a functional artificial liver. Identification and isolation of pluripotent stem cells and subsequent injection into the human body could regenerate the impaired or damaged tissue or organ. Isolation of embryonic or adult human stem cells for β-cells of pancreas and subsequent injection into the site could rejuvenate islets of Langerhans and start insulin production in diabetic patients (Journal of Biomedical Materials Research 2008; 87A:1103-1111 PDF, Biotechnology and Bioengineering 2006; 95:404-411 PDF).