Stem cell technology gives hope of effective treatment for a variety of malignant and non-malignant diseases through the rapid developing field that combines the efforts of cell biologists, geneticists, and clinicians. Stem cells are defined as totipotent progenitor cells capable of self-renewal and multi-lineage differentiation. Stem cells survive well and show steady division in culture which then causes them the ideal targets for vitro manipulation. Research into solid tissue stem cells has not made the same progress as haematopoietic stem cells because of the difficulty of reproducing the necessary and precise 3D arrangements and tight cell-cell and cell-extracellular matrix interactions that exist in solid organs. Yet, the ability of tissue stem cells to assimilate into the tissue cytoarchitecture under the control of the host microenvironment and developmental cues, makes them ideal for cell replacement therapy.
The development of gene therapy strategies for treatment of intra-cranial tumors offer much promise, and has shown to be successful in the treatment of some dogs; although research in this area is still at an early stage. Using conventional techniques, brain cancer is difficult to treat because it spreads so rapidly. Researchers at the Harvard Medical School transplanted human neural stem cells into the brain of rodents that received intracranial tumours. Within days, the cells migrated into the cancerous area and produced cytosine deaminase, an enzyme that converts a non-toxic pro-drug into a chemotheraputic agent. As a result, the injected substance was able to reduce the tumor mass by 81 percent. The stem cells neither differentiated nor turned tumorigenic.
Some researchers believe that the key to finding a cure for cancer is to inhibit proliferation of cancer stem cells. Accordingly, current cancer treatments are designed to kill cancer cells. However, conventional chemotherapy treatments cannot discriminate between cancerous cells and others. Stem cell therapies may serve as potential treatments for cancer. Research on treating lymphoma using adult stem cells is underway and has had human trials. Essentially, chemotherapy is used to completely destroy the patients own lymphocytes, and stem cells injected, eventually replacing the immune system of the patient with that of the healthy donor.