Progress and challenges for cell encapsulation in brain tumour therapy

Cell encapsulation provides a method to circumvent the host immune system by encapsulating cells or tissues in immunoisolating, semipermeable membranes before implantation. The technology has been widely studied with an aim of developing bio-organs transplantable into patients without the need of immunosuppression, and in cancer therapy, the principle of cell encapsulation may be further exploited. Encapsulated recombinant cells represent factories or bioreactors for the production of therapeutic proteins. By implanting the bioreactors in the vicinity of the tumour, long-term local de novo delivery of the therapeutic proteins may be achieved. Malignant brain tumours such as glioblastoma multiforme (GBM) remain highly lethal neoplasms, refractory to current therapies. Researchers and medical professionals are working on developing translational therapies to combat these aggressive tumours. Numerous clinical trials on gene therapy for glioma patients have been conducted over the last decade, but the results have largely been disappointing. Cell encapsulation represents an alternative method for local delivery of therapeutic proteins with antineoplastic properties to glioma patients. The concept has not yet reached clinical trials, but encouraging results have been achieved in rats bearing gliomas when implanting endostatin-secreting encapsulated cells into the rat brain. This review primarily focuses on the recent progress that has been made with cell encapsulation technology. In addition, the challenges this field faces before clinical application in brain tumour patients is discussed.