CELLS ENCAPSULATED IN ALGINATE: A POTENTIAL SYSTEM FOR DELIVERY OF RECOMBINANT PROTEINS TO MALIGNANT BRAIN TUMOURS TRACY-ANN READ, $ * VIDAR STENSVAAG, $ HARALD VINDENES, % ELLING ULVESTAD, % ROLF BJERKVIG $ and FRITS THORSEN } $Department of Anatomy and Cell Biology, University of Bergen, Bergen, Norway; %Department of Microbiology and Immunology, The Gade Institute, Haukeland University Hospital, Bergen, Norway; }Department of Radiophysics, Haukeland University Hospital, Bergen, Norway AbstractÐGrowth and progression of malignant brain tumours occurs in a micromilieu consisting of both tumour and normal cells. Several proteins have been identi®ed with the potential of interfering directly with tumour cells or with the neovascularisation process, thereby inhibiting tumour growth. A continuous delivery of such inhibitory proteins to the tumour microenvironment by genetically engin- eered cells could theoretically be of considerable therapeutic importance. In this study we have investi- gated the growth characteristics of cells encapsulated in alginate, which represents a potential delivery system for recombinant proteins that may have antitumour eects. Three dierent cell lines, NHI 3T3, 293 and BT4C were encapsulated in alginate, which is an immuno-isolating substance extracted from brown seaweed. The encapsulated cells were observed at speci®c intervals during a 4-month period after in vitro propagation and as transplants into the cortex of BD-IX rats. Morphological studies showed that encapsulated cells proliferated and formed spheroids within the alginate in the in vitro cultures and after implantation into the brain. Even after 4 months in vivo a substantial amount of living cells were observed within the alginate beads. A vigorous in®ltration of mononuclear cells was observed in the brain bordering the alginate beads, one week after implantation. However, there was a gradual decrease of mononuclear cells at the border zone beyond the ®rst week of implantation. The majority of in¯am- matory cells were reactive microglia and invading monocytes, as veri®ed by immunohistochemistry. The data further shows that alginate encapsulated cells can be frozen in liquid N 2 and will retain their viabi- lity and proliferative capacity. # 1999 Published by Elsevier Science Ltd on behalf of ISDN. All rights reserved. Key words: alginate, encapsulation, producer cells, brain tumours. INTRODUCTION Oncogenesis involves an accumulation of somatic mutations that alter the cell's geno- and phenotype, leading to a breakdown of mechanisms controlling normal cell growth and dierentiation. 4 The progression of glial tumours is characterised by cell growth, accompanied by a diuse in®ltration of tumour cells into the surrounding brain tissue. 20,21 The progression depends on an adequate nutrient supply mediated by an ongoing neovascularisation process, 8 in addition to a number of growth factors and macromolecules supplied by both tumour and host cells. 21,26 It is commonly acknowledged that several of the growth factors that control cell proliferation are shared by tumour cells and endothelial cells while others, such as vascular endothelial growth factors (VEGF's), are solely associated with endothelial cells. Furthermore, since migrating cells show little tendency to proliferate, it appears that the tumour cell invasion process is biologically distinct from the proliferative process. The progression of the disease is therefore dependent on two separate biological compartments. 2 However, as shown in Fig. 1, there is a large degree of cross-talk between the cell invasion and cell proliferation compartments. For instance, the invasive process depends on a number of extracellular matrix Int. J. Devl Neuroscience, Vol. 17, No. 5±6, pp. 653±663, 1999 # 1999 Published by Elsevier Science Ltd on behalf of ISDN. All rights reserved. Printed in Great Britain 0736-5748/99 $20.00 + 0.00 PII: S0736-5748(99)00052-0 www.elsevier.com/locate/ijdevneu *To whom correspondence should be addressed. Tel:. +47-55-58-6373; E-mail: t-a.read@pki.uib.no 653