In this issue two groups, Read et al. (see p. 29) and Joki et al. (see p. 35) describe a strategy for sustained delivery of the anti-angiogenic agent, endostatin, to tumors. Both groups engineered cells to express endostatin and then encapsulated them in sodium alginate, forming beads, an arrangement that promotes exchange of nutrients and oxygen to the cells, and protects them from tissue rejection. Both groups showed that the beads reduced tumor growth in vivo, using animal models of gliomas, a highly vascularized and invasive form of brain tumor. Read et al. implanted beads and tumor cells intracranially in rats, and Joki et al. implanted beads next to existing tumors growing under the skin of mice. Both groups subsequently observed reduced tumor growth, large areas of necrosis, and apoptosis in the endostatin-treated tumors. Given that continuous delivery may be key to the antitumor efficacy of endostatin, such cell-based approaches could hold promise for cancer therapy (see also p. 20).