Gap Junction Liposomes for Efficient Delivery of Chemotherapeutics to Solid Tumors

Chemotherapeutic delivery is limited by inefficient transport across cellular membranes. Here, we harness the cellular gap junction network to release therapeutic cargos directly into the cytosol. Specifically, cell-derived vesicles, termed connectosomes, contain gap junction transmembrane proteins that open a direct passageway to the cellular interior. Connectosomes were previously shown to substantially improve chemotherapeutic delivery in vitro. Here, we test connectosomes in vivo, using a murine breast tumor model. We demonstrate that connectosomes improve chemotherapeutic delivery to cellular targets within tumors by up to 16-fold, compared to conventional drug-loaded liposomes, suggesting an efficient alternative pathway for intracellular delivery.

Lysis of fresh murine mammary tumor cells by syngeneic natural killer cells and lymphokine-activated killer cells

We have compared the ability of natural killer (NK) cells from two substrains of C3H mice that differ with respect to their susceptibility to the development of mammary adenocarcinomas to lyse fresh syngeneic mammary tumor cells. Single cell suspensions of mammary tumors from retired breeder females were used as targets in 22-h 51Cr-release cytotoxicity assays with syngeneic NK cells. Tumor cell suspensions were prepared by enzymatic digestion of finely minced tissue followed by centrifugation through a discontinuous Percoll gradient. Effector cells were prepared by passing spleen cells over nylon wool followed by centrifugation through Percoll fraction 7. Syngeneic NK cells had significant levels of lysis against 5/8 tumors studied. NK cells from low risk animals (C3Heb/FeJ) consistently demonstrated greater cytotoxicity against tumor cell preparations than did effectors from the high tumor substrain (C3H/OuJ). Study of cytocentrifuge preparations stained with Wright-Giemsa revealed that the two substrains were identical with respect to the number of azurophilic granules present in the cytoplasm of their NK cells. We have also shown that lymphokine-activated killer (LAK) cells can be generated from splenocytes in C3H mice. While LAK cells from both substrains were capable of lysing fresh syngeneic mammary tumor cells in vitro, LAK cells from the animals at high risk for the formation of mammary adenocarcinomas had greater cytotoxicity against tumor cell suspensions than LAK cells from the low tumor substrain.