Engineered cytokine/antibody fusion proteins improve delivery of IL-2 to pro-inflammatory cells and promote antitumor activity.

Progress in cytokine engineering is driving therapeutic translation by overcoming the inherent limitations of these proteins as drugs. The interleukin-2 (IL-2) cytokine harbors great promise as an immune stimulant for cancer treatment. However, the cytokine's concurrent activation of both pro-inflammatory immune effector cells and anti-inflammatory regulatory T cells, its toxicity at high doses, and its short serum half-life have limited clinical application. One promising approach to improve the selectivity, safety, and longevity of IL-2 is complexation with anti-IL-2 antibodies that bias the cytokine towards the activation of immune effector cells (i.e., effector T cells and natural killer cells). Although this strategy shows therapeutic potential in preclinical cancer models, clinical translation of a cytokine/antibody complex is complicated by challenges in formulating a multi-protein drug and concerns about complex stability. Here, we introduce a versatile approach to designing intramolecularly assembled single-agent fusion proteins (immunocytokines, ICs) comprising IL-2 and a biasing anti-IL-2 antibody that directs the cytokine's activities towards immune effector cells. We establish the optimal IC construction and further engineer the cytokine/antibody affinity to improve immune biasing function. We demonstrate that our IC preferentially activates and expands immune effector cells, leading to superior antitumor activity compared to natural IL-2 without inducing toxicities associated with IL-2 administration. Collectively, this work presents a roadmap for the design and translation of immunomodulatory cytokine/antibody fusion proteins.

The Enrichment of Survivin in Exosomes from Breast Cancer Cells Treated with Paclitaxel Promotes Cell Survival and Chemoresistance.

The generation and release of membrane-enclosed packets from cancer cells, called extracellular vesicles (EVs), play important roles in propagating transformed phenotypes, including promoting cell survival. EVs mediate their effects by transferring their contents, which include specific proteins and nucleic acids, to target cells. However, how the cargo and function of EVs change in response to different stimuli remains unclear. Here, we discovered that treating highly aggressive MDAMB231 breast cancer cells with paclitaxel (PTX), a chemotherapy that stabilizes microtubules, causes them to generate a specific class of EV, namely exosomes, that are highly enriched with the cell survival protein and cancer marker, Survivin. Treating MDAMB231 cells with a variety of other chemotherapeutic agents, and inhibitors that block cell growth and survival, did not have the same effect as PTX, with the exception of nocodazole, another inhibitor of microtubule dynamics. Exosomes isolated from PTX-treated MDAMB231 cells strongly promoted the survival of serum-starved and PTX-treated fibroblasts and SKBR3 breast cancer cells, an effect that was ablated when Survivin was knocked-down from these vesicles using siRNA. These findings underscore how the enrichment of a specific cargo in exosomes promotes cell survival, as well as can potentially serve as a marker of PTX resistance.