Engineered probiotic <i>Bifidobacterium</i> for tumor-targeted pancreatic cancer therapy.

Lee, Jaehyun; Yang, Kaiting; Nowicki, Christina A; Liu, Wei; Li, Kangdi; Naccasha, Emile; Sun, Zhichen; Fu, Yang-Xin et al. · Sci Adv · 2026

basic_science · Level V

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Abstract

Pancreatic ductal adenocarcinoma (PDAC) presents a substantial challenge due to its resistance to cancer treatments. This limited efficacy is, in part, attributed to the immunosuppressive tumor microenvironment (TME), which impairs effector T (T<sub>eff</sub>) cell activity. Interleukin-2 (IL-2) is a key cytokine for T cell activation, but its therapeutic use is limited by a short half-life, systemic toxicity, and regulatory T (T<sub>reg</sub>) activation. To address this limitation, we engineered <i>Bifidobacterium longum</i>, a probiotic obligate anaerobe that selectively colonizes the TME, to continuously secrete Super-mutant IL-2 (SumIL-2), an engineered IL-2 variant that preferentially activates T<sub>eff</sub> cells over T<sub>reg</sub> cells, thereby delivering SumIL-2 selectively to the tumor (BifidoSumIL-2). Systemic administration of BifidoSumIL-2 significantly suppressed tumor growth in both subcutaneous tumors and orthotopic PDAC in mice, inducing an improved T<sub>eff</sub>/T<sub>reg</sub> ratio. Combining BifidoSumIL-2 with chemotherapy, radiation, and immunotherapy further restrained orthotopic PDAC growth, highlighting its therapeutic potential for difficult-to-treat cancers like PDAC.

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