Cancer is a prominent source of mortality globally, and the worldwide burden is rising¹. Live biotherapeutics for sustained delivery of anti-tumor agents have attracted increasing attention in oncology owing to the potential for improved therapeutic efficiency and limited side effects compared to traditional therapies such as chemotherapy and radiation². Specific bacteria such as Escherichia, Salmonella, Listeria, and Pseudomonas can selectively colonize hypoxic, immunosuppressive, and biochemically unique microenvironments within solid tumors^3-5, exhibiting inherent anti-tumor effects based on stimulation of the innate immune system or secretion of natural anti-tumor products⁶. 

For the reduced toxicity to normal tissues triggered by the over-production of therapeutic proteins by engineered bacteria, In 2024, our group developed therapeutically active engineered bacteria mediated by a sono-activatable integrated gene circuit based on the thermosensitive transcriptional repressor TlpA₃₉ (SINGER system)⁷, This system, with high sensitivity, modularity, and compatibility, allows rapid engineering of multiple payloads in response to US irradiation. However, the need for coupling agents and specialized sonographic equipment increases intervention complexity⁸, reducing clinical practicality. Moreover, the high temperatures required (42-45 °C) pose risks such as potential thermal damage to healthy tissues⁸ and unintended activation of endogenous thermo-responsive proteins⁹. 

Light serves as a compelling trigger to tune gene expression in bacteria¹⁰. Several blue light-activatable photoswitches have been constructed in bacteria to modulate gene expression based on photosensitive proteins from fungi and bacteria¹¹. However, the limited tissue penetration and potential phototoxicity of blue light hinder the in vivo applicability of blue light–activated photoswitches¹².

To overcome these shortcomings, we developed a near-infrared light-mediated PadC-based photoswitch (NETMAP) system based on a chimeric phytochrome-activated diguanylyl cyclase (PadC) and a cyclic diguanylate monophosphate (c-di-GMP)-responsive transcriptional activator MrkH (Fig. 1). Briefly, upon NIR light illumination (710 nm), the chimeric photoreceptor PadC converts intracellular guanosine triphosphate (GTP) into c-di-GMP¹³, allowing  the transcriptional activator MrkH to bind to its chimeric promoter P_mrkA and initiate target gene expression.

Fig. 1 The NETMAP system-mediated tumor therapy

The NETMAP system demonstrated robust activation of reporter gene expression (55-fold) upon NIR light illumination compared to darkness. NIR light-induced production of anti-tumor therapeutic proteins [CTLA-4 nanobody (CTLA-4nb), PD-L1 nanobody (PD-L1nb), Azurin, and Cytolysin A (ClyA)] from ∆XIV significantly inhibited tumor growth and improved the survival rate of mice in various murine tumor models by activating adaptive immunity or inducing apoptosis and lysis of tumor cells. For example, to better simulate clinical patient conditions, we established a patient-derived xenograft (PDX) model using clinically sourced colorectal cancer tissues. Following the injection of engineered oncolytic bacteria, NIR irradiation was applied continuously for nine days, with two hours of exposure per day. Tumor growth was significantly inhibited, and histological analysis further revealed extensive tumor necrosis in the treatment group (Fig. 2).

Fig. 2 NETMAP-mediated tumor therapy in a CRC PDX model

In conclusion, we have built an optogenetic platform integrated into an attenuated S. enteritidis strain, providing a potential strategy to explore combination therapies for various cancers.  We anticipate that NIR light-triggered live biotherapeutics should contribute to accurate and effective treatments across multiple diseases by providing customizable outputs and precise dosage control.

Our paper : Qiao, L. et al. Engineered bacteria for NIR light-inducible expression of cancer therapeutics. Nat. Cancer. (2025).

References

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