This study presents a novel approach for targeted cancer therapy using prodrug-conjugated tumor-seeking commensals. The researchers identified an oral commensal strain of Lactobacillus plantarum (Lp) that specifically binds to nasopharyngeal carcinoma (NPC) cells via OppA-mediated recognition of heparan sulfate. They engineered Lp to load anticancer prodrugs, which are activated by tumor-associated biosignals to release SN-38, a chemotherapy compound, near NPC cells. In vitro experiments showed that the prodrug-loaded microbes significantly increased the potency of SN-38 against NPC cell lines, up to 10-fold. In a mouse xenograft model, intravenous injection of the engineered Lp led to bacterial colonization in NPC tumors and a 67% inhibition in tumor growth, enhancing the efficacy of SN-38 by 54%. Conventional chemotherapy is the primary mode of cancer treatment but is often associated with poor bioavailability, severe systemic toxicity, and low patient tolerance. Prodrugs have been investigated as an alternative approach for targeted cancer therapy, as they can be converted to active drugs in the tumor microenvironment. However, current prodrug strategies have limited target specificity, as TME cues may not be clearly distinguishable from normal tissue, leading to off-target effects. The conjugation of tumor-targeting carriers can improve treatment specificity, but the macromolecular nature of these carriers often complicates pharmacokinetics, affecting biodistribution, metabolism, and clearance. To overcome these limitations, the study harnesses the intrinsic interactions between bacteria and cancer cells within the tumor microbiome for precise prodrug administration. The researchers identified and characterized a commensal microbe with cancer-binding capabilities and engineered it to deliver prodrugs to specific cancer sites. The prodrug was conjugated to the bacterial vector through chemical linkers to ensure site-specific release of the native drug. The engineered Lp strain showed substantial synergy with the loaded prodrug, resulting in a reduction of up to 10-fold in the half maximal inhibitory concentration (IC50) required for SN-38. In an NPC mouse xenograft model, the delivery of prodrugs through engineered Lp led to a 67% inhibition in tumor growth, significantly enhancing the efficacy of SN-38 by 54%. The study also demonstrated that the OppA proteins in Lp play a crucial role in binding to heparan sulfate on cancer cells. The researchers identified Lp_0018 as a key OppA protein with high heparan sulfate binding affinity. They further developed a prodrug-carrying Lp strain, Lp-Sav, which was engineered to display tetramer streptavidin on its surface, enabling the surface loading of biotinylated prodrugs. The prodrugs were designed to release SN-38 in response to tumor-associated biosignThis study presents a novel approach for targeted cancer therapy using prodrug-conjugated tumor-seeking commensals. The researchers identified an oral commensal strain of Lactobacillus plantarum (Lp) that specifically binds to nasopharyngeal carcinoma (NPC) cells via OppA-mediated recognition of heparan sulfate. They engineered Lp to load anticancer prodrugs, which are activated by tumor-associated biosignals to release SN-38, a chemotherapy compound, near NPC cells. In vitro experiments showed that the prodrug-loaded microbes significantly increased the potency of SN-38 against NPC cell lines, up to 10-fold. In a mouse xenograft model, intravenous injection of the engineered Lp led to bacterial colonization in NPC tumors and a 67% inhibition in tumor growth, enhancing the efficacy of SN-38 by 54%. Conventional chemotherapy is the primary mode of cancer treatment but is often associated with poor bioavailability, severe systemic toxicity, and low patient tolerance. Prodrugs have been investigated as an alternative approach for targeted cancer therapy, as they can be converted to active drugs in the tumor microenvironment. However, current prodrug strategies have limited target specificity, as TME cues may not be clearly distinguishable from normal tissue, leading to off-target effects. The conjugation of tumor-targeting carriers can improve treatment specificity, but the macromolecular nature of these carriers often complicates pharmacokinetics, affecting biodistribution, metabolism, and clearance. To overcome these limitations, the study harnesses the intrinsic interactions between bacteria and cancer cells within the tumor microbiome for precise prodrug administration. The researchers identified and characterized a commensal microbe with cancer-binding capabilities and engineered it to deliver prodrugs to specific cancer sites. The prodrug was conjugated to the bacterial vector through chemical linkers to ensure site-specific release of the native drug. The engineered Lp strain showed substantial synergy with the loaded prodrug, resulting in a reduction of up to 10-fold in the half maximal inhibitory concentration (IC50) required for SN-38. In an NPC mouse xenograft model, the delivery of prodrugs through engineered Lp led to a 67% inhibition in tumor growth, significantly enhancing the efficacy of SN-38 by 54%. The study also demonstrated that the OppA proteins in Lp play a crucial role in binding to heparan sulfate on cancer cells. The researchers identified Lp_0018 as a key OppA protein with high heparan sulfate binding affinity. They further developed a prodrug-carrying Lp strain, Lp-Sav, which was engineered to display tetramer streptavidin on its surface, enabling the surface loading of biotinylated prodrugs. The prodrugs were designed to release SN-38 in response to tumor-associated biosign