新出现的化疗和放疗耐药性加剧了癌症风险，需要新的治疗策略。尽管针对促癌基因的 RNA 疗法非常有效，但肿瘤特异性递送仍然是实施这一有价值工具的障碍。在这项研究中，我们使用 4T1 小鼠乳腺癌模型报告了一种色氨酸营养缺陷型鼠伤寒沙门氏菌菌株作为具有肿瘤靶向能力的肿瘤治疗递送系统。 SiSo细胞上表达的受体结合癌抗原（RCAS1）是一种癌症特异性蛋白，可诱导外周淋巴细胞凋亡并赋予肿瘤免疫逃避作用。我们设计了针对 RCAS1 的长非编码反义 RNA (asRCAS1)，并由沙门氏菌使用非抗生素、营养缺陷型选择性真核表达质粒 pJHL204 进行递送。在体内肿瘤间传代后，JOL2888（ΔtrpA、ΔtrpE、Δasd asRCAS1）菌株在肿瘤中表现出高度的可持续性，但在健康器官中没有持续存在，从而证明了肿瘤特异性和安全性。通过蛋白质印迹和 qPCR 证实了 RCAS1 在肿瘤中的抑制作用。在小鼠中，JOL2888 治疗减少了肿瘤相关巨噬细胞，改善了 T 细胞群，引发了细胞介导的免疫，并抑制了促癌基因。因此，JOL2888 治疗使肿瘤体积显着减少了 80%，脾肿大减少了 30%，并完全阻止了肺转移。这些发现强调了色氨酸营养缺陷型沙门氏菌传递肿瘤治疗大分子的内在肿瘤靶向能力。© 2023 作者。

Emerging chemo- and radiotherapy resistance exacerbated the cancer risk and necessitated novel treatment strategies. Although RNA therapeutics against pro-oncogenic genes are highly effective, tumor-specific delivery remains a barrier to the implementation of this valuable tool. In this study, we report a tryptophan-auxotrophic Salmonella typhimurium strain as an onco-therapeutic delivery system with tumor-targeting ability using 4T1 mice breast-cancer model. The receptor-binding cancer antigen expressed on SiSo cell (RCAS1) is a cancer-specific protein that induces the apoptosis of peripheral lymphocytes and confers tumor immune evasion. We designed a long non-coding antisense-RNA against RCAS1 (asRCAS1) and delivered by Salmonella using a non-antibiotic, auxotrophic-selective, eukaryotic expression plasmid, pJHL204. After in vivo tumor-to-tumor passaging, the JOL2888 (ΔtrpA, ΔtrpE, Δasd + asRCAS1) strain exhibited high sustainability in tumors, but did not last in healthy organs, thereby demonstrating tumor specificity and safety. RCAS1 inhibition in the tumor was confirmed by western blotting and qPCR. In mice, JOL2888 treatment reduced tumor-associated macrophages, improved the T cell population, elicited cell-mediated immunity, and suppressed cancer-promoting genes. Consequently, the JOL2888 treatment significantly decreased the tumor volume by 80%, decreased splenomegaly by 30%, and completely arrested lung metastasis. These findings highlight the intrinsic tumor-targeting ability of tryptophan-auxotrophic Salmonella for delivering onco-therapeutic macromolecules.© 2023 The Author(s).