基因工程沙门氏菌靶向改变肿瘤相关巨噬细胞表型及沉默CCL18抑制乳腺癌转移的研究

Tumor associated macrophages (TAMs) play a crucial role in breast cancer progression. Studies have recently demonstrated that CCL18 released by breast TAMs promotes breast cancer invasion and metastasis. Basically, macrophages are specialized phagocytic cells that attack infectious bacteria. In turn, bacteria component LPS activates macrophages (M1) to destroy tumor. On the other hand, the understanding of bacteria as tumor-targeting vector and M1 macrophage activator has pushed experts to make much effort on bacteria-based cancer therapy, such as drug delivery system design or an adjuvant to traditional chemodrugs. However, clinically, bacetria toxicity to normal organs limits its application. Besides, most of bacteria were used to target cancer cells but not tumor niche, although the latter has pivotal role in cancer progression. We currently generated a salmonella bacterial vector that not only specifically targets tumor, but also be able to proliferate inside tumor spontaneously, while decreases or disappears in normal organs over time. This vector can deliver shRNA to targeting cells. In this proposal, we will egineer salmonella vector to encode CCL18 shRNA, then use it to attract TAMs in tumor niche and silence CCL18 expression, further, to block the metastasis-promoting pathway. Also, we expect this kind of bacteria which contains LPS activates or redirects TAM to M1 phenotype that would be favorable for cancer treatment. Therefore, using this bacteria vector, we could inhibit tumor metastasis and kill primary tumor simultaneously. Our study is expected to improve the bio-safety and effectiveness of genetically engineered bacteria-mediated gene therapy, as well as to promote clinical application. It would be a major breakthrough in the field of cancer biotherapy.

乳腺癌微环境中的肿瘤相关巨噬细胞（TAM）对乳腺癌的转移有重要作用，研究发现TAM分泌CCL18促进乳腺癌侵袭和转移。而且由于巨噬细胞特异性趋化和吞噬细菌，细菌的成分LPS激活巨噬细胞（M1型）有效的杀伤肿瘤。基于对巨噬细胞活化功能的重要作用和在实体瘤中的聚集特性，细菌在肿瘤治疗研究已经成为热点，但对正常组织的毒性局限了它的临床应用。前期我们基因工程改造的沙门氏菌载体，具有正常组织低分布（甚至不分布）和肿瘤组织高分布的特点，且可以编码携带shRNA沉默靶基因表达。本实验我们拟运用改造后的细菌载体编码CCL18 shRNA靶向沉默乳腺癌微环境TAM的CCL18，阻断TAM促进乳腺癌转移的通路；进而利用细菌本身激活或逆转TAM为M1型，"双管齐下"既抑制转移又杀伤肿瘤。我们的研究有望提高基因工程改造菌介导的基因治疗的生物安全和有效性，实现临床规模化应用，将是肿瘤生物治疗领域的重大突破。

乳腺癌微环境中的肿瘤相关巨噬细胞（TAM）对乳腺癌的转移具有重要作用，而作为专业吞噬细胞的巨噬细胞对细菌有趋向性和特异吞噬性，而细菌组成成分LPS激活的巨噬细胞（M1型）可以杀伤肿瘤。在本研究中，我们通过基因工程改造出的沙门氏细菌载体，具有正常组织低分布（甚至不分布）和肿瘤组织高分布的特性，且可以编码携带shRNA沉默靶基因表达。为抑制乳腺癌转移，研究细菌在乳腺癌免疫治疗中的作用，我们成功运用改造后的细菌载体将TAM巨噬细胞变为M1型，使其可靶向乳腺癌微环境中的TAM，变TAM为M1，从而杀伤乳腺癌细胞。同时我们验证了在免疫完整的小鼠中，改造后的沙门氏菌同样具有抑制乳腺癌生长的作用。在寻找靶向药物方面，我们研究了抗肿瘤药物laromustine的裂解产物异氰酸甲酯其抗肿瘤作用部分是通过干预肿瘤血管发生而得以实现的，这为后续通过基因工程菌携带异氰酸甲酯或抗血管生成因子靶向杀伤乳腺癌提供了前期基础。