The influence of Lactobacillus johnsonii on tumor growth and lymph node metastasis in papillary thyroid carcinoma.

Lymph node metastasis (LNM) is a key factor in the prognosis of papillary thyroid carcinoma (PTC). This study explores the effect of intratumoral bacteria on LNM in PTC. The intrathyroidal microbiome is analyzed in 55 PTC patients by 16S rRNA gene sequencing. The CCK8 and Transwell assays determine the impact of bacteria on the proliferation and migration abilities of PTC cells. Xenograft tumor and bacterial colonization experiments are carried out using nude mice. We show that Lactobacillus is significantly decreased in PTC lesions from patients with LNM. Lactobacillus johnsonii (L. johnsonii) suppresses the proliferation and migration capability of PTC cells in vitro and in vivo. Bacterial gut colonization of L. johnsonii increases its abundance in tumors and inhibits PTC growth and LNM. These findings suggest that L. johnsonii can be harnessed for the development of innovative therapeutic strategies for PTC.