Butyrate-associated antiproliferative and antitumor effects of Eubacterium limosum KGMB01548 in colorectal cancer.

INTRODUCTION

Recent work has shown that Eubacterium limosum suppresses colorectal cancer (CRC), but the contribution and cellular actions of its short-chain fatty acids remain incompletely defined.

METHODS

We characterized E. limosum KGMB01548, a human gut isolate, and examined the antitumor activity of its cell-free culture supernatant (ElCFS).

RESULTS

ElCFS preferentially inhibited the proliferation of human HCT116 and murine CT26 CRC cells while having little effect on non-malignant CCD 841 CoN colonic cells. The activity persisted after heat and enzymatic treatments, and pH-dependent liquid-liquid extraction indicated that a small organic acid was a major bioactive component. High-performance liquid chromatography detected 13.77 mM butyrate and 23.33 mM acetate in ElCFS. At approximately the concentration delivered by 10% ElCFS, sodium butyrate (NaB; 1.3 mM) produced comparable antiproliferative activity, whereas sodium acetate did not, supporting butyrate as a major candidate contributor to ElCFS activity. ElCFS and approximately concentration-matched NaB increased histone H3 acetylation, consistent with histone deacetylase inhibition, and induced apoptosis, as evidenced by PARP and caspase-3 cleavage and p53 phosphorylation. Their antiproliferative effects were markedly attenuated under glucose-depleted conditions. In a CT26 syngeneic tumor model, peritumoral administration of ElCFS reduced tumor growth, indicating that secreted E. limosum metabolites retained local antitumor activity outside the intestinal route. Oral pre-administration of live E. limosum also reduced subsequent tumor burden. Furthermore, 16S rRNA gene profiling suggested modest changes in several putative short-chain-fatty-acid-producing taxa and in PICRUSt2-predicted butyrate-biosynthesis potential, without a major change in alpha diversity.

DISCUSSION: Together, these findings link E. limosum KGMB01548 to butyrate-associated histone acetylation, apoptosis, glucose-sensitive antiproliferative activity, and tumor suppression, supporting further investigation of this gut commensal and its secreted metabolites as microbiome-derived approaches for CRC control.