N6-methyladenosine-modified circ_0081069: an effective approach to modulate breast cancer's tumor immune...

Circular RNA (circRNA) has been recognized as critical regulator in cancer progression. However, the mechanisms of circ_0081069 in breast cancer (BC) remain understood. The study was designed to elucidate the pathological significance and mechanism of circ_0081069 in BC.

The expression of circ_0081069 was investigated in BC tissues and cell via qRT-PCR. CCK-8 and Transwell were carried out for assessing cell viability and invasion. After transfection, the expression of circ_0081069, microRNA (miR)-1286 and E2F4 were manipulated, and the mechanism in BC were explored by bioinformatic predication, luciferase reporter assay and RIP assay. The m⁶A modification was confirmed via MeRIP assay. Granzyme, IFN-γ, TNF-α and PD-L1 levels were determined using ELISA and western blot. Xenograft tumor model was established to detect circ_0081069 functions in vivo.

Circ_0081069 was markedly upregulated in BC tissues (n = 60) and cells, which was correlated with poor patient prognosis. Knockdown of circ_0081069 restrained MDA-MB-231 and BT549 cells viability and invasion. Moreover, Granzyme, TNF-α, IFN-γ and PD-L1 levels were elevated in the co-cultured BC and CD8⁺ T cells. Mechanistically, circ_0081069 was a sponge for miR-1286, leading to up-regulation of E2F4. The inhibitory functions of circ_0081069 knockdown in BC pathological behaviors and tumor microenvironment were reversed by miR-1286 inhibition. METTL3 silence inhibited cell viability, invasion and tumor microenvironment by stabilizing circ_0081069. Furthermore, circ_0081069 knockdown suppressed BC cell proliferation and regulated immune microenvironment in vivo.

m⁶A-modified circ_0081069 facilitated BC progression and tumor microenvironment via the miR-1286/E2F4 regulatory axis.