Junctional adhesion molecular 3 (JAM3) is a novel tumor suppressor and improves the prognosis in breast cancer brain metastasis via the TGF-β/Smad signal pathway

Abstract

Purpose The incidence of breast cancer brain metastasis (BCBM) is a deadly clinical problem, and exact mechanisms remain elusive. Junction adhesion molecule (JAM), a tight junction protein, is a key negative regulator of cancer cell invasion and metastasis. Methods Junction adhesion molecular 3 (JAM3) expression in breast cancer was analyzed by bioinformatics method and confirmed by PCR, western blot, and immunofluorescence (IF) in cell lines. The effect of exogenous expression of JAM3 through lentivirus vectors on invasion, adhesion, and apoptosis was verified using transwell assay and flow cytometer. Differentially expressed genes (DEGs) were detected by RNA sequence and verified by q-PCR and Western bot. The effect of silencing JAM3 using siRNA was assessed by adhesion assay. Kaplan-Meier analysis was applied to calculate the impact of JAM3 expression and classic clinicopathologic characteristics on survival. Results Bioinformatics analysis revealed that JAM3 expression was reduced in BCBM. Exogenous expression of JAM3 minimizes the ability to invade, adhesion and promotes apoptosis of breast cancer cells. Silencing JAM3 results in morphology-changing and recovering invasion and adhesion to ECMs and the TGF-β/Smad signal pathway may be involved. JAM3 predicts less metastasis and good survival in patients with BCBM. Statistical analysis examined the correlation between JAM3 expression in BCBM samples detected by IHC and the clinicopathological characteristics. Kaplan-Meier analysis indicated that a high expression level of JAM3 was associated with longer survival time. Conclusion JAM3 can serve as a key negative regulator of breast cancer cell invasion, apoptosis, and brain metastasis, which may be linked to the TGF/Smad signal pathway. JAM3 has been anticipated to be a promising biomarker in the diagnosis and prognosis of breast cancer.