Exosomal long noncoding RNA LNMAT2 promotes lymphatic metastasis in bladder cancer

Abstract

Patients with bladder cancer (BCa) with clinical lymph node (LN) metastasis have an extremely poor prognosis. VEGF-C has been demonstrated to play vital roles in LN metastasis in BCa. However, approximately 20% of BCa with LN metastasis exhibits low VEGF-C expression, suggesting a VEGF-C–independent mechanism for LN metastasis of BCa. Herein, we demonstrate that BCa cell–secreted exosome-mediated lymphangiogenesis promoted LN metastasis in BCa in a VEGF-C–independent manner. We identified an exosomal long noncoding RNA (lncRNA), termed lymph node metastasis-associated transcript 2 ( LNMAT2 ), that stimulated human lymphatic endothelial cell (HLEC) tube formation and migration in vitro and enhanced tumor lymphangiogenesis and LN metastasis in vivo. Mechanistically, LNMAT2 was loaded to BCa cell–secreted exosomes by directly interacting with heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1). Subsequently, exosomal LNMAT2 was internalized by HLECs and epigenetically upregulated prospero homeobox 1 (PROX1) expression by recruitment of hnRNPA2B1 and increasing the H3K4 trimethylation level in the PROX1 promoter, ultimately resulting in lymphangiogenesis and lymphatic metastasis. Therefore, our findings highlight a VEGF-C–independent mechanism of exosomal lncRNA-mediated LN metastasis and identify LNMAT2 as a therapeutic target for LN metastasis in BCa.