Prox1 Is Linked to Metastasis and Poor Prognosis by Promoting Lymphangiogenesis in Melanoma.

Purpose: The purpose of this study is to investigate the role of Prox1 in the progression of cutaneous melanoma (CMM) and its relationship with lymphatic metastasis. Methods and Results: By analyzing the data from the Cancer Genome Atlas (TCGA), we found that the expression of Prox1 and LYVE1 was significantly upregulated in the metastatic melanoma group. Additionally, elevated levels of Prox1 were associated with shorter survival times. Correlation analysis demonstrated a significant relationship between Prox1 and markers associated with lymphangiogenesis, including LYVE1, FLT4, FOXC2, and ANGPT2. A clinical study involving 32 cases of CMM was conducted to analyze Prox1 expression and its relationship with lymphangiogenesis and clinicopathological characteristics. Research revealed that Prox1 was expressed significantly higher in patients with lymph node (LN) metastasis and in those classified as stage 3C-4. Additionally, the density of lymphatic vessels(LVD) in the LN metastasis group and the stage 3C-4 group was markedly higher than in the group without lymph node metastasis and in the stage 0-3B group. Furthermore, Breslow thickness was found to correlate with both Prox1 expression and LVD. Prox1-positive expression was associated with increased LVD. Further investigation was conducted on the role of Prox1 in the CMM cell line A375 and its derived exosomes. Exosomes were collected from CMMnc and CMMshProx1 to verify the changes in Prox1 expression, respectively. It was observed that the proliferation, migration, and tube formation abilities of human lymphatic endothelial cells(HLECs) diminished with the downregulation of Prox1. Additionally, VEGFR3 activation was reduced in HLECs following the reduction of Prox1. Conclusion: Prox1 played an important role in promoting cell proliferation, migration, and lymphangiogenesis, which is related to tumor metastasis and poor prognosis. These results indicated the potential importance of Prox1 as a biomarker, which is expected to lead to the development of a new insight for anti-tumor therapy.