PDSS2-Del2, a new variant of PDSS2, promotes tumor cell metastasis and angiogenesis in hepatocellular carcinoma via activating NF-κB.

Hepatocellular carcinoma (HCC) is among the leading causes of cancer-related mortality worldwide. Our previous study identified a novel alternative splicing variant of prenyl diphosphate synthase subunit 2 (PDSS2) in HCC characterized by a deletion of exon 2, named PDSS2-Del2, which is devoid of the tumor-suppressive function of full-length PDSS2 (PDSS2-FL). To better understand the clinical significance of PDSS2-Del2, we performed a BaseScope™ assay on an HCC tissue microarray and found that positive staining for PDSS2-Del2 predicted a worse overall survival in patients with HCC (P = 0.02). PDSS2-Del2 levels correlated significantly with microvessel counts in HCC tumor tissues. Importantly, PDSS2-Del2 overexpression functionally promoted HCC metastasis, as demonstrated by in vitro and in vivo migration assays. In vivo assays also demonstrated that PDSS2-Del2 increased angiogenesis in xenografts. Furthermore, we discovered that elevated PDSS2-Del2 expression in HCC tumor cells decreased fumarate levels and activated the canonical nuclear factor-κB pathway. The epithelial-to-mesenchymal transition (EMT) and WNT/β-catenin signaling pathways were also activated by overexpression. Dimethyl fumarate (DMF), a fumaric acid ester, effectively reduced the metastasis induced by PDSS2-Del2 as observed with in vivo spleen-liver metastasis animal experiments. DMF is a prescribed oral therapy for multiple sclerosis and it might be a potential treatment for metastasis of patients with HCC. Early clinical trials are needed to validate its potential in this context.