Protein arginine methyltransferases (PRMT) catalyze protein arginine methylation and play an important role in many biological processes. Aberrant PRMT expression in tumor cells has been documented in several common cancer types; however, its precise contribution to hepatocellular carcinoma (HCC) cell invasion and metastasis is not fully understood. In this study, we identified a new oncogene, PRMT9, whose overexpression strongly promotes HCC invasion and metastasis. PRMT9 expression was detected more frequently in HCC tissues than in adjacent noncancerous tissues. PRMT9 overexpression was significantly correlated with hepatitis B virus antigen (HBsAg) status, vascular invasion, poor tumor differentiation and advanced TNM stage. Patients with higher PRMT9 expression had a shorter survival time and higher recurrence rate. PRMT9 expression was an independent and significant risk factor for survival after curative resection. Functional studies demonstrated that PRMT9 increased HCC cell invasion and lung metastasis. Knocking down PRMT9 with short hairpin RNA (shRNA) inhibited HCC cell invasion. Further investigations found that PRMT9 increased cell migration and invasion through epithelial‐mesenchymal transition (EMT) by regulating Snail expression via activation of the PI3K/Akt/GSK‐3β/Snail signaling pathway. In clinical HCC samples, PRMT9 expression was positively associated with Snail expression and was negatively associated with E‐cadherin expression. In conclusion, our study demonstrated that PRMT9 is an oncogene that plays an important role in HCC invasion and metastasis through EMT by regulating Snail expression via activation of the PI3K/Akt/GSK‐3β/Snail signaling pathway. Thus, PRMT9 may serve as a candidate prognostic biomarker and a potential therapeutic target.

Both phosphatase of regenerating liver-3 (PRL-3) and tumor-associated macrophages (TAM) influence cancer progression. Whether PRL-3 plays a critical role in colorectal cancer invasion and metastasis by inducing TAM infiltration remains unclear. In the current study, we investigated the effects of chemokine ligand 26 (CCL26) on TAM infiltration and colorectal cancer invasion and the underlying mechanism in colorectal cancer cells by overexpressing or silencing PRL-3. We found that PRL-3 upregulated CCL26 expression correlatively and participated in cell migration, according to the results of gene ontology analysis. In addition, IHC analysis results indicated that the PRL-3 and CCL26 levels were positively correlated and elevated in stage III and IV colorectal cancer tissues and were associated with a worse prognosis in colorectal cancer patients. Furthermore, we demonstrated that CCL26 induced TAM infiltration by CCL26 binding to the CCR3 receptor. When LoVo-P and HT29-C cells were cocultured with TAMs, CCL26 binding to the CCR3 receptor enhanced the invasiveness of LoVo-P and HT29-C cells by mobilizing intracellular Caof TAMs to increase the expression of IL6 and IL8. In addition, IHC results indicated that protein levels of CCR3 and TAMs counts were higher in stage III and IV colorectal cancer tissues and correlated with CCL26. Moreover, similar results were observed using mice injected with LoVo-P and HT29-C cells. These data indicate that PRL-3 may represent a potential prognostic marker that promotes colorectal cancer invasion and metastasis by upregulating CCL26 to induce TAM infiltration..

Increasing evidence suggests that PRMT5, a protein arginine methyltransferase, has roles in cell growth regulation and cancer development. However, the role of PRMT5 in hepatocellular carcinoma (HCC) progression remains unclear. Here, we showed that PRMT5 expression was frequently upregulated in HCC tissues, and its expression was inversely correlated with overall survival in HCC patients. PRMT5 knockdown markedly inhibited in vitro HCC proliferation and in vivo tumorigenesis. We revealed that the mechanism of PRMT5‐induced proliferation was partially mediated by BTG downregulation, leading to cell cycle arrest during the G1 phase in HCC cells. Ectopic BTG2 overexpression decreased HCC growth, caused cell cycle arrest at the G1 phase, and downregulated Cyclin D1 and Cyclin E1 protein expression. Furthermore, we found that PRMT5‐induced ERK phosphorylation regulated BTG2 expression in HCC cells, whereas pretreatment with a selective ERK1/2 inhibitor (PD184352) significantly reversed the effect of PRMT5 on BTG2 expression. Our results indicated that PRMT5 promotes HCC proliferation by downregulating BTG2 expression via the ERK pathway.

Cisplatin has been widely employed as a cornerstone chemotherapy treatment for a wide spectrum of solid neoplasms; increasing tumor responsiveness to cisplatin has been a topic of interest for the past 30 years. Strong evidence has indicated that mitochondrial fission participates in the regulation of apoptosis in many diseases; however, whether mitochondrial fission regulates cisplatin sensitivity remains poorly understood. Here, we show that MFF mediated mitochondrial fission and apoptosis in tongue squamous cell carcinoma (TSCC) cells after cisplatin treatment and that miR-593-5p was downregulated in this process. miR-593-5p attenuated mitochondrial fission and cisplatin sensitivity by targeting the 3′ untranslated region sequence of MFF and inhibiting its translation. In exploring the underlying mechanism of miR-593-5p downregulation, we observed that BRCA1 transactivated miR-593-5p expression and attenuated cisplatin sensitivity in vitro. The BRCA1-miR-593-5p-MFF axis also affected cisplatin sensitivity in vivo. Importantly, in a retrospective analysis of multiple centers, we further found that the BRCA1-miR-593-5p-MFF axis was significantly associated with cisplatin sensitivity and the survival of patients with TSCC. Together, our data reveal a model for mitochondrial fission regulation at the transcriptional and post-transcriptional levels; we also reveal a new pathway for BRCA1 in determining cisplatin sensitivity through the mitochondrial fission program.