miR-21, which is a putative tumor onco-miR and frequently overexpressed microRNA in various tumors, has been linked to tumor progression through targeting of tumor-suppressor genes. In this study, we sought to determine whether miR-21 has any role on tumor progression of salivary adenoid cystic carcinoma (SACC) and the possible mechanisms. We found that the level of miR-21 expression was significantly higher in SACC than that in normal salivary tissues, and it is also higher in tumors with metastasis than that without metastasis. Using an anti-miR-21 inhibitor in an in vitro model, downregulation of miR-21 significantly decreased the capacity of invasion and migration of SACC cells, whereas a pre-miR-21 increased the capacity of invasion and migration of SACC cells. To explore the potential mechanisms by which miR-21 regulate invasion and migration, we identified one direct miR-21 target gene, programmed cell death 4 (PDCD4), which has been implicated in invasion and metastasis Salivary adenoid cystic carcinoma (SACC) is one of the most common malignancy of the salivary gland, accounting for 10% of salivary gland tumors and 30% of human salivary gland malignancies. 1,2 SACC is characterized by slow but aggressive growth, nerve and blood vessel invasion, multiple recurrences, and distant metastases. 3-5 Lung metastasis and nerve metastasis are the biological characteristics of SACC. [6][7][8] It has been reported that the incidence of SACC with distant metastasis ranged from 35 to 50% of all cases. Lung was the most common organ of its distant metastasis, and lung metastasis is still the leading death cause of patients with SACC. 4,5 Although the 5-year survival rate is high for patients with SACC, probably because of the slow growth of the tumor, the 10-and 15-year prognoses are poor because of the frequent local recurrences and distant metastases. [6][7][8] Although multiple genetic and epigenetic alterations have been detected in SACC, 3,9-13 the precise molecular mechanisms of progression and metastasis of SACC remain unknown.MicroRNAs (miRNAs) are small non-coding RNA molecules, with a length of 20-22 nucleotides, that regulate gene expression by either translational inhibition or mRNA degradation. miRNAs function as either oncogenes or tumor suppressors by inhibiting the expression of target genes, some of which are either directly or indirectly involved with canonical signaling pathways. 13,14 The roles and function of some selected miRNAs in SACC have been reported. 15

BackgroundMethylated DNA in fluids may be a suitable biomarker for cancer patients. XAF1 has been shown to be frequently down-regulated in human gastric cancer (GC). Here, we investigated if XAF1 methylation in GC could be a useful biomarker.MethodsReal-time RT-PCR was used to detect XAF1 mRNA expression; immunohistochemistry and western blot were used to examine XAF1 protein expression in GC tissues (n = 202) and their corresponding para-cancerous histological normal tissues (PCHNTs). Real-time methylation specific-PCR was used to investigate XAF1 promoter methylation in the same panel of GC tissues, their PCHNTs and sera.ResultsWe confirmed frequent XAF1 down-regulation in both mRNA and protein levels in GC tissues as compared to normal controls and PCHNTs. XAF1 hypermethylation was evidenced in 83.2% (168/202) of GC tissues and 27.2% (55/202) of PCHNTs, while no methylation was detected in the 88 normal controls. The methylation level in GC tissues was significantly higher than that in PCHNTs (p<0.05). The hypermethylation of XAF1 significantly correlated with the down-regulation of XAF1 in GC tissues in both mRNA and protein levels (p<0.001 each). Moreover, we detected high frequency of XAF1 methylation (69.8%, 141 out of 202) in the sera DNAs from the same patients, while the sera DNAs from 88 non-tumor controls were negative for XAF1 methylation. The XAF1 methylation in both GC tissues and in the sera could be a good biomarker for diagnosis of GC (AUC = 0.85 for tissue and AUC = 0.91 for sera) and significantly correlated with poorer prognosis (p<0.001). In addition, after-surgery negative-to-positive transition of XAF1 methylation in sera strongly associated with tumor recurrence.Conclusions1) Dysfunction of XAF1 is frequent and is regulated through XAF1 promoter hypermethylation; 2) Detection of circulating methylated XAF1 DNAs in the serum may be a useful biomarker in diagnosis, evaluating patient’s outcome (prognosis and recurrence) for GC patients.

Papillary thyroid carcinoma (PTC) is the most common malignancy of the thyroid gland, with a relatively high cure rate. Distant metastasis (DM) of PTC is uncommon, but when it occurs, it significantly decreases the survival of PTC patients. The molecular mechanisms of DM in PTC have not been systematically studied. We performed whole exome sequencing and GeneseeqPrime (425 genes) panel sequencing of the primary tumor, plasma and matched white blood cell samples from 20 PTC with DM and 46 PTC without DM. We identified somatic mutations, gene fusions and copy number alterations and analyzed their relationships with DM of PTC. BRAF‐V600E was identified in 73% of PTC, followed by RET fusions (14%) in a mutually exclusive manner (P < 0.0001). We found that gene fusions (RET, ALK or NTRK1) (P < 0.01) and chromosome 22q loss (P < 0.01) were independently associated with DM in both univariate and multivariate analyses. A nomogram model consisting of chromosome 22q loss, gene fusions and three clinical variables was built for predicting DM in PTC (C‐index = 0.89). The plasma circulating tumor DNA (ctDNA) detection rate in PTC was only 38.9%; however, it was significantly associated with the metastatic status (P = 0.04), tumor size (P = 0.001) and invasiveness (P = 0.01). In conclusion, gene fusions and chromosome 22q loss were independently associated with DM in PTC and could serve as molecular biomarkers for predicting DM. The ctDNA detection rate was low in non–DM PTC but significantly higher in PTC with DM.

The Wnt/β-catenin pathway is essential for embryonic development and homeostasis, but excessive activation of this pathway is frequently observed in various human diseases, including cancer. Current therapeutic drugs targeting the Wnt pathway often lack sufficient efficacy, and new compounds targeting this pathway are therefore greatly needed. Here we report that the plant-derived natural product parthenolide (PTL), a sesquiterpene lactone, inhibits Wnt signaling. We found that PTL dose-dependently inhibits Wnt3a- and CHIR99021-induced transcriptional activity assessed with the T-cell factor (TCF)/lymphoid enhancer factor (LEF) firefly luciferase (TOPFlash) assay in HEK293 cells. Further investigations revealed that PTL decreases the levels of the transcription factors TCF4/LEF1 without affecting β-catenin stability or subcellular distribution. Moreover, this effect of PTL on TCF4/LEF1 was related to protein synthesis rather than to proteasome-mediated degradation. Of note, siRNA-mediated knockdown of RPL10, a ribosome protein PTL binds, substantially decreased TCF4/LEF1 protein levels and also Wnt3a-induced TOPFlash activities, suggesting a potential mechanism by which PTL may repress Wnt/β-catenin signaling. In summary, PTL binds RPL10 and thereby potently inhibits the Wnt/β-catenin pathway.