Aldehyde dehydrogenase plays crucial roles in response to lower temperature stress in Solanum tuberosum and Nicotiana benthamiana.

The aim of this study is to elucidate the role of ALDH2B7a during the response to lower temperature in Solanum tuberosum. This gene was found to have altered intragenic DNA methylation status in our previous reports. A total of 18 orthologs of StALDH2B7a were identified in the S. tuberosum genome, which were then divided into 8 aldehyde dehydrogenase (ALDH) subfamilies. The methylation statuses of four intragenic cytosine sites in intron 5 and exon 6 of genomic StALDH2B7a were altered by lower temperature stress, resulting in changes in the expression of StALDH2B7a. Silencing of NbALDH2C4, a homolog of StALDH2B7a in Nicotiana benthamiana, resulted in plants which were sensitive to lower temperature and accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA). These data suggested that the expression of StALDH2B7a was upregulated by alteration of its intragenic cytosine methylation status during lower temperature stress, and additional StALDH2B7a enzymes scavenged excess aldehydes resulting from ROS in a response to cold stress in potato. Our study expands the understanding of the mechanisms involved in plant responses to lower temperature, and provides a new gene source to improve potato tolerance to cold stress in northern China, where lower temperature is one of the key limiting factors for crop production.

Epigenetic silencing of PRSS3 provides growth and metastasis advantage for human hepatocellular carcinoma.

Protease, serine, 3 (PRSS3), a member of the trypsin family of serine proteases, has been shown to be aberrantly expressed in several cancer types and to play important roles in tumor progression and metastasis. However, the expression and function of PRSS3 gene in hepatocellular carcinoma (HCC) remain unclear. Here we found that PRSS3 expression was decreased in human HCC cell lines and HCC surgical specimens. This was associated with intragenic methylation of PRSS3 gene. Treatment with DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine and/or histone deacetylase inhibitor trichostatin A restored PRSS3 expression in HCC cell lines. Ectopic overexpression of PRSS3 gene in HCC cell lines significantly suppressed cell proliferation and colony formation and arrested cell cycle at G1/S phase, accompanied with downregulation of cyclin D1 (CCND1)/CDK4 and cyclin E1 (CCNE1)/CDK2 complexes. Moreover, PRSS3 overexpression in HCC cells inhibited HCC cell migration and invasion with downregulation of matrix metallopeptidase 2 (MMP2). Further study showed that PRSS3 overexpression diminished the phosphorylation of mitogen-activated protein kinase/extracellular-signal-regulated kinase signaling protein, mitogen-activated protein kinase kinase 1 (MEK1)/mitogen-activated protein kinase kinase 2 (MEK2) and extracellular-signal related kinase 1 (ERK1)/extracellular-signal related kinase 2 (ERK2), in HCC cells. In contrast, knockdown of PRSS3 by small interfering RNA resulted in opposite effects on an HCC cell line SNU-387 which constitutively expresses PRSS3. These results demonstrate that downregulation of PRSS3 by intragenic hypermethylation provides growth and metastasis advantage to HCC cells. The clinical relevance of PRSS3 to human HCC was shown by the intragenic methylation of PRSS3 in HCC specimens and its association with poor tumor differentiation in patients with HCC. Thus, PRSS3 is a potential prognostic biomarker and an epigenetic target for intervention of human HCC. KEY MESSAGES: • PRSS3 is downregulated by intragenic hypermethylation in HCC. • Epigenetic silencing of PRSS3 facilitates growth, migration, and invasion of HCC. • PRSS3 intragenic methylation has implication in diagnosis of HCC.

Clinical significance of expression and epigenetic profiling of TUSC1 in gastric cancer.

BACKGROUND AND OBJECTIVES: The prognosis of advanced gastric cancer (GC) remains dismal. The aim of this study was to identify a novel tumor suppressor gene (TSG) with repressed transcription by aberrant DNA methylation in GC. METHODS: The expression and methylation status of tumor suppressor candidate 1 (TUSC1) were evaluated in GC cell lines and 112 pairs of surgical specimens. TUSC1 protein expression and distribution in GC tissue were determined by immunohistochemistry. RESULTS: The majority of GC cell lines (83%) and GC tissues (82%) showed downregulation of TUSC1 mRNA compared with noncancerous tissues. No significant differences were found in TUSC1 mRNA expression between three GC subtypes categorized by tumor locations and morphology. Reduced expression of TUSC1 mRNA in GC tissues was significantly associated with advanced T stage, vessel invasion and lymph node metastasis, leading to poor prognosis. The expression patterns of TUSC1 protein were confirmed to be consistent with those of TUSC1 mRNA. Sixty-three (57%) of 112 patients showed intragenic hypermethylation of TUSC1 in GC tissues. CONCLUSIONS: Our results suggested that reduced expression of TUSC1 mRNA was related to poor prognosis and TUSC1 is a putative TSG that is suppressed through intragenic hypermethylation in GC.