Alteration in gene expression profile and oncogenicity of esophageal squamous cell carcinoma by RIZ1 upregulation

Synergism between RIZ1 gene therapy and paclitaxel in SiHa cervical cancer cells

RIZ1 is a tumor suppressor gene. The purpose of the present study was to investigate the inhibitory effect of RIZ1 gene therapy on the growth of SiHa cervical cancer cells and its synergism with paclitaxel. The expression levels of RIZ1 were examined by real-time PCR and western blotting before and after transfection of RIZ1. The effects of paclitaxel or pcDNA3.1(+)-RIZ1 alone or in combination, on the proliferation of SiHa cells were evaluated by MTT method. The inhibitory effect on the proliferation of SiHa cells was more significant in the pcDNA3.1(+)-RIZ1 combined with paclitaxel group than in the pcDNA3.1(+)-RIZ1 or paclitaxel groups (P<0.05). The expression level of RIZ1 in SiHa cells increased after treatment with paclitaxel, which indicated a synergism between them. RIZ1 gene therapy combined with paclitaxel showed stronger cell inhibition than paclitaxel alone, which indicated a synergism between them.

Lower PRDM2 expression is associated with dopamine-agonist resistance and tumor recurrence in prolactinomas

Background

Dopamine agonists (DAs) are the first-line treatment for prolactinomas, which account for 25–30% of functioning pituitary adenomas, and bromocriptine (BRC) is the only commercially available DAs in China. However, tumors are resistant to therapy in 5–18% of patients.

Methods

The exomes of six responsive prolactinomas and six resistant prolactinomas were analyzed by whole-exome sequencing.

Results

Using stringent variant calling and filtering parameters, ten somatic variants that were mainly associated with DNA repair or protein metabolic processes were identified. New resistant variants were identified in multiple genes including PRDM2, PRG4, MUC4, DSPP, DPCR1, RP1L1, MX2, POTEF, C1orf170, and KRTAP10-3. The expression of these genes was then quantified by real-time reverse-transcription PCR (RT–qPCR) in 12 prolactinomas and 3 normal pituitary glands. The mRNA levels of PRDM2 were approximately five-fold lower in resistant prolactinomas than in responsive tumors (p < 0.05). PRDM2 protein levels were lower in resistant prolactinomas than in responsive tumors, as determined by Western blotting and immunohistochemical analysis (p < 0.05). Overexpression of PRDM2 upregulated dopamine receptor D2 (D2DR) and inhibited the phosphorylation of ERK1/2 in MMQ cells. PRDM2 showed a synergistic effect with BRC on the inhibition of prolactin (PRL) secretion and MMQ cell viability, and low PRDM2 expression was associated with tumor recurrence.

Conclusions

PRDM2 downregulation may play a role in dopamine-agonist resistance and tumor recurrence in prolactinomas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1267-0) contains supplementary material, which is available to authorized users.

PRDI-BF1-RIZ domain of retinoblastoma protein-interacting zinc finger gene 1 induces apoptosis and exerts anticancer activity in esophageal squamous cell carcinoma cells

The present study examined the role of the PRDI-BF1-RIZ (PR) domain of tumor suppressor retinoblastoma protein-interacting zinc finger gene 1 (RIZ1) as an anticancer domain and its ability to induce apoptosis in esophageal squamous cell carcinoma (ESCC) cells. The TE13 ESCC cell line was transfected with pcDNA3.1(+) eukaryotic expression vectors bearing the open reading frames of either the human RIZ1 gene or the PR domain, and the mRNA and protein expression levels were then detected using quantitative reverse transcription polymerase chain reaction and western blotting, respectively. The rate of apoptosis was determined by flow cytometry and the cell invasion ability was determined by an invasion assay. RIZ1 and the PR domain induced apoptosis and reduced the cell invasion ability (P<0.01). These findings indicate that the RIZ1 gene possesses anticancer activity in the PR domain, which may be important in inhibiting the development of ESCC.

Effect of the downregulation of SMYD3 expression by RNAi on RIZ1 expression and proliferation of esophageal squamous cell carcinoma

The present study aimed to investigate the expression and role of SET and MYND domain-containing protein 3 (SMYD3) in esophageal squamous cell carcinoma; to observe the proliferation of esophageal squamous cell carcinoma after suppression of SMYD3 expression; and to explore the effect of SMYD3 downregulation on the expression of retinoblastoma protein-interacting zinc finger gene 1 (RIZ1). Tissues from 11 patients, including cancer and normal esophageal tissues, were obtained by surgery to observe the SMYD3 protein expression immunohistochemistry. Esophageal squamous cell carcinoma TE13 cells were transfected with four different SMYD3-shRNA plasmids, and SMYD3 mRNA expression levels were assessed to select the most efficient interfering plasmid. After SMYD3 downregulation in TE13 cells, mRNA and protein expression levels of SMYD3 and RIZ1 were determined using RT-PCR and western blotting, and cell proliferation was evaluated by the MTT method. In all 11 tissue paired samples, SMYD3 protein expression was higher in the cancer tissues (72.7%; 8/11), than that in the normal tissues (18.2%; 2/11) (Fisher's exact test, P=0.03). The mRNA expression levels of SMYD3 were significantly decreased by RNA interference (P<0.05), and plasmid SMYD3-shRNA-1242 was determined to be the most effective. Compared with the controls, transfection with the SMYD3-shRNA interfering plasmid significantly reduced the SMYD3 mRNA and protein expression levels in TE13 cells (P<0.05), whereas the expression levels of the anti-oncogene RIZ1 were increased (P<0.05). The MTT assay showed that ablation of SMYD3 expression significantly inhibited proliferation of TE13 cells (P<0.05). SMYD3 may participate in the biological activity of esophageal squamous cell carcinoma, as overexpression of SMYD3 correlates with its occurrence and its downregulation inhibits cancer cell proliferation. The shRNA efficiently downregulated SMYD3 in TE13 cells, which represents an SMYD3-interfered cell-test-model for future experiments. RNAi suppression of SMYD3 promoted the expression of RIZ1 in TE13 cells, suggesting a signal transduction pathway between SMYD3 and RIZ1. The SMYD3-RIZ1 pathway may represent a therapeutic target for esophageal squamous cell carcinoma.