The ubiquitin-conjugating enzyme E2-EPF is overexpressed in cervical cancer and associates with tumor growth.

We found that the ubiquitin-conjugating enzyme E2-EPF mRNA is highly expressed in cervical squamous cancer relative to normal tissues and its expression levels positively correlate with clinical stage. Reduction of E2-EPF protein levels by >80% using shRNA decreases the expression levels of HIF-1α, and the proliferation, invasion and tumorigenicity of SiHa, a cervical squamous cancer cell line. E2-EPF knockdown also increases the chemosensitivity to topoisomerase I inhibitor (topotecan) and II (etoposide and doxorubicin). Our results suggest that E2-EPF is associated with the growth and aggressivity of cervical tumor cells. Targeting the E2-EPF pathway may have potential clinical applications for the treatment of cervical cancer.

Possible role of the exchange protein directly activated by cyclic AMP (Epac) in the cyclic AMP-dependent functional differentiation and syncytialization of human placental BeWo cells.

BACKGROUND: The mononuclear villous cytotrophoblast (CTB) differentiates and fuses to the multinucleated syncytiotrophoblast (STB), which produces hCG and progesterone. cAMP-mediated intracellular pathways are involved in the process of endocrine differentiation and fusion (syncytialization). The exchange protein directly activated by cAMP (Epac) is a mediator of cAMP signaling. We examined the differential roles of Epac and protein kinase A (PKA) signaling in the cell fusion and differentiation of trophoblast-derived BeWo cells. METHODS: Epac1 and Epac2 were localized in human placental tissue (n = 9) by immunohistochemistry. The PKA-selective cAMP analog (N(6)-phenyl-cAMP, Phe) or Epac-selective cAMP analog (CPT) was tested for effects on hCG and progesterone production, and syncytialization in BeWo cells. The effect of knockdown of Epac or its downstream target molecule (Rap1) on syncytialization was evaluated. RESULTS: Epac1 and Epac2 proteins were expressed in villous CTB, STB, stroma, blood vessels and extravillous CTB of the placenta. Phe increased the expression of hCG alpha/beta mRNA and secretion of hCG protein in BeWo cells (P < 0.01 versus control). CPT-stimulated production of hCG (P < 0.05), albeit to a lesser extent than Phe. Progesterone production was also enhanced by Phe or CPT (P < 0.01 and P < 0.05, respectively). CPT or a stable cAMP analog (dibutyryl-cAMP: Db) increased the number of syncytialized BeWo cells (P < 0.01), whereas Phe did not stimulate fusion. CPT- or Db-induced syncytialization was observed, even in the presence of a PKA inhibitor. Knockdown of Epac1 or Rap1 repressed the Db-, CPT- or forskolin-induced cell fusion. CONCLUSIONS: The Epac signaling pathway may be associated with the cAMP-mediated functional differentiation and syncytialization of human trophoblasts.

Circulating IGF-binding protein 7 (IGFBP7) levels are elevated in patients with endometriosis or undergoing diabetic hemodialysis.

BACKGROUND: Insulin-like growth factor-binding protein-7 (IGFBP7) is a secretory protein with a molecular mass of approximately 30 kDa. It is abundantly expressed in the uterine endometrium during the secretory phase of the menstrual cycle. Decreased IGFBP7 expression has been observed in some cancers and leiomyomata. METHODS: To determine whether serum IGFBP7 levels reflect changes in uterine IGFBP7 expression in humans during the menstrual cycle, and to examine whether serum IGFBP7 levels are altered in patients with various disorders, we developed a novel, dual-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Firstly, concentrations of IGFBP7 released into the medium were determined in cultured endometrial stromal and glandular cells. Blood samples were collected from women who had normal menstrual cycles and who had been diagnosed with endometriosis. Serum from hemodialysis patients and gastrointestinal cancers was also used to determine the IGFBP7 levels. RESULTS: Using this new ELISA, we demonstrated that cultured uterine cells secrete IGFBP7 into the medium. Patients with endometriosis and those with type II diabetes mellitus undergoing hemodialysis had significantly higher serum concentrations of IGFBP7 than the relevant control subjects. There were no differences in serum IGFBP7 levels in women at different stages of the menstrual cycle. Furthermore, serum IGFBP7 levels in patients with colorectal, esophageal, or endometrial cancer were not different than normal healthy subjects. CONCLUSION: Our observations suggest that IGFBP7 is associated with the pathophysiology of endometriosis and diabetes mellitus, and that serum IGFBP7 levels do not reflect enhanced uterine expression of IGFBP7 mRNA during the menstrual cycle.

Early growth response-1 mediates downregulation of telomerase in cervical cancer.

Early growth response (Egr)-1 is a transcription factor that triggers transcription of downstream genes within 15-30 min of various stimulations. These genes are expressed rapidly through specific promoter activation and mediate cell growth and angiogenesis. Following the previous computational identification of a site that was thought to be an Egr-1 consensus binding site at -273 to -281 in the human telomerase reverse transcriptase (hTERT) promoter region, the present study was conducted to evaluate the role of Egr-1 in the regulation of hTERT and telomerase in uterine cervical cancer. First, the expression of Egr-1 and hTERT at the mRNA level was examined in cervical cancer tissues. Egr-1 and hTERT were expressed much higher in cervical cancer tissues than in the normal cervix. However, a negative correlation was noted in the expression between Egr-1 and hTERT. By luciferase assay using hTERT promoter constructs, hTERT transcriptional activation was shown to be inhibited when Egr-1 was overexpressed. Furthermore, Egr-1 overexpression decreased hTERT protein production as well as hTERT mRNA as observed by western blotting analysis and real-time reverse transcription-polymerase chain reaction, respectively. The present study suggests that Egr-1 plays an important regulatory role in the transcriptional activation of hTERT.