Are there useful biomarkers for gastric cancer?

RUNX3 inhibits survivin expression and induces cell apoptosis in gastric cancer

Transcription factor RUNX3 is associated with gastric tumorigenesis and progression through regulating the expression of its target genes. Survivin is a member of the inhibitor of apoptosis (IAP) family and has been shown to inhibit cell apoptosis and promote cell proliferation. Increased survivin expression has been found in various cancer types, including gastric cancer. In this study, we found that restoration of RUNX3 promotes cell apoptosis through inhibiting the survivin expression, while RUNX3 inhibition increases the expression of survivin in gastric cancer cell lines. Moreover, RUNX3 over-expression inhibits,whereas its inhibition increases, the promoter activity of survivin gene, respectively. RUNX3-R122C, a mutation located in the conserved Runt domain, has no effect on the promoter activity of survivin gene. We further identified a RUNX3-binding site in the promoter of survivin gene and the binding of RUNX3 on survivin promoter leads to significantly inhibition of survivin expression. Finally, we confirmed the negative correlation of RUNX3 and survivin expression in clinical specimens of gastric cancer. These findings reveal a novel mechanism of RUNX3 for the induction of cell apoptosis in human gastric cancer.

RUNX3 regulates vimentin expression via miR-30a during epithelial-mesenchymal transition in gastric cancer cells

Runt-related transcription factor 3 (RUNX3) is a putative tumour suppressor via regulating the expression of a series of target genes. Clinical studies demonstrated that loss of RUNX3 expression is associated with gastric cancer progression and poor prognosis, but the underlying mechanism is not entirely clear. Accumulating evidence shows that the epithelial–mesenchymal transition (EMT) plays an important role in cancer relapse and metastasis. Therefore, we addressed whether RUNX3 has a role in the EMT in gastric cancer. Knockdown of RUNX3 promoted cell invasion and increased the protein expression of the mesenchymal marker vimentin in human gastric cancer cells. Overexpression of RUNX3 suppressed cell invasion and decreased the protein expression of vimentin in the cells and inhibited gastric cancer cells colonization in nude mice. Furthermore, overexpression of RUNX3 increased the expression of microRNA-30a (miR-30a), and miR-30a directly targeted the 3′ untranslated region of vimentin and decreased its protein level. miR-30a inhibitor abrogated RUNX3-mediated inhibition of cell invasion and downregulation of vimentin. Thus, RUNX3 suppressed gastric cancer cell invasion and vimentin expression by activating miR-30a. In gastric cancer patients, levels of RUNX3 were positively correlated with miR-30a and negatively associated with the levels of vimentin. Collectively, our data suggest a novel molecular mechanism for the tumour suppressor activity of RUNX3. Effective therapy targeting the RUNX3 pathway may help control gastric cancer cell invasion and metastasis by inhibiting the EMT.

CIP2A is overexpressed in gastric cancer and its depletion leads to impaired clonogenicity, senescence, or differentiation of tumor cells

PURPOSE

Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncogenic factor stabilizing c-MYC protein and driving cellular transformation. We determine whether CIP2A expression can serve as marker for gastric cancer and investigate the mechanism underlying CIP2A-mediated transformation and cell proliferation.

EXPERIMENTAL DESIGN

Normal and malignant gastric tissues derived from 37 patients with gastric cancer were analyzed for CIP2A expression using reverse transcription-PCR and immunohistochemical staining. Gastric and other cell lines with different p53 and pRB backgrounds were used to inhibit CIP2A expression using small interfering RNA and then examined for clonogenic potentials, senescence, or differentiation.

RESULTS

CIP2A mRNA was present in 34 of 37 (90%) of tumor specimens but absent in 27 of 37 (73%) of matched normal gastric mucosa. In 10 adjacent normal tissues with detectable CIP2A mRNA, 6 of them exhibited much weaker levels of CIP2A compared with their corresponding tumors. Thus, a total of 32 (87%) gastric cancer samples overexpressed CIP2A. CIP2A protein expression was readily detectable in the tumor tissues but absent in normal gastric mucosa. Depleting CIP2A expression substantially inhibited growth and clonogenic capabilities of tumor cell lines independently of p53 and pRB pathways. Gastric cancer-derived AGS cells underwent senescence following the inhibition of CIP2A expression. Moreover, CIP2A depletion triggered partial differentiation of leukemic HL60 cells.

CONCLUSION

CIP2A in tumor cells is required for sustained proliferation by preventing cell growth arrest, senescence, or differentiation and its expression is significantly (P < 0.001) discriminatory between normal and cancerous gastric tissue.

Expression of the full-length telomerase reverse transcriptase (hTERT) transcript in both malignant and normal gastric tissues

Activation of telomerase by the induction of a full-length telomerase reverse transcriptase (hTERT) transcript is a critical step during cellular immortalization and malignant transformation. Telomerase activity or hTERT expression has thus served as diagnostic and/or prognostic markers in different types of human malignancies. In the present study, we investigated the expression of the telomerase components hTERT and telomerase RNA template (hTER) in normal and malignant gastric tissues derived from 37 patients with gastric cancers. Overall hTERT mRNA was detectable in 33/37 (90%) of tumour specimens and 23/37 (62%) of the corresponding normal gastric tissues. Twenty-five of thirty-seven tumours (71%) expressed the full-length hTERT mRNA, and unexpectedly, this full-length transcript was found in 16 of 37 (43%) normal gastric tissues. Immunohistochemical analyses demonstrated a positive hTERT staining in small fractions of normal epithelial cells and in most gastric cancer cells. A close correlation between the presence of a full-length hTERT transcript and the c-MYC oncogene expression was observed in both normal and cancerous gastric specimens. Moreover, the full-length hTERT expression was positively associated with the tumour size in these patients. Similar levels of hTER expression were expressed in tumour and their corresponding normal tissues. The finding that the full-length hTERT transcript was present in both normal and malignant gastric tissues will preclude its use as a gastric cancer marker. Nevertheless, full-length hTERT mRNA expression may indicate a progressive gastric cancer, and its presence in normal gastric mucosa may have an impact on the anti-telomerase strategy for cancer therapeutic purpose.