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Clinical Significance of High Mobility Group A2 in Human Gastric Cancer and Its Relationship to let-7 MicroRNA Family

Authors' Affiliations: ¹ Department of Molecular and Surgical Oncology, Medical Institute of Bioregulation, Kyushu University, Beppu, Japan and ² Department of Surgical Oncology, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan

Requests for reprints: Masaki Mori, Department of Molecular and Surgical Oncology, Medical Institute of Bioregulation, Kyushu University, 4546 Tsurumibaru, Beppu 874-0838, Japan. Phone: 81-977-27-1650; Fax: 81-977-27-1651; E-mail: mmori{at}beppu.kyushu-u.ac.jp.

Purpose: The high mobility group A2 (HMGA2) nonhistone chromosomal protein can modulate transcription by altering chromatin architecture. HMGA2 is highly expressed during embryogenesis and in various benign and malignant tumors. Recent studies report that HMGA2 is negatively regulated by the let-7 microRNA (miRNA) family. However, no studies have examined the clinical significance of HMGA2 and its relationship to the let-7 miRNA family in gastric cancer.

Experimental Design: Using quantitative real-time reverse transcription–PCR, we analyzed HMGA2 expression with respect to various clinicopathologic factors in 110 patients with gastric cancer. We also did an association study comparing HMGA2 expression and let-7 miRNA family expression in gastric cancer.

Results: Expression of HMGA2 in cancerous tissues was significantly higher than in noncancerous tissues (P < 0.05). Elevated HMGA2 expression was significantly correlated with serosal invasion (P < 0.05) and poor clinical prognosis (P < 0.05). A multivariate analysis showed that HMGA2 expression status was an independent prognostic factor (P < 0.05). An inverse correlation between HMGA2 and let-7a was found in gastric cancer cell lines (P = 0.08). The expressions of let-7a, let-7b, and let-7c in gastric cancer patients with low HMGA2 expression were significantly higher than those with high HMGA2 expression (P < 0.05).

Conclusions: High expression of HMGA2 in gastric cancer correlates with tumor invasiveness and is an independent prognostic factor. Furthermore, our findings suggest that HMGA2 is negatively regulated by the let-7 miRNA family in human gastric cancer.