Metformin-Induced Heat Shock Protein Family A Member 6 Is a Promising Biomarker of Esophageal Squamous Cell Carcinoma

Abstract

<b><i>Introduction:</i></b> Antidiabetic drug metformin exerts various antitumor effects on different cancers. Esophageal squamous cell carcinoma (ESCC) is an intractable digestive organ cancer and new treatment strategy is required. In this study, we performed a comprehensive gene expression analysis of ESCC cell lines treated with metformin, which provided helpful information on the antitumor effects of metformin in ESCC. Next, we selected a promising gene among them and examined its effects on ESCC properties. <b><i>Methods:</i></b> We examined metformin-induced mRNA expression changes in two human ESCC cell lines by performing next-generation sequencing (NGS) and pathway analysis. Heat shock protein family A (Hsp70) member 6 (<i>HSPA6</i>) expression in surgical specimens obtained from 83 ESCC patients who underwent curative operations was evaluated immunohistochemically and analyzed. <b><i>Results:</i></b> Metformin upregulated mRNA expression of the many genes, including <i>HSPA6</i>, a cancer immune-related gene, and inhibited mRNA expression of the other many genes. Pathway analysis indicated major canonical pathways and upstream regulators related to metformin. The result indicated <i>HSPA6</i> as a promising biomarker. <i>HSPA6</i> expression correlated with disease-free survival (DFS) of the patients with all stage ESCC (<i>p</i> = 0.021), especially with stage I/II ESCC (<i>p</i> &#x3c; 0.001). With stage III, low <i>HSPA6</i> expression was not associated with poor DFS (<i>p</i> = 0.918). Multivariate analysis indicated that independent low <i>HSPA6</i> expression was an independent poor prognostic factor of stage I/II ESCC (<i>p</i> &#x3c; 0.001). However, <i>HSPA6</i> expression did not correlate with the clinicopathological characteristics, including age, sex, tumor depth, lymph node metastasis, tumor stage, and tumor markers of the patients with stage I/II ESCC. <b><i>Conclusions:</i></b> This NGS analysis detected prospective candidate genes, including <i>HSPA6</i>. Our results indicate that <i>HSPA6</i> is a promising biomarker of the recurrence risk of stage I/II ESCC. Further studies on <i>HSPA6</i> would lead to better treatment.