| Summary: | <p>Abstract</p> <p>Background</p> <p>MicroRNA let-7i has been proven to be down-regulated in many human malignancies and correlated with tumor progression and anticancer drug resistance. Our study aims to characterize the contribution of miRNA let-7i to the initiation and malignant progression of locally advanced gastric cancer (LAGC), and evaluate its possible value in neoadjuvant chemotherapeutic efficacy prediction.</p> <p>Methods</p> <p>Eighty-six previously untreated LAGC patients who underwent preoperative chemotherapy and radical resection were included in our study. Let-7i expression was examined for pairs of cancer tissues and corresponding normal adjacent tissues (NATs), using quantitative RT-PCR. The relationship of let-7i level to clinicopathological characteristics, pathologic tumor regression grades after chemotherapy, and overall survival (OS) was also investigated.</p> <p>Results</p> <p>Let-7i was significantly down-regulated in most tumor tissues (78/86: 91%) compared with paired NATs (<it>P</it> < 0.001), and low levels of let-7i were significantly correlated with local invasion, lymphatic metastasis, and poor pathologic tumor response. Multivariate Cox regression analysis revealed that low let-7i expression was an unfavorable prognostic factor of OS (hazard ratio (HR) = 2.316, <it>P</it> =0.024) independently of other clinicopathological factors, including tumor node metastasis (TNM) stage (HR = 3.226, <it>P</it> = 0.013), depth of infiltration (HR = 4.167, <it>P</it> < 0.001), and lymph node status (HR = 2.245, <it>P</it> = 0.037).</p> <p>Conclusions</p> <p>These findings indicate that let-7i may be a good candidate for use a therapeutic target and a potential tissue marker for the prediction of chemotherapeutic sensitivity and prognosis in LAGC patients.</p>
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