Objective To investigate the association of FAT atypical cadherin 1 (FAT1) with clinicopathological parameters and prognosis in esophageal squamous cell carcinoma (ESCC).

Methods The retrospective cohort study was conducted. The clinicopathological data of 124 patients with ESCC who were admitted to Shanxi Cancer Hospital from January 2011 to December 2015 were collected. There were 85 males and 39 females, aged from 40 to 72 years, with a median age of 60 years. The ESCC tissues surgically removed and adjacent tissues specimens were collected to prepare tissue microarray for immunohistochemical staining. The 5 cases of ESCC tissues and adjacent tissues were analyzed by real-time quantitative polymerase chain reaction (qRT-PCR). Observation indicators: (1) the expression of FAT1 protein in ESCC and adjacent tissues; (2) the expression of FAT1 RNA in ESCC and adjacent tissues; (3) the expression of FAT1 protein in ESCC tissues and its association with clinicopathological parameters; (4) follow-up and survival. Follow-up using outpatient examination and telephone interview was conducted to detect survival of patients up to February 13, 2019. The survival time was from surgical date to tumor-related death or endpoint of follow-up. Measurement data with normal distribution were represented as Mean±SD, and comparison between groups was analyzed using the t test. Measurement data with skewed distribution were represented as M (range). Count data were described as absolute numbers or percentages, and comparison between groups was analyzed using the chi-square test. Comparison of ordinal data was analyzed using the non parameter rank sum test. The Kaplan-Meier method was used to calculate survival time, and Log-rank test was used for survival analysis.

Results (1) The expression of FAT1 protein in ESCC and adjacent tissues: of 124 specimens, the 107 cases of ESCC tissues and 93 cases of adjacent tissues were finally obtained because of exfoliative tissues. There were 76 cases of ESCC tissues and corresponding adjacent tissues matched. Results of immuno-histochemical staining showed that FAT1 protein was expressed in both ESCC and adjacent tissues and was brown after staining. FAT1 was located in cytomembrane, with high expression of FAT1 as ≥75 and low expression as <75. The relative expression levels of FAT1 protein in ESCC and adjacent tissues were 68±42 and 77±37, showing a significant difference between ESCC and adjacent tissues (t=2.380, P<0.05). (2) The expression of FAT1 RNA in ESCC and adjacent tissues: results of qRT-PCR showed that the relative expression levels of FAT1 RNA in 5 cases of ESCC and adjacent tissues were 1.6±0.4 and 2.5±0.3, with a significant difference between them (t=3.560, P<0.05). (3) The expression of FAT1 protein in ESCC tissues and its association with clinicopathological parameters: of the 107 ESCC patients, 58 cases had high expression of FAT1. There were 42 and 16 cases with high expression of FAT1 in 65 non-drinking patients and 42 drinking patients, respectively, showing a significant difference between them (χ²=7.229,P<0.05). (4) Follow-up and survival: 96 of 107 ESCC patients were followed up for 38.0‒94.9 months, with a median follow-up time of 45.9 months. Survival analysis showed that the survival time of patients with high FAT1 expression was 24 months, versus 22 months of patients with low FAT1 expression, indicating no significant difference between them (χ²=1.773, P>0.05). Results of subgroup analysis showed that the survival time was 24 months and 21 months of female patients with high and low FAT1 expression, 23 months and 22 months of non-smoking patients with high FAT1 expression and low FAT1 expression, 23 months and 21 months of non-drinking patients with high FAT1 expression and low FAT1 expression, respectively, showing significant differences between them (χ²=8.769, 12.827, 10.724, P<0.05).

Conclusions The expression of FAT1 in ESCC tissues is low. Female, non-smoking and non-drinking ESCC patients with high FAT1 expression have good survival.