AIM: To investigate the clinical significance of methylmethanesulfonate sensitivity 19(MMS19) expression in esophageal squamous cell carcinoma(ESCC).METHODS: Between June 2008 and May 2013, specimens from 103 patients who underwent endoscopic biopsy for the diagnosis of ESCC at the endoscopy center of Sun Yat-Sen University Cancer Center were collected; 52 matched-normal esophageal squamous epithelium samples were biopsied as controls.MMS19 protein expression was measured by immunohistochemistry.Of the 103 cases of ESCC, 49 received radical surgery following neoadjuvant chemoradiotherapy consisting of concurrent radiation in a total dose of 40 Gy and two cycles of chemotherapy with vinorelbine and cisplatin.Relationships between MMS19 expression, clinicopathologic characteristics and chemoradiotherapy response were analyzed.RESULTS: The MMS19 protein could be detected in both the cytoplasm and nucleus of most specimens.High cytoplasmic expression of MMS19 was detected in 63.1% of ESCC samples, whereas high nuclearexpression of MMS19 was found in 35.0%.High cytoplasmic MMS19 expression was associated with regional lymph node metastases(OR = 11.3, 95%CI: 2.3-54.7; P < 0.001) and distant metastases(OR = 13.1, 95%CI: 1.7-103.0; P = 0.002).Furthermore, high cytoplasmic MMS19 expression was associated with a response of ESCC to chemoradiotherapy(OR = 11.5, 95%CI: 3.0-44.5; P < 0.001), with a high cytoplasmic MMS19 expression rates in 79.3% and 25.0% of patients from the good chemoradiotherapy response group and poor response group, respectively.Nuclear MMS19 expression did not show any significant association with clinicopathologic characteristics or chemoradiotherapy response in ESCC.CONCLUSION: The results of our preliminary study suggest that MMS19 may be a potential new predictor of metastasis and chemoradiotherapy response in ESCC. AIM: To investigate the clinical significance of methylmethanesulfonate sensitivity 19 (MMS19) expression in esophageal squamous cell carcinoma (ESCC). METHODS: Between June 2008 and May 2013, specimens from 103 patients who underwent endoscopic biopsy for the diagnosis of ESCC at the endoscopy center of Sun Yat-Sen University Cancer Center were collected; 52 matched-normal esophageal squamous epithelium samples were biopsied as controls. MF19 protein expression was measured by immunohistochemistry. Of the 103 cases of ESCC, 49 received radical surgery following neoadjuvant chemoradiotherapy consisting of concurrent radiation in a total dose of 40 Gy and two cycles of chemotherapy with vinorelbine and cisplatin. Relationshipships between MMS19 expression, clinicopathologic characteristics and chemoradiotherapy response were reported .RESULTS: The MMS19 protein could be detected in both the cytoplasm and nucleus of the most specimens. High cytoplasmic expression of MMS19 was detected in 63.1% of ESCC samples, while high nuclearexpression of MMS19 was found in 35.0% .High cytoplasmic MMS19 expression was associated with regional lymph node metastases (OR = 11.3, 95% CI: 2.3-54.7; P <0.001) % CI: 1.7-103.0; P = 0.002) .Furthermore, high cytoplasmic MMS19 expression was associated with a response of ESCC to chemoradiotherapy (OR = 11.5, 95% CI: 3.0-44.5; P <0.001), with a high cytoplasmic MMS19 expression rates in 79.3% and 25.0% of patients from the good chemoradiotherapy response group and poor response group, respectively. Nuclear MMS19 expression did not show any significant association with clinicopathologic characteristics or chemoradiotherapy response in ESCC.CONCLUSION: The results of our preliminary study suggest that MMS19 may be a potential new predictor of metastasis and chemoradiotherapy response in ESCC.