Objective To investigate the expression of trophoblast cell-surface antigen 2(TROP2)in salivary ade-noid cystic carcinoma(SACC)in order to analyze its relationship with TROP2 expression and clinicopathological features,as well as to clarify the correlation between TROP2 expression and the prognosis of patients with SACC.Methods With approval from the ethics committee,the expression of TROP2 in 85 SACC and paracancer tissue sam-ples was detected by using the immunohistochemical method,and the relationship between TROP2 expression and clini-copathological characteristics was analyzed.The Kaplan-Meier method was used to analyze the relationship between TROP2 protein expression and 5-year disease-free survival(DFS)in 40 patients with SACC.Furthermore,the logistic re-gression model was used to analyze the prognostic factors of patients with SACC.Results The low or no expression rate of TROP2 in SACC tissues was significantly higher than that in paracancer tissues(P＜0.001).Low or no expres-sion of TROP2 was significantly positively correlated with tumor growth and clinical staging in patients with SACC(P＜0.05).Kaplan-Meier survival analysis showed that the DFS of patients with SACC with low or no expression of TROP2 protein was significantly lower than those of patients with high expression of TROP2 protein(P＜0.05),and the progno-sis was poor.The logistic regression model showed that low or no expression of TROP2 protein(OR=5.37;95%CI:1.03-28.08;P=0.046)and Ⅲ-Ⅳ clinical staging(OR=6.89;95%CI:1.37～34.77;P=0.019)were risk factors affect-ing the prognosis of patients with SACC.Conclusion Low or no expression of TROP2 protein in SACC tissues leads to poor prognosis of patients and is positively correlated with tumor growth and clinical staging.In addition,low or no ex-pression of TROP2 can be used as an independent prognostic risk factor for poor prognosis in patients with SACC,and TROP2 is a marker of poor prognosis in patients with SACC.

Malignant tumors have become the main cause of human death.With the prolonged use of chemotherapeutic drugs during the treatment process,tumor cell resistance is also constantly increasing.long non-coding RNA(lncRNA)is an important mem-ber of the non-coding RNA family.Cancer susceptibility candidate 2(CASC2)is a type of long non-coding RNA,high expression of CASC2 can inhibit tumor cell development and reduce drug resistance of tumor cells by promoting apoptosis,regulating signaling path-ways,participating in cellular transmission pathways,competitively binding of miRNA,and changing the protein structure or functional status.This article will provide a comprehensive review of the regulatory effects and mechanism of lncRNA CASC2 on chemotherapy resistance in malignant tumors.