AKR1C1 Low Expression In Nasopharyngeal Carcinoma Increases Cisplatin Sensitivity

Nasopharyngeal carcinoma(NPC)is one of the malignant tumors of the nasopharyngeal epithelium.Nasopharyngeal carcinoma has a typical geographical distribution,especially in Southern China and Southeast Asia.In recent years,improved radiotherapy techniques have given satisfactory outcomes of early stage of NPC.But most of the patients were diagnosed as locally advanced NPC at the first diagnosis.According to different literature reports,their 5-year survival rate was still only about 30-80%.As indicated by the National Comprehensive Cancer Network(NCCN)Guidelines,locoregionally advanced disease requires cisplatin-based concurrent chemoradiotherapy.Thus,understanding the mechanism of cisplatin-resistance in NPC may enable the development of new strategies to overcome chemoresistance and improve clinical outcome of locally advanced NPC cases.Human 20-keto reductase family 1 member C1(AKR1C1)is a member of the aldehyde ketone reductase superfamily(AKRs).AKR family members catalyze the conversion of aldehydes and ketones to their corresponding alcohols.Their substrates include endogenous and xenobiotic non-steroidal carbonyl compounds.Moreover,chemotherapeutic drugs containing carbonyl can be converted to inactivated reductive metabolite,leading to the chemotherapyresistance.Actually,cumulative data indicated that AKR1C1 has led to the resistance of multiple chemotherapeutic drugs for cancer treatment.Thus,targeting AKR family members provide a novel therapeutic strategy for overcoming chemoresistance in malignant tumours.Objective: The aim of this research was to clarify the expression of AKR1C1 in nasopharyngeal carcinoma and normal nasopharyngeal mucosa,and to analyze the effect of AKR1C1 on the biological behavior of nasopharyngeal carcinoma cells and it's role in cisplatin resistance in NPC.Methods: 1.The expression of AKR1C1 protein in nasopharyngeal carcinoma and normal nasopharyngeal mucosa was detected by immunohistochemistry.2.AKR1C1 protein expression was detected by Western blot in different nasopharyngeal carcinoma cell lines and immortalized nasopharyngeal epithelial cell lines.3.To analyze the correlation between the expression of AKR1C1 protein in nasopharyngeal carcinoma tissue and the clinicopathological characteristics of nasopharyngeal carcinoma,and to analyze the survival.4.AKR1C1 was down-regulated by transiently transfection of CNE1 and CNE2 cells with small interfering RNA.5.The effects of AKR1C1 knockdown by si RNA on proliferation,migration and invasion in NPC cells were evaluated by CCK-8,wound healing,and transwell assays.6.To evaluate the effects of AKR1C1 silencing on cisplatin sensitivity in NPC cells,CCK-8 assays were used to detect cell proliferation,flow cytometry was used to detect cell cycle distribution,and flow cytometry and DAPI staining were used to detect cell apoptosis.Results: 1.AKR1C1 was down-regulated in nasopharyngeal carcinoma tissues,and highly expressed in ciliated columnar epithelial cells,and lowly expressed in squamous metaplastic nasopharyngeal epithelial tissues;Some nasopharyngeal carcinoma cells were expressed,some were deleted,and the expression was lost in normal nasopharyngeal carcinoma cells.2.The expression level of AKR1C1 in nasopharyngeal carcinoma tissues was down-regulated with the malignant progression of the clinicopathological characteristics of nasopharyngeal carcinoma;however,the 5-year survival rate was higher in patients with low expression of AKR1C1.3.Si RNA-transient transfection successfully reduced the expression of AKR1C1.4.Knockdown of AKR1C1 by si RNA showed no impact on cell proliferation,migration and invasion in NPC cells.5.Knockdown of AKR1C1 by si RNA enhanced cisplatin-induced inhibition of cell proliferation and cell cycle arrest.6.Knockdown of AKR1C1 by si RNA increased cisplatin-induced apoptosis.Conclusions: Although AKR1C1 expression is down-regulated with the malignant progression of nasopharyngeal carcinoma,down-regulation of AKR1C1 is a good prognostic factor for overall survival(OS)in NPC patients.In vitro studies showed that AKR1C1 wasn't directly involved in the malignant biological behaviors of NPC cells;Whereas,AKR1C1 knockdown could enhance cisplatin sensitivity of NPC cells,suggesting that the survival effect of AKR1C1 on patients with nasopharyngeal carcinoma depends on its resistance to chemotherapy.These results suggest that AKR1C1 is a potential marker for predicting cisplatin response and could serve as a molecular target to increase cisplatin sensitivity in NPC.