Studies Of Expression Of Lipid Metabolism-related Molecules In Ovarian Cancer Tissues And Its Correlation With Platinum Resistance And Prognosis Based On Bioinformatics Analysis

BackgroundOvarian cancer(OC)is the most lethal gynecological malignancy.Despite great advances in surgical techniques and adjuvant therapy,the clinical prognosis of ovarian cancer remains poor,with a 5-year survival rate of only 49%.A majority of the OC patients are diagnosed at later stages,where cytoreductive surgery followed by chemotherapy with platinum-based drugs is the primary choice for the treatment.Although 60%-90%of OC patients respond well to platinum-based drugs,median progression-free survival of patients with advanced disease is only 18 months,for which chemoresistance is largely to be blamed.Recent studies have shown that the development of platinum-resistance is a multifactorial phenomenon,involving alterations in the tumor microenvironment,increased DNA repair,cancer stem cells activity,and metabolic reprogramming.In a variety of cancer cells,lipid uptake,storage,and lipogenesis are increased and contributed to rapid tumor growth.Cholesterol is one of the vital components of mammalian cell membranes and involved in cell cycle regulation.Rapidly growing tumor cells require higher amounts of cholesterol and several studies have suggested that cholesterol metabolism plays an important role in the progression of malignancies and the prognosis of cancer patients.Reprogramming of cholesterol metabolic pathways has been observed in many cancers,including ovarian cancer.Recent studies have also shown that reprogramming of cholesterol metabolic pathways might be involved in chemoresistance in ovarian cancer.Nevertheless,the specific mechanism by which cholesterol metabolic pathway reprogramming causes platinum resistance remains unclear.In this study,online survival analyses were performed to determine the relationship between LDLR and HMGCR gene expression and the prognosis of ovarian cancer patients(from TCGA and GEO datasets)using the KM Plotter software(measured by Progression-free survival or Post-progression Survival).We studied two cholesterol metabolism-related proteins LDLR and HMGCR expression and plasma LDL and cholesterol levels are related to platinum resistance and prognosis in patients with OC.Purposes1.To anlyze of TCGA and GEO datasets to explore the relationship between the expression levels of LDLR and HMGCR in ovarian cancer tissues and the prognosis of patients.2.To explore the relationship between serum LDL,CHO and drug resistance in patients with ovarian cancer3.To detect the expression and location of LDLR and HMGCR protein in patients with ovarian cancer and their relationship with drug resistance and prognosis.Methods1.Explore the relationship between LDLR and HMGCR and the prognosis of patients with ovarian cancer.Online survival analyses were performed to determine the relationship between LDLR and HMGCR gene expression and the prognosis of ovarian cancer patients using the KM Plotter software(measured by Progression-free survival or Post-progression Survival).The ovarian cancer patients from TCGA and GEO datasets were analyzed.2.Clinical data collection and analysis.A retrospective study of 1109 patients with ovarian cancer who underwent surgical for ovarian cancer in Qilu Hospital of Shandong University from December 2013 to December 2018.Reports of laboratory investigations performed pre-and post-surgery and pre-and post-chemotherapy(plasma lipid profile,glucose,CA125),and data of pathological parameters,chemotherapy regimens and basic clinical information were obtained.Lipid profile parameters were measured by an automatic biochemistry analyzer.All laboratory tests were performed and reported as per the standard quality control procedures of the laboratory of the Shandong University.After screening,47 platinum-resistant patients and 48 platinum-sensitive ovarian cancer patients were obtained.The postoperative survival and recurrence of patients were followed up by telephone.Analyze the relationship between the above data and platinum resistance and prognosis of patients with ovarian cancer.3.Detect the expression of LDLR and HMGCR in platinum-resistant and platinum-sensitive tissues of ovarian cancer and their relationship with prognosis.Apply for pathological sections of 65 OC patients’ tumor tissues from the Department of Pathology,Qilu Hospital of Shandong University.And immunohistochemical staining assay was used to detect the differences in the expression of LDLR and HMGCR in platinum-resistant and platinum-sensitive tissues of ovarian cancer,and analyze their relationship with prognosis and platinum resistance.Results1.The relationship between LDLR and HMGCR and prognosis of ovarian cancer patients.To determine the relationship between LDLR and HMGCR gene expression and prognosis,online survival analyses were performed using the OC patients’ dataset of the TCGA and GEO datasets.The two datasets with relatively large numbers of patients treated with platinum-containing chemotherapy(GSE14764 and GSE26193)were selected for survival analysis.In TCGA dataset,patients with tumors expressing high levels of LDLR had poorer survival.In contrast,high expression of HMGCR was associated with better prognosis.Similarly,in GEO dataset,patients with tumors expressing high levels of LDLR and low levels of HMGCR had poorer survival(P<0.05).2.Analysis of clinical data of ovarian cancer patients2.1 The characteristics of patientsMedical histories of 1109 ovarian cancer patients were screened,and the data of 65 patients were finally collected.Patients were divided into two groups,based on their response to platinum-based chemotherapy:‘platinum-resistant’ which included 34 patients and ’platinum-sensitive’ which included 31 patients.The mean age of at diagnosis in platinum-sensitive patients were 55.9±10.72 and platinum-resistant patients were 53.6±8.79.The mean age of menarche in platinum-sensitive patients was significantly higher(15.93±2.97)than that of platinum-resistant patients(14.02±4.11).The difference between the two groups was statistically significant(P=0.013).A majority of cases were diagnosed at FIGO Ⅲ stage in both platinum-resistant(82.4%)and sensitive group(87.1%).The recurrence rate of the platinum-sensitive group was significantly lower than that of platinum-resistant group(P<0.001).2.2 The surgical and pathological characteristics of patientsAll 79 ovarian cancer patients with follow-up data received surgical treatment in our hospital.The operation method was mainly abdominal surgery(95%),and intraoperative greater omentum resection was performed in 63 patients(79.8%).64(81%)patients were involved in bilateral ovaries,28(35.4%)patients were involved in appendix,and 62(78.5%)patients were involved in omentum.Among the 79 ovarian cancer patients,8 cases of(10.1%)FIGO stage Ⅰ,6 cases(7.6%,)in FIGO stage Ⅱ,and 65 cases(82.3%)in FIGO stage Ⅲ.3.Serum LDL and cholesterol levels and their significance in patients with platinum-resistant OCSerum LDL and CHO levels were measured by automatic biochemical analyzer.The mean LDL and cholesterol levels(mmol/L)of 3.01±0.67 and 5.01±0.82,respectively,in platinum-sensitive patients was significantly lower than the corresponding values of 3.34± 1.01 and 5.38±1.11 in platinum-resistant patients(P<0.001).The mean TG level(mmol/L)of 1.44±0.84 in platinum-sensitive patients was also significantly different from the TG level of 1.69±0.91 in platinum-resistant patients(P=0.001).However,the levels of HDL were not statistically different between two group(P=0.209).4.Immunohistochemical analysis of LDLR and HMGCR protein expression levels in OC tissuesLDLR and HMGCR staining were observed in both resistant and sensitive ovarian cancer tissues.The LDLR was highly expressed,whereas HMGCR expression was low in patients with platinum resistance.A total of 22(64.7%)resistant patients showed high expression of LDLR and 27(79.4%)showed low expression of HMGCR.In platinum-sensitive patients,the results of immunohistochemistry were opposite.The ttest analysis showed that staining score of LDLR was higher in platinum-resistant patients(P<0.0001),and that of HMGCR was lower in platinum-resistant patients(P=0.0012).Kaplan-Meier analysis and log-rank test were performed to assess the relationship of LDLR and HMGCR protein expression with OS and DFS in OC patients.OC patients expressing high levels of LDLR had poorer DFS than patients expressing low levels of LDLR(P=0.009).A similar tendency was observed for OS(P=0.046).However,no significant association between the expression of HMGCR and OS or DFS was found(P>0.05).Conclusion1.The poor prognosis of ovarian cancer patients might be related to the high expression of LDLR and low expression of HMGCR.2.Platinum resistance in ovarian cancer was associated with high cholesterol metabolism.3.Cholesterol metabolic reprogramming might be one of the mechanisms of platinum resistance in ovarian cancer.Innovations and limitationsInnovations:The relationship between lipid metabolism-related molecules and the prognosis of ovarian cancer patients was found through bioinformatics analysis;the relationship between lipid metabolism and platinum resistance in ovarian cancer patients was further explored by using patient blood lipid profile data;immunohistochemical staining was used to verify the relationship between lipid metabolism molecular expression and prognosis in ovarian cancer tissues.Limitations:The number of samples included in immunohistochemical staining was relatively small,and further research should be expanded the sample size;this study lacks the mechanism of lipid metabolism-related molecules affecting platinum resistance,and further research is needed to clarify the possible mechanism.