==== Front Open Med (Wars) Open Med (Wars) med Open Medicine 2391-5463 De Gruyter med-2020-0139 10.1515/med-2020-0139 Research Article Analysis of expression and prognosis of KLK7 in ovarian cancer Chen Erhua 1 Zhu Huifang 1 Yang Yue Wang Ling Zhang Jianhua Han Yonghong Liu Xiang liux_cpu@163.com Department of Pharmacy and Medicine Pharmacy, Jiang Su College of nursing, Huaian, 223005, China 1 Erhua Chen and Huifang Zhu have made an equal contribution to this work. 30 9 2020 2020 15 1 932 939 06 4 2020 11 8 2020 23 8 2020 © 2020 Erhua Chen et al., published by De Gruyter2020Erhua Chen et al., published by De GruyterThis work is licensed under the Creative Commons Attribution 4.0 International License.Abstract Background Ovarian cancer is one of the common malignant tumors in female reproductive organs. Kallikrein-related peptidase (KLK) 7 is a secreted serine peptidase that is related to different cancer. To investigate the expression and significance of KLK7 in ovarian cancer. Materials and methods The expression of KLK7 in human ovarian cancer was evaluated by Oncomine and Cancer Cell Line Encyclopedia database. Then the co-expression genes relevant to the KLK7 gene were analyzed by the Pearson correlation test. Finally, the impact of KLK7 on clinical prognosis was investigated in distinct subtypes of ovarian cancer patients by UALCAN database and Kaplan–Meier plotter database. Results It was found that the expression of KLK7 was higher in ovarian cancer compared with other types of cancer, such as gastric cancer and pancreatic cancer. The expression of KLK7 was found to be increased in four various ovarian cancer data sets compared with the healthy tissues. In addition, upregulation of KLK7 expression was associated with age and cancer stage. Moreover, survival analysis revealed that higher KLK7 expression was negatively associated with progression-free survival. Conclusion Knowledge of the expression of KLK7 may be useful for better understanding the outcome in ovarian cancer patients. Keywords ovarian cancerKLK7oncomine ==== Body 1 Introduction Ovarian cancer is the highest mortality of gynecologic malignancy, and it carries a lifetime risk of approximately 2% for women [1]. As ovarian cancer is usually detected in advanced stages, it has poor prognosis even with many treatment options until now [2]. Increasing evidence has suggested that those diagnosed with early stage ovarian cancer may achieve a cure with adjuvant treatment [3]. Therefore, exploring a promising novel biomarker to improve the survival rate of ovarian cancer patients is urgent. To date, 15 kallikrein-related peptidases (KLKs) family genes are found in the human genome. All of them take part in apoptosis, digestive system enzyme activation and coagulation–fibrinolysis [4]. KLK7 is also known as human stratum corneum chymotryptic enzyme because of its early detection in human skin [5]. In breast cancer, KLK7 was significantly downregulated in the sera of breast cancer and benign breast disease patients, implying a role in the pathogenesis of infiltrating ductal carcinoma [6]. It has been reported that KLK7 and KLK10 are two of the most upregulated genes in papillary thyroid carcinoma, which are involved in cell adhesion and extracellular matrix remodeling [7]. The overexpression of KLK7 can increase the proliferation abilities and promote migration and invasive behavior in pancreatic cancer cells [8]. Wang et al. [9] identify the KLK4–7 genes exert key modulatory effects on some other cancer-related genes at the mRNA and proteins in ovarian cancer cells and tissues. KLK7 secreted in the ovarian cancer microenvironment could in turn accelerate cancer progression [10]. However, little is known about the expression and prognostic role of KLK7 in ovarian cancer. In our study, Oncomine has been systematically employed to explore the association of KLK7 mRNA expression with ovarian cancer patients. Meanwhile, the correlation of gene and the clinical value of KLK7 were shown by UALCAN database. Survival analysis of KLK7 was achieved based on Kaplan–Meier plotter. 2 Materials and methods 2.1 Oncomine analysis The Oncomine is a public cancer database (www.oncomine.org) for filtering and missing data in our needs. In this study, we set the screening criteria as follows: “Cancer Type: Ovarian cancer;” “Gene: KLK7;” “Data Type: mRNA,” “Different analysis: cancer vs. normal.” We defined the cutoff as 0.01 and 1.5 for p values and fold changes, respectively, to exam the mRNA expression status of KLK7 in different cancer types. 2.2 Cancer cell line encyclopedia (CCLE) database The CCLE database provides public access to genomic data, analysis and visualization for cell lines. The KLK7’s expression in different cell lines is verified by CCLE database. 2.3 UALCAN database UALCAN is an interactive web resource based on level 3 RNA-seq and clinical data of 31 cancer types. We analyzed the expression profiles of KLK7 in normal and ovarian serous cystadenocarcinoma samples based on clinicopathologic parameters, such as cancer stage, age, race and tumor grade. 2.4 The Kaplan–Meier plotter Kaplan–Meier plotter database was used to evaluate the prognostic significance of KLK7 mRNA expression, which provided the data on survival and gene expression. All patient were divided into two groups, according to the median expression (high and low expression), to analyze the overall survival (OS) and progression-free survival (PFS) by calculating the hazard ratio (HR), 95% confidence intervals (95% CI) and log rank p value. 3 Results 3.1 The mRNA expression levels of KLK7 in human cancers To compare the mRNA expression difference of KLK7 between tumor and normal tissues in multiple cancers, we used the Oncomine database. As shown in Figure 1, a total of 310 analyses were included for KLK7. The KLK7 mRNA expression was upregulated in 23 studies and downregulated in 35 studies. The KLK7 expression showed upregulated in cancer tissues compared to that in normal tissues. Figure 1 Transcriptional levels of KLK7 in different types of cancers (ONCOMINE). 3.2 The expression level of KLK7 mRNA in human ovarian cancer As shown in Figure 2a–d, KLK7 was found to be increased in four various cancer data sets compared with healthy tissues including ovarian serous adenocarcinoma [11] and ovarian endometrioid adenocarcinoma [12,13]. Figure 2 (a–d) Expression of KLK7 in in four various cancer data sets, (e) comparison of KLK7 across four analyses. A meta-analysis of the results of these four studies was studied. The KLK7 gene was ranked as 948.0 in all expressed genes, which means that KLK7 mRNA expression was significantly increased in two types of ovarian cancer (Figure 2e). Moreover, CCLE database analysis revealed that the mRNA expression levels of KLK7 in ovarian cancer compared with the other cancer cells. The mRNA expression of KLK7 ranks fourth highest in breast cancer and this is based on Affy gene chip data (Figure 3a). The mRNA expression of KLK7 ranks fifth highest in different tumor cell lines RNA-seq data, which is behind that of upper aerodigestive tract, bile duct, esophagus and colorectal (Figure 3b). Figure 3 (a) Expression of KLK7 based on Affy gene chip data, (b) expression of KLK7 based on RNA-seq data. 3.3 Expression correlation analysis of KLK7 in ovarian cancer We selected top two genes (KLK8 and SUPT3H) that most positively or negatively correlated with KLK7 to analysis. The klk8 gene expression level was positively correlated with the KLK7 expression with a Pearson CC value of 0.6 (Figure 4a). We observed a negative correlation between KLK7 and SUPT3H expressions with a Pearson CC value of 0.36 (Figure 4b). Figure 4 Correlation of KLK8, SUPT3H and CHEK1 gene expression in ovarian cancer. (a) Gene expression correlation between KLK7 and KLK8 in OV, (b) gene expression correlation between KLK7 and SUPT3H in OV. 3.4 Association between KLK7 gene expression and clinical pathological parameters in patients with ovarian cancer We next concentrated on the detection of KLK7 expression in normal and ovarian serous cystadenocarcinoma samples using UALCAN database. As shown in Figure 5, our analytical mining of the UALCAN database indicated that the expression level of KLK7 was higher in stage 4 compared with stages 2 and 3 of ovarian serous cystadenocarcinoma (P < 0.05) for cancer stages. Besides, KLK7 was downregulated in the age-group 81–100 years compared with those in the age-group 41–60 years (P < 0.05). Unfortunately, no significant difference was observed in the expression of the patients’ race and cancer grade. Figure 5 The relative expression of KLK7 in ovarian cancer. (a) Expression of KLK7 in OV based n individual cancer stages, (b) expression of KLK7 in OV based on patient's race, (c) expression of KLK7 in OV based on patient's age, (d) expression of KLK7 in OV based on tumor grade. 3.5 KLK7 expression was correlated with the survival of ovarian cancer To further assess the prognostic value of KLK7 in ovarian cancer, the KLK7 mRNA expression was evaluated; the Affymetrix ID was 239381_at KLK7. High KLK7 mRNA expression indicated unfavorable PFS for all patients with ovarian cancer (HR, 1.67; 95% CI, 1.38–2.02; P = 1.3 × 10−07; Figure 6a), patients with serous ovarian cancer (HR, 1.43; 95% CI, 1.16–1.77; P = 0.00084; Figure 6b) and patients with endometrioid ovarian cancer (HR, 5.05; 95% CI, 1.74–14.65; P = 0.00095; Figure 6c). KLK7 exhibited no association with OS in patients with serous ovarian cancer (Figure 7a), serous ovarian cancer (Figure 7b) and endometrioid ovarian cancer (Figure 7c). Although KLK7 expression was not significantly correlated with poor OS, the higher expression of KLK7 in all patients with ovarian cancers is significantly correlated with better PFS (P < 0.05). Figure 6 Prognostic value of KLK7 expression for OS of patients with ovarian cancer based on the Kaplan–Meier plotter. (a) All KLK7 (239381_at), (b) serous KLK7 (239381_at), (c) endometrioid KLK7 (239381_at). Figure 7 Prognostic value of KLK7 expression for PFS in patients with ovarian cancer based on the Kaplan–Meier plotter. (a) All KLK7 (239381_at), (b) serous KLK7 (239381_at), (c) endometriod KLK7 (239381_at). 4 Discussion Most ovarian cancer patients cannot be cured completely, even with the combination of cytoreductive surgery and chemotherapy drugs [14]. Based on tissue analysis, KLK7 was found in both stromal and tumor cells, whose expression was higher in tumor cells [15,16]. Studies have found that KLK7 increases the expression of integrity adhesion receptors and both forms of the produced serine proteases (KLK7 and the nonproteolytic form) work in ovarian cancer peritoneal invasion [17]. Although some other studies have indicated that different members of KLK family associated with specific cancers and KLK7 as preferred targets for inhibition of ovarian cancer, the distinct role of KLK7 remains to be elucidated [18,19]. In our study, the expression and prognostic of KLK7 were systematically identified by several online databases. Many studies have reported that KLK7 is overexpressed in healthy tissue than in tumors of ovarian cancer patients and have linked with the some other diseases [20,21] We first systematically analyzed the expression of KLK7 in different cancers using ONCOMINE, and our results confirmed that KLK7 was overexpressed in ovarian cancer, colorectal cancer and gastric cancer. Subsequently, our analysis suggested that high expression of KLK7 in ovarian cancer compared to normal controls among four data sets (Figure 2a–d). By the comparison of KLK7 expression in four data sets, meta-analysis demonstrated that KLK7 was significantly increased in two types of ovarian cancer, namely, ovarian serous adenocarcinoma and ovarian endometrioid adenocarcinoma (Figure 2e). Additionally, KLK7 was also highly expressed in human ovarian cancer cell lines, as implicated by CCLE database, supporting the critical role of KLK7 in ovarian cancer initiation or progression (Figure 3a and b). Tamir et al. [22] suggested that KLK7 mRNA and protein overexpression are directly associated with early stage ovarian carcinomas and can be measured in patient tissue and serum samples. Further, Kyriakopoulou et al. [23] reported overexpressed KLK7 in ovarian cancer had an association with those high tumor grade diseases. In our report, we demonstrated that the expression of KLK7 was higher in a range of 41–60 years cancer stage. Previous studies indicated that high KLK7 expression was significantly associated with prolonged OS and PFS [24]. Then we evaluated whether overexpression of KLK7 was associated with clinicopathological features and survival outcomes by Kaplan–Meier plotter database. In contrast to this result, our finding revealed that overexpressed KLK7 was significantly associated with worse FPS in ovarian cancer. Our study has certain limitations. It was only analyzed by online databases, and experimental or clinical validation would be needed to confirm the expression of KLK7 in ovarian cancer. More investigations should focus on a functional characterization and molecular mechanisms of the upregulated or downregulated factors in other significant KLK7 family members that are involved in KLK-mediated functions. In addition, we did not assess the potential diagnostic and therapeutic effect and explore whether it can be used as diagnostic markers or treatment. Taken together, we identified KLK7 gene is potentially involved in prognosis through bioinformatics analysis. KLK7 gene should be considered as potential prognostic biomarker for a better understanding of ovarian cancer progression and therapy. Conflict of interest: Authors state no conflict of interest. ==== Refs References [1] Carlo VL. Ovarian cancer: epidemiology and risk factors. Eur J Cancer Prev. 2017;26:55–62.Carlo VL Ovarian cancer: epidemiology and risk factors Eur J Cancer Prev 2017 26 55 62 26731563 [2] Pal P, Hales K, Petrik J, Hales B. Pro-apoptotic and anti-angiogenic actions of 2-methoxyestradiol and docosahexaenoic acid, the biologically derived active compounds from flaxseed diet, in preventing ovarian cancer. J Ovarian Res. 2019;12:49.Pal P Hales K Petrik J Hales B Pro-apoptotic and anti-angiogenic actions of 2-methoxyestradiol and docosahexaenoic acid, the biologically derived active compounds from flaxseed diet, in preventing ovarian cancer J Ovarian Res 2019 12 49 31128594 [3] Suhburgmann E, Alavi M. Detection of early stage ovarian cancer in a large community cohort. Cancer Med. 2019;8:7133–40.Suhburgmann E Alavi M Detection of early stage ovarian cancer in a large community cohort Cancer Med 2019 8 7133 40 31568690 [4] Prassas I, Eissa A, Poda G, Diamandis EP. Unleashing the therapeutic potential of human kallikrein-related serine proteases. Nat Rev Drug Discovery. 2015;14:183–202.Prassas I Eissa A Poda G Diamandis EP Unleashing the therapeutic potential of human kallikrein-related serine proteases Nat Rev Drug Discovery 2015 14 183 202 25698643 [5] Hansson L, Stromqvist M, Backman A, Wallbrandt P, Carlstein A, Egelrud T. Cloning, expression, and characterization of stratum corneum chymotryptic enzyme. A skin-specific human serine proteinase. J Biol Chem. 1994;269:19420–6.Hansson L Stromqvist M Backman A Wallbrandt P Carlstein A Egelrud T Cloning, expression, and characterization of stratum corneum chymotryptic enzyme. A skin-specific human serine proteinase J Biol Chem 1994 269 19420 6 8034709 [6] Ejaz S, Nasim F, Ashraf M, Ahmad G. Down-regulation of hK7 in the sera of breast cancer and benign breast disease patients. Heliyon. 2017;3:e00356.Ejaz S Nasim F Ashraf M Ahmad G Down-regulation of hK7 in the sera of breast cancer and benign breast disease patients Heliyon 2017 3 e00356 28761938 [7] Reyes I, Reyes N, Suriano R, Iacob C, Suslina N, Policastro A, et al. Gene expression profiling identifies potential molecular markers of papillary thyroid carcinoma. Crim Behav Ment Health. 2019;24:71–83.Reyes I Reyes N Suriano R Iacob C Suslina N Policastro A Gene expression profiling identifies potential molecular markers of papillary thyroid carcinoma Crim Behav Ment Health 2019 24 71 83 [8] Zheng SL, Feng MY, Yang G, Xiong GB, Zheng LF, Zhang T, et al. The expression of KLK7 in pancreatic cancer and the effects on the biological behavior of pancreatic cancer cells. Chin J Surg. 2018;56:391–7.Zheng SL Feng MY Yang G Xiong GB Zheng LF Zhang T The expression of KLK7 in pancreatic cancer and the effects on the biological behavior of pancreatic cancer cells Chin J Surg 2018 56 391 7 29779317 [9] Wang P, Magdolen V, Seidl C, Dorn J, Drecoll E, Kotzsch M, et al. Kallikrein-related peptidases 4, 5, 6 and 7 regulate tumour-associated factors in serous ovarian cancer. Br J Cancer. 2018;119:1–9.Wang P Magdolen V Seidl C Dorn J Drecoll E Kotzsch M Kallikrein-related peptidases 4, 5, 6 and 7 regulate tumour-associated factors in serous ovarian cancer Br J Cancer 2018 119 1 9 [10] Silva LM, Kryza T, Stoll T, Hoogland C, Dong Y, Stephens C, et al. Integration of two in-depth quantitative proteomics approaches determines the kallikrein-related peptidase 7 (KLK7) degradome in ovarian cancer cell secretome. Mol Cell Proteom. 2019;18:818–36.Silva LM Kryza T Stoll T Hoogland C Dong Y Stephens C Integration of two in-depth quantitative proteomics approaches determines the kallikrein-related peptidase 7 (KLK7) degradome in ovarian cancer cell secretome Mol Cell Proteom 2019 18 818 36 [11] Lu KH, Patterson AP, Wang L, Marquez RT, Atkinson EN, Baggerly KA, et al. Selection of potential markers for epithelial ovarian cancer with gene expression arrays and recursive descent partition analysis. Clin Cancer Res. 2004;10:3291–300.Lu KH Patterson AP Wang L Marquez RT Atkinson EN Baggerly KA Selection of potential markers for epithelial ovarian cancer with gene expression arrays and recursive descent partition analysis Clin Cancer Res 2004 10 3291 300 15161682 [12] Yoshihara K, Tajima A, Komata D, Yamamoto T, Kodama S, Fujiwara H, et al. Gene expression profiling of advanced-stage serous ovarian cancers distinguishes novel subclasses and implicates ZEB2 in tumor progression and prognosis. Cancer Sci. 2009;100:1421–8.Yoshihara K Tajima A Komata D Yamamoto T Kodama S Fujiwara H Gene expression profiling of advanced-stage serous ovarian cancers distinguishes novel subclasses and implicates ZEB2 in tumor progression and prognosis Cancer Sci 2009 100 1421 8 19486012 [13] Hendrix ND, Wu R, Kuick R, Schwartz DR, Fearon ER, Cho KR. Fibroblast growth factor 9 has oncogenic activity and is a downstream target of Wnt signaling in ovarian endometrioid adenocarcinomas. Cancer Res. 2006;66:1354–62.Hendrix ND Wu R Kuick R Schwartz DR Fearon ER Cho KR Fibroblast growth factor 9 has oncogenic activity and is a downstream target of Wnt signaling in ovarian endometrioid adenocarcinomas Cancer Res 2006 66 1354 62 16452189 [14] Mcguire WP, Hoskins WJ, Brady MF, Kucera PR, Davidson M. Cyclophosphamide and cisplatin compared with paclitaxel and cisplatin in patients with stage iii and stage iv ovarian cancer. N Engl J Med. 1996;334:1–6.Mcguire WP Hoskins WJ Brady MF Kucera PR Davidson M Cyclophosphamide and cisplatin compared with paclitaxel and cisplatin in patients with stage iii and stage iv ovarian cancer N Engl J Med 1996 334 1 6 7494563 [15] Dorn J, Gkazepis A, Kotzsch M, Kremer M, Propping C, Mayer K, et al. Clinical value of protein expression of kallikrein-related peptidase 7 (klk7) in ovarian cancer. Biol Chem. 2014;395:95–107.Dorn J Gkazepis A Kotzsch M Kremer M Propping C Mayer K Clinical value of protein expression of kallikrein-related peptidase 7 (klk7) in ovarian cancer Biol Chem 2014 395 95 107 23999494 [16] Dorn J, Yassouridis A, Walch A, Diamandis EP, Schmitt M, Kiechle M, et al. Assessment of kallikrein-related peptidase 5 (klk5) protein expression in tumor tissue of advanced ovarian cancer patients by immunohistochemistry and ELISA: correlation with clinical outcome. Am J Cancer Res. 2015;6:61.Dorn J Yassouridis A Walch A Diamandis EP Schmitt M Kiechle M Assessment of kallikrein-related peptidase 5 (klk5) protein expression in tumor tissue of advanced ovarian cancer patients by immunohistochemistry and ELISA: correlation with clinical outcome Am J Cancer Res 2015 6 61 27073723 [17] Dong Y, Tan OL, Loessner D, Stephens C, Walpole C, Boyle GM, et al. Kallikrein-related peptidase 7 promotes multicellular aggregation via the? 5? 1 integrin pathway and paclitaxel chemoresistance in serous epithelial ovarian carcinoma. Cancer Res. 2010;70:2624–33.Dong Y Tan OL Loessner D Stephens C Walpole C Boyle GM Kallikrein-related peptidase 7 promotes multicellular aggregation via the? 5? 1 integrin pathway and paclitaxel chemoresistance in serous epithelial ovarian carcinoma Cancer Res 2010 70 2624 33 20332224 [18] Daniela L, Peter G, Sarah P, Johanna F, Holger B, Clements JA, et al. Kallikrein-related peptidases represent attractive therapeutic targets for ovarian cancer. Expert Opin Ther Targets. 2018;22:745–63.Daniela L Peter G Sarah P Johanna F Holger B Clements JA Kallikrein-related peptidases represent attractive therapeutic targets for ovarian cancer Expert Opin Ther Targets 2018 22 745 63 30114962 [19] Dong Y, Kaushal A, Brattsand M, Nicklin J, Clements JA. Differential splicing of klk5 and klk7 in epithelial ovarian cancer produces novel variants with potential as cancer biomarkers. Clin Cancer Res an Off J Am Assoc Cancer Res. 2003;9:1710–20.Dong Y Kaushal A Brattsand M Nicklin J Clements JA Differential splicing of klk5 and klk7 in epithelial ovarian cancer produces novel variants with potential as cancer biomarkers Clin Cancer Res an Off J Am Assoc Cancer Res 2003 9 1710 20 [20] Girgis A, Bui A, White NM, Yousef GM. Integrated genomic characterization of the Kallikrein gene locus in cancer. Anticancer Res. 2012;32:957–63.Girgis A Bui A White NM Yousef GM Integrated genomic characterization of the Kallikrein gene locus in cancer Anticancer Res 2012 32 957 63 22399617 [21] Psyrri A, Kountourakis P, Scorilas A, Markakis S, Camp R, Kowalski D, et al. Human tissue kallikrein 7, a novel biomarker for advanced ovarian carcinoma using a novel in situ quantitative method of protein expression. Ann Oncol. 2008;19:1271–7.Psyrri A Kountourakis P Scorilas A Markakis S Camp R Kowalski D Human tissue kallikrein 7, a novel biomarker for advanced ovarian carcinoma using a novel in situ quantitative method of protein expression Ann Oncol 2008 19 1271 7 18325919 [22] Tamir A, Jag U, Sarojini S, Schindewolf C, Tanaka T, Gharbaran R, et al. Kallikrein family proteases klk6 and klk7 are potential early detection and diagnostic biomarkers for serous and papillary serous ovarian cancer subtypes. J Ovarian Res. 2014;7:109.Tamir A Jag U Sarojini S Schindewolf C Tanaka T Gharbaran R Kallikrein family proteases klk6 and klk7 are potential early detection and diagnostic biomarkers for serous and papillary serous ovarian cancer subtypes J Ovarian Res 2014 7 109 25477184 [23] Kyriakopoulou LG, Yousef GM, Scorilas A, Katsaros D, Massobrio M, Fracchioli S, et al. Prognostic value of quantitatively assessed klk7 expression in ovarian cancer. Clin Biochem. 2003;36:135–43.Kyriakopoulou LG Yousef GM Scorilas A Katsaros D Massobrio M Fracchioli S Prognostic value of quantitatively assessed klk7 expression in ovarian cancer Clin Biochem 2003 36 135 43 12633763 [24] Dorn J, Gkazepis A, Kotzsch M, Kremer M, Propping C, Mayer K, et al. Clinical value of protein expression of kallikrein-related peptidase 7 (klk7) in ovarian cancer. Biol Chem. 2014;395:95–107.Dorn J Gkazepis A Kotzsch M Kremer M Propping C Mayer K Clinical value of protein expression of kallikrein-related peptidase 7 (klk7) in ovarian cancer Biol Chem 2014 395 95 107 23999494