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© 2003 American Society for Clinical Oncology Human Kallikrein 6 (hK6): A New Potential Serum Biomarker for Diagnosis and Prognosis of Ovarian Carcinoma
From the Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; National Center for Scientific Research "Demokritos," IPC, Athens, Greece; Department of Obstetrics and Gynecology, Gynecologic Oncology Unit, University of Turin, Turin, Italy; Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Leuven, Belgium; Department of Obstetrics and Gynecology, University Hospital Groningen, The Netherlands; and Department of Clinical Chemistry, Helsinki University Central Hospital, Helsinki, Finland. Address reprint requests to E. P. Diamandis, MD, Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada; email: ediamandis{at}mtsinai.on.ca.
Purpose: The discovery of new ovarian cancer biomarkers that are suitable for early disease diagnosis and prognosis may ultimately lead to improved patient management and outcomes. Patients and Methods: We measured, by immunoassay, human kallikrein 6 (hK6) concentration in serum of 97 apparently healthy women, 141 women with benign abdominal diseases, and 146 women with histologically proven primary ovarian carcinoma. We then calculated the diagnostic sensitivity and specificity of this test and examined the association of serum hK6 concentration with various clinicopathologic variables and patient survival. Results: Serum hK6 concentration between normal and benign disease patients was not different (mean, 2.9 and 3.1 µg/L, respectively). However, hK6 in presurgical serum of ovarian cancer patients was highly elevated (mean, 6.8 µg/L; P < .001). Serum hK6 decreased after surgery (to a mean of 3.9 µg/L) in 68% of patients. The diagnostic sensitivity of serum hK6 at 90% and 95% specificity is 52% and 47%, respectively, in the whole patient population. For early stage disease (stage I or II), sensitivity is approximately 21% to 26%. When combined with CA-125, at 90% specificity, sensitivity increases to 72% (for all patients) and to 42% in stage I or II disease. Serum hK6 concentration correlates moderately with CA-125 and is higher in patients with late-stage, higher-grade disease and in patients with serous histotype. Preoperative serum hK6 concentration is a powerful predictor of disease-free and overall survival in both univariate and multivariate analyses. Conclusions: Serum hK6 concentration seems to be a new biomarker for ovarian carcinoma and may have value for disease diagnosis and prognosis.
OVARIAN CANCER kills more women in North America than all other gynecological malignancies combined. The American Cancer Society estimates that 23,400 new cases of ovarian cancer will be diagnosed in 2001 and 13,900 deaths will result from the disease.1 The high fatality-to-case ratio associated with ovarian cancer is partially caused by the lack of a recognizable pattern of symptoms in its early stages; 70% of women with ovarian cancer are diagnosed with advanced stage disease. This disease has a 5-year survival rate of 85% if diagnosed early (stage I or II carcinoma), but survival decreases to less than 20% in women presenting with stage III or IV disease.2 Clearly, the development of new methods for early ovarian cancer diagnosis will likely contribute to improved patient outcomes. The only well-validated ovarian cancer tumor marker, CA-125, was discovered about 20 years ago.3,4 CA-125 has clinical value for disease monitoring, and it is used as an aid for the early detection of relapse and for assessing response to treatment.5–7 CA-125 also has some prognostic value8 and can aid in disease diagnosis.4,9 More recently, the diagnostic value of CA-125 was shown to be improved by combination of markers, including CA-125 plus D-dimer10 or CA-125 plus OVX1, LASA, CA 15–3, CA 72–4, and prostasin.11–13 The application of CA-125 for screening asymptomatic individuals has been reported,11,14–17 but its value is still under investigation. The sequencing of the human genome has raised hopes that new cancer biomarkers may soon be discovered. By using whole-genome mining approaches, investigators have identified many candidate biomarkers for ovarian cancer diagnosis and prognosis.13,18–20 It is now believed that the discovery of new biomarkers may ultimately lead to cancer-specific panels, which, when used with artificial network approaches, may bring about high specificity and sensitivity for cancer classification, diagnosis, and prognosis.18–21 The human kallikrein gene family consists of 15 genes, all tandemly localized on chromosome 19q13.4.22,23 All genes encode for secreted serine proteases of relatively low molecular mass (approximately 30 kd). Among these kallikreins, prostate-specific antigen (PSA) is the best cancer marker.24,25 In addition, human glandular kallikrein 2 (hK2) is an emerging prostate cancer marker.26 Recently, we reported preliminarily that human kallikrein 6 (hK6) is a potential serological marker for ovarian carcinoma.27 Indeed, many kallikreins seem to be disregulated in ovarian cancer, and their transcript levels seem to have either favorable or unfavorable prognostic value.28–36 This article examines in detail the diagnostic and prognostic value of serum hK6 levels in ovarian carcinoma.
Patient Population Included in this study were 97 apparently healthy women (ages 26 to 72 years; mean, 52 years; median, 49 years), 141 women with benign diseases (ages 21 to 76 years; mean, 46 years; median, 45 years), and 146 women with histologically proven primary ovarian carcinoma (ages 28 to 78 years; mean, 56 years; median, 57 years). Of the benign lesions, 50 were classified as endometriosis, 22 as mucinous cystadenomas, 26 as ovarian dermoid cysts, 10 as ovarian benign teratomas, 15 as corpus luteum, and 18 as serous cystadenomas. Malignant tumors were staged according to the International Federation of Gynecology and Obstetrics criteria. Histologic classification was based on the World Health Organization and International Federation of Gynecology and Obstetrics recommendations. The characteristics of the ovarian cancer patients in terms of stage, grade, histotype, residual tumor after surgery (debulking success) menopausal status, and response to chemotherapy are described later. Serum samples from all patients were collected before surgery, before initiation of therapy and stored at -80°C until analysis. For 105 ovarian cancer patients, serum was also available after surgery. This sample was obtained approximately 2 to 3 weeks after surgery. Sera were obtained from four centers as follows: the Gynecologic Oncology Unit, University of Turin, Italy (20 cancers, 25 benigns, 40 controls); the Department of Obstetrics and Gynecology, University Hospital Groningen, the Netherlands (41 cancers, 30 benigns, 20 controls); the Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Leuven, Belgium (46 cancers, 22 benigns, 15 controls); and the Department of Clinical Chemistry, Helsinki University Central Hospital, Finland (39 cancers, 64 benigns, 22 controls). Our protocols have been approved by the review boards of all participating institutions. All patients were treated with platinum-based chemotherapy, and response to treatment was assessed as described elsewhere.36 Follow-up information was available for 131 of the ovarian cancer patients with a median follow-up of 25 months and a range of 1 to 106 months. Sixty-four (49%) of these patients relapsed and 28 (21%) died during the course of the follow-up period.
Analysis of hK6 and CA-125
Statistical Analysis
Receiver operating characteristic (ROC) curves were constructed for hK6 and CA-125 serum concentration by plotting sensitivity versus 1-specificity, and the areas under the ROC curves (AUC) were calculated. The noncancer group included the normal individuals and the patients with benign disease. Correlations between different variables were assessed by the Pearson correlation coefficient on log-transformed data. Analysis of variance (ANOVA) was used to determine differences between two or more groups. These tests treated log(hK6) concentration in serum as a continuous variable. hK6 serum concentration was also classified as either hK6-positive (> 4.2 or 4.4 µg/L) or hK6-negative ( Kaplan-Meier progression-free survival (PFS) and overall survival (OS) curves were constructed to demonstrate the survival differences between the hK6-positive and hK6-negative patients. The log-rank test was used to examine the significance of the differences among the survival curves. The effect of serum log(hK6) concentration on patient OS and on progression of the disease was assessed with the hazards ratio, calculated by both univariate and multivariate Cox proportional hazards regression models. In the multivariate analysis, the clinical and pathologic variables that may affect survival, including stage of disease, tumor grade, residual tumor, and histologic type, were included in the model to adjust for their impact.
Serum hK6 Concentration in Cancer and Noncancer Patients The mean, median, range, and selected percentiles of serum hK6 concentration among noncancer (normal; n = 97), benign disease (n = 141), presurgical (n = 146), and postsurgical (n = 105) ovarian cancer patients is shown in Table 1  . The mean and median values between noncancer and benign disease patients were not statistically significant. Statistically significant associations between serum hK6 concentration and the subtypes of benign gynecologic diseases were not observed. A P value of .56 was calculated using ANOVA analysis and log(hK6) values. The mean and median hK6 values in presurgical ovarian cancer patients were significantly higher than those in the noncancer and benign groups (P < .001). The distribution of hK6 concentration in the three groups of patients is presented in Fig 1 along with the corresponding CA-125 values. Presurgical serum hK6 concentration is not different between normal and benign disease patients but is significantly elevated in a proportion of ovarian cancer patients. CA-125 values are progressively increased from normal to benign to cancer patients.
For dichotomous classification of this patient population as hK6-positive and hK6-negative, we selected the hK6 cutoffs of 4.2 µg/L (90% diagnostic specificity) and 4.4 µg/L (95% diagnostic specificity).
Changes of Serum hK6 Concentration After Surgery
Correlation Between Serum hK6 and CA-125 Concentration The logarithmic plot of Fig 3 shows the correlation between serum log(hK6) and log(CA-125) concentration (Pearson correlation rp = 0.61 for the cases, -0.052 for the benign subjects, and 0.153 for the control subjects). Although the correlation in cancer patients is significant (P < .001), there are still many samples with quite variable values. For example, at CA-125 levels of approximately 500 KU/L, hK6 concentration ranges from 2 to 40 µg/L, whereas samples with hK6 levels of approximately 6 µg/L may have CA-125 values ranging from 5 to more than 5,000 KU/L.
Diagnostic Sensitivity and Specificity of Serum hK6 Concentration For this calculation, we considered various subgroups of patients, as shown in Table 2 . In the noncancer group, we have included all patients who are either normal or have benign disease. When the whole patient group was analyzed, diagnostic sensitivity was around 52% at 90% specificity and 47% at 95% specificity. The ROC curve of Fig 4 indicates a slight diagnostic advantage of CA-125 in comparison with hK6. In the subgroup of patients with CA-125 more than 60 KU/L, the diagnostic sensitivity of hK6 is 71% and 65% at specificities of 90% and 95%, respectively. In the subgroup of patients with low CA-125 (< 23 KU/L), approximately 13% to 17% of patients will still have elevated hK6, at hK6 cutoffs of 4.4 (95% specificity) or 4.3 µg/L (90% specificity), respectively. In the subgroup of patients with slightly elevated CA-125 (23 to 60 KU/L), the diagnostic sensitivity of hK6 is 15% to 26% at specificities of 95% to 90%, respectively (Table 2). However, the two markers can be combined to improve sensitivity by developing a logistic regression model with the terms log(hK6) and log(CA-125). We derived the combination function, f(x) = 3.95 log(hK6) + 1.97 log(CA-125), and performed ROC analysis, which supported the added value of using both variables together, in a multivariate function.
In Table 3 , we calculated the additional contribution of hK6 in identifying ovarian cancer patients by using CA-125 and hK6 alone and in combination at 90% and 95% specificity. Among all patients with known stage (N = 124), hK6 analysis increases the sensitivity of CA-125 by 12% or 13%, at 90% or 95% specificity cutoffs, respectively, for both markers. The addition of hK6 increases the sensitivity of CA-125 alone from 30% to 42%, or from 26% to 37%, at 90% or 95% specificity cutoffs for both markers, respectively, for ovarian cancer stages I or II.
Table 4 summarizes the relative risk (RR) of having ovarian cancer, based on serum hK6 concentration using the ovarian cancer and the combined control and benign groups. The RR increases exponentially with increasing hK6 concentration, reaching a value of 20 when hK6 is  4.3 µg/L. The RR is still substantial (RR = 5.3) in multivariate analysis, after adjusting for CA-125 levels.
Prognostic Value of Serum hK6 Higher ovarian cancer stage and grade are strongly associated with higher serum hK6 concentration (Fig 5 and Table 5). Furthermore, serous adenocarcinomas are more frequently associated with high serum hK6 concentration (positivity 68%) followed by endometrioid tumors (positivity 33%); mucinous tumors are rarely associated with high serum hK6 (9%). Furthermore, high serum hK6 concentration is associated with the presence of residual tumor, suboptimal debulking, and poor response to chemotherapy. All of these associations were highly significant (P < .001).
In univariate Cox analysis, serum hK6 concentration is associated with shorter PFS and OS (Table 6 ). These associations remained statistically significant in the multivariate analysis. The multivariate Cox model was adjusted for hK6 status, CA-125 status, clinical stage, histological type, grade, and residual tumor size. The prognostic value of CA-125 was no longer statistically significant in the multivariate analysis. In addition to presurgical serum hK6, stage of disease was the only other parameter that was associated with both PFS and OS in multivariate analysis.
Similar data were obtained with Kaplan-Meier survival analysis (Fig 6 ). Patients with high presurgical serum hK6 have much shorter PFS and OS than patients with low preoperative hK6 levels. Although all patients with high serum hK6 relapsed by 6 years, more than 50% of patients with low preoperative serum hK6 were still in remission.
The discovery of new ovarian cancer biomarkers for early diagnosis, prognosis, monitoring, and prediction of therapeutic response may contribute to improved clinical outcomes. The only well-accepted ovarian cancer biomarker, CA-125, was discovered 20 years ago. A number of other potential ovarian cancer biomarkers have been identified, but their clinical value is not established.1,10–13,20,38 This article describes a novel ovarian cancer biomarker, hK6, a member of the expanded human kallikrein gene family. The traditional ovarian cancer biomarker, CA-125, falls short of being able to diagnose early ovarian cancer effectively.39 In addition to its low sensitivity for early disease, CA-125 also suffers from low specificity; that is, elevated levels are seen in many benign gynecological diseases.39 At present, it is widely accepted that no single cancer biomarker will provide all of the necessary information for optimal cancer diagnosis and management. The current trend is to focus on the identification of multiple biomarkers that can be used in combination. Such approaches have already been shown to have clinical potential in ovarian cancer.11–13 Other issues related to ovarian cancer screening by using biomarkers as well as other modalities have been addressed in excellent recent reviews and editorials.16,38–40
Serum hK6 represents a novel biomarker for ovarian carcinoma. This biomarker is more specific for ovarian cancer than CA-125 because elevations were not seen in benign diseases (Fig 1
Similar to CA-125, hK6 is more frequently elevated in serous ovarian carcinoma than in endometrioid and mucinous carcinomas (Table 5
The data of Table 5
Serum hK6 likely originates from tumor cells because postoperatively, the levels are significantly decreased (Fig 2
In this article, we did not address the issues of ovarian cancer monitoring by measuring serum hK6 concentration or the possible elevations of serum hK6 in other cancers. In our previous preliminary investigation,27 we showed examples of ovarian cancer patient monitoring with serum hK6. A more detailed study will be necessary to address the issue of monitoring patients whose tumors do not produce CA-125 but do still secrete hK6. As indicated in Table 2
Table 5 In conclusion, we show evidence that serum hK6 concentration represents a novel biomarker for ovarian carcinoma, which has potential utility as a diagnostic, prognostic, and predictive tool. The combination of hK6 and CA-125 improves the diagnostic sensitivity of ovarian cancer at all stages, including early-stage disease. The current availability of a simple and reliable immunoassay for measuring serum hK6 concentration37 will facilitate further studies to establish the clinical usefulness of serum hK6 analysis for the management of patients with ovarian carcinoma.
Supported by the Early Detection Research Network (EDRN) of the National Cancer Institute (Grant No. 1CFAMA-10047), the Italian Association for Cancer Research (AIRC), and OncoTherapeutics Inc., Toronto, Canada. Dr. Diamandis is a Consultant of OncoTherapeutics Inc.
1. Greenlee RT, Hill Harmon M, Murray T, et al: Cancer statistics 2001. CA Cancer J Clin 51:15–36, 2001 2. Myer T, Rustin GJS: Role of tumor markers in monitoring epithelial ovarian cancer. Br J Cancer 82:1535–1538, 2000[CrossRef][Medline] 3. Bast RC, Feeny M, Lazarus H, et al: Reactivity of a monoclonal antibody with human ovarian carcinoma. J Clin Invest 68:1331–1337, 1981[Medline] 4. Bast RC, Klug TL, John ES, Al E: A radioimmunoassay using a monoclonal antibody to monitor the course of epithelial ovarian cancer. N Engl J Med 309:883–887, 1983[Abstract] 5. Rustin GJ, Nelstrop A, Stilwell J, et al: Savings obtained by CA125 measurements during therapy for ovarian carcinoma. The North Thames Ovary Group. Eur J Cancer 28:79–82, 1992[CrossRef][Medline]
6. Rustin GJ, Nelstrop AE, McClean P, et al: Defining response of ovarian carcinoma in initial chemotherapy according to serum CA125. J Clin Oncol 14:1545–1551, 1996
7. Eisenhauer EA, Vermorken JB, van Glabbeke M: Predictors of response to subsequent chemotherapy in platinum pretreated ovarian cancer. A multivariate analysis of 704 patients. Ann Oncol 8:963–968, 1997 8. Nagele F, Petru E, Medl M, et al: Preoperative CA125: An independent prognostic factor in patients with stage I epithelial ovarian cancer. Obstet Gynecol 86:259–264, 1995[CrossRef][Medline] 9. Jacobs I, Oram D, Fairbanks J, et al: A risk of malignancy index incorporating CA125, ultrasound and menopausal status for the accurate preoperative diagnosis of ovarian cancer. Br J Obstet Gynaecol 97:922–929, 1990[Medline] 10. Gadducci A, Baichhi U, Marrai R, et al: Preoperative evaluation of D-dimer and CA125 levels in differentiating benign from malignant ovarian masses. Gynecol Oncol 60:197–202, 1996[CrossRef][Medline]
11. Woolas RP, Xu FJ, Jacobs IJ, et al: Elevation of multiple serum markers in patients with stage I ovarian cancer. J Natl Cancer Inst 85:1748–1751, 1993 12. Woolas RP, Conaway MR, Xu F, et al: Combinations of multiple serum markers are superior to individual assays for discriminating malignant from benign pelvic masses. Gynecol Oncol 59:111–116, 1995[CrossRef][Medline]
13. Mok SC, Chao J, Skates S, et al: Prostasin, a potential serum marker of ovarian cancer: Identification through microarray technology. J Natl Cancer Inst 93:1458–1464, 2001 14. Einhorn N, Sjovall K, Knapp RC, et al: Prospective evaluation of serum CA125 levels for early detection of ovarian cancer. Obstet Gynecol 80:14–18, 1992[Medline]
15. Jacobs I, Davies AP, Bridges J, et al: Prevalence screening for ovarian cancer in postmenopausal women by CA125 measurement and ultrasonography. Br Med J 306:1030–1032, 1993 16. Jacobs IJ, Skates SJ, MacDonald N, et al: Screening for ovarian cancer: A pilot randomised controlled trial. Lancet 353:1207–1210, 1999[CrossRef][Medline] 17. Skates SJ, Xu F, Yu Y, et al: Toward an optimal algorithm for ovarian cancer screening with longitudinal tumour markers. Cancer 76:2004–2010, 1995[CrossRef][Medline]
18. Welsh JB, Zarrinkar PP, Sapinoso LM, et al: Analysis of gene expression profiles in normal and neoplastic ovarian tissue samples identifies candidate molecular markers of epithelial ovarian cancer. Proc Natl Acad Sci U S A 98:1176–1181, 2001 19. Schummer M, Ng WV, Bumgarner RE, et al: Comparative hybridization of an array of 21,500 ovarian cDNAs for the discovery of genes overexpressed in ovarian carcinomas. Gene 238:375–385, 1999[CrossRef][Medline]
20. Kim JH, Skates SJ, Uede T, et al: Osteopontin as a potential diagnostic biomarker for ovarian cancer. J Am Med Assoc 287:1671–1679, 2002 21. Khan J, Wei JS, Ringner M, et al: Classification and diagnostic prediction of cancers using gene expression profiling and artificial neural networks. Nat Med 7:673–679, 2001[CrossRef][Medline] 22. Diamandis EP, Yousef GM, Luo LY, et al: The human kallikrein gene family—implications in carcinogenesis. Trends Endocrinol Metab 11:54–60, 2000[CrossRef][Medline]
23. Yousef GM, Diamandis EP: The new human tissue kallikrein gene family: Structure, function and association to disease. Endocr Rev 22:184–204, 2001 24. Diamandis EP: Prostate specific antigen—its usefulness in clinical medicine. Trends Endocrinol Metab 9:310–316, 1998[CrossRef][Medline]
25. Barry MJ: Clinical practice: Prostate-specific antigen testing for early diagnosis of prostate cancer. N Engl J Med 344:1373–1377, 2001 26. Rittenhouse HG, Finlay JA, Mikolzjczyk SD, et al: Human kallikrein 2 (hK2) and prostate-specific antigen (PSA): Two closely related, but distinct, kallikreins in the prostate. Crit Rev Clin Lab Sci 35:275–368, 1998[CrossRef][Medline] 27. Diamandis EP, Yousef GM, Soosaipillai AR, et al: Human kallikrein 6 (zyme/protease M/neurosin): A new serum biomarker of ovarian carcinoma. Clin Biochem 33:579–583, 2000[CrossRef][Medline]
28. Obiezu CV, Scorilas A, Katsaros D, et al: Higher human kallikrein gene 4 (KLK4) expression indicates poor prognosis of ovarian cancer patients. Clin Cancer Res 7:2380–2386, 2001 29. Kim H, Scorilas A, Katsaros D, et al: Human kallikrein gene 5 (KLK5) expression is an indicator of poor prognosis in ovarian cancer. Br J Cancer 84:643–650, 2001[CrossRef][Medline]
30. Magklara A, Scorilas A, Katsaros D, et al: The human KLK8 (neuropsin/ovasin) gene: Identification of two novel splice variants and its prognostic value in ovarian cancer. Clin Cancer Res 7:806–811, 2001
31. Luo LY, Katsaros D, Scorilas A, et al: Prognostic value of human kallikrein 10 expression in epithelial ovarian carcinoma. Clin Cancer Res 7:2372–2379, 2001 32. Luo L-Y, Bunting P, Scorilas A, Diamandis EP: Human kallikrein 10: A novel tumor marker for ovarian carcinoma? Clin Chim Acta 306:111–118, 2001[CrossRef][Medline]
33. Dong Y, Kaushal A, Bui L, et al: Human kallikrein 4 (KLK4) is highly expressed in serous ovarian carcinomas. Clin Cancer Res 7:2363–2371, 2001 34. Tanimoto H, Underwood LJ, Shigemasa K, et al: The stratum corneum chymotryptic enzyme that mediates shedding and desquamation of skin cells is highly overexpressed in ovarian tumor cells. Cancer 86:2074–2082, 1999[CrossRef][Medline]
35. Underwood LJ, Tanimoto H, Wang Y, et al: Cloning of tumor-associated differentially expressed gene-14, a novel serine protease overexpressed by ovarian carcinoma. Cancer Res 59:4435–4439, 1999 36. Yousef GM, Kyriakopoulou LG, Scorilas A, et al: Quantitative expression of the human kallikrein gene 9 (KLK9) in ovarian cancer: A new independent and favorable prognostic marker. Cancer Res 161:7811–7818, 2001 37. Diamandis EP, Yousef GM, Soosaipillai AR, et al: Immunofluorometric assay of human kallikrein 6 (zyme/protease M/neurosin) and preliminary clinical applications. Clin Biochem 33:369–375, 2000[CrossRef][Medline]
38. Scholler N, Fu N, Yang Y, et al: Soluble member(s) of the mesothelin/megakaryocyte potentiating family are detectable in sera from patients with ovarian carcinoma. Proc Natl Acad Sci U S A 96:11531–11536, 1999
39. Mills GB, Bast RC, Srivastava S: Future for ovarian cancer screening: Novel markers for emerging technologies of transcriptional profiling and proteomics. J Natl Cancer Inst 93:1437–1439, 2001 40. Parley PJ: Ovarian cancer screening: Are we making any progress? Curr Opin Oncol 13:399–402, 2001[CrossRef][Medline] 41. Hoffman BR, Katsaros D, Scorilas, et al: Immunofluorometric quantitation and histochemical localization of kallikrein 6 protein in ovarian cancer tissues: A new independent unfavorable prognostic biomarker. Br J Cancer 87:763–771, 2002[CrossRef][Medline] 42. Shigemasa K, Underwood LJ, Beard J, et al: Overexpression of testisin, a serine protease expressed by testicular germ cells, in epithelial ovarian tumor cells. J Soc Gynecol Investig 7:358–362, 2000[CrossRef][Medline]
43. Tanimoto H, Yan Y, Clarke J, et al: Hepsin, a cell surface serine protease identified in hepatoma cells, is overexpressed in ovarian cancer. Cancer Res 57:2884–2887, 1997 44. Hirahara F, Miyagi E, Nagashima Y, et al: Differential expression of trypsin in human ovarian carcinomas and low-malignant-potential tumors. Gynecol Oncol 68:162–165, 1998[CrossRef][Medline] 45. Duffy MJ: Role of proteolytic enzymes in cancer invasion and metastasis. Clin Exp Metastasis 10:145–155, 1992[CrossRef][Medline] 46. Matrisian LM: Cancer biology: Extracellular proteinases in malignancy. Curr Biol 9:R776–R778, 1999[CrossRef][Medline] 47. Kleiner DE, Stetler-Stevenson WG: Matrix metalloproteinases and metastasis. Cancer Chemother Pharmacol 43:S42–S51, 1999 48. Woodhouse EC, Chuaqui RF, Liotta LA: General mechanisms of metastasis. Cancer 80:1529–1537, 1997[CrossRef][Medline] 49. Aznavoorian S, Murphy AN, Stetler-Stevenson WG, et al: Molecular aspects of tumor cell invasion and metastasis. Cancer 71:1368–1383, 1993[CrossRef][Medline] Submitted February 5, 2002; accepted November 25, 2002.
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Copyright © 2003 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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ABSTRACT
INTRODUCTION
4.2 or 4.4 µg/L). The relationship of this dichotomous variable with other clinicopathologic correlates was established with the 
2 test or the Fisher’s exact test, as appropriate. 
