_____________________________________________________________________________________________________ *Corresponding author: Email: asmaa.osama@must.edu.eg; Original Research Article Journal of Disease and Global Health 11(3): 124-133, 2018 ISSN: 2454-1842, NLM ID: 101664146 ROLE OF CYSTATIN C GENE POLYMORPHISM AS A RISK FACTOR OF PROSTATE CANCER A CASE-CONTROL STUDY ELSAEID ELBAWAB 1 , M. BAKHEET 1 , M. SEDDIK 2 , A. REDA 3 AND A. OSMAN 4* 1 Department of Biochemistry, Faculty of Medicine, Al Azhar University, Egypt. 2 Department of Clinical Pathology, Faculty of Medicine, Assiut University, Egypt. 3 Urology and Nephrology University Center, Assiut University, Egypt. 4 Department of Clinical Pathology, Faculty of Medicine, Aswan University, Egypt. AUTHORS’ CONTRIBUTIONS All authors have made substantial contributions to conception and design, and/or acquisition of data, and/or analysis and interpretation of data. All authors participated in drafting the article or revising it critically for important intellectual content and all authors gave final approval of the version to be submitted, and any revised version. Each author participated sufficiently in the work to take public responsibility for appropriate portions of the content. All authors read and approved the final manuscript. ARTICLE INFORMATION Reviewers: (1) Innocent Damudu Peter, University of Maiduguri, Nigeria. (2) P. Fernandez, Stellenbosch University, South Africa. (3) Ugwu Melvin Nnaemeka, Cross River University of Technology, Nigeria. (4) Alok Nahata, Ying Zhi Agricultural and Industries, Malaysia. Received: 12 September 2018 Accepted: 02 November 2018 Published: 07 December 2018 __________________________________________________________________________________ ABSTRACT Background: Cystatin C is found to be down regulated in prostate cancer and modifies invasion of prostate cancer cells via MAPK/Erk and androgen receptor pathways. In this work, we detected the frequency of cystatin C gene single nucleotide polymorphism different variants and its relation to the serum levels of both total testosterone and PSA. Methods: The study was conducted on (50) cases of newly diagnosed Prostatic cancer patients and another age and sex-comparable (50) healthy individuals as a control group. All were investigated for the frequency of Cystatin C gene polymorphism, serum total testosterone and serum PSA. Results: Cystatin C gene (BB) variant was detected in 16.0% of cases and 4.0% in controls which showed significant difference with p value=0.046 as compared with (AA) and (AB) variants where (AA) variant was detected in 56.0% of cases and 64.0% in controls which showed no significant difference with p value =0.414, and (AB) variant was detected in 28.0% of cases and 32.0% in controls which also showed no significant difference with p value = 0.663. The serum PSA levels in cases were from 30 to 150 (ng/ml) and in controls were from 0.0 to 3.4 (ng/ml) which showed high significant difference between both groups with p value = 0.000. Serum PSA Levels was higher in the mutant type (BB) than the wild type (AA). As in wild type (AA) the serum PSA levels ranged from 31.5 to 150 (ng/ml) and mutant type (BB) the serum PSA levels ranged from 65