JBUON 2021; 26(2): 475-482 ISSN: 1107-0625, online ISSN: 2241-6293 • www.jbuon.com Email: editorial_ofce@jbuon.com ORIGINAL ARTICLE Corresponding author: Vladimir Jurisic, MD, PhD. Univeristy of Kragujevac, Faculty of Medical Sciences, Svetozara Markovića 69, 34 000 Kragujevac, Serbia. Tel: +381 34306800, Email: jurisicvladimir@gmail.com Received: 18/01/2021; Accepted: 03/02/2021 Evaluation of Cyclin D1 expression by western blotting methods and immunohistochemistry in breast cancer patients Sandra Radenkovic 1 , Gordana Konjevic 2 , Marina Nikitovic 1,3 , Suzana Stojanovic-Rundic 1,3 , Vesna Plesinac-Karapandzic 1,3 , Marijana Milovic-Kovacevic 4 , Vladimir Jurisic 5 1 Department for Radiation Oncology and Diagnostics, Institute of Oncology and Radiology of Serbia, 11 000 Belgrade, Pasterova 14, Serbia. 2 Department of Experimental Oncology, Institute of Oncology and Radiology of Serbia, Belgrade, Serbia. 3 Faculty of Medicine, University of Belgrade, Belgrade, Serbia. 4 Institute of Oncology and Radiology of Serbia, 11 000 Belgrade, Pasterova 14, Serbia. 5 Department of Pathophysiology, Faculty of Medical Sciences, University of Kragujevac, Serbia. Summary Purpose: Considering that cyclin D1 had a prognostic and clinical value for breast cancer patients, adequate measure- ment of cyclin D1 is necessary. Methods: In this investigation, we detect cyclin D1 expres- sion in tumour and peritumoral tissue of breast cancer patients by Western blotting method and by immunohis- tochemistry. Results: Cyclin D1 expression decreased signifcantly with each advanced clinical stage of disease and tumour size. Also, patients without lymph node involvement, with posi- tive hormone receptors and Luminal A type of tumours had signifcantly increased the expression of cyclin D1. We show that cyclin D1 expression correlates with longer RFS in the entire group of patients, in the group of ER-positive and in the group of HER2-negative patients. Patients who were both ER and cyclin D1 positive had a better prognosis. Conclusion: Taken together, our results showing correla- tion of cyclin D1 with clinical stage, tumour size and lymph nodes, suggest that cyclin D1 expression detected by Western blotting could be considered as an additional marker for the staging of breast cancer, as well as a marker for longer RFS and survival in ER-positive breast cancer patients. Key words: cyclin D1, breast cancer patients, estrogen recep- tor, progression-free survival, overall survival Introduction Novel tumour markers which could predict and detect possible relapse of breast cancer disease are required in the treatment of this disease. Moreover, predictive markers are necessary for the selection of patients who should receive a certain type of treatment [1]. Considering that current adjuvant systemic therapies are not specifc for all types of breast cancer, more specifc molecular markers for the therapy and follow-up of breast cancer patients are needed [2,3]. The cyclins represent a class of proteins that are associated with the cell cycle. Cyclin D1 is a protein involved in the G1 phase of the cell cycle by helping the phosphorylation of retinoblastoma protein (pRb) [4]. The hypophosphorylated form of pRb blocks the growth of the cell. Therefore, phosphorylation of pRb is crucial for the cell cy- cle transtition into the S-phase [5]. Estrogens can induce proliferation by activating cyclin D1 that phosphorylates Rb [6]. Moreover, it has been shown This work by JBUON is licensed under a Creative Commons Attribution 4.0 International License.