Clinical and Functional Importance of Selected CASP8 and CASP9 Polymorphisms in Breast Carcinoma

Abstract

Caspase-8 and caspase-9 (encoded by CASP8 and CASP9) are executive caspases of programmed cell death (apoptosis). Dysregulation of apoptosis plays an important role in cancer development, progression, and resistance to anticancer therapy. The goal of this work was to evaluate potential associations between polymorphisms in CASP8 and CASP9, previously linked to breast cancer risk, and the transcript levels of these genes (including their alternative anti-apoptotic variants) in tumor tissues and the clinical characteristics of the patients. Sanger sequencing, high resolution melting (HRM) analysis, and allelic discrimination were used to identify polymorphisms in DNA samples isolated from tumor tissues and peripheral blood lymphocytes of 60 breast carcinoma patients. Total transcript levels of CASP8 and CASP9, and levels of alternative splicing variants CASP8L and CASP9B, were quantified by real-time PCR in tumor tissues. Clinically interesting associations were validated in DNA from lymphocytes of 615 breast carcinoma patients. A haplotype in CASP9 composed of three polymorphisms rs4645978-rs2020903-rs4646034 was significantly associated with CASP9 expression in tumors, with the expression of the progesterone receptor and ERBB2, and with the TNBC subtype of breast carcinoma in the validation study. The associations between the rs3834129 polymorphism in CASP8 and stage of disease, rs6435074 with grade, expression of estrogen receptor and ERBB2, and rs6723097 with ERBB2 expression have not yet been validated. However, rs6723097 was associated with disease-free survival in patients treated with hormonal therapy. This study reveals a previously unknown and presumably functional (in silico) association between a haplotype in CASP9 and molecular and clinical phenotypes of breast carcinoma. The potential clinical utility of this association for prognostication of breast carcinoma should be evaluated by independent studies.Key words: breast carcinoma - caspases - polymorphisms - functional - clinical - importanceThis work was supported by grant of the CU Grant Agency No. 1444313, and grant of the Internal Grant Agency of the Czech Ministry of Health No. 15-25618A.The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 3. 3. 2016Accepted: 26. 10. 2016.