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konferencjach naukowych: Praga 2019

HMGMT, BRCA1 AND MEG3 METHYLATION STATUS

IN TRIPLE-NEGATIVE BREAST CANCER

Sylwia Paszek¹, Agnieszka Kołacińska²-³, Marcin Braun⁴, Ewa Kaznowska¹, Dorota Jesionek-Kupnicka⁴, Edyta Barnaś¹, Izabela Zawlik¹"

^aculty of Medicine, University of Rzeszów, Rzeszów, Poland; Department of Head and Neck Cancer Surgery, Medical University of Lodź, Lodź, Poland; ³Breast Unit, Cancer Center, Copernicus Memoriał Hospital, Lodź Poland; Department of Pathology, Chair of Oncology, Medical University of Lodź, Lodź, Poland

"Corresponding author: Associate Professor Izabela Zawlik, Faculty of Medicine, University of Rzeszów, Warzywna 1A, 35-959 Rzeszów, Poland, e-mail: [e-mail]

BACKGROUND AND AIM: Breast cancer is one of the most common cancer in women worldwide. The most severe type of breast cancer is triple-negative breast cancer (TNBC) due to unfavorable clinical course and poor prognosis (1). The development of cancer is often associated with dysregulation of epigenetic mechanisms, including DNA methylation (2). Recent studies have shown that IncRNA (long non-coding RNA) may also affect cancerogenesis (3). One of the genes encoding IncRNA whose changes are responsible for breast cancer development is MEG3 (4). The aim of our study was to evaluate MGMT (06-methylguanine DNA methyltransferase), BRCA1 (breast cancer 1) and MEG3 fmaternally expressed 3) methylation status in TNBC.

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Figurę 1. Representative MSP results for the MGMT, BRCA1 and MEG3 promoter methylation. A. Presence of 80-bp PCR product indicates that the breast cancer is positive for MGMT methylation. Presence of 94-bp PCR product indicates that the breast cancer is negative for MGMT methylation. B. The product sizes of the methylated and unmethylated amplicons were 68 bp and 104 bp, respectively. C. The product sizes of the methylated and unmethylated amplicons were 227 bp. Abbreviations: M, methylated PCR product; U, unmethylated PCR product; PC, positive control - methylated control; NC, negative control -unmethylated control; MW, molecular weight marker.

EXPERIMENTAL PROCEDURĘ: In this study 44 TNBC patients were included. Genomie DNA was isolated from formalin-fixed and paraffin-embedded tissues using the QIAamp DNA FFPE Tissue Kit. The methylation status of the MGMT, BRCA1 and MEG3 promoter regions were analysed by methylation-specific PCR (MSP). We assessed the correlations between the methylation status and clinicopathological features (age, grade, tumor size, lymph nodes metastasis).

RESULTS: MGMT, BRCA1 and MEG3 promoters methylation was found in 70.4%, 61.3% and 61.3% of TNBC patients, respectively. Representative results of MSP for the promoter methylation analyzed genes are shown in Figurę 1. Moreover, we have shown that the frequency of MGMT and BRCA1 methylation is higher in older patients compared to younger patients (Table 1). Additionally, in one of TNBC patient with glandular and squamous histopathological components, it was shown that the promoters status of all analysed genes, changed from methylated to unmethylated after chemotherapy of this patient.

Table 1. Association of DNA methylation with age

Gene name	Mean Age		p - value
	Unmethylated	Methylated
MGMT	53.92889	63.54091	0.019438
BRCA1	55.00731	64.16015	0.018845

CONCLUSION: The high frequency of MGMT, BRCA1 and MEG3 methylation indicates that epigenetic changes are important mechanisms in breast cancer. Moreover, our results indicates that MGMT and BRCA1 methylation may have greater impact in the development of breast cancer in older patients compared to younger patients. However, the results should be confirmed in a larger number of patients.

References:

1) Siegel R, Ma J, Zou Z, Jemal A: CA: a cancer journal for dinicians 2014, Cancer Stotistics. 2014; 64:9-29. 2) Baylin SB, Jones PA. Epigenetic Determinants of Cancer. Cold Spring Harb Perspect Biol. 2016; 8(9): a019505. 3) Zhou S, He Y, Yang S, et al. The regulatory roles of IncRNAs in the process of breast cancer invasion and metastasis. Biosci Rep. 2018;38(5):BSR20180772. 4) Sun LI, Li Y2, Yang B. Downregulated long non-coding RNA MEG3 in breast cancer regulates proliferation, migration and invasion by depending on p53's transcriptional activity. Biochem Biophys Res Commun. 2016;9;478(l):323-329.

FUNDING SOURCE: This study was supported    3^rd World Congress on Cancer, Prague, 2019

by the University of Rzeszów.