Abstract PO4-15-02: ApoE polymorphism is associated with aggressive tumor phenotypes for breast cancer patients
Authors: Luciano Maria Claudia , Ana Rosane Sant' , Lima Valeska , Silva Paulo Goberlanio , Albuquerquye Clarissa , Bitencourt Flavio , Bezerra Maria Julia , Oliveira Francisca Fernanda , De Moura José Fernando , Fernandes Isabelle Joyce , Leite Fernanda 
Published: May 2024

Abstract
Introduction: Apolipoprotein E (APOE) is implicated in several biological processes, such as protein synthesis, cell growth and differentiation, cholesterol transport, lipid metabolism, and tissue repair. APOE has different isoforms (E2, E3, and E4) that combine conflicting relations with cancer risk. This study aimed to evaluate the distribution of different isoforms of APOE among suspected HBOC (Hereditary Breast and Ovarian Cancer Syndrome) patients. Methodology: DNA was extracted from the blood cells of 108 patients. The detection was performed using qPCR after amplifying specific regions containing the polymorphisms. It was considered that all the amplicons containing Cq amplification &lt; 35. The melting curve for each patient was analyzed to determine the frequency of the isoforms E2, E3, E4, and genotypes E2/E2, E2/E3, E2E4, E3/E3, and E3/E4. The allele and genotype were also correlated with hereditary variants previously identified by genetic tests for germline mutations and with tumoral phenotype. The data were expressed in frequency and associated using chi-square tests or Fisher's exact test (SPSS v20.0, p&lt; 0.05). Results A total of 108 patients filling criteria for HBOC syndrome were evaluated. Among them, 15 (13.9%) had a mutation in BRCA1, 5 (4.6%) in BRCA2, and 2 (1.9%) in TP53. Most patients were under 45 years old (n=76, 70.4%), female (n=104, 96.3%), had a high school education (n=44, 44.0%), were non-smokers (n=79, 80.6%) or drinkers (n=76, 78.4%), and had no comorbidities (n=66, 64.1%). Overweight at diagnosis was observed in 61 (68.5%) individuals. The most frequent tumor phenotype and stage were luminal B (n=46, 43.4%) and stage IIIA (n=22, 26.2%), respectively. Neoadjuvant chemotherapy was performed in 40 (47.1%) with a high rate of complete and partial response 18 (36.7%) and 22 (44.9%), respectively. Regarding ApoE polymorphisms, the E2 allele showed the lowest frequency (n=7, 6.5%), E3 was present in 103 (95.4%) cases, while E4 was present in 39 (36.1%). The most frequent genotype was E3/E3 (n=64, 58.3%), followed by E3/E4 (n=34, 31.5%), E2/E3 (n=6, 5.6%), E4 (n=4, 3.7%), and E2/E4 (n=1, 0.9%). No cases of E2/E2 genotype were observed. The presence of E2 was inversely associated with comorbidity frequency (p=0.040) but directly associated with TP53 mutation (p=0.012) and triple-negative tumor phenotype (p=0.027). E3 was not associated with clinical characteristics, but E4 was associated with low Ki-67 immunoreactivity (p=0.033). The E2/E3 phenotype was directly associated with triple-negative tumors (p=0.044) and heterozygous tumors (p=0.011). Conclusion: The ApoE polymorphism, particularly the presence of the E2 allele in heterozygosity, is associated with TP53 mutation and a more aggressive tumor phenotype.
Citation Format: Maria Claudia Luciano, Rosane Sant' Ana, Valeska Lima, Paulo Goberlanio Silva, Clarissa Albuquerquye, Flavio Bitencourt, Maria Julia Bezerra, Francisca Fernanda Oliveira, José Fernando De Moura, Isabelle Joyce Fernandes, Fernanda Leite. ApoE polymorphism is associated with aggressive tumor phenotypes for breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-15-02.