Abstract P3-07-08: Breast cancer in China reveals transcriptomic likeness to Caucasian breast cancer

The incidence of breast cancer among Chinese women has been historically much lower than that of Caucasian women but has increased dramatically over the past 30 years in urban areas of China, an increase likely to continue in the next decades across China with progressive urbanization and economic development. However, it is still unclear whether differences in breast cancer incidence between Chinese and Caucasian women reflect differences in disease biology in addition to environmental factors. To address this question, we compared consecutive cohorts of Chinese and Italian breast cancer patients who underwent surgical resection in the years 2005-2007 at Fudan Cancer Center of Shanghai (China) and Fondazione IRCCS Istituto Tumori of Milan (Italy), respectively, two comprehensive cancer centers with similar inpatients and outpatients recruited in a large area. Analyses of clinico-pathological characteristics of 1563 Chinese and 1052 Italian consecutive breast cancer patients revealed that 50% of patients in the Chinese cohort were younger than 50 years versus 29% of Italian patients, indicating that Chinese women develop breast cancer earlier than Italian patients, with a peak of frequency at 50-60 years. Among Chinese breast tumors, 63% were estrogen receptor (ER)-positive versus 85% of the Italians, and the prevalence of ER-positive tumors was equivalent in pre- and postmenopausal Chinese cases, suggesting the same hormonal features in tumors of younger and older patients, consistent with findings in the Italian cohort. Microarray-based gene and miRNA expression profiling was then conducted on 80 Chinese and 97 Italian samples using Illumina Gene and MicroRNA expression technologies. To minimize potential bias and artifact due to variability in specimen collection, storage, processing and analysis of high-throughput results, samples initially collected in the Chinese and Italian hospitals were all stored, randomly processed and analyzed in the Italian center. Analysis revealed a comparable pattern of gene and miRNA expression in the 2 cohorts with unsupervised hierarchical clustering of 12,338 genes and 858 miRNAs, and similar expression of intrinsic and extracellular matrix (ECM) genes led to a similar partition in intrinsic and ECM subtypes, indicating molecular similarity among Chinese and Caucasian breast cancers. Supported by Ministero Affari Esteri (Italy-China significant bilateral project). Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-07-08.