Buck Institute for Research on Aging, 8001 Redwood Blvd., Novato, CA, 94945, USA.
University of California, Genomics Institute, Santa Cruz, CA, USA.
Breast Cancer Res. 2020 Jul 31;22(1):81. doi: 10.1186/s13058-020-01322-6.
Previous studies have identified and validated a risk-associated Active transcriptome phenotype commonly expressed in the cancer-adjacent and histologically normal epithelium, stroma, and adipose containing peritumor microenvironment of clinically established invasive breast cancers, conferring a 2.5- to 3-fold later risk of dying from recurrent breast cancer. Expression of this Active transcriptome phenotype has not yet been evaluated in normal breast tissue samples unassociated with any benign or malignant lesions; however, it has been associated with increased peritumor adipocyte composition.
Detailed histologic and transcriptomic (RNAseq) analyses were performed on normal breast biopsy samples from 151 healthy, parous, non-obese (mean BMI = 29.60 ± 7.92) women, ages 27-66 who donated core breast biopsy samples to the Komen Tissue Bank, and whose average breast cancer risk estimate (Gail score) at the time of biopsy (1.27 ± 1.34) would not qualify them for endocrine prevention therapy.
Full genome RNA sequencing (RNAseq) identified 52% (78/151) of these normal breast samples as expressing the Active breast phenotype. While Active signature genes were found to be most variably expressed in mammary adipocytes, donors with the Active phenotype had no difference in BMI but significantly higher Gail scores (1.46 vs. 1.18; p = 0.007). Active breast samples possessed 1.6-fold more (~ 80%) adipocyte nuclei, larger cross-sectional adipocyte areas (p < 0.01), and 0.5-fold fewer stromal and epithelial cell nuclei (p < 1e-6). Infrequent low-level expression of cancer gene hotspot mutations was detected but not enriched in the Active breast samples. Active samples were enriched in gene sets associated with adipogenesis and fat metabolism (FDR q ≤ 10%), higher signature scores for cAMP-dependent lipolysis known to drive breast cancer progression, white adipose tissue browning (Wilcoxon p < 0.01), and genes associated with adipocyte activation (leptin, adiponectin) and remodeling (CAV1, BNIP3), adipokine growth factors (IGF-1, FGF2), and pro-inflammatory fat signaling (IKBKG, CCL13).
The risk-associated Active transcriptome phenotype first identified in cancer-adjacent breast tissues also occurs commonly in healthy women without breast disease who do not qualify for breast cancer chemoprevention, and independently of breast expressed cancer-associated mutations. The risk-associated Active phenotype appears driven by a pro-tumorigenic adipocyte microenvironment that can predate breast cancer development.
先前的研究已经确定并验证了一种与风险相关的活跃转录组表型，该表型通常在临床上已确立的浸润性乳腺癌的癌旁和组织学正常上皮、基质和含有肿瘤周围微环境的脂肪中表达，使死于复发性乳腺癌的风险增加 2.5-3 倍。然而，尚未在与任何良性或恶性病变无关的正常乳腺组织样本中评估这种活跃转录组表型的表达；但是，它与肿瘤周围脂肪细胞组成的增加有关。
对 151 名健康、多产、非肥胖（平均 BMI=29.60±7.92）的绝经前妇女的正常乳腺活检样本进行了详细的组织学和转录组（RNAseq）分析，这些妇女年龄在 27-66 岁之间，她们向 Komen 组织库捐献了核心乳腺活检样本，并且她们在活检时的平均乳腺癌风险估计值（Gail 评分）（1.27±1.34）不符合内分泌预防治疗的条件。
全基因组 RNA 测序（RNAseq）鉴定出这些正常乳腺样本中有 52%（78/151）表达活跃的乳腺表型。虽然在乳腺脂肪细胞中发现了活跃的特征基因表达最具可变性，但具有活跃表型的供体在 BMI 上没有差异，但 Gail 评分明显更高（1.46 对 1.18；p=0.007）。活跃的乳腺样本具有 1.6 倍（约 80%）的脂肪细胞核，更大的脂肪细胞横截面积（p<0.01），以及 0.5 倍（p<1e-6）的基质和上皮细胞核。检测到但未富集癌症基因热点突变的低频低水平表达，但在活跃的乳腺样本中没有富集。活跃样本富集了与脂肪生成和脂肪代谢相关的基因集（FDR q≤10%），已知可驱动乳腺癌进展的 cAMP 依赖性脂肪分解的高特征评分，白色脂肪组织褐变（Wilcoxon p<0.01），以及与脂肪细胞激活（瘦素、脂联素）和重塑（CAV1、BNIP3）、脂肪细胞因子生长因子（IGF-1、FGF2）和促炎脂肪信号（IKBKG、CCL13）相关的基因。
首次在癌旁乳腺组织中发现的与风险相关的活跃转录组表型也常见于没有乳腺疾病且不符合乳腺癌化学预防条件的健康女性中，并且与乳腺表达的癌症相关突变无关。与风险相关的活跃表型似乎是由促进肿瘤发生的脂肪细胞微环境驱动的，这种微环境可能早于乳腺癌的发生。
