Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, 68198-6495, USA.
Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE, 68198-6495, USA.
Clin Exp Metastasis. 2018 Dec;35(8):797-818. doi: 10.1007/s10585-018-9941-7. Epub 2018 Oct 16.
Epidemiological studies show a reduced risk of breast cancer (BC) in women consuming high levels of long-chain (LC) omega-3 (ω-3) fatty acids (FAs) compared with women who consumed low levels. However, the regulatory and mechanistic roles of dietary ω-6 and LC-ω-3 FAs on tumor progression, metastasis and survival are poorly understood. Female BALB/c mice (10-week old) were pair-fed with a diet containing ω-3 or an isocaloric, isolipidic ω-6 diet for 16 weeks prior to the orthotopic implantation of 4T1 mammary tumor cells. Major outcomes studied included: mammary tumor growth, survival analysis, and metastases analyses in multiple organs including pulmonary, hepatic, bone, cardiac, renal, ovarian, and contralateral MG (CMG). The dietary regulation of the tumor microenvironment was evaluated in mice autopsied on day-35 post tumor injection. In mice fed the ω-3 containing diet, there was a significant delay in tumor initiation and prolonged survival relative to the ω-6 diet-fed group. The tumor size on day 35 post tumor injection in the ω-3 group was 50% smaller and the frequencies of pulmonary and bone metastases were significantly lower relative to the ω-6 group. Similarly, the incidence/frequencies and/or size of cardiac, renal, ovarian metastases were significantly lower in mice fed the ω-3 diet. The analyses of the tumor microenvironment showed that tumors in the ω-3 group had significantly lower numbers of proliferating tumor cells (Ki67)/high power field (HPF), and higher numbers of apoptotic tumor cells (TUNEL)/HPF, lower neo-vascularization (CD31 vessels/HPF), infiltration by neutrophil elastase cells, and macrophages (F4/80) relative to the tumors from the ω-6 group. Further, in tumors from the ω-3 diet-fed mice, T-cell infiltration was 102% higher resulting in a neutrophil to T-lymphocyte ratio (NLR) that was 76% lower (p < 0.05). Direct correlations were observed between NLR with tumor size and T-cell infiltration with the number of apoptotic tumor cells. qRT-PCR analysis revealed that tumor IL10 mRNA levels were significantly higher (six-fold) in the tumors from mice fed the ω-3 diet and inversely correlated with the tumor size. Our data suggest that dietary LC-ω-3FAs modulates the mammary tumor microenvironment slowing tumor growth, and reducing metastases to both common and less preferential organs resulting in prolonged survival. The surrogate analyses undertaken support a mechanism of action by dietary LC-ω-3FAs that includes, but is not limited to decreased infiltration by myeloid cells (neutrophils and macrophages), an increase in CD3 lymphocyte infiltration and IL10 associated anti-inflammatory activity.
流行病学研究表明，与低水平摄入长链（LC）ω-3（ω-3）脂肪酸的女性相比，高水平摄入 LCω-3 脂肪酸的女性患乳腺癌（BC）的风险降低。然而，饮食 ω-6 和 LC-ω-3 脂肪酸对肿瘤进展、转移和存活的调节和机制作用知之甚少。10 周龄雌性 BALB/c 小鼠在接受 4T1 乳腺肿瘤细胞原位植入前，分别用含 ω-3 或等热量、等脂的 ω-6 饮食喂养 16 周。主要研究结果包括：乳腺肿瘤生长、生存分析以及包括肺、肝、骨、心、肾、卵巢和对侧 MG（CMG）在内的多个器官的转移分析。在肿瘤注射后第 35 天对小鼠进行尸检，评估肿瘤微环境的饮食调节情况。在摄入含 ω-3 饮食的小鼠中，肿瘤起始明显延迟，与 ω-6 饮食喂养组相比，生存时间延长。在 ω-3 组，肿瘤注射后第 35 天的肿瘤大小缩小了 50%，肺和骨转移的频率明显降低。同样，在摄入 ω-3 饮食的小鼠中，心脏、肾脏、卵巢转移的发生率/频率和/或大小明显降低。对肿瘤微环境的分析表明，与 ω-6 组相比，ω-3 组肿瘤中增殖的肿瘤细胞（Ki67）/高倍镜视野（HPF）数量明显减少，凋亡的肿瘤细胞（TUNEL）/HPF 数量增加，新生血管化（CD31 血管/HPF）减少，中性粒细胞弹性蛋白酶细胞和巨噬细胞（F4/80）浸润减少。此外，在摄入 ω-3 饮食的小鼠的肿瘤中，T 细胞浸润增加了 102%，导致中性粒细胞与淋巴细胞比值（NLR）降低了 76%（p<0.05）。NLR 与肿瘤大小之间以及 T 细胞浸润与凋亡肿瘤细胞数量之间存在直接相关性。qRT-PCR 分析显示，摄入 ω-3 饮食的小鼠肿瘤中 IL10 mRNA 水平显著升高（六倍），与肿瘤大小呈负相关。我们的数据表明，饮食 LC-ω-3 脂肪酸可调节乳腺肿瘤微环境，减缓肿瘤生长，减少向常见和不太偏好的器官转移，从而延长生存时间。进行的替代分析支持饮食 LC-ω-3 脂肪酸的作用机制，包括但不限于骨髓细胞（中性粒细胞和巨噬细胞）浸润减少、CD3 淋巴细胞浸润增加和与 IL10 相关的抗炎活性增加。
