Hypoxia pathway and hypoxia-mediated extensive extramedullary hematopoiesis are involved in ursolic acid's anti-metastatic effect in 4T1 tumor bearing mice.

Jian-Li Gao,Yan-Mei Shui,Bai-Cheng He,Gui-Yuan Lv,Tong-Chuan He,Wei Jiang,En-Yi Huang,Qi-Yang Shou,Xin Ji

doi:10.18632/oncotarget.12375

Abstract

Hypoxic in the tumor mass is leading to the myeloproliferative-like disease (leukemoid reaction) and anemia of body, which characterized by strong extensive extramedullary hematopoiesis (EMH) in spleen. As the key transcription factor of hypoxia, hypoxia-inducible factor-1 (HIF-1) activates the expression of genes essential for EMH processes including enhanced blood cell production and angiogenesis. We found ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid, inhibited growth of breast cancer both in vivo and in vitro. The suppression was mediated through the inhibition of multiple cell pathways linked to inflammation, proliferation, angiogenesis, and metastasis. UA also suppressed the leukemoid reaction and the EMH phenomenon of the tumor bearing mice without any significant suppression on body weight (i.p. by 20 mg/kg for 28 days). This is associated with the significant decrease in white blood cells (WBC), platelets (PLT) and spleen weight. During this process, we also detected the down-regulation of cell proliferative genes (PCNA, and β-catenin), and metastatic genes (VEGF, and HIF-1α), as well as the depression of nuclear protein intensity of HIF-1α. Furthermore, the expression of E2F1, p53 and MDM2 genes were increased in UA group when the VEGF and HIF-1α was over-expressed. Cancer cells were sensitive to UA treating after the silencing of HIF-1α and the response of Hypoxic pathway reporter to UA was suppressed when HIF-1α was over expressed. Overall, our results from experimental and predictive studies suggest that the anticancer activity of UA may be at least in part caused by suppressing the cancer hypoxia and hypoxia-mediated EMH.

Highlights

Breast cancer is the most common solid malignancy among women, both in the United States [1] and in China [2]
Some previous studies have shown that ursolic acid (UA) can inhibit several cancer cells through multiple pathways[30, 31], namely nuclear factor-κ-gene binding (NF-κB) [32], apoptosis signal- regulating kinase1 (ASK1)-c-Jun N-terminal kinase (JNK) [33], signal transducer and activator of 3 (STAT3) [34], JNK [35] and transforming growth factor-β1 (TGF-β1)/miR-21/programmed cell death 4 (PDCD4) Pathways [36], and so on
Our reporter assay exposed that several pathways, including hypoxia-inducible factor (HIF)-1α, extracellular signalregulated kinase (ERK), transcription factor (TCF), nuclear factor κB (NFκB), and eag-like K+ channel (Elk), were changed by UA treatment, among which HIF-1α was the most significant reduced

Summary

Introduction

Breast cancer is the most common solid malignancy among women (almost 26.8%–29% in all cancer cases), both in the United States [1] and in China [2]. In 2013, 85% breast cancer cases were invasion cases in younger women under age 40 years [3]. The close link between hypoxia and metastasis has been well recognized. Hypoxia affects both metastatic spread and selection of aggressive cells both in experimental and clinical studies [4]. Tumor hypoxia is associated with many steps in cancer, such as angiogenesis, metastasis, and dysregulated hematopoiesis [5,6,7]. Hypoxiaresponsive pathways modulate extensive extramedullary hematopoiesis (EMH) and angiogenesis [8, 9]

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