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China accounts for almost half of the total number of liver cancer cases and deaths worldwide, and hepatocellular carcinoma (HCC) is the most primary liver cancer. Snail family transcriptional repressor 2 (SNAI2) is known as an epithelial to mesenchymal transition-inducing transcription factor that drives neoplastic epithelial cells into mesenchymal phenotype. However, the roles of endogenous SNAI2 remain controversial in different types of malignant tumors. Herein, we surprisingly identify that anchorage-independent growth, including the formation of tumor sphere and soft agar colony, is significantly increased when SNAI2 expression is inhibited by shRNAs in HCC cells. Suppression of SNAI2 suffices to up-regulate several cancer stem genes. Although unrelated to the metastatic ability, SNAI2 inhibition does increase the efflux of Hoechst 33342 and enhance multidrug resistance in vitro and in vivo. In agreement with this data, we demonstrate for the first time that decreasing SNAI2 level can transcriptionally upregulate several ATP binding cassette (ABC) transporter genes such as ABCB1. Moreover, ABC transporters' inhibitor verapamil can rescue the multidrug resistance induced by SNAI2 inhibition. Our results implicate that SNAI2 behaves as a tumor suppressor by inhibiting multidrug resistance via suppressing ABC transporter genes in HCC cells.

Breast cancer is one of the most frequently diagnosed cancers among women, and metastasis makes it lethal. Tumor-associated macrophages (TAMs) that acquire an alternatively activated macrophage (M2) phenotype may promote metastasis. However, the underlying mechanisms are still elusive. Here, we examined how TAMs interact with breast cancer cells to promote metastasis. Immunohistochemistry was used to examine the expression of the M2-specific antigen CD163 in paraffin-embedded mammary carcinoma blocks to explore fusion events in breast cancer patients. U937 cells were used as a substitute for human monocytes, and these cells differentiated into M2 macrophages following phorbol 12-myristate 13-acetate (PMA) and M-CSF stimulation. M2 macrophages and the breast cancer cell lines MCF-7 and MDA-MB-231 fused in the presence of 50% polyethylene glycol. Hybrids were isolated by fluorescence-activated cell sorting, and the relevant cell biological properties were compared with their parental counterparts. Breast cancer stem cell (BCSC)-related markers were quantified by immunofluorescence staining, RT-PCR, quantitative RT-PCR and/or western blotting. The tumor-initiating and metastatic capacities of the hybrids and their parental counterparts were assessed in NOD/SCID mice. We found that the CD163 expression rate in breast cancer tissues varied significantly and correlated with estrogen receptor status (p0.05). Characterization of the fusion hybrids revealed a more aggressive phenotype, including increased migration, invasion and tumorigenicity, but reduced proliferative ability, compared with the parental lines. The hybrids also gained a CD44(+)CD24(-/low) phenotype and over-expressed epithelial-mesenchymal transition-associated genes. These results indicate that TAMs may promote breast cancer metastasis through cell fusion, and the hybrids may gain a BCSC phenotype.

Anthracycline daunorubicin (DNR) is one of the major antitumor agents widely used in the treatment of myeloid leukemia. Unfortunately, the clinical efficacy of DNR was limited because of its cytotoxity at high dosage. As a novel cytoprotective mechanism for tumor cell to survive under unfavorable conditions, autophagy has been proposed to play a role in drug resistance of tumor cells. Whether DNR can activate to impair the sensitivity of cancer cells remains unknown. Here, we first report that DNR can induce a high level of autophagy, which was associated with the activation of extracellular signal-regulated kinase 1/2 (ERK1/2). Moreover, cell death induced by DNR was greatly enhanced after autophagy inhibition by the pharmacological inhibitor chloroquine (CQ) and siRNAs targeting Atg5 and Atg7, the most important components for the formation of autophagosome. In conclusion, we found that DNR can induce cytoprotective autophagy by activation of ERK in myeloid leukemia cells. Autophagy inhibition thus represents a promising approach to improve the efficacy of DNR in the treatment of patients with myeloid leukemia.