Cholangiocarcinoma is an aggressive malignant tumor originating from intrahepatic or extrahepatic bile ducts. Its malignant phenotypes may be assumed by cancer stem cells (CSC). Here, we demonstrate that CD274 (PD-L1), known as an immunomodulatory ligand, has suppressive effects on CSC-related phenotypes of cholangiocarcinoma. Using two human cholangiocarcinoma cell lines, RBE and HuCCT1, we attempted to isolate the CD274low and CD274high cells from each cell line, and xenografted them into immunodeficient NOD/scid/γcnull (NOG) mice. We found that the CD274low cells isolated from both RBE and HuCCT1 are highly tumorigenic in NOG mice compared with CD274high cells. Furthermore, the CD274low cells possess several CSC-related characteristics, such as high aldehyde dehydrogenase (ALDH) activity, reduced reactive oxygen species production and a dormant state in the cell cycle. Furthermore, depletion of CD274 expression by shRNA in RBE cells enhances their tumorigenicity and increases ALDH activity. These findings are compatible with our observation that clinical cholangiocarcinoma specimens are classified into low and high groups for CD274 expression, and the CD274 low group shows poorer prognosis when compared with the CD274 high group. These results strongly suggest that CD274 has a novel function in the negative regulation of CSC-related phenotypes in human cholangiocarcinoma, which is distinct from its immunomodulatory actions.

Abstract. Accumulating evidence demonstrated that Hox antisense intergenic RNA (HOTAIR) serves essential roles in the development and metastasis of several types of cancer. In hepatocellular carcinoma (HCC), high expression of HOTAIR is associated with poor prognosis, and HOTAIR regulates cell migration and proliferation. However, the downstream molecular targets of HOTAIR depend on the cancer cell types, and little is known about the precise molecular mechanisms of HOTAIR involved in cancer development. The present study investigated the role of HOTAIR in HCC cell lines. Notably, the overexpression of HOTAIR in HCC cell lines did not affect cell migration and proliferation capability. In the microarray analysis, C-C motif chemokine ligand (CCL)2 was identified to be differentially expressed in HOTAIR-overexpressing cells, and it was confirmed that HOTAIR promotes the secretion of CCL2. Furthermore, it was revealed that the proportion of macrophages and myeloid-derived suppressor cells (MDSCs) were increased when peripheral blood mononuclear cells were co-cultured with HOTAIR-overexpressing cells. Collectively, these data suggest that HOTAIR regulates CCL2 expression, which may be involved in the recruitment of macrophages and MDSCs to the tumor microenvironment. IntroductionHox antisense intergenic RNA (HOTAIR), a lncRNA that acts as an oncogenic molecule in various types of cancer, is localized to the HOXC gene cluster. HOTAIR interacts with PRC2 (polycomb repressive complex 2) to enhance H3K27 trimethylation, and thereby decreases the expression of a large number of genes. Several groups, including our laboratory, have reported that high HOTAIR expression is correlated with a poor prognosis in several types of cancer, including breast (1), colorectal (2), non-small lung cell (3), and gastric cancer (4). Interestingly, recent report suggested that effects of HOTAIR are strongly tissue-dependent and can even differ within the same type of cancer (5). Thus, the underlying mechanism by which HOTAIR is involved in malignant progression remains uncertain.Hepatocellular carcinoma (HCC) is the fifth leading cause of cancer and second leading cause of cancer-related mortality worldwide. More than 600,000 deaths are associated with HCC every year worldwide (6). Previous report suggested that the expression of HOTAIR is associated with tumor recurrence and poor prognosis in hepatocellular carcinoma (7,8). Several in vitro analyses were reported using HCC cell line, HepG2; HOTAIR is a FOXC1-activated driver of malignancy, which acts in part through the repression of miR-1 in HepG2 cells (9). HOTAIR silence activates P16 Ink4a and P14 ARF signaling by enhancing miR-218 expression and suppressing Bmi-1 expression, resulting in the suppression of tumorigenesis in HepG2 cells (10). Introduction of human HOTAIR into HepG2 cells revealed that HOTAIR promoted more rapid proliferation (7). Although different intracellular signaling are expected among multiple HCC cell lines, the research of HOTAIR using HCC cell lines except for...

CD271 (p75 neurotrophin receptor) plays both positive and negative roles in cancer development, depending on the cell type. We previously reported that CD271 is a marker for tumor initiation and is correlated with a poor prognosis in human hypopharyngeal cancer (HPC). To clarify the role of CD271 in HPC, we established HPC cell lines and knocked down the CD271 expression using siRNA. We found that CD271-knockdown completely suppressed the cells’ tumor-forming capability both in vivo and in vitro. CD271-knockdown also induced cell-cycle arrest in G0 and suppressed ERK phosphorylation. While treatment with an ERK inhibitor only partially inhibited cell growth, CDKN1C, which is required for maintenance of quiescence, was strongly upregulated in CD271-depleted HPC cells, and the double knockdown of CD271 and CDKN1C partially rescued the cells from G0 arrest. In addition, either CD271 depletion or the inhibition of CD271-RhoA signaling by TAT-Pep5 diminished the in vitro migration capability of the HPC cells. Collectively, CD271 initiates tumor formation by increasing the cell proliferation capacity through CDKN1C suppression and ERK-signaling activation, and by accelerating the migration signaling pathway in HPC.