Loss of angiotensin-converting enzyme 2 promotes growth of gallbladder cancer.

The aim of this study is to investigate the role of angiotensin-converting enzyme 2 (ACE2) in gallbladder cancer (GBC) and the therapeutic potential of angiotensin receptor blocker in GBC. Human gallbladder epithelial cells (HGBEC) together with GBC cells and tissue samples were used. In vitro studies were carried out to investigate the role of ACE2 in GBC cells. ACE2 levels were studied in in vivo GBC mouse models subject to ARB treatment. ACE2 level was decreased in GBC cells compared with that in normal gallbladder cells. Replenishment of angiotensin II (A2) promoted tumour cell growth, which could be mitigated by ACE2 supplement. ARB blocked A2-induced GBC cell growth and activated ERK. Activity of mTOR was not altered with different ACE2 status. ARB inhibited tumour growth in xenograft mouse models. In vivo study also showed that decreased expression of ACE2 was associated with enlarged tumour size. By genetic replenishment of ACE2 and pharmaceutical use of ARB, restored ACE2 level mitigated GBC growth. Our results supported the rationale for the use of ARB in GBC patients for potential therapeutic benefit.

MicroRNA-135a acts as a putative tumor suppressor by directly targeting very low density lipoprotein receptor in human gallbladder cancer.

The precise functions and mechanisms of microRNAs (miR) in gallbladder cancer (GBC) remain elusive. In this study, we found that miR-135a-5p expression is often dampened and correlated with neoplasm histologic grade in GBC. MicroRNA-135a-5p introduction clearly inhibited GBC cell proliferation in vitro and in vivo. Moreover, very low density lipoprotein receptor (VLDLR), which is often upregulated in GBC tissues, was identified as a direct functional target of miR-135a-5p. Furthermore, the p38 MAPK pathway was proven to be involved in miR-135a-VLDLR downstream signaling. Together, these results suggested that the miR-135a-VLDLR-p38 axis may contribute to GBC cell proliferation.

Inhibition of mTOR pathway attenuates migration and invasion of gallbladder cancer via EMT inhibition.

Gallbladder cancer (GBC) is an aggressive disease in which epithelial-mesenchymal transition (EMT) plays a critical role. Whether inhibition of mTOR effects via EMT reversal in GBC remains unclear. Using genetic and pharmacologic inhibitions of mTOR, we investigated the changes of EMT levels in GBC cells. Expressions of EMT related genes were also studied. Migration and invasion assays were carried out and in vivo tumour metastasis mouse models were established. Circulating tumour DNA was quantified. We used EMT index (ratio of Vimentin/Ecadherin expression) to profile EMT levels. We found that inhibition of mTOR using shRNAs and rapamycin inhibited EMT in GBC-SD gallbladder cancer cells. Inhibition of mTOR inhibited EMT in GBC-SD cells in TGF-ß-dependent manner, which was contributed majorly by mTORC2 inhibition. Rapamycin decreased invasiveness and migration of GBC-SD cells in vitro and in vivo. We have in the current study shown that rapamycin diminishes the ability of invasion and migration of GBC via inhibition of TGF-ß-dependent EMT. Our findings contribute to the understanding of the carcinogenesis of GBC.

miR-125b suppresses cellular proliferation by targeting c-FLIP in gallbladder carcinoma.

Gallbladder carcinoma (GBC) is the most common malignant tumor of the biliary tract. The incidence rate of gallbladder cancer ranks sixth among gastrointestinal types of cancer, and its incidence is increasing each year. Further clarification of the pathogenesis of GBC is essential, and identification of novel effective treatments is required. It has been previously demonstrated that high expression of the anti-apoptotic protein cellular Fas-associated death domain-like interleukin-1-converting enzyme inhibitory protein (c-FLIP) in GBC inhibited apoptosis in gallbladder cancer cells. In subsequent experiments, it was observed that microRNA (miR)-125b could target c-FLIP and inhibit the protein expression of c-FLIP by binding to the 3'untranslated regions of c-FLIP mRNA. In addition, the expression of miR-125b in GBC was significantly decreased, and the growth of gallbladder cancer cells was inhibited by the overexpression of miR-125b. The present study demonstrated that miR-125b could suppress the proliferation of gallbladder cancer cells by targeting c-FLIP. c-FLIP enriched the target gene pathway of miR-125b and may serve as a novel target for the treatment of GBC.

MicroRNA-26a acts as a tumor suppressor inhibiting gallbladder cancer cell proliferation by directly targeting HMGA2.

MicroRNAs (miRNAs) are a class of small, single-stranded, non-coding RNA molecules which can act as oncogenes or tumor suppressor genes in human cancer. However, the possible functions and mechanisms of miRNA action in gallbladder cancer (GBC) have not been elucidated. In the present study, it was found that miR-26a was often downregulated in GBC and the expression of miR-26a was associated with neoplasm histological grade. miR-26a significantly inhibited the proliferation of GBC cells based on the gain-of-function assays. Furthermore, we demonstrated that high mobility group AT-hook 2 (HMGA2) was a direct target of miR-26a. The results showed that HMGA2 mRNA levels and miR-26a levels were negatively correlated. In addition, we confirmed that reintroduction of HMGA2 antagonized the inhibition of miR-26a to GBC cell proliferation and all these effects were achieved through the cell cycle. Together, all these results suggest that miR-26a expression contributes to GBC proliferation by targeting HMGA2. miR-26a shows promise as a prognosis factor and therapeutic target of GBC patients.