Peritoneal dissemination in gastric cancer is a common fatal clinical condition with few effective therapies available. We studied the therapeutic effect of a tumor-targeting drug delivery system that uses cisplatin-encapsulated and Tf-conjugated PEG liposomes (Tf-PEG liposomes) in nude mice with peritoneal dissemination of human gastric cancer cells. Small unilamellar Tf-PEG, PEG or DSPC/CH liposomes (bare liposomes) encapsulating cisplatin were prepared by reversephase evaporation followed by extrusion. Electron microscopic studies revealed that Tf-PEG liposomes were internal- Key words: liposome; targeting; transferrin; peritoneal dissemination; gastric cancerPeritoneal dissemination is the most frequent noncurative factor and the most common type of recurrence after curative surgery in patients with gastric cancer. 1 Control of this metastasis is one of the most important challenges in treating gastric cancer. There have been few reports of effective treatment for peritoneal dissemination in patients with gastric cancer. 2,3 As a clinical locoregional chemotherapy, various anticancer drugs in solution form have been administered i.p. to expose the drug directly to peritoneal tumor cells. 4 However, small water-soluble molecules, such as cisplatin or mitomycin C, are absorbed easily through the large peritoneal surface into the circulating blood. It is difficult to maintain a high drug concentration for a long time in the peritoneal cavity. 5,6 Therefore, i.p. administration of anticancer drugs in solution form does not always produce the desired effect.Liposomes, known to be drug carriers, have various advantages. 7,8 First, they encapsulate various drugs such as water-soluble, lipid-soluble or high m.w. substances and release them in a sustained manner. Second, the antigenicity and toxicity of liposomes are very low because they consist of lipid, which is a natural component of organisms. Third, the biodistribution of liposomes can be controlled by the size or lipid component. Fourth, various materials, such as antibodies or chemical compounds, can modify the surfaces of liposomes. However, the therapeutic application of liposomes has been limited by their rapid clearance from the bloodstream and by their uptake by the RES. Recent efforts have been made to reformulate the liposome composition, to reduce its affinity to the RES. Liposomes modified with amphipathic PEG are not readily taken up by macrophages in the RES and, hence, stay in the circulation for a relatively long time. 9 -14 To increase the therapeutic effect and decrease side effects, tumor-specific targeting therapy has been advocated. Intracellular targeting using iron-saturated Tf as a ligand for receptor-mediated endocytosis has attracted attention. Tf is a glycoprotein that transports ferric ions in the body and the Tf receptor is internalized into cells by endocytosis through the binding of Tf. This receptormediated endocytosis is a normal physiologic process by which iron is delivered to cells. [15][16][17] Also, the Tf receptor concen...
The presence of isolated tumor cells in the peripheral blood (PB) and bone marrow (BM) is an important factor contributing to the metastasis of solid cancers. Moreover, recent studies have demonstrated that various types of host cells are also involved in cancer development and metastasis. BM microenvironment is thought to be a good reflection of the interplay between tumor cells and cancer-associated host cells in metastatic sites compared to the bloodstream. We performed RNA-seq analysis of the BM samples from 8 gastric cancer (GC) patients (Stages I and IV: n = 4 each) in order to identify candidate prognostic markers, and revealed higher expression of multiple histone mRNAs in Stage IV patients. Results were validated through qRT-PCR analysis of HIST1H3D expression in 175 BM, 92 PB, and 115 primary tumor (PT) samples from GC patients. HIST1H3D expression in the BM, PB, and PT of Stage IV patients was higher than that in Stage I patients (p = 0.0284, 0.0243, 0.0006, respectively). In silico analysis revealed that most of the histone genes upregulated in BM samples from Stage IV GC patients had predictive target sites for microRNA 760 (miR-760) in their 3′ UTRs. miR-760 expression was assayed using qRT-PCR in 105 BM and 96 PT samples. In contrast to histone mRNA expression, miR-760 was downregulated in the BM and PT of Stage IV patients compared to Stage I patients (p = 0.0094 and 0.0018, respectively). Direct interaction between miR-760 and histone mRNA was confirmed by luciferase analysis in a GC cell line, NUGC3. HIST1H3D expression was downregulated in 3 GC cell lines (NUGC3, KE39, and KATOIII) after Pre-miR-760 transfection in both mRNA and protein levels. We also examined miR-760 expression levels of noncancerous host cells in samples from GC patients. In BM samples from another set of 4 GC patients, the CD14 positive fraction exhibited the same degree of miR-760 expression compared to a CD45/EpCAM+ fraction. Moreover, in corresponding noncancerous tissues from primary gastric tumors, miR-760 expression was lower in Stage IV patients than in Stage I patients. These results suggest that changes in miR-760 expression in host noncancerous cells are also associated with GC progression. In conclusion, histone mRNA is upregulated, while miR-760 is downregulated in the BM and PT of advanced GC patients and proposed that the histone mRNA/miR-760 axis may have a crucial role in the development of GC. Citation Format: Takeshi Iwaya, Takeo Fukagawa, Yutaka Suzuki, Tomoya Sudo, Kaoru Ishida, Kohei Kume, Satoshi Nishizuka, Hisae Iinuma, Masaki Mori, Mitsuru Sasako, Go Wakabayashi, Koshi Mimori. MicroRNA 760 regulates gastric cancer progression by downregulation of histone mRNA expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5201. doi:10.1158/1538-7445.AM2014-5201
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