Taiki Moriyama

MicroRNA-21 modulates biological functions of pancreatic cancer cells including their proliferation, invasion, and chemoresistance.

Due to the poor prognosis of pancreatic cancer, novel diagnostic modalities for early diagnosis and new therapeutic strategy are urgently needed. Recently, microRNA-21 (miR-21) was reported to be strongly overexpressed in pancreatic cancer as well as in other solid cancers. We investigated the functional roles of miR-21, which have not been fully elucidated in pancreatic cancer. miR-21 expression was assessed in pancreatic cancer cell lines (14 cancer cell lines, primary cultures of normal pancreatic epithelial cells and fibroblasts, and a human normal pancreatic ductal epithelial cell line) and pancreatic tissue samples (25 cancer tissues and 25 normal tissues) by quantitative real-time reverse transcription-PCR amplification. Moreover, we investigated the proliferation, invasion, and chemoresistance of pancreatic cancer cells transfected with miR-21 precursor or inhibitor. miR-21 was markedly overexpressed in pancreatic cancer cells compared with nonmalignant cells, and miR-21 in cancer tissues was much higher than in nonmalignant tissues. The cancer cells transfected with the miR-21 precursor showed significantly increased proliferation, Matrigel invasion, and chemoresistance for gemcitabine compared with the control cells. In contrast, inhibition of miR-21 decreased proliferation, Matrigel invasion, and chemoresistance for gemcitabine. Moreover, miR-21 positively correlated with the mRNA expression of invasion-related genes, matrix metalloproteinase-2 and -9, and vascular endothelial growth factor. These data suggest that miR-21 expression is increased in pancreatic cancer cells and that miR-21 contributes to the cell proliferation, invasion, and chemoresistance of pancreatic cancer.[Mol Cancer Ther 2009;8(5):1067–74]

CD10+ pancreatic stellate cells enhance the progression of pancreatic cancer

BACKGROUND & AIMS Pancreatic stellate cells (PSCs) promote the progression of pancreatic cancer by producing extracellular matrix and soluble factors. However, the functional heterogeneity of PSCs has not been identified until now. Detailed characterization of the PSCs in human pancreatic cancer would provide a set of potential targets for stroma-directed therapy. METHODS We isolated PSCs from fresh pancreatic ductal adenocarcinoma tissue and sorted them by flow cytometry according to cell surface expression of CD10, which is a stromal prognostic marker for various tumors. We analyzed the functional differences between CD10(+) PSCs and CD10(-) PSCs. RESULTS Immunohistochemical analysis showed that the frequency of CD10 expression by PSCs was markedly higher in tumor tissue than in normal tissue (33.7% vs 0%, respectively, P = .028). In pancreatic ductal adenocarcinoma, CD10 expression by PSCs was associated with positive nodal metastases (P = .011) and a shorter survival time (P < .001). In vitro coculture experiments showed that CD10(+) PSCs promoted the invasiveness of pancreatic cancer cell lines, SUIT-2 and Panc-1 cells more intensively than CD10(-) PSCs. CD10(+) PSCs significantly increased the tumor growth and invasiveness of SUIT-2 cells in a murine cotransplantation model. CD10(+) PSCs secreted higher levels of matrix metalloproteinase 3 than CD10(-) PSCs, and knockdown of matrix metalloproteinase 3 in cocultured PSCs reduced the invasion of SUIT-2 and Panc-1 cells. CONCLUSIONS CD10(+) PSCs enhance the progression of pancreatic cancer cells. CD10(+) PSCs may be a candidate for selective therapeutic targeting in the treatment of pancreatic cancer.

Enhanced cell migration and invasion of CD133+ pancreatic cancer cells cocultured with pancreatic stromal cells

Recently, cancer stem cells have been reported as a new therapeutic target in pancreatic cancer as well as other cancers, but the specific role of these cells is unknown.

Tumor–stromal interactions with direct cell contacts enhance proliferation of human pancreatic carcinoma cells

Pancreatic ductal adenocarcinoma is often characterized by an abundant desmoplastic stroma that is partially induced by activated pancreatic stellate cells (PSCs). Indirect co‐culture has often been used to investigate the effects of cancer–stromal interactions on the proliferation of cancer cells, but the effects of cell–cell adhesion and juxtacrine signaling between cancer and stromal cells cannot be evaluated using this method. This study aimed to establish a simplified direct co‐culture system that could be used to quantify populations of cancer cells in co‐culture with PSCs, and to evaluate the effects of direct cell contact on the proliferation of cancer cells. We established three green fluorescent protein (GFP)‐expressing pancreatic cancer cell lines and were able to quantify them with high reliability and reproducibility, even when co‐cultured directly with PSCs, using a color plate reader. We assessed the differential effects of direct and indirect co‐culture with PSCs on the proliferation of cancer cells, and found that the proliferation of GFP‐expressing pancreatic cancer cell lines was dramatically enhanced by direct co‐culture with PSCs, compared with the indirect co‐culture system. We also found that direct co‐culture of cancer cells and PSCs activated the Notch signaling pathway in both cell types. Direct cell contact between cancer cells and PSCs plays an important role in the control of cancer cell proliferation, and is essential to the understanding of tumor–stromal interactions. (Cancer Sci 2009; 100: 2309–2317)

Prospectively Isolated Cancer-Associated CD10+ Fibroblasts Have Stronger Interactions with CD133+ Colon Cancer Cells than with CD133− Cancer Cells

Although CD133 has been reported to be a promising colon cancer stem cell marker, the biological functions of CD133+ colon cancer cells remain controversial. In the present study, we investigated the biological differences between CD133+ and CD133− colon cancer cells, with a particular focus on their interactions with cancer-associated fibroblasts, especially CD10+ fibroblasts. We used 19 primary colon cancer tissues, 30 primary cultures of fibroblasts derived from colon cancer tissues and 6 colon cancer cell lines. We isolated CD133+ and CD133− subpopulations from the colon cancer tissues and cultured cells. In vitro analyses revealed that the two populations showed similar biological behaviors in their proliferation and chemosensitivity. In vivo analyses revealed that CD133+ cells showed significantly greater tumor growth than CD133− cells (P = 0.007). Moreover, in cocultures with primary fibroblasts derived from colon cancer tissues, CD133+ cells exhibited significantly more invasive behaviors than CD133− cells (P<0.001), especially in cocultures with CD10+ fibroblasts (P<0.0001). Further in vivo analyses revealed that CD10+ fibroblasts enhanced the tumor growth of CD133+ cells significantly more than CD10− fibroblasts (P<0.05). These data demonstrate that the in vitro invasive properties and in vivo tumor growth of CD133+ colon cancer cells are enhanced in the presence of specific cancer-associated fibroblasts, CD10+ fibroblasts, suggesting that the interactions between these specific cell populations have important roles in cancer progression. Therefore, these specific interactions may be promising targets for new colon cancer therapies.

Hypoxic stellate cells of pancreatic cancer stroma regulate extracellular matrix fiber organization and cancer cell motility

Desmoplasia and hypoxia in pancreatic cancer mutually affect each other and create a tumor-supportive microenvironment. Here, we show that microenvironment remodeling by hypoxic pancreatic stellate cells (PSCs) promotes cancer cell motility through alteration of extracellular matrix (ECM) fiber architecture. Three-dimensional (3-D) matrices derived from PSCs under hypoxia exhibited highly organized parallel-patterned matrix fibers compared with 3-D matrices derived from PSCs under normoxia, and promoted cancer cell motility by inducing directional migration of cancer cells due to the parallel fiber architecture. Microarray analysis revealed that procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2) in PSCs was the gene that potentially regulates ECM fiber architecture under hypoxia. Stromal PLOD2 expression in surgical specimens of pancreatic cancer was confirmed by immunohistochemistry. RNA interference-mediated knockdown of PLOD2 in PSCs blocked parallel fiber architecture of 3-D matrices, leading to decreased directional migration of cancer cells within the matrices. In conclusion, these findings indicate that hypoxia-induced PLOD2 expression in PSCs creates a permissive microenvironment for migration of cancer cells through architectural regulation of stromal ECM in pancreatic cancer.

Intraoperative parathyroid hormone assay in patients with Graves' disease for prediction of postoperative tetany

We measured intraoperative parathyroid hormone (IOPTH) levels before and after thyroidectomy in a large group of patients to test whether changes in IOPTH can predict postoperative tetany. Subjects were 111 consecutive patients (94 females and 17 males) with Graves’ disease undergoing subtotal thyroidectomy. Blood samples for IOPTH assay were obtained after anesthesia (basal) and following skin closure (postoperative). Data were compared between patients who developed tetany (n = 9) and those who did not (n = 102). There was no significant difference in sex, age, period of antithyroid drug administration, or the weight of the thyroid between the two groups. The preoperative serum calcium level was significantly lower (p < 0.05) and the basal IOPTH significantly higher (p < 0.05) in the tetany group than in the non-tetany group. The IOPTH level was significantly lower (p < 0.005) and the average percent decrease in IOPTH levels was higher (p < 0.001) in the tetany group than in the non-tetany group. A decrease in IOPTH of more than 70% was shown to be 78% sensitive, 94% specific, and 93% accurate, and it has 78% positive predictive value and 94% negative predictive value for the development of tetany. Our study shows that a postoperative decrease of IOPTH level is the most predictive of postoperative tetany of the clinical risk factors investigated. We recommend IOPTH measurement as an adjunct to postoperative management of patients with Graves’ disease to assist in preventing hypocalcemia and determining the earliest time for safe discharge.

Sequential Changes in Plasma Intact and Whole Parathyroid Hormone Levels during Parathyroidectomy for Secondary Hyperparathyroidism

Most commercial assays for intact parathyroid hormone (iPTH) cross-react with non-PTH1-84 fragments (likely to be PTH7-84). We aimed to evaluate a whole PTH assay that measured only PTH1-84 by comparing it with an assay measuring iPTH levels during parathyroidectomy in secondary hyperparathyroidism (HPT). Twenty-eight patients with secondary HPT who underwent total parathyroidectomy with autotransplantation served as subjects. Blood samples for postoperative assay were drawn after anesthesia; immediately prior to excision of the last parathyroid gland; and at 5, 10, and 15 minutes after excision. The PTH7-84 level was calculated by subtracting the whole PTH value from the iPTH value. Plasma whole PTH decreased more rapidly than iPTH after parathyroidectomy (p < 0.0001). PTH levels that decreased by 50% or more from levels prior to excision to 10 minutes after excision were used to predict successful parathyroidectomy; decreases in whole PTH substantiated curative surgery for all patients without introducing false-positive and false-negative results. iPTH levels decreased by at least 50% in only 16 patients at 10 minutes after excision without false-positive results. Out of 11 cases in which iPTH decreased less than 50%, two were true-negatives and nine were false-negatives. Decreases in whole PTH levels more accurately reflect surgical outcome than do decreases in iPTH levels during parathyroidectomy in secondary HPT patients. Even though the quick iPTH assay is used infrequently during surgery for secondary HPT, our results suggest that a quick whole PTH assay may be more useful than the iPTH assay currently used in parathyroidectomy procedures for secondary HPT.

Extra-pancreatic invasion induces lipolytic and fibrotic changes in the adipose microenvironment, with released fatty acids enhancing the invasiveness of pancreatic cancer cells

Pancreatic cancer progression involves components of the tumor microenvironment, including stellate cells, immune cells, endothelial cells, and the extracellular matrix. Although peripancreatic fat is the main stromal component involved in extra-pancreatic invasion, its roles in local invasion and metastasis of pancreatic cancer remain unclear. This study investigated the role of adipose tissue in pancreatic cancer progression using genetically engineered mice (Pdx1-Cre; LSL-KrasG12D; Trp53R172H/+) and an in vitro model of organotypic fat invasion. Mice fed a high fat diet had significantly larger primary pancreatic tumors and a significantly higher rate of distant organ metastasis than mice fed a standard diet. In the organotypic fat invasion model, pancreatic cancer cell clusters were smaller and more elongated in shape and showed increased fibrosis. Adipose tissue-derived conditioned medium enhanced pancreatic cancer cell invasiveness and gemcitabine resistance, as well as inducing morphologic changes in cancer cells and increasing the numbers of lipid droplets in their cytoplasm. The concentrations of oleic, palmitoleic, and linoleic acids were higher in adipose tissue-derived conditioned medium than in normal medium, with these fatty acids significantly enhancing the migration of cancer cells. Mature adipocytes were smaller and the concentration of fatty acids in the medium higher when these cells were co-cultured with cancer cells. These findings indicate that lipolytic and fibrotic changes in peripancreatic adipose tissue enhance local invasiveness and metastasis via adipocyte-released fatty acids. Inhibition of fatty acid uptake by cancer cells may be a novel therapy targeting interactions between cancer and stromal cells.

Suppression of CD51 in pancreatic stellate cells inhibits tumor growth by reducing stroma and altering tumor-stromal interaction in pancreatic cancer

Pancreatic stellate cells (PSCs) enhance the malignant behavior of pancreatic cancer by interacting with cancer cells and producing extracellular matrix (ECM). To date, several stroma-targeted therapies for pancreatic cancer have been attempted, but these therapies are still not in practical use. Integrins expressed in stromal cells are involved in fibrosis of several organs, as well as promoting tumor malignancy. We investigated whether CD51, also known as integrin αV, expressed in PSCs was associated with stromal formation of pancreatic cancer and enhancement of tumor malignancy. We also assessed the effects of suppression of CD51 in PSCs on pancreatic cancer. Immunohistochemistry for CD51 in resected pancreatic cancer tissues showed that high expression of CD51 in the tumor stroma was associated with lymph node metastasis (P=0.025), positive pathologic margin (P=0.025), and shorter patient survival times (P=0.043). Lentivirus-mediated short hairpin RNA knockdown of CD51 decreased the proliferation and migration of PSCs. Quantitative real-time polymerase chain reaction showed that expression levels of genes related with ECM and tumor-stromal interactions were decreased by CD51 knockdown in PSCs. In a co-implantation model of pancreatic cancer cells and PSCs, tumor growth in vivo was inhibited by CD51 knockdown in PSCs (P<0.05). We also found reduced tumor stroma and decreased proliferation of cancer cells in implanted cancer tissues with CD51-silenced PSCs (P<0.05). Our results showed that CD51 expression in pancreatic cancer stroma is associated with enhanced tumor malignancy and that CD51 may be a potential therapeutic target for pancreatic cancer.