Identification of a novel subpopulation of tumor-initiating cells from gemcitabine-resistant pancreatic ductal adenocarcinoma patients.

Pancreatic ductal adenocarcinoma is highly resistant to systemic chemotherapy. Although there are many reports using pancreatic cancer cells derived from patients who did not receive chemotherapy, characteristics of pancreatic cancer cells from chemotherapy-resistant patients remain unclear. In this study, we set out to establish a cancer cell line in disseminated cancer cells derived from gemcitabine-resistant pancreatic ductal adenocarcinoma patients. By use of in vitro co-culture system with stromal cells, we established a novel pancreatic tumor-initiating cell line. The cell line required its direct interaction with stromal cells for its in vitro clonogenic growth and passaging. Their direct interaction induced basal lamina-like extracellular matrix formation that maintained colony formation. The cell line expressed CD133 protein, which expression level changed autonomously and by culture conditions. These results demonstrated that there were novel pancreatic tumor-initiating cells that required direct interactions with stromal cells for their in vitro cultivation in gemcitabine-resistant pancreatic ductal adenocarcinoma. This cell line would help to develop novel therapies that enhance effects of gemcitabine or novel anti-cancer drugs.

Hypoxia induces tumor aggressiveness and the expansion of CD133-positive cells in a hypoxia-inducible factor-1α-dependent manner in pancreatic cancer cells.

BACKGROUND: Intratumoral hypoxia is known to lead to increased aggressiveness and distant metastasis. However, the interplay underlying these actions is still unknown. OBJECTIVE: We explored whether cancer cells might acquire a stem-like phenotype under hypoxia, consequently leading to an aggressive phenotype, including invasiveness and metastasis. METHODS: Under normoxia (20% O(2)) or hypoxia (1% O(2)), the expression of CD133 (cancer stem cell marker), CXC chemokine receptor 4 (CXCR4) and hypoxia-inducible factor-1α (HIF-1α) was examined by RT-PCR and immunostaining using human pancreatic cancer cell lines. We also examined if hypoxia facilitates the invasiveness of CD133+ cancer cells. Furthermore, we transfected dominant active HIF-1α (HIF-1αΔODD) by the retroviral gene transfer and examined the effects both in vitro and in vivo. RESULTS: Compared with normoxia, hypoxia elevated the expression of CD133, CXCR4 and HIF-1α. Moreover, hypoxia facilitated the invasiveness of CD133+ pancreatic cancer cells. The behavior of HIF-1αΔODD-transfected cells under normoxia was compatible with that of the parent cells under hypoxia. Furthermore, a xenograft model of HIF-1αΔODD cells showed aggressiveness, including metastasis and highly tumorigenic ability. CONCLUSION: Hypoxia induces tumor aggressiveness associated with the expansion of CD133+ pancreatic cancer cells in a predominantly HIF-1α-dependent manner.

Impact of the DISC1 Ser704Cys polymorphism on risk for major depression, brain morphology and ERK signaling.

Disrupted-in-schizophrenia 1 (DISC1), identified in a pedigree with a familial psychosis with the chromosome translocation (1:11), is a putative susceptibility gene for psychoses such as schizophrenia and bipolar disorder. Although there are a number of patients with major depressive disorder (MDD) in the family members with the chromosome translocation, the possible association with MDD has not yet been studied. We therefore performed an association study of the DISC1 gene with MDD and schizophrenia. We found that Cys704 allele of the Ser704Cys single-nucleotide polymorphism (SNP) was associated with an increased risk of developing MDD (P=0.005, odds ratio=1.46) and stronger evidence for association in a multi-marker haplotype analysis containing this SNP (P=0.002). We also explored possible impact of Ser704Cys on brain morphology in healthy volunteers using MR imaging. We found a reduction in gray matter volume in cingulate cortex and a decreased fractional anisotropy in prefrontal white matter of individuals carrying the Cys704 allele compared with Ser/Ser704 subjects. In primary neuronal culture, knockdown of endogenous DISC1 protein by small interfering RNA resulted in the suppression of phosphorylation of ERK and Akt, whose signaling pathways are implicated in MDD. When effects of sDISC1 (Ser704) and cDISC1 (Cys704) proteins were examined separately, phosphorylation of ERK was greater in sDISC1 compared with cDISC1. A possible biological mechanism of MDD might be implicated by these convergent data that Cys704 DISC1 is associated with the lower biological activity on ERK signaling, reduced brain gray matter volume and an increased risk for MDD.

Effect of systemic administration of D-serine on the levels of D- and L-serine in several brain areas and periphery of rat.

To obtain further insight into the distribution and metabolism of exogenous D-serine, we have investigated the effect of the intraperitoneal administration of D-serine (10 mmol/kg) on the concentrations of D- and L-serine in several brain areas and periphery of infant and adult rats. The administration produced a significant augmentation of the D-serine levels not only in the cortex but also in the hippocampus, striatum, cerebellum and periphery. The rapid decline in the enhanced D-serine levels was observed in the periphery and cerebellum, whereas the injection caused a prolonged elevation of the D-serine levels in the cortex and hippocampus. The application caused a slight increase in the L-serine levels in several brain areas and periphery 3 or 6 h after the injection, whereas a significant decrease in the L-serine concentration was observed in the periphery, diencephalon and cerebellum 3 or 7 days after the injection. Because a structural abnormality and N-methyl-D-aspartate (NMDA) receptor hypofunction has been demonstrated in the cortex and hippocampus of schizophrenic subjects, D-serine treatment may offer a new therapeutic approach to diseases related to the hypofunction of NMDA receptors such as schizophrenia.