The cellular components of the hematopoietic stem cell niche have been gradually identified. However, the niche for malignant hematopoiesis remains to be elucidated. Here, using human leukemia cells, which could be transplanted to immunodeficient mice, we studied the in vivo homing, proliferation and survival sites by immunohistopathology, compared with the corresponding sites for cord blood CD34 þ (CBCD34 þ ) cells. The human leukemia cells initially localized on the surface of osteoblasts in the epiphysial region, and expanded to the inner vascular and diaphysial regions within 4 weeks. The percentage of CD34 þ leukemia cells in the bone marrow was transiently increased up to 50%. In vivo 5-bromo-2 0 -deoxyuridine labeling revealed that the epiphysis was the most active site for leukemia cell proliferation. CBCD34 þ cells showed the similar pattern of homing and proliferation to leukemia cells. After high-dose administration of cytosine-1-b-D-arabinofuranoside, residual leukemia cells were localized in the perivascular endothelium as well as in contact with the trabecular endosteum. These findings suggest that xenotransplantation into immunodeficient mice provides a useful model to study the leukemia niche.

We investigated native Japanese subjects whether C702T, C936T and G1612A polymorphisms in the 3' untranslated region (3'-UTR) of vascular endothelial growth factor (VEGF) gene are associated with the risk of renal cell carcinoma (RCC). Genomic DNAs from 145 RCC patients and 145 healthy controls were examined by polymerase chain reaction-based restriction fragment length polymorphism. Variant allele frequencies of C702T, C936T and G1612A were 0.00, 0.20 and 0.13 in the controls, respectively. The C702T and G1612A allele frequencies were significantly different between the Japanese population and the Caucasian population reported elsewhere. For each of C936T and G1612A polymorphisms, there was no statistically significant difference in the distribution of genotype frequencies between the cases and controls. Odds ratios and 95% confidence intervals computed by logistic regression analyses were not statistically significant. Stratification for the RCC cases according to pathological cell subtype, grade or stage failed to reveal any significant heterogeneity with respect to the genotype of each VEGF polymorphism. We revealed that there are significant ethnic differences in the C702T and G1612A allele frequencies, but suggested that C702T, C936T and G1612A polymorphisms in the 3'-UTR of VEGF gene are not associated with the risk of RCC, at least in Japanese population.

Human oral mucosal cells are an attractive site for tissue engineering because they are the most accessible cells in the body and easy to manipulate in vitro. They thus have possibilities for targeting by somatic gene therapy. We examined the efficiency of retrovirus-mediated gene transfer and the construction of mucosal epithelium in vivo. Human oral mucosal cells were transduced with a retroviral vector carrying the lacZ gene at high efficiency and constructed epithelium after G418 selection with 3T3 cells in vitro. The cultured oral mucosal epithelium membrane was then grafted onto immunodeficient mice. Beta-Gal expression was detected histochemically in vivo 5 weeks after grafting. Furthermore, we transduced factor IX cDNA into the mucosal epithelium membrane, and it was then transplanted into nude mice. Between 0.6 and 1.8 ng of human factor IX per milliliter was found in mouse plasma, and the production was continued for 23 days in vivo. These results confirmed that the oral mucosal epithelium is an ideal target tissue for gene therapy or tissue engineering.

Our results indicate that the present 7 cm cutoff value in the TMN system is valid in terms of prognostic value. The 4 cm cutoff value may not reflect the survival when total nephrectomy is considered, thus indicating that tumors at 4 cm cutoff value may be valid when nephron sparing surgery is considered. The 13 cm cutoff value seems to be most appropriate in N0M0 tumors with over 7 cm in diameter.

RASAL2 methylation or c-FOS mRNA or VEGFA mRNA in RCC tissues. Overexpression of RASAL2 in 786-O cells could inhibit the recruitment and tube formation of HUVECs, while RASAL2 knockdown (KD) in ACHN cells enhanced the recruitment and tube formation of HUVECs in vitro. Also, overexpression of RASAL2 could inhibit tumorigenecity of xenografts. Mechanistically, RASAL2 KD could enhance the phosphorylation of GSK3 and upregulate the expression of c-FOS and VEGFA. Furthermore, RASAL2 was inversely correlated with VEGFA and CD31 in tissues from human RCC specimens and xenografts.CONCLUSIONS: RASAL2 was downregulated in RCC tissues, which could lead to tumor angiogenesis via p-GSK3/c-FOS/VEGFA signaling pathway. Therefore, RASAL2 could be a potential target to prevent patients with RCC from resistance to anti-vascular therapy.