The existence of a hematopoietic stem cell niche as a spatially confined regulatory entity relies on the notion that hematopoietic stem and progenitor cells (HSPCs) are strategically positioned in unique bone marrow (BM) microenvironments with defined anatomical and functional features. Here, we employ a powerful imaging cytometry platform to perform a comprehensive quantitative analysis of HSPC distribution in BM cavities of femoral bones. We find that HSPCs preferentially localize in endosteal zones, where the majority closely interacts with sinusoidal and non-sinusoidal BM microvessels, which form a distinctive circulatory system. In situ tissue analysis reveals that HSPCs exhibit a hypoxic profile, defined by strong retention of pimonidazole and expression of HIF-1α, regardless of localization throughout the BM, adjacency to vascular structures or cell cycle status. These studies argue that the characteristic hypoxic state of HSPCs is not solely the result of a minimally oxygenated niche but may be partially regulated by cell-specific mechanisms.

This study provides additional evidence that cancer risk, especially for lung and colorectal cancer, is elevated in individuals with periodontitis. Additional research is needed to understand cancer site-specific and racial differences in findings.

BackgroundThe embryonic stem cell (ESC) factor, SALL4, plays an essential role in both development and leukemogenesis. It is a unique gene that is involved in self-renewal in ESC and leukemic stem cell (LSC).Methodology/Principal FindingsTo understand the mechanism(s) of SALL4 function(s), we sought to identify SALL4-associated proteins by tandem mass spectrometry. Components of a transcription repressor Mi-2/Nucleosome Remodeling and Deacetylase (NuRD) complex were found in the SALL4-immunocomplexes with histone deacetylase (HDAC) activity in ESCs with endogenous SALL4 expression and 293T cells overexpressing SALL4. The SALL4-mediated transcriptional regulation was tested on two potential target genes: PTEN and SALL1. Both genes were confirmed as SALL4 downstream targets by chromatin-immunoprecipitation, and their expression levels, when tested by quantitative reverse transcription polymerase chain reaction (qRT-PCR), were decreased in 293T cells overexpressing SALL4. Moreover, SALL4 binding sites at the promoter regions of PTEN and SALL1 were co-occupied by NuRD components, suggesting that SALL4 represses the transcriptions of PTEN and SALL1 through its interactions with the Mi-2/NuRD complex. The in vivo repressive effect(s) of SALL4 were evaluated in SALL4 transgenic mice, where decreased expressions of PTEN and SALL1 were associated with myeloid leukemia and cystic kidneys, respectively.Conclusions/SignificanceIn summary, we are the first to demonstrate that stem cell protein SALL4 represses its target genes, PTEN and SALL1, through the epigenetic repressor Mi-2/NuRD complex. Our novel finding provides insight into the mechanism(s) of SALL4 functions in kidney development and leukemogenesis.

The inflammatory microenvironment plays an important role in the pathogenesis and progression of tumors and may be associated with somatic genomic alterations. We examined the association of tumor infiltrating T-cell density with clinical-pathologic variables, tumor molecular subtype and oncologic outcomes in surgically-treated primary prostate cancer occurring in patients of European-American or African-American ancestry. We evaluated 312 primary prostate tumors, enriched for patients with African-American ancestry and high grade disease. Tissue microarrays were immunostained for CD3, CD8 and FOXP3 and were previously immunostained for ERG and PTEN using genetically validated protocols. Image analysis for quantification of T-cell density in tissue microarray tumor spots was performed. Automated quantification of T-cell densities in tumor-containing regions of tissue microarray spots and standard histologic sections were correlated (r=0.73, p<0.00001) and there was good agreement between visual and automated T-cell density counts on tissue microarray spots (r=0.93, p<0.00001). There was a significant correlation between CD3+, CD8+ and FOXP3+ T-cell densities (p<0.00001), but these were not associated with most clinical or pathologic variables. Increased T-cell density was significantly associated with ERG positivity (median 309 vs 188 CD3+ T-cells/mm2; p=0.0004) and also with PTEN loss (median 317 vs 192 CD3+ T-cells/mm2; p=0.001) in the combined cohort of matched European-American and African-American ancestry patients. The same association or a similar trend was present in patients of both ancestries when analyzed separately. When the African-American patients from the matched race set were combined with a separate high grade set of African-American cases, there was a weak association of increased FOXP3+ T-cell densities with increased risk of metastasis in multivariable analysis. Though high T-cell density is associated with specific molecular subclasses of prostate cancer, we did not find an association of T-cell density with racial ancestry.

Our previous work shows that the stem cell factor SALL4 plays a central role in embryonic and leukemic stem cells. In this study, we report that SALL4 expression was higher in drug resistant primary acute myeloid leukemic patients than those from drug-responsive cases. In addition, while overexpression of SALL4 led to drug resistance in cell lines, cells with decreased SALL4 expression were more sensitive to drug treatments than the parental cells. This led to our investigation of the implication of SALL4 in drug resistance and its role in side population (SP) cancer stem cells. SALL4 expression was higher in SP cells compared to non-SP cells by 2–4 fold in various malignant hematopoietic cell lines. Knocking down of SALL4 in isolated SP cells resulted in a reduction of SP cells, indicating that SALL4 is required for their self-renewal. The SP phenotype is known to be mediated by members of the ATP-binding cassette (ABC) drug transport protein family, such as ABCG2 and ABCA3. Using chromatin-immunoprecipitation (ChIP), quantitative reverse transcription polymerase chain reaction (qRT-PCR) and electrophoretic mobility shift assay(EMSA), we demonstrated that SALL4 was able to bind to the promoter region of ABCA3 and activate its expression while regulating the expression of ABCG2 indirectly. Furthermore, SALL4 expression was positively correlated to those of ABCG2 and ABCA3 in primary leukemic patient samples. Taken together, our results suggest a novel role for SALL4 in drug sensitivity, at least in part through the maintenance of SP cells, and therefore may be responsible for drug-resistance in leukemia. We are the first to demonstrate a direct link between stem cell factor SALL4, SP and drug resistance in leukemia.

Esophageal squamous cell carcinoma (ESCC) is 1 of the most common cancers worldwide. In our study, cDNA microarray comprising 14,803 genes was employed to identify gene-specific expression profile in 6 paired samples of ESCC. Nine genes identified were commonly upregulated and 36 downregulated in tumors, as compared to normal esophageal squamous epithelia. Among these genes, we found that 9 of the altered expression genes were related to arachidonic acid (AA) metabolism, such as annexin-I, annexin-II, S100A8, S100A10, S100P, glutathione peroxidase-3, phosphatidylcholine transfer protein, aldo-keto reductase family 1 and cyclooxygenase-2 (COX-2). To gain insights into the regulation of the AA metabolism pathway involved in the carcinogenesis of ESCC, we investigated the expression of 8 genes related to the AA metabolism by semiquantitative reverse transcript ( Esophageal cancer is 1 of the most lethal malignancies in the world. It exists in 2 main pathologic types, esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EADC). ESCC is the predominant histologic subtype of esophageal cancer and characterized by high mortality rate and geographic differences in incidence. 1 It occurs at very high frequencies in some countries, including China and especially in the south side of the Taihang mountains on the borders of 3 provinces (Henan, Hebei and Shanxi). Due to the relatively late stage of diagnosis and the poor efficacy of treatment, 5-year survival rate is below 10%. 2 The development of better treatment modalities and better diagnostic and preventive approaches requires the understanding of the molecular mechanisms of the complex process of esophageal tumorigenesis. Genetic factors were speculated to be 1 of the most important causes for the high prevalence and familial aggregation of ESCC in China. 3 Previous studies showed that some of the complicated genetic alternation had been found in the tumorigenesis of esophagus, such as point mutations of p53 and p16; amplification of cycline D, c-myc, hst-1, int-2 and epidermal growth factor receptor; as well as allelic loss on chromosomes 3p, 5q, 9p21-22, 13q and 17p. 4 -7 But this is not sufficient to understand the common pathway of carcinogenesis and progression of ESCC. A previous study in our lab also revealed that a Mendelian autosomal recessive major gene underlying susceptibility to ESCC played a significant role in the etiology of ESCC in a moderate high-incidence area of northern China. 8 However, the molecular pathways involved in the pathogenesis of ESCC are poorly understood.Advances in cDNA microarray technologies have enabled the definition of thousands of genes' expression changes simultaneously. Previous studies have been successfully performed in ESCC. 9 -11 These studies have begun to provide valuable information to understand the development and progression of ESCC. In the present study, in order to uncover the molecular pathways involved in complicated biologic processes of the esophageal epithelium malignant transformation, we...

The embryonic self-renewal factor SALL4 has been implicated in the development of human acute myeloid leukemia (AML). Transgenic mice expressing the human SALL4B allele develop AML, which indicates that this molecule contributes to leukemia development and maintenance. However, the underlying mechanism of SALL4-dependent AML progression is unknown. Using SALL4B transgenic mice, we observed that HoxA9 was significantly upregulated in SALL4B leukemic cells compared with wild-type controls. Downregulation of HoxA9 in SALL4B leukemic cells led to decreased replating capacity in vitro and delayed AML development in recipient mice. In primary human AML cells, downregulation of SALL4 led to decreased HOXA9 expression and enhanced apoptosis. We found that SALL4 bound a specific region of the HOXA9 promoter in leukemic cells. SALL4 overexpression led to enhanced binding of histone activation markers at the HOXA9 promoter region, as well as increased HOXA9 expression in these cells. Furthermore, we observed that SALL4 interacted with mixed-lineage leukemia (MLL) and co-occupied the HOXA9 promoter region with MLL in AML leukemic cells, which suggests that a SALL4/MLL pathway may control HOXA9 expression. In summary, our findings revealed a molecular mechanism for SALL4 function in leukemogenesis and suggest that targeting of the SALL4/MLL/HOXA9 pathway would be an innovative approach in treating AML.

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