Acute myeloid leukemia (AML) with mutated NPM1 shows distinctive biologic and clinical features, including absent/low CD34 expression, the significance of which remains unclear. Therefore, we analyzed CD34⁺ cells from 41 NPM1-mutated AML. At flow cytometry, 31 of 41 samples contained less than 10% cells showing low intensity CD34 positivity and variable expression of CD38. Mutational analysis and/or Western blotting of purified CD34⁺ cells from 17 patients revealed NPM1-mutated gene and/or protein in all. Immunohistochemistry of trephine bone marrow biopsies and/or flow cytometry proved CD34⁺ leukemia cells from NPM1-mutated AML had aberrant nucleophosmin expression in cytoplasm. NPM1-mutated gene and/or protein was also confirmed in a CD34⁺ subfraction exhibiting the phenotype (CD34⁺/CD38⁻/CD123⁺/CD33⁺/CD90⁻) of leukemic stem cells. When transplanted into immunocompromised mice, CD34⁺ cells generated a leukemia recapitulating, both morphologically and immunohistochemically (aberrant cytoplasmic nucleophosmin, CD34 negativity), the original patient9s disease. These results indicate that the CD34⁺ fraction in NPM1-mutated AML belongs to the leukemic clone and contains NPM1-mutated cells exhibiting properties typical of leukemia-initiating cells. CD34⁻ cells from few cases (2/15) also showed significant leukemia-initiating cell potential in immunocompromised mice. This study provides further evidence that NPM1 mutation is a founder genetic lesion and has potential implications for the cell-of-origin and targeted therapy of NPM1-mutated AML.

Ankyloblepharon‐ectodermal defects‐cleft lip/palate (AEC) syndrome, which is characterized by cleft palate and severe defects of the skin, is an autosomal dominant disorder caused by mutations in the gene encoding transcription factor p63. Here, we report the generation of a knock‐in mouse model for AEC syndrome (p63^+/L514F) that recapitulates the human disorder. The AEC mutation exerts a selective dominant‐negative function on wild‐type p63 by affecting progenitor cell expansion during ectodermal development leading to a defective epidermal stem cell compartment. These phenotypes are associated with impairment of fibroblast growth factor (FGF) signalling resulting from reduced expression of Fgfr2 and Fgfr3, direct p63 target genes. In parallel, a defective stem cell compartment is observed in humans affected by AEC syndrome and in Fgfr2b^−/− mice. Restoring Fgfr2b expression in p63^+/L514F epithelial cells by treatment with FGF7 reactivates downstream mitogen‐activated protein kinase signalling and cell proliferation. These findings establish a functional link between FGF signalling and p63 in the expansion of epithelial progenitor cells and provide mechanistic insights into the pathogenesis of AEC syndrome. See accompanying article http://dx.doi.org/10.1002/emmm.201100202

Context: A previous micro-RNA expression profile of thyroid follicular adenomas identified miR-142 precursor among the miRNAs downregulated in the neoplastic tissues compared to normal thyroid gland. Objective: The aim of this work has been to assess the expression of miR-142–3p in a large panel of follicular thyroid adenomas and carcinomas and evaluate its effect on thyroid cell proliferation and target expression. Design: The expression of miR-142–3p was analyzed by qRT-PCR in thyroid follicular adenomas and carcinomas, compared to normal thyroids. MiR-142–3p expression was restored in WRO cells and the effects on cell proliferation and target expression were evaluated. Results: Here we show that miR-142–3p is downregulated in FTAs, FTCs, and FVPTCs. MiR-142–3p was demonstrated to reduce the proliferation rate of WRO and FTC133 cells, supporting its tumor suppressor role in thyroid cancerogenesis. Moreover, this microRNA was able to downregulate the expression of ASH1L and MLL1, by direct and indirect mechanisms, respectively. Consistently, an inverse correlation between miR-142–3p expression and ASH1L and MLL1 proteins was found in thyroid follicular adenomas and carcinomas. ASH1L and MLL1, which belong to the Trithorax group (TrxG) proteins and are major regulators of Homeobox gene expression, maintain active target gene transcription by histone 3 lysine 4 methylation. Interestingly, we found that FTCs and FTC cell lines express tumor specific, shorter forms of the two proteins. The capability of miR-142–3p to modulate the levels of these tumor-associated forms and to reactivate thyroid-specific Hox gene expression, likely contributes to its tumor suppressive function. Conclusions: These data demonstrate that miR-142–3p downregulation has a role in thyroid tumorigenesis, by regulating ASH1L and MLL1.

High-mobility group A1 (HMGA1) proteins are architectural chromatinic proteins, abundantly expressed during embryogenesis and in most cancer tissues, but expressed at low levels or absent in normal adult tissues. Several studies have demonstrated that HMGA1 proteins play a causal role in neoplastic cell transformation. The aim of this study was to investigate the role of these proteins in the control of cancer stem cells (CSCs), which have emerged as a preferred target in cancer therapy, because of their role in cancer recurrence. We observed that HMGA1 is overexpressed in colon tumour stem cell (CTSC) lines compared to normal and colon cancer tissues. We demonstrated that HMGA1 silencing in CTSCs increases stem cell quiescence and reduces self-renewal and sphere-forming efficiency (SFE). The latter, together with the upregulation and asymmetric distribution of NUMB, is indicative of the recovery of an asymmetric division pattern, typical of normal stem cells. We further found that HMGA1 transcriptionally regulates p53, which is known to control the balance between symmetric and asymmetric divisions in CSCs. Therefore, our data indicate a critical role for HMGA1 in regulating both self-renewal and the symmetric/asymmetric division ratio in CSCs, suggesting that blocking HMGA1 function may be an effective anti-cancer therapy.

Research from JAMA Surgery — Combined CD133/CD44 Expression as a Prognostic Indicator of Disease-Free Survival in Patients With Colorectal Cancer

BACKGROUND: Despite the well recognized expression of the cell surface markers cluster of differentiation 44 (homing cell adhesion molecule) and CD133 (Prominin 1) on human colorectal cancer stem cells (CCSCs), these molecules do not appear to be effective targets for stem cell‐directed therapies. Because the surface marker CD66c (also known as carcinoembryonic antigen‐related cell adhesion molecule 6) has demonstrated promise as a therapeutic target in pancreatic malignancy, the authors evaluated its potential as a target for stem cell‐directed treatment of colorectal cancer.METHODS: First, the authors characterized CD66c expression by flow cytometry and immunohistochemistry in colon cancer samples and in normal colon tissues. Then, the coexpression of CD66c and CD133 was evaluated on putative CCSCs. CD66c expression also was measured in stem cell‐enriched colon spheres. Finally, the effects of small‐interfering RNA‐mediated CD66c silencing on the in vitro and in vivo growth of Caco2 colon cancer cells were evaluated.RESULTS: CD66c expression was significantly higher in colon cancers than in contiguous normal colon tissues and paralleled cancer stage. CD66c was absent in CD133‐positive cells that were isolated from normal colon, whereas its expression was brightest (CD66c^bright) in CD133‐positive cells from colon cancer samples. In vitro experiments demonstrated that colon spheres were considerably enriched in a CD66c^bright population in a fashion comparable to the enrichment observed in fresh liver metastases. In vitro proliferation and clonogenic potential were hampered when CD66c was silenced in Caco2 cells. Finally, in vivo xenograft experiments demonstrated that CD66c silencing almost completely abrogated the tumorigenic potential of Caco2 cells.CONCLUSIONS: CD66c^bright expression was associated with colon cancer stem cells and CD66c silencing blocked tumor growth, thereby opening the way to a potential new treatment for colon cancer. Cancer 2013. © 2012 American Cancer Society.