ING1 gene, the founding member of the ING tumor suppressor family, was originally identified through subtractive hybridization between normal mammary epithelial cells and breast cancer cell lines, and subsequent in vivo selection of genetic suppressor element that displayed oncogenic features. Soon after identification of ING1, four additional members of the ING family (ING2-5) were cloned and all the gene products contain a highly conserved plant homeodomain (PHD) finger motif in the carboxy (C)-terminal end, that plays important role for their function. Furthermore, ING family members contain nuclear localization signals and N-terminal sequences important in the interaction with histone acetyltransferase (HAT) and histone deacetyltransferase (HDAC) that regulate gene promoter activity within chromatin. Although exact functions of ING family genes have not been clarified, the gene products are involved in transcriptional regulation, apoptosis, cell cyle, angiogenesis and DNA repair through p53-dependent and -independent pathways. Chromosomal deletion and decreased expression of each ING family member gene in various cancer types strongly suggested products of these genes as tumor suppressor factors. Rare mutation but frequent allelic loss and epigenetic changes have been shown in ING family genes, suggesting them as a class II tumor suppressor gene. This review summarizes the known biological functions of the ING tumor suppressors and signaling related pathways.

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In recent years, enamel bleaching has been widely conducted clinically. Bleaching involves degrading pigments that are organic substances, and has been thought to have no effect on inorganic substances. However, no study has examined in detail how the enamel changes by bleaching. In the present study, the effects of two commercial bleaching agents; Hi-Lite (Hi-L) and Nite White Excel (NWE), on enamel were investigated by observations with contact microradiography (CMR), scanning electron microscopy (SEM), micro X ray diffractometer (XRD) and high-resolution transmission electron microscopy (HR-TEM), focusing on the effects on enamel crystals. CMR showed no change in degree of mineralization after bleaching with Hi-L or NWE as compared with the control. On SEM, gaps along the prism sheath and cracks between crystals were observed on the enamel surface of Hi-L-bleached and NWE-bleached enamel. XRD demonstrated no remarkable differences in crystal composition and crystallinity after bleaching by both agents as compared with the control. On HR-TEM, crystal growth findings were observed in some regions of Hi-L-bleached enamel, while crystal demineralization findings were observed in NWE-bleached enamel. All the above changes were limited to the very superficial layer of enamel in all the samples.

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The influence of oral administration of High Advanced-Collagen Tripeptide (HACP) developed by Jellice Co., Ltd (Sendai, Japan) for bone repairing process was investigated in rat. Cortical bone defects (1mm diameter) of the tibia were created through the medial cortex and medulla. After 1 day of operation, HACP/physiological saline solution (80mg/2ml/Kg) was orally administrated as experimental group. Only physiological saline solution was orally administrated as control group. There were no significant differences in body weight, serum levels of total proteins, calcium concentration and alkaline phosphatase activity between HACP and control groups during administration periods. After 3 weeks of administration, the tibia bone was excised. Micro high-resolution microfocus x-ray computed tomography showed the formation of primary woven bone in HACP group. Histological sections stained with hematoxylin and eosin were observed under light microscope. In control group, blood clot inside the bone defect with a thin connective tissue surrounding the defect was observed. On the contrary, bone defect area was filled with granulation tissue, blood clot and a great number of osteoblasts in the HACP group. The present results suggested that oral administration of HACP may provide a beneficial effect on bone healing process.

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The histologic hallmark distinguishing desmoplastic ameloblastoma (DA) from conventional ameloblastoma (CA) is its pronounced stromal desmoplasia, and this formed the basis of this investigation. To elucidate the stromal characteristics, localization patterns of oxytalan fibers, type III collagen and BMP family in DA (n=8) was compared with CA (n=24), and periodontal ligament (PL) (n=8). Oxytalan fibers formed apico-occlusal bundles in PL, thick radial bundles around tumor nests in DA, and as scanty fibers in CA. Type III collagen was identified in PL, strongly expressed in DA stroma, but weakly in CA. BMP-2, -3, -4 and -7 expression patterns in tumor epithelium and stroma were more pronounced in DA (including sites of bone formation), than CA. No immunoreactivity for BMP-5 and -6 were detected. Current findings suggest that the stroma in DA is neoplastic and derived from odontogenic ectomesenchyme, and recommends its reclassification as an odontogenic epithelial-ectomesenchymal neoplasm.

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Bone formation steadily declines with age resulting in a loss of bone mass. Reactive oxygen species (ROS) are thought to be major contributors to the aging process. The zinc finger transcription factor, Early Growth Response-1 (Egr-1) is a potential regulator as a transcription factor of many target genes, and plays a role in cell growth, development, and differentiation. However, the effect of ageing on Egr-1 gene expression has not yet been ascertained. To identify which genes have an altered transcription level associated with bone loss by ageing, the pre-osteoblastic cell MC3T3-E1 was treated with H₂O₂, and gene expression profiles analyzed with gene chip technology using the Affymetrix GeneChip analysis system (Mouse; 34,000 genes). The expression of many genes in MC3T3-E1 was altered significantly with Egr-1 being decreased by H₂O₂. The reduction of Egr-1 mRNA levels was successfully confirmed by reversed transcription polymerase chain reaction (RT-PCR) and real-time PCR. Since it has been reported that Egr-1 plays an important role as a transcription factor for growth factor genes which promote cell proliferation and differentiation of preosteoblastic cells, the reduction of Egr-1 gene expression by H₂O₂ may be involved in the decline of bone formation in the ageing process.

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