Is withdrawal of antiresorptive agents necessary before and after tooth extraction? A systematic review.

OBJECTIVES: The need for prevention and management of medication-related osteonecrosis of the jaw (MRONJ) has increased with the growing number of patients using antiresorptive agents. The scope of this systematic review (SR) was to determine whether the withdrawal of antiresorptive agents is necessary for tooth extractions in patients receiving each of the antiresorptive medications. MATERIALS AND METHODS: The searches were performed using the MEDLINE databases. We selected SRs, randomized controlled trials (RCTs), prospective and retrospective non-randomized clinical (observational) studies, and case reports/case series in this order of preference. RESULTS: We included one SR, one RCT, five observational studies, and three case reports. Meta-analyses were not conducted because the RCT had an extremely small sample size and the observational studies had different definitions of intervention and comparison that could not be integrated across studies. In this SR, no studies showed a benefit (i.e., a reduction in the incidence of osteonecrosis of the jaw) of short-term withdrawal of antiresorptive agents for tooth extraction. Additionally, no studies examined the harm (i.e., an increase in femoral and vertebral fractures and skeletal-related events during bone metastasis) of withdrawal for tooth extraction. CONCLUSIONS: We were unable to determine whether withdrawal before and after tooth extraction is necessary with a high certainty of evidence. Future systematic reviews including RCTs with larger samples are expected to provide such evidence. CLINICAL RELEVANCE: This systematic review provides evidence-based information for multidisciplinary collaborations related to patients receiving antiresorptive agents.

Efficacy of texture analysis of ultrasonographic images in the differentiation of metastatic and non-metastatic cervical lymph nodes in patients with squamous cell carcinoma of the tongue.

OBJECTIVE: We investigated the efficacy of using texture analysis of ultrasonographic images of the cervical lymph nodes of patients with squamous cell carcinoma of the tongue to differentiate between metastatic and non-metastatic lymph nodes. STUDY DESIGN: We analyzed 32 metastatic and 28 non-metastatic lymph nodes diagnosed by histopathologic examination on presurgical US images. Using the LIFEx texture analysis program, we extracted 36 texture features from the images and calculated the statistical significance of differences in texture features between metastatic and non-metastatic lymph nodes using the t test. To assess the diagnostic ability of the significantly different texture features to discriminate between metastatic and non-metastatic nodes, we performed receiver operating characteristic curve analysis and calculated the area under the curve. We set the cutoff points that maximized the sensitivity and specificity for each curve according to the Youden J statistic. RESULTS: We found that 20 texture features significantly differed between metastatic and non-metastatic lymph nodes. Among them, only the gray-level run length matrix feature of run length non-uniformity and the gray-level zone length matrix features of gray-level non-uniformity and zone length non-uniformity showed an excellent ability to discriminate between metastatic and non-metastatic lymph nodes as indicated by the area under the curve and the sum of sensitivity and specificity. CONCLUSIONS: Analysis of the texture features of run length non-uniformity, gray-level non-uniformity, and zone length non-uniformity values allows for differentiation between metastatic and non-metastatic lymph nodes, with the use of gray-level non-uniformity appearing to be the best means of predicting metastatic lymph nodes.

Hypo-osmolarity induces apoptosis resistance via TRPV2-mediated AKT-Bcl-2 pathway.

In cirrhosis, several molecular alterations such as resistance to apoptosis could accelerate carcinogenesis. Recently, mechanotransduction has been attracting attention as one of the causes of these disturbances. In patients with cirrhosis, the serum sodium levels progressively decrease in the later stage of cirrhosis, and hyponatremia leads to serum hypo-osmolality. Since serum sodium levels in patients with cirrhosis with liver cancer are inversely related to cancer's number, size, stage, and cumulative survival, we hypothesized that hypo-osmolality-induced mechanotransduction under cirrhotic conditions might contribute to oncogenesis and/or progression of hepatocellular carcinoma (HCC). In this study, we adjusted osmosis of culture medium by changing the sodium chloride concentration and investigated the influence of hypotonic conditions on the apoptosis resistance of an HCC cell line, HepG2, using a serum-deprivation-induced apoptosis model. By culturing the cells in a serum-free medium, the levels of an antiapoptotic protein Bcl-2 were downregulated. In contrast, the hypotonic conditions caused apoptosis resistance by upregulation of Bcl-2. Next, we examined which pathway was involved in the apoptosis resistance. Hypotonic conditions enhanced AKT signaling, and constitutive activation of AKT in HepG2 cells led to upregulation of Bcl-2. Moreover, we revealed that the enhancement of AKT signaling was caused by intracellular calcium influx via a mechanosensor, TRPV2. Our findings suggested that hyponatremia-induced serum hypotonic in patients with cirrhosis promoted the progression of hepatocellular carcinoma.NEW & NOTEWORTHY Our study first revealed that hypo-osmolarity-induced mechanotransduction enhanced calcium-mediated AKT signaling via TRPV2 activation, resulting in contributing to apoptosis resistance. The finding indicates a possible view that liver cirrhosis-induced hyponatremia promotes hepatocellular carcinogenesis.

Quantitative bone single photon emission computed tomography analysis of the effects of duration of bisphosphonate administration on the parietal bone.

Effects of long-term bisphosphonate (BP) administration on the metabolism of healthy bone and the concomitant changes in imaging are unclear. Hence, we aimed to retrospectively investigate the effects of long-term BP administration on the intact parietal bone using the standardised uptake value (SUV) derived from single photon emission computed tomography (SPECT). We enrolled 29 patients who had odontogenic infection, osteoporosis, bone metastasis cancer, or rheumatoid arthritis, and classified them into BP-naïve: A (14 patients) and BP-treated: B, < 4 years (7 patients) and C, ≥ 4 years (8 patients) groups. We measured the maximum bilateral SUV (SUVmax) of the parietal bone using quantitative bone SPECT software. There were significant differences in the duration of BP administration and SUVmax of the parietal bone among the diseases (P < 0.0001 and P = 0.0086, respectively). There was a positive correlation between the duration of BP administration and SUVmax of the parietal bone (rs = 0.65, P = 0.0002). The SUVmax was significantly different between A and B (P = 0.02) and between A and C (P = 0.0024) groups. This is the first report on the correlation between long-term BP administration and the SUVmax of the parietal bone using the quantitative bone SPECT analysis.

Prevalence of and risk factors for postoperative hemorrhage after lower third molar extraction on warfarin therapy: a multicenter retrospective study in Japan.

Postoperative hemorrhage after tooth extraction is a critical and clinically important issue for clinicians and patients receiving anticoagulants. The purpose of the present study was to investigate the prevalence of and risk factors for postoperative hemorrhage after lower third molar extraction in Japanese patients receiving warfarin therapy. A total of 142 patients who underwent lower third molar extraction between January 2010 and December 2016 were included, and their medical records were retrospectively reviewed. The prevalence of and risk factors for postoperative hemorrhage were investigated. The prevalence of postoperative hemorrhage after lower third molar extraction was significantly higher in patients receiving warfarin than in healthy subjects (21.8% vs 0.7%, P < 0.001). The cutoff value for PT-INR was 2.11 based on a receiver-operating characteristic analysis. A multivariate analysis indicated that an elevated PT-INR value [hazard ratio (HR) 3.798, 95% confidence interval (CI) 1.400-10.467, P < 0.01], preoperative antibiotic administration (HR 4.434, 95% CI 1.591-14.775, P < 0.01), difficulties with intraoperative hemostasis (HR 16.298, 95% CI 2.986-110.677, P < 0.01), and higher serum creatinine levels (HR 7.465, 95% CI 1.616-39.576, P < 0.05) are significant predictors of postoperative hemorrhage after lower third molar extraction. Multivariate correlations were observed between risk factors including an elevated PT-INR value, preoperative antibiotic administration, and higher serum creatinine levels, and postoperative hemorrhage after lower third molar extraction in patients receiving warfarin therapy. Clinicians need to consider these risk factors for postoperative hemorrhage after the lower third molar extraction and monitor PT-INR in patients receiving warfarin therapy.

An Adult Mouse Thyroid Side Population Cell Line that Exhibits Enriched Epithelial-Mesenchymal Transition.

BACKGROUND: Studies of thyroid stem/progenitor cells have been hampered due to the small organ size and lack of tissue, which limits the yield of these cells. A continuous source that allows the study and characterization of thyroid stem/progenitor cells is desired to push the field forward. METHOD: A cell line was established from Hoechst-resistant side population cells derived from mouse thyroid that were previously shown to contain stem/progenitor-like cells. Characterization of these cells were carried out by using in vitro two- and three-dimensional cultures and in vivo reconstitution of mice after orthotopic or intravenous injection, in conjunction with quantitative reverse transcription polymerase chain reaction, Western blotting, immunohisto(cyto)chemistry/immunofluorescence, and RNA seq analysis. RESULTS: These cells were named SPTL (side population cell-derived thyroid cell line). Under low serum culturing conditions, SPTL cells expressed the thyroid differentiation marker NKX2-1, a transcription factor critical for thyroid differentiation and function, while no expression of other thyroid differentiation marker genes were observed. SPTL cells formed follicle-like structures in Matrigel® cultures, which did not express thyroid differentiation marker genes. In mouse models of orthotopic and intravenous injection, the latter following partial thyroidectomy, a few SPTL cells were found in part of the follicles, most of which expressed NKX2-1. SPTL cells highly express genes involved in epithelial-mesenchymal transition, as demonstrated by RNA seq analysis, and exhibit a gene-expression pattern similar to anaplastic thyroid carcinoma. CONCLUSION: These results demonstrate that SPTL cells have the capacity to differentiate into thyroid to a limited degree. SPTL cells may provide an excellent tool to study stem cells, including cancer stem cells of the thyroid.

Unusual maxillary osteoblastic and osteolytic lesions presenting as an initial manifestation of childhood acute myeloid leukemia: A case report.

Changes in facial bones may represent a manifestation of systemic disease. Dentists play an important role in the early detection of these manifestations of complex systemic diseases. A case of unusual maxillary mixed (osteoblastic and osteolytic) lesions as an initial manifestation of childhood acute myeloid leukemia (AML) is presented. A 12-year-old male patient was referred to the Department of Oral Medicine complaining of severe swelling in the right buccal region. 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) showed enhanced FDG uptake in the right maxillary sinus. In addition, PET maximum intensity projection image showed diffused FDG uptake in the entire bone marrow. Bone marrow aspiration was performed on the lumbar vertebra, and fluorescence in situ hybridization (FISH) demonstrated AML. The patient was diagnosed with AML (M5a) and treated with chemotherapy by the pediatric department. Six months later, the patient achieved complete remission. After chemotherapy, the disappearance of the osteoblastic and osteolytic lesion and 18F-FDG accumulation were confirmed by PET/CT. Dentists should be familiar with oral manifestations of leukemia because early detection of oral lesions would increase the life span of the patients and reduce the severity of complications.

Differences in sequential posttreatment salivary IL-6 levels between patients with and patients without locoregional recurrences of oral squamous cell carcinoma: Part III of a cohort study.

OBJECTIVE: Sequential postoperative salivary interleukin-6 (IL-6) concentrations were examined in patients with oral squamous cell carcinoma (OSCC) who had early or late locoregional recurrences or those who did not. STUDY DESIGN: Twenty-seven consecutive patients with OSCC were originally included in the study. All patients underwent radical surgery. Four saliva samples were collected before (periods I and II) and after (periods III and IV) surgery, and IL-6 concentrations were measured. RESULTS: Although postoperative (period III: at the time of discharge) salivary IL-6 level was significantly higher in patients with early locoregional recurrence (P = .02) than in those without, no such relationships were observed for preoperative IL-6 concentrations (periods I and II). Postoperative (period IV: 24 months after surgery) IL-6 level was significantly higher in patients with late locoregional recurrence (P = .03) than in those without, but no such relationships were observed for IL-6 concentrations in periods I, II, and III. CONCLUSIONS: Sequential postoperative salivary IL-6 concentration may be a useful marker for diagnosis of early and late locoregional recurrence in OSCC.

Expression of stanniocalcin 1 in thyroid side population cells and thyroid cancer cells.

BACKGROUND: Mouse thyroid side population (SP) cells consist of a minor population of mouse thyroid cells that may have multipotent thyroid stem cell characteristics. However the nature of thyroid SP cells remains elusive, particularly in relation to thyroid cancer. Stanniocalcin (STC) 1 and 2 are secreted glycoproteins known to regulate serum calcium and phosphate homeostasis. In recent years, the relationship of STC1/2 expression to cancer has been described in various tissues. METHOD: Microarray analysis was carried out to determine genes up- and down-regulated in thyroid SP cells as compared with non-SP cells. Among genes up-regulated, stanniocalcin 1 (STC1) was chosen for study because of its expression in various thyroid cells by Western blotting and immunohistochemistry. RESULTS: Gene expression analysis revealed that genes known to be highly expressed in cancer cells and/or involved in cancer invasion/metastasis were markedly up-regulated in SP cells from both intact as well as partial thyroidectomized thyroids. Among these genes, expression of STC1 was found in five human thyroid carcinoma-derived cell lines as revealed by analysis of mRNA and protein, and its expression was inversely correlated with the differentiation status of the cells. Immunohistochemical analysis demonstrated higher expression of STC1 in the thyroid tumor cell line and thyroid tumor tissues from humans and mice. CONCLUSION: These results suggest that SP cells contain a population of cells that express genes also highly expressed in cancer cells including Stc1, which warrants further study on the role of SP cells and/or STC1 expression in thyroid cancer.

Advantage of FMISO-PET over FDG-PET for predicting histological response to preoperative chemotherapy in patients with oral squamous cell carcinoma.

PURPOSE: Hypoxia, a prognostic factor in many types of cancer, can be detected by (18)F-fluoromisonidazole (FMISO) positron emission tomography (PET). It is unclear whether hypoxia reflects the response to chemotherapy in patients with oral squamous cell carcinoma (OSCC). The correlations of FMISO-PET and FDG-PET with histological response to preoperative chemotherapy were therefore assessed in patients with OSCC. METHODS: This study enrolled 22 patients with OSCC undergoing preoperative chemotherapy. The T-stages were T2 in 6 patients, T3 in 3, and T4a in 13, and the N-stages were N0 in 14 patients, N1 in 3, and N2 in 5. Each patient was evaluated by both FMISO-PET and FDG-PET before surgery, and the maximum standardized uptake value (SUVmax) of FDG- and FMISO-PET and tumor-muscle ratio (TMR) of FMISO-PET were measured. The threshold for the hypoxic volume based on TMR was set at 1.25. The histological response to preoperative chemotherapy was evaluated using operative materials. RESULTS: FMISO-PET and FDG-PET detected uptake by primary OSCCs in 15 (68%) and 21 (95%) patients, respectively, and median SUVmaxs of FMISO- and FDG-PET in the primary site were 2.0 (range, 1.3-3.5) and 16.0 (range, 1.0-32.2), respectively. The median of FMISO TMR was 1.5 (range, 0.99-2.96). There were five cases whose FMISO TMR was less than 1.25. Histological evaluation showed good response to preoperative chemotherapy in 7 patients (32%) and poor response in 15 (68%). Good response was significantly more prevalent in patients with negative than positive FMISO uptake (P < 0.001) and without the hypoxic area evaluated by FMISO-PET TMR (P = 0.04), whereas FDG uptake was not significantly correlated with response to chemotherapy response. Multivariate logistic regression analysis showed that FMISO uptake was an independent significant predictor of response to preoperative chemotherapy (P = 0.03, odds ratio = 0.06, 95% confidence interval = 0.004-0.759). CONCLUSIONS: An advantage of FMISO-PET over FDG-PET for predicting histological response to preoperative chemotherapy in patients with OSCC was observed.

Serine 727 phosphorylation of STAT3: an early change in mouse hepatocarcinogenesis induced by neonatal treatment with diethylnitrosamine.

STAT3 activation is involved in development and progression of hepatocellular carcinoma (HCC). We investigated STAT3 activation during hepatocarcinogenesis induced by neonatal diethylnitrosamine (DEN) treatment in mice. Nuclear accumulation and phosphorylation of STAT3 were detected in altered hepatocyte foci in the early stages as well as adenomas and HCCs in the late stages. Although total STAT3 levels were the same between the hepatic lesions and normal livers, S727-phosphorylated STAT3 was enhanced in adenomas and HCCs, whereas Y705-phosphorylated STAT3 was detected mainly in HCCs. In mouse HCC cell lines, although both S727 and Y705 remained un- or hypophosphorylated under serum-free conditions, fetal bovine serum (FBS) induced strong S727/weak Y705 phosphorylation, STAT3 nuclear accumulation and cell proliferation, whereas IL-6 treatment without FBS caused Y705 phosphorylation without S727 phosphorylation, STAT3 nuclear accumulation or cell proliferation. When HCCs were simultaneously treated with FBS/IL-6, selective suppression of S727 phosphorylation by an MEK inhibitor prevented STAT3 nuclear accumulation and cell proliferation. Furthermore, an S727 phosphorylation-deficient STAT3 mutant (S727A) had a diminished capacity to accumulate in the nucleus when compared with wild-type (WT) or the phosphorylation-mimic mutant (S727D) following treatment with FBS/IL-6. After treatment with FBS/IL-6, the cells expressing the S727A mutant proliferated more slowly than those expressing WT or S727D mutant. In contrast, suppression of Y705 phosphorylation by a JAK inhibitor in the FBS/IL-6 treated cells did not affect STAT3 nuclear accumulation or cell proliferation. Taken together, these data demonstrate that STAT3 activation, mainly through S727 phosphorylation, contributes to the DEN-induced hepatocarcinogenesis at the earliest stages.

Stem cell antigen 1-positive mesenchymal cells are the origin of follicular cells during thyroid regeneration.

Many tissues are thought to contain adult stem/progenitor cells that are responsible for repair of the tissue where they reside upon damage and/or carcinogenesis, conditions when cellular homeostasis becomes uncontrolled. While the presence of stem/progenitor cells of the thyroid has been suggested, how these cells contribute to thyroid regeneration remains unclear. Here we show the origin of thyroid follicular cells and the process of their maturation to become follicular cells during regeneration. By using ß-galactosidase (ß-gal) reporter mice in conjunction with partial thyroidectomy as a model for thyroid regeneration, and bromodeoxyuridine (BrdU) long label-retaining cell analysis, we demonstrated that stem cell antigen 1 (Sca1) and BrdU-positive, but ß-gal and NKX2-1 negative cells were found in the non-follicular mesenchymal area 7 days after partial thyroidectomy. They temporarily co-expressed cytokeratin 14, and were observed in part of follicles by day 35 post-partial thyroidectomy. Sca1, BrdU, ß-gal, and NKX2-1-positive cells were found 120 days post-partial thyroidectomy. These results suggested that Sca1 and BrdU positive cells may participate in the formation of new thyroid follicles after partial thyroidectomy. The process of thyroid follicular cell regeneration was recapitulated in ex vivo thyroid slice collagen gel culture studies. These studies will facilitate research on thyroid stem/progenitor cells and their roles in thyroid diseases, particularly thyroid carcinomas.

Unique Properties of Hepatocarcinogenesis-Resistant DRH Rat Hepatocytes Linked or Not Linked to the Drh1 Locus on Rat Chromosome 1.

Hepatocarcinogenesis-resistant DRH rats exhibit few and small preneoplastic hepatocytic lesions during hepatocarcinogenesis, of which traits have been assigned to two major chromosomal regions, Drh1 and Drh2. In this study, hepatocytes from DRH.F344-Drh1, a congenic strain in which the Drh1 chromosomal region was replaced with that of F344 rats, were compared to hepatocytes from Donryu (original strain), DRH, and F344 rats. Although DRH hepatocytes exhibited low proliferation and p38 dephosphorylation after lead nitrate (LN) treatment despite cytokine and Cox2 activation, DRH.F344-Drh1 hepatocytes exhibited high responses, as did Donryu and F344 hepatocytes. Moreover, although DRH hepatocytes were resistant to hepatotoxins, DRH.F344-Drh1 hepatocytes were as sensitive to hepatotoxins as Donryu and F344 hepatocytes. However, DRH.F344-Drh1 hepatocytes like DRH hepatocytes proliferated at lower rates in vitro and contained smaller nuclei than Donryu and F344 hepatocytes. Thus, low responses to LN and resistance to hepatotoxins in DRH hepatocytes were linked to the Drh1 locus, while low proliferation in vitro and small nuclear size were not linked to the Drh1 locus.

Effects of bone marrow and hepatocyte transplantation on liver injury.

BACKGROUND: The therapeutic effects of bone marrow and hepatocyte transplantation were investigated regarding the treatment of retrorsine-partial hepatectomy-induced liver injury. METHODS: Analbuminemic F344alb rats were given two doses of retrorsine 2 wk apart, followed 4 wk later by transplantation with F344 rat bone marrow cells or hepatocytes immediately after a two-thirds hepatectomy. The survival rate, liver regeneration rate, liver functions, albumin-positive hepatocytes, and normal albumin gene sequences in the liver and serum albumin levels were investigated in the recipients. RESULTS: Although 65% retrorsine/partial hepatectomy-treated F344alb died between 1 and 11 d after the partial hepatectomy, only 27.5% of the animals died following bone marrow transplantation, and 50% with hepatocyte transplantation. Both bone marrow and hepatocyte transplantation ameliorated acute liver injury after a partial hepatectomy. Bone marrow transplantation yielded a very small increase in the number of albumin-positive hepatocytes in the liver, while hepatocyte transplantation resulted in massive replacement of the liver tissues by the donor hepatocytes associated with an elevation of serum albumin after an extended time. CONCLUSIONS: Both bone marrow and hepatocyte transplantation could prevent acute hepatic injury, conceivably due to a paracrine mechanism.

Oncostatin M regulates secretoglobin 3A1 and 3A2 expression in a bidirectional manner.

Secretoglobin (SCGB) 3A1 and 3A2 are members of the small molecular weight secretoglobin gene superfamily. SCGB3A1 is a tumor suppressor gene, whereas SCGB3A2 has anti-inflammatory properties. Both genes are mainly expressed in the lung and trachea in mice. Whether the expression and/or function of these two genes are related is not known. Here we show that the expression of SCGB3A1 and SCGB3A2 are bidirectionally regulated by oncostatin M (OSM) when examined in a mouse transformed Clara cell line (mtCC); SCGB3A1 is up-regulated by OSM, while SCGB3A2 is down-regulated in a time- and dose-dependent manner. OSM-activated STAT3/5, through binding to the STAT-binding element located at -201 to -209 bp in the mouse Scgb3a1 gene promoter, and the extracellular signal-regulated kinase (ERK)- and p38-mitogen-activated protein kinase (MAPK) pathways are responsible for the OSM-induced up-regulation of SCGB3A1 expression. On the other hand, the -113 to -273 bp region in the Scgb3a2 promoter appears to be responsible for the OSM induced down-regulation of the gene. No significant differences in the levels or patterns of specific DNA-binding proteins were found in the -113 to -273 bp region as determined by electrophoretic mobility shift assays. Neither the ERK- nor p38-MAPK pathways were involved in the OSM-induced reduction of Scgb3a2 promoter activity. These results suggest that OSM-induced suppression of SCGB3A2 expression is an indirect effect of OSM. Expression of the Clara cell marker, CYP2F2, was markedly decreased upon OSM treatment in parallel with the decrease of SCGB3A2 expression in mtCC cells. The differential regulation of Scgb3a1 and Scgb3a2 gene expression by OSM may explain the unique functions of these genes in the lung.

Low p38 MAPK and JNK activation in cultured hepatocytes of DRH rats; a strain highly resistant to hepatocarcinogenesis.

DRH rats are a hepatocarcinogenesis-resistant strain isolated from hepatocarcinogenesis-sensitive Donryu rats, and the liver of DRH shows less histological damage and fewer/smaller neoplastic hepatic lesions by the treatment with hepatocarcinogens. To investigate the mechanism of the resistance, the properties of hepatocytes of DRH and Donryu were compared. In primary culture, DRH hepatocytes exhibited higher proliferation and less apoptosis than Donryu hepatocytes in the presence of EGF and insulin. However, such difference was not correlated to the degree of DNA damage associated with cell culture or cell cycle checkpoint function. Although the mitogen-activated protein kinases [EGF receptor (EGFR) and extracellular signal regulating kinases (ERK1/2)] were activated to the same degree, the stress-activated protein kinases [p38 mitogen-activated protein kinase (p38) and c-jun N-terminal kinase (JNK)] were activated to a lesser degree in the DRH hepatocytes. Treatment with 2-acetylaminofluorene (2-AAF) in vivo also resulted in less JNK and p38 activation in the DRH livers. Furthermore, apoptosis signal-regulating kinase 1 (ASK1) was inhibited by the lysate from the DRH but not by the Donryu hepatocytes. The low activation of the stress-activated protein kinases may be linked to the resistance to cellular stress, which may underlie the hepatocarcinogenesis-resistance in DRH rats.

Low selection of preneoplastic hepatocytes after treatment with the 2-acetylaminofluorene diet-partial hepatectomy regimen in the liver of hepatocarcinogenesis-resistant DRH strain rats.

In hepatocarcinogenesis-resistant DRH rats, preneoplastic hepatocytic lesions are smaller than those of usual rats during carcinogenesis. When preneoplastic hepatocytes from DRH and Donryu (original strain of DRH) were reciprocally transplanted into the livers of DRH and Donryu treated with 2-acetylaminofluorene (2-AAF) diet/two-thirds hepatectomy (PH), the Donryu cells formed small colonies within the DRH liver, whereas the DRH cells formed large colonies within the Donryu liver. The DRH liver showed less degree of oval cell proliferation after treatment with 2-AAF and PH, and DRH hepatocytes were more resistant to the growth-inhibitory effect of 2-AAF after PH. Furthermore, DRH hepatocytes were generally resistant to cytotoxicity of hepatotoxins. The tissue environment of the DRH liver, therefore, is less effective for selective growth of preneoplastic hepatocytes during the carcinogen treatment, which is probably a major cause of the hepatocarcinogenesis-resistance in DRH rats.

Hypoxia-independent overexpression of hypoxia-inducible factor 1alpha as an early change in mouse hepatocarcinogenesis.

Hypoxia-inducible factor 1 (HIF-1) is involved in tumor progression/metastasis and activated in various cancers. Here we show that HIF-1alpha, which plays a major role in HIF-1 activation, is overexpressed in preneoplastic hepatocytic lesions from a very early stage during hepatocarcinogenesis in mice and man. Transcriptional targets of HIF-1, such as vascular endothelial growth factor, glut-1, c-met, and insulin-like growth factor II (IGF-II), were also overexpressed in mouse lesions. Oxygen tension within the lesions was not different from that of the normal hepatic tissues, indicating that HIF-1alpha expression was independent of hypoxia. On the other hand, Akt, the pathway of which can up-regulate HIF-1alpha expression, was activated in the mouse lesions, whereas HIF-1alpha was markedly down-regulated in the mouse hepatocellular carcinoma (HCC) cell lines after treatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, indicating that HIF-1alpha expression is dependent on PI3K/Akt signaling. Conversely, HIF-1alpha knockdown by short interfering RNA in the HCC cell line resulted in decreased expression of activated Akt together with the HIF-1 target genes, indicating that Akt activation is reversely dependent on HIF-1 activation. Treating the HCC cells with IGF-II or epidermal growth factor (EGF) up-regulated both phospho-Akt and HIF-1alpha, whereas inhibition of IGF-II or EGF signaling down-regulated them both, suggesting that IGF-II and EGF can, at least in part, mediate the activation of Akt and HIF-1alpha. However, Akt was not activated by IGF-II or EGF in the HIF-1alpha knockdown cells, indicating that expression of the HIF-1 target genes is necessary for the Akt activation. These findings suggest that the reciprocal activation of PI3K/Akt signaling and HIF-1alpha may be important in the progression of hepatocarcinogenesis.

F344 rat liver nonparenchymal cell transplantation can increase the number of albumin-positive hepatocytes in the liver following hematopoietic reconstitution in irradiated analbuminemic rats.

The adult liver contains hematopoietic stem cells that can reconstitute the bone marrow. We tested whether bone marrow cells (BMCs) derived from liver nonparenchymal cells (LNPCs) can increase the number of hepatocytes within livers. LNPCs from Fischer 344 rats (F344) were infused into the penile veins of F344 congenic Nagase's analbuminenic rats (F344alb) immediately after whole-body irradiation, and the recipients were sacrificed 8 weeks later. Eleven of 15 (73.3%) F344alb that received the LNPC transplantation after irradiation survived, while only 1 of 8 (12.5%) F344alb that received irradiation alone was alive after 8 weeks. Normal albumin gene sequences were detected by PCR in BMCs of the recipient F344alb that received LNPC transplantation after irradiation, indicating that F344alb bone marrow was reconstituted by F344 LNPCs. Although single or pairs of albumin-positive (Alb+) hepatocytes were seen in the liver of untreated F344alb and those with irradiation or LNPC transplantation alone, clusters consisting of >3 Alb+ hepatocytes were detected in the livers of F344alb with the LNPC or BMC transplantation after irradiation together with single or double Alb+ cells. Normal albumin gene sequences were detected by PCR in the DNA isolated from such Alb+ hepatocyte clusters microdissected from the immunostained sections. The data indicate that BMCs derived from F344 LNPCs could increase the number Alb+ hepatocytes within the F344alb liver.

Different growth capacity between infant and adult mouse hepatocytes in vitro correlates to the cyclin D1 level without relation to oxidative DNA damage.

BACKGROUND: Proliferating capacity of hepatocytes is rapidly decreased during growth into maturity, but its exact reason(s) are not well known. METHODS: Hepatocytes isolated from infant (10-14 days old) and adult (10-13 months old) B6C3F1 mice were cultivated in the medium containing epidermal growth factor and insulin. Proliferative capacity, apoptosis, morphological changes, cell cycle proteins and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were compared between the two hepatocyte populations. RESULTS: Although adult hepatocytes rapidly underwent cellular crisis characterized by extended morphology and multiple nuclei without proliferation, infant hepatocytes could proliferate with less crisis. Cyclin D1 was much more abundant in the infant than adult cells, but there was no difference according to the expression of cdk4, cdk2, cyclin E and cdk inhibitors (p16(Ink4) (p16), p21(Cip1/Waf1) (p21) and p27(Kip1) (p27)). 8-OHdG became high soon after cultivation, while it rapidly went down after day 2 both in the infant and adult cells. CONCLUSIONS: The high growth capacity of infant hepatocytes in vitro was dependent on the cyclin D1 level, but there was no relation to 8-OHdG.