Squamous cell cancers contain a side population of stem-like cells that are made chemosensitive by ABC transporter blockade.

Cancers are a heterogeneous mix of cells, some of which exhibit cancer stem cell-like characteristics including ATP-dependent drug efflux and elevated tumorigenic potential. To determine whether aerodigestive squamous cell carcinomas (SCCs) contain a subpopulation of cancer stem cell-like cells, we performed Hoechst dye efflux assays using four independent cell lines. Results revealed the presence of a rare, drug effluxing stem cell-like side population (SP) of cells within all cell lines tested (SCC-SP cells). These cells resembled previously characterised epithelial stem cells, and SCC-SP cell abundance was positively correlated with overall cellular density and individual cell quiescence. Serial SCC-SP fractionation and passaging increased their relative abundance within the total cell population. Purified SCC-SP cells also exhibited increased clonogenic potential in secondary cultures and enhanced tumorigenicity in vivo. Despite this, SCC-SP cells remained chemotherapeutically sensitive upon ATP-dependent transporter inhibition. Overall, these findings suggest that the existence of ATP transporter-dependent cancer stem-like cells may be relatively common, particularly within established tumours. Future chemotherapeutic strategies should therefore consider coupling identification and targeting of this potential stem cell-like population with standard treatment methodologies.

Ethanol stimulates apolipoprotein B mRNA editing in the absence of de novo RNA or protein synthesis.

Apolipoprotein B (apoB) mRNA editing involves a site-specific modification of cytidine to form uridine. The reaction is catalyzed in the nucleus by a multi-protein editosome. Rat hepatic editing is regulated during development, metabolically and in response to ethanol. Ethanol stimulated editing in hepatocytes within minutes of exposure. In the present study, we show that ethanol stimulated apoB mRNA synthesis and apoB mRNA editing. Significantly, the proportion of edited apoB mRNA also increased following ethanol treatment of transcription or translation arrested cells. These data suggested that ethanol could regulate editing activity using pre-existing editosomal proteins. In addition, the presence of a suppressor of apoB mRNA editing activity was suggested by the finding that inhibition of mRNA or protein synthesis alone was sufficient to increase the proportion of edited RNA. It is proposed that the level of editing activity observed in hepatocytes may be the end result of positive and negative regulatory proteins.

Mercapturic acids (N-acetylcysteine S-conjugates) as endogenous substrates for the renal organic anion transporter-1.

Mercapturic acids are N-acetyl-L-cysteine S-conjugates that are formed from a range of endogenous and exogenous chemicals. Although the kidney is a major site for elimination of mercapturic acids, the transport mechanisms involved have not been identified. The present study examined whether mercapturic acids are substrates for the renal basolateral organic anion transporter-1 (Oat1) from rat kidney. This carrier mediates uptake of organic anions from the bloodstream in exchange for intracellular alpha-ketoglutarate. Uptake of [(3)H]p-aminohippuric acid (PAH) in Oat1-expressing Xenopus laevis oocytes was strongly inhibited by S-(2,4-dinitrophenyl)-N-acetyl-L-cysteine (DNP-NAC) and by all other mercapturic acids tested, including the endogenous mercapturic acid N-acetyl-leukotriene E(4). Inhibition by the mercapturic acids was competitive, which is consistent with the hypothesis that these compounds are substrates for Oat1. This conclusion was supported by the direct demonstration of saturable [(35)S]DNP-NAC uptake in Oat1-expressing oocytes. [(35)S]DNP-NAC uptake was inhibited by PAH and other mercapturic acids and was stimulated in oocytes preloaded with glutarate. The apparent K(m) value for DNP-NAC uptake was only 2 microM, indicating that this mercapturic acid is a high affinity substrate for Oat1. Together, these data indicate that clearance of endogenous mercapturic acids is an important function of the renal organic anion transporter.

Clara cell secretory protein-expressing cells of the airway neuroepithelial body microenvironment include a label-retaining subset and are critical for epithelial renewal after progenitor cell depletion.

Stem cells with potential to contribute to the re-establishment of the normal bronchiolar epithelium have not been definitively demonstrated. We previously established that neuroepithelial bodies (NEBs) sequester regenerative cells that contribute to bronchiolar regeneration after selective chemical depletion of Clara cells, a major progenitor cell population. Two candidate stem cells were identified on the basis of proliferative potential after chemical ablation: a pollutant-resistant subpopulation of Clara cells that retain their expression of Clara cell secretory protein (CCSP) (variant CCSP-expressing [CE] cells or vCE cells) and calcitonin gene-related peptide (CGRP)-expressing pulmonary neuroendocrine cells (PNECs). In the present study, two populations of label-retaining cells were identified within the NEB: CGRP-expressing cells and a subpopulation of CE cells. To investigate contributions made by CE and CGRP-expressing cells to epithelial renewal, CE cells were ablated through acute administration of ganciclovir to transgenic mice expressing herpes simplex virus thymidine kinase under the regulatory control of the mouse CCSP promoter. CGRP-immunoreactive PNECs proliferated after depletion of CE cells, yet were unable to repopulate CE cell-depleted airways. These results support the notion that vCE cells represent either an airway stem cell or are critical for stem cell maintenance, and suggest that PNECs are not sufficient for epithelial renewal.

Conditional clara cell ablation reveals a self-renewing progenitor function of pulmonary neuroendocrine cells.

The neuroepithelial body (NEB) is a highly dynamic structure that responds to chronic airway injury through hyperplasia of associated pulmonary neuroendocrine (PNE) cells. Although NEB dysplasia is correlated with preneoplastic conditions and PNE cells are thought to serve as a precursor for development of small cell lung carcinoma, mechanisms regulating expansion of the PNE cell population are not well understood. Based on studies performed in animal models, it has been suggested that NEB-associated progenitor cells that are phenotypically distinct from PNE cells contribute to PNE cell hyperplasia. We have previously used a Clara cell-specific toxicant, naphthalene, to induce airway injury in mice and have demonstrated that naphthalene-resistant Clara cells, characterized by their expression of Clara cell secretory protein (CCSP), and PNE cells contribute to airway repair and associated hyperplasia of NEBs. This study was conducted to define the contribution of NEB-associated CCSP-expressing progenitor cells to PNE cell hyperplasia after Clara cell ablation. Transgenic (CCtk) mice were generated in which herpes simplex virus thymidine kinase was expressed within all CCSP-expressing cells of the conducting airway epithelium through the use of transcriptional regulatory elements from the mouse CCSP promoter. Chronic administration of ganciclovir (GCV) to CCtk transgenic mice resulted in selective ablation of CCSP-expressing cells within conducting airways. Proliferation and hyperplasia of PNE cells occurred in the absence of detectable proliferation among any other residual airway epithelial cell populations. These results demonstrate that PNE cells function as a self-renewing progenitor population and that NEB-associated Clara cells are not necessary for PNE cell hyperplasia.

Neuroepithelial bodies of pulmonary airways serve as a reservoir of progenitor cells capable of epithelial regeneration.

Remodeling of the conducting airway epithelium is a common finding in the chronically injured lung and has been associated with increased risk for developing lung cancer. Pulmonary neuroendocrine cells and clusters of these cells termed neuroepithelial bodies (NEBs) play a central role in each of these processes. We previously developed an adult mouse model of airway injury and repair in which epithelial regeneration after naphthalene-induced Clara cell ablation occurred preferentially at airway branch points and gave rise to nascent Clara cells. Continued repair was accompanied by NEB hyperplasia. We now provide the following evidence that the NEB microenvironment serves as a source of airway progenitor cells that contribute to focal regeneration of the airway epithelium: 1) nascent Clara cells and NEBs localize to the same spatial domain; 2) within NEB, both Clara cell secretory protein- and calcitonin gene-related peptide-immunopositive cells are proliferative; 3) the NEB microenvironment of both the steady-state and repairing lung includes cells that are dually immunopositive for Clara cell secretory protein and calcitonin gene-related peptide, which were previously identified only within the embryonic lung; and 4) NEBs harbor variant Clara cells deficient in cytochrome P450 2F2-immunoreactive protein. These data suggest that the NEB microenvironment is a reservoir of pollutant-resistant progenitor cells responsive to depletion of an abundant airway progenitor such as the Clara cell.

Association of gastric lymphoid follicles and Helicobacter pylori infection.

Lymphoid tissue is normally absent in the gastric mucosa; however, lymphoid follicles are very frequently noted in Helicobacter-associated gastritis. We reviewed 237 cases of chronic gastritis with lymphoid follicles. Out of this 227 cases (95.8%) were found to have H. pylori infection. The significance of this finding and its possible relationship to primary gastric lymphoma are discussed.

Recurrent bilateral theca lutein cysts in association with normal pregnancy.

We describe a case of a 28-year-old Saudi patient, gravida 6, para 5, at 14 weeks' gestation, who had recurrent bilateral theca lutein cysts during her last three pregnancies. The cysts were treated surgically during her fourth pregnancy because of acute abdomen at 20 weeks' gestation. Ovarian biopsy confirmed the diagnosis of theca lutein cysts and her pregnancy continued until term. In the last two pregnancies, the theca lutein cysts were managed conservatively by serial ultrasound examination and they resolved spontaneously. There was no history of molar pregnancy or use of ovulation-inducing drugs. The possibility that there was increased sensitivity of the ovarian tissue to human chorionic gonadotropin is discussed.

Pleuropulmonary blastoma of the lung presenting as posterior mediastinal mass: a case report.

Pulmonary blastoma is a rare primary neoplasm of the lung. A case of a 2 1/2-year-old girl with a rapidly progressing pleuropulmonary blastoma clinically presenting as a posterior mediastinal mass is discussed.

Steroid-responsive Rosai-Dorfman disease.

Nodular skin lesions on the lateral aspects of the legs of a female child were first noticed at the age of 6 days. A biopsy of the lesions was done at the age of 6 months when the child had also developed cervical and inguinal lymphadenopathy and angiomatous lesions on the face. The diagnosis of Rosai-Dorfman disease (RDD; also known as sinus histiocytosis with massive lymphadenopathy, SHML) was made. Increasing respiratory obstruction by lymphoid tissue prompted a 2-week trial with oral prednisolone. A dramatic response occurred, with complete resolution of all clinical findings within 5 days, but with recurrence of lymphadenopathy 6 weeks after stopping with medication. Further observations over the next 3 years established a consistent response to prednisolone and a pattern of steroid dependence.

Intrathoracic extramedullary hematopoietic tumor in hemoglobin C disease.

A case of intrathoracic extramedullary hematopoietic tumor associated with hemoglobin C disease is reported in a 27-year-old Bangladeshi man. The patient's initial complaints were generalized weakness, weight loss, and left upper abdominal pain. Hospital workup revealed a solitary intrathoracic mass in the posterior mediastinum, which was suspected to be a lymphoma based on fine-needle aspiration. The mass was excised and proved to be an extramedullary hematopoietic tumor. The problem of differential diagnosis is discussed.

Basement membrane thickening in the placentae from diabetic women.

A light microscopy study was carried out on 48 placentae. Seventeen placentae were obtained from non-diabetic mothers while the other 31 placentae were from both women with controlled diabetes and women who had an abnormality of the glucose tolerance test. All the women delivered at 38-40 weeks of gestation. Placentae from diabetic patients showed immaturity of the villi, hypertrophy of the capillaries and thickening of the basement membrane of the trophoblastic villi (3.2 +/- 0.35 microns) and the amniotic membrane (1.8 +/- 0.3 microns). Focal fibrinoid necrosis, an increase in the number of Hofbauer cells and dilatation of villi capillaries were also commonly observed in placentae from diabetic mothers, and the normal cuboidal cells lining the amniotic membrane tended to become tall columnar (17.6 +/- 6.3 microns) with distally located nuclei. Similar findings were observed in patients who had a potentially abnormal glucose tolerance test, which suggests the possibility of primary lesion in origin. Therefore, control of hyperglycemia may only partially prevent the development of placental abnormalities.