H-ras-transformed NRK-52E renal epithelial cells have altered growth, morphology, and cytoskeletal structure that correlates with renal cell carcinoma in vivo

Summary We studied the effect of the ras oncogene on the growth kinetics, morphology, cytoskeletal structure, and tumorigenicity of the widely used NRK-52E rat kidney epithelial cell line and two H-ras oncogene-transformed cell lines, H/1.2-NRK-52E (H/1.2) and H/6.1-NRK-52E (H/6.1). Population doubling times of NRK-52E, H/1.2, and H/6.1 cells were 28, 26, and 24 h, respectively, with the transformed cells reaching higher saturation densities than the parent cells. NRK-52E cells had typical epithelial morphology with growth in colonies. H/1.2 and H/6.1 cell colonies were more closely packed, highly condensed, and had increased plasma membrane ruffling compared to parent cell colonies. NRK-52E cells showed microfilament, microtubule, and intermediate filament networks typical of epithelial cells, while H/1.2 and H/6.1 cells showed altered cytoskeleton architecture, with decreased stress fibers and increased microtubule and intermediate filament staining at the microtubule organizing center. H/1.2 and H/6.1 cells proliferated in an in vitro soft agar transformation assay, indicating anchorage-independence, and rapidly formed tumors in vivo with characteristics of renal cell carcinoma, including mixed populations of sarcomatoid, granular, and clear cells, H/6.1 cells consistently showed more extensive alterations of growth kinetics, morphology, and cytoskeleton than H/1.2 cells, and formed tumors of a more aggressive phenotype. These data suggest that analysis of renal cell characteristics in vitro may have potential in predicting tumor behavior in vivo, and significantly contribute to the utility of these cell lines as in vitro models for examining renal epithelial cell biology and the role of the ras proto-oncogene in signal transduction involving the cytoskeleton.     

Conversion of premalignant human cells to tumorigenic cells by methylmethane sulfonate and methylnitronitrosoguanidine

Nine human tumor cell lines derived from both epithelial and mesenchymal tumors exhibited either an anchorage-independent growth non-tumorigenic phenotype or an anchorage-independent tumorigenic phenotype. Transformed epithelial cell lines with the non-tumorigenic phenotype could be converted to a progressively growing tumor phenotype following treatment with either methylmethane sulfonate (MMS) or N-methyl-N-nitro-N-nitrosoguanidine (MNNG). In contrast, sarcoma derived cell lines with a non-tumorigenic phenotype could be converted to a progressively growing tumor phenotype only with MNNG. SV40 immortalized HET-1A non-tumorigenic phenotype cells could be converted to a progressively growing tumorigenic phenotype, infrequently, when treated with MNNG, but not MMS. Progressively growing tumors produced by either MMS or MNNG treated non-tumorigenic phenotypes exhibited metastatic potential in nude mice. Chemically treated HET-1A cells acquired the ability to produce tumor in mice but the tumor did not exhibit metastatic potential. In contrast, populations of tumorigenic cells were not rendered more biologically aggressive after treatment with either MMS or MNNG; i.e., the latency period for tumor development was not accelerated and the tumors did not exhibit metastatic potential. These results suggest that the biological effects of MMS and MNNG on non-tumorigenic, tumorigenic and immortalized cell lines are phenotype specific.Abbreviations AIG anchorage-independent growth - DMSO dimethyl sulfoxide - FBS fetal bovine serum - GM growth medium - MEM Eagle's minimum essential medium - MMS methylmethane sulfonate - MNNG N-Methyl-N-Nitro-N-Nitrosoguanidine - PDL population doubling - SCC squamous cell carcinoma     

The beneficial role of extracellular reactive oxygen species in apoptosis-induced compensatory proliferation

Apoptosis-induced proliferation (AiP) maintains tissue homeostasis following massive stress-induced cell death. During this phenomenon, dying cells induce proliferation of the surviving cells to compensate for the tissue loss, and thus restore organ size. Along with wound healing and tissue regeneration, AiP also contributes to tumor repopulation following radiation or chemotherapy. There are several models of AiP. Using an “undead” AiP model that causes hyperplastic overgrowth of Drosophila epithelial tissue, we recently demonstrated that extracellular reactive oxygen species (eROS) are produced by undead epithelial cells, and are necessary for inducing AiP and overgrowth. Furthermore, hemocytes, the Drosophila blood cells, are seen adjacent to the undead epithelial tissue, and may secrete the TNF ortholog Eiger that signals through the TNF receptor to active Jun-N-terminal kinase (JNK) in the undead tissue and induce proliferation. We propose that undead epithelial tissue triggers an inflammatory response that resembles recruitment of macrophages to human epithelial tumors, and that these tumor-associated macrophages release signals for proliferation and tumor growth of the epithelium. This Extra View article summarizes these recent findings with a focus on the role of eROS for promoting regeneration and inflammation-induced tumorigenesis.     

Elimination of oncogenic cells that regulate epithelial homeostasis in Drosophila

Normal epithelial tissues often put anti-tumorigenic pressure on newly emerged oncogenic cells through cell–cell communications. In Drosophila epithelium, clones of oncogenic cells mutant for evolutionarily conserved apico-basal polarity genes such as scribble (scrib) and discs large (dlg) are actively eliminated when surrounded by normal cells. It has been reported that c-Jun N-terminal kinase (JNK) signaling in polarity-deficient cells is crucial for their cell death. However, the mechanism by which normal epithelial tissues exert anti-tumorigenic effects on polarity-deficient cells had been elusive. Here, I describe our genetic studies in Drosophila epithelium especially focused on the role of surrounding normal epithelial cells in response to the emergence of polarity-deficient cells. Furthermore, I also describe recent studies regarding the mechanism by which polarity-deficient cells are extruded from the tissue, and discuss future perspectives on the study of cell–cell communications in epithelial homeostasis.     

Biological Characterization of Human Epithelial Ovarian Carcinoma Cells in Primary Culture: The Insulin-like Growth Factor System

Little is known about the factors regulating epithelial ovarian cancer cell growth. This is due, in large part, to the difficulty in obtaining and culturing human ovarian cells for relevantin vitrostudies. We recently developed a method for culturing epithelial carcinoma cells derived from fresh, untreated epithelial ovarian cancer specimens. The cell populations are free of fibroblasts and reflect the primary tumor as determined by chromosomal analysis. In this study we report on the cells’ growth in serum-free medium and their secretion of CA-125, a glycoprotein marker for ovarian cancer. Furthermore we characterize the insulin-like growth factor (IGF) system in these primary ovarian carcinoma cell cultures. The cells secrete IGF peptides and IGF-binding proteins, possess specific type I IGF receptors, and respond to exogenous IGFs. The culture system reported here provides the basis for further study and manipulation of the IGF system as well as other regulators of epithelial ovarian cancer. Greater understanding of the cellular and molecular mediators of primary human ovarian cancer cell growth may translate into relevant clinical interventions.     

肿瘤细胞粘附、迁移与转移的相关性

肿瘤细胞的粘附、迁移能力与癌转移密切相关. 细胞粘附分子选择素、整合素、免疫球蛋白超家族及钙粘素介导同型或异型细胞间以及细胞与基质间的粘附,其在肿瘤细胞表面表达数量或分布方式的改变直接或间接影响着转移潜能,是肿瘤细胞从原发瘤脱落以及着床的关键性环节.肿瘤细胞的迁移能力被认为是癌转移的限速环节.一般情况下,肿瘤细胞在体内或体外的迁移能力与其转移潜能呈正相关性,肿瘤细胞通过对迁移刺激物的趋化性及趋触性应答而完成向远离器官的转移,其具体分子机制目前还不清楚.     

Transgenic Expression of the Helicobacter pylori Virulence Factor CagA Promotes Apoptosis or Tumorigenesis through JNK Activation in Drosophila

Gastric cancer development is strongly correlated with infection by Helicobacter pylori possessing the effector protein CagA. Using a transgenic Drosophila melanogaster model, we show that CagA expression in the simple model epithelium of the larval wing imaginal disc causes dramatic tissue perturbations and apoptosis when CagA-expressing and non-expressing cells are juxtaposed. This cell death phenotype occurs through activation of JNK signaling and is enhanced by loss of the neoplastic tumor suppressors in CagA-expressing cells or loss of the TNF homolog Eiger in wild type neighboring cells. We further explored the effects of CagA-mediated JNK pathway activation on an epithelium in the context of oncogenic Ras activation, using a Drosophila model of metastasis. In this model, CagA expression in epithelial cells enhances the growth and invasion of tumors in a JNK-dependent manner. These data suggest a potential role for CagA-mediated JNK pathway activation in promoting gastric cancer progression.     

Epiregulin promotes growth and metastasis of gastric cancer via the ERK/JNK/p38 signaling pathway

Epiregulin (EREG) is a ligand of the epidermal growth factor receptor. It belongs to the ErbB family of ligands found overexpressed in various cancers such as colon cancer and lung carcinoma and is likely to play diverse oncogenic roles in several other cancer types. However, little is known about the mechanisms of EREG in the pathogenesis of gastric cancer (GC). The present study was undertaken to investigate whether EREG influences the development and progression in GC. The results revealed that EREG was found to be overexpressed in human GC cells lines. Moreover, EREG induced cell migration, invasion, and proliferation, and inhibited apoptosis in vitro. The study also found that EREG depletion inhibited tumor growth in vivo. Our findings indicated that EREG activated the ERK/JNK/p38 signaling pathway and PI3K/Akt signaling pathways to promote GC malignant progression. Overall, this study suggests that EREG may promote GC development and progression through the ERK/JNK/p38 and PI3K/Akt signaling pathways, which may improve our understanding of the molecular mechanism of EREG in GC. Thus, EREG may be a potential target for GC treatment.     

Identification and targeting of cancer stem cells

Cancer stem cells (CSC) represent malignant cell subsets in hierarchically organized tumors, which are selectively capable of tumor initiation and self‐renewal and give rise to bulk populations of non‐tumorigenic cancer cell progeny through differentiation. Robust evidence for the existence of prospectively identifiable CSC among cancer bulk populations has been generated using marker‐specific genetic lineage tracking of molecularly defined cancer subpopulations in competitive tumor development models. Moreover, novel mechanisms and relationships have been discovered that link CSC to cancer therapeutic resistance and clinical tumor progression. Importantly, proof‐of‐principle for the potential therapeutic utility of the CSC concept has recently been provided by demonstrating that selective killing of CSC through a prospective molecular marker can inhibit tumor growth. Herein, we review these novel and translationally relevant research developments and discuss potential strategies for CSC‐targeted therapy in the context of resistance mechanisms and molecular pathways preferentially operative in CSC.     

角质细胞生长因子2对细胞生长、移行及创伤愈合的作用

角质细胞生长因子2(KGF-2)是成纤维细胞生长因子超家族的一员,由间质细胞合成并分泌,能特异促进上皮细胞增殖、分化与迁移,对脊椎动物多种组织和器官的发育起重要调控作用．通过PCR从人的肾组织cDNA文库中克隆分离获得了KGF-2的cDNA,表明该因子在成人肾中有表达．采用大肠杆菌表达并纯化重组蛋白用于生物学功能研究的结果显示：KGF-2在体外不仅能够促进角质细胞的生长和增殖,而且对其凋亡具有抑制作用,还对细胞的移行具有影响．在动物实验中,KGF-2能促进皮肤切除产生的伤口愈合,提示该蛋白质可以作为创伤治疗或辅助用药的候选分子．     

Stromal–epithelial cell interactions and alteration of branching morphogenesis in macromastic mammary glands

True macromastia is a rare but disabling condition characterized by massive breast growth. The aetiology and pathogenic mechanisms for this disorder remain largely unexplored because of the lack of in vivo or in vitro models. Previous studies suggested that regulation of epithelial cell growth and development by oestrogen was dependent on paracrine growth factors from the stroma. In this study, a co‐culture model containing epithelial and stromal cells was used to investigate the interactions of these cells in macromastia. Epithelial cell proliferation and branching morphogenesis were measured to assess the effect of macromastic stromal cells on epithelial cells. We analysed the cytokines secreted by stromal cells and identified molecules that were critical for effects on epithelial cells. Our results indicated a significant increase in cell proliferation and branching morphogenesis of macromastic and non‐macromastic epithelial cells when co‐cultured with macromastic stromal cells or in conditioned medium from macromastic stromal cells. Hepatocyte growth factor (HGF) is a key factor in epithelial–stromal interactions of macromastia‐derived cell cultures. Blockade of HGF with neutralizing antibodies dramatically attenuated epithelial cell proliferation in conditioned medium from macromastic stromal cells. The epithelial–stromal cell co‐culture model demonstrated reliability for studying interactions of mammary stromal and epithelial cells in macromastia. In this model, HGF secreted by macromastic stromal cells was found to play an important role in modifying the behaviour of co‐cultured epithelial cells. This model allows further studies to investigate basic cellular and molecular mechanisms in tissue from patients with true breast hypertrophy.     

Different hormonal requirements for androgen-independent growth of normal and tumor epithelial cells from rat prostate

Summary The proliferation of isolated normal prostate epithelial cells from rat and man is androgen-independent and requires cholera toxin, insulin, dexamethasone, epidermal growth factor (EGF) and one or more polypeptide factors that are concentrated in bovine neural tissue. The active agents in the neural tissue extract are heparin-binding polypeptides (prostatropins), the predominant form of which has a molecular weight of 17400 and an acetylalanine at the aminoterminus. Prostatropins supported a half-maximal increase in normal prostate epithelial cell number at 50 picomolar. The proliferation of primary and serially-cultured epithelial cells from androgen-responsive Dunning R3327 rat prostate tumors was also androgen-independent, but exhibited dramatic alterations in response to hormones that stimulated normal cell proliferation. At low cell density, androgen-independent growth of isolated tumor-derived epithelial cells was independent on cholera toxin, was stimulated by dexamethasone, required insulin andeither EGFor prostatropin. The presence of either EGF or prostatropin masked the response to the other factor. In the absence of EGF, purified prostatropins supported a half-maximal increase in tumor cell number at 7 picomolar. Endogenous production of EGF-like and prostatropin-like factors or both was suggested by the reduced requirement for EGF and prostatropin at high prostate tumor cell density. These results suggest that anti-hormonal therapies against prostate tumor growth should be based on intervention with the activity of insulin (or insulin-like factors) or simultaneous intervention with both EGF and prostatropin (or their homologues). This work was supported by NIH grants CA 37589 and HL 33847, and grant 1718 from the Council for Tobacco Research. Editor’s Statement This paper is the first report of the comparison of the hormone requirements of primary cultures of normal and tumor prostate epithelial cells from the same system.     

RASSF6 promotes p21Cip1/Waf1-dependent cell cycle arrest and apoptosis through activation of the JNK/SAPK pathway in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is a highly aggressive and common pathological subtype of renal cancer. This cancer is characterized by biallelic inactivation of the von Hippel–Lindau (VHL) tumor suppressor gene, which leads to the accumulation of hypoxia-inducible factors (HIFs). Although therapies targeted at HIFs can significantly improve survival, nearly all patients with advanced ccRCC eventually succumb to the disease. Thus, additional oncogenic events are thought to be involved in the development of ccRCC tumors. In this study, we investigated the role of RASSF6 in ccRCC. Downregulation of RASSF6 was commonly observed in primary tumors relative to matched adjacent normal tissues. Moreover, functional studies established that ectopic re-expression of RASSF6 in ccRCC cells inhibited cell proliferation, clonogenicity, and tumor growth in mice, whereas silencing of RASSF6 dramatically enhanced cell proliferation in vitro and in vivo. Mechanistic investigation suggested that RASSF6 triggers p21^Cip1/Waf1 accumulation to induce G₁ cell cycle arrest and promote apoptosis upon exposure to pro-apoptotic agents, and both of these mechanisms appear to be mediated by activated JNK signaling. Together, these findings suggest that RASSF6 may play a tumor suppressor role in the progression of ccRCC.     

Toll-like receptors expressed in tumor cells: targets for therapy

Toll-like receptors (TLRs), mainly expressing in human immune related cells and epithelial cells, play an essential role in the host defense against microbes by recognizing conserved bacterial molecules. Recently, the expression or up-regulation of TLRs has been detected in many tumor cell lines or tumors, especially epithelial derived cancers. Although the TLR profile varies on different tumor cells, the current evidences indicate that the expression of TLRs is functionally associated with tumor progression. TLR expression may promote malignant transformation of epithelial cells. Engagement of TLRs increases tumor growth and tumor immune escape, and induces apoptosis resistance and chemoresistance in some tumor cells. These findings demonstrate that TLR is a promising target for the development of anticancer drugs and make TLR agonists or antagonists the potential agents for tumor therapy.     

Therapeutic angiogenesis using tumor cell‐conditioned medium

Stem cell‐conditioned medium (CM), which contains angiogenic factors that are secreted by stem cells, represents a potential therapy for ischemic diseases. Along with stem cells, tumor cells also secrete various angiogenic factors. Here, tumor cells as a cell source of CM for therapeutic angiogenesis was evaluated and the therapeutic efficacy of tumor cell CM in mouse hindlimb ischemia models was demonstrated. CM obtained from a human fibrosarcoma HT1080 cell line culture was compared with CM obtained from a human bone marrow‐derived mesenchymal stem cell (MSC) culture. HT1080 CM contained higher concentrations of angiogenic factors compared with MSC CM, which was attributable to the higher cell density that resulted from a much faster growth rate of HT1080 cells compared with MSCs. For use in in vitro and in vivo angiogenesis studies, HT1080 CM was diluted such that HT1080 CM and MSC CM would have the same cell number basis. The two types of CMs induced the same extent of human umbilical vein endothelial cell (HUVEC) proliferation in vitro. The injection of HT1080 CM into mouse ischemic limbs significantly improved capillary density and blood perfusion compared with the injection of fresh medium. Although the therapeutic outcome of HT1080 CM was similar to that of MSC CM, the preparation of CM by tumor cell line culture would be much more efficient due to the faster growth and unlimited life‐time of the tumor cell line. These data suggest the potential application of tumor cell CM as a therapeutic modality for angiogenesis and ischemic diseases. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:456–464, 2016