Correlation between the presence of microvilli and the growth or metastatic potential of tumor cells

Harnessing atomic force microscopy-based single-cell analysis to advance physical oncology

Single-cell analysis is an emerging and promising frontier in the field of life sciences, which is expected to facilitate the exploration of fundamental laws of physiological and pathological processes. Single-cell analysis allows experimental access to cell-to-cell heterogeneity to reveal the distinctive behaviors of individual cells, offering novel opportunities to dissect the complexity of severe human diseases such as cancers. Among the single-cell analysis tools, atomic force microscopy (AFM) is a powerful and versatile one which is able to nondestructively image the fine topographies and quantitatively measure multiple mechanical properties of single living cancer cells in their native states under aqueous conditions with unprecedented spatiotemporal resolution. Over the past few decades, AFM has been widely utilized to detect the structural and mechanical behaviors of individual cancer cells during the process of tumor formation, invasion, and metastasis, yielding numerous unique insights into tumor pathogenesis from the biomechanical perspective and contributing much to the field of cancer mechanobiology. Here, the achievements of AFM-based analysis of single cancer cells to advance physical oncology are comprehensively summarized, and challenges and future perspectives are also discussed. RESEARCH HIGHLIGHTS: Achievements of AFM in characterizing the structural and mechanical behaviors of single cancer cells are summarized, and future directions are discussed. AFM is not only capable of visualizing cellular fine structures, but can also measure multiple cellular mechanical properties as well as cell-generated mechanical forces. There is still plenty of room for harnessing AFM-based single-cell analysis to advance physical oncology.

Recalculating the Route: Repositioning Antimicrobial Peptides for Cancer Treatment

Resistance to antimicrobial drugs has been considered a public health problem. Likewise, the increasing resistance of cancer cells to drugs currently used in therapy has also become a problem. Therefore, the research and development of synthetic peptides bring a new perspective on the emergence of new drugs for treating this resistance since bioinformatics provides a means to optimize these molecules and save time and costs in research. Peptides have several mechanisms of action, such as forming pores on the cell membrane and inhibiting protein synthesis. Some studies report the use of antimicrobial peptides with the potential for action against cancer cells, suggesting a repositioning of antimicrobial peptides to fight back cancer resistance. There is an alteration in the microenvironment, making its net charge negative for the survival and growth of cancer cells. The changes in glycoproteins favor the membrane to have a more negative charge, favoring the interaction between the cells and the peptide, thus making possible the repositioning of these antimicrobial peptides against cancer. Here, we will discuss the mechanism of action, targets and effects of peptides, comparison between microbial and cancer cells, and proteomic changes caused by the interaction of peptides and cells.

Current research status of anti-cancer peptides: Mechanism of action, production, and clinical applications

The escalating rate of cancer cases, together with treatment deficiencies and long-term side effects of currently used cancer drugs, has made this disease a global burden of the 21st century. The number of breast and lung cancer patients has sharply increased worldwide in the last few years. Presently, surgical treatment, radiotherapy, chemotherapy, and immunotherapy strategies are used to cure cancer, which cause severe side effects, toxicities, and drug resistance. In recent years, anti-cancer peptides have become an eminent therapeutic strategy for cancer treatment due to their high specificity and fewer side effects and toxicity. This review presents an updated overview of different anti-cancer peptides, their mechanisms of action and current production strategies employed for their manufacture. In addition, approved and under clinical trials anti-cancer peptides and their applications have been discussed. This review provides updated information on therapeutic anti-cancer peptides that hold great promise for cancer treatment in the near future.

Melatonin modulates the Warburg effect and alters the morphology of hepatocellular carcinoma cell line resulting in reduced viability and migratory potential

AIMS

Hepatocellular Carcinoma (HCC) is a primary neoplasm derived from hepatocytes with low responsiveness and recurrent chemoresistance. Melatonin is an alternative agent that may be helpful in treating HCC. We aimed to study in HuH 7.5 cells whether melatonin treatment exerts antitumor effects and, if so, what cellular responses are induced and involved.

MAIN METHODS

We evaluated the effects of melatonin on cell cytotoxicity and proliferation, colony formation, morphological and immunohistochemical aspects, and on glucose consumption and lactate release.

KEY FINDINGS

Melatonin reduced cell motility and caused lamellar breakdown, membrane damage, and reduction in microvillus. Immunofluorescence analysis revealed that melatonin reduced TGF and N-cadherin expression, which was further associated with inhibition of epithelial-mesenchymal transition process. In relation to the Warburg-type metabolism, melatonin reduced glucose uptake and lactate production by modulating intracellular lactate dehydrogenase activity.

SIGNIFICANCE

Our results indicate that melatonin can act upon pyruvate/lactate metabolism, preventing the Warburg effect, which may reflect in the cell architecture. We demonstrated the direct cytotoxic and antiproliferative effect of melatonin on the HuH 7.5 cell line, and suggest that melatonin is a promising candidate to be further tested as an adjuvant to antitumor drugs for HCC treatment.

Bioactive cationic peptides as potential agents for breast cancer treatment

Breast cancer continues to affect millions of women worldwide, and the number of new cases dramatically increases every year. The physiological causes behind the disease are still not fully understood. One in every 100 cases can occur in men, and although the frequency is lower than among women, men tend to have a worse prognosis of the disease. Various therapeutic alternatives to combat the disease are available. These depend on the type and progress of the disease, and include chemotherapy, radiotherapy, surgery, and cancer immunotherapy. However, there are several well-reported side effects of these treatments that have a significant impact on life quality, and patients either relapse or are refractory to treatment. This makes it necessary to develop new therapeutic strategies. One promising initiative are bioactive peptides, which have emerged in recent years as a family of compounds with an enormous number of clinical applications due to their broad spectrum of activity. They are widely distributed in several organisms as part of their immune system. The antitumoral activity of these peptides lies in a nonspecific mechanism of action associated with their interaction with cancer cell membranes, inducing, through several routes, bilayer destabilization and cell death. This review provides an overview of the literature on the evaluation of cationic peptides as potential agents against breast cancer under different study phases. First, physicochemical characteristics such as the primary structure and charge are presented. Secondly, information about dosage, the experimental model used, and the mechanism of action proposed for the peptides are discussed.

Study of the metabolic alterations in patulin-induced neoplastic transformation in normal intestinal cells

Several surveillance studies have reported significantly high level of patulin (PAT), mycotoxin in fruit juices suggesting the possible exposure to human. In vitro studies have showed that PAT can alter the permeability, ion transport and modulates tight junction of intestine. In real scenario, human can be exposed with low levels of PAT for longer duration through different fruits and their products. Hence, keeping this possibility in view, we conducted a study where normal intestinal cells were exposed with non-toxic levels of PAT for longer duration and found that PAT exposure causes cancer-like properties in normal intestinal cells. It is a well-known fact that cancer cells rewired their metabolism for cell growth and survival and metabolites closely depict the phenotypic properties of cells. Here, metabolomic study was performed in the PAT transformed and passage matched non-transformed cells using ¹H HRMAS NMR. We have identified 12 significantly up-regulated metabolites, which, interestingly, were majorly amino acids, suggesting that PAT-induced pre-cancerous cells are involved in acquirement of nutrients for high protein turn-over. Furthermore, pathway analysis of metabolomics data indicated that aminoacyl tRNA biosynthesis, D-glutamate metabolism, glyoxylate and dicarboxylate metabolism and nitrogen metabolism were majorly hampered in PAT-induced pre-cancerous properties in normal intestinal cells.

Ultrastructural Analysis of Inflammatory Breast Cancer Cell Clusters in an Ex Vivo Environment Mechanically Mimicking the Lymph Vascular System

Background:

Inflammatory breast cancer (IBC) is a rare form of breast cancer with a poor prognosis. IBC is characterized by florid lymphovascular tumor emboli in the skin and the parenchyma of the breast. We hypothesized that the formation of these emboli/clusters plays a pivotal role in IBC metastasis and its rapid progression, and that their structure and function may be a key to identifying molecular biological differences between IBC and non IBC.

Methods:

Mechanical methods were used to mimic the lymph fluid viscosity by adding 2.25% of PEG8000 to the media. Clusters were obtained for IBC tumor cell lines (SUM149 and IBC-3), non IBC tumor cell lines (MDA-MB-231, MDA-MB-468, and MCF7), and a non-tumorigenic human mammary epithelial cell line (MCF10A). Clusters were analyzed by light microscopy, and then prepared for and observed by transmission electron microscopy (TEM).

Results:

Significant differences were seen between IBC and non IBC clusters. The TEM analysis revealed that IBC cells harbored numerous microvilli and microvesicles, both on the free outer surface and inside the cluster. Microvilli from IBC cell clusters were noted at higher density and were longer than those of non IBC cell clusters.

Conclusions:

IBC tumor cell clusters exhibited distinct ultrastructural features characterized by the presence of long, crowded microvilli and numerous microvesicles. These microvilli may play an important role in the biology and aggressiveness of IBC.

Paxillin knockdown suppresses metastasis and epithelial‑mesenchymal transition in colorectal cancer via the ERK signalling pathway

Paxillin (PXN) is a cytoplasmic protein that plays an important role in regulating focal adhesion, cytoskeletal rearrangements and cell motility. The present study aimed to investigate the role of PXN in the metastasis of human colorectal cancer (CRC) and its possible mechanisms. Immunohistochemical staining of tissues from 102 surgical CRC patients revealed that high PXN expression was positively correlated with tumour‑node‑metastasis (TNM) stage, lymph node metastasis, distant metastasis, and recurrence at distant sites after radical surgery. In 24 cases of stage IV CRC, PXN expression in liver metastasis was higher than that in the matched primary tumour. The knockdown of PXN inhibited the proliferation, migration and invasion potential of SW480 cells in vitro and in vivo. Transmission electron microscopy revealed the effect of PXN on ultrastructural characteristics, observed mainly in microvilli and desmosomes. The downregulation of PXN decreased the activation of extracellular regulated protein kinase (ERK) and suppressed the epithelial‑mesenchymal transition (EMT) process. Following the downregulation of PXN, the addition of an ERK activator or inhibitor restored or further suppressed EMT, respectively, accompanied by corresponding changes in cell migration and invasion. Collectively, the present results confirmed the important role of PXN in CRC metastasis and revealed that PXN regulated EMT progression via the ERK signalling pathway. PXN may represent a future therapeutic strategy to prevent the EMT‑associated progression and invasion of CRC.

Integrin and Heparan Sulfate Dual-Targeting Peptide Assembly Suppresses Cancer Metastasis

Metastasis is one of the ongoing challenges in cancer therapy which most treatments failed to address. Inspired by the upregulated expression of both integrin β1 and heparan sulfate in metastatic tumors, we developed an integrin/HS dual-targeting peptide assembly that selectively inhibits cancer cell migration and invasion. Particularly, the dual-targeting peptide self-assembles into nanofibrous microdomains specifically on the cancer cell membrane, triggering spatial organization of integrins, which form clusters on the apical membrane. Via the actin cytoskeleton that physically connects to integrin clusters, the oncogene yes-associated protein, which regulates cancer metastasis, is deactivated. We showed that in multiple cancer cell lines, including the highly metastatic pancreatic cancer cells, the dual-targeting peptide exerts potent and dose-dependent antimetastatic effects. Our work illustrates how basic biochemical insights can be exploited as the basis for nano-biointerface fabrication, which is potentially a general design strategy for nanomedicine development.

Bacteriocins: perspective for the development of novel anticancer drugs

Antimicrobial peptides (AMPs) from prokaryotic source also known as bacteriocins are ribosomally synthesized by bacteria belonging to different eubacterial taxonomic branches. Most of these AMPs are low molecular weight cationic membrane active peptides that disrupt membrane by forming pores in target cell membranes resulting in cell death. While these peptides known to exhibit broad-spectrum antimicrobial activity, including antibacterial and antifungal, they displayed minimal cytotoxicity to the host cells. Their antimicrobial efficacy has been demonstrated in vivo using diverse animal infection models. Therefore, we have discussed some of the promising peptides for their ability towards potential therapeutic applications. Further, some of these bacteriocins have also been reported to exhibit significant biological activity against various types of cancer cells in different experimental studies. In fact, differential cytotoxicity towards cancer cells as compared to normal cells by certain bacteriocins directs for a much focused research to utilize these compounds as novel therapeutic agents. In this review, bacteriocins that demonstrated antitumor activity against diverse cancer cell lines have been discussed emphasizing their biochemical features, selectivity against extra targets and molecular mechanisms of action.

Ultrastructural changes induced by Solanum incanum aqueous extract on HCT 116 colon cancer cells

Medicinal plants have recently gained increasing scientific interest as an important source of molecules with different therapeutic potentials. Accordingly, the present study was carried out to investigate ultrastructural changes induced by the aqueous extract of Solanum incanum (SI) fruit on human colorectal carcinoma cell line (HCT 116 cells). Examination of SI-treated HCT 116 cells with transmission electron microscopy (TEM) demonstrated numerous ultrastructural changes in the form of loss of the surface microvilli, mitochondrial damage and dilatation of cristae, and formation of autophagic vacuoles and increasing numbers of lipid droplets. Also, majority of the treated cells showed nuclear shrinkage with chromatin condensation and nucleolar changes. Moreover, some cells showed focal areas of cytoplasmic degeneration associating with formation of myelin figures and fatty globules. In conclusion, TEM was able to verify cytotoxicity of SI aqueous extract against HCT 116 colon cancer cells.

Tumor cell membrane-targeting cationic antimicrobial peptides: novel insights into mechanisms of action and therapeutic prospects

There is an ongoing need for effective and targeted cancer treatments that can overcome the detrimental side effects presented by current treatment options. One class of novel anticancer molecules with therapeutic potential currently under investigation are cationic antimicrobial peptides (CAPs). CAPs are small innate immunity peptides found ubiquitously throughout nature that are typically membrane-active against a wide range of pathogenic microbes. A number of CAPs can also target mammalian cells and often display selective activity towards tumor cells, making them attractive candidates as novel anticancer agents warranting further investigation. This current and comprehensive review describes key examples of naturally occurring membrane-targeting CAPs and their modified derivatives that have demonstrated anticancer activity, across multiple species of origin and structural subfamilies. In addition, we address recent advances made in the field and the ongoing challenges faced in translating experimental findings into clinically relevant treatments.

Biodistribution of Evans blue in an orthotopic AY-27 rat bladder urothelial cell carcinoma model: implication for the improved diagnosis of non-muscle-invasive bladder cancer (NMIBC) using dye-guided white-light cystoscopy

OBJECTIVES

To investigate the possibility of using Evans blue (EB) as a novel diagnostic tool to detect bladder tumours with white-light (WL) cystoscopy, in this preclinical study we examine the biodistribution of EB in the different layers (urothelium, submucosa, muscle) of a normal rat bladder and a rat bladder bearing a malignant urothelium composed of syngeneic AY-27 tumour cells.

MATERIALS AND METHODS

EB was instilled into both normal as well as tumour-bearing rat bladders. After instillation, bladders were removed and snap frozen in liquid nitrogen. The distribution of EB in the different layers was quantified using fluorescence microscopy. To gain more insight into the mechanism underlying the selective accumulation of EB in tumour tissue, bladder sections were prepared for ultrastructural investigations by means of transmission electron microscopy (TEM). In addition, we also examined the expression of E-cadherin, claudin-1 and desmoglein-1 by immunohistochemistry to study the integrity of the bladder wall, as these molecules are key constituents of adherens junctions, tight junctions and desmosomes, respectively.

RESULTS

In most cases, the accumulation of EB in malignant bladders was substantially higher than in healthy bladders, at least when 1 mm EB instillations were used. In case of a 1 mm EB instillation for 2 h, the EB-associated fluorescence in malignant urothelial tissue was 55-times higher than the fluorescence found in normal urothelium. Ultrastructurally, malignant tissue displayed wider intercellular spaces and a decreased number of cell junction components compared with normal tissue, pointing to defects in the urothelial barrier. There were no differences in the expression of E-cadherin, whereas desmoglein-1 staining was stronger in the membranes of healthy bladder urothelium compared with tumour tissue. Claudin-1 expression was negative in all samples tested.

CONCLUSION

EB is selectively taken up by tumour tissue after intravesical instillations in rats bearing bladder tumours. The lower expression of desmoglein-1 in tumour samples, together with the reduced presence of desmosomes seen with TEM, likely imply that desmosomes play an important role in the ultrastructural differences between healthy rat urothelium and tumour tissue, and secondary to that, to the differential uptake of EB in both tissues. We consider that our findings could be useful for future clinical developments in the field of diagnostics for bladder cancer.

Inflammation-related carcinogenesis: current findings in epidemiological trends, causes and mechanisms

Inflammation is a definite cancer-causing factor as revealed by cumulative basic, clinical and epidemiological studies. It is mostly induced by infectious agents. For instance, infection with papillomaviruses associates with anogenital cancers, especially cervical cancers; Helicobacter pylori infection of the stomach tends to increase the risk of stomach cancer; chronic hepatitis B & C viruses and fluke infections of the liver increase liver cancers; autoimmune diseases, e.g., inflammatory bowel diseases, associate with development of colorectal cancer, and aerial irritants (foreign bodies) such as asbestos or fine particulate matter (PM2.5) in outdoor air increase malignant pleural mesotheliomas or lung cancers. These are typical examples of inflammation-related carcinogenesis. It is apparent that the pathogens to induce inflammatory reactions in specific organs are not related to each other. However, the underlying pathogenesis in common is to induce and/or sustain inflammation. In this article, I would like to review the up-to-date findings of epidemiological trends, causes and mechanisms of inflammation-related carcinogenesis.

Coleusin factor, a novel anticancer diterpenoid, inhibits osteosarcoma growth by inducing bone morphogenetic protein-2-dependent differentiation

Coleusin factor is a diterpenoid compound isolated from the root of a tropical plant, Coleus forskohlii. Although Coleusin factor has been reported to suppress proliferation of and induce apoptosis in several types of cancer cells, the effects of Coleusin factor on osteosarcoma and the underlying mechanism are still not fully understood. In this study, we show that Coleusin factor treatment potently inhibits the growth of osteosarcoma cells associated with G(1) cell-cycle arrest. Interestingly, apoptosis and cell death are not induced. Instead, Coleusin factor causes osteosarcoma cells to exhibit typical properties of differentiated osteoblasts, including a morphologic alteration resembling osteoblasts, the expression of osteoblast differentiation markers, elevated alkaline phosphatase activity, and increased cellular mineralization. Coleusin factor treatment significantly increases the expression of bone morphogenetic protein-2 (BMP-2), a crucial osteogenic regulator, and runt-related transcription factor 2 (RUNX2), one of the key transcription factors of the BMP pathway. When BMP-2 signaling is blocked, Coleusin factor fails to inhibit cell proliferation and to induce osteoblast differentiation. Thus, upregulation of BMP-2 autocrine is critical for Coleusin factor to induce osteoblast differentiation and exert its anticancer effects on osteosarcoma. Importantly, administration of Coleusin factor inhibits the growth of osteosarcoma xenografted in nude mice without systemic or immunologic toxicity. Osteosarcoma is a highly aggressive cancer marked by the loss of normal differentiation. Coleusin factor represents a new type of BMP-2 inducer that restores differentiation in osteosarcoma cells. It may provide a promising therapeutic strategy against osteosarcoma with minimal side effects.

SiRNA-mediated silencing of paxillin down-regulates ERK1/2 signaling and alters cell ultrastructure in colorectal carcinoma cell line SW480

AIM: To study the effect of silencing of paxillin overexpression on cell signaling and ultrastructure in colorectal carcinoma cell line SW480.

METHODS: Using empty plasmid as a negative control, two siRNA fragments were transfected into a colorectal carcinoma cell line SW480 which overexpresses paxillin. Stably transfected cells were screened and three new cell lines NC, SW545 and SW782 were obtained, which carried the negative control, the siRNA targeting the site 545-565, and the siRNA targeting the site 782-802, respectively. The expression and site-specific phosphorylation of paxillin, FAK, ERK1/2 and AKT1/2/3 were examined in the four cell lines by Western blot. Specimens were prepared with cultured carcinoma cells to observe cell ultrastructure by transmission electron microscopy.

RESULTS: Paxillin overexpression in SW545 cells was not silenced at all, whereas silenced paxillin overexpression and remarkably reduced phosphorylation of paxillin (Tyr118) were observed in SW782 cells. Expression of AKT1/2/3 and FAK as well as their site-specific phosphorylation were substantially the same in the four cell lines. Although expression of ERK1/2 was substantially the same in the four cell lines, significantly reduced phosphorylation of ERK1/2 (Thr202/Tyr204) was observed in SW782 cells. There was no distinct ultrastructural difference between NC cells and SW480 cells, whereas dramatic ultrastructural changes were observed in SW782 cells, such as much more microvilli, microfilament and microtubule bundles, lysosomes and much less mitochondria.

CONCLUSION: Paxillin overexpression may play an important role in the malignant transformation of colorectal carcinoma cells, which is characterized by dramatic ultrastructural changes that can be reversed by silencing paxillin overexpression. Activation of ERK1/2 signaling downstream of paxillin is indispensable for the malignant transformation of colorectal carcinoma cells.

Inflammation and free radicals in tumor development and progression

Inflammation is thought to be one of the major contributors to carcinogenesis. Accumulated studies in this field revealed that free radicals produced by inflammatory cells not only cause direct damage to DNA but also exert indirect effects such as de-regulation of cell proliferation and apoptosis, stimulation of angiogenesis, and modification of gene/protein expressions and protein activities, all of which are a critical step toward carcinogenesis. Free radicals have also been reported to act as both initiator and promoter of carcinogenic process. Recent evidence shows that free radicals convert benign tumors to more malignant ones (i.e. tumor progression) leading to the final stage of carcinogenesis. This article reviews the current findings linking inflammation and cancer, and shed light on inflammatory cell-derived free radicals as major endogenous reactive substances for tumor development and progression.

Characterization of the progressive sublines derived from a weakly malignant cloned cell line, ER-1, co-inoculated subcutaneously with a foreign body

We previously established an experimental model of tumor progression using a weakly malignant rat mammary carcinoma cell line, ER-1. Using this model, we demonstrated that ER-1 cells converted into highly tumorigenic and metastatic cells, ERpP, by s.c. co-inoculation with plastic plates. We here compared in vitro biological properties associated with malignancy of ER-1 cells with those of ERpP cells which were highly malignant when inoculated into syngeneic rats. In vitro growth rate of ERpP cells was higher than that of ER-1 cells under a low nutrient condition. Invasion capacity of ERpP cells to rat lung endothelial cell monolayer or reconstituted basement membrane, Matrigel, was higher than that of ER-1 cells. Migration of ERpP cells toward fibronectin or laminin was also significantly higher than that of ER-1 cells. There was no difference in gelatinolytic or plasminogen activator activity detected in conditioned media between ER-1 and ERpP cells. Furthermore, we found that ER-1 cells communicated better among themselves and with normal fibroblasts through gap junctions compared to ERpP cells. These results suggest that growth advantage in a poor nutrient condition, enhancement of cell motility, and loss or decrease of junctional communication may be associated with tumor progression of ER-1 cells.

Morphological changes of microvilli on different surfaces of epithelial cells in the rat bladder treated with N-butyl-N-(4-hydroxybutyl) nitrosamine

This study investigates morphological changes of microvilli occurring on different surfaces of epithelial cells, including luminal surfaces, intercellular surfaces, and basal cell surfaces adjacent to the basement membrane (BM), in the rat bladder treated with N-butyl-N(4-hydroxybutyl) nitrosamine (BBN) by transmission electron microscopy (TEM). The present results showed that the microvilli were observed not only on the luminal surfaces of epithelial cells but also on the intercellular surfaces and basal cell surfaces adjacent to the BM following administration of BBN. There were a variety of morphological changes of microvilli on the luminal surfaces, intercellular surfaces and basal cell surfaces adjacent to the BM, respectively. It is suggested that the microvilli occurring on the luminal surfaces may not represent characteristics of the microvilli occurring on the intercellular surfaces and on the basal cell surfaces adjacent to the BM, and that occurrence of the microvilli on the epithelial cell surfaces may reflect a higher metabolic activity of proliferative epithelial cells and may play an important role in the processes of tumor growth during bladder carcinogenesis.

A variant actin (beta m) reduces metastasis of mouse B16 melanoma

We recently reported an acidic actin co-expressed with beta and gamma actin in mouse B16 melanoma, whose expression was inversely correlated with the metastatic potential. The cDNA for this actin is slightly different from the hitherto recognized mouse beta actin cDNA, and we designated it beta m actin. In order to directly investigate the effects of beta m actin on metastasis, we transfected the beta m actin cDNA into a re-cloned B16-BL6 cell line which is more invasive than the highly metastatic cell line, B16-F10; we have already reported the suppressive effect of beta m actin on the invasiveness of B16-F10. Here we report on the decline in the metastatic ability of beta m-transfected cells. In the beta m-transfected B16-BL6 cell line, we observed an increase in the organization of actin stress fibers, accompanied by a decrease in metastasis to the lung, in the invasion of collagen gels, in in vivo invasiveness, and in cell migration on a glass plate covered with colloidal gold particles. We observed no correlation of beta m actin expression either with cell attachment to Matrigel, or with type-IV collagenase expression. These results suggest that beta m actin can play a role in reducing the invasiveness of mouse B16 melanoma, most probably through decreasing cell motility, which may thus result in suppression of the metastatic ability of cells.

Enhancement of tumorigenicity and invasion capacity of rat mammary adenocarcinoma cells by epidermal growth factor and transforming growth factor-beta

We have studied the effects of growth factors and cytokines on the tumorigenicity and invasion capacity of tumor cells by using regressor and progressor tumor cell lines (ER-1 and ERpP, respectively) derived from an SHR rat mammary adenocarcinoma. ER-1 cells regress spontaneously whereas ERpP cells show invasive growth and high metastasis to lung and other organs in syngeneic SHR rats. When ER-1 cells were pretreated with either epidermal growth factor (EGF) or transforming growth factor-beta (TGF-beta) for 24 h in vitro, and intraperitoneally transplanted into SHR rats, they grew and killed the host, whereas ER-1 cells pretreated with tumor necrosis factor-alpha did not. Tumorigenicity and invasion capacity of ERpP cells were also enhanced by treatment with EGF and TGF-beta. The ER-1 cells pretreated with EGF, once grown in vivo, had acquired irreversible tumorigenicity and invasion capacity without requiring further EGF treatment, and the enhanced malignancy was irreversible. These findings suggest that growth factors play an important role in acquisition of malignancy of tumor cells.

Effects of areca nut on growth, differentiation and formation of DNA damage in cultured human buccal epithelial cells

Because the high incidence of oral cancers in South-East Asia is causally linked to the common habit of betel quid chewing, the effects of an aqueous extract of areca nut, one of the main ingredients of the quid, on growth, differentiation, morphology and DNA damage were studied in cultured human buccal epithelial cells. An acute exposure (3 hr) of the cells to the extract altered their morphology and induced ridges in the plasma membrane, with indications of internalization of extract particles. Such exposure also caused formation of DNA single-strand breaks which accumulated during post-treatment culture, indicating continuous exposure to residual particles and/or the possibility of inhibited DNA repair. The extract accelerated terminal differentiation of the cells, measured as involucrin expression at relatively non-toxic levels. The extract caused similar loss of colony-forming efficiency in normal cells and in a buccal carcinoma cell line (SqCC/YI) which was defective in its ability to undergo differentiation, indicating that extract toxicity could occur independently from this response. Finally, the genotoxicity of the salivary areca-nut-specific carcinogen 3-(N-nitrosomethyl-amino)propionaldehyde, was demonstrated by the formation of DNA protein cross-links and DNA single-strand breaks in normal buccal epithelial cells. These findings in vitro suggest that betel quid carcinogenesis in the human oral cavity may involve cytopathic alterations of normal cell morphology, growth and differentiation, as well as formation of DNA damage by areca-nut-related agents extracted or formed in saliva.

Isolation of subclones with different tumorigenicity and metastatic ability from rat nephroblastoma cell line, ENUT

Seven subclones derived from a chemically induced rat nephroblastoma cell line, ENUT, were isolated and their cytological characteristics were examined in order to investigate the biological nature of the parent tumor. The subclones were divisible into two types based on morphological and biological features: polygonal cells with well developed junctional complexes and less developed cell surface microvilli, showing a doubling time of 13.0 to 14.0 h and tumorigenicity in nude mice of 42-100%, and spindle-shaped cells with poorly developed junctional complexes and well developed microvilli, showing a doubling time of 9.7 to 12.2 h and 100% tumorigenicity. Potential for both spontaneous and experimental metastasis to the lungs was apparently higher in the spindle-shaped clones than in the polygonal clones. In spite of their differing characteristics, the cytochemical phenotypes of the two clonal types were almost identical to those of immature renal tubules of the developing fetal kidney. The present findings suggest that these subclones possess characteristics of early nephrogenic epithelial cells, and we speculate that the biological differences observed among the subclones may be explained by differences in malignant progression. In addition, these clones appear to be a useful model for the study of tumorigenicity and metastasis.