CVM-1118 (foslinanib), a 2-phenyl-4-quinolone derivative, promotes apoptosis and inhibits vasculogenic mimicry via targeting TRAP1

CVM-1118 (foslinanib) is a phosphoric ester compound selected from 2-phenyl-4-quinolone derivatives. The NCI 60 cancer panel screening showed CVM-1125, the major active metabolite of CVM-1118, to exhibit growth inhibitory and cytotoxic effects at nanomolar range. CVM-1118 possesses multiple bioactivities, including inducing cellular apoptosis, cell cycle arrest at G₂/M, as well as inhibiting vasculogenic mimicry (VM) formation. The TNF receptor associated protein 1 (TRAP1) was identified as the binding target of CVM-1125 using nematic protein organization technique (NPOT) interactome analysis. Further studies demonstrated CVM-1125 reduced the protein level of TRAP1 and impeded its downstream signaling by reduction of cellular succinate levels and destabilization of HIF-1α. The pharmacogenomic biomarkers associated with CVM-1118 were also examined by Whole Genome CRISPR Knock-Out Screening. Two hits (STK11 and NF2) were confirmed with higher sensitivity to the drug in cell knock-down experiments. Biological assays indicate that the mechanism of action of CVM-1118 is via targeting TRAP1 to induce mitochondrial apoptosis, suppress tumor cell growth, and inhibit vasculogenic mimicry formation. Most importantly, the loss-of-function mutations of STK11 and NF2 are potential biomarkers of CVM-1118 which can be applied in the selection of cancer patients for CVM-1118 treatment. CVM-1118 is currently in its Phase 2a clinical development.

Comparison of glutathione peroxidase-3 protein expression and enzyme bioactivity in normal subjects and patients with sepsis

BACKGROUND

Serum glutathione peroxidase-3 (GPx-3) is known as a key selenoprotein with antioxidant properties. GPx-3 deficiency has been associated with sepsis. The objectives of this study are (1) to compare the GPx-3 protein concentrations and GPx-3 bioactivity in normal healthy subjects and septic patients, and (2) to evaluate the relationship between GPx-3 bioactivity and its protein concentration.

METHODS

Serum samples were collected from 50 normal healthy subjects and 70 septic patients. The reliable bioanalytical methods for GPx-3 protein concentration and bioactivity in human serum were developed and validated. Analyses of GPx-3 bioactivity and GPx-3 protein concentration were then performed.

RESULTS

Geometric mean GPx-3 bioactivity was 78.13U/l for patients with sepsis, significantly lower than normal subjects with 108.21U/l (p<0.0001). Similarly, the GPx-3 protein concentration was significantly lower in patients with sepsis than in normal subjects, with the mean GPx-3 value of 0.78 vs 3.10μg/ml, respectively (p<0.0001). A positive correlation was observed between the GPx-3 bioactivity and its corresponding protein concentration in septic serum samples (R=0.74, p<0.0001), regardless of gender or age difference.

CONCLUSION

These findings suggest that the decrease in GPx-3 bioactivity observed in the septic patients was resulted from the significant sepsis-related decline of GPx-3 protein concentrations.

Phase I dose escalation study of CVM-1118, a novel anti-vascular mimicry agent, in patients with advanced cancers

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Background: CVM-1118 is an oral NCE that demonstrated potent anti-tumor effects in several tumor xenograft models, via multiple MOAs including induction of cancer cell cycle arrest and apoptosis, and reducing vasculogenic mimicry (VM) network formation in cancer cells, providing a promising therapeutic means in the treatment of malignant tumors that have metastatic potential. Methods: Patients with advanced tumors are being enrolled into 2 ongoing open-label Phase I dose escalation studies in both US (CVM-001) and Taiwan (CVM-002) to evaluate ethnic differences in drug responses. CVM-1118 capsules are administrated orally QD/BID in a 28-day cycle for 4 cycles. The primary objectives are to evaluate the safety, tolerability and pharmacokinetics (PK) and establish the Recommended Phase 2 Dose (RP2D). The secondary objective is to evaluate the therapeutic response after receiving treatment. Beyond 4 cycles, patients showing clinical benefit with CVM-1118 may enter extension cohort to continue the treatment. Results: To date, 28 pts (16 M/12 F)received CVM-1118 across 6 dose levels (50 to 800 mg daily). Median number of days was 52 (range 2 to 135). For CVM-001, 2 DLTs (grade 5 dehydration and grade 3 fatigue) were reported at cohort 6 (800 mg/daily) and the MTD is currently under evaluation. For CVM-002, 3 cohorts (100 to 400 mg/daily) have been completed without DLT. Enrolment to cohort 5 (600 mg/daily) is in progress. From both studies, the most common drug-related AEs included manageable diarrhea, nausea, and vomiting. Rapid oral absorption was observed with Tmax < 2 hr. Bioconversion to active metabolite, CVM-1125, occurred rapidly and the drug exposure increased with increasing dose levels. However, patients in US study showed higher drug exposure than those in Taiwan study. Two patients at 200 mg/daily cohort in Taiwan completing 4-cycle treatment and showing stable disease continued into extension cohort with higher dose. Conclusions: In this ongoing study, Asian patients in Taiwan appear to have better tolerance for CVM-1118 than those in US, likely due to lower drug exposure at same dose level, and some patients have experienced clinical benefit. Clinical trial information: NCT02507544; NCT02703298.

Tumor cell vascular mimicry: Novel targeting opportunity in melanoma

In 1999, the American Journal of Pathology published an article, entitled "Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry" by Maniotis and colleagues, which ignited a spirited debate for several years and earned the journal's distinction of a "citation classic" (Maniotis et al., 1999). Tumor cell vasculogenic mimicry (VM), also known as vascular mimicry, describes the plasticity of aggressive cancer cells forming de novo vascular networks and is associated with the malignant phenotype and poor clinical outcome. The tumor cells capable of VM share the commonality of a stem cell-like, transendothelial phenotype, which may be induced by hypoxia. Since its introduction as a novel paradigm for melanoma tumor perfusion, many studies have contributed new findings illuminating the underlying molecular pathways supporting VM in a variety of tumors, including carcinomas, sarcomas, glioblastomas, astrocytomas, and melanomas. Of special significance is the lack of effectiveness of angiogenesis inhibitors on tumor cell VM, suggesting a selective resistance by this phenotype to conventional therapy. Facilitating the functional plasticity of tumor cell VM are key proteins associated with vascular, stem cell, extracellular matrix, and hypoxia-related signaling pathways--each deserving serious consideration as potential therapeutic targets and diagnostic indicators of the aggressive, metastatic phenotype. This review highlights seminal findings pertinent to VM, including the effects of a novel, small molecular compound, CVM-1118, currently under clinical development to target VM, and illuminates important molecular pathways involved in the suppression of this plastic, aggressive phenotype, using melanoma as a model.

DNA hypomethylation is crucial for apoptotic DNA to induce systemic lupus erythematosus-like autoimmune disease in SLE-non-susceptible mice

OBJECTIVES

Systemic lupus erythematosus (SLE) is characterized by serological presence of anti-double-stranded DNA (dsDNA) antibodies and its pathogenesis remains unclarified. Our previous work found that syngeneic activated lymphocyte-derived DNA (ALD-DNA) induced SLE-like autoimmune disease in the SLE-non-prone BALB/c mice. Here, the biological and chemical characteristics of the somatic DNA were focused upon to investigate their contribution to the autoimmunity induction to provide clues for the understanding of the pathogenesis of SLE in non-susceptible strains.

METHODS

Induction of anti-dsDNA antibodies, glomerulonephritis and proteinuria was evaluated in BALB/c mice after subcutaneous immunization with apoptotic DNA (annexin-V+) extracted from concanavalin A or UV-treated apoptotic splenocytes or necrotic DNA from necrotic splenocytes. The hypomethylated apoptotic DNA and the normal DNA were then methylated and demethylated, respectively, by CpG methylase or 5-azacytidine treatment to re-evaluate their immunogenicity in BALB/c mice.

RESULTS

It was apoptotic but not necrotic DNA that induced SLE-like autoimmune disease and the level of apoptotic DNA was associated with the level of anti-dsDNA antibodies. The apoptotic DNA exhibited significantly lower methylation levels than the normal DNA. Methylation of the hypomethylated apoptotic DNA significantly impaired its ability to induce anti-dsDNA antibodies and proteinuria, while demethylation of the normal or necrotic DNA endowed them with the immunogenicity to induce the SLE-like syndrome.

CONCLUSIONS

Our study provides direct evidence showing that DNA hypomethylation is essential for apoptotic DNA to induce SLE-like autoimmune disease in non-susceptible mice, which may help in elucidating the pathogenesis of SLE.

Expression of axl in lung adenocarcinoma and correlation with tumor progression

We used the Transwell system to select highly invasive cell lines from minimally invasive parent cells, and we compared gene expression in paired cell lines with high and low invasive potentials. Axl was relatively overexpressed in the highly invasive cell lines when compared with their minimally invasive counterparts. However, there is only limited information about the role of Axl in cancer invasion. The biologic function of Axl in tumor invasion was investigated by overexpression of full-length Axl in minimally invasive cells and by siRNA knockdown of Axl expression in highly invasive cells. Overexpression of Axl in minimally invasive cells increased their invasiveness. siRNA reduced cell invasiveness as Axl was downregulated in highly invasive cells. We further investigated the protein expression of Axl by immunohistochemistry and its correlation with clinicopathologic features. Data from a study of 58 patient specimens showed that Axl immunoreactivity was statistically significant with respect to lymph node status (P < .0001) and the patient's clinical stage (P < .0001). Our results demonstrate that Axl protein kinase seems to play an important role in the invasion and progression of lung cancer.

Induction of systemic lupus erythematosus-like syndrome in syngeneic mice by immunization with activated lymphocyte-derived DNA

OBJECTIVES

Systemic lupus erythematosus (SLE) is the prototype of autoimmune disease and the mechanisms underlying the disease have not yet been elucidated. Thus, animal models of SLE would facilitate investigation of pathogenetic mechanisms involved in the development of the disease. This study characterizes a murine model of SLE-like syndrome induced by syngeneic activated lymphocyte-derived DNA (referred to as ALD DNA).

METHODS

Normal BALB/c mice were immunized subcutaneously with highly purified ALD DNA. Anti-double-stranded DNA (anti-dsDNA) antibodies were determined by enzyme-linked immunosorbent assay. Other SLE-associated autoantibodies were examined by indirect immunofluorescence and anti-ENA (extractable nuclear antigen) profile assay. Pathological changes were analysed by light microscopy and electron microscopy. Kidney cryostat sections were viewed by immunofluorescence for the presence of glomerular IgG and C3 deposits. Proteinuria was measured by Coomassie brilliant blue assay.

RESULTS

High levels of anti-dsDNA antibodies and other autoantibodies frequently appearing in SLE were detectable in the sera of ALD DNA-immunized mice. Glomerulonephritis and glomerular deposition of IgG plus C3 were observed in the kidney sections. Moreover, proteinuria was seen in the immunized mice.

CONCLUSIONS

SLE-like syndrome can be induced by ALD DNA in normal mice. This induced model may be useful for elucidating the mechanisms involved in autoimmunity to DNA and the development of SLE.

Prognosis of non-small cell lung cancer patients by detecting circulating cancer cells in the peripheral blood with multiple marker genes

PURPOSE

Current lung cancer staging and prognosis methods are based on imaging methods, which may not be sensitive enough for early and accurate detection of metastasis. This study aims to validate the use of a panel of markers for circulating cancer cell detection to improve the accuracy of cancer staging, prognosis, and as a rapid assessment of therapeutic response.

EXPERIMENTAL DESIGN

We analyzed the National Cancer Institute-Cancer Genome Anatomy Project database to identify potential marker genes for the detection of circulating cancer cells in peripheral blood. Nested real-time quantitative PCR and a scoring method using cancer cell load Lc were employed to correlate the amount of circulating cancer cells with clinical outcomes in 54 non-small cell lung cancer (NSCLC) patients. The Kaplan-Meier method was employed for analysis of prognostic variables.

RESULTS

A panel of four marker genes was identified and experimentally validated. With these marker genes, we achieved an overall positive detection rate of 72% for circulating cancer cells in the peripheral blood of NSCLC patients. Patients who had higher Lc values had worse outcomes and shorter survival times. Patients with poor therapeutic response were revealed by positive detection of circulating cancer cells after therapy. The results correlated well with the patients' survival time.

CONCLUSION

Circulating cancer cell detection by a panel of markers and the Lc scoring method can supplement the current tumor, node, metastasis staging method for improved prognosis and for rapid assessment of therapeutic response. Together, they may facilitate the design of better therapeutic strategies for the treatment of NSCLC patients.

Role of angiogenic and non-angiogenic mechanisms in oral squamous cell carcinoma: correlation with histologic differentiation and tumor progression

BACKGROUND

Angiogenesis has been demonstrated to associate with various measures of tumor aggressiveness in many human malignancies. However, studies of tumor angiogenesis in oral squamous cell carcinoma (SCC) are still unclear. Recent studies indicate non-angiogenesis mechanism (tumor-lined vessel) may exist in certain tumors. Therefore, we investigate microvessel density (MVD) and tumor-lined vessel in oral SCC.

METHODS

Peritumoral and intratumoral MVD were measured by immunohistochemical staining. Tumor-lined vessels were identified by double staining. Statistical analysis of peritumoral and intratumoral MVD and presence of tumor-lined vessels with clinicopathologic parameters was performed.

RESULTS

The results showed peritumoral MVD increased with disease progression and further increases of intratumoral MVD was detected by CD31 and CD34. Non-angiogenesis, tumor-lined vessel, presented in oral SCC and correlated significantly with tumor size, stage, and histologic differentiation.

CONCLUSION

Our results suggest at the initiation of oral SCC, increasing vascularity is observed at the periphery of the tumor. As the tumor continues to grow, further increases of intratumoral vascularity and the presence of tumor-lined vessels are associated with cancer progression.

Tumor-associated antigen L6 and the invasion of human lung cancer cells

Metastasis is a coordinated process that depends on the interaction of cancer cells with the tumor microenvironment. Members of the transmembrane-4 superfamily (TM4SF) of surface proteins have been implicated in the regulation of cancer cell metastasis, and the expression of several TM4SF members on tumor cells is inversely correlated with patient prognosis. The tumor-associated antigen L6 (TAL6), a distant member of the TM4SF, is expressed on most epithelial cell carcinomas and is a target for antibody-mediated therapy. We examined whether TAL6 may play a role in cancer metastasis by using an established series of human lung carcinoma cell lines (CL1-0 to CL1-5) that exhibit increasing invasiveness in vitro and in vivo. We found that TAL6 expression correlated with the in vitro invasiveness of CL lung carcinoma cells (r(2) = 0.98) and human carcinoma cells (r(2) = 0.69). Forced expression of TAL6 on CL1-0 lung carcinoma cells significantly increased their in vitro invasiveness and decreased the survival of SCID mice in an experimental metastasis model. Specific antibody against TAL6 (monoclonal antibody L6) significantly reduced the migration and invasiveness of CL1-5 lung carcinoma cells. The effects of monoclonal antibody L6 on CL1-5 invasion required clustering of TAL6 on the cell surface. Real-time reverse transcription-PCR of lung cancer specimens showed that increased expression of TAL6 was significantly associated with early postoperative relapse (P = 0.034) and shorter survival (P = 0.025) in squamous cell lung cancer patients. Thus, TAL6 appears to be involved in cancer invasion and metastasis.

Shortening of microsatellite deoxy(CA) repeats involved in GL331-induced down-regulation of matrix metalloproteinase-9 gene expression

Matrix metalloproteinase-9 (MMP-9) associates with cancer cell invasion and metastasis. CL1-5 cells, a human lung adenocarcinoma cell line, expressed an elevated level of MMP-9 and exhibited a highly invasive and metastatic ability. By Matrigel assay and gelatinase zymography, the topoisomerase II poison GL331 was found to dose-dependently inhibit the invasiveness and the level of secreted MMP-9 of CL1-5 cells. Northern blot analysis indicated that cellular MMP-9 mRNA level was decreased after GL331 treatment. Furthermore, GL331-induced down-regulation of mmp-9 gene promoter was demonstrated by using a luciferase reporter gene driven by the -216 to -13 region of the mmp-9 gene promoter cloned from CL1-5 cells. By PCR amplification and gel electrophoresis, we found that GL331 caused shortening of the -216 to -13 region of the mmp-9 promoter. Direct sequencing analysis revealed that the number of d(CA) was reduced from 24 to 18 at the microsatellite d(CA) repeat region of the mmp-9 promoter. The CL1-5 cells transfected with the luciferase reporter containing 18 d(CA)s expressed only 53% of those when the reporter contained 24 d(CA)s. The promoter region of mmp-9 gene contains other positive regulatory elements, such as TRE and kappaB. We found that GL331 did not significantly influence the luciferase activity driven by TRE or kappaB. Taken together, these data suggested that GL331 inhibited MMP-9 mRNA expression at least partly through the selective induction of shortening of microsatellite d(CA) repeats. This is the first report that an anti-cancer agent can inhibit mmp-9 gene expression by inducing microsatellite DNA shortening.

IMP-4, a novel metallo-beta-lactamase from nosocomial Acinetobacter spp. collected in Hong Kong between 1994 and 1998

Between 1994 and 1998, 97 imipenem-resistant Acinetobacter isolates were identified at the Prince of Wales Hospital, Hong Kong, China. A bla(IMP) PCR product was obtained from 23 of 35 viable cultures; 12 isolates belonged to genomic DNA group 3, 8 belonged to group 2 (Acinetobacter baumannii), 2 belonged to group 13TU, and 1 belonged to group 1. The bla(IMP) homologues were sequenced from two isolates from genomic DNA group 2 and one isolate each from groups 3 and 13TU. The four sequences included an identical 738-bp open reading frame, predicted to encode a polypeptide of 246 amino acids, with 95.6% homology to IMP-1 and 89.3% homology to IMP-2. The new enzyme, designated IMP-4, was partially purified. It had a pI of 8.0 and was strongly active against imipenem and meropenem, with V(max) values 53 and 8% of that for penicillin G, respectively. Strong activity was also seen against oxyimino-aminothiazolyl cephalosporins but not against aztreonam. Hydrolytic activity was inhibited by EDTA but not by clavulanate or tazobactam. Carbapenem MICs for most bla(IMP)-positive isolates were 4 to 32 microg/ml, but one isolate with the intact gene was susceptible, with imipenem and meropenem MICs of 0.25 and 0.5 microg/ml, respectively. The latter isolate did not produce the band with a pI of 8.0, and gene expression was inferred to have been lost. None of the isolates studied in detail contained extrachromosomal DNA, and carbapenem resistance was not transmissible to Escherichia coli. Nevertheless, the presence of bla(IMP-4) in different genomic DNA groups implies horizontal transfer, and sequences resembling a GTTRRRY integrase-dependent recombination motif were identified in the flanking regions of bla(IMP-4).

Epidemiology and infection control implications of Acinetobacter spp. in Hong Kong

In a previous study, we showed that Acinetobacter genomic DNA group 3 was the most common species among blood culture isolates and was commonly found on superficial carriage sites of the healthy and the sick, which are different findings from those reported in Europe and North America. We used amplified ribosomal DNA restriction analysis and pulsed-field gel electrophoresis to study further the molecular epidemiology of acinetobacters in our region. Over a study period of 6 weeks with 136 consecutive routine clinical isolates (1.33% of all specimens), genomic DNA groups 2 (Acinetobacter baumannii), 3, and 13TU were obtained from 59 of 69 positive patients. There is a significant difference in the specimen sources of the three genomic DNA groups, with group 13TU being significantly associated with the respiratory tract (chi-square exact test, P = 0.0064). Settle plates showed a significantly heavier environmental load from the intensive care unit (ICU) than from the four surgical wards examined (22 of 70 versus 76 of 120 plates with <5 colonies; chi-square test, P < 0. 0001). Genomic group 3 accounted for 6 of 12 clusters of possibly related strains among patients, between patients and the ICU environment, and in the ICU environment. Genomic groups 2 and 3 accounted for 21% of the 132 genomically identified isolates recovered from 21 of 41 local vegetables, 53 of 74 fish and meat samples, and 22 of 60 soil samples. Group 13TU was present only in patients' immediate surroundings. The role played by the environment and by human carriage should be evaluated in order to devise a cost-effective infection control program pertinent to our situation of acinetobacter endemicity.

Skin carriage of acinetobacters in Hong Kong

We studied the carriage of Acinetobacter spp. at five superficial sites in 79 patients from two hospitals, in 133 healthy controls from the community (medical students and new nurses), and in 198 student nurses in different classes. A total of 431 isolates from 364 positive sites of 201 subjects and 124 blood culture isolates (1997 to 1998) were genospeciated by amplified ribosomal DNA restriction analysis. Genospecies 3 was the most common species. The carriage rate of student nurses (42 of 131) was significantly lower than that of new nurses from the community (25 of 38) (chi-square test, P = 0.0004; odds ratio [OR], 4.08; 95% confidence limits, 1.78 to 9.41) but not significantly different (P = 0.1) from that of patients in the same hospital (20 of 42). Genospecies from blood cultures and subjects (acute patients and student nurses) from Prince of Wales Hospital were similar to one another but different from subjects from the community or from another hospital (chi-square test, P < 0.0001). Half of the subjects who were positive at at least two sites had different genospecies. Of the 28 sites examined, 68% showed strain variation among isolates of the same genospecies by random amplified polymorphic DNA analysis. Half of the 106 subjects who had samples taken again within 6 weeks or 6 months later were positive only once. In the 17 subjects who were positive on at least two occasions, each occasion yielded different genospecies in 13 subjects. Our results indicate that skin carriage in the majority of healthy subjects is characterized by low density, variation in genospecies and strains, short-term duration, and the typicality of a given locality.

Analysis with flow cytometry of green fluorescent protein expression in leukemic cells

BACKGROUND

The measurement of DNA content with propidium iodide (PI) in cells transfected with expression vectors encoding the green fluorescent protein (GFP) is a useful tool in studying a variety of biological functions of proteins within cells. The purpose of this study was to determine conditions of formaldehyde fixation that permit intracellular GFP fluorescence and adequate DNA histograms to be generated following transient transfection of cells with a GFP-encoding plasmid. Cell cycle analysis was also performed in GFP-positive cells.

METHODS

The murine myeloid leukemic cell line, 32Dcl3, was used as the model system. Cells were transfected with a GFP-encoding plasmid (pEGFPC1). Following fixation in different formaldehyde concentrations and permeabilization with 70% ethanol, cells were stained with PI and analyzed by flow cytometry for GFP fluorescence and DNA content. Transfected cells were also analyzed for GFP fluorescence and DNA content following release from nocodazole block.

RESULTS

Fixing cells in 0.51-1.75% formaldehyde concentrations prior to ethanol permeabilization resulted in 14-19% of transfected cells being GFP-positive, with acceptable coefficients of variation on the G(1) peak of DNA histograms. Analysis of cells synchronized to and released from the G(2)-M phase by nocodazole suggested that GFP-positive cells, when compared to GFP-negative cells, did not appear to progress out of G(2)-M following release from nocodazole block. Simultaneous detection of GFP fluorescence and DNA content by PI staining is possible following transient transfection of cells with a single expression vector encoding GFP. Our results demonstrate that GFP expression can be detected, using flow cytometry to perform cell cycle analysis in murine leukemic cells.

Profiling expression patterns and isolating differentially expressed genes by cDNA microarray system with colorimetry detection

A high-density cDNA microarray with colorimetry detection system to simultaneously monitor the expression of many genes on nylon membrane is described and characterized. To quantify the expression of genes and to isolate differentially expressed genes, the southern hybridization process on filter membranes was employed. The levels of gene expression were represented by color intensities generated by colorimetric reactions in place of hazardous radioisotopes or costly laser-induced fluorescence detection. The gene expression patterns on nylon membranes were digitized by devices such as an economical flatbed scanner or a digital camera. The quantitative information of gene expression was retrieved by image analysis software. Quantitative comparison of the northern dot-blotting method with the microarray system is described. Applications employing single-color detection as well as dual-color detection to isolate differentially expressed genes among thousands of genes are demonstrated.

Antimicrobial resistance in Shigella flexneri and Shigella sonnei in Hong Kong, 1986 to 1995

Three hundred and thirty-three Shigella isolates obtained in 1986 to 1995 were tested for their susceptibilities to 19 antimicrobial agents. Nalidixic acid resistance had emerged in 59.6% of Shigella flexneri isolates during 1994 to 1995, with all tested resistant isolates having the mutation in gyrA encoding the Ser-83 alteration. Multiresistance (resistance to four or more agents) was more common in S. flexneri than in Shigella sonnei.

Selection of invasive and metastatic subpopulations from a human lung adenocarcinoma cell line

To better understand the mechanism(s) underlying lung cancer invasion and metastasis, a Transwell invasion chamber was used to select progressively more invasive cancer cell populations from a clonal cell line of human lung adenocarcinoma, CL1. Five sublines with progressive invasiveness, designated CL1-1, CL1-2, CL1-3, CL1-4, and CL1-5, were obtained through this in vitro selection process. Their invasive abilities through basement membrane matrix showed a 4- to 6-fold increase over that of the parental cells. Moreover, the sublines manifested an increase in their colony-forming ability on soft agar, tumorigenicity, and metastatic potency in severe combined immunodeficiency (SCID) mice. Examining the phenotypes of the cell lines revealed increased expression of 92 kD gelatinase and an increase in the cell population stained with anti-keratin-8 and -18 antibodies. Clonal isolation of anti-keratin-18-antibody-positive and -negative cell populations demonstrated a correlated enhancement of the invasiveness of these cells and their expression of keratin-18. These results support the notion that the metastatic behavior of lung cancer cells can be characterized with this in vitro system, and that the properties of these progressively invasive cancer cells can be clonally studied.

Extracellular pH affects regulation of the pcbAB gene in Penicillium chrysogenum

The effect of extracellular pH and dissolved oxygen on regulation of the pcbAB gene in P. chrysogenum was examined, using Northern analysis and a reporter gene fusion. It was found that ambient pH markedly affected levels of pcbAB mRNA whereas maintenance of dissolved oxygen concentration above 10% had no detectable effect. The presence of a DNA-binding protein, which binds upstream of the pcbAB translational start codon, was also related to ambient pH. In all fermentations, pcbAB mRNA was most abundant at around the late exponential/early stationary phase of a culture.

Role of intermediate filaments in migration, invasion and metastasis

The expression of intermediate filament proteins is remarkably tissue-specific which suggests that the intermediate filament (IF) type(s) present in cells is somehow related to their biological function. However, in some cancers-particularly malignant melanoma and breast carcinoma, there is a strong indication that vimentin and keratin IFs are coexpressed, thus presenting as a dedifferentiated or interconverted (between epithelial and mesenchymal) phenotype. In this review, two in vitro models are presented which recapitulate the interconverted phenotype in human melanoma and breast carcinoma, and allow, for the first time, unique observations to be made with respect to the role of IFs in cancer progression. These studies have provided direct evidence linking overexpression of keratin IFs in human melanoma with increased migratory and invasive activity in vitro, which can be down-regulated by substituting dominant-negative keratin mutants. Overexpression of vimentin IFs in the breast carcinoma model leads to augmentation of motility and invasiveness in vitro, which can be transiently down-regulated by treatment with antisense oligonucleotides to vimentin. Additional experimental evidence suggests that the mechanism(s) responsible for the differential expression of metastatic properties associated with the interconverted phenotype rest(s) in the unique interaction, either direct or indirect, of IFs with specific integrins interacting with the extracellular matrix. In this review, we discuss the observations derived from the human melanoma and breast carcinoma models to address the hypothesis that the ability to coexpress vimentin and keratins confers a selective advantage to tumor cells in their interpretation of and response to signaling cues from the extracellular matrix. The ramifications of these observations are discussed with respect to the patholophysiology of the respective in situ tumors.

Factors affecting DNA-binding proteins and pcbC transcript levels in Penicillium chrysogenum

Proteins extracted from Penicillium chrysogenum grown in either complex or defined medium were used in electromobility shift assays. With a probe DNA covering the region -10 to -132 relative to the pcbC translation start codon, four protein/DNA complexes (designated A-D) were reproducibly observed. Two of the four DNA/protein complexes routinely detected in extracts from liquid cultures (A and B) were also detectable with protein extracts from P. chrysogenum spores. Generally, with proteins from liquid cultures, there was a correlation between increased levels of the complexes and increased levels of the pcbC transcript. In addition, the detectable levels of the complexes and the pcbC transcript showed some relationship to the extracellular pH of the medium. In defined medium, with glucose as the carbon source, the pcbC transcript was not detectable in extracts from the wild-type strain at any time, whereas with the high penicillin-producing strain P-2, a pcbC transcript was detected. In complex medium, the pcbC transcript was detectable during the exponential phase of cultures of the wild-type or P-2, even when glucose levels were as high as 2.5% (w/v).

Acidic pH enhances the invasive behavior of human melanoma cells

As a consequence of poor perfusion and elevated acid production, the extracellular pH (pHex) of tumors is generally acidic. Despite this, most in vitro experiments are still performed at the relatively alkaline pHex of 7.4. This is significant, because slight changes in pHex can have profound effects on cell phenotype. In this study we examined the effects of mildly acidic conditions on the in vitro invasive potential of two human melanoma cell lines; the highly invasive C8161, and poorly invasive A375P. We observed that culturing of either cell line at acidic pH (6.8) caused dramatic increases in both migration and invasion, as measured with the Membrane Invasion Culture System (MICS). This was not due to a direct effect of pH on the invasive machinery, since cells cultured at normal pH (7.4) and tested at acidic pH did not exhibit increased invasive potential. Similarly, cells cultured at acidic pH were more aggressive than control cells when tested at the same medium pH. These data indicate that culturing of cells at mildly acidic pH induces them to become more invasive. Since acid pH will affect the intracellular pH (pHin) and intracellular calcium ([Ca2+]in), we examined the effect of these parameters on invasion. While changes in [Ca2+]in were not consistent with invasive potential, the changes in pHin were. While these conditions decrease the overall amount of gelatinases A and B secreted by these cells, there is a consistent and significant increase in the proportion of the activated form of gelatinase B.

Experimental coexpression of vimentin and keratin intermediate filaments in human melanoma cells augments motility

Intermediate filaments have been used as cell-type-specific markers in differentiation and pathology; however, recent reports have demonstrated the coexpression of vimentin (a mesenchymal marker) and keratins (epithelial markers) in numerous neoplasms, including melanoma, which has been linked to metastatic disease. To test the hypothesis that coexpression of vimentin and keratins by melanoma cells contributes to a more migratory and invasive phenotype, we co-transfected a vimentin-positive human melanoma cell line, A375P (of low invasive ability), with cDNAs for keratins 8 and 18. The resultant stable transfectants expressed vimentin- and keratin-positive intermediate filaments showed a two- to threefold increase in their invasion of basement membrane matrix and migration through gelatin in vitro. These findings were further corroborated by video cinematography. During attachment and spreading on fibronectin, the transfectants containing vimentin and keratins 8 and 18 demonstrated an increase in focal adhesions that stained positive for beta 1 integrin and phosphotyrosine, along with enhanced membrane ruffling and actin stress fiber formation. From these data, we postulate that coexpression of vimentin and keratins results in increased cytoskeletal interactions at focal contacts within extracellular matrices involving integrin cell signaling events, which contributes to a more migratory behavior.

Detection of a protein which binds specifically to the upstream region of the pcbAB gene in Penicillium chrysogenum

The upstream region of the pcbAB gene from Penicillium chrysogenum was screened for protein-binding sites using an electromobility shift assay. A specific protein/DNA interaction was detected within a fragment covering the region -387 to -242 relative to the pcbAB translational start codon. The appearance of this protein and pcbAB mRNA in culture extracts occurred at the same time point in fermentations, suggesting that the protein might be a transcription activator. The putative upstream activating sequence was located more precisely using cross-competition assays. These indicated the involvement of the 7-bp motif TGCCAAG in the binding of the protein.

Somatic mutation of human immunoglobulin V genes in the X-linked HyperIgM syndrome

Somatic mutation of Ig variable regions occurs prominently in germinal centers, but it has been debated whether the mutation process initiates in germinal centers or is activated before germinal center entry of B cells. We have analyzed for the presence of somatic mutation in Ig gene rearrangements of the nonpolymorphic human VH6 gene in the X-linked HyperIgM syndrome, which is associated with defective CD40 ligand expression and absence of germinal centers and generation of memory B lymphocytes. IgM and rare IgG VH6 productive rearrangements were isolated from PBL of patients with X-linked HyperIgM syndrome. Although the majority of both the IgM and IgG VH6 rearrangements had a germline VH6 sequence, 7 of 102 VH6 IgM and 1 of 6 IgG rearrangements had a mutated VH6 gene. The mutation frequency (mutations/bp) was 1.4% with a range of 2-9 mutations per clone, a mutation frequency lower, however, than that observed in IgM (3.2%) and IgG (5.4%) VH6 rearrangements of normal individuals. These results suggest that somatic mutation may be initiated in a CD40 ligand-independent pathway before entry of B cells into germinal centers, but fails to achieve the high mutation frequency observed in the presence of germinal centers.

v-jun oncogene suppresses both phorbol ester-induced cell invasion and stromelysin gene expression in a mouse papilloma cell line

The viral jun (v-jun) oncogene encodes a transcription factor that can participate in the transactivation of genes through the AP-1 complex. Evidence indicates that the ability of v-jun to transform cells and stimulate transcription depends on the cell type. We have asked whether expression of the v-jun gene in benign tumor forming mouse keratinocytes that already express an activated c-rasHa oncogene would cause malignant progression. Our results showed that the v-jun transfection did not result in malignant progression; instead, we made the unexpected observation that the ability of these cells to invade reconstituted basement membrane matrix (in vitro) in response to the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate, was suppressed. This phenomenon could, in part, be explained by the suppression of the induction by phorbol ester of expression of the metalloproteinase, stromelysin (transin). Of interest was the finding that 12-O-tetradecanoylphorbol-13-acetate induction of other cellular genes known to be regulated by AP-1 was not inhibited in the benign tumor cells expressing v-jun.

Expression of complete keratin filaments in mouse L cells augments cell migration and invasion

Intermediate filament proteins have been used to diagnose the origin of specific cells. Classically, vimentin is found in mesenchymal cells, and keratins are present in epithelial cells. However, recent evidence suggests that the coexpression of these phenotype-specific proteins augments tumor cell motility, and hence, metastasis. In the present study, we used the mouse L-cell model to determine if a direct correlation exists between the expression of additional keratins in these cells, which normally express only vimentin, and their migratory ability. Mouse L cells were transfected with human keratins 8, 18, and both 8 and 18. The results indicate that the cells expressing complete keratin filaments have a higher migratory and invasive ability (through extracellular matrix-coated filters) compared with the parental and control-transfected clones. Furthermore, there is an enrichment of keratin-positive cells from a heterogeneous population of L clones selected over serial migrations. This migratory activity was directly correlated with the spreading ability of the cells on Matrigel matrix, in which the keratin-positive transfectants maintain a round morphology for a longer duration, compared with the other L-cell populations. Collectively, these data suggest that keratins may play an important role(s) in migration, through a special interaction with the extracellular environment, thereby influencing cell shape.

Coexpression of vimentin and keratins by human melanoma tumor cells: correlation with invasive and metastatic potential

BACKGROUND

Several protein markers, including vimentin, have been used to diagnose human melanoma. Because melanoma often has metastasized by the time of diagnosis, early markers prognostic for metastatic potential need to be identified. Commonly, vimentin is found in mesenchymal cells, and keratins are present in epithelial cells, but recent studies report coexpression of vimentin and keratin(s) in epithelial and nonepithelial neoplasms, including some melanomas.

PURPOSE

Our purpose was to determine whether coexpression of vimentin and keratin(s) is correlated with tumor cell invasion and metastatic behavior.

METHODS

We evaluated nine human melanoma cell lines expressing vimentin and other markers of aggressive tumor behavior (HMB-45, S-100, HLA-ABC class I and HLA-DR class II histocompatibility antigens, and K8 and K18 keratins). Levels of K8 and K18 keratins were determined in the highly metastatic C8161 cell line, the poorly metastatic A375P line, and the moderately metastatic A375M line. To determine whether the presence of keratin affects migratory ability, we altered the conformational structure of keratin filaments in C8161 cells by transfection with a mutant K18 complementary DNA. We also determined messenger RNA levels of human type IV collagenase, an enzyme marker for invasion and metastasis.

RESULTS

In A375P cells, two-dimensional electrophoresis with Coomassie-stained gels, immunoblotting, and immunofluorescence staining showed no detectable levels of K8 or K18. A375M cells showed low levels of K8 and K18 by Western and Northern blotting, with a distinctive fluorescent subpopulation of cells. In comparison, K8 and K18 levels in C8161 cells were high in all cells. Type IV collagenase messenger RNA levels were lowest in A375P cells and highest in C8161 cells, correlating with invasive ability in vitro and metastatic potential in athymic nude mice. The transfectant clones C1070-10 and C1070-14 derived from the C8161 parent line showed dramatic morphological changes, disrupted keratin filaments, and decreased invasive and metastatic potential directly correlated with a reduction in migratory activity.

CONCLUSION

These findings show a correlation between the coexpression of vimentin with K8 and K18 keratins and the invasive and metastatic behavior of three representative human melanoma cell lines.