Standardization of the immunocytochemical detection of cancer cells in BM and blood: I. establishment of objective criteria for the evaluation of immunostained cells

BACKGROUND

Detection of isolated tumor cells (TC) in BM from carcinoma patients can predict future relapse. Various molecular and immunocytochemical (ICC) methods have been used to detect these cells, which are present at extremely low frequencies of 10(-5) - 10(-6). The specificity and sensitivity of these techniques may vary widely. In 1996, a European ISHAGE Working Group was founded to standardize and optimize procedures used for the detection of minimal residual disease. We have attempted to develop objective criteria for the evaluation of immunocytochemically identifiable cancer cells.

METHODS

An interlaboratory ring experiment was performed, to compare the screening and detection of micrometastasis-positive events between different laboratories. The discrepant results induced us to establish a common consensus on morphological criteria applicable to the identification of immunostained micrometastatic TC.

RESULTS

Bared on this consensus evaluation, we propose a classification of stained elements into three groups: (1) 'TC's show pathognomonic signs of epithelial TC-nature, as defined by a clearly enlarged nucleus or clusters of > or = 2 immunopositive cells. (2) 'Probable TC's represent morphological overlap between hematopoietic cells (HC) and TC which lack pathognomonic signs of TC-nature, but do not exhibit clear morphological features of HC. These cells are considered as TC if control staining with an isotype-specific, unrelated Ab is negative. (3) 'TC-negative' cells are defined as 'false positive' HC, skin squamous epithelial cells and artefacts.

DISCUSSION

The proposed classification of immunostained events is a first step towards the development of standardized immunocytochemical assays for the detection of occult micrometastatic TC in BM or blood.

Synergistic antitumor efficacy and altered gene expression signature in breast cancer cells treated with immunotoxins and cyclosporin A

13505

Background: Immunotoxins (ITs) has shown limited clinical success related to liver toxicity and development of anti-IT antibodies. To delay the immune response we tested combinations of ITs and the Cyclosporin A (CsA). we have shown that one IT, currently in a phase I/II clinical trial, acts by inducing apoptosis and protein synthesis inhibition, but gene expression analysis of IT treated cells has never been reported. Hence, we also studied changes in gene expression induced by ITs alone and the effects of adding (CsA) on both treatment efficacy and gene expression signature. Methods: Human MA-11 breast cancer cells were treated in vitro with antiEGFR- and antiEPCAM-based ITs alone and in combinations with CsA. Therapeutic efficay was assessed by MTS cell viability assay. Total RNA from untreated and treated cells was isolated and CodeLink Uniset Human 20 k Oligo Bioarray (GE Healthcare, Amersham Biosciences, NJ), containing approximately 20,289 gene probes, was used to generate gene expression profiles. Gene expression analysis was carried out using GeneSpring software version 7.2 using One-way ANOVA with p<0.05. Comparisons of gene list across different groups were performed using Venn Diagrams. Results: Combination therapy produced remarkable synergistic effects in MA-11 cells in vitro and in metastasis models in vivo. Moreover, in conventional rats receiving repeated injections of ITs and CsA the formation of anti-IT antibodies was virtually abrogated. Changes in gene expression profiles induced by the ITs alone and in combination with CsA were evaluated to elucidate the underlying molecular mechanisms for the synergistic effects. The ITs each induced specific changes in expression of some apoptosis-related genes but also fogenes in pathways unrelated to apoptosis and protein synthesis. The addition of CsA induced up- or down-regulation of a number of interesting non-immune-associated genes Conclusions: Important shortcomings for successful clinical use of ITs may be overcome by combination therapy with CsA. The possibility for further improvement is provided by results of gene profiling studies identifying therapy-induced genes belonging to different cell signaling pathways.

No significant financial relationships to disclose.

COM-1 is over-expressed in human colorectal carcinomas

21001

Background: COM-1, candidate of metastasis-1, is a primarily nuclear protein thought to play a role in the development and maintenance of metastatic tumours and to have some mitogenic activity. However subsequent investigations have demonstrated a much more diverse role in cancer and cell growth. Here we have investigated the expression and sub-cellular distribution patterns of COM-1 in human colorectal carcinomas. Methods: Carcinoma and normal matched tissues were collected following surgery and frozen for future analysis. Sections of tissue underwent immuno-histochemistry (IHC) staining for COM-1 to determine degree of staining and changes in cellular distribution of the proteins within the tissue. Furthermore, quantitative analysis (quantitative polymerase chain reaction - qPCR) of mRNA levels of COM-1 transcripts was performed to compare levels in normal tissue with those in carcinoma tissues. Statistical analysis was by the Mann-Whitney test. Results: IHC -Normal tissue demonstrated strong nuclear staining for COM-1 protein with little or no cytoplasmic staining. In carcinoma tissue the level of overall staining was found to be much greater, with a greater degree of cytoplasmic staining and little evidence of nuclear staining. qPCR- COM-1 mRNA expression within cells was significantly higher within tumour tissue when compared to normal tissue (Mean 36.7 v 26.5, p=0.003). Moreover, there was a trend in increasing levels of expression and significance of difference between normal tissue and carcinoma tissue with increasing Dukes stage (A p=.52, B p=0.03, C p=0.03) , T-Stage (1 p=1.0, 2 p=0.69, 3 p=0.04, 4 p=0.03), Nodal status (−ve p=0.07, +ve p=0.04 and tumour differentiation (well diff p=0.91, Mod. Diff p= 0.06, Poor. Diff. p= 0.026). Conclusions: COM-1 expression is increased in colorectal tumour tissues when compared to normal mucosa. This is reflected at both the protein and mRNA levels within the cells. In addition there is evidence of dislocated expression and redistribution of COM-1 protein with normal protein expression remaining intra-nuclear however, in tumours COM-1 then becomes cytoplasmic. Aberant over-expression of COM-1 has been identified in other human carcinoma types and has been linked with advanced disease, here we have demonstrated a similar pattern in colorectal carcinomas.

No significant financial relationships to disclose.

Clinically proven markers of metastasis predict metastatic spread of human melanoma cells engrafted in scid mice

Metastasis formation is a complex process and as such can only be modelled in vivo. As markers indicating metastatic spread in syngenic mouse models differ significantly from those in man, this study aimed to develop a human melanoma xenograft mouse model that reflects the clinical situation. Six human melanoma cell lines (LOX, MV3, FEMX-1, G361, MeWo and UISO-Mel6) were xenografted into severe combined immunodeficient mice and tumour growth, metastatic behaviour and number of lung metastases were assessed. Tumours and metastases were analysed for HPA binding and expression of CEACAM-1 and L1, all markers indicative of metastasis in clinical studies. Development of primary tumour nodules ranged from 3 weeks (MV3) to 3 months (MeWo). Whereas G361 and FEMX-1 rarely formed lung metastases, MeWo, MV3 and LOX were moderately and UISO-Mel6 was highly metastatic. Similar to clinical studies, HPA, CEACAM1 and L1 indicated metastatic spread in the xenograft melanoma model, but were not all simultaneously expressed in all cell lines. Considering the strongest expression of one marker combined with an absent or low expression of the other two markers, we conclude that LOX is the cell line of choice for analyses of the functional role of HPA-binding glycoconjugates, UISO-Mel6 is ideally suited to study CEACAM1 function in melanoma spread and L1 function can best be modelled using MeWo.

Chemo-response biomarker discovery via expression profiling using soft-tissue sarcoma xenografts

9569

Background: Soft-tissue sarcoma (STS) constitute a heterogeneous group of tumours of mesenchymal origin. Whereas the mainstay of treatment has been surgery and radiation, these tumours are generally considered as quite chemoresistant. However, it is well known that subgroups of patients benefit from chemotherapy. Markers that could predict drug response would therefore be beneficial for the management of this malignancy. We have previously established panel of 17 unique human soft tissue xenografts, representing 7 different histological subgroups and assessed their responsiveness to doxorubicin, ifosfamide, etoposide, and cisplatin. We wanted to utilize these xenografts as a model system to discover for novel candidate marker genes for STS chemo-response. Methods: GE Uniset Human 20K microarrays were used to obtain gene expression profiles from the each xenografts. One-way ANOVA test with a Benjamini-Hochberg multiple test correction allowing a false discovery rate of 5% was used to identify genes with significantly differential expression. Results: Doxorubicin, ifosfamide, etoposide and cisplatin were efficient in 6/17, 10/17, 1/17 and 7/17 xenografts respectively. However, in the expression profiles obtained none of the genes showed significantly correlation with chemo-responsiveness to any of the drugs. Two of the xenografts, TAX 1 and TAX 2, both originate from a malignant fibrous histiocytoma (MFH) in the same patient, but show strikingly different sensitivity to ifosfamide (TAX1 resistant, TAX2 sensitive). When triplicate hybridizations of TAX1 and 2 were compared, 294 genes met the above criteria. In addition we identified a subset of 122 genes that were flagged absent in one of the specimens, present in the other. Among genes with an already described role in mediating drug resistance are GST-pi and glutathione peroxidase. Taken together, these results indicate that discovery of general response markers in STSs may be difficult due to the heterogeneity of the different subgroups constituting this malignancy. Conclusions: Gene expression profiling of the TAX 1 and TAX 2 xenografts revealed a number of interesting candidate marker genes for ifosfamide sensitivity of MFH. This list of genes will be further refined by validation in clinical samples.

No significant financial relationships to disclose.

Gene expression profiles classifies the responsiveness of human osteosarcoma to doxorubicin, cisplatin and ifosfamide

9534

Background: Despite the increased survival rates of osteosarcoma patients attributed to adjuvant chemotherapy, at least one third of the patients still succumb to their disease. Furthermore, ultra-aggressive combination chemotherapy is associated with considerable acute and long term toxicity. This is of particular concern in patients who may be cured by a simpler and less toxic regimens or do not have micrometastatic disease. Hence, further improvements in the management of osteosarcoma seemingly depend on diagnostic and prognostic tools that may allow for a more risk adapted and individualized treatment. Methods: We have used GE Uniset Human 20K microarrays to obtain gene expression profiles from a panel of ten unique human osteosarcoma xenografts. For each of the three drugs doxorubicin, cisplatin or ifosfamide the xenografts were grouped according to their response to chemotherapy, resistant, weakly sensitive or sensitive. For each individual drug, a one-way ANOVA test with a Benjamini and Hochberg multiple test correction allowing a false discovery rate of 5% (doxorubicin, cisplatin) or 2% (ifosfamide) was used to identify genes with significantly differential expression. In addition a 2-fold cut off was applied to exclude smaller but yet significant differences. Results: For doxorubicin and cisplatin, respectively 59 and 120 genes met these criteria. The expression levels of 25 genes overlapped between these two groups. For ifosfamide, 148 genes were selected, for 5 of them the expression overlapped with cisplatin sensitivity related genes. In the lists, genes involved in mediating and regulating apoptosis were abundant, such as regulators of TGF signaling, ubiquitin mediated protein degradation and members of the immediate early response protein family. Several genes which products interact with components of the cytoskeleton were also identified. Conclusion: We have used a unique strategy to screen for potential chemosensitivity markers by utilizing xenografts as training sets.

No significant financial relationships to disclose.

Antiproliferative activity and mechanism of action of fatty acid derivatives of gemcitabine in leukemia and solid tumor cell lines and in human xenografts

Gemcitabine is a deoxycytidine analog, which can be inactivated by deamination catalyzed by deoxycytidine deaminase (dCDA). Altered transport over the cell membrane is a mechanism of resistance to gemcitabine. To facilitate accumulation, the fatty acid derivative CP-4125 was synthesized. Since, the fatty acid is acylated at the site of action of dCDA, a decreased deamination was expected. CP-4125 was equally active as gemcitabine in a panel of rodent and human cell lines and in human melanoma xenografts bearing mice. In contrast to gemcitabine, CP-4125 was not deaminated but inhibited deamination of deoxycytidine and gemcitabine. Pools of the active triphosphate of gemcitabine increased for over 20 hr after CP-4125 exposure, while these pools decreased directly after removal of gemcitabine.

IN CONCLUSION

CP-4125 is an interesting new gemcitabine derivative.

Efficient expansion and gene transduction of mouse neural stem/progenitor cells on recombinant fibronectin

Neural stem/progenitor cells (NSCs) are commonly grown as floating neurospheres in medium containing basic fibroblast growth factor and epidermal growth factor. Under these conditions, about 1% of the cells retain multipotentiality. We developed a protocol based on culture of NSCs in adherence on recombinant fibronectin (rFN) to transduce up to 90% NSCs at a multiplicity of infection of 2 with no need for viral concentration or production of serum-free retroviral supernatants. NSCs grew faster on rFN than as neurospheres on tissue culture plastic and did not lose their stem cell nature or multipotentiality. Furthermore, retroviral-mediated transgene expression was sustained with time in culture and upon differentiation into neurons and astrocytes. These experimental conditions may be utilized to study the function of various genes in NSCs, and to manipulate NSCs for gene and cell therapy of several neurological diseases.

Modulation of glioma cell invasion and motility by adenoviral gene transfer of PAI-1

A number of studies have emphasized the role of PAI-1 as an important regulator of tumor cell invasion and metastasis. The hallmark of primary tumors of the central nervous system and glioblastomas in particular is the diffuse invasion into the normal brain tissue. Since PAI-1 is expressed in such tumors, we studied the effect of adenoviral-mediated transfer of the PAI-1 gene in regulating the in vitro invasiveness of D54Mg glioma cells into Matrigel, and into fetal rat brain aggregates. Treatment of D54Mg cells with 50 MOI (multiplicity of infection) of the replication defective vector AdCMVPAI-1 increased PAI-1 expression 23-fold compared to control vectors, and the invasion through Matrigel was reduced by 67%. The motility of the cells was reduced by 58% compared to controls (indicating that inhibition of motility was the principal effect of PAI-1 in these cells). The ability of D54Mg tumor spheroids to invade fetal rat brain aggregates was not reduced by the PAI-1 gene transfer. The results show that overexpression of PAI-1 can inhibit glioma cell motility and invasion through extracellular matrix (ECM) components, like laminin and collagen, but does not inhibit tumor cell invasion in a three-dimensional invasion assay, simulating normal brain tissue having a different ECM and interstitial composition. The different results obtained in the two invasion assays reflect the complex biological effects of the uPA/PAI-1 system, and questions a simplistic view of PAI- I as an inhibitor of brain tumor invasion.

Retroviral transfer of MRP1 and gamma-glutamyl cysteine synthetase modulates cell sensitivity to L-buthionine-S,R-sulphoximine (BSO): new rationale for the use of BSO in cancer therapy

MRP1 (multidrug resistance protein 1) co-exports glutathione (GSH) and drug(s) and exports GSH, glucuronide, and sulphate-conjugated drugs. Human Fly-eco fibrosarcoma cells producing the MRP1-expressing retrovirus SF91MRP (Fly-eco MRP1), as well as 3T3 cells transduced with SF91MRP (3T3/MRP1), presented a decrease in intracellular GSH levels, as measured by two different methods. The enhanced export of GSH caused by the overexpression of MRP1 was partially counterbalanced by an increased rate of GSH synthesis. Fly-eco MRP1 and 3T3/MRP1 were hypersensitive to the GSH-depleting and cytotoxic activities of L-buthionine-S,R-sulphoximine (BSO), compared with their parental counterparts. In addition, the potentiation by BSO of the cytotoxic activity of chlorambucil and doxorubicin in Fly-eco MRP1 cells was greater than in parental Fly-eco cells. Although the turnover time of GSH, i.e. the theoretical time in which the entire GSH pool is resynthesised, was approximately 50% faster in Fly-eco MRP1 cells than in parental cells, this was not sufficient to fully restore the intracellular GSH level. In addition, mrp1 (-/-) mice were resistant to the GSH-depleting activity of intraperitoneally (i.p.) injected BSO, compared with mrp1 (+/+) mice. Co-transfer of the cDNAs for MRP1 and the heavy subunit of gamma-glutamyl cysteine synthetase (GCS) resulted in increased intracellular GSH levels and in high-level resistance to the GSH-depleting and cytotoxic activities of BSO. These data, and in particular the elevated single-agent cytotoxicity of BSO, provide a new rationale for the use of BSO in the treatment of MRP1-overexpressing tumours.

Expression of ring finger-deleted TRAF2 sensitizes metastatic melanoma cells to apoptosis via up-regulation of p38, TNFalpha and suppression of NF-kappaB activities

Mechanisms underlying radiation and chemotherapy resistance, the hallmark of human melanoma, are not well understood. Here we demonstrate that expression levels of signal adaptor protein TRAF2 coincide with melanoma resistance to UV-irradiation. Altered TRAF2 signaling by a form of TRAF2, which lacks the ring finger domain (TRAF2DeltaN), increases activities of p38 MAPK, ATF2, and the level of TNFalpha expression. Forced expression of TRAF2DeltaN in HHMSX highly metastatic melanoma cells that lack Fas expression and thus utilize the TNFalpha-TNFR1 as the major apoptotic pathway sensitized cells to UV-induced apoptosis. An over twofold increase in degree of apoptosis was observed in TRAF2DeltaN expressing cells that were treated with actinomycin D, anisomycin or with the radiomimetic drug neocarzinostatin. Sensitization by TRAF2DeltaN is selective since it was not observed in response to either Taxol or cis-platinum treatment. TRAF2DeltaN effects are primarily mediated via p38 since inhibition of p38 reduces, whereas activation of p38 promotes the level of UV-induced apoptosis. Conversely, activation of IKK attenuates the sensitization of melanoma by TRAF2DeltaN, indicating that p38-mediated suppression of NF-kappaB activity is among TRAF2DeltaN effects. Our finding identifies p38, TNFalpha and NF-kappaB among key players that efficiently sensitizes melanoma cells to UV-, ribotoxic (anisomycin) and radiomimetic chemicals-induced programmed cell death in response to aberrant TRAF2 signaling.

Structure-activity studies of novobiocin analogs as modulators of the cytotoxicity of etoposide (VP-16)

We have previously reported that the antibiotic novobiocin enhanced the toxicity of the anticancer agent etoposide (VP-16) to several drug-sensitive and -resistant tumor cell lines. The increase in VP-16 cytotoxicity produced by novobiocin was not due to the combined effects of these agents on topoisomerase II, but to inhibition by novobiocin of VP-16 efflux, which in turn led to increased accumulation of VP-16 and increased formation of potentially lethal VP-16-stabilized topoisomerase II-DNA covalent complexes. We have now identified novobiocin analogs that are essentially equivalent to novobiocin as inhibitors of the activity of topoisomerase II, but that are more potent than novobiocin (a) as modulators of the cytotoxicity of VP-16 to WEHI-3B leukemia and A549 lung carcinoma cells and (b) in increasing VP-16 accumulation in these cell lines. Thus, removal of the sugar moiety of novobiocin to form novobiocic acid enhanced the potency of the antibiotic as a modulator of VP-16, whereas the substituted coumarin ring alone (U-7587) was devoid of VP-16 modulatory activity. Modifications of the side chain of novobiocin significantly influenced modulatory activity, with cyclonovobiocic acid, which was formed from novobiocic acid by acid-catalyzed cycloaddition, being the most active in enhancing the cytotoxicity of VP-16. The increased potency of novobiocic acid and cyclonovobiocic acid as modulators of VP-16 activity was achieved with no change from novobiocin in the capacity of these analogs to inhibit the catalytic activity of mammalian topoisomerase II, indicating a change in the specificity of these analogs.

Optimization of hammerhead ribozymes for the cleavage of S100A4 (CAPL) mRNA

Previously, suppression of the S100A4 mRNA by an endogenously expressed ribozyme in osteosarcoma cells was shown to inhibit their metastasis in rats. As a prelude to performing similar studies with exogenous, synthetic ribozymes, we compared a series of hammerhead ribozymes targeted against different sites in the mRNA. The ribozymes differed only in the 7-base flanking sequences complementary to the substrate and were protected against nucleases by chemical modification. Cleavage efficiency varied widely and was not obviously related to the predicted secondary structure of the target RNA. The most active ribozyme of the series was chosen for further optimization. Lengthening its flanking sequences was counterproductive and reduced cleavage even when using excess ribozyme. Using excess substrate (multiple-turnover kinetics), cleavage was fastest with the (6+8) ribozyme having 6 nucleotides (nt) in stem III and 8 nt in stem I. Although these stems strongly influence ribozyme performance, their optimization is still empirical. Faster cleavage was obtained by adding facilitator oligonucleotides to ribozymes with shorter stems of (6+6) and (5+5) nt. Stimulation was particularly strong in the case of the (5+5) ribozyme, which was poorly active by itself. The enhancement caused by different facilitator oligonucleotides paralleled their expected ability to hybridize to RNA as a function of length and chemical modification.

Immunobead-based detection and characterization of circulating tumor cells in melanoma patients

The presence of circulating tumor cells in bone marrow and peripheral blood of cancer patients may reflect the aggressiveness of the disease. This also applies to cancers that rarely give rise to overt bone marrow metastases. The clinical validity of micrometastasis detection for staging and prognostication depends on the sensitivity and reliability of the detection method. In malignant melanoma, most studies have used reverse transcriptase polymerase chain reaction (RT-PCR) techniques, commonly with tyrosinase mRNA as the target molecule. Unfortunately, highly inconsistent results have been reported, raising doubts about this approach. In a study of 81 melanoma patients with metastatic disease, we used an immunobead rosetting method in which live melanoma cells are selected and identified by binding of paramagnetic beads coated with the 9.2.27 antibody against the high molecular weight melanoma-associated antigen. In bone marrow samples obtained from 60 patients, 14 (23.3%) were positive, compared to only two of 81 in blood. A highly significant correlation (p = 0.0001, log rank test) was found between micrometastasis positivity and overall survival from time of removal of the primary tumor. Moreover, in regression analysis it was found that the presence of micrometastatic cells was an independent and the most important indicator of poor prognosis, with a relative risk of 5.38. The immunomagnetic method is simple, rapid, and highly sensitive and will be used in further prospective clinical studies.

Rapid enrichment and detection of melanoma cells from peripheral blood mononuclear cells by a new assay combining immunomagnetic cell sorting and immunocytochemical staining

Commonly used methods for detection of melanoma cells in blood, including RT-PCR and immunocytochemistry, display only a limited sensitivity and specificity. Reliable detection of less than one melanoma cell per ml of blood is hardly possible using these methods. To obtain greater sensitivity so that a single melanoma cell in up to 25 ml of blood can be detected (5 x 10(7) peripheral blood mononuclear cells, or PBMC), we developed a new assay for combined enrichment and immunocytochemical detection of disseminated melanoma cells from PBMC of patients with malignant melanomas. Melanoma cells are directly magnetically labeled using colloidal superparamagnetic microparticles approximately 60 nm in diameter conjugated to the anti-melanoma monoclonal antibody 9.2.27, with no reactivity to normal cells in blood. Magnetically labeled melanoma cells are enriched from PBMC by magnetic cell separation and detected by a new approach for immunocytochemical staining with monoclonal mouse anti-melanoma antibodies (anti-MelanA and HMB-45). The efficiency of this assay was demonstrated in a model system in which 5-500 tumor cells from the melanoma cell line SK-MEL-28 were seeded into PBMC samples from healthy donors containing 5 x 10(7) leukocytes. Mean recovery of the seeded tumor cells was 47.4 +/- 13.99% (n = 15). Applying the assay to 20-50 ml blood samples of patients with stage III-IV malignant melanomas, we were able to detect melanoma cells in two of eight patients (25%).