Guidelines for the use of cell lines in biomedical research

Cell-line misidentification and contamination with microorganisms, such as mycoplasma, together with instability, both genetic and phenotypic, are among the problems that continue to affect cell culture. Many of these problems are avoidable with the necessary foresight, and these Guidelines have been prepared to provide those new to the field and others engaged in teaching and instruction with the information necessary to increase their awareness of the problems and to enable them to deal with them effectively. The Guidelines cover areas such as development, acquisition, authentication, cryopreservation, transfer of cell lines between laboratories, microbial contamination, characterisation, instability and misidentification. Advice is also given on complying with current legal and ethical requirements when deriving cell lines from human and animal tissues, the selection and maintenance of equipment and how to deal with problems that may arise.

Quantitative analysis of BTF3, HINT1, NDRG1 and ODC1 protein over-expression in human prostate cancer tissue

Prostate carcinoma is the most common cancer in men with few, quantifiable, biomarkers. Prostate cancer biomarker discovery has been hampered due to subjective analysis of protein expression in tissue sections. An unbiased, quantitative immunohistochemical approach provided here, for the diagnosis and stratification of prostate cancer could overcome this problem. Antibodies against four proteins BTF3, HINT1, NDRG1 and ODC1 were used in a prostate tissue array (> 500 individual tissue cores from 82 patients, 41 case pairs matched with one patient in each pair had biochemical recurrence). Protein expression, quantified in an unbiased manner using an automated analysis protocol in ImageJ software, was increased in malignant vs non-malignant prostate (by 2-2.5 fold, p<0.0001). Operating characteristics indicate sensitivity in the range of 0.68 to 0.74; combination of markers in a logistic regression model demonstrates further improvement in diagnostic power. Triple-labeled immunofluorescence (BTF3, HINT1 and NDRG1) in tissue array showed a significant (p<0.02) change in co-localization coefficients for BTF3 and NDRG1 co-expression in biochemical relapse vs non-relapse cancer epithelium. BTF3, HINT1, NDRG1 and ODC1 could be developed as epithelial specific biomarkers for tissue based diagnosis and stratification of prostate cancer.

Abstract 4077: Plexin B1 trafficking in prostate cancer

Prostate cancer is a leading form of cancer in men with 324,000 cases diagnosed/year in the European Union. Plexin B1 is a cell-membrane receptor for semaphorins; its ligand is semaphorin 4D. Plexin receptors are involved in axon guidance, angiogenesis, immunity as well as cancer biology. We have identified a high frequency of somatic missense mutations in the plexin B1 gene and overexpression of the protein in prostate cancer. The mutations found in prostate cancer are functionally significant, altering signalling pathways downstream of plexinB1 and affecting cell phenotype. These results suggest that plexin B1 has an important role in prostate cancer progression. Previous studies have documented the unexpected localization of cell membrane receptors such as EGFR and ErbB2, in the nucleus and their role as transcription factors. Preliminary immunohistochemistry results in the laboratory indicated the presence of plexin B1 protein in the nucleus in tumour cells, suggesting that plexins may have a role in the nucleus. The aim of this study was to determine if plexin B1 is translocated to the nucleus in prostate cancer cells and what is the nuclear localization signal recognized for the trafficking of the protein.

The different techniques were used; Immunofluorescence was performed on cell lines with antibodies specific to the intracellular domain of plexin B1. Colocalization studies were carried out using the Volocity Software®. A cell fractionation assay was performed and cell lysates analysed by immunoblotting. A construct of the cytoplasmic domain of plexin B1 fused with GFP was generated and its subcellular localization in transfected cells analysed by confocal microscopy. The plexin B1/GFP construct is currently mutated on the putative NLS signal using site-directed mutagenesis. The subcellular localization of the plexin B1 mutants will be observed by confocal microscopy.

Immunofluorescence of prostate cancer cell lines showed the presence of the intracellular domain of plexin B1 receptor in the nucleus, suggesting a translocation of the protein to the nucleus. Plexin B1 was found to co-localize with DAPI staining. Further immunofluorescence studies showed that the presence of plexin B1 in the nucleus is dependent on semaphorin 4D binding in a time-dependent manner. The translocation occurs 15min after ligand binding and decreases after 40min of ligand binding. A cell fractionation assay followed by immunoblotting confirmed the preliminary immunofluorescence data. To assess the nuclear trafficking with a functional assay, a GFP tag was attached to the intracellular domain of plexin B1 and its translocation to the nucleus was observed in transfected cells.

In conclusion, the translocation of plexin B1 to the nucleus suggests an interesting novel role for this receptor in the nucleus. Plexin B1 could act as a transcription co-factor and may have an impact on carcinogenesis.

Citation Format: Anne Legendre, John R W Masters, Magali Williamson. Plexin B1 trafficking in prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4077. doi:10.1158/1538-7445.AM2013-4077

Recommendation of short tandem repeat profiling for authenticating human cell lines, stem cells, and tissues

Cell misidentification and cross-contamination have plagued biomedical research for as long as cells have been employed as research tools. Examples of misidentified cell lines continue to surface to this day. Efforts to eradicate the problem by raising awareness of the issue and by asking scientists voluntarily to take appropriate actions have not been successful. Unambiguous cell authentication is an essential step in the scientific process and should be an inherent consideration during peer review of papers submitted for publication or during review of grants submitted for funding. In order to facilitate proper identity testing, accurate, reliable, inexpensive, and standardized methods for authentication of cells and cell lines must be made available. To this end, an international team of scientists is, at this time, preparing a consensus standard on the authentication of human cells using short tandem repeat (STR) profiling. This standard, which will be submitted for review and approval as an American National Standard by the American National Standards Institute, will provide investigators guidance on the use of STR profiling for authenticating human cell lines. Such guidance will include methodological detail on the preparation of the DNA sample, the appropriate numbers and types of loci to be evaluated, and the interpretation and quality control of the results. Associated with the standard itself will be the establishment and maintenance of a public STR profile database under the auspices of the National Center for Biotechnology Information. The consensus standard is anticipated to be adopted by granting agencies and scientific journals as appropriate methodology for authenticating human cell lines, stem cells, and tissues.

A novel role for Wnt/Ca2+ signaling in actin cytoskeleton remodeling and cell motility in prostate cancer

Wnt signaling is a critical regulatory pathway in development and disease. Very little is known about the mechanisms of Wnt signaling in prostate cancer, a leading cause of death in men. A quantitative analysis of the expression of Wnt5A protein in human tissue arrays, containing 600 prostate tissue cores, showed >50% increase in malignant compared to benign cores (p<0.0001). In a matched pair of prostate cancer and normal cell line, expression of Wnt5A protein was also increased. Calcium waves were induced in prostate cells in response to Wnt5A with a 3 fold increase in Flou-4 intensity. The activity of Ca²⁺/calmodulin dependent protein kinase (CaMKII), a transducer of the non-canonical Wnt/Ca²⁺ signaling, increased by 8 fold in cancer cells; no change was observed in β-catenin expression, known to activate the canonical Wnt/β-catenin pathway. Mining of publicly available human prostate cancer oligoarray datasets revealed that the expression of numerous genes (e.g., CCND1, CD44) under the control of β-catenin transcription is down-regulated. Confocal and quantitative electron microscopy showed that specific inhibition of CaMKII in cancer cells causes remodeling of the actin cytoskeleton, irregular wound edges and loose intercellular architecture and a 6 and 8 fold increase in the frequency and length of filopodia, respectively. Conversely, untreated normal prostate cells showed an irregular wound edge and loose intercellular architecture; incubation of normal prostate cells with recombinant Wnt5A protein induced actin remodeling with a regular wound edge and increased wound healing capacity. Live cell imaging showed that a functional consequence of CaMKII inhibition was 80% decrease in wound healing capacity and reduced cell motility in cancer cells. We propose that non-canonical Wnt/Ca²⁺ signaling via CaMKII acts as a novel regulator of structural plasticity and cell motility in prostate cancer.

PAK4: a pluripotent kinase that regulates prostate cancer cell adhesion

Hepatocyte growth factor (HGF) is associated with tumour progression and increases the invasiveness of prostate carcinoma cells. Migration and invasion require coordinated reorganisation of the actin cytoskeleton and regulation of cell-adhesion dynamics. Rho-family GTPases orchestrate both of these cellular processes. p21-activated kinase 4 (PAK4), a specific effector of the Rho GTPase Cdc42, is activated by HGF, and we have previously shown that activated PAK4 induces a loss of both actin stress fibres and focal adhesions. We now report that DU145 human prostate cancer cells with reduced levels of PAK4 expression are unable to successfully migrate in response to HGF, have prominent actin stress fibres, and an increase in the size and number of focal adhesions. Moreover, these cells have a concomitant reduction in cell-adhesion turnover rates. We find that PAK4 is localised at focal adhesions, is immunoprecipitated with paxillin and phosphorylates paxillin on serine 272. Furthermore, we demonstrate that PAK4 can regulate RhoA activity via GEF-H1. Our results suggest that PAK4 is a pluripotent kinase that can regulate both actin cytoskeletal rearrangement and focal-adhesion dynamics.

Clinical applications of expression profiling and proteomics in prostate cancer

Expression profiling and proteomics have the potential to transform the management of prostate cancer, identifying new markers for screening, diagnosis, prognosis, monitoring and targets for therapy. Expression profiling has revealed that the majority of prostate cancers contain fusion genes resulting in the upregulation of ETS family transcription factors. New diagnostic markers to replace PSA are being actively sought using a variety of proteomic platforms. Nevertheless, no single molecular marker has yet been discovered that is any more reliable for predicting outcome than histopathological grading. In the future, small custom-built chips will be used to detect a small panel of RNA or protein markers to answer specific questions concerning patient management for each type of cancer.

Allelic imbalance and biochemical outcome after radical prostatectomy

OBJECTIVE

To compare the incidence of allelic imbalance (AI) in men with rapid disease progression with those who remained disease free after radical prostatectomy, with the aim of identifying genetic markers to predict prognosis and guide further treatment.

PATIENTS AND METHODS

Tumour and normal DNA were extracted from two matched groups of 31 men with extracapsular node-negative (pT3N0) prostate cancer who had undergone radical prostatectomy. One group comprised men who developed biochemical recurrence within 2 years of surgery and one group were prostate-specific antigen (PSA) free for at least 3 years. Men were matched for Gleason grade, preoperative PSA and pathological stage. Analysis was performed by genotyping.

RESULTS

Allelic imbalance was analysed using 30 markers, and was seen in at least one marker in 57 (92%) of the cases. Deletion at marker D10S211 (10p12.1) was significantly more common in the relapse group than the non-relapse group (35 vs 5%, P=0.03).

CONCLUSIONS

This study demonstrates significant association between AI on chromosome 10 and biochemical progression after radical prostatectomy.

Rho family GTPases are activated during HGF-stimulated prostate cancer-cell scattering

An important process in embryogenesis and cancer-cell metastasis is the conversion of epithelial cells to a migratory phenotype, a phenomenon known as epithelial-mesenchymal transition (E-MT). To achieve E-MT, cells dissociate from neighbouring cells and adopt a migratory morphology. This transition requires remodelling of their cell shape and substratum adhesions; activities that require extensive reorganisation of the actin cytoskeleton. Hepatocyte growth factor (HGF)-induced scattering of Madin Darby canine kidney (MDCK) cells is a routinely used model of E-MT, in which actin cytoskeletal rearrangement is known to be dependent on Rho family GTPases. We have developed a novel model of HGF-induced E-MT using the human prostate cancer cell line, DU145. This model overcomes the limitation of using a canine cell line and facilitates the study of E-MT in human cancer. We demonstrate for the first time the scattering response of individual DU145 cells to HGF in real time and have characterised changes in actin cytoskeletal organisation and cell adhesions as these cells respond to HGF. HGF-induced scattering of DU145 cells is dependent on the activity of Rho family GTPases, and using this model, we are able to demonstrate for the first time that endogenous Cdc42 is activated downstream of HGF. Furthermore we have also shown that the response of DU145 cells to HGF is dependent on a phosphatidylinositide 3-kinase pathway.

Tumour markers for managing men who present with metastatic prostate cancer and serum prostate-specific antigen levels of <10 ng/mL

OBJECTIVE

To define immunohistochemical features of the primary cancers that might help in the differential diagnosis and monitoring of treatment in men presenting with metastatic prostate cancer and low serum levels of prostate-specific antigen (PSA), who can be difficult to diagnose and manage.

PATIENTS AND METHODS

Paraffin blocks of prostate biopsies were obtained for 33 patients presenting with untreated metastatic prostate cancer and serum PSA levels of <10 ng/mL. Sections were immunostained for PSA, prostatic acid phosphatase (PAP), prostate-specific membrane antigen (PSMA), androgen receptor (AR), chromogranin A and CD 56.

RESULTS

The combined Gleason scores were 8-10 in 25 men (76%) and 6 or 7 in the other eight (24%). Morphologically, there were no neuroendocrine features. PSA immunostaining was equivocal in 12 (36%) cases and in a further 19 (58%) was strong but focal and could be missed on biopsy sampling. PSMA was expressed in 90% of cases, and staining was widely distributed in nine of the 12 in which PSA staining was equivocal. There was strong AR expression in 30 (91%) cases and it was present in areas where PSA was absent.

CONCLUSION

In this patient group, immunohistochemical assessments of PSMA and AR are potentially useful as diagnostic markers.

Reduced levels of XPA, ERCC1 and XPF DNA repair proteins in testis tumor cell lines

Over 80% of patients with advanced metastatic testis tumors can be cured using cisplatin-based combination chemotherapy. This is unusual as metastatic cancer in adults is usually incurable. Cell lines derived from testis tumors retain sensitivity to cisplatin in vitro. We previously investigated 2 testis tumor cell lines with a low capacity to remove cisplatin-induced DNA damage and found that they had low levels of the DNA nucleotide excision repair proteins XPA, ERCC1 and XPF. To determine whether low levels of XPA, ERCC1 and XPF proteins are characteristic of testis tumor cell lines, we investigated 35 cell lines derived from cancers to determine whether groups of cell lines from diverse tissue origins differ from one another in constitutive levels of these NER proteins. Quantitative immunoblotting was used to compare groups of cell lines representing prostate, bladder, breast, lung, cervical, ovarian and testis cancers. Only the 6 testis tumor cell lines showed significantly lower mean levels of XPA (p = 0.001), XPF (p = 0.001) and ERCC1 (p = 0.004) proteins from the other groups. Our results encourage further investigation of the possibility that low levels of these nucleotide excision repair proteins could be related to the favorable response of testis tumors to cisplatin-based chemotherapy.

Clinical features of patients who present with metastatic prostate carcinoma and serum prostate-specific antigen (PSA) levels < 10 ng/mL

BACKGROUND

Although < 1% of men present with prostate-specific antigen (PSA)-negative prostate carcinoma, in that they have serum PSA levels much lower than the tumor burden would suggest, such patients represent a management dilemma. To the authors' knowledge, little information exists in the literature regarding patterns of disease and response to treatment. The authors wished to define the clinical features of this patient group.

METHODS

The British Association of Urological Surgeons Cancer Registry 2000 and 2001 data bases were used to identify the clinical features and outcome of 33 men with metastatic prostate carcinoma who presented with serum PSA levels < 10 ng/mL. Clinical notes and histopathology were reviewed for each patient.

RESULTS

Seventeen patients (51%) presented with urinary symptoms and/or pelvic pain, 6% with cachexia and 21% with bone pain. Characteristic bone metastases were present in 81% of patients, similar to the presentation of men with high serum PSA levels. Hypercalcemia was a feature in 9% of patients. Visceral metastases were present in two patients. The median response duration to first-line hormone manipulation was 7 months. No responses were seen in 11 of 13 patients who received second-line hormones or to any third-line treatment. Three of 5 patients who received chemotherapy responded but developed recurrent disease within 8 weeks of treatment cessation. The median overall survival was 12 months.

CONCLUSIONS

The presentation of patients with treatment-naïve PSA-negative metastatic prostate carcinoma is similar to that of patients with high serum PSA levels, but their median survival and response duration to first-line hormone therapy are of much shorter duration. Second-line hormone therapy is ineffective, but early chemotherapy may be beneficial. Hypercalcemia is a particular feature in this group of patients.

Curing metastatic cancer: lessons from testicular germ-cell tumours

Most metastatic cancers are fatal. More than 80% of patients with metastatic testicular germ-cell tumours (TGCTs), however, can be cured using cisplatin-based combination chemotherapy. Why are TGCTs more sensitive to chemotherapeutics than most other tumour types? Answers to this question could lead to new treatments for metastatic cancers.

Can p53 staining be used to identify patients with aggressive superficial bladder cancer?

Approximately 10% of patients with superficial bladder cancer (pTa/pT1) recur with life-threatening muscle-invasive disease. Identification of these patients has been a major goal of bladder cancer research. In 1994, it was suggested that p53 immunostaining could identify the cancers that would progress and it was proposed that tumours that stain for p53 should be treated aggressively with radiotherapy or cystectomy. Despite the hundreds of studies published since on the relationship between p53 and progression in superficial bladder cancer, the clinical utility of p53 immunostaining has not been resolved because of limitations concerning the numbers of patients and the length of follow-up. This study set out to overcome these limitations by using tissue from a large multicentre trial that recruited 502 patients with a median follow-up of 10 years. Each of 34 patients that had progressed with >/= pT2 disease or had distant metastases or had died from bladder cancer was compared with one or two matched controls. Sections were stained with a mouse monoclonal antibody to p53, pAb1801. In agreement with many of the earlier studies, p53 immunostaining had prognostic significance. The adjusted hazard ratio for time to progression for the pAb1801-positive versus negative group was 2.5, with 95% confidence intervals of 1.05-5.98 (p = 0.039). The other major risk factor that is associated with progression of superficial bladder cancer is pT1G3 disease. Of the 42 pT1G3 cancers, 14 (33%) progressed. The proportion of cancers with p53 staining that progressed was similar to the proportion of pT1G3 cancers that progressed, but neither the sensitivity nor the specificity of association of p53 staining with progression is sufficient to recommend cystectomy in individual patients.

The comparative values of bone marrow aspirate and trephine for obtaining bone scan-targeted metastases from hormone-refractory prostate cancer

Samples of metastatic prostate cancer to bone are difficult to obtain. The aim of this study was to compare the results of bone marrow aspirate and trephine biopsy for obtaining metastatic hormone-refractory prostate cancer (HRPC) samples using previous diagnostic planar 99(m)Tc-HDP bone scans to guide the procedure. All samples taken were for the purposes of research and molecular studies on HRPC. Twenty patients with HRPC had bone marrow aspirate and trephines taken from lesions in the posterior superior iliac spine or sacro-iliac region when shown on diagnostic 99(m)Tc-HDP bone scans. Three patients also underwent plain X-ray, 18F-positron emission tomography bone scan, pelvic MRI scan and 99(m)Tc nanocolloid bone marrow scans. These images were used to assess if the extra imaging information provided, such as three-dimensional localisation of the bone metastases, was of value for target bone metastases. Cancer cells were obtained in 15/20 (75%) cases in which a trephine biopsy was attempted and 0/20 of cases in which a bone marrow aspiration was attempted. The additional information provided by the range of other imaging investigations was of little benefit in obtaining tumour samples, but did suggest why negative biopsies were obtained in some cases after targeting with planar bone scans. We recommend the use of bone marrow trephine biopsy alone, guided by previous diagnostic 99(m)Tc planar bone scan as a practical method to obtain prostate cancer cells from bone metastases.

Amplification of the androgen receptor gene in bone metastases from hormone-refractory prostate cancer

The aim of this study was to examine the prevalence of androgen receptor (AR) amplification in metastases to bone and other sites in patients with hormone-refractory prostate cancer (HRPC) and to compare these findings with those in pretreatment primary tumour samples from the same patients. Tissue from 24 patients with HRPC was available for study, together with 13 primary tumour specimens. AR gene amplification and copy number for X-chromosome were assessed by fluorescence in situ hybridization (FISH) using a SpectrumOrange-labelled probe at locus Xq11-13 for the AR gene and a SpectrumGreen-labelled alpha-satellite probe for the X-chromosome (Vysis, UK, Ltd.). A minimum of 20 nuclei were scored in each of three tumour areas by two independent observers. Samples from 18/24 patients with HRPC (12 bone marrow biopsies, three local tumour recurrences, and three lymph nodes) and nine primary tumour specimens were adequate for FISH analysis. Results were expressed as a mean ratio of AR gene copy number : mean X-chromosome number, with a ratio of greater than 1.5 defined as amplification. AR gene amplification was seen in 9/18 (50%) cases of HRPC and in none of the primary (untreated) tumour specimens (p = 0.0048, Fisher's exact test). For the 12 bone marrow samples, AR gene amplification occurred in 5/12 (38%) cases. Elevated copy number for chromosome X occurred in 3/18 (17%) HRPC and 4/9 (44%) matched primary tumours. This study shows for the first time that AR gene amplification can be demonstrated by FISH in bone metastases from HRPC patients. Because bone marrow biopsies can be obtained from most patients with HRPC, the findings provide a rational basis for the routine selection of patients who may respond more favourably to second-line anti-androgen therapy.