Francis G. Gabriel

Cancer cell adaptation to chemotherapy.

BackgroundTumor resistance to chemotherapy may be present at the beginning of treatment, develop during treatment, or become apparent on re-treatment of the patient. The mechanisms involved are usually inferred from experiments with cell lines, as studies in tumor-derived cells are difficult. Studies of human tumors show that cells adapt to chemotherapy, but it has been largely assumed that clonal selection leads to the resistance of recurrent tumors.MethodsCells derived from 47 tumors of breast, ovarian, esophageal, and colorectal origin and 16 paired esophageal biopsies were exposed to anticancer agents (cisplatin; 5-fluorouracil; epirubicin; doxorubicin; paclitaxel; irinotecan and topotecan) in short-term cell culture (6 days). Real-time quantitative PCR was used to measure up- or down-regulation of 16 different resistance/target genes, and when tissue was available, immunohistochemistry was used to assess the protein levels.ResultsIn 8/16 paired esophageal biopsies, there was an increase in the expression of multi-drug resistance gene 1 (MDR1) following epirubicin + cisplatin + 5-fluorouracil (ECF) chemotherapy and this was accompanied by increased expression of the MDR-1 encoded protein, P-gp. Following exposure to doxorubicin in vitro, 13/14 breast carcinomas and 9/12 ovarian carcinomas showed >2-fold down-regulation of topoisomerase IIα (TOPOIIα). Exposure to topotecan in vitro, resulted in >4-fold down-regulation of TOPOIIα in 6/7 colorectal tumors and 8/10 ovarian tumors.ConclusionThis study suggests that up-regulation of resistance genes or down-regulation in target genes may occur rapidly in human solid tumors, within days of the start of treatment, and that similar changes are present in pre- and post-chemotherapy biopsy material. The molecular processes used by each tumor appear to be linked to the drug used, but there is also heterogeneity between individual tumors, even those with the same histological type, in the pattern and magnitude of response to the same drugs. Adaptation to chemotherapy may explain why prediction of resistance mechanisms is difficult on the basis of tumor type alone or individual markers, and suggests that more complex predictive methods are required to improve the response rates to chemotherapy.

Observational and cost analysis of the implementation of breast cancer sentinel node intraoperative molecular diagnosis

Background Accurate intraoperative sentinel lymph node (SLN) assessment enables axillary clearance to be completed immediately in node-positive breast cancer patients. This article reports a study of the introduction of intraoperative molecular SLN analysis in routine clinical practice in the Portsmouth Breast Care Centre. Design There was prospective analysis of 254 consecutive patients who underwent SLN biopsy in a single centre. Nodes were sectioned at 2 mm intervals and alternate slices were analysed using a CE-marked assay for mammaglobin (MG) and cytokeratin 19 (CK19). Remaining slices of node were sent for histological analysis, which included CK19 immunohistochemistry. While the assay was being carried out, the surgeon performed the breast tumour resection. The cost per patient was estimated retrospectively and the cost effects on the hospital and primary care trust for a typical service were also estimated. Results A total of 491 SLNs from 254 patients were evaluated. The intraoperative assay showed positivity of SLNs for metastatic cells in 78 patients. There was 100% detection of macrometastases within sentinel nodes analysed by GeneSearch. Overall concordance between histological status, including micrometastases and GeneSearch analysis, was 95% (sensitivity 96%, specificity 95%). The cost per procedure was increased for wide local excision with SLN biopsy and intraoperative assessment compared with other models, but fewer procedures were carried out. Conclusion Intraoperative assessment of SLNs in breast cancer using a molecular assay is a safe, acceptable and accurate technique that allows a reduction in the frequency of delayed axillary clearance surgery. Take-up of this method may be hampered by perverse incentives operating within healthcare funding.

The molecular basis of the chemosensitivity of metastatic cutaneous melanoma to chemotherapy

Background Chemotherapy benefits relatively few patients with cutaneous melanoma. The assessment of tumour chemosensitivity by the ATP-based tumour chemosensitivity assay (ATP-TCA) has shown strong correlation with outcome in cutaneous melanoma, but requires fresh tissue and dedicated laboratory facilities. Aim To examine whether the results of the ATP-TCA correlate with the expression of genes known to be involved in resistance to chemotherapy, based on the hypothesis that the molecular basis of chemosensitivity lies within known drug resistance mechanisms. Method The chemosensitivity of 47 cutaneous melanomas was assessed using the ATP-TCA and correlated with quantitative expression of 93 resistance genes measured by quantitative reverse transcriptase PCR (qRT-PCR) in a Taqman Array after extraction of total RNA from formalin-fixed paraffin-embedded tissue. Results Drugs susceptible to particular resistance mechanisms showed good correlation with genes linked to these mechanisms using signatures of up to 17 genes. Comparison of these signatures for DTIC, treosulfan and cisplatin showed several genes in common. HSP70, at least one human epidermal growth factor receptor, genes involved in apoptosis (IAP2, PTEN) and DNA repair (ERCC1, XPA, XRCC1, XRCC6) were present for these agents, as well as genes involved in the regulation of proliferation (Ki67, p21, p27). The combinations tested included genes represented in the single agent signatures. Conclusions These data suggest that melanoma chemosensitivity is influenced by known resistance mechanisms, including susceptibility to apoptosis. Use of a candidate gene approach may increase understanding of the mechanisms underlying chemosensitivity to drugs active against melanoma and provide signatures with predictive value.

Screening Autoantibody Profiles in Systemic Rheumatic Disease with a Diagnostic Protein Microarray That Uses a Filtration-Assisted Nanodot Array Luminometric Immunoassay (NALIA)

BACKGROUND We developed a cost-efficient modular system for multiplex analysis of the multiple autoantibodies that characterize systemic rheumatoid diseases. METHODS The nanodot array luminometric immunoassay (NALIA) system consists of conventional 96-well membrane-bottomed plates in which antigens or antibodies are adsorbed onto the underside of the membrane. Current arrays use a 5 x 5 format (25 dots/well), which allows 10 analytes to be measured in duplicate: double-stranded DNA (dsDNA), centromere protein B (CENP-B), PCNA, Sm, Sm ribonucleoprotein (Sm-RNP), U1-snRNP, Scl70, SSA/Ro, SSB/La, Jo-1, and controls. The test fluid, control sera, and subsequent reagents are drawn through the membrane. The captured analytes are quantified by monitoring chemiluminescence with a charge-coupled device (CCD) and analyzed with commercial array software. RESULTS The assay can detect <20 x 10(3) IU/L of anti-dsDNA. The interwell CV was 10%-14%. There was an 83% concordance (kappa = 0.56) between the NALIA results obtained for anti-dsDNA assayed by beta-testing in a routine immunology diagnostic laboratory and the results obtained with a conventional ELISA reagent set. The concordance values for Ro, La, Sm, and RNP were 98% (kappa, 0.92), 93% (kappa, 0.41), 97% (kappa, 0.62), and 97% (kappa, 0.73), respectively. CONCLUSION The NALIA approach promises to provide a highly economical platform for a wide range of applications that require assays of multiple analytes. The degree of concordance of our results with a conventional reagent set was no less than that occurring between different commercial products. A sample of serum from a finger stick provides a volume sufficient to perform the array assay.

The biology of micrometastases from uveal melanoma

Background The aim of this study was to investigate the possible causes of tumour latency in uveal melanoma primarily through the analysis of micrometastases in tissue obtained from donors postmortem. Various explanations have been proposed but there is no clear answer from animal studies and few human data. The main hypotheses may be divided into several areas—immunological control of metastatic cells, lack of angiogenesis within micrometastases and reduced cell turnover. Methods 196 patients were recruited to the study between 2003 and 2007. Patients were invited to take part and their relatives agreed to postmortem examination of their liver and lungs in the event of their death, including tissue sampling to assess the presence of micrometastases and their biology. Metastatic cells were detected by immunohistochemistry using a pan-melanoma antibody reagent, and by quantitative reverse transcriptase (qRT)–PCR for three melanoma-associated genes (tyrosinase Melan-A, and gp100) and a housekeeping gene (HMBS/PBGD) in samples stored in RNAlater or as formalin-fixed paraffin-embedded tissue. Results 22 deaths were investigated at autopsy as part of the study. Sixteen patients died with large deposits of metastatic melanoma, while six patients died of other causes. In addition, a liver resection for hepatic adenoma provided further tissue from a case without clinical evidence of metastasis. Metastatic melanoma cells were identified by immunohistochemistry of the liver samples in one case and by qRT–PCR in two further cases without macrometastases. There was no evidence of multicellular micrometastases sufficiently large to require angiogenesis and no associated inflammation was observed. Conclusion The most likely explanation for latency in this setting is the inability of uveal melanoma cells in metastatic sites to grow.

Activation of tonsil dendritic cells with immuno-adjuvants

BackgroundDendritic cells (DC) play the key role in directing antigen-specific immune responses and manipulating their function may be a useful tool for immunotherapy. The balance between immune stimulation and tolerance is particularly important at mucosal interfaces, where discrimination between dangerous pathogens and innocuous antigens takes place. In humans, although much is known about the responses of monocyte derived DC, relatively little is known about effect of immuno-stimulatory adjuvants on DC found in tonsil.ResultsTo examine this, tonsil DC were isolated and cultured with potent DC activators; IFNγ, anti-CD40 antibody, LPS and Poly I:C either singly or in combination. To measure maturation and activation, DC were examined for changes in the expression of HLA-DR, HLA- class I, CD83, CD40, CD80 and CD86 and the release of IL12p70.The DC isolated from tonsil were a mixed population containing both myeloid and plasmacytoid DC, but all showed similar responses. Tonsil DC released IL12p70 upon stimulation with IFNγ , anti-CD40 antibody, and LPS, but unlike monocyte-derived DC, they did not increase the expression of cell surface activation molecules above those induced by culture alone. Poly I:C, a potent stimulator of laboratory generated DC inhibited the activation of tonsil DC by other adjuvants.ConclusionAs the response of this mixed population of DC does not mirror that of DC generated in vitro, this may have implications for other tissue residing DC and might be an important consideration for immunotherapy.

Rapid up-regulation of cyclooxygenase-2 by 5-fluorouracil in human solid tumors.

Inhibition of cyclooxygenase (COX)-2 has been associated with reduced growth of malignant cells. Current therapy of gastrointestinal carcinomas involves the use of 5-fluorouracil (5-FU)-based chemotherapy and we have therefore studied the effect of this agent on the expression of COX-2. COX-2 expression was measured by quantitative RT-PCR in biopsies from a series of 14 esophageal carcinomas, six of which had paired samples taken before and after chemotherapy, and in tumor-derived cells exposed to 5-FU in vitro from a series of 44 tumors, including breast, ovarian, esophageal and colonic carcinomas. COX-2 expression was increased by exposure to 5-FU or 5-FU combination chemotherapy in all the tumor types studied, whether measured in biopsies taken before and after 5-FU-based chemotherapy (4-fold increase, p<0.015) or in primary cells exposed to drugs in vitro (24-fold increase, p<0.001). A modest increase of COX-2 mRNA was also seen after in vitro treatment of cells with cisplatin. In contrast, doxorubicin and paclitaxel caused no up-regulation in vitro, while irinotecan caused inhibition of COX-2 (2.7-fold decrease, p<0.01). These data provide a molecular rationale for clinical trials of combination chemotherapy with COX-2 inhibitors.

Measuring Gene Expression from Cell Cultures by Quantitative Reverse-Transcriptase Polymerase Chain Reaction

Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) offers a robust method for the measurement of RNA levels for any gene within cells harvested at any point before or during cell culture. The key elements of RNA extraction followed by a two-step qRT-PCR method (reverse transcription and PCR) are described, followed by a brief section on analysis of the results. There are a number of excellent kits available commercially for much of this work, but it is essential to ensure that the quality and quantity of cDNA produced is adequate for the standard PCR or array to be used.