Prognosis for fludarabine therapy of chronic lymphocytic leukaemia based on ex vivo drug response by DiSC assay

The rate of in vitro fludarabine-induced peripheral blood and bone marrow cell apoptosis may predict the chemotherapy outcome in patients with chronic lymphocytic leukemia

Purpose

The problem of drug sensitivity and predicting the outcome of chemotherapy seems to be of great importance in hemato-oncological disorders. There are some factors that can help to predict effects of chemotherapy in chronic lymphocytic leukemia (CLL), such as presence of del17p, del11q, or TP53 gene mutations, which result in resistance to purine analogues and alkylating drugs. Despite the new therapeutic options introduced recently, purine analogues in combination with cyclophosphamide and the monoclonal antibody rituximab is still the gold standard for the first-line treatment of fit patients with CLL. The aim of this study was to assess whether the rate of apoptosis caused by one of purine analogues—fludarabine in cell cultures differs between patients who clinically respond to fludarabine-based chemotherapy and those who do not respond.

Methods

CLL leukemic cells, obtained from peripheral blood and bone marrow of 23 patients, were cultured in the presence of fludarabine. After 24 h of incubation, the rate of apoptosis, indicated by the expression of active caspase-3, was assessed with flow cytometry and then analyzed regarding clinical response to fludarabine-based regimens.

Results

The percentage of apoptotic cells induced by fludarabine was significantly higher in the group of patients who achieved remission in comparison to the group with no response to purine analogues therapy. Interestingly, we observed that among the patients who did not respond to chemotherapy, the presence of del17p and del11q was detected only once. Other non-responders had no detectable genetic abnormalities.

Conclusions

Based on these results, it can be presumed that in vitro drug sensitivity test, which is easy to perform, may predict the outcome of fludarabine-based chemotherapy in CLL patients.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-015-1893-0) contains supplementary material, which is available to authorized users.

Differential Staining Cytotoxicity assay: a review

Differential Staining Cytotoxicity (DiSC) assay is the prototype for a closely related family of assays based on the concept of total cell kill, or, in other words, cell death occurring in the entire population of tumor cells. It is probably the most versatile of the cell-death end points, in that it (1) can be applied to both solid and hematologic neoplasms, (2) can be applied to specimens in which it is not possible to obtain a pure population of highly enriched tumor cells, and (3) can be applied to a wide variety of drugs, ranging from traditional cytotoxic agents to biological response modifiers with activity mediated through tumor-infiltrating effector cells, to "targeted" kinase inhibitors, and to antivascular agents, such as bevacizumab and pazopanib. The basic principles of the assay are to culture three-dimensional fresh tumor cell clusters in anchorage-independent conditions. At the conclusion of the culture period, Fast Green dye is added to the microwells, the contents of which are then sedimented onto permanent Cytospin centrifuge slides and then counterstained with hematoxylin-eosin or Wright-Giemsa. "Living" cells stain with the cytologic stain in question and can be identified as either normal or neoplastic, based on standard morphologic criteria. "Dead" cells stain blue-green. Nonviable endothelial cells appear as strikingly hyperchromatic, blue-black, and often refractile objects, which may be readily distinguished from other types of dead cells. This assay has been biologically and clinically validated in a number of ways, as described in this chapter.

CD154 expression triggered by purine analogues in vitro: Correlation with treatment response and autoimmune events in chronic lymphocytic leukemia

OBJECTIVE

Despite a fludarabine-based treatment is the first choice of therapy in chronic lymphocytic leukemia (CLL), not all patients achieve a partial or complete response and some of them develop autoimmune manifestations. The aim of this study was to evaluate the influence of CD154 on these adverse effects because CD154 is involved in both B-cell survival and autoimmunity.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) from 36 patients with CLL were cultured in vitro with fludarabine or 2-chlorodeoxyadenosine for 24, 48, and 72 hours.

RESULTS

Seven patients (19.4%) presented CD154 expression in PBMC cultured with purine analogues in vitro for 24 and/or 48 hours, while no expression was found when cultured in media alone. These seven patients showed a decreased apoptotic rate in vitro after purine analogues compared with those patients who did not express CD154 (p = 0.01 for fludarabine; p < 0.001 for 2-chlorodeoxyadenosine). CD154 expression was found to have prognostic value for response to fludarabine in vivo and was associated with the development of autoimmune manifestations (odds ratio = 25; 95% confidence interval = 3.5-166.7; p < 0.001).

CONCLUSION

Our preliminary results suggest that CD154 expression in CLL patients, which may be induced by purine analogues, is associated with resistance to fludarabine and with development of autoimmune manifestations.

Expression of multidrug resistance-associated ABC transporters in B-CLL is independent of ZAP70 status

PURPOSE

To assess whether the poor prognosis of ZAP70-positive B-cell chronic lymphocytic leukemia (CLL) is associated with the overexpression of ABC transporter genes that are responsible for pleiotropic drug resistance.

MATERIALS AND METHODS

The transcript level of ten drug transporters was analyzed using semiquantitative and quantitative RT-PCR in control hematopoietic cells, in 41 CLL patient samples and in 5 lymphoma cell lines. ZAP70 status was determined by immunoblotting.

RESULTS

Of all analyzed transporters, MDR1, MDR2, MRP1, MRP4, MRP5, and MRP7 were expressed at a significantly higher level in B lymphocytes when compared with other hematopoietic cells in peripheral blood. A subgroup of 41 CLL patient samples showed similar or higher expression of these genes than control B cells, and CLL cells exhibited high expression when compared with multiple lymphoma cell lines. No significant correlation between ZAP70 expression and ABC transporter expression was observed.

CONCLUSION

The ZAP70 status is independent of the multidrug resistance phenotype in CLL.

Drug induction apoptosis assay as predictive value of chemotherapy response in patients with B-cell chronic lymphocytic leukemia

A large number of prognostic factors are available to help predict the course of the disease for patients with B-cell chronic lymphocytic leukemia (B-CLL). However, it is not clear the involvement of these well established prognostic factors in the clinical response of the patients with B-CLL to the chemotherapy. The possible association of the patient clinical-biological characteristics and the in vitro response to chemotherapic agents may serve to provide powerful predictive information to identify optimum treatment for patients. An apoptosis induction assay displays the patient in vitro responses to chemotherapy and the possible association with their clinical-biological characteristics. In this study, patients showed a significant better in vitro response to drugs when they were in the initial stages of the disease or with low beta(2) microglobulin serum level. Response to purine analogues was significantly higher in patients with long lymphocyte doubling time (LDT), few cells expressing CD38, normal karyotype or no p53 deletion, whereas there was no correspondence with ZAP-70 expression. Furthermore, a good correlation was shown between in vitro apoptosis induction assay and the patient clinical response to purine analogues. In conclusion, association between in vitro drug sensitivity and some of the markers considered as prognostic factors could help to develop personalised therapeutic regimens for patients with B-CLL.

Immunohistochemistry for human concentrative nucleoside transporter 3 protein predicts fludarabine sensitivity in chronic lymphocytic leukemia

Fludarabine (F-ara-A) is widely used as palliative treatment in chronic lymphocytic leukemia (CLL). Clinical resistance is frequently observed, and adverse effects are common. To date, no practical assay exists to identify patients likely to derive benefit from F-ara-A. We previously reported that high mRNA levels encoding human concentrative nucleoside transporter 3 (hCNT3) protein in CLL correlated with clinical resistance to F-ara-A. This study explores the value of immunohistochemistry (IHC) for hCNT3 as a marker of F-ara-A resistance in CLL. We studied 36 CLL patients who received F-ara-A monotherapy and had suitable pre-F-ara-A tissue available. IHC was performed with validated hCNT3-specific monoclonal antibodies and quantitatively scored by a hematopathologist blinded to clinical outcomes. Relationships between hCNT3 staining in CLL cells and time to progression (TTP), overall response (OR), and overall survival (OS) were assessed. Dichotomization of quantitative hCNT3 staining showed that subjects with high hCNT3 IHC scores had a significantly shorter TTP with F-ara-A treatment compared to those with a low score (hazard ratio, HR, 3.16; P=0.006). Median TTP was 4.7 vs 11.2 months, respectively. On multivariate analysis, hCNT3 score was the only clinical parameter independently associated with TTP (HR, 3.12; P=0.01). OR and OS did not differ significantly between the dichotomized groups. We found a strong relationship between IHC staining of hCNT3 and clinical resistance to F-ara-A therapy in CLL. If confirmed, IHC for hCNT3 may be routinely used to predict those patients unlikely to benefit from F-ara-A, thereby avoiding F-ara-A-related toxicities.

A fluorescence microplate cytotoxicity assay with a 4-log dynamic range that identifies synergistic drug combinations

PURPOSE

Cytotoxicity assays in 96-well tissue culture plates allow rapid sample handling for multicondition experiments but have a limited dynamic range. Using DIMSCAN, a fluorescence digital image system for quantifying relative cell numbers in tissue culture plates, we have developed a 96-well cytotoxicity assay with a >4-log dynamic range.

METHODS

To overcome background fluorescence that limits detection of viable cells with fluorescein diacetate, we used 2'4'5'6'-tetrabromofluorescein (eosin Y) to quench background fluorescence in the medium and in nonviable cells to enhance the reduction of background fluorescence achieved with digital image thresholding. The sensitivity and linearity of the new assay were tested with serial dilutions of neuroblastoma and leukemia cell lines. DIMSCAN was compared with other in vitro cytotoxicity assays: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation, and trypan blue dye exclusion.

RESULTS

Without background fluorescence reduction, scans produced a nearly flat curve across various cell concentrations from 100 to 10(6) cells per well. Either digital image thresholding or eosin Y dramatically reduced background fluorescence, and combining them achieved a linear correlation (r > 0.9) of relative fluorescence to viable cell number over >4 logs of dynamic range, even in the presence of 4 x 10(4) nonviable cells per well. Cytotoxicity of deferoxamine for neuroblastoma cell lines measured by the DIMSCAN assay achieved dose-response curves similar to data obtained by manual trypan blue counts or colony formation in soft agar but with a wider dynamic range. Long-term cultures documented the clonogenic ability of viable cells detected by DIMSCAN over the entire dynamic range. The cytotoxicity of two drug combinations (buthionine sulfoximine + melphalan or fenretinide + safingol) was tested using both DIMSCAN and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, and the wider dynamic range of DIMSCAN facilitated detection of synergistic interactions.

CONCLUSION

DIMSCAN offers the ability to rapidly and efficiently conduct cytotoxicity assays in 96-well plates with a dynamic range of >4 logs. This assay enables rapid testing of anticancer drug combinations in microplates.

Use of optophoresis as an in vitro predictor of cell response to chemotherapy for chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia [CLL] is characterized by active accumulation of clonal CD5+/CD19+/CD23+ B cells. Individualized characterization of patient cell resistance/sensitivity to specific agents can provide important information to guide therapy selection. We have utilized optophoresis, which is a technique for the analysis of the motion of cells within a moving optical gradient field. It detects the broad cellular changes associated with apoptosis based on physical characteristics of the cell, such as morphology, size, refractive index, density, and surface properties. We analyzed peripheral blood samples from 62 CLL patients in the presence of varying concentrations of chemotherapeutic agents. Optophoresis and a more conventional measurement of cell death were utilized. The outcome of ex vivo drug resistance using optophoresis was compared to clinical response in 30 patients for which there was clinical outcome data available. The overall accuracy of optophoresis in reflecting clinical response was 80%. It has advantages over alternative methods of determining chemoresistance including the ability to evaluate very small sample sizes and ability to work in mixed-cell populations. Changes in cell physical characteristics in response to chemotherapy, as measured by optophoresis is an accurate method for predicting chemosensitivity ex vivo in CLL.

Drug resistance in B-cell chronic lymphocytic leukemia: Predictable by in vitro evaluation with a multiparameter flow cytometric cytotoxicity assay

BACKGROUND

Patients with B-cell chronic lymphocytic leukemia (B-CLL) often demonstrate variable responses to similar treatments. It would be highly desirable to develop a personalized therapeutic strategy for selection of appropriate drugs or regimens based on the drug sensitivity profiles of leukemic cells from individuals.

METHODS

We applied a multiparameter flow cytometric drug cytotoxicity assay to evaluate drug effects specifically on B-CLL cells from 43 individuals after leukemic cells were incubated in vitro with fludarabine, chlorambucil, cladribine, or prednisolone.

RESULTS

We demonstrated that different B-CLL cell populations from 43 individuals showed a marked variability in drug sensitivity. In vitro resistance to fludarabine was greatest in B-CLL cells with deletions of p53, a cytogenetic abnormality that is almost invariably associated with a poor therapeutic response clinically.

CONCLUSIONS

In vitro drug sensitivity profiles analyzed by a multiparameter flow cytometric cytotoxicity assay may serve as a tool to facilitate individualized selection of appropriate drugs for treatment in B-CLL. Prospective trials will be needed to validate the clinical utility of this flow cytometric cytotoxicity assay.

Apoptotic effect of fludarabine is independent of expression of IAPs in B-cell chronic lymphocytic leukemia

Despite the efficiency of fludarabine in the induction of clinical responses in B-cell chronic lymphocytic leukemia (B-CLL) patients, resistance to this drug has been documented. The present study tested whether resistance to fludarabine is related to the expression of inhibitor of apoptosis proteins (IAPs) family members. We analyzed the expression of c-IAP1, c-IAP2 and XIAP, by immunocytochemistry, in 30 blood samples from B-CLL patients and correlated protein expression to fludarabine-induced apoptosis estimated by an annexin-V assay. Expression of c-IAP1, c-IAP2 and XIAP were found predominantly in the cytoplasm, and a wide range of staining intensities was observed among distinct samples. No correlation was found between the levels of IAPs expression and prognostic factors such as age, gender, lymphocyte doubling time, white blood cell count or previous treatment. The expression of IAPs also failed to predict the sensitivity to fludarabine-induced apoptosis. Alternative pathways of cell death may explain the independence of fludarabine-induced apoptosis from the high expression of IAPs.

Chronic lymphocytic leukemia: economic burden and quality of life: literature review

The purpose of this review was answer 2 main questions: what is the impact of chronic lymphocytic leukemia (CLL) on the patient's quality of life and how great is the economic burden of this disease on the health care payers and providers. Patients with CLL typically do not receive any treatment soon after the initial diagnosis. Although there is no known cure for CLL yet, when treated, the patients receive aggressive and expensive therapies (eg, chemotherapy or bone marrow transplantation). A rigorous and systematic literature review was performed of English-language articles published in 1990-2002. It was supplemented with additional articles published before 1990 for completeness and additional references to fill the gaps identified in the published medical literature. The literature on the quality of life (QOL) of CLL patients is very limited. We identified only 8 articles, and none of them analyzed the QOL in untreated CLL patients. Because CLL is a disease affecting adults, especially the elderly, all 8 studies measured the QOL in the adult population. QOL difficulties include fear of death and disability, problems gaining employment or health insurance, and fatigue. No specific leukemia or CLL instruments but general QOL instruments (eg, I-HRQL) were identified and some cancer-specific ones (eg, EORTC QLQ-C30, FACT-G, FACT Anemia, FACT-Fatigue). Interestingly, a FACT-Bone Marrow Transplant instrument exists, although we found no study on CLL that used it. Even the literature on the economic burden of CLL is very limited. We identified 13 studies on the cost of CLL: Most of them were cost-identification or cost-comparison studies, and 5 dealt with the cost-effectiveness of medical interventions to treat CLL. Cost drivers identified for CLL were the chemotherapy costs, intravenous immunoglobulin costs, transplantation costs, and costs associated with the differential staining cytotoxicity assay. We identified very few articles on the QOL of CLL patients and therefore cannot draw strong conclusions about the key QOL predictors. Nevertheless, patients with anemia were found to have a better QOL if they had higher hemoglobin counts and good response to erythropoietin treatment. The articles published seem to demonstrate that the older the age of the patient was, the poorer the QOL. The main cost drivers identified for CLL were related to the treatment chosen (eg, chemotherapy, bone marrow transplantation). There are hints that higher costs often result from the delivery of non-optimal therapy that leads to adverse events, infections, and drug resistance. In summary, the impact of this disease on the health care budget of the different health care providers and payers as well as on the patient's QOL is substantially unknown, calling for appropriate economic and QOL studies.

Economic assessment on the management of chronic lymphocytic leukaemia

In the last decade, several new promising treatments for chronic lymphocytic leukaemia (CLL) have been developed. Healthcare costs are increasing and new treatments tend to be very expensive; therefore, information about the cost effectiveness in treatments for CLL is urgently needed. The authors performed a literature review on the currently available economic evaluations on CLL treatments. A total of 65 articles were found, of which 11 could be included. These articles were evaluated on the basis of six methodological requirements for economic evaluations, enabling readers to judge the value of the studies. Only a small amount of information was available on the costs of CLL treatments. Future economic evaluations should be performed according to the methodological requirements for these studies, which should also be properly documented.

Importance of receptor density in alpha radioimmunotherapy in B cell malignancies: an in-vitro study

BACKGROUND

External beam radiotherapy and beta radioimmunotherapy (RIT) are effective treatments for lymphoid malignancies. The development of RIT with alpha emitters is attractive because of the high linear energy transfer (LET) and short path length, allowing higher tumour cell kill and lower toxicity to healthy tissues.

AIM

To assess the binding of rituximab to samples of B cell chronic lymphocytic leukaemia (B-CLL) and splenic lymphoma with villous lymphocytes (SLVL), and to evaluate the induction of apoptosis by conventional therapies as well as with Bi conjugated to rituximab.

METHOD

213Bi was eluted from a 225Ac generator and conjugated to CD20 antibody (rituximab) with CHX-A''-DTPA as chelator. Binding assays with 213Bi-rituximab were correlated to antibody binding capacity obtained by flow cytometry. Apoptosis was scored by flow cytometric analyses of the cells stained with annexin V-FITC and 7-amino-actinomycin D.

RESULTS

Binding of 213Bi-rituximab was significantly lower for B-CLL compared to SLVL samples (12+/-3 and 42+/-10 213Bi atoms per cell, respectively, at 370 kBq.ml(-1)). The induction of apoptosis did not differ significantly between the two groups (B-CLL and SLVL) after external gamma irradiation or treatment with methylprednisolone and fludarabine (17+/-12% and 18+/-11%; 23+/-14% and 21+/-12%; 9+/-9% and 11+/-8%, respectively; all results expressed as percentages of all cells). Rituximab conjugated or not to 213Bi induced significantly more apoptosis in SLVL (42+/-19% and 42+/-17%) compared to B-CLL samples (27+/-12% and 6+/-8%).

CONCLUSION

Binding assays confirm that SLVL samples present more CD20 antigens compared to B-CLL samples. Conventional therapies such as fludarabine, methylprednisolone or external gamma irradiation induce similar responses in the two populations but SLVL samples present higher sensitivity towards 213Bi-rituximab. These data are in favour of alpha-RIT in SLVL patients.

VH gene mutation status and cellular drug resistance in chronic lymphocytic leukaemia

OBJECTIVE

B-cell chronic lymphocytic leukaemia (B-CLL) can be divided into two clinical entities based on the immunoglobulin variable heavy chain (VH) gene mutation status, as cases with unmutated VH genes display a more aggressive disease with shorter survival time than mutated cases. The aim of this study was to investigate whether differences in cellular drug resistance could give an explanation for these divergent clinical courses.

METHODS

The VH gene mutation status was analysed in patients with previously untreated B-CLL using VH gene family-specific PCR amplification and nucleotide sequencing. In vitro sensitivity to cytarabine, fludarabine, cladribine, doxorubicin, idarubicin, vincristine, cyclophosphamide, melphalan and prednisolone was assessed using the non-clonogenic in vitro assay, fluorometric microculture cytotoxicity assay.

RESULTS

The VH genes and in vitro drug resistance were successfully analysed in 46 cases, revealing that 25 (54%) cases showed unmutated and 21 (46%) cases mutated VH genes. Interestingly, the unmutated group generally tended to be more chemosensitive than the mutated group with significant differences for cytarabine and prednisolone (P < or = 0.01).

CONCLUSION

The propensity of inferior drug response in mutated B-CLL may reflect a more differentiated disease than in unmutated B-CLL. We conclude that the difference in prognosis between B-CLL cases with unmutated and mutated VH genes could not be explained by difference in cellular drug resistance.

Changing picture of cellular drug resistance in human leukemia

A relatively well documented and seemingly firm overall picture of mechanisms involved in leukemia-cell drug resistance has evolved since the 1970s, where mechanisms involved in multidrug resistance towards anti-leukemia chemotherapeutic compounds were first described. At that time, based on available data, resistance associated with overexpression of the cell-surface transmembrane ATPase P-glycoprotein (P-170, P-gp, the product of the MDR1 gene) was described as "the" cause of multidrug resistance in cancer cells. However, during the 1980s and later on other mechanisms were described as candidate causes of multidrug resistance in human leukemia. Moreover, research of the past decade has provided us with an enormous increase in the amount of data and knowledge on the cell-biological and--to an even higher extent--the molecular-genetic processes governing cell survival and death in cancer cells. This, in turn, has improved the possibilities of designing and developing better drugs and drug combinations in leukemia. Along this line, based on rational drug design, imatinib, a 2-phenylaminopyrimidine derivative, has very recently been introduced and found to be an efficient inhibitor of the altered tyrosine kinase, which arises as a product of the BCR-ABL fusion transcript in Philadelphia chromosome positive (Ph+) cases of CML. This new compound appears to be the first of a (hopefully) large family of small organic molecules with a more specific inhibiting activity against the pathogenetic defects in leukemia as well as cancer. With this novel compound, as with all other known individual drugs and classes of chemotherapeutic drugs, drug resistance is seen. To what extent drug resistance towards this novel compound (and its successors) will follow patterns of drug resistance that are already known or entirely new mechanisms of drug resistance is yet to be seen.

Adenine deoxynucleotides fludarabine and cladribine induce apoptosis in a CD95/Fas receptor, FADD and caspase-8-independent manner by activation of the mitochondrial cell death pathway

The adenine deoxynucleosides cladribine (2CdA) and fludarabine (FAraA) are DNA-damaging agents that interfere with DNA repair and induce apoptosis in nonproliferating lymphoid cells. Although both drugs are clinically used for the treatment of indolent lymphoproliferative diseases, the pathways of apoptosis induction remain largely unknown. In the present work, we demonstrate that both drugs induce apoptosis independently of death receptor signaling but activate the mitochondrial cell death pathway. To dissect the signaling pathways, we employed Jurkat cells either deficient for FADD or caspase-8 or overexpressing Bcl-2. In Bcl-2 overexpressing cells, apoptosis and cytochrome c release were blocked whereas processing of caspase-9, -3 and -8 was partially inhibited. In contrast, neither the deficiency of FADD or caspase-8 nor the interference with death receptor signaling by neutralizing anti-CD95/Fas antibodies affected cell death. Inhibitor experiments revealed that caspase-8 is processed by caspase-3-like caspases. Moreover, cytochrome c release and processing of caspase-9 and -3 occurred to an equal extent in wild-type FADD -/- and caspase-8 -/- Jurkat cells. Likewise, apoptosis induction by cladribine or fludarabine was not hampered upon inhibition of caspase-8 in MOLT-3 and MOLT-4 cells or overexpression of a dominant-negative FADD mutant in BJAB cells. Thus, we conclude that apoptosis induced by nucleoside analogues is independent from death receptor signaling as well as from a proposed direct effect on APAF-1, but rather follows the mitochondrial signaling pathway of cytochrome c release and subsequent processing of caspase-9 and -3.

Quantitative analysis of nucleoside transporter and metabolism gene expression in chronic lymphocytic leukemia (CLL): identification of fludarabine-sensitive and -insensitive populations

Resistance to fludarabine is observed in the clinic, and molecular predictive assays for benefit from chemotherapy are required. Our objective was to determine if expression of nucleoside transport and metabolism genes was associated with response to fludarabine therapy in patients with chronic lymphocytic leukemia (CLL). CLL cells from 56 patients were collected prior to treatment with fludarabine. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was performed on sample RNA to determine the relative levels of mRNA of 3 nucleoside transporters that mediate fludarabine uptake (human equilibrative nucleoside transporter 1 [hENT1], human equilibrative nucleoside transporter 2 [hENT2], and human concentrative nucleoside transporter 3 [hCNT3]), deoxycytidine kinase (dCK), and 3 5'-nucleotidases (ecto-5'nucleotidase [CD73], deoxynucleotidase-1 [dNT-1], and cytoplasmic high-Km 5-nucleotidase [CN-II]). Two-dimensional hierarchical cluster analysis of gene expression identified 2 distinct populations of CLL. Cluster 2 patients experienced a 3.4-fold higher risk of disease progression than cluster 1 patients (P = .0058, log-rank analysis). Furthermore, independent analysis of the individual genes of interest revealed statistically significant differences for risk of disease progression (adjusted hazard ratios [HRs]) with underexpression of dNT-1 (HR = 0.45; P = .042), CD73 (HR = 0.40; P = .022), and dCK (HR = 0.0.48; P = .035), and overexpression of hCNT3 (HR = 4.7; P = .0007) genes. Subjects with elevated hCNT3 expression experienced a lower complete response rate to fludarabine therapy (11% vs 69%; P = .002). No hCNT3-mediated plasma membrane nucleoside transport was detected in CLL samples expressing hCNT3 message, and hCNT3 protein was localized to the cytoplasm with immunohistochemical and confocal microscopy.

Appraisal of the MTT-based assay as a useful tool for predicting drug chemosensitivity in leukemia

The MTT-based assay relies upon the cellular reduction of tetrazolium salts to their intensely colored formazans. The test is easy to perform in hematological malignancies and is adaptable for high throughput of samples, although there are some minor limitations in its application resulting from metabolic interference. This class of assays are highly accurate for predicting drug resistance, whereas their predictive value for drug sensitivity depends on the type of disease and drug or drug combination used. They have been found to predict clinical response to fludarabine FLD in B-CLL and were useful for predetermining clinical potential of a single drug or drug combination in AML patients. Extensive studies with ALL patients have supported their advantage for selecting effective drug treatment of the disease. To conclude, pretreatment chemosensitivity assays may help in the selection of chemotherapeutic drugs with the greatest likelihood for clinical effectiveness, and in the exclusion of uneffective therapy. This can lead to improved disease management, response, survival and use of financial resources.

Ex vivo analysis of topotecan: advancing the application of laboratory-based clinical therapeutics

Topotecan is currently approved for relapsed small-cell lung cancer and ovarian cancer. Topotecan's efficacy in the second-line setting and novel mechanism of action suggest broad antitumour activity. We utilised a clinically validated, cell-death, ex vivo assay in human tumour explants to examine the activity profile of topotecan alone and in combination with other antitumour agents. Serial dilutions of topotecan alone and in combination with other cytotoxic agents were applied to biopsy specimens of non-small-cell lung cancer (NSCLC) and breast, colon, and prostate cancers. Dose-response curves were interpolated to provide 50% lethal concentrations (LC(50)). The degree of synergy (by median effect) and normalised Z-scores (raw scores converted to relative activity distributed around the mean) were then computed. Single-agent activity was observed for topotecan in all four tumour types. In 57 chemotherapy-naive specimens, NSCLC revealed the highest activity, demonstrated by the lowest LC(50) value (0.26+/-0.06 microg ml(-1); P=0.002). Overall, previously treated and chemotherapy-naive specimens revealed no significant differences in mean LC(50)'s. Synergy was observed for several combinations, including topotecan plus cisplatin in prostate and for topotecan plus 5-fluorouracil in breast cancers. The Z-score analyses conducted suggest activity for previously unexplored drug regimens, including topotecan plus 5-fluorouracil, vinorelbine, and mitomycin-C in NSCLC and breast cancer. Phase II studies are underway to determine the degree to which these ex vivo findings will translate into improved clinical results.

Assay-assisted treatment selection for women with breast or ovarian cancer

Although women suffering from advanced cancer of the breast or ovary are unlikely to be cured, several active agents are available that can prolong their lives. The use of these agents is based on demonstrated benefit in large randomized clinical trials, and the clinical activity of these chemotherapy regimens is initially high, with 60%-70% of patients responding. Unfortunately, their benefit in the second-line setting is often limited, with less than 30% of patients showing significant disease response. Thus some 70% of patients may undergo ineffective treatment during the course of their disease, while still suffering from significant chemotherapy-related toxicity. Having some foreknowledge of a given agent's expected result before its administration would therefore benefit the individual patient. In vitro drug response testing, first developed to assist in the selection of antibiotics for patients with bacterial infections, has recently been demonstrated to accurately predict how cancer patients will respond to chemotherapy. This review discusses the historical development of in vitro testing for cancer patients, some of the pitfalls encountered, and offers an assessment of their current utility. Results of various clinical trials that evaluated correlations between in vitro tumor response and clinical outcomes are described. These data suggest that in vitro drug response assays can accurately predict drug resistance and can identify patients who are more or less likely to benefit from a given agent.

The burden and outcomes associated with four leukemias: AML, ALL, CLL and CML

Given the recent advances in the treatment of hematologic malignancies and the many other treatments on the horizon, physicians and payers will be faced with the critical decisions of when to use new treatments in the clinical pathway and how to allocate healthcare resources. This review will provide an overall context for the clinical, economic and quality of life burden of leukemia, as well as provide cross-analysis among the four major types of leukemia: acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia and chronic myeloid leukemia.

Bax expression correlates with cellular drug sensitivity to doxorubicin, cyclophosphamide and chlorambucil but not fludarabine, cladribine or corticosteroids in B cell chronic lymphocytic leukemia

In B-CLL, non-proliferating B cells accumulate due to defective apoptosis. Cytotoxic therapies trigger apoptosis and deregulation of apoptotic pathways contributes to chemoresistance. Loss of the apoptosis-promoting Bax has been implicated in resistance to cytotoxic therapy. We therefore evaluated ex vivo drug sensitivity of CLL, producing chemoresponse data which are prognostic indicators for B-CLL, in particular in the case of purine nucleoside analogs. To analyze the underlying mechanisms of drug resistance, we compared endogenous Bax and Bcl-2 expression to ex vivo response to eight drugs, and to survival in 39 B-CLL patients. We found that reduced Bax levels correlated well with ex vivo resistance to traditional B-CLL therapies - anthracyclines, alkylating agents and vincristine (all P < 0.04). Surprisingly, no such relationship was observed for the purine nucleoside analogs or corticosteroids (all P > 0.5). Mutational analysis of p53 could not explain the loss of Bax protein expression. Levels of Bcl-2 were not associated with sensitivity to any drug. In contrast to the ex vivo data, neither Bax or Bcl-2 expression nor doxorubicin sensitivity were associated with increased survival whereas sensitivity to fludarabine correlated with better overall survival (P = 0.031). These findings suggest that the resistance to purine nucleoside analogs and corticosteroids in B-CLL is due to inactivation of pathways different from those activated by anthracyclines, vinca alkaloids and alkylating agents and may be the molecular rationale for the efficacy of purine analogs in this disease.

Parameters affecting the ex vivo cytotoxic drug sensitivity of human hematopoietic cells

The drug sensitivity of normal cells provides a baseline for determining the therapeutic index, and therefore the effectiveness, of cytotoxic drugs, yet little is known about the factors that affect normal cell chemosensitivity. Some parameters are known to have a profound effect on tumor cell sensitivity. The purpose of this study was to determine how cytotoxic drug sensitivity of hematopoietic cells isolated from cancer patients was affected by various parameters. These included previous chemotherapy (yes or no), sex, age, tumor type (leukemias or solid tumors), sample source (blood, bone marrow, serous effusions, or tumor biopsies) and predominant cell lineage (lymphoid, myeloid, macrophage, or mixed). Mononuclear cells isolated from blood, bone marrow, serous effusions, and tumor biopsies were incubated for four days with a median of 16 drugs. The differential staining cytotoxicity assay, an ex vivo apoptotic drug sensitivity test in which cell survival is determined morphologically, was used to assess normal hematopoietic and tumor cell response to cytotoxic drugs. One hundred forty-six specimens yielded hematopoietic cell chemosensitivity results with 3-36 drugs. Compared with tumor cells, there was far less interpatient variation in chemosensitivity of hematopoietic cells. Mean hematopoietic cell drug sensitivity showed little variation due to previous chemotherapy, sex, age, tumor type, and sample source or cell lineage. We therefore concluded that cytotoxic drug sensitivity of hematopoietic cells from a variety of sources could be used for assessment of therapeutic index. Drug therapeutic index results are a valuable tool in identifying novel cytotoxic agents and individually tailored chemotherapy regimens.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia continues to attract much basic and clinical research interest. Despite recent advances, the disease still has no established cure. Nonetheless, significant strides have been made in our understanding of the genetics, biology, and clinical staging of this disease. This understanding may improve our ability to segregate patients into subtypes that differ in their cytogenesis, propensity toward disease progression, or response to standard or innovative forms of therapy. Finally, several promising new modalities of treatment are being evaluated in clinical trials, involving novel drugs or drug-combinations, monoclonal antibodies, stem cell transplantation, or gene therapy.

Ex vivo assessment of drug response by differential staining cytotoxicity (DiSC) assay suggests a biological basis for equality of chemotherapy irrespective of age for patients with chronic lymphocytic leukaemia

With a mean age at diagnosis for chronic lymphocytic leukaemia (CLL) of 65 years, development of optimal therapeutic regimens has been hampered by the advanced age of patients. In general, because of comorbidity older patients are not treated with the intent of achieving a complete response and so do not attain the quality of response of younger patients and do not survive as long. We have investigated whether or not ex vivo cellular sensitivity to cytotoxic drugs could be an underlying biological basis for this age differential in response and survival by comparing ex vivo drug response with age in untreated CLL patients. Cells from 365 untreated CLL patients aged 31.1-87.1 years (average 65.3 years) were tested for drug response by differential staining cytotoxicity (DiSC) assay with a panel of 10 drugs. An average of 280 results (range 196-361) obtained for each drug was compared with patient age. For chlorambucil, cyclophosphamide, prednisolone, vincristine, doxorubicin, epirubicin, fludarabine, cladribine and methylprednisolone, no relationship was found between ex vivo drug response and age (r<0.12). For pentostatin, a possible but very weak relationship (r = 0.18; n = 210; P = 0.06) was found. We conclude that cellular sensitivity to cytotoxic drugs does not support the differential treatment of older and younger CLL patients.

Response to cladribine in previously treated patients with chronic lymphocytic leukaemia identified by ex vivo assessment of drug sensitivity by DiSC assay

The ability to identify non-responders to cytotoxic chemotherapy has significant clinical and economic benefits. Differential staining cytotoxicity (DiSC) assays were performed in 34 previously treated patients with chronic lymphocytic leukaemia prior to treatment with cladribine. Of the 28 identified as ex vivo sensitive, 26 achieved a complete (CR) or partial response (PR) (median length of response 1. 5 years, median survival 3.37 years) and two had a >70% fall in lymphocytes: six identified as ex vivo resistant failed to respond. The DiSC assay can accurately identify a subgroup of patients resistant to cladribine.