Chemosensitization and delayed androgen-independent recurrence of prostate cancer with the use of antisense Bcl-2 oligodeoxynucleotides

Timing Is Everything: Preclinical Evidence Supporting Simultaneous Rather Than Sequential Chemohormonal Therapy for Prostate Cancer

PURPOSE

Androgen ablation is the mainstay of systemic therapy for prostate cancer, with cytotoxic therapies reserved for hormone-refractory disease. It is not clear, however, that this is the most appropriate sequence of interventions for this disease. This study addresses the ideal timing of systemic treatments in the Shionogi and LNCaP xenograft models. We explored the hypothesis that stress-induced gene expression changes after chemotherapy can induce a hormone-independent phenotype.

EXPERIMENTAL DESIGN

Three groups of mice bearing either Shionogi or LNCaP xenografts were treated with (a) initial castration and delayed paclitaxel, (b) initial paclitaxel and delayed castration, or (c) simultaneous castration plus paclitaxel. End points were time to tumor progression and time to sacrifice. Microarray and reverse transcription-PCR analyses were carried out to assess changes in gene expression induced by paclitaxel.

RESULTS

Mice receiving simultaneous therapy showed a significant improvement in median time to progression (TTP: Shionogi, 65 versus 38 days, P = 0.004; LNCaP, 105 versus 70 days, P = 0.032) and time to sacrifice (Shionogi, 83 versus 66 days, P < 0.014) versus best sequential therapy. A marked lack of response to castration was observed after initial paclitaxel therapy. Gene expression and reverse transcription-PCR studies confirmed that several genes known to play a role in androgen independence were up-regulated in response to paclitaxel exposure.

CONCLUSIONS

In laboratory models of prostate cancer, simultaneous androgen deprivation plus paclitaxel is more effective than sequential treatments. These findings provide preclinical proof-of-principle for ongoing clinical trials addressing the role and timing of systemic therapies in prostate cancer.

Therapeutic efficacy of adenoviral-mediated p53 gene transfer is synergistically enhanced by combined use of antisense oligodeoxynucleotide targeting clusterin gene in a human bladder cancer model

To establish a more effective therapeutic strategy against advanced bladder cancer, we investigated the effects of combined treatment with antisense (AS) oligodeoxynucleotide (ODN) targeting the anti-apoptotic gene clusterin and adenoviral-mediated p53 gene transfer (Ad5CMV-p53) using the human bladder cancer KoTCC-1 model. Clusterin expression in KoTCC-1 cells was highly upregulated by Ad5CMV-p53 treatment; however, AS clusterin ODN treatment further suppressed clusterin expression in KoTCC-1 cells after Ad5CMV-p53 treatment. AS clusterin ODN treatment synergistically enhanced the cytotoxic effect of Ad5CMV-p53, and DNA fragmentation characteristic of apoptosis was observed only after combined treatment with AS clusterin ODN and Ad5CMV-p53, but not after treatment with either agent alone. Administration of AS clusterin ODN and Ad5CMV-p53 into nude mice resulted in a significant inhibition of KoTCC-1 tumor growth as well as lymph node metastases compared to administration of either agent alone. Furthermore, combined treatment with AS clusterin ODN, Ad5CMV-p53, and cisplatin completely eradicated KoTCC-1 tumors and lymph node metastases in 60% and 100% of mice, respectively. These findings suggest that combined treatment with AS clusterin ODN and Ad5CMV-p53 could be a novel strategy to inhibit bladder cancer progression, and that further additional use of a chemotherapeutic agent may substantially enhance the efficacy of this combined regimen.

Reappraisal of the Concept of Hormone Therapy in Metastatic Prostate Cancer and Implications for Treatment

Almost all prostate cancer patients become resistant to hormonal therapy that blocks androgen-mediated cell proliferation. The key to this resistance may lie in expression of the androgen receptor itself. Alternative methods to block the AR-mediated signaling pathways appear to be critical for tumor survival. These signal transduction pathways that interact with AR may enhance the response to androgen ablation therapy. The identification of signaling pathways may be a major goal in the treatment of prostate cancer. The application of novel therapies must be preceded by the identification of the genetic and molecular tumor profiles for each patient.

Inhibition of cell proliferation in human breast tumor cells by antisense oligonucleotides against facilitative glucose transporter 5

In recent years, successful examples of antisense oligonucleotide (AS) therapy for genetic diseases have stimulated scientists to investigate its application on cancer diseases. AS can be used to down-regulate the mRNA and protein expression by annealing to specific region of the target mRNA which is responsible for the malignancy. Glucose transporter 5 (Glut5) is a tissue specific transporter that can be found on breast cancer tissues but not on normal breast tissues. Therefore, it is of clinical interest to investigate whether AS against Glut5 mRNA can tackle breast cancer. In this study, two cell lines, MCF-7 which is estrogen-receptor positive and MDA-MB-231 which is estrogen-receptor negative, were used to mimic breast cancer tissues at early and late stages, respectively. A 15-base sequence around the start codon of Glut5 was used. It was found that AS against Glut5 exerted anti-proliferative effect on both of these two breast tumor cell lines and seemed to exert its effect via the suppression of expression of Glut5 proteins in the cells. AS against Glut5 exhibited no effect on human hepatoma HepG2 cells which do not possess any Glut5. The results imply an alternative way in treating breast tumor as the AS against Glut5, unlike tamoxifen, takes effect on breast tumor cells via suppressing the expression of Glut5 that they specifically possess, and regardless whether the breast tumors are estrogen dependent or not.

Bcl-2 inhibitors potentiate the cytotoxic effects of radiation in Bcl-2 overexpressing radioresistant tumor cells

PURPOSE

Bcl-2, an inhibitor of apoptosis frequently shows elevated expression in human tumors, thus resulting in resistance to radiation therapy. Therefore, inhibiting Bcl-2 function may enhance the radiosensitivity of tumor cells. Tetrocarcin A (TC-A) and bcl-2 antisense oligonucleotides exhibit antitumor activity by inhibiting Bcl-2 function and transcription, respectively. We investigated whether these antitumor agents would enhance the cytotoxic effects of radiation in tumor cells overexpressing Bcl-2.

METHODS AND MATERIALS

We used HeLa/bcl-2 cells, a stable Bcl-2-expressing cell line derived from wild-type HeLa (HeLa/wt) cells. Cells were incubated with TC-A and bcl-2 antisense oligonucleotides for 24 h after irradiation, and cell viability was then determined. Apoptotic cells were quantified by flow cytometric assay.

RESULTS

The HeLa/bcl-2 cells were more resistant to radiation than HeLa/wt cells. At concentrations that are not inherently cytotoxic, both TC-A and bcl-2 antisense oligonucleotides increased the cytotoxic effects of radiation in HeLa/bcl-2 cells, but not in HeLa/wt cells. However, in HeLa/bcl-2 cells, additional treatment with TC-A in combination with radiation did not significantly increase apoptosis.

CONCLUSIONS

The present results suggest that TC-A and bcl-2 antisense oligonucleotides reduce radioresistance of tumor cells overexpressing Bcl-2. Therefore, a combination of radiotherapy and Bcl-2 inhibitors may prove to be a useful therapeutic approach for treating tumors that overexpress Bcl-2.

Targeting Bcl-2 with oblimersen for patients with hormone refractory prostate cancer

Patients with metastatic hormone refractory prostate cancer (HRPC) have limited treatment options and new therapies are needed. Advances in the understanding of the molecular mechanisms implicated in prostate cancer progression have identified many potential therapeutic gene targets including Bcl-2, an important pro-survival regulator of apoptotic cell death. Bcl-2 is overexpressed in a variety of human malignancies including prostate cancer where it has also been associated with androgen independent progression and treatment resistance. Oblimersen is a phosphorothioate antisense oligonucleotide complimentary to the Bcl-2 mRNA and a potent inhibitor of Bcl-2 expression which in pre-clinical testing can significantly enhance the therapeutic effect of chemotherapy, hormone and radiation therapy. Clinical trials evaluating oblimersen in combination with chemotherapy in a variety of cancers have shown good tolerability and promising response rates. Randomized trials are required to determine if oblimersen can enhance the effectiveness of docetaxel in patients with HRPC.

Synergistic antitumor effect of combined use of adenoviral-mediated p53 gene transfer and antisense oligodeoxynucleotide targeting clusterin gene in an androgen-independent human prostate cancer model

Our recent studies showed that antisense oligodeoxynucleotide targeting antiapoptotic gene, clusterin, enhanced apoptosis induced by conventional therapeutic modalities using several prostate cancer models. In this study, to establish a more effective therapeutic strategy against prostate cancer, we investigated the effect of combined treatment with antisense clusterin oligodeoxynucleotide and adenoviral-mediated p53 gene transfer (Ad5CMV-p53) in an androgen-independent human prostate PC3 tumor model. Treatment of PC3 cells with 500 nmol/L antisense clusterin oligodeoxynucleotide decreased clusterin mRNA by &gt;80% compared with that with 500 nmol/L mismatch control oligodeoxynucleotide. Clusterin mRNA expression in PC3 cells was highly up-regulated by Ad5CMV-p53 treatment; however, antisense clusterin oligodeoxynucleotide treatment further suppressed clusterin expression in PC3 cells after Ad5CMV-p53 treatment. Antisense clusterin oligodeoxynucleotide treatment significantly enhanced the sensitivity of Ad5CMV-p53 in a dose-dependent manner, reducing the IC50 of Ad5CMV-p53 by 75%. Apoptotic cell death was detected after combined treatment but not after treatment with either agent alone. In vivo administration of antisense clusterin oligodeoxynucleotide and Ad5CMV-p53 resulted in a significant inhibition of s.c. PC3 tumor growth as well as lymph node metastases from orthotopic PC3 tumors compared with administration of either agent alone. Furthermore, combined treatment with antisense clusterin oligodeoxynucleotide, Ad5CMV-p53, and mitoxantrone completely eradicated s.c. PC3 tumors and lymph node metastases from orthotopic PC3 tumors in 60% and 100% of mice, respectively. These findings suggest that combined treatment with antisense clusterin oligodeoxynucleotide and Ad5CMV-p53 could be a novel strategy to inhibit progression of hormone-refractory prostate cancer and that further addition of chemotherapeutic agents may help to enhance the efficacy of this combined regimen.

Mechanisms of the development of androgen independence in prostate cancer

The effectiveness of androgen ablation in the management of advanced prostate cancer is of limited duration, with the median length of response being only 18-24 months. The transition of the prostate cancer cell to an androgen independent phenotype is a complex process that involves selection and outgrowth of pre-existing clones of androgen-independent cells (clonal selection) as well as adaptive up-regulation of genes that help the cancer cells survive and grow after androgen ablation (adaptation). These two mechanisms share an important pre-requisite characteristic: prostate cancers are heterogeneous tumours comprised of various subpopulations of cells that respond differently to androgen withdrawal therapy. This tumour heterogeneity may reflect either a multifocal origin, adaptation to environmental stimuli, and/or genetic instability of the initial cancer. This review will reexamine the different mechanisms that enable prostate cancer cells to proliferate in an androgen depleted environment.

Mechanisms of the development of androgen independence in prostate cancer

The effectiveness of androgen ablation in the management of advanced prostate cancer is of limited duration, with the median length of response being only 18-24 months. The transition of the prostate cancer cell to an androgen independent phenotype is a complex process that involves selection and outgrowth of pre-existing clones of androgen-independent cells (clonal selection) as well as adaptive up-regulation of genes that help the cancer cells survive and grow after androgen ablation (adaptation). These two mechanisms share an important pre-requisite characteristic: prostate cancers are heterogeneous tumours comprised of various subpopulations of cells that respond differently to androgen withdrawal therapy. This tumour heterogeneity may reflect either a multifocal origin, adaptation to environmental stimuli, and/or genetic instability of the initial cancer. This review will reexamine the different mechanisms that enable prostate cancer cells to proliferate in an androgen depleted environment.

Use of antisense oligonucleotides targeting the cytoprotective gene, clusterin, to enhance androgen- and chemo-sensitivity in prostate cancer

The discovery and targeting of genes mediating androgen-independence may lead to the development of novel therapies that delay progression of hormone refractory prostate cancer (HRPC). Clusterin is a stress-associated cell survival gene that increases after androgen ablation. Here, we review clusterin's functional role in apoptosis and the use of antisense oligonucleotides (ASOs) against clusterin to enhance apoptosis in prostate cancer models. Immunostaining of tissue microarrays constructed from untreated and post-hormone treated radical prostatectomy specimens confirm that clusterin is highly expressed in virtually all HRPC cells, 80% of prostate cancer cells after neoadjuvant hormone therapy, but is low or absent (<20%) in untreated specimens. Overexpression of clusterin in LNCaP cells confers resistance to both androgen ablation and chemotherapy. Clusterin ASOs reduced clusterin levels in a dose-dependent and sequence-specific manner. Adjuvant treatment with murine clusterin ASOs after castration of mice bearing Shionogi tumors decreased clusterin levels, accelerated apoptotic tumor regression, and significantly delayed the recurrence of androgen-independent tumors. A human clusterin ASO targeting the translation initiation site and incorporating MOE-gapmer backbone (OGX-011) synergistically enhanced the cytotoxic effects of paclitaxel in human xenografts of prostate, renal cell, bladder, and lung cancer. Clusterin, is an anti-apoptosis protein upregulated in an adaptive cell survival manner by androgen ablation and chemotherapy that confers resistance to various cell death triggers. Suppression of clusterin levels using ASOs enhances cell death following treatment with androgen ablation, radiation, and chemotherapy.

Combined targeting of epidermal growth factor receptor and MDM2 by gefitinib and antisense MDM2 cooperatively inhibit hormone-independent prostate cancer

PURPOSE

The epidermal growth factor receptor (EGFR) may play a relevant role in the progression, hormone therapy resistance, and prognosis of prostate cancer patients. Also MDM2, a negative p53 regulator that interacts with retinoblastoma (Rb), E2F, p19(arf) and the ras-mitogen-activated protein kinase(MAPK) cascade plays an important role in prostate cancer progression and prognosis. On the basis of the EGFR and MDM2 role in integrating signaling pathways critical for prostate cancer progression, we investigated whether their selective combined blockade may have a cooperative antitumor effect in prostate cancer. For this purpose, we have used the EGFR tyrosine kinase inhibitor gefitinib (ZD1839, Iressa) and a second generation hybrid oligonucleotide antisense MDM2 (AS-MDM2), respectively.

EXPERIMENTAL DESIGN

Gefitinib and AS-MDM2 were administered to hormone-refractory and hormone-dependent human prostate cancer cells in vitro and to mice bearing tumor xenografts, evaluating the effects on growth, apoptosis, and protein expression, in vitro and in vivo.

RESULTS

We demonstrated that the combination of gefitinib and AS-MDM2 synergistically inhibits the growth of hormone-independent prostate cancer cells in vitro. This effect is accompanied by the inhibition of MDM2, phosphorylated Akt (pAkt), phosphorylated MAPK (pMAPK), and vascular endothelial growth factor (VEGF) expression and by Rb hypophosphorylation. The combination of the two agents in nude mice bearing the same hormone-independent tumors caused a potent cooperative antitumor effect. Tumor samples analysis confirmed the inhibition of MDM2, pAkt, pMAPK, VEGF, and basic fibroblast growth factor expression.

CONCLUSIONS

This study shows that EGFR and MDM2 play a critical role in the growth of prostate cancer, especially hormone-dependent, and that their combined blockade by gefitinib and AS-MDM2 causes a cooperative antitumor effect, supporting the clinical development of this therapeutic strategy.

Expression of biomarkers modulating prostate cancer progression: implications in the treatment of the disease

OBJECTIVES

To determine whether COX-2, bcl-2 and neoangiogenesis are related to human prostate cancer relapse after definitive surgical treatment and progression toward androgen independence and to evaluate the association between the patterns of these tumoral biomarkers and other standard clinico-pathological parameters (such as Gleason score, PSA, TNM stage).

MATERIALS AND METHODS

We retrospectively analyzed the records on 126 prostate cancer samples from patients treated at our University Hospital from 1995 to 2002. The 72 patients with clinically localized disease (group 1) had undergone radical prostatectomy. Another 54 patients (group 2) had metastatic androgen-independent disease. Archived material relating to the subjects was then immunostained for bcl-2, COX-2 and CD-31, using an anti-bcl-2 monoclonal primary antibody, an anti-COX-2 polyclonal rabbit antibody and an anti-CD-31 monoclonal mouse antibody to evaluate neoangiogenesis (MVD, microvessel density).

RESULTS

We found that bcl-2, COX-2 and MVD expression increased from group 1 to group 2. The intergroup difference was significant only for high MVD (P < 0.05). On the other hand, high MVD, high bcl-2 and high COX-2 expression was correlated with a higher PSA level (P < 0.01), whereas only a high MVD was also related with Gleason score (P < 0.05). We used univariate analysis to evaluate the prognostic impact of biologic and clinico-pathologic parameters on the disease-free-survival of 72 patients treated by radical prostatectomy. A total of 30 patients (41.6%) experienced biochemical relapse; bcl-2, COX-2 and MVD significantly correlated with disease relapse in these patients. In fact, we observed disease relapse in 24/45 (53%) with high bcl-2 expression, in 15/21 (71%) with a high MVD count and finally, in 30/58 (52%) with high COX-2 expression. Finally, PSA value and Gleason score were the only two biologic markers significantly associated to disease relapse in a multivariate analysis.

CONCLUSIONS

Our results strongly support a role for bcl-2, COX-2 and angiogenesis in the development and progression of prostate cancer. Of course, we are aware of the small sample size considered in our study. Further investigations would better clarify the prognostic and therapeutic implications of these findings.

Inhibition of bcl-2 enhances the efficacy of chemotherapy in renal cell carcinoma

OBJECTIVES

Renal cell cancer (RCC) is highly resistant to chemotherapy. Increased expression of the antiapoptotic gene bcl-2 in tumors is known to be associated with poor responses to systemic treatment of cancer. Down-regulation of bcl-2 expression using antisense oligonucleotides (asON) has been shown to increase chemosensitivity in clinical phase I-III studies with various cancers. However, no studies on the efficacy of this approach in RCC have been reported so far. This study aimed to evaluate whether bcl-2 asON could enhance efficacy of chemotherapy in human RCC.

MATERIAL AND METHODS

Expression of bcl-2 mRNA and protein was analyzed in different RCC cell lines by RT-PCR and Western blot. Cells with high or low bcl-2 mRNA and protein expression were treated with different concentrations of bcl-2 asON in combination with cisplatin. AsON-induced down-regulation of bcl-2 mRNA and protein was documented by RT-PCR and Western blot. Treatment effects on cell viability were analyzed by colorimetric tetrazolium (MTT) assay. Immunohistochemical staining of M30-positive cells was performed for quantification of apoptotic cells.

RESULTS

Transfection of high bcl-2 expressing cells with bcl-2 asON alone induced no reduction of cell viability at a concentration range from 100-1000 nM. In combination therapy, pretreatment with asON significantly enhanced MTT reduction after cisplatin treatment. IC50 concentrations of cisplatin were 1 microg/ml with and 2.7 microg/ml without prior incubation. The marked reduction of cell viability correlated with an 8-fold increase of apoptotic cells after combination treatment. Only a minor increase of cisplatin effectivity was noted after asON preincubation of cells with lower bcl-2 expression.

CONCLUSIONS

The combination of cisplatin and bcl-2 antisense ON exerts significantly greater effects on cell viability and apoptosis than either agent used alone on human RCC cells. These data indicate that inhibition of bcl-2 expression may be an attractive therapeutic strategy in RCC tumors with high bcl-2 expression.

Antitumor effect of simultaneous transfer of interleukin-12 and interleukin-18 genes and its mechanism in a mouse bladder cancer model

BACKGROUND

The objectives of this study were to evaluate the antitumor effects of the simultaneous introduction of interleukin 12 (IL-12) and IL-18 genes into a mouse bladder cancer cell line (MBT2). We intended to compare these with those of either gene alone and to investigate the mechanism of the effects induced by the transfer of IL-12 and/or IL-18 genes in this model system.

METHODS

We transfected the IL-12 and/or IL-18 genes into MBT2 cells by the liposome-mediated gene transfer method. We confirmed the secretion of IL-12 and/or IL-18 by enzyme-linked immunosorbent assay. Parental (MBT2/P), IL-12-transfected (MBT2/IL-12), IL-18-transfected (MBT2/IL-18) or both IL-12- and IL-18-transfected (MBT2/Both) cells were subcutaneously or intravenously injected into syngeneic C3H mice. To analyze the mechanism of tumor rejection, these clones were subcutaneously injected into naive nude mice and those depleted with natural killer (NK) cells by antibody.

RESULTS

MBT2/IL-12, MBT2/IL-18 and MBT2/Both were completely rejected when they were injected subcutaneously or intravenously into syngeneic mice. However, MBT2/IL-12, but not MBT2/IL-18, could grow in nude mice. Moreover, the antitumor effect of MBT2/IL-18 was partially abrogated when injected into nude mice of which NK cells were depleted by antibody treatment. MBT2/Both was completely rejected in both nude mice with and without NK cells.

CONCLUSION

The results of the present study indicate that T cells and NK cells seem to play important roles in the antitumor effects by the secretion of IL-12 and IL-18, respectively, and MBT2/Both possesses both mechanisms.

Changes in gene expression induced by phosphorothioate oligodeoxynucleotides (including G3139) in PC3 prostate carcinoma cells are recapitulated at least in part by treatment with interferon-beta and -gamma

PURPOSE

G3139 is an antisense bcl-2 phosphorothioate oligodeoxyribonucleotide that is currently being evaluated in Phase III clinical trials in several human cancers. The aim of the present work was to further identify the apparent non-bcl-2-dependent mechanism of this action of this compound in PC3 prostate cancer cells.

EXPERIMENTAL DESIGN

We performed Affymetrix U95A oligonucleotide microarray studies on mRNA isolated from cells treated with G3139 and related oligonucleotides.

RESULTS

Hierarchical clustering revealed the presence of a set of genes of which the expression was elevated on both 1 and 3 days after oligonucleotide treatment. Significantly, the persistence of expression of the up-regulation of these genes, many of which are members of the IFN cascade, was greater for G3139 than for any other oligomer evaluated. Furthermore, many of the genes with the greatest up-regulation of expression are also those of which the expression is up-regulated after treatment of cells with IFNs. Treatment of PC3 cells with either IFN-beta or -gamma recapitulated some of the aspects of the molecular and phenotypic changes observed after treatment with a G3139/Lipofectin complex. These include down-regulation of bcl-2 protein expression itself, down-regulation of protein kinase C alpha protein expression (but not that of other protein kinase C isoforms), alteration in p21/Waf1/Cip1 protein expression, up-regulation of MHC-I cell surface expression, and profound suppression of cell growth in the absence of a notable increase in cellular apoptosis. However, G3139 (when complexed with Lipofectin) did not induce the up-regulation of expression of either type I or type II IFNs, nor could IFNs be found in conditioned media from treated cells.

CONCLUSIONS

Oligonucleotide microarray experiments demonstrated that G3139 could induce elements of the IFN cascade in PC3 cells in vitro. In addition, the cellular phenotype obtained after treatment with exogenous IFN could, at least in part, recapitulate that obtained after G3139 treatment. Nevertheless, the oligonucleotide microarray experiments we performed also demonstrated that there are extremely large qualitative and quantitative differences between the two treatments.

Therapeutic potential of antisense Bcl-2 as a chemosensitizer for cancer therapy

Bcl-2 protein plays a critical role in inhibiting anticancer drug-induced apoptosis, which is mediated by a mitochondria-dependent pathway that controls the release of cytochrome c from mitochondria through anion channels. Constitutive overexpression of Bcl-2 or unchanged expression after treatment with anticancer drugs confers drug resistance not only to hematologic malignancies but also to solid tumors. The down-regulation of Bcl-2 protein by the antisense (AS) Bcl-2 (oblimesen sodium) may be a useful method for targeting the antiapoptotic protein and thereby increasing the chemotherapeutic effect of anticancer drugs. Several randomized, controlled, Phase III trials have compared standard chemotherapy with a combination of AS Bcl-2 and standard chemotherapy for the treatment of patients with chronic lymphocytic leukemia, multiple myeloma, malignant melanoma, and nonsmall cell lung carcinoma. Nonrandomized clinical trials and preclinical evaluations of AS Bcl-2 also are underway for patients with other malignancies. Here, the authors review the current clinical and preclinical evaluations of AS Bcl-2 and discuss its potential to act as a chemosensitizer and to enhance the therapeutic effect of cancer chemotherapy.

Tissue oxygen tension measurements in the Shionogi model of prostate cancer using 19F MRS and MRI

OBJECTIVES

To investigate changes in tumour tissue oxygenation throughout the tumour growth-regression-relapse cycle in an androgen-dependent animal tumour model.

MATERIALS AND METHODS

19F T1 relaxometry of Perfluoro-15-Crown-5-Ether was used to measure in vivo partial oxygen pressure (pO2) of Shionogi tumours on a 2.35-T MR scanner. Perfluoro-15-Crown-5-Ether was administered as an emulsion injected intravenously or as a neat compound injected directly into the tumour. Non-localized, tumour 19F T1 measurements, made at multiple time points throughout the tumour cycle, were translated into pO2 levels.

RESULTS

No correlation between tumour size and pO2 values was found. Values of pO2 for growing tumours (50 +/- 30 torr) were significantly lower than for regressing and relapsing tumours after 9 days post-castration (70 +/- 10 torr, p<0.05). Maximum pO2 values (90 +/- 30 torr) were reached between fifth and eighth day post-castration, when tumour pO2 was significantly higher than both pre-castration (p<0.001) and after 9 days post-castration (p<0.05).

CONCLUSION

We demonstrate that longitudinal pO2 measurements in vivo are feasible. Values of pO2 for growing androgen-dependent tumours were significantly lower than for regressing and relapsing androgen-independent tumours. These results have potential clinical importance in optimizing the timing of chemotherapy and/or radiotherapy of hormone dependent tumours.

A phase I trial of a Bcl-2 antisense (G3139) and weekly docetaxel in patients with advanced breast cancer and other solid tumors

PURPOSE

Expression of the Bcl-2 protein confers resistance to various apoptotic signals. G3139 [oblimersen sodium (Genasense)] is a phosphorothioate antisense oligodeoxynucleotide that targets Bcl-2 mRNA, downregulates Bcl-2 protein translation, and enhances the antitumor effects of subtherapeutic doses of docetaxel (Taxotere).

PATIENTS AND METHODS

We performed a phase I trial to determine the maximum tolerated dose (MTD) and safety profile of combined therapy with G3139 and weekly docetaxel in patients with advanced Bcl-2-positive solid tumors. Cohorts of three to six patients were enrolled to escalating doses of G3139 and a fixed dose of weekly docetaxel using either of two schedules. In part I, G3139 was administered by continuous infusion for 21 days (D1-22), and docetaxel (35 mg/m2) was given weekly on days 8, 15 and 22. In part II, G3139 was given by continuous infusion for 5 days before the first weekly dose of docetaxel, and for 48 h before the second and third weekly docetaxel doses. For both schedules, cycles were repeated every 4 weeks.

RESULTS

Twenty-two patients were enrolled. Thirteen patients were treated on the part I schedule with doses of G3139 escalated from 1 to 4 mg/kg/day. Nine patients were on the part II schedule of shorter G3139 infusion at G3139 doses of 5-9 mg/kg/day. Hematologic toxicities were mild, except for one case of persistent grade 3 thrombocytopenia in part I. The most common adverse events were cumulative fatigue and transaminase elevation, which prevented further dose escalation beyond 4 mg/kg/day for 21 days with the part I schedule. In part II of the study, using the abbreviated G3139 schedule, even the highest daily doses were tolerated without dose-limiting toxicity or the need for dose modification. Objective tumor response was observed in two patients with breast cancer, including one whose cancer previously progressed on trastuzumab plus paclitaxel. Four patients had stable disease. Pharmacokinetic results for G3139 were similar to those of other trials.

CONCLUSIONS

G3139 in combination with standard-dose weekly docetaxel was well tolerated. The shortened and intermittent G3139 infusion had less cumulative toxicities and still allowed similar total G3139 delivery as the longer infusion. Further studies should examine the molecular effect of the regimen, as well as clinical activities in malignancies for which taxanes are indicated.

Development of Rationally Designed, Target-Based Agents for the Treatment of Advanced Colorectal Cancer

Although there have been several recent additions to the conventional armamentarium used to treat patients with advanced colorectal cancer, principally as a result of the development of selective and nonselective pharmacologic agents and antibodies, the general outcome of patients with advanced disease is still poor. However, a greater understanding of cancer biology, as well as major advances in biotechnology, is beginning to identify and characterize molecular aberrations that are common in patients with colorectal cancer. These advances have resulted in the development of a wide range of rationally designed, target-based anticancer therapeutic agents, which, by virtue of their selectivity, would be expected to produce less nonspecific toxicity and therefore higher therapeutic indices compared with nonspecific cytotoxic agents. This review will discuss several novel targets and therapeutic agents, particularly those designed to interrupt aberrant signal transduction and apoptotic processes. It will also emphasize the complexity of these systems and the need to incorporate novel clinical development paradigms based on a thorough scientific understanding of these targets.

Imatinib Mesylate in Combination with Other Chemotherapeutic Agents for Chronic Myelogenous Leukemia

Imatinib therapy is an important contribution to the management of patients with chronic myelogenous leukemia (CML). Despite high rates of hematologic and cytogenetic responses to imatinib therapy, the emergence of resistance to imatinib has been recognized as a major problem in the treatment of CML. Experimental and clinical studies suggest that imatinib as a single drug may not be sufficient to eradicate BCR-ABL-positive stem cells. Therefore, whether combinations of imatinib with other agents can increase the length of molecular remission and whether such combinations can prolong survival should be determined by large-scale clinical studies. In this review, we discuss efficacious combinations for future clinical trials. These regimens combine imatinib with conventional chemotherapeutic agents or with inhibitors of other signal transduction molecules that may be preferentially activated in CML cells.

Antisense therapy: recent advances and relevance to prostate cancer

Currently employed treatment options for patients with advanced and metastatic cancer such as surgery, radiation, hormone therapy, and chemotherapy are limited. In particular, the well known limitations of chemotherapy are at least in part due to a lack of specificity. The activation of dominant oncogenes and inactivation of tumor suppressor genes may represent novel targets for cancer therapy. Antisense therapy has been widely used to specifically and selectively inhibit the expression of selected genes at the messenger RNA level. Combinations of antisense oligonucleotides with chemotherapeutic agents may offer important advantages in cancer treatment. Several antisense drugs, especially oblimersen (G3139), have shown interesting results in experiments in animals, and have entered clinical trials. However, control oligonucleotides must be carefully chosen to separate antisense effects from the many potential nonspecific effects of oligonucleotides. This review summarizes the advantages and limitations of antisense therapy and its use in the treatment of androgen-independent prostate cancer.

Molecular mechanisms of resistance of leukemia to imatinib mesylate

Despite high rates of hematologic and cytogenetic responses to imatinib therapy, the emergence of resistance to imatinib has been recognized as a major problem in the treatment of Ph-positive leukemia. The high frequency of BCR-ABL mutations and amplifications represents the high degree of heterogeneity in patients with advanced phase of CML, in whom multiple leukemic clones may exist. Therefore, a single inhibitor is unlikely to able to block all mutants.

Nucleotide-based therapies targeting clusterin chemosensitize human lung adenocarcinoma cells both in vitro and in vivo

Introduction: Lung cancer is highly lethal and resistant to most anticancer interventions. Treatment resistance is mediated, in part, by enhanced expression of cell survival proteins that help facilitate tumor progression. Clusterin is a stress-associated cytoprotective protein up-regulated by various apoptotic triggers in many cancers and confers treatment resistance when overexpressed. The objectives in this study were to evaluate clusterin expression levels in human lung cancer tissue, and to test effects of clusterin silencing using antisense oligonucleotides (ASOs) and short interfering double-stranded RNAs (siRNAs) on chemosensitivity in human lung cancer A549 cells. Methods: Clusterin immunostaining was evaluated in a tissue microarray of 149 spotted human lung cancers. The effects of clusterin ASO or siRNA treatment on clusterin expression and chemosensitivity to paclitaxel was examined in A549 cells in vitro while the ability of clusterin ASO to chemosensitize in vivo was evaluated in immunocompromised mice bearing A549 tumors. Results: More than 80% of human non-small cell lung cancers are immunoreactive for clusterin. Clusterin ASO or siRNA decreased clusterin mRNA expression in A549 cells &gt;75% in a dose-dependent, sequence-specific manner, and significantly enhanced chemosensitivity to paclitaxel in vitro. Characteristic apoptotic DNA laddering was observed after combined treatment with ASO plus paclitaxel, but not with either agent alone. In vivo administration of clusterin ASO, compared to mismatch control oligonucleotide, synergistically enhanced the effects of paclitaxel or gemcitibine to significantly delay A549 tumor growth. Conclusion: These findings identify clusterin as a valid therapeutic target in strategies employing novel multimodality therapy for advanced lung cancer.

Society of Urologic Oncology position statement: Redefining the management of hormone-refractory prostate carcinoma

Because patients with hormone-refractory prostate carcinoma are a very diverse group, management of these patients represents a unique challenge. Despite much research, to the authors' knowledge few studies published to date have provided definitive treatment answers. The Society of Urologic Oncology (SUO) convened a multidisciplinary panel of urologists, oncologists, and radiation oncologists to develop a treatment algorithm for patients with hormone-refractory prostate carcinoma. The resulting treatment outline was based on a review of the literature review and on the expert opinions of the panelists. The current article provided a logical progression of treatment choices that included hormonal manipulations, chemotherapeutic options, and adjunctive therapies. Future clinical trials and therapies were also discussed by the authors. Management strategies should be targeted toward the individual patient. Although significant progress has been made in understanding and treating hormone-refractory prostate carcinoma, earlier interventions would be ideal and better therapeutic approaches to prolong survival are necessary.

The future of antisense therapy: combination with anticancer treatments

The current direction in cancer research is rational drug design, which is based on the evidence that transformed cells are characterized by alterations of genes devoted to the regulation of both cell proliferation and apoptosis. A variety of approaches have been carried out to develop new agents selective for cancer cells. Among these, antisense oligonucleotides (ASOs) are one of such class of new agents able to inhibit specifically the synthesis of a particular cancer-associated protein by binding to protein-encoding RNA, thereby preventing RNA function. In the past decade, several ASOs have been developed and tested in preclinical and clinical studies. Many have shown convincing in vitro reduction in target gene expression and promising activity against a wide variety of tumors. However, because of the multigenic alterations of tumors, the use of ASOs as single agents does not seem to be effective in the treatment of malignancies. Antisense therapy that interferes with signaling pathways involved in cell proliferation and apoptosis are particularly promising in combination with conventional anticancer treatment. An overview of the progress of ASOs used in combination therapy is provided.

Inhibition of PC-3 prostate cancer cell growth in vitro using both antisense oligonucleotides and taxol

Antisense oligonucleotides (oligos) directed against mRNA-encoding transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor (EGFR) have demonstrated in vitro and in vivo efficacy against prostate cancer tumor models. However, many therapeutic agents have increased effectiveness when given in combination with other more established agents. We evaluated the effectiveness of two oligos (3.32 and 6.64 microM/L) known to have significant activity against the PC-3 prostate cell line in combination therapy with the chemotherapeutic agent paclitaxel (Taxol) (2.5 and 5.0 nm). Therapy was evaluated when oligos and Taxol were administered either as (1) single agents, (2) simultaneously in a combined therapy, or (3) sequentially, a form of combination therapy with both agents being administered in a series. We found that when either of the two oligos were given simultaneously with Taxol, no synergistic activity was noted. However, when sequentially administered in a series 1 d apart, a pretreatment with the antisense directed against TGF-alpha (6.64 microM/L) followed by Taxol (5 nm) had significantly greater activity than these agents similarly administered in the reverse order or simultaneously.>

A small inhibitor of the interaction between Bax and Bcl-X(L) can synergize with methylprednisolone to induce apoptosis in Bcl-X(L)-overexpressing breast-cancer cells

PURPOSE

To identify inhibitors of the interaction between Bax and Bcl-X(L).

METHODS

Using an assay based on biosensor technology, we screened a chemical library of 10,000 compounds for inhibitors of the interaction between Bax and Bcl-X(L). Using cell-culture systems we tested active compounds for their ability to induce apoptosis in Bcl-X(L)-overexpressing MCF7 cells and increase the sensitivities of the cells to apoptosis-inducing drugs [vincristine sulphate, dexamethasone, cycloheximide and 6alpha-methylprednisolone (MP)].

RESULTS

A single compound, 2',4',5',7'-tetrabromofluorescein (A5), from the library was found to inhibit this interaction efficiently. Several structural analogues of A5 were tested and two of these [4',5'-dibromofluorescein (A9) and 3,4,5,6-tetrabromofluorescein (A11)] were found to be active, and their activities were confirmed by an independent in vitro pull-down assay. These active compounds were observed to induce apoptosis in Bcl-X(L)-overexpressing MCF7 cells. Moreover, two of the compounds (A5 and A11) appeared to increase the sensitivities of the cells to MP. A more rigorous test using the isobologram technique showed that there is a synergistic cytotoxic effect between A11 and MP.

CONCLUSIONS

We have identified a small inhibitor of the interaction between Bax and Bcl-X(L) that can synergize with methylprednisolone to induce apoptosis in Bcl-X(L)-overexpressing breast-cancer cells.

Potentiation of dexamethasone-, paclitaxel-, and Ad-p53-induced apoptosis by Bcl-2 antisense oligodeoxynucleotides in drug-resistant multiple myeloma cells

Overexpression of Bcl-2 in myeloma cells results in resistance to drugs such as dexamethasone (DEX), adenovirus-mediated delivery of p53 (Ad-p53), and paclitaxel (TAX), which work through the intrinsic apoptotic pathway. Bcl-2 antisense oligodeoxynucleotides (Bcl-2-ASO) have been shown to induce apoptosis in cancer cells, as a single agent or, better, in combination with chemotherapy. We hypothesized that down-regulation of Bcl-2 by Bcl-2-ASO will sensitize drug-resistant myeloma cells to undergo apoptosis. In this paper we report a detailed time/dose study of the effect of Bcl-2-ASO on myeloma cells with varying levels of Bcl-2. Treatment of myeloma cells expressing relatively low levels of Bcl-2 with Bcl-2-ASO resulted in a substantial apoptosis concomitant with a substantial depletion of Bcl-2 protein. Maximal apoptosis was observed at 5 to 10 microg/mL Bcl-2-ASO, following 4 days of treatment. Down-regulation of Bcl-2 and apoptosis were time and dose dependent and were sequence specific. In these cell lines, apoptosis was accompanied by activation of caspase-9 and caspase-3 and by release of cytochrome c to the cytosol. In contrast, high Bcl-2-expressing myeloma cells were practically resistant to Bcl-2-ASO. Most important, however, pretreatment of myeloma cells expressing high levels of Bcl-2 with Bcl-2-ASO increased the extent of DEX-, TAX-, and Ad-p53-induced apoptosis from 10%-20% to 70%-90%. Increased apoptosis was accompanied by additional decrease in Bcl-2 protein. Similar results for down-regulation of Bcl-2 and apoptosis were obtained with freshly isolated myeloma cells. These data support development of clinical trials with combinations of Bcl-2-ASO and DEX, TAX, or Ad-p53 in the treatment of refractory myeloma patients.

Regulation of Bcl-2 expression by dihydrotestosterone in hormone sensitive LNCaP-FGC prostate cancer cells

PURPOSE

Up-regulation of the anti-apoptotic bcl-2 proto-oncogene is associated with androgen independent prostate cancer progression. This observation suggests that the expression of bcl-2 may be negatively regulated by androgens in prostate cancer cells.

MATERIALS AND METHODS

The expression of the proto-oncogene bcl-2 was assessed in the hormone sensitive prostate cancer cell line LNCaP-FGC in the presence and absence of a physiological concentration of 1 nM. dihydrotestosterone (DHT). Sequence analysis of the bcl-2 promoter regions demonstrated the presence of 2 potential androgen response elements. Transient transfections of luciferase reporter constructs containing these potential androgen response elements into LNCaP-FGC cells in the presence and absence of DHT were performed. Steady-state transcripts of bcl-2 were assessed using RNase protection assays.

RESULTS

Cells cultured in charcoal stripped serum in the presence of DHT resulted in down-regulation of bcl-2 protein. Down-regulation of bcl-2 protein and mRNA by DHT was inhibited by coincubation with the antiandrogen bicalutamide, an agent that competitively inhibits binding of DHT to androgen receptor. Luciferase reporter constructs containing candidate androgen response elements were transrepressed in the presence of DHT. Bcl-2 mRNA was also down-regulated by DHT and this down-regulation could not be abolished by cycloheximide.

CONCLUSIONS

Together these results suggest that the suppression of bcl-2 expression by DHT in hormone sensitive LNCaP-FGC prostate cancer cells occurs directly. In addition, these results provide a possible mechanistic basis for the up-regulation (derepression) of bcl-2 observed in hormone independent prostate cancers.

Chemosensitization of human prostate cancer using antisense agents targeting the type 1 insulin-like growth factor receptor

OBJECTIVE

To assess the effect of the downregulation of type 1 insulin-like growth factor receptor (IGF1R) on the chemosensitivity of prostate cancer cells. IGF1R is overexpressed by prostate cancer compared with benign prostatic epithelium and IGF1R expression commonly persists in androgen-independent metastatic disease at levels comparable to those in the primary.

MATERIALS AND METHODS

Human androgen-independent DU145 prostate cancer cells were transfected with IGF1R antisense oligonucleotides or antisense RNA. Transfected cultures were treated with cisplatin, mitoxantrone, paclitaxel or vehicle control, and survival measured using a clonogenic assay.

RESULTS

Both antisense strategies suppressed IGF1R protein levels to 30-50% of those in control cultures. This was associated with 1.5-2-fold enhancement of sensitivity to cisplatin, mitoxantrone and paclitaxel, and an increase in cisplatin-induced apoptosis.

CONCLUSION

This approach has potential for development as a clinical treatment for advanced prostate cancer and other chemoresistant tumours.

Antisense oligonucleotide therapy for urologic tumors

Modulation of gene expression using antisense oligonucleotides has advanced from the laboratory to the clinic. Numerous companies can, at least partially, attribute their success to the development of antisense techniques, and one antisense drug is currently on the market. Antisense compounds have been used in clinical trials that included patients with urologic tumors, mostly directed at proliferation- or apoptosis-related targets. Furthermore, therapeutic inhibition of many new identified genes is being investigated in preclinical tests. This review provides a contemporary overview of current preclinical and clinical antisense oligonucleotide concepts for the treatment of urologic tumors.

Regulators of apoptosis as anticancer targets

For the majority of patients with advance malignancies, current therapies are noncurative. Developing therapeutic agents that enhance the apoptotic effects and hence antitumor potential of currently available chemotherapy agents represents a rationale investigative strategy. Several chemotherapeutic agents including antimicrotubule agents and all-trans-retinoic acid utilize these pathways to mediate tumor cell killing. With specific agents such as oblimersan sodium in randomized "pivotal" studies, and agents targeting the TRAIL receptor-family recently entering early clinical study, cautious optimism is warranted.

Role of prostate stem cell antigen in prostate cancer research

PURPOSE OF REVIEW

The identification of cell surface antigens is critical to the development of future prognostic and therapeutic modalities for the treatment of prostate cancer. Several prostate-specific proteins have been identified and are under investigation. This review reports on prostate stem cell antigen (PSCA), a protein with restricted expression that may have prognostic and therapeutic utility.

RECENT FINDINGS

PSCA is a glycosylphosphatidylinositol-anchored cell-surface protein belonging to the Ly-6/Thy-1 family of cell surface antigens, and a murine homologue has been described. It is expressed in the normal human prostate and overexpressed in human prostate cancers. Its overexpression has been correlated with increased Gleason score, advanced stage and bone metastasis. PSCA is co-amplified with MYC, an independent predictor of progression and death. PSCA may therefore be a useful predictor of tumor biology and a useful target of immunotherapy against prostate cancer. Evidence suggests a potential role in strategies employing cytotoxic T cell lymphocytes. Anti-tumor activity has been demonstrated with monoclonal antibodies in tumor take and established tumor xenograft models. Conjugated antibody has recently been reported to have anti-tumor activity in preclinical models.

SUMMARY

PSCA may serve as a tool in refining the prognosis of an individual cancer and may be a useful therapeutic target for immunotherapy. Future studies will be required to confirm its clinical utility as a prognostic factor. Future animal and clinical studies will be required to test various immunotherapy strategies for safety and efficacy. The study of PSCA regulation and expression may provide information on normal prostate development and prostate carcinogenesis.

Increase in therapeutic index of doxorubicin and vinblastine by aptameric oligonucleotide in human T lymphoblastic drug-sensitive and multidrug-resistant cells

Aptameric GT oligomers are a new class of potential anticancer molecules that inhibit the growth of human cancer cell lines by binding to specific nuclear proteins. We demonstrated that an aptameric GT oligonucleotide increased the therapeutic index of doxorubicin and vinblastine in T lymphoblastic drug-sensitive and multidrug-resistant (MDR) cells. The doxorubicin ID50 decreased 6.5-fold by coadministration of 1 microM GT to CCRF-CEM cells and by 24-fold by coadministration of 0.75 microM GT to CEM-VLB300 cells. In CEM-VLB300 cells, the vinblastine ID50 decreased 11-fold by coadministration of 0.5 microM GT. Control CT sequence did not potentiate the drugs in either CCRF-CEM or CEM-VLB300 cells. The ability of GT to bind to specific nuclear proteins in cancer cells related to the increase in the therapeutic index of doxorubicin and vinblastine. No cooperation was detected by the administration of GT oligomer together with doxorubicin to rat differentiated thyroid FRTL-5 cells and to normal human lymphocytes. These cells did not show binding of GT to the specific nuclear proteins, and they were not sensitive to the cytotoxic action of the GT sequence. Drug potentiation by GT not involving normal human lymphocytes might be exploited to develop a more selective treatment of drug-sensitive and MDR tumors.

Neoadjuvant androgen withdrawal prior to external radiotherapy for locally advanced adenocarcinoma of the prostate

BACKGROUND

It is unclear whether positive interactions between radiation and androgen withdrawal for patients with locally advanced prostate cancer is synergistic or additive. The present study aimed to clarify the significance of neoadjuvant androgen ablation prior to external radiotherapy in a human prostate LNCaP tumor model and in patients with locally advanced prostate cancer.

METHODS

Comparisons were made between the effect of castration prior to radiation on the growth of subcutaneous LNCaP tumors implanted into male nude mice and their serum prostate-specific antigen (PSA) levels, and the results of castration or radiation alone. Twenty-nine patients with histologically proven and locally advanced adenocarcinoma of the prostate were treated with luteinizing hormone-releasing hormone analog at least 3 months before, during, and after external radiation therapy with a total dose of 70 Gy. The toxicity and response to this therapy were evaluated.

RESULTS

Treatment combining castration and radiation resulted in synergistic inhibition of LNCaP tumor growth and a significant delay in the emergence of androgen-independent recurrence as opposed to either treatment alone. The external radiotherapy was completed in 28 patients (96.6%), resulting in a reduction of serum PSA levels in all 28 patients to below 1.0 ng/mL. All patients were alive after a mean follow-up period of 34 months (range 11-53) with a 3-year PSA relapse-free survival rate of 83.7%. Among several factors examined, only the Gleason score was significantly associated with PSA relapse-free survival in univariate analysis, but not in multivariate analysis. Thirteen of 28 patients (46%) and 7 of 28 (25%) also showed at least one form of gastrointestinal or genitourinary toxicity, respectively. Of these patients, 8 with gastrointestinal toxicities, and 1 with genitourinary toxicity, experienced acute complications higher than grade 3.

CONCLUSION

The experimental findings objectively suggested the use of neoadjuvant androgen withdrawal prior to radiation therapy. Although our clinical experience is preliminary, combined androgen ablation and radiation therapy may also be effective in controlling locally advanced prostate cancer, with tolerable side-effects.

10th International Conference on gene therapy of cancer: 13 - 15 December 2001, San Diego, CA, USA

This annual meeting was organised by R Sobol and A Deisseroth (Sidney Kimmel Cancer Center, San Diego, CA, USA) and K Scanlon (Keck Graduate Institute, Claremont, CA, USA). The meeting covered a wide range of topics in cancer gene therapy and included five sessions. The topics were: (1) Tumour suppressors/apoptosis/antisense-ribozymes/angiogenesis; (2) Vector systems; (3) Therapy sensitisation/'suicide' gene therapy; (4) Haematopoietic gene transfer; and (5) Poster/discussion sessions. The following meeting highlights have focused mainly on the recent progress in antisense/ribozyme-based approaches useful for cancer gene target validation and drug development.

Clusterin expression is significantly enhanced in prostate cancer cells following androgen withdrawal therapy

INTRODUCTION AND OBJECTIVES

Progression of prostate cancer to androgen independence (AI) results in part from the upregulation of anti-apoptotic genes following androgen withdrawal, and androgen-independent disease remains the primary obstacle to improved survival. Testosterone-repressed prostate message-2 (TRPM-2) encodes the anti-apoptotic protein clusterin, which is upregulated in response to cellular compromise as observed in normal and malignant tissues undergoing apoptosis. Systemic administration of antisense clusterin oligonucleotides in prostate cancer xenograft models delays progression to AI and enhances chemosensitivity. The objective of this study was to define changes in clusterin expression following neoadjuvant hormone therapy (NHT) in prostate cancer patients.

MATERIALS AND METHODS

Archival radical prostatectomy (RP) specimens were obtained for 128 patients who received either no NHT or treatment for 2-8 weeks, 3 months, or 8 months. Paired needle biopsy specimens were acquired for 30 patients and all tissues were subjected to clusterin immunohistochemistry. Western blot analysis was performed on frozen tissue from 5 untreated and 5 treated patients.

RESULTS

Clusterin expression in malignant prostatic tissue was significantly greater in patients who underwent preoperative NHT (P < 0.001). Needle biopsies obtained prior to NHT consistently demonstrated lower staining intensity than corresponding RP specimens (P < 0.001). Western blot analysis confirmed clusterin levels increased 17-fold beginning within 4 weeks after androgen withdrawal.

CONCLUSIONS

Upregulation of clusterin levels following androgen ablation therapy may represent an adaptive cell survival response following apoptotic signals like androgen withdrawal. These findings support clusterin as a valid therapeutic target in strategies employing novel multimodality therapy for advanced prostate cancer.

Over expression of clusterin is an independent prognostic factor for nonpapillary renal cell carcinoma

PURPOSE

Recent studies have revealed the powerful anti-apoptotic activity of clusterin in several types of malignant tumors. However, the significance of clusterin expression in human renal cell carcinoma has not been well characterized. We determined whether the expression level of clusterin in nonpapillary renal cell carcinoma may be used as predictor of tumor progression and prognosis.

MATERIALS AND METHODS

Total RNA was extracted from 93 nonpapillary renal cell carcinomas obtained at surgery and expression levels of clusterin messenger (m)RNA in these specimens were measured by Northern blot analysis. Findings were analyzed with respect to several clinicopathological factors.

RESULTS

There were 48 cases (52%) with strong clusterin mRNA expression and 45 (48%) in which it was weak or nonexistent. The expression level of clusterin mRNA did not significantly correlate with patient gender, age, tumor grade or size, or histological cell type, whereas pathological stage and the incidence of tumor recurrence were closely associated with clusterin expression (p <0.005 and <0.01, respectively). The recurrence-free and overall survival rates in patients with strong clusterin expression were significantly lower than in those with weak or no expression (p <0.05). Furthermore, multivariate analyses revealed that strong expression of clusterin was an independent predictor of tumor recurrence and overall survival (p <0.05).

CONCLUSIONS

These findings suggest that the over expression of clusterin may be a useful prognostic parameter in patients with nonpapillary renal cell carcinoma after radical nephrectomy.

Antisense-induced down-regulation of thymidylate synthase and enhanced cytotoxicity of 5-FUdR in 5-FUdR-resistant HeLa cells

1. Thymidylate synthase (TS) is a target for several anticancer drugs. We previously showed that an antisense oligodeoxynucleotide (ODN) directed against TS mRNA down-regulated TS protein and enhanced cytotoxicity of TS-targeting drugs [including 5-fluorodeoxyuridine (5-FUdR)] in HeLa cells. Patient tumours with increased TS expression are resistant to TS-targeting drugs. It was hypothesized that TS mRNA and consequently TS protein could be down-regulated in 5-FUdR-resistant cells that overexpress TS, sensitizing them to 5-FUdR cytotoxicity. In this study we assessed the capacity of an anti-TS antisense ODN to circumvent resistance dependent on TS overexpression. 2. Variant HeLa clones exhibiting 2 - 20 fold resistance to 5-FUdR were selected by exposing cultured cells to drug. Clones FUdR-5a, -25b, and -50a expressed TS protein levels 10 fold, 10 fold, and 17 fold higher (respectively) than parental cells. Cells were treated with antisense ODN 83 (a 2'-methoxy-ethoxylated, phosphorothioated 20-mer, complementary to a portion of the 3'-untranslated region of TS mRNA), or ODN 32 (a control ODN with the same base composition as ODN 83, but in randomized order). Twenty-four and 48 h following transfection (50-100 nM ODN, plus polycationic liposome), TS mRNA levels (by RT-PCR) and protein levels (by radiolabelled 5-FUdR-monophosphate binding) were decreased by at least 60% in ODN 83-treated cells compared with control ODN 32-treated cells. ODN 83 enhanced the cytotoxicity of 5-FUdR by up to 85% in both parental and 5-FUdR-resistant cell lines. 3. Antisense ODN can be used to down-regulate TS and attenuate drug resistance in TS-overexpressing cells.

Inhibition of potentially anti-apoptotic proteins by antisense protein kinase C-alpha (Isis 3521) and antisense bcl-2 (G3139) phosphorothioate oligodeoxynucleotides: relationship to the decreased viability of T24 bladder and PC3 prostate cancer cells

Isis 3521 and G3139 are 20- and 18-mer phosphorothioate oligonucleotides, respectively, targeted to the protein kinase C (PKC)-alpha and bcl-2 mRNAs. Treatment of T24 bladder and PC3 prostate carcinoma cells with full-length and 3'-truncation mutants of Isis 3521 causes down-regulation of PKC-alpha protein and mRNA. However, at the level of a 15-mer and shorter, down-regulation of mRNA expression is no longer observed. Further, no diminution in cellular viability, as measured by 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide assay, in response to increasing concentrations of paclitaxel, can be observed for these shorter oligomers. These observations not only indicate that PKC-alpha protein expression can be down-regulated by both RNase H-dependent and -independent mechanisms but also that down-regulation of PKC-alpha is insufficient by itself to "chemosensitize" cells. G3139, which down-regulates bcl-2 protein and mRNA expression, also down-regulates PKC-alpha protein and mRNA expression but not that of PKC-betaI, -epsilon, or -zeta. However, the down-regulation of PKC-alpha and bcl-2 are not linked. When the carrier Eufectin 5 is employed, only bcl-2 is down-regulated in both T24 and PC3 cells at 50 nM oligonucleotide concentration. At 100 nM, both bcl-2 and PKC-alpha expression are down-regulated, and only at this concentration can "chemosensitization" to paclitaxel and carboplatin be observed. In contrast, the down-regulation of bcl-2 seems to be linked with that of RelA (p65). However, this too is also not sufficient for chemosensitization, even though it leads to the loss of expression of genes under the putative control of nuclear factor-kappaB and to detachment of the cells from plastic surfaces. These results underscore the complexity of the intracellular requirements for the initiation of chemosensitization to anti-neoplastic agents.