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

Therapeutic Potential of Clusterin Inhibition in Human Cancer

Clusterin (CLU) protein is involved in various pathophysiological processes including carcinogenesis and tumor progression. In recent years, the role of the secretory isoform has been demonstrated in tumor cells, where it inhibits apoptosis and favors the acquisition of resistance to conventional treatments used to treat cancer. To determine the possible therapeutic potential of inhibiting this protein, numerous studies have been carried out in this field. In this article, we present the existing knowledge to date on the inhibition of this protein in different types of cancer and analyze the importance it could have in the development of new therapies targeted against this disease.

Clusterin Expression in Colorectal Carcinomas

Colorectal cancer is the third most diagnosed cancer, behind only breast and lung cancer. In terms of overall mortality, it ranks second due to, among other factors, problems with screening programs, which means that one of the factors that directly impacts survival and treatment success is early detection of the disease. Clusterin (CLU) is a molecular chaperone that has been linked to tumorigenesis, cancer progression and resistance to anticancer treatments, which has made it a promising drug target. However, it is still necessary to continue this line of research and to adjust the situations in which its use is more favorable. The aim of this paper is to review the current genetic knowledge on the role of CLU in tumorigenesis and cancer progression in general, and discuss its possible use as a therapeutic target in colorectal cancer.

Clusterin and Its Isoforms in Oral Squamous Cell Carcinoma and Their Potential as Biomarkers: A Comprehensive Review

Oral squamous cell carcinoma (OSCC) is a prevalent type of head and neck cancer, ranked as the sixth most common cancer worldwide, accounting for approximately 300,000 new cases and 145,000 deaths annually. Early detection using biomarkers significantly increases the 5-year survival rate of OSCC by up to 80-90%. Clusterin (CLU), also known as apolipoprotein J, is a sulfated chaperonic glycoprotein expressed in all tissues and human fluids and has been reported to be a potential biomarker of OSCC. CLU has been implicated as playing a vital role in many biological processes such as apoptosis, cell cycle, etc. Abnormal CLU expression has been linked with the development and progression of cancers. Despite the fact that there are many studies that have reported the involvement of CLU and its isoforms in OSCC, the exact roles of CLU and its isoforms in OSCC carcinogenesis have not been fully explored. This article aims to provide a comprehensive review of the current understanding of CLU structure and genetics and its correlation with OSCC tumorigenesis to better understand potential diagnostic and prognostic biomarker development. The relationship between CLU and chemotherapy resistance in cancer will also be discussed to explore the therapeutic application of CLU and its isoforms in OSCC.

Circadian rhythmicity of amyloid-beta-related molecules is disrupted in the choroid plexus of a female Alzheimer's disease mouse model

The choroid plexus (CP) is part of the blood-cerebrospinal fluid barrier (BCSFB) and was recently described as an important component of the circadian clock system. It is the principal source of cerebrospinal fluid (CSF) and responsible for the synthesis and secretion of various neuroprotective peptides including those involved in amyloid-β (Aβ) transport/degradation, contributing to Aβ homeostasis. Inadequate Aβ metabolic clearance and transport across the BCSFB have been associated with circadian dysfunctions in Alzheimer's disease (AD) patients. To investigate whether AD pathology influences Aβ scavengers circadian expression, we collected CP at different time points from an AD mouse model (APP/PS1) (female and male animals, aged 6- and 12-months-old) and analyzed their mRNA expression by Real-time RT-PCR. Only angiotensin-converting enzyme (Ace) expression in 6-month-old female wild-type mice and transthyretin (Ttr) expression in 12-month-old female wild-type mice presented significant rhythmicity. The circadian rhythmicity of Ace and Ttr, prompt us to analyze the involvement of circadian rhythm in Aβ uptake. A human CP papilloma (HIBCPP) cell line was incubated with Aβ-488 and uptake was evaluated at different time points using flow cytometry. Aβ uptake displayed circadian rhythmicity. Our results suggest that AD might affect Aβ scavengers rhythmicity and that Aβ clearance is a rhythmic process possibly regulated by the rhythmic expression of Aβ scavengers.

Targeting Clusterin Induces Apoptosis, Reduces Growth Ability and Invasion and Mediates Sensitivity to Chemotherapy in Human Osteosarcoma Cells

Objective:

The aim of the study was to investigate the expression of sCLU in relation to the clinicopathological features and prognosis of patients with untreated High-Grade Osteosarcoma (HGOS) and to evaluate sCLU as a target for osteosarcoma (OS) therapies.

Methods:

The expression of sCLU in 98 patients of HGOS enrolled from April 2005 to March 2015 at the affiliated hospital of Qingdao University was evaluated by immunohistochemistry. The sCLU expression, clinical data and survival were compared. siRNA-mediated sCLU gene silencing on cell apoptosis, viability, invasion and chemosensitivity to doxorubicin in U2OS cells in vitro was evaluated.

Results:

sCLU expression was found in 59 (60%) of the 98 patients. A positive correlation was observed between sCLU expression and metastatic disease (P = 0.036) and a negative correlation between sCLU expression and response to chemotherapy (P = 0.002). Targeting sCLU expression in U2OS cells induced significant reduction in cellular growth and higher rates of spontaneous endogenous apoptosis. In addition, targeting sCLU expression inhibited the invasion of U2OS cells. Furthermore, targeting sCLU expression significantly sensitized to chemotherapeutic drug, doxorubicin.

Conclusions:

The overexpression of sCLU was significantly correlated with metastasis and chemosensitivity in patients with HGOS. sCLU may be a promising therapeutic or chemopreventive target for human OS treatment.

Clusterin inhibition mediates sensitivity to chemotherapy and radiotherapy in human cancer

Since its discovery in 1983, the protein clusterin (CLU) has been isolated from almost all human tissues and fluids and linked to the development of different physiopathological processes, including carcinogenesis and tumor progression. During the last few years, several studies have shown the cytoprotective role of secretory CLU in tumor cells, inhibiting their apoptosis and enhancing their resistance to conventional treatments including hormone depletion, chemotherapy, and radiotherapy. In an effort to determine the therapeutic potential that the inhibition of this protein could have on the development of new strategies for cancer treatment, numerous studies have been carried out in this field, with results, in most cases, satisfactory but sometimes contradictory. In this document, we summarize for the first time the current knowledge of the effects that CLU inhibition has on sensitizing tumor cells to conventional cancer treatments and discuss its importance in the development of new strategies against cancer.

Custirsen (OGX-011) combined with cabazitaxel and prednisone versus cabazitaxel and prednisone alone in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel (AFFINITY): a randomised, open-label, international, phase 3 trial

BACKGROUND

Docetaxel and cabazitaxel improve overall survival compared with mitoxantrone in patients with metastatic castration-resistant prostate cancer. Custirsen (OGX011) is a second generation highly specific antisense oligonucleotide that inhibits the production of clusterin, an antiapoptotic protein that is upregulated in response to chemotherapy and that confers treatment resistance. We aimed to assess whether custirsen in combination with cabazitaxel and prednisone increases overall survival in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel.

METHODS

In this randomised, open-label, international, phase 3 trial, men with radiographically documented metastatic castration-resistant prostate cancer that had progressed after docetaxel treatment with a Karnofsky performance status of more than 70% and who were fit for chemotherapy, were recruited from 95 cancer treatment centres in eight countries. Patients were randomly assigned (1:1) centrally using permuted blocks (block size 8) to receive cabazitaxel plus prednisone (cabazitaxel 25 mg/m² intravenously every 21 days plus oral prednisone 10 mg daily) with or without custirsen (640 mg intravenously on days 1, 8, and 15, plus three previous loading doses) until disease progression, unacceptable toxicity, or the completion of ten treatment cycles. Randomisation was stratified by use of opioids for prostate cancer-related pain at screening, disease progression following first-line docetaxel treatment established by radiographic evidence, and previous treatment with abiraterone or enzalutamide. The co-primary endpoints were overall survival in all randomly assigned patients and in a poor-prognosis subgroup. All analyses were intention to treat with the exception of safety, which was reported for patients who received any assigned treatment. The trial has been completed and the results presented here are the final analysis. This trial is registered with Clinicaltrials.gov, number NCT01578655.

FINDINGS

Between Sept 9, 2012, and Sept 29, 2014, 795 patients were screened for enrolment. 635 men were eligible for inclusion and were randomly assigned (n=317 in the cabazitaxel and prednisone plus custirsen group and n=318 in the cabazitaxel and prednisone group). Median follow up was 28·3 months (IQR 24·4-34·5) for the custirsen group and 29·8 months (IQR 25·3-35·2) for the control group. Median overall survival in all randomly assigned patients did not differ between the two groups (14·1 months [95% CI 12·7-15·9] in the curtisen group vs 13·4 months [12·1-14·9] in the control group; hazard ratio [HR] 0·95 [95% CI 0·80-1·12]; log-rank p=0·53). In the poor prognosis subgroup, median overall survival also did not differ between the two treatment groups (11·0 months [95% CI 9·3-13·3] in the custursin group vs 10·9 months [8·2-12·4] in the control group; HR 0·97 [95% CI 0·80-1·21]; two-sided p=0·80). The most frequently reported grade 3 or worse adverse events in the custirsen versus control groups were neutropenia (70 [22%] of 315 vs 61 [20%] of 312), anaemia (68 [22%] vs 49 [16%]), fatigue (23 [7%] vs 18 [6%]), asthenia (16 [5%] vs 8 [3%]), bone pain (16 [5%] vs 5 [2%]), and febrile neutropenia (16 [5%] vs 9 [3%]). Serious adverse events were reported in 155 (49%) versus 132 (42%). 27 patients died within 30 days of treatment in the cabazitaxel and prednisone plus custirsen group, seven of which were deemed to be treatment related, versus 17 in the cabazitaxel and prednisone group, eight of which were deemed to be treatment related. Of the 21 deaths reported, 15 were reported as complications related to study treatment, either chemotherapy (eight and three, respectively) or study drug (none and four, respectively).

INTERPRETATION

We noted no survival benefit in men with metastatic castration-resistant prostate cancer with the addition of custirsen to cabazitaxel and prednisone treatment. Cabazitaxel and prednisone remains the standard of care for patients with metastatic castration-resistant prostate cancer progressing after docetaxel chemotherapy.

FUNDING

OncoGenex Pharmaceuticals.

Clusterin and neuropilin-2 as potential biomarkers of tumor progression in benzo[a]pyrene-transformed 16HBE cells xenografted nude mouse model

Benzo[a]pyrene (BaP) is a ubiquitous environment contaminant and its exposure could increase incidence of human lung cancer. In order to confirm and compare potential biomarkers of BaP-induce carcinogenesis and tumor progression, time-dependent changes of clusterin (CLU) and neuropilin-2 (NRP2) levels were evaluated in sera of BaP-transformed 16HBE cell line T-16HBE-C1 cells xenografted nude mice. Performance of CLU and NRP2 on tissue classification and tumor progression forecast was also calculated. Levels of CLU and NRP2 were significant elevated in both culture supernatant of T-16HBE-C1 cells and sera of T-16HBE-C1 cells xenografted nude mice compared with control. CLU and NRP2 were both found positively stained in tumor tissue. CLU and NRP2 alone could well predicate tumor progression in nude mice and CLU appeared to be more sensitive than NRP2. When both of them combined, performance of predication would improve. In conclusion, CLU and NRP2 could serve as potential biomarkers of tumor progression in nude mice xenografted with T-16HBE-C1 cells.

Autocrine mechanisms of cancer chemoresistance

An ever-increasing number of studies highlight the role of cancer secretome in the modification of tumour microenvironment and in the acquisition of cancer cell resistance to therapeutic drugs. The knowledge of the mechanisms underlying the relationship between cancer cell-secreted factors and chemoresistance is becoming fundamental for the identification of novel anticancer therapeutic strategies overcoming drug resistance and novel prognostic secreted biomarkers. In this review, we summarize the novel findings concerning the regulation of secreted molecules by cancer cells compromising drug sensitivity. In particular, we highlight data from available literature describing the involvement of cancer cell-secreted molecules determining chemoresistance in an autocrine manner, including: i) growth factors; ii) glycoproteins; iii) inflammatory cytokines; iv) enzymes and chaperones; and v) tumor-derived exosomes.

Melittin inhibits tumor growth and decreases resistance to gemcitabine by downregulating cholesterol pathway gene CLU in pancreatic ductal adenocarcinoma

Melittin is a Chinese traditional medicine for treating chronic inflammation, immunological diseases and cancers, however, the efficacy of melittin and its mechanism for treating pancreatic ductal adenocarcinoma (PDAC) are still unknown. Here we investigated the anti-cancer activity of melittin and its regulated mechanism(s) in the PDAC models. Melittin was found to suppress tumor growth by promoting cell apoptosis and cell-cycle arrest. Interestingly, the microarray analyses demonstrated that melittin significantly regulated cholesterol biosynthesis pathway during treatment. For instance, the cholesterol pathway gene clusterin (CLU) was highly downregulated by melittin which also enhanced gemcitabine sensitivity in PDAC cells by inhibiting CLU expression. In contrast, overexpression of CLU significantly diminished melittin mediated tumor suppression and gemcitabine sensitization, suggesting that CLU is the target of melittin. Furthermore, in the xenograft mouse model, the combination therapy of melittin and gemcitabine is more efficacious for inhibiting PDAC tumor growth than either single regimen. Taken together, our study has indicated that melittin is capable of suppressing tumor growth and promoting gemcitabine sensitivity in PDAC by downregulating cholesterol pathway.

Custirsen in combination with docetaxel and prednisone for patients with metastatic castration-resistant prostate cancer (SYNERGY trial): a phase 3, multicentre, open-label, randomised trial

BACKGROUND

Clusterin is a chaperone protein associated with treatment resistance and upregulated by apoptotic stressors such as chemotherapy. Custirsen is a second-generation antisense oligonucleotide that inhibits clusterin production. The aim of the SYNERGY trial was to investigate the effect of custirsen in combination with docetaxel and prednisone on overall survival in patients with metastatic castration-resistant prostate cancer.

METHODS

SYNERGY was a phase 3, multicentre, open-label, randomised trial set at 134 study centres in 12 countries. Patients were eligible for participation if they had: metastatic castration-resistant prostate cancer and had received no previous chemotherapy; prostate-specific antigen greater than 5 ng/mL; and a Karnofsky performance score of 70% or higher. Patients were randomly assigned 1:1 centrally to either the docetaxel, prednisone, and custirsen combination or docetaxel and prednisone alone. Patients were not masked to treatment allocation. Randomisation was stratified by opioid use for cancer-related pain and radiographic evidence of progression. All patients received docetaxel 75 mg/m² intravenously with 5 mg of prednisone orally twice daily. Patients assigned docetaxel, prednisone, and custirsen received weekly doses of custirsen 640 mg intravenously after three loading doses of 640 mg. The primary endpoint was overall survival analysed in the intention-to-treat population. Patients who received at least one study dose were included in the safety analysis set. This trial is registered with ClinicalTrials.gov, number NCT01188187. The trial is completed and final analyses are reported here.

FINDINGS

Between Dec 10, 2010, and Nov 7, 2012, 1022 patients were enrolled to the trial, of whom 510 were assigned docetaxel, prednisone, and custirsen and 512 were allocated docetaxel and prednisone. No difference in overall survival was recorded between the two groups (median survival 23·4 months [95% CI 20·9-24·8] with docetaxel, prednisone, and custirsen vs 22·0 months [19·5-24·0] with docetaxel and prednisone; hazard ratio [HR] 0·93, 95% CI 0·79-1·10; p=0·415). The most common adverse events of grade 3 or worse in the docetaxel, prednisone and custirsen group (n=501) compared with the docetaxel and prednisone alone group (n=499) were neutropenia (grade 3, 63 [13%] vs 28 [6%]; grade 4, 98 [20%] vs 77 [15%]), febrile neutropenia (grade 3, 52 [10%] vs 31 [6%]; grade 4, four [1%] vs two [<1%]), and fatigue (grade 3, 53 [11%] vs 41 [8%]; grade 4, three [1%] vs one [<1%]). One or more serious adverse events were reported for 214 (43%) of 501 patients treated with docetaxel, prednisone, and custirsen and 181 (36%) of 499 receiving docetaxel and prednisone alone. Adverse events were attributable to 23 (5%) deaths in the docetaxel, prednisone, and custirsen group and 24 (5%) deaths in the docetaxel and prednisone alone group.

INTERPRETATION

Addition of custirsen to first-line docetaxel and prednisone was reasonably well tolerated, but overall survival was not significantly longer for patients with metastatic castration-resistant prostate cancer treated with this combination, compared with patients treated with docetaxel and prednisone alone.

FUNDING

OncoGenex Technologies.

Randomized phase II trial of Custirsen (OGX-011) in combination with docetaxel or mitoxantrone as second-line therapy in patients with metastatic castrate-resistant prostate cancer progressing after first-line docetaxel: CUOG trial P-06c

PURPOSE

Clusterin (CLU) is an antiapoptotic, stress-induced protein conferring treatment resistance when overexpressed. This study tested custirsen, a CLU inhibitor, in patients with metastatic castration-resistant prostate cancer (mCRPC) progressing during or within 6 months of initial docetaxel therapy.

PATIENTS AND METHODS

Men were randomized to receive either docetaxel + prednisone + custirsen (DPC) or mitoxantrone + prednisone + custirsen (MPC).

RESULTS

Forty-two patients received study treatment. Toxicity was similar in both arms. Twenty patients treated with DPC received a median of 8 cycles; overall survival (OS) was 15.8 months. Median time to pain progression (TTPP) was 10.0 months; 10 of 13 (77%) evaluable patients had pain responses. Three of 13 (23%) evaluable patients had objective partial responses. Prostate-specific antigen (PSA) declines of 90% or more, 50% or more, and 30% or more occurred in 4 (20%), 8 (40%), and 11 (55%) patients, respectively. Twenty-two patients treated with MPC received a median of 6 cycles; OS was 11.5 months. The median TTPP was 5.2 months; 6 of 13 (46%) evaluable patients had pain responses. No objective responses were observed. PSA declines of 50% or more and 30% or more occurred in 6 (27%) and 7 (32%) patients, respectively. Low serum CLU levels during treatment showed superior survival for patients based on modeling with proportional hazard regression with a time-dependent covariate and different landmarks.

CONCLUSIONS

Custirsen plus either docetaxel or mitoxantrone was feasible in patients with progressive mCRPC following first-line docetaxel therapy. Pain relief was higher than expected, with interesting correlations between serum CLU and survival. A phase III trial evaluating the pain palliation benefit of custirsen with taxane therapy is ongoing.

A phase I study of OGX-011, a 2'-methoxyethyl phosphorothioate antisense to clusterin, in combination with docetaxel in patients with advanced cancer

PURPOSE

Clusterin is a cytoprotective chaperone protein that promotes cell survival and confers broad-spectrum treatment resistance. OGX-011 is a 2'-methoxyethyl-modified phosphorothioate antisense oligonucleotide that is complementary to clusterin mRNA, has a prolonged tissue half life, enhances drug efficacy in xenograft models, and reduces clusterin expression in humans with a biologically effective dose of 640 mg. The objective of this study was to determine a recommended phase II dose of OGX-011 in combination with docetaxel.

EXPERIMENTAL DESIGN

Patients with cancers known from the literature to express clusterin were eligible. OGX-011 was given by 2-h i.v. infusion starting at 40 mg weekly after loading doses on days 1, 3, and 5. Docetaxel was given i.v. 30 mg/m(2) weekly for 5 of 6 weeks (schedule A) or 75 mg/m(2) every 3 weeks (schedule B). All patients had serial samples of peripheral blood mononuclear cells and serum assessed for clusterin expression.

RESULTS

Forty patients were enrolled to eight cohorts. OGX-011 could be given at the full biologically effective single-agent dose of 640 mg with both docetaxel schedules. Toxic effects were primarily myelosuppression, fatigue, hair loss, gastrointestinal effects (expected docetaxel effects), as well as dose-related chills and fever (expected OGX-011 effects). OGX-011 AUC and C(max) increased proportionally with no apparent effect on docetaxel pharmacokinetics. At the end of cycle 1, serum clusterin showed mean decreases of 34% and 38% (range, 15-99%) at the 640-mg dose levels.

CONCLUSIONS

OGX-011 can be given at a biologically effective dose with standard doses of docetaxel. Phase II trials of combined OGX-011 and chemotherapy are ongoing in patients with prostate, breast, and lung cancers.

Cytoplasmic clusterin expression is associated with longer survival in patients with resected non small cell lung cancer

BACKGROUND

Clusterin is a glycoprotein that has been implicated in many processes, including apoptosis, cell cycle regulation, and DNA repair. Previous studies have examined the prognostic value of clusterin expression in various malignancies. In the present study, we examined clusterin staining in tumors resected from patients with non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Tumor specimens were obtained for 113 patients with completely resected NSCLC from paraffin-embedded tissue microarrays and stained with an antibody specific for clusterin. Staining patterns were observed and graded based on intensity and then correlated with clinical data.

RESULTS

Positive cytoplasmic clusterin staining was observed in 44 patients, and weak/negative staining was observed in 62 patients. Patients who had tumors that stained positive for cytoplasmic clusterin had significantly longer survival in multivariate analysis (hazard ratio 0.487, 95% confidence interval 0.27-0.89). A correlation was also observed for recurrence-free survival, which approached statistical significance (hazard ratio 0.345, 95% confidence interval 0.12-1.02). In univariate analysis, patients with clusterin-positive tumors had a 63% 3-year survival, whereas patients with clusterin-negative tumors had a 42% 3-year survival (P = 0.0108); clusterin-positive tumors also had significantly less recurrence (P = 0.0231).

CONCLUSIONS

Cytoplasmic clusterin staining is present in a substantial number of NSCLC tumors and may be a biomarker for longer survival in patients with surgically resected NSCLC.

Clusterin isoforms differentially affect growth and motility of prostate cells: possible implications in prostate tumorigenesis

Besides a fully processed, secreted form of clusterin (sCLU), an alternative proapoptotic form of the protein targeting the nucleus (nCLU) was recently described. The possible differential roles played by the two clusterin forms in growth and motility of nonmalignant and malignant prostate cells are investigated here. sCLU or nCLU was transiently transfected in both androgen-independent prostate cancer cells (PC3 and DU 145) and immortalized prostate epithelial cells (PNT1A, a nontumoral control). Then, cell growth, motility, and cytoskeleton organization were studied. We found that (a) in PNT1A cells, both sCLU and nCLU significantly decreased cell proliferation and motility; (b) in PC3 and DU 145 cancer cells, only nCLU inhibited cell growth and migration, with sCLU being ineffective; and (c) the antimotility effect of nCLU was accompanied by a dramatic dismantling of the actin cytoskeleton. Moreover, transfection with "full-length" CLU cDNA produced both sCLU and nCLU in nonmalignant PNT1A cells, whereas only sCLU was found in cancer cells. Thus, CLU gene expression might play a crucial role in prostate tumorigenesis by exerting differential biological effects on normal versus tumor cells through differential processing of CLU isoforms in the two cell systems. We also found that nCLU binds to alpha-actinin, a key protein for the regulation of actin cytoskeleton, and that nCLU and alpha-actinin colocalize in the cytoplasm. Thus, the antimotility activity of nCLU and its ability to cause dismantling of the actin cytoskeleton seem to be mediated by its binding to alpha-actinin.

Hsp27 knockdown using nucleotide-based therapies inhibit tumor growth and enhance chemotherapy in human bladder cancer cells

Heat shock protein 27 (Hsp27) is a cytoprotective chaperone that is phosphoactivated during cell stress that prevents aggregation and/or regulate activity and degradation of certain client proteins. Recent evidence suggests that Hsp27 may be involved in tumor progression and the development of treatment resistance in various tumors, including bladder cancer. The purpose of this study was to examine, both in vitro and in vivo, the effects of overexpression of Hsp27 and, correspondingly, the down-regulation of Hsp27 using small interfering (si) RNA and OGX-427, a second-generation antisense oligonucleotide targeting Hsp27. Hsp27 overexpression increased UMUC-3 cell growth and resistance to paclitaxel. Both OGX-427 and Hsp27 siRNA decreased Hsp27 protein and mRNA levels by >90% in a dose- and sequence-specific manner in human bladder cancer UMUC-3 cells. OGX-427 or Hsp27 siRNA treatment induced apoptosis and enhanced sensitivity to paclitaxel in UMUC-3 cells. In vivo, OGX-427 significantly inhibited tumor growth in mice, enhanced sensitivity to paclitaxel, and induced significantly higher levels of apoptosis compared with xenografts treated with control oligonucleotides. Collectively, these findings suggest that Hsp27 knockdown with OGX-427 and combined therapy with paclitaxel could be a novel strategy to inhibit the progression of bladder cancer.

Knockdown of the cytoprotective chaperone, clusterin, chemosensitizes human breast cancer cells both in vitro and in vivo

Clusterin is a stress-associated cytoprotective chaperone up-regulated by various apoptotic triggers in many cancers and confers treatment resistance when overexpressed. The objectives of this study were to evaluate clusterin expression levels in human breast cancer and to determine whether antisense oligonucleotides or double-stranded small interfering RNAs (siRNA) targeting the clusterin gene enhance apoptosis induced by paclitaxel. Clusterin immunostaining was evaluated in a tissue microarray of 379 spotted breast cancers. The effect of hormone withdrawal, paclitaxel treatment, clusterin antisense oligonucleotide (OGX-011), and siRNA treatments on clusterin expression was examined in MCF-7 and MDA-MB-231 cells. Northern, quantitative real-time PCR, and Western analyses were used to measure change in clusterin mRNA and protein levels. The effect of OGX-011 or siRNA clusterin treatment on chemosensitivity to paclitaxel was done in both cell lines in vitro, whereas the ability of OGX-011 to chemosensitize in vivo was evaluated in athymic mice bearing MCF-7 tumors. Clusterin was expressed in 62.5% of tumors within the tissue microarray. Clusterin expression increased after estrogen withdrawal and paclitaxel treatment in vitro in MCF-7 cells. OGX-011 or siRNA clusterin decreased clusterin levels by >90% in a dose-dependent, sequence-specific manner and significantly enhanced chemosensitivity to paclitaxel in vitro. When combined, OGX-011 or siRNA clusterin reduced the IC50 by 2-log compared with paclitaxel alone. In vivo administration of OGX-011 enhanced the effects of paclitaxel to significantly delay MCF-7 tumor growth. These data identify clusterin as a valid therapeutic target and provides preclinical proof-of-principle to test OGX-011 in multimodality therapies for breast cancer.