Sialylation: A Cloak for Tumors to Trick the Immune System in the Microenvironment

The tumor microenvironment (TME), where the tumor cells incite the surrounding normal cells to create an immune suppressive environment, reduces the effectiveness of immune responses during cancer development. Sialylation, a type of glycosylation that occurs on cell surface proteins, lipids, and glycoRNAs, is known to accumulate in tumors and acts as a "cloak" to help tumor cells evade immunological surveillance. In the last few years, the role of sialylation in tumor proliferation and metastasis has become increasingly evident. With the advent of single-cell and spatial sequencing technologies, more research is being conducted to understand the effects of sialylation on immunity regulation. This review provides updated insights into recent research on the function of sialylation in tumor biology and summarizes the latest developments in sialylation-targeted tumor therapeutics, including antibody-mediated and metabolic-based sialylation inhibition, as well as interference with sialic acid-Siglec interaction.

Expression of a Siglec-Fc Protein and Its Characterization

The emerging importance of the Siglec-sialic acid axis in human disease, especially cancer, has necessitated the identification of ligands for Siglecs. Recombinant Siglec-Fc fusion proteins have been widely used as ligand detectors, and also as sialic acid-targeted antibody-like proteins for cancer treatment. However, the heterogenetic properties of the Siglec-Fc fusion proteins prepared from various expression systems have not been fully elucidated. In this study, we selected HEK293 and CHO cells for producing Siglec9-Fc and further evaluated the properties of the products. The protein yield in CHO (8.23 mg/L) was slightly higher than that in HEK293 (7.46 mg/L). The Siglec9-Fc possesses five N-glycosylation sites and one of them is located in its Fc domain, which is important for the quality control of protein production and also the immunogenicity of Siglec-Fc. Our glycol-analysis confirmed that the recombinant protein from HEK293 received more fucosylation, while CHO showed more sialylation. Both products revealed a high dimerization ratio and sialic acid binding activity, which was confirmed by the staining of cancer cell lines and bladder cancer tissue. Finally, our Siglec9-Fc product was used to analyze the potential ligands on cancer cell lines.

Engineering Corynebacterium glutamicum for the de novo biosynthesis of tailored poly-γ-glutamic acid

γ-Polyglutamic acid (γ-PGA) is a biodegradable polymer naturally produced by Bacillus spp. that has wide applications. Fermentation of γ-PGA using Bacillus species often requires the supplementation of L-glutamic acid, which greatly increases the overall cost. Here, we report a metabolically engineered Corynebacterium glutamicum capable of producing γ-PGA from glucose. The genes encoding γ-PGA synthase complex from B. subtilis (pgsB, C, and A) or B. licheniformis (capB, C, and A) were expressed under inducible promoter P_tac in a L-glutamic acid producer C. glutamicum ATCC 13032, which led to low levels of γ-PGA production. Subsequently, C. glutamicum F343 with a strong L-glutamic acid production capability was tested. C. glutamicum F343 carrying capBCA produced γ-PGA up to 11.4 g/L, showing a higher titer compared with C. glutamicum F343 expressing pgsBCA. By introducing B. subtilis glutamate racemase gene racE under P_tac promoter mutants with different expression strength, the percentage of L-glutamic acid units in γ-PGA could be adjusted from 97.1% to 36.9%, and stayed constant during the fermentation process, while the γ-PGA titer reached 21.3 g/L under optimal initial glucose concentrations. The molecular weight (M_w) of γ-PGA in the engineered strains ranged from 2000 to 4000 kDa. This work provides a foundation for the development of sustainable and cost-effective de novo production of γ-PGA from glucose with customized ratios of L-glutamic acid in C. glutamicum.

A randomized phase II study of weekly paclitaxel with or without pelareorep in patients with metastatic breast cancer: final analysis of Canadian Cancer Trials Group IND.213

BACKGROUND

Pelareorep, a serotype 3 reovirus, has demonstrated preclinical and early clinical activity in breast cancer and synergistic cytotoxic activity with microtubule targeting agents. This multicentre, randomized, phase II trial was undertaken to evaluate the efficacy and safety of adding pelareorep to paclitaxel for patients with metastatic breast cancer (mBC).

METHODS

Following a safety run-in of 7 patients, 74 women with previously treated mBC were randomized either to paclitaxel 80 mg/m² intravenously on days 1, 8, and 15 every 4 weeks plus pelareorep 3 × 10¹⁰ TCID₅₀ intravenously on days 1, 2, 8, 9, 15, and 16 every 4 weeks (Arm A) or to paclitaxel alone (Arm B). Primary endpoint was progression-free survival (PFS). Secondary endpoints were objective response rate, overall survival (OS), circulating tumour cell counts, safety, and exploratory correlative analyses. All comparisons used a two-sided test at an alpha level of 20%. Survival analyses were adjusted for prior paclitaxel.

RESULTS

Final analysis was performed after a median follow-up of 29.5 months. Pelareorep was well tolerated. Patients in Arm A had more favourable baseline prognostic variables. Median adjusted PFS (Arm A vs B) was 3.78 mo vs 3.38 mo (HR 1.04, 80% CI 0.76-1.43, P = 0.87). There was no difference in response rate between arms (P = 0.87). Median OS (Arm A vs B) was 17.4 mo vs 10.4 mo (HR 0.65, 80% CI 0.46-0.91, P = 0.1).

CONCLUSIONS

This first, phase II, randomized study of pelareorep and paclitaxel in previously treated mBC did not show a difference in PFS (the primary endpoint) or RR. However, there was a significantly longer OS for the combination. Further exploration of this regimen in mBC may be of interest.

Temsirolimus in combination with carboplatin and paclitaxel in patients with advanced solid tumors: a NCIC-CTG, phase I, open-label dose-escalation study (IND 179)

BACKGROUND

The purpose of the study was to assess the safety, tolerability, recommended phase II dose (RPTD), and preliminary antitumor activity of the combination of carboplatin-paclitaxel (Taxol)-temsirolimus.

MATERIALS AND METHODS

Patients with solid malignancies suitable for carboplatin-paclitaxel (CP) chemotherapy and two or less prior lines of chemotherapy received 15, 20, or 25 mg of temsirolimus per week with CP given every 21 days. Thirty-eight eligible patients were entered into six dose levels with the first two levels administering temsirolimus on days 8 and 15 and the subsequent four dose levels switching to days 1 and 8 temsirolimus administration.

RESULTS

Days 8 and 15 administration of temsirolimus was not feasible due to myelosuppression on day 15. CP on day 1 with temsirolimus on days 1 and 8 was well tolerated. Dose-limiting toxicity (DLT) was grade 4 thrombocytopenia (n=2) and grade 3 fatigue (n=1). Relative dose intensities for carboplatin, paclitaxel, and temsirolimus at the RPTD were 92%, 82%, and 56%, respectively. Non-DLT treatment-related adverse events occurring in >20% of patients included fatigue, mucositis, alopecia, neuropathy, nausea, neutropenia, thrombocytopenia, and infection. Grade 3/4 non-hematological toxicity was rare. Partial responses (PRs) and disease stabilization were seen in 46% and 49% of patients, respectively. Nine of 11 (82%) endometrial cancer patients had objective PRs.

CONCLUSION

Carboplatin-paclitaxel-temsirolimus is well tolerated and the RPTD is carboplatin area under the curve 5 mg/ml/min, paclitaxel 175 mg/m2, both given on day 1 with temsirolimus 25 mg on days 1 and 8.

Preclinical and clinical activity of sunitinib in patients with cisplatin-refractory or multiply relapsed germ cell tumors: a Canadian Urologic Oncology Group/German Testicular Cancer Study Group cooperative study

BACKGROUND

The objective of the study was to investigate the activity of sunitinib in a cell line model and subsequently in patients with cisplatin-refractory or multiply relapsed germ cell tumors (GCT).

METHODS

The effect of sunitinib on cell proliferation in cisplatin-sensitive and cisplatin-refractory GCT cell lines was evaluated after 48-h sunitinib exposure by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, and IC(50) (concentration that causes 50% inhibition of growth) doses were determined. Sunitinib was subsequently administered at a dose of 50 mg/day for 4 weeks followed by a 2-week break to 33 patients using a Simon two-stage design.

RESULTS

Sunitinib demonstrated comparable dose-dependent growth inhibition in cisplatin-sensitive and cisplatin-resistant cell lines, with IC(50) between 3.0 and 3.8 μM. Patient characteristics were as follows: median of 2 (1-6) cisplatin-containing regimens; high-dose chemotherapy 67%; late relapse 33%; and cisplatin refractory or absolute cisplatin refractory 54%. Toxic effects included fatigue (39%), anorexia (21%), diarrhea (27%), mucositis (45%), nausea (33%), hand-foot syndrome (12%), dyspepsia (27%), and skin rash (18%). No unexpected side-effects were observed. Thirty -two of 33 patients were assessable for response. Three confirmed partial responses (PRs) and one unconfirmed PR were seen for a total response rate of 13%. Median progression-free survival (PFS) was 2 months, with a 6-month PFS rate of 11%.

CONCLUSIONS

Sunitinib shows in vitro activity in cisplatin-resistant GCT cell lines. Modest clinical activity in heavily pretreated GCT patients was observed.

Clinical implication of ERCC1 overexpression in advanced biliary tract adenocarcinoma patients treated with platinum-based palliative chemotherapy

e22018

Background: Several clinical studies have shown that Excision repair cross-complementation group1 (ERCC1) overexpression is associated with resistance to platinum-based chemotherapy and poor prognoses in several tumors. However these studies have never been tried for biliary tract cancer. The aim of this study was to evaluate the association between ERCC1 expression and treatment outcomes in advanced biliary tract adenocarcinoma patients treated with platinum-based palliative chemotherapy. Methods: We analyzed 45 patients with histologically confirmed adenocarcinoma of biliary tract at 5 institutions between January 2002 and March 2008. ERCC1 expression was assessed by immunohistochemistry from biopsy specimens. Results: ERCC1 expression was positive in 17 of 45 specimens (37.8%). 26 (57.8%) of 45 patients showed clinical benefits(including complete response, partial response and stable disease). Among 26 patients who obtained clinical benefits, seven (27%) were positive for ERCC1 expression and ninety (73%) were negative (p=0.079). With a median follow-up of 6.6 months (range, 0.9–39.4 months), median Progression free survival (PFS) and Overall survival (OS) were 4.4 months (95% CI, 3.2–5.6 months) and 8.5 months (95% CI, 6.1–10.9 months), respectively, for the total study population. On univariate analysis, PFS was 2.3 months for patients with ERCC1 positive tumor and 5.3 months for those with ERCC1 negative tumor (P = 0.053). However OS was significantly longer in the ERCC1-negative group than in the ERCC1-positive group (10.0 vs 4.4 months, respectively; P = 0.001). Other factors affecting the prolongation of OS were objective response rate (P = 0.016) and clinical benefits (P = 0.001). A Cox proportional hazard model showed that negative ERCC1 expression (hazard ratio 0.405, 95% CI, 0.200–0.820; P = 0.012) and clinical benefit (hazard ratio 0.183, 95% CI 0.080–0.420; P = 0.001) were significant independent prognostic factors for the prolongation of survival. Conclusions: These results suggest that advanced biliary tract adenocarcinoma patients with ERCC1-negative tumors show a survival benefit from palliative chemotherapy with a platinum- containing regimen.

No significant financial relationships to disclose.

Ratiometric dosing of irinotecan (IRI) and floxuridine (FLOX) in a phase I trial: A new approach for enhancing the activity of combination chemotherapy

2549

Background: Like many pairs of chemotherapy agents, the combination of IRI and FLOX displays ratio-dependent activity in vitro. CPX-1, a liposome formulation of IRI:FLOX, was developed to maintain a synergistic 1:1 molar ratio in vivo, was highly active in preclinical models, and was evaluated in a phase 1 trial (CLTR0104–101). Methods: Doses were escalated from 30U/m2 (1U= 1 mg IRI + 0.36 mg FLOX) to 270 U/m2 given on day 1 and 15 of each 28 day cycle. Adult patients (pts) with advanced solid tumors, ECOG PS<2, adequate bone marrow, liver, and renal function were eligible; 4 pts per cohort. After defining the MTD, additional pts with CRC were enrolled (extension phase). IRI completed greater than 12 months prior to this trial was allowed in the absence of resistance to IRI. PK was done on day 1 and 15 of the 1st cycle. Results: Safety: The dose escalation phase enrolled 24 pts in 6 cohorts and added 2 pts in the 5th cohort (210U/m2; the MTD) after noting dose limiting diarrhea (3 pts) and neutropenia (1 pt) including one death from dehydration and renal failure due to prolonged diarrhea (gr3) & vomiting (gr2) at 270U/m2. An additional 7 pts with CRC received 210U/m2 in the extension phase. Grade 3/4 adverse events included diarrhea, nausea, vomiting, neutropenia and thrombocytopenia with most occurring at 270U/m2. No new toxicities were observed for this combination. Response: 30/33 pts were evaluable with 2 confirmed PRs (NSCLC and CRC), 21 SD and 7 PD. Median PFS was 5.4 mos. (0.3–11.8 mos.) in 15 pts w/CRC. PK: All pts maintained synergistic plasma IRI:FLOX ratios for 24h. IRI and FLOX AUCs (0-inf) were greater for CPX-1 than expected for conventional drugs. AUCs for SN-38 and 5FU at 210U/m2 were 0.8 ± 0.1 and 10 ± 8.7 μg-hr/mL, respectively, indicating bioavailability for both drugs. Conclusion: CPX-1 was well tolerated in the outpatient setting and evidence of anti-tumor activity was obtained. This is the first clinical evaluation of ratiometric dosing in which a synergistic drug ratio, pre-selected in vitro based on optimal anti-tumor activity, was maintained systemically to enhance therapeutic benefit.

[Table: see text]

Development and assessment of conventional and targeted drug combinations for use in the treatment of aggressive breast cancers

Combination chemotherapy has been at the forefront of cancer treatment for over 40 years. However, the rationale for selecting drug combinations and the process used to demonstrate clinical effectiveness has primarily followed trial and error methodology. Typically, the selection and assessment of combined drug therapies has been based on the effectiveness of each agent as monotherapy in treating the neoplasm and avoiding overlapping toxicities, followed by clinical trials to establish dose scheduling, toxicity, and efficacy. Unfortunately, this scheme is inefficient in terms of the time required to complete and revise these clinical trials based on the outcome to optimize the drug combination. A more rational approach for the development of combination oncology products should consider (i) in vitro assays for assessing therapeutic effects of drug combinations (antagonistic, additive or synergistic interactions) when added simultaneously; (ii) methods for measuring these interactions in vivo; (iii) the importance of understanding pharmacokinetic and biodistribution parameters when using drug combinations; (iv) the need to assess pathways known to contribute to cancer cell survival as well as metastasis; and (iv) the need to assess the fate of different cell populations (cancer and stroma) contributing to the development of cancer. Therefore, the goal of this article is to provide a road map for the preclinical development of drug combination products that will have improved therapeutic activity and a high likelihood of providing beneficial therapeutic outcomes in patients with aggressive cancers with a specific focus on patients with breast cancer.

A phase II study of the antisense oligonucleotide GTI-2040 plus docetaxel and prednisone as first line treatment in hormone refractory prostate cancer (HRPC)

13015

Background: Despite initial responses to chemotherapy, median survival in HRPC remains a dismal 18 mos. Novel therapeutic approaches are clearly needed. The enzyme ribonucleotide reductase (RNR) composed of 2 subunits, R1 and R2 is essential for DNA synthesis and repair. The R2 subunit is often overexpressed in tumors increasing their malignant potential and promoting drug resistance. GTI-2040 (Lorus Therapeutics, Canada) is an antisense oligonucleotide to the R2 subunit downregulating its expression. In preclinical studies, GTI-2040 has shown antitumor activity in prostate cancer xenografts, synergy and non-overlapping toxicity with the taxanes. It is therefore a rational choice for combination with docetaxel in HRPC. Objectives: To determine efficacy of this regimen using PSA response rate. Secondary objectives include: duration of response, TTP, objective tumor response rate, safety and tolerability. Pharmacokinetic (PK) studies will be performed. PBMC will be used to determine RNR activity and R2 subunit quantitation. Methods: HRPC patients with PS 0–2, adequate organ function and no prior chemotherapy were treated with GTI-2040 5mg/kg/d continuous infusion for 14d, docetaxel 75 mg/m2 IV every 21d, and prednisone 5mg twice daily. Results: Twenty-two pts in 5 centers have been enrolled. Pts have received a total of 107 cycles to date. Median age 63 (52–77); median baseline PSA 140 (26–1256); ECOG 0:1:2: 14:7:1; prior radiotherapy in 14 pts. Pts received a median of 5 cycles (2–10). Grade 3/4 hematologic toxicities were lymphophenia (10pts), leukopenia (7pts), and neutropenia (7pts). Anemia (any grade) was seen in 19 pts across 92 cycles. Most frequent non-hematologic toxicities were fatigue and pain. PSA responses seen in 9/22 pts. Objective tumor response:1 PR, 9 SD, 3 PD, 3 off due to toxicity prior to objective response measurement, 3 no measureable lesions, 3 to be assessed. 19 pts off treatment: 9 PD, 4 toxicity (1 toxic death), 2 completed 10 cycles, 2 at investigator’s discretion and 2 withdrew consent. Three pts remain on study. Median TTP estimated at 17 wks. Accrual has been sufficient to meet stage 1 requirements. Final response, toxicity, pK, RNR and R2 subunit analysis will be available and presented.

No significant financial relationships to disclose.

Phase 1 study of CPX-1, a fixed ratio formulation of irinotecan (IRI) and floxuridine (FLOX), in patients with advanced solid tumors

2014

Background: In vitro studies have shown that varying the ratio of individual agents in drug combinations can result in synergistic, additive or antagonistic activity against tumor cells. CPX-1 is a liposomal formulation of IRI and FLOX in a fixed 1:1 molar ratio which was selected as optimal in vitro and confirmed to be synergistic in vivo in preclinical tumor models. CPX-1 overcomes the dissimilar pharmacokinetics (PK) of the individual drugs, enables sustained maintenance of this ratio after IV administration, and was evaluated in a Phase I open-label, dose-escalation study. Methods: Starting dose was 30 U/m2 (1 Unit of CPX-1 contains 1 mg IRI + 0.36 mg FLOX) given on day 1 and 15 of each 28-day cycle. Dose escalation was by modified Fibonacci with 4 subjects/cohort. Eligibility included: ≥ 18 yo; advanced solid tumor; ECOG PS ≤ 2; adequate bone marrow/liver/renal function. PK analysis was done on day 1 and 15 of the first cycle. Results: 26 subjects (16M:10F), median age 54.5 y (21–72), all with prior therapy, enrolled in 6 cohorts with the 5th cohort expanded to 6 subjects. Diagnoses: 8 colorectal, 3 pancreatic, 3 ovarian, 2 breast, 2 gastric, 2 esophageal, 2 sarcomas, 1 renal cell, 1 prostate, 1 NSCLC and 1 sphenoid sinus. Response: 20 subjects evaluable: 2 confirmed PRs (NSCLC 8+ wks; Colon 13+ wks, in a patient with prior IRI exposure) and 13 with SD (8–24+wks). Safety: DLTs were observed at the 6th dose level: 4 subjects with DLTs: 3 diarrhea (one resulting in death due to dehydration/ARF) and one neutropenia. Other possibly related grade 3 and 4 events included one each of: grade 3 diarrhea, grade 3 vomiting, grade 3 neutropenia, grade 3 fatigue, grade 3 compression fracture and arthralgia and pulmonary embolism grade 4. PK: In all 14 subjects analyzed to date the 1:1 molar ratio of IRI to FLOX was maintained for 24 hours and metabolites 5-FU and SN-38 were present in the plasma. Conclusions: CPX-1 represents a new approach to developing drug combinations in which drug ratios are pre-selected in vitro based on optimal antitumor activity and maintained systemically through pharmacokinetic control. Phase 2 studies are planned with a recommended dose of 210U/m2 of CPX-1.

[Table: see text]

Randomized, double-blind, controlled trial of mitoxantrone/prednisone and clodronate versus mitoxantrone/prednisone and placebo in patients with hormone-refractory prostate cancer and pain

PURPOSE

To compare the incidence of palliative response in patients with hormone-resistant prostate cancer (HRPC) treated with mitoxantrone and prednisone (MP) plus clodronate with that of patients treated with MP plus placebo.

MATERIALS AND METHODS

Men with HRPC, bone metastases, and bone pain were randomly assigned to receive clodronate 1,500 mg administered intravenously (IV) or placebo every 3 weeks, in combination with mitoxantrone 12 mg/m2 IV every 3 weeks and prednisone 5 mg orally bid. Patients completed the present pain intensity (PPI) index and Prostate Cancer-Specific Quality-of-Life Instrument at each treatment visit and used a diary to record analgesic use on a daily basis. The primary end point was a reduction to zero or of two points in the PPI or a decrease of 50% in analgesic intake, without increase in either.

RESULTS

The study accrued 209 eligible patients over 44 months. One hundred sixty patients (77%) had mild PPI scores (1 or 2), and 49 (24%) had moderate PPI scores (3 or 4). The primary end point of palliative response was achieved in 46 (46%) of 104 patients on the clodronate arm and in 41 (39%) of 105 patients on the placebo arm (P =.54). The median duration of response, symptomatic disease progression-free survival, overall survival, and overall quality of life were similar between the arms. Subgroup analysis suggested possible benefit in patients with more severe pain.

CONCLUSION

MP provides useful palliation in symptomatic men with HRPC. Clodronate does not increase the rate of palliative response or overall quality of life. Clodronate may be beneficial to patients who have moderate pain, but this requires further confirmation.

Overexpression of the cytoprotective protein clusterin decreases radiosensitivity in the human LNCaP prostate tumour model

OBJECTIVE

To evaluate the effect of clusterin overexpression on radiation-induced tumour growth rates and apoptosis in human prostate LNCaP cells, as prostate cancer cells are relatively resistant to radiation-induced apoptosis and local recurrences are common, but overexpression of the anti-apoptotic protein clusterin can accelerate progression to androgen-independence and to confer a chemoresistant phenotype in various prostate cancer models.

MATERIALS AND METHODS

Western blot analysis and immunohistochemistry were used to compare clusterin expression levels in parental (P) and clusterin-transfected (T) LNCaP cells in vitro and in vivo. The effects of radiation on clusterin-expression in both parental LNCaP/P and clusterin-transfected LNCaP/T tumours were analysed by Northern blot analysis. The cellular response to radiation was determined up to 3 weeks after irradiation using tetrazolium and re-growth assays, and cell-cycle analysis by flow cytometry.

RESULTS

Clusterin mRNA expression increased from undetectable to low levels in LNCaP/P tumours after radiation and more than three-fold in LNCaP/T tumours. Clusterin overexpression decreased the radiosensitivity in a time-dependent manner, reducing the extent of growth arrest and apoptosis by up to 54%. Re-growth assays showed that the improved survival rates of LNCaP/T cells after radiation did not change after 3 days, remaining constant over 3 weeks.

CONCLUSIONS

These results identify clusterin as a promoter of cell survival that may help mediate resistance to radiation-induced apoptosis. Furthermore, clusterin overexpression seems to provide an extended protection against radiation-induced cell cycle arrest and apoptosis.

Phase II study of troxacitabine (BCH-4556) in patients with advanced and/or metastatic renal cell carcinoma: a trial of the National Cancer Institute of Canada-Clinical Trials Group

PURPOSE

A multi-institution phase II study was undertaken by National Cancer Institute of Canada-Clinical Trials Group to evaluate the efficacy and toxicity of intravenous troxacitabine (Troxatyl; Shire Pharmaceuticals Plc, Laval, Quebec, Canada), in patients with renal cell carcinoma.

PATIENTS AND METHODS

Between June 1999 and March 2000, 35 patients (24 male) with a mean age of 60 years who had advanced and/or metastatic disease were treated with troxacitabine given as an intravenous infusion over 30 minutes at a dose of 10 mg/m2 intravenously, once every 3 weeks.

RESULTS

Of the 33 of 35 patients evaluable for response, there were two confirmed partial responses, 21 patients had stable disease (median duration, 4.4 months), and 10 patients had progressive disease. Eight patients remained stable for more than 6 months, of whom six remain free of progression. The most common drug-related nonhematologic toxicities observed were skin rash (77.1%), hand-foot syndrome (68.6%), alopecia (51.4%), fatigue (51.4%), and nausea (57.1%). Out of a total of 145 cycles of treatment, 98 were given without steroid premedication, whereas 47 cycles were given with steroid premedication. Without premedication, skin rash occurred in 37% of cycles compared with 26% when steroids were given prophylactically.

CONCLUSION

Troxacitabine given at a dose of 10 mg/m2 once every 3 weeks was well tolerated in patients with metastatic renal cell cancer, with common toxicities being a moderate to severe granulocytopenia and skin rash. Steroid premedication may reduce the frequency and severity of the skin rash. Our current study suggests that the nucleoside analog troxacitabine may have modest activity against renal cell carcinoma; however, larger studies are required to confirm this.

Antitumor activity of antisense clusterin oligonucleotides is improved in vitro and in vivo by incorporation of 2'-O-(2-methoxy)ethyl chemistry

Phosphorothioate (P=S) antisense oligonucleotides (ASO) targeting the cell survival gene clusterin synergistically enhance castration- and chemotherapy-induced apoptosis in prostate cancer xenografts. This study compares efficacy, tissue half-lives, and toxicity of P=S clusterin ASO to third-generation backbone 2'-O-(2-methoxy)ethyl (2'MOE) ribose-modified clusterin ASO. Northern analysis quantified changes in clusterin mRNA levels in human PC-3 cells and tumors. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay measured effects of combined clusterin ASO plus paclitaxel on PC-3 cell growth. Athymic mice bearing PC-3 tumors were treated with paclitaxel plus either P=S clusterin ASO, 2'-MOE clusterin ASO, or mismatch control oligonucleotides for 28 days. Weekly body weights and serum parameters were measured to assess toxicity. Tissue half-life of P=S and 2'-MOE ASO in PC-3 tumors was assessed using capillary gel electrophoresis (CGE). Both 2'-MOE and P=S ASO decreased clusterin mRNA levels in a dose-dependent and sequence-specific manner. 2'-MOE ASO more potently suppressed clusterin mRNA (80 versus 40% at 500 nM) compared with P=S ASO. IC(50) of paclitaxel was equally reduced (50--75%) by both compounds. In vivo tissue half-life was significantly longer for 2'-MOE-modified ASO than for P=S ASO (5 versus 0.5 days). Using CGE, >90% of detected 2'-MOE ASO in tumor tissue was full length. Weekly administration of 2'-MOE clusterin ASO was equivalent to daily P=S clusterin ASO in enhancing paclitaxel efficacy in vivo. 2'-MOE-modified ASO potently suppressed clusterin expression and prolonged tissue half-lives with no additional side effects. These results support the use of 2'-MOE-modified ASO over conventional P=S ASO by potentially increasing potency and allowing longer dosing intervals in clinical trials.

Use of antisense oligonucleotides targeting the antiapoptotic gene, clusterin/testosterone-repressed prostate message 2, to enhance androgen sensitivity and chemosensitivity in prostate cancer

BACKGROUND

Androgen resistance develops, in part, from upregulation of antiapoptotic genes after androgen withdrawal. Identification and targeting of genes mediating androgen-independent (AI) progression may lead to development of novel therapies that delay hormone-refractory prostate cancer. Clusterin is a cell survival gene, that increases after androgen ablation. Here, we review clusterin's functional role in apoptosis and the ability of antisense oligonucleotides (ASOs) against clusterin to enhance apoptosis in prostate cancer xenograft models.

RESULTS

Immunostaining of radical prostatectomy specimens confirm that clusterin is highly expressed in 80% prostate cancer cells after neoadjuvant hormone therapy, but is low or absent (<20%) in untreated specimens. Clusterin levels increase >10 fold in regressing Shionogi tumors after castration. Pretreatment of mice bearing androgen-dependent Shionogi tumors with calcium antagonists inhibited castration-induced apoptosis, tumor regression, and clusterin gene upregulation, illustrating that clusterin is an apoptosis-associated gene and not an androgen-repressed gene. 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 by 70% and resulted in earlier onset and more rapid apoptotic tumor regression, with significant delay in recurrence of AI tumors. Species-specific clusterin ASOs also increased the cytotoxic effects of paclitaxel, reducing the 50% inhibitory concentration (IC(50)) of PC-3 and Shionogi cells by 75% to 90%. Although clusterin ASOs had no effect on the growth of established AI Shionogi or PC-3 tumors, clusterin ASOs synergistically enhanced paclitaxel-induced tumor regression in both Shionogi and PC-3 models.

CONCLUSIONS

Collectively, these data identify clusterin as an antiapoptosis protein, upregulated in an adaptive cell-survival manner by androgen ablation and chemotherapy, which confers resistance to various cell-death triggers. Inhibition of clusterin upregulation using clusterin ASOs can enhance cell death after treatment with androgen ablation and chemotherapy.

Decision model for optimizing respirator protection

Respirators are widely used for protection against inhaled toxins. The emphasis of research and implementation effort has evolved through several stages: the respirator device itself, use situation, respirator program factors under employer control, individual worker factors not under employer control, and occupational health systems. For this study, a computer-simulation decision assistance model was developed to assess the impact of various factors on the number of workers receiving adequate protection. Factors include the respirator protection factor, identification of sites needing respirator protection, selection of proper device, availability when needed, frequency of ever use, regularity of use among users, and variability in personal susceptibility or other factors. This analysis demonstrates that for both moderate-risk and high-risk (i.e., IDLH, immediately dangerous to life and health) exposures under current circumstances, the actual protection afforded depends upon the optimization of program factors and detection of atypical outlier persons and worksites. Therefore, programs and research must focus on these areas. Occupational medicine specialists should help optimize these areas and, in addition, use each case of respiratory protection failure as an index case to improve the overall programs.

Expression of an elongation factor 1 gamma-related sequence in adenocarcinomas of the colon

The authors have previously reported that a messenger RNA (mRNA) bearing 60% homology to elongation factor 1 gamma in Artemia salina was overexpressed in 7 of 9 pancreatic tumors relative to normal appearing adjacent tissue. The purpose of the present study was to determine if this pattern of overexpression is also detected in colorectal carcinoma. Overexpression was observed in 25 of 29 colorectal carcinomas, relative to normal adjacent tissue. Of them, mRNA was overexpressed in 2 tumors classified as Dukes' D, in 8 of 11 tumors classified as Dukes' B2, and in 15 of 16 tumors classified as Dukes' C2.

Monoclonal antibody study of the subcellular localization and DNA-stimulating activity of murine sarcoma virus-activated transformation-associated proteins

Previously, we reported the monoclonal antibody detection of transformation-associated proteins (TAP) in ts110 murine sarcoma virus-transformed normal rat kidney (6M2) cells (Chan et al., 1986). In this study, we used the same monoclonal antibody to investigate the subcellular localization, the fate and the mitogenic activity of TAP, as well as the correlationship between TAP synthesis and the expression of transformation properties of 6M2 cells. It was found that TAP were localized in the cytoplasm (probably the Golgi apparatus) of 6M2 cells. TAP were found as three intracellular polypeptides (mol wt of 66K, 63K, and 60K, respectively), and were rapidly released into extracellular medium. Upon release, TAP changed to two extracellular polypeptides (mol wt of 68K and 64K, respectively). Furthermore, the synthesis of TAP was temperature sensitive and correlated closely with the expression of transformation properties of the 6M2 cells. TAP have been purified by monoclonal antibody-affinity column chromatography and found to have a synergistic effect with insulin in stimulating the DNA synthesis of normal rat kidney cells.