ABSTRACT
BACKGROUND: Limited stage small cell lung cancer (SCLC) represents a minority of SCLC. Despite extensive clinical trials, standard treatment remains cisplatin-based chemotherapy and thoracic irradiation (TI). This study focused on the interaction of cisplatin/radiation with the anti-human DR5 monoclonal antibody TRA-8 in SCLC cells. TRA-8 binds specifically to DR5 and has been shown to activate apoptosis. METHODS: Four human SCLC cell lines were utilized for experimentation (SCLC-41, SCLC-58, SCLC-68, and SCLC-74). Immunoblot analysis was used to determine relative protein levels of DR5, DR4 and pro-caspase 8 for each cell line. Using a tetrazolium-based assay (XTT), the IC(50) values for cisplatin with or without TRA-8 were determined for the SCLC cell lines. Four SCLC lines were assayed with a combination of TRA-8 (10 µg/ml), 2 Gy radiation and various concentrations of cisplatin. Apoptosis was evaluated using Annexin V-FITC and cleaved caspase immunoblotting. Using a SCLC-58 subcutaneous xenograft model, treatment began 21 d after tumor cell injection. Treatment included weekly cisplatin (4 mg/kg) and radiation of 1 Gy (24 h after cisplatin) and TRA-8 (200 µg) was administered i.p. twice weekly for three weeks. RESULTS: Immunoblot analysis showed similar levels of DR5 for all cell lines with variable levels of DR4. Various concentrations of TRA-8 antibody (≤ 10 µg/ml) induced no significant cytotoxicity in the SCLC cell lines. The in vitro combination treatment with TRA-8 (10 µg/ml), 1.25 µg/ml cisplatin and 2 Gy radiation showed increased cytotoxicity when compared to combinations without TRA-8. Furthermore, the triple combination demonstrated the greatest amount of apoptosis as measured by Annexin V staining. The in vivo studies showed the combination of 1G y, cisplatin and TRA-8 extended the tumor doubling time to 44 d as compared to any doublet treatment groups that ranged from 12 to 20 d. Analysis of survival data showed 100% of the combination group (RT+cisplatin+TRA-8) were alive 65 d after treatment began whereas all doublet treatment groups showed 50% or less survival. CONCLUSIONS: These studies showed increased cytotoxicity when TRA-8 was added to radiation/cisplatin in SCLC. This effect was demonstrated in vitro and in vivo. TRA-8 represents a promising new agent in the treatment of SCLC.
Subject(s)
Antibodies, Monoclonal/administration & dosage , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Cisplatin/administration & dosage , Lung Neoplasms/therapy , Radiation, Ionizing , Receptors, TNF-Related Apoptosis-Inducing Ligand/antagonists & inhibitors , Small Cell Lung Carcinoma/therapy , Animals , Annexin A5/pharmacology , Apoptosis/drug effects , Apoptosis/radiation effects , Cell Line, Tumor/drug effects , Cell Line, Tumor/radiation effects , Cell Survival , Chemoradiotherapy , Dose-Response Relationship, Drug , Dose-Response Relationship, Radiation , Humans , In Vitro Techniques , Lung Neoplasms/pathology , Mice , Mice, Nude , Sensitivity and Specificity , Small Cell Lung Carcinoma/pathology , Treatment OutcomeABSTRACT
The goal of this study was to design paclitaxel (PTX)-monoclonal antibody (mAb) prodrug conjugates (PTXMAbs) with the ability to deliver therapeutically significant doses of the drug to the tumor while avoiding the previously observed solubility limitations of conjugates with PTX:mAb molar ratios of >3. New PTX conjugates were synthesized using the discrete poly(ethylene glycol) (dPEG) as linkers. These compounds, PTX-L-Lys[(dPEG12)(3)-dPEG4]-dPEG6-NHS (9a and 9b, for L = GL or SX, respectively), were then conjugated to the antiepidermal growth factor receptor mAb, C225 at increasing PTX:C225 ratios, producing completely soluble conjugates. Unlike the earlier PTXMAbs, buffered solutions of these conjugates remained homogeneous for extended periods of time. Fluorescence-activated cell sorting (FACS) analysis indicated preserved immunogenicity of the conjugates at all four substitution ratios, while cytotoxicity studies in MDA-MB-468 breast cancer cells indicated preservation of drug cytotoxicity. These conjugates may have potential in the development of high-drug-load tumor-targeting taxanes.
Subject(s)
Antineoplastic Agents, Phytogenic/administration & dosage , Drug Delivery Systems/methods , Immunoconjugates/pharmacology , Paclitaxel/administration & dosage , Antibodies, Monoclonal/therapeutic use , Breast Neoplasms/drug therapy , Cell Line, Tumor , Cell Survival/drug effects , Drug Stability , ErbB Receptors/immunology , Female , Humans , Immunoconjugates/chemistry , Polyethylene GlycolsABSTRACT
Conjugates of curcumin to two differently sized poly(ethylene glycol) molecules were synthesized in an attempt to overcome the low aqueous solubility of this natural product with cytotoxic activity against some human cancer cell lines. The soluble conjugates exhibited enhanced cytotoxicity as compared to that of the parent drug. Synthesis, analyses of the rate of drug release, and cytotoxicity studies are herein reported. The water-soluble conjugates may provide information useful for the development of injectable curcumin conjugates.
