Schedule treatment design and quantitative in vitro evaluation of chemotherapeutic combinations for metastatic prostate cancer therapy
Preclinical evaluation is essential for a rational design of combination chemotherapy as some agents, with known mechanisms of action and non-overlapping toxicities may increase the therapeutic index of anticancer drugs, whose clinical success is hindered by side effects and drug resistance. The present study investigated new drug combinations with potential outcome for the treatment of metastatic prostate cancer. This final clinical stage exhibits predominantly hormone-refractory prostate cancer (HRPC) cells but also a minority of hormone responsive cells.
Growth inhibition activity of simultaneous and sequential combinations was evaluated by resazurin assay. In vitro evaluation of synergism, additivity, or antagonism, against prostate cancer cell lines, was performed by the median effect analysis. The importance of dosage, exposure time, drug ratio, and type of treatment were investigated and compared.
Most simultaneous combinations of two drugs with different mechanisms of action or of two topoisomerase II inhibitors resulted in mild antagonism of antiproliferative effects, particularly notorious at high cell death. Imatinib–mitoxantrone and ciprofloxacin–etoposide combinations were exceptions, as they yielded additivity and dose reduction index (DRI) values of 2.6 and 3.5-fold for mitoxantrone and etoposide, respectively. Sequential combinations (ciprofloxacin or imatinib pre-treatment) revealed additive growth inhibition effects, translated in much higher DRI values (from 7.0 to 15.3-fold). Moderate synergism was restricted to sequential ciprofloxacin combinations at high cell death.
Ciprofloxacin and imatinib significantly improve growth inhibition activity of standard antineoplastic drugs in a schedule-dependent manner and, therefore, may have an important role as adjuvant therapeutic agents in a clinical setting.
KeywordsHRPC Chemosensitization Imatinib Dose reduction index Median effect analysis
- 3.Di Lorenzo G, Autorino R, De Laurentiis M, Bianco R, Lauria R, Giordano A, De Sio M, D’Armiento M, Bianco AR, De Placido S (2003) Is there a standard chemotherapeutic regimen for hormone-refractory prostate cancer? Present and future approaches in the management of the disease. Tumori 89:349–360PubMedGoogle Scholar
- 14.Tannock IF, Osoba D, Stockler MR, Ernst DS, Neville AJ, Moore MJ, Armitage GR, Wilson JJ, Venner PM, Coppin CM, Murphy KC (1996) Chemotherapy with mitoxantrone plus prednisone or prednisone alone for symptomatic hormone-resistant prostate cancer: a Canadian randomized trial with palliative end points. J Clin Oncol 14:1756–1764PubMedGoogle Scholar
- 16.Hardman JG, Limbird LE, Gilman AG (2001) Goodman LSPbot: Goodman & Gilman’s the pharmacological basis of therapeutics. In: Hardman JG, Limbird LE (eds)/Alfred Goodman Gilman (consulting ed) 10th edn. McGraw-Hill, New York, LondonGoogle Scholar
- 47.Naber KG, Sorgel F, Kees F, Jaehde U, Schumacher H (1989) Pharmacokinetics of ciprofloxacin in young (healthy volunteers) and elderly patients, and concentrations in prostatic fluid, seminal fluid, and prostatic adenoma tissue following intravenous administration. Am J Med 87:57S–59SCrossRefPubMedGoogle Scholar