Investigating the mechanism of enhanced cytotoxicity of HPMA copolymer-Dox-AGM in breast cancer cells.

Recently we have described an HPMA copolymer conjugate carrying both the aromatase inhibitor aminoglutethimide (AGM) and doxorubicin (Dox) as combination therapy. This showed markedly enhanced in vitro cytotoxicity compared to the HPMA copolymer-Dox (FCE28068), a conjugate that demonstrated activity in chemotherapy refractory breast cancer patients during early clinical trials. To better understand the superior activity of HPMA copolymer-Dox-AGM, here experiments were undertaken using MCF-7 and MCF-7ca (aromatase-transfected) breast cancer cell lines to: further probe the synergistic cytotoxic effects of AGM and Dox in free and conjugated form; to compare the endocytic properties of HPMA copolymer-Dox-AGM and HPMA copolymer-Dox (binding, rate and mechanism of cellular uptake); the rate of drug liberation by lysosomal thiol-dependant proteases (i.e. conjugate activation), and also, using immunocytochemistry, to compare their molecular mechanism of action. It was clearly shown that attachment of both drugs to the same polymer backbone was a requirement for enhanced cytotoxicity. FACS studies indicated both conjugates have a similar pattern of cell binding and endocytic uptake (at least partially via a cholesterol-dependent pathway), however, the pattern of enzyme-mediated drug liberation was distinctly different. Dox release from PK1 was linear with time, whereas the release of both Dox and AGM from HPMA copolymer-Dox-AGM was not, and the initial rate of AGM release was much faster than that seen for the anthracycline. Immunocytochemistry showed that both conjugates decreased the expression of ki67. However, this effect was more marked for HPMA copolymer-Dox-AGM and, moreover, only this conjugate decreased the expression of the anti-apoptotic protein bcl-2. In conclusion, the superior in vitro activity of HPMA copolymer-Dox-AGM cannot be attributed to differences in endocytic uptake, and it seems likely that the synergistic effect of Dox and AGM is due to the kinetics of intracellular drug liberation which leads to enhanced activity.     

Therapeutic implications of low lymphocyte count in non-ST segment elevation acute coronary syndromes

BackgroundLow lymphocyte count (LLC), a surrogate for inflammation, has emerged as a potential risk factor for cardiovascular outcomes, especially new ischemic events. To identify patients with non-ST segment elevation acute coronary syndromes (NSTEACS) who benefit from an invasive revascularization strategy remains a challenge. We sought to determine if patients with high-risk NSTEACS who exhibited LLC have a greater reduction in long-term post-discharge myocardial infarction (MI) when managed under a revascularization invasive strategy (RIS) as compared with conservative strategy (CS).MethodsNine hundred seventy two consecutive patients with high-risk NSTEACS were treated under two revascularization strategies (RS): 1) CS, from January 2001 to October 2002 (345 patients; 35.5%) and 2) RIS, from November 2002 to May 2005 (627 patients; 64.5%). LLC was defined as lymphocytes count ≤ 1200 cells/ml (1 vs. 2–4 quartiles). The association between the type of RS and MI was stratified by lymphocyte count status and assessed by Cox regression adapted for competing events.ResultsAt 3-year follow-up, 145 deaths (14.9%), 135 MI (13.9%) and 76 revascularization procedures (7.8%) were registered. In a multivariable setting, LLC patients exhibited a greater MI risk reduction when managed under RIS (HR: 0.40; 95% CI = 0.22–0.72, p = 0.003). Conversely, when LLC was not present, no difference in the rate of MI was detected between the two RS.ConclusionsLLC identifies a subgroup of patients with greater reduction in the risk of postdischarge MI when a RIS is applied.