Identification of a nucleoside/nucleobase transporter from Plasmodium falciparum, a novel target for anti-malarial chemotherapy.

Plasmodium, the aetiologic agent of malaria, cannot synthesize purines de novo, and hence depends upon salvage from the host. Here we describe the molecular cloning and functional expression in Xenopus oocytes of the first purine transporter to be identified in this parasite. This 422-residue protein, which we designate PfENT1, is predicted to contain 11 membrane-spanning segments and is a distantly related member of the widely distributed eukaryotic protein family the equilibrative nucleoside transporters (ENTs). However, it differs profoundly at the sequence and functional levels from its homologous counterparts in the human host. The parasite protein exhibits a broad substrate specificity for natural nucleosides, but transports the purine nucleoside adenosine with a considerably higher apparent affinity (K(m) 0.32+/-0.05 mM) than the pyrimidine nucleoside uridine (K(m) 3.5+/-1.1 mM). It also efficiently transports nucleobases such as adenine (K(m) 0.32+/-0.10 mM) and hypoxanthine (K(m) 0.41+/-0.1 mM), and anti-viral 3'-deoxynucleoside analogues. Moreover, it is not sensitive to classical inhibitors of mammalian ENTs, including NBMPR [6-[(4-nitrobenzyl)thio]-9-beta-D-ribofuranosylpurine, or nitrobenzylthioinosine] and the coronary vasoactive drugs, dipyridamole, dilazep and draflazine. These unique properties suggest that PfENT1 might be a viable target for the development of novel anti-malarial drugs.

Determining factors which predict response to primary medical therapy in breast cancer using a single fine needle aspirate with immunocytochemical staining and flow cytometry.

The increasing use of neoadjuvant chemotherapy and endocrine therapy in the management of breast cancer has lead us to evaluate and optimise the standard technique of cytocentrifugation of a single fine needle aspirate (FNA) taken from a breast tumour in-vivo, to determine a range of both immunocytochemical and flow cytometric factors which are predictive of response to primary medical therapy. Some of these factors are also of prognostic significance in early stage disease. An analysis of the cellularity and immunocytochemical staining characteristics of FNAs obtained from a series of 206 patients with palpable breast cancers indicate that in a sample of 46 cases it is possible to measure oestrogen receptor, progesterone receptor and c-erbB-2 providing over 400 cells per slide are obtained, with material obtained in a single FNA prepared by cytocentrifugation, using standard immunocytochemical methods. The staining results obtained were comparable to those obtained using frozen or paraffin embedded tissue sections taken from the same tumour. In addition an estimate of the proliferation indices could be made by flow cytometric analysis of the residual cell suspension fluid with measurement of DNA index and S-phase fraction in 131/164 (80%) and 110/164 (67%) of cases respectively. Providing all FNAs obtained for cytocentrifugation were taken at first presentation rather than immediately following a standard FNA, then it was possible to obtain adequately cellular (> 400 cells/slide) samples in 96 out of 126 (75%) of the last cohort of breast aspirates. These effects may be independent of T stage but not histological type as patients with lobular tumours only produced cellular aspirates in 1/7 (14%) of cases.(ABSTRACT TRUNCATED AT 250 WORDS)