HIV-1 integrase inhibitors are substrates for the multidrug transporter MDR1-P-glycoprotein

BACKGROUND: The discovery of diketoacid-containing derivatives as inhibitors of HIV-1 Integrase (IN) (IN inhibitors, IINs) has played a major role in validating this enzyme as an important target for antiretroviral therapy. Since the in vivo efficacy depends on access of these drugs to intracellular sites where HIV-1 replicates, we determined whether the IINs are recognized by the multidrug transporter MDR1-P-glycoprotein (P-gp) thereby reducing their intracellular accumulation. To address the effect of IINs on drug transport, nine quinolonyl diketo acid (DKA) derivatives active on the HIV-1 IN strand transfer (ST) step and with EC50 ranging from 1.83 to >50 μm in cell-based assays were tested for their in vitro interaction with P-gp in the CEM-MDR cell system. IINs were investigated for the inhibition and induction of the P-gp function and expression as well as for multidrug resistance (MDR) reversing ability. RESULTS: The HIV-1 IINs act as genuine P-gp substrates by inhibiting doxorubicin efflux and inducing P-gp functional conformation changes as evaluated by the modulation of UIC2 mAb epitope. Further, IINs chemosensitize MDR cells to vinblastine and induce P-gp expression in drug sensitive revertants of CEM-MDR cells. CONCLUSION: To our knowledge, this is the first demonstration that HIV-1 IINs are P-gp substrates. This biological property may influence the absorption, distribution and elimination of these novels anti HIV-1 compounds

[Results of a questionnaire on malignant tumors of the oral cavity].

A set of 23 questions on malignant neoplasms of oral cavity has been submitted to a group of 38 graduate in dentistry and dental prosthesis, at the time of their qualifying examination. The answers reveal a sufficient degree of knowledge of the problem but also indicate that some specific aspects of this important question should be probed

Indagine sui livelli di conoscenza del carcinoma orale: risultati della seconda somministrazione di un questionario.

A test on clinical, epidemiologica and etiological aspects of oral cancer has been submitted for the second time to a group of graduates in dentistry and dental prosthesis at the time of their qualifying examination, in order to value the degree of their knowledge about the most serious stomatological pathology. The results, compared to those ones of the first test-submission, and the following considerations are here exposed. A fairly good knowledge on oral cancer has been noticed in most of the interviewed, as well as in 1989. In particular, a good degree of knowledge on etiologica factors, therapeutic programs and prognosis has been remarked while gaps and incongruousness on precancerous lesions, staging, epidemiological and diagnostic aspects have been found. The authors, at last, lay stress on the difference between the present answers on oral cancer diagnostic delay and those ones of 1989

AZT-induced hypermethylation of human thymidine kinase gene in the absence of total DNA hypermethylation

Genome-wide DNA hypermethylation induced by 3'-azido-3'-deoxythymidine (AZT) has been suggested to be involved in the development of AZT resistance. We used a CD4 T-lymphoblastoid CEM line and its AZT-resistant MT500 variant with reduced thymidine kinase activity, Evaluation of total DNA methylation, after AZT treatment, failed to show an increase in the 5-methylcytosine level in both parental and AZT-resistant cells, The effect was instead observed at a more specific gene level, on the three HpaII sites present in exon 1 of the human thymidine kinase gene, These results suggest that AZT treatment can induce site-specific hypermethylation, even in the absence of a more general DNA hypermethylating effect

Pentose phosphate pathway alterations in multi-drug resistant leukemic T-cells: 31P NMR and enzymatic studies

31P NMR studies were carried out on the parental drug-sensitive human T-lymphoblastoid cell line CCRI-CEM (CEM) and its multi-drug-resistant (MDR) CEM-VBL100 variants to assess the role of the pentose phosphate (PP) in MDR expression. CEM and CEM-VBL100 were incubated in the presence of 2-deoxyglucose as recently proposed by our group. Accumulation of 2-deoxyglucose 6-phosphate was much lower in the drug-resistant than in sensitive cells indicating PP shunt activation in the MDR variants. This result was confirmed by enzymatic analyses which demonstrated that with respect to the parental line the MDR variant was characterized by a) unaltered hexokinase activity; b) higher glucose 6-phosphate dehydrogenase activity; c) increased levels of reduced glutathione and marked increase of glutathione peroxidase activity after cell exposure to an oxidizing agent (tert-butylhydroperoxide). These results support the view that cell detoxification mechanisms mediated by the pentose phosphate pathway may contribute to the expression of MDR in tumours

Intracellular Metabolism of 3'-Azido-3'-deoxythymidine (AZT): A Nuclear Magnetic Resonance Study on T-Lymphoblastoid Cell Lines with Different Resistance to AZT.

This paper reports the results of 31P and 1H nuclear magnetic resonance (NMR) studies on the uptake and phosphorylation of 3'-azido-3'-deoxythymidine (AZT) in the human CD4+ T-lymphoblastoid cell line CCRF-CEM (CEM-1.3) and in its AZT-resistant cell variant MT-500, isolated by prolonged culturing of CEM cells in the presence of increasing AZT concentrations. After 3 hr of incubation in the presence of 0.5 mM AZT, both AZT and its monophosphorylated form (AZT-MP) could be detected in the sensitive cell line in concentrations above the NMR detection levels. In another cell line, MOLT-4, which is less sensitive to AZT effects, the intracellular level of AZT-MP was much lower and was only slightly raised by increasing the concentration of AZT in the extracellular and intracellular compartments. In the AZT-resistant clone MT-500, characterized by a very low thymidine kinase (TK, EC 2.7.1.21) activity with respect to the parental clone, the intracellular AZT-MP concentration was below detection (<0.02 nmol/10(6) cells). Since, however, not only AZT-MP but also AZT signals failed to be detected in MT-500 extracts following cell incubation with AZT, it was concluded that a TK deficiency cannot be the exclusive mechanism of AZT resistance in these cells. The possible effects of additional mechanisms of drug resistance, such as specific AZT cell extrusion and limited permeation, are discussed, together with the new prospects offered by NMR spectroscopy to further evaluate the limiting steps for the utilization of antiretroviral nucleoside analogues

De Cifris Cryptanalysis

Cryptanalysis is a fascinating aspect of cryptology, but it is often surrounded by a mix of doubt and suspicion. In this book some active Italian researchers will provide rigorous explanations of modern cryptanalytic methods, revealing this discipline for what it is: a beautiful subject where advanced mathematical theories and tools intertwine with practical estimates of the security of real-life cryptosystems