Chemically synthesized peptide libraries as a new source of BBB shuttles. Use of mass spectrometry for peptide identification.

The blood-brain barrier (BBB) is a biological barrier that protects the brain from neurotoxic agents and regulates the influx and efflux of molecules required for its correct function. This stringent regulation hampers the passage of brain parenchyma-targeting drugs across the BBB. BBB shuttles have been proposed as a way to overcome this hurdle because these peptides can not only cross the BBB but also carry molecules which would otherwise be unable to cross the barrier unaided. Here we developed a new high-throughput screening methodology to identify new peptide BBB shuttles in a broadly unexplored chemical space. By introducing d-amino acids, this approach screens only protease-resistant peptides. This methodology combines combinatorial chemistry for peptide library synthesis, in vitro models mimicking the BBB for library evaluation and state-of-the-art mass spectrometry techniques to identify those peptides able to cross the in vitro assays. BBB shuttle synthesis was performed by the mix-and-split technique to generate a library based on the following: Ac-d-Arg-XXXXX-NH2 , where X were: d-Ala (a), d-Arg (r), d-Ile (i), d-Glu (e), d-Ser (s), d-Trp (w) or d-Pro (p). The assays used comprised the in vitro cell-based BBB assay (mimicking both active and passive transport) and the PAMPA (mimicking only passive diffusion). The identification of candidates was determined using a two-step mass spectrometry approach combining LTQ-Orbitrap and Q-trap mass spectrometers. Identified sequences were postulated to cross the BBB models. We hypothesized that some sequences cross the BBB through passive diffusion mechanisms and others through other mechanisms, including paracellular flux and active transport. These results provide a new set of BBB shuttle peptide families. Furthermore, the methodology described is proposed as a consistent approach to search for protease-resistant therapeutic peptides. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Serum cholesterol levels and survival after rtPA treatment in acute stroke.

BACKGROUND: According to the reverse epidemiology hypothesis, high cholesterol levels might be protective and associated with greater survival rates under certain conditions. In stroke patients, a clear correlation between lipid levels and mortality after ischaemic and hemorrhagic strokes has been demonstrated. The aim of this study was to analyze the impact of lipid levels on 3-month mortality in patients with ischaemic stroke (IS) homogeneously treated with intravenous rtPA and admitted to a monitored acute stroke unit. METHODS: Retrospective analysis of a prospective cohort of 220 patients with an IS treated with rtPA within the first 4.5 h in a single tertiary hospital from January 2005 to August 2010. RESULTS: Mortality at 3 months was 15.0%. Univariate analysis showed that age, NIHSS at admission, heart failure, and atrial fibrillation were directly related to 3-month mortality; cholesterol, triglycerides, and low density lipoprotein were inversely associated. The death rate by cholesterol level was 5.5% for the highest tertile (>192 mg/dl), 13.7% for the middle (192-155 mg/dl), and 25.7% for the lowest (<155 mg/dl), P = 0.003. Multivariate analysis showed that amongst the lipid determinations, only cholesterol [OR: 0.985 (95% CI: 0.972-0.998), P = 0.021] was inversely associated with 3-month mortality. The 'protective' effect of cholesterol was independent of stroke severity and remained significant in non-lacunar strokes. CONCLUSIONS: Survival of stroke patients receiving current, most effective medical treatment is related to blood cholesterol levels, with an inverse relationship between cholesterol and mortality. The mechanism of this apparently paradoxical situation remains unexplained but merits further research.

Brain metastasis models: What should we aim to achieve better treatments?

Brain metastasis is emerging as a unique entity in oncology based on its particular biology and, consequently, the pharmacological approaches that should be considered. We discuss the current state of modelling this specific progression of cancer and how these experimental models have been used to test multiple pharmacologic strategies over the years. In spite of pre-clinical evidences demonstrating brain metastasis vulnerabilities, many clinical trials have excluded patients with brain metastasis. Fortunately, this trend is getting to an end given the increasing importance of secondary brain tumors in the clinic and a better knowledge of the underlying biology. We discuss emerging trends and unsolved issues that will shape how we will study experimental brain metastasis in the years to come.

Severity of allergic rhinitis impacts sleep and anxiety: results from a large Spanish cohort.

BACKGROUND: Allergic rhinitis (AR) is a highly prevalent disease that generates high social and health care costs and also has a significant effect on quality of life and quality of sleep. It has also been related to some psychological disorders like anxiety or depression. OBJECTIVE: To evaluate anxiety, depression, and quality of sleep and life alteration in a group of patients with perennial AR compared to a group of seasonal AR patients. METHODS: Six-hundred seventy adults (> 18 years) with perennial and seasonal AR were recruited consecutively in 47 centers in Spain. Individuals were grouped in "Perennial" and "Seasonal" according to the seasonality of their symptoms. Anxiety, depression, sleep quality and health related quality of life were evaluated using the Hospital Anxiety and Depression Scale, Medical Outcomes Study Sleep Scale (MOS Sleep Scale) and the Health-related quality of life questionnaire ESPRINT-15, respectively. Both groups of patients were evaluated in and out of the pollen season. RESULTS: AR symptoms are related to worse quality of life and more anxiety and depression symptoms. Indeed, symptom severity also correlates with worse outcomes (quality of life, sleep and depression/anxiety) regardless allergen seasonality. Symptoms severity, compared with seasonality and persistence, is the most important factor related with more anxiety and depression and poor sleep. However, symptoms severity, persistence and seasonality are independently affecting the quality of life in patients with AR. CONCLUSIONS: Although AR symptoms have a great impact on depression and anxiety symptoms, quality of life and quality of sleep in all AR patients, as expected, individuals with more severe AR seem to suffer more intensely their effects.

Increased immune cell infiltration in patient-derived tumor explants treated with Traniplatin: an original Pt(iv) pro-drug based on Cisplatin and Tranilast.

Elevated intra-tumoral immune infiltrate is associated with an improved prognosis in cancer of distinct origins. Traniplatin (TPT) is a novel platinum(iv) pro-drug based on Cisplatin (CDDP) and the marketed drug Tranilast. When compared in vitro to Cisplatin, TPT showed increased cytotoxic activity against colon and lung cancer cells but decreased activity against immune cells. In addition, TPT efficiency was evaluated in tumor explants derived from colorectal cancer samples from patients subjected to intended curative surgery. TPT induced strong intra-tumoral cytotoxic activity yet was associated with an elevated presence of immune cell infiltrate, suggesting a reduced cytotoxic activity against immune cells in colorectal cancer.

Antibacterial evaluation of a collection of norfloxacin and ciprofloxacin derivatives against multiresistant bacteria.

The objective of this study was to analyse an array of ciprofloxacin and norfloxacin derivatives in order to determine those with good activity against bacteria that already present fluoroquinolone resistance associated with mutations in the gyrA and/or parC genes. Four norfloxacin and 20 ciprofloxacin derivatives were synthesised and tested against quinolone-susceptible and -resistant Escherichia coli, Acinetobacter baumannii, Stenotrophomonas maltophilia and Staphylococcus aureus strains using a microdilution test. Among the derivatives, the 4-methyl-7-piperazine ciprofloxacin derivative showed a minimum inhibitory concentration for 50% of the organisms that was 16- and 8-fold lower than ciprofloxacin for A. baumannii and S. maltophilia, respectively. When the methyl group at position 4 in the piperazine ring was substituted by ethyl, butyl or heptyl groups, activity against A. baumannii steadily decreased. The 7-(4-methyl)-piperazine ciprofloxacin derivative (UB-8902) showed very good activity against these multiresistant microorganisms including A. baumannii and S. maltophilia.

AT514, a cyclic depsipeptide from Serratia marcescens, induces apoptosis of B-chronic lymphocytic leukemia cells: interference with the Akt/NF-kappaB survival pathway.

Clinical treatment of B-cell chronic lymphocytic leukemia (B-CLL) is limited by the progressive drug resistance and nonselectivity of most drugs towards malignant cells. Depsipeptides are present in certain bacteria and display potent antitumor activity. We have studied the effect of the novel cyclodepsipeptide AT514 (serratamolide) from Serratia marcescens on B-CLL cell viability. AT514 induced apoptosis of B-CLL cells from the 21 patients studied, as confirmed by Annexin-V binding and nuclei condensation, with an average IC50 of 13 microM. AT514 was effective in those B-CLL cases resistant to fludarabine, but had no effect on normal PBL. AT514 preferentially activated the intrinsic apoptotic pathway, as evidenced by loss of mitochondrial membrane potential, release of cytochrome c and activation of caspase-9 and -3, but not of caspase-8. Importantly, AT514 interfered with phosphatidylinositol-3 kinase and protein kinase C survival signals since it increased the apoptotic effect of LY294002 and Bisl inhibitors, and induced Akt dephosphorylation at Ser 473. AT514 also decreased NF-kappaB activity by dramatically reducing the levels of p65 in B-CLL. This was confirmed on functional assays using NF-kappaB-luc-transfected Raji cells and transgenic mice. Our results establish that AT514 induces apoptosis of primary B-CLL cells and could be useful for clinical treatment of this malignancy.

Using peptides to increase transport across the intestinal barrier.

The oral route is the preferred for the administration of drugs; however, it has some serious limitations. One of the main disadvantages is poor permeability across the intestinal barrier. Various approaches are currently being adopted to overcome this issue. In this review, we describe the alternatives that use peptides to enhance intestinal absorption. First, we define the various sources of peptide enhancers followed by the analysis of the absorption mechanism used. We then comment on the possible toxic effects derived from their use as permeation enhancers, as well as potential formulation strategies. Finally, the advantages and drawbacks of peptides as intestinal enhancers are examined.

Further purification of bovine spleen inhibitors of lymphocyte DNA synthesis (chalones).

Partially purified lymphocytic factors were obtained from boving spleen; these factors are non-cytotoxic and biologically active in vitro and in vivo: [3H]Thymidine incorporation into DNA of mitogen-stimulated mouse spleen cells in culture is inhibited; similar results are obtained with phytohaemagglutinin-stimulated peripheral human lymphocytes, where blast cells transformation is blocked. [3H]Thymidine incorporation into DNA of mitogen stimulated lymphocytes withdrawn from in vivo treated mice, is also reduced. The two factors in vitro and in vivo seem to act preferentially on mouse spleen cells compared to their action on liver, kidney and testicle cells in cluture, as far as thymidine incorporation into DNA is concerned. The following techniques were applied for their purification: 1. Homogenization of the fresh tissue in water, centrifugation, dialysis of the supernatant, centrifugation, fractionation of the supernatant by alcoholic precipitation and finally concentration in vacuo and lyophilization of the material soluble at 75% of alcohol yielded fraction F. 2. Preparation of an acetone powder from the spleen, extraction of the dry powder with water, then high speed centrifugation, followed by lyophilization of the supernatant produced fraction F'. Both fractions F and F' were further fractionated by chromatography on a Sephadex G75 column: 7 peaks were obtained (F1--F7). Biological activity was found in fraction F1, corresponding to high molecular weight material, and in fraction F6, corresponding to low molecular weight substances. By rechromatography on Sephadex G 75, it is easy to dissociate from F1 a small molecular weight fraction which might be similar to F6 as far as elution volume and biological properties are concerned.

Phase II trial of weekly intravenous vinorelbine in first-line advanced breast cancer chemotherapy.

PURPOSE: This study investigated the therapeutic effects of single-agent intravenous (IV) weekly Navelbine (vinorelbine or 5'-nor-anhydro-vinblastine; Pierre Fabre Médicament, Boulogne, France), a semisynthetic vinca alkaloid, in women who had received no prior chemotherapy for locally advanced or metastatic breast cancer. PATIENTS AND METHODS: One hundred fifty-seven patients with assessable advanced or metastatic breast cancer who had received no prior chemotherapy were entered onto the study. They were stratified into five groups according to the main assessable tumor target: lung, liver, lymph nodes, skin, and others. One hundred forty-five patients were assessable for toxicity and response using World Health Organization (WHO) criteria; the 12 patients who were not evaluated were excluded because they were found not to meet the eligibility criteria. Navelbine was administered as a weekly 30-mg/m2 short IV infusion, and treatment was continued until disease progression. RESULTS: The overall response rate (WHO criteria) was 41% (complete response [CR], 7%; partial response [PR], 34%; 95% confidence interval [CI], 33% to 49%). In addition, 30% of the patients had stable disease. The response rate according to target was lymph nodes (28 of 42), 67%; liver (nine of 39), 23%; lung (10 of 30), 33%; skin (21 of 30), 70%; primary tumor (10 of 16), 56%; and bone (three of 10), 30%. The median time to treatment failure was 6 months and the median survival was 18 months. A total of 1,673 cycles were given to 145 eligible patients. At least one episode of WHO grade 3 or 4 granulocytopenia was seen in 72% of the patients. Nausea and/or vomiting, anemia, and/or thrombocytopenia were seen in less than 1% of cycles. Other side effects were rare, and additional toxicities were documented in the following proportions of patients: grade 2 to 3 alopecia, 8%; infectious episodes, 6%; and peripheral neuropathy, 3%. CONCLUSION: Our data confirm that Navelbine has major single-agent antitumor activity as front-line therapy in advanced breast cancer. Given its excellent tolerance profile and low toxicity, it should be considered for inclusion in first-line combination chemotherapy regimens.

Self-assembly of the amphipathic helix (VHLPPP)8. A mechanism for zein protein body formation.

gamma-Zein, a maize storage protein with an N-terminal proline-rich repetitive domain (gamma-ZNPRD), is located at the periphery of protein bodies. This domain appears to be indispensable for the aggregation of the protein on the surface of the organelle. The peptide (VHLPPP)8, spanning the gamma-ZNPRD, adopts a polyproline II (PPII) conformation that gives an amphipathic helix different from the alpha-helix. We used atomic force microscopy to study the surface organisation of the octamer, and transmission electron microscopy to visualise aggregates of the peptide in aqueous solution. We consider two self-assembly patterns that take account of the observed features. The micellar one fits best with the experimental results presented. Moreover, we found that this peptide has properties associated with surfactants, and form micelles in solution. This spontaneous amphipathic arrangement of the gamma-ZNPRD suggests a mechanism of gamma-zein deposition inside maize protein bodies.

Molecular analysis of peptides from the GH loop of foot-and-mouth disease virus C-S30 using surface plasmon resonance: a role for kinetic rate constants.

A foot-and-mouth disease virus (FMDV) field variant, isolate C-S30 (also named C(1)-Barcelona), is known to contain four changes within the main antigenic site A (GH loop of capsid protein VP1, residues 136-150), at least one of which (Leu147-->Val) involves a highly conserved position, critical for antibody recognition in the reference strain C-S8c1. However, immunoenzymatic analysis of FMDV C-S30 showed it was recognised by 4C4, a monoclonal antibody that specifically targets site A. This remarkable behaviour has led us to analyse the individual and combined contributions of the four mutations to the antigenicity of C-S30, by surface plasmon resonance (SPR) and enzyme-linked immunosorbent assay (ELISA) studies of pentadecapeptides displaying all possible combinations of the four replacements. Analysis of this family of C-S30-derived analogues shows a certain level of antibody recognition by SPR. In addition, SPR data suggest that kinetic rate constants provide an indirect measure, on the one hand, of paratope accessibility (association rate constant) and, on the other hand, of peptide fitness to the same paratope (dissociation rate constant).

Use of substituted and tandem-repeated peptides to probe the relevance of the highly conserved RGD tripeptide in the immune response against foot-and-mouth disease virus.

Antigenic site A of foot-and-mouth disease virus (FMDV) is an exposed, mobile loop which includes a central, highly conserved Arg-Gly-Asp tripeptide (RGD, VP1 residues 141-143 in serotype C) thought to be part of the cell attachment site. We have analyzed the contribution of RGD to the interaction of site A with antibodies by incorporating selected amino acid replacements at RGD into synthetic peptides representing site A, and analyzing the reactivity of substituted peptides with site A-specific monoclonal antibodies (MAbs). Replacement of Arg-141, Gly-142 or Asp-143 by alanine resulted in the loss of one, three and five epitopes, respectively, out of seven epitopes probed. Other replacements resulted in the loss of even larger numbers of epitopes, suggesting that the amino acids of the RGD region are either directly involved in interaction with antibodies or that they exert an important influence on the interaction of surrounding residues with antibodies. Thus, we explored the ability of tandem repeats of the RGDL sequence (corresponding to FMDV C-S8c1) to evoke neutralizing antibodies in rabbits and guinea pigs. Neutralizing activity was generally low but with a broad specificity for different FMDV serotypes and variants. Significant decreases in neutralizing titers were observed with boosting, suggesting a possible suppression of those anti-peptide antibodies which may also be directed to cellular RGD sequences. The results point to an involvement of RGD in the antigenic structure of site A, and open the possibility that broadly neutralizing antibodies might be induced by tandem repeats of the critical, conserved domain.

Cyclic disulfide model of the major antigenic site of serotype-C foot-and-mouth disease virus. Synthetic, conformational and immunochemical studies.

A cyclic disulfide peptide representing antigenic site A of foot-and-mouth disease virus (FMDV) strain C-S8c1 (residues 134 to 155 of viral protein 1 (VP1) with Tyr136 and Arg153 replaced by cystine; TTCTASARGDLAHLTTTHACHL) was synthesized by solid phase methods. Formation of the cyclic disulfide was carried out by air oxidation of the fully deprotected and reduced bis-cysteine precursor, under high dilution conditions. The identity of the cyclic peptide was confirmed by both physical and enzymatic methods. A conformational study of the cyclic peptide and of its linear parent structure (YTASARGDLAHLTTTHARHLP, residues 136-156 of VP1 of FMDV C-S8c1) by circular dichroism in the presence of a structure-inducing solvent showed the cyclic disulfide analog to adopt lower levels of alpha-helix than its linear counterpart. In competitive ELISA assays both peptides reacted with similar affinity against a representative panel of neutralizing monoclonal antibodies directed towards antigenic site A. Thus, a high inherent flexibility of this loop may preclude a conformational restriction strong enough to alter recognition by anti-virus antibodies.

Inhibition of HIV-2(ROD) replication in a lymphoblastoid cell line by the alpha1-antitrypsin Portland variant (alpha1-PDX) and the decRVKRcmk peptide: comparison with HIV-1(LAI).

We investigated the effects of alpha1-antitrypsine Portland variant (alpha1-PDX) and decanoylRVKRchloromethylketone (decRVKRcmk) on HIV-2(ROD) replication in the Jurkat lymphoblastoid cell line. To this end, cells were stably transfected with the alpha1-PDX (J-PDX) and used as targets for HIV-2(ROD) infection. Controls were prepared with the empty vector (J-pcDNA3). HIV-2(ROD) and HIV-1(LAI) replications were significantly inhibited and delayed in the presence of the alpha1-PDX protein. When decRVKRcmk was used at 35 microM, inhibition rates were 70-80% for HIV-2(ROD) and HIV-1(LAI), while total inhibition occurred at 70 microM. Control peptides consisting of decanoylRVKR and acetylYVADcmk had no effect. In the presence of the alpha1-PDX or the decRVKRcmk at 35 microM, the infectivity of HIV-2(ROD) and HIV-1(LAI) produced was 3-4-fold lower. Both molecules inhibited syncytium formation by HIV-2(ROD) and HIV-1(LAI) to a considerable extent. Finally, the inhibition of viral replication was correlated with the ability of the decRVKRcmk at 35 and 70 microM and of the alpha1-PDX, to inhibit the processing of envelope glycoprotein precursors. The alpha1-PDX protein and the decRVKRcmk peptide at 35 microM inhibited HIV-2 and HIV-1 to a similar level suggesting that identical or closely related endoproteases are involved in the maturation of their envelope glycoprotein precursors into surface and transmembrane glycoproteins. The significant inhibition observed with alpha1-PDX indicates that furin or furin-like endoproteases appear to play a major role in the maturation process.

Neoadjuvant chemotherapy in operable breast cancer.

Primary chemotherapy in localised breast cancer may prevent tumour spread during surgical treatment and reduce proliferation of micrometastases. A randomised clinical trial, in 196 premenopausal and postmenopausal patients with operable (T2-3, N0-1b) breast cancer, was started in November 1983 at the Institut Curie to compare neoadjuvant and adjuvant regimens of chemotherapy with radiotherapy with or without surgery. The patients have been followed up for 35-70 months (median 54). A neoadjuvant group received two monthly cycles of intravenous doxorubicin/cyclophosphamide/5-fluorouracil before locoregional therapy and four cycles subsequently. Six monthly cycles following locoregional therapy were administered to the adjuvant group. Because of inclusion of postmenopausal and/or node-negative patients, compliance was less than optimal in 39 patients who were analysed separately according to actual dose received. Tumour response, evaluated after two cycles of neoadjuvant chemotherapy, was significantly associated with dose (P = 0.003). Survival showed a slight non-significant advantage for the neoadjuvant group. Survival plotted by actual dose was also similar. Neoadjuvant chemotherapy was safe and at least as effective as the adjuvant regimen. Patients have been accrued to a subsequent larger trial of chemotherapy as first-line treatment.

Prognostic factors in inflammatory breast cancer and therapeutic implications.

223 inflammatory breast cancer patients were diagnosed at the Institut Curie between 1977 and 1987. Patients received chemotherapy and radiation treatment according to three consecutive randomised trials. Five- and 10- year survival rates were 41 and 32%, respectively. Disease-free interval rates were 25.5% at 5 years and 19% at 10 years. Parameters significantly linked with a pejorative prognosis in a multivariate analysis were: diffuse erythema, lymph node involvement, chest wall adherence, and age above 50 years. When therapeutic response parameters were included in the multivariate analysis, the five most important prognostic factors in order of significance were complete tumour regression after completion of induction treatment (at 8 months), complete regression of inflammatory symptoms after 3 months of neoadjuvant chemotherapy, limited erythema at presentation and, less significantly, complete regression of inflammatory symptoms at 8 months and tumour regression at 3 months. In conclusion, patients who achieved a rapid and complete remission had a better prognosis than patients who had an incomplete response to chemotherapy. High-dose chemotherapy and reversal or prevention of drug resistance will be evaluated in future trials. Detailed information on the biology of this disease should allow the design of new strategies aiming to improve patient management.

Breast tumour response to primary chemotherapy predicts local and distant control as well as survival.

The purpose of the present paper was to evaluate correlations between clinical response to chemotherapy and outcome in a subgroup analysis of premenopausal patients with tumours considered too large for breast conserving surgery, treated with primary chemotherapy (n = 200) from a previously published trial (Scholl S.M., Fourquet A., Asselain B, et al. Eur J Cancer 1994, 30A, 645-652). Objective response rates amounted to 65% following four courses. In a multivariate Cox regression analysis, comparing seven parameters, the following variables were associated with poor survival: clinically involved nodes [N1b:RR: 2.7 (95% CI 1.3-5.3)], the failure to respond to chemotherapy [D:RR: 2.62 (95% CI 1.3-5)] and a raised S phase fraction [SPF > 5%: RR: 2.4 (95% CI 1.2-5)]. Parameters associated with increased metastatic recurrence rates, by order of entry in the model, were: young age [< 35: RR: 2.46 (95% CI 1.2-5)], large clinical tumour size [T3: RR: 2.02 (95% CI 1.2-3.4)], poor histological grade (SBR III: RR: 1.93 (95% CI 1.1-3.3)] and the failure to respond to chemotherapy [D: RR: 1.91 (95% CI 1-3.4)]. The assessment of both tumour cell proliferation rates as well as possibly drug resistance markers (although not available in the present study) should be helpful in selecting patients likely to benefit from intensified chemotherapy regimens. The most accurate predictor of response in the present study appeared to be the response to chemotherapy treatment itself.

Direct single-step surface plasmon resonance analysis of interactions between small peptides and immobilized monoclonal antibodies.

Surface plasmon resonance (SPR) methods have been optimized to permit direct kinetic analysis of the antigenic peptide analytes interacting with immobilized monoclonal antibodies (mAbs). High reproducibility and a significant correlation between SPR and previous ELISA data on the same set of antibodies and peptides were observed. The kinetic data obtained provide further insight into the structure of the main antigenic site of foot-and-mouth disease virus (FMDV).

Synthesis and antitumor evaluation of new thiazolo[5,4-b]quinoline derivatives.

A new synthesis of 9-hydroxy- and 9-(alkylamino)thiazolo[5,4-b]quinolines by cyclization of 4-(ethoxycarbonyl)-5-(arylamino)thiazoles and 5-(arylamino)-4-carbamoylthiazoles, respectively, is described. In vitro cytotoxicity of a large number of derivatives of these compounds has been tested against several cell lines. The highest activities observed are associated with the presence of a 2-[[(N,N-diethylamino)ethyl]amino] substituent at C-2 and a fluorine atom at the C-7 position of the tricyclic planar heteroaromatic framework. Three structural features seem to be essential for antitumor activities: a positive charge density at carbon C-7, a side chain at position C-2 or C-9 of the thiazoloquinoline skeleton with two basic nitrogens and a pKa value of 7.5-10 in the most basic center, and a conformational flexibility of this basic side chain. These structural requirements must be simultaneously satisfied in order to ensure a significant antitumor activity.