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Biomedical subjects

A Photiou

Publications and source records attributed to A Photiou.

12 recordsLinked to original sources
PubMed2001

Melanocyte-Directed enzyme prodrug therapy (MDEPT): development of second generation prodrugs for targeted treatment of malignant melanoma.

Evaluation of second generation prodrugs for MDEPT, by oximetry, has highlighted structural properties that are advantageous and disadvantageous for efficient oxidation using mushroom tyrosinase. In particular, a sterically undemanding prodrug bis-(2-chloroethyl)amino-4-hydroxyphenylaminomethanone 28 was synthesised and found to be oxidised by mushroom tyrosinase at a superior rate to tyrosine methyl ester, the carboxylic acid of which is the natural substrate for tyrosinase. The more sterically demanding phenyl mustard prodrugs 9 and 10 were oxidised by mushroom tyrosinase at a similar rate to tyrosine methyl ester. In contrast, tyramine chain elongation via heteroatom insertion was detrimental and the rate of mushroom tyrosinase oxidation of phenyl mustard prodrugs 21 and 22 decreased by 10 nanomol/min.

Agaricales↗
PubMed2001

Absence of the t(14;18) chromosomal translocation in primary cutaneous B-cell lymphoma.

BACKGROUND: The t(14;18)(q32;q21) chromosomal translocation is found in the majority of nodal follicular lymphomas and in a lower percentage of systemic high-grade diffuse large B-cell lymphomas. The translocation results in the juxtaposition of the bcl-2 gene on chromosome 18 with the immunoglobulin heavy chain joining region on chromosome 14. Bcl-2 protein prevents apoptosis and the translocation leads to overexpression of a functionally normal Bcl-2 protein that prevents apoptosis of neoplastic cells. OBJECTIVES: The purpose of our study was to analyse cases of primary cutaneous B-cell lymphoma (PCBCL) for the presence of the t(14;18) translocation and to correlate the results with Bcl-2 expression and histological subtype. METHODS: Forty-four cutaneous B-cell lymphoid proliferations (36 PCBCL, four follicular B-cell lymphomas with cutaneous presentation and four reactive B-cell infiltrates) were analysed by polymerase chain reaction amplification and polyacrylamide gel electrophoresis using consensus primers for the joining region on the immunoglobulin heavy chain gene in combination with either a primer for the major breakpoint region (MBR) or the minor cluster region (mcr) on chromosome 18. RESULTS: None of 36 PCBCL analysed demonstrated a t(14;18) translocation; however, three of four systemic follicular B-cell lymphomas presenting in the skin were found to have a translocation in the MBR, which was confirmed by sequence analysis. Correlation with Bcl-2 immunostaining showed that of seven patients with high-grade cutaneous diffuse large B-cell lymphoma, four were Bcl-2 positive but had no evidence of a t(14;18) translocation. In the five cases classified as primary cutaneous follicle centre cell lymphoma, the neoplastic cells within the germinal centres failed to express Bcl-2. However, Bcl-2-positive neoplastic cells were present in all four cases of systemic follicular lymphoma, including the case that did not show a t(14;18) translocation. In all cases of marginal zone lymphoma the marginal zone lymphocytes were Bcl-2 positive. CONCLUSIONS: These findings indicate that the t(14;18) translocation does not occur in PCBCL, which suggests the involvement of different pathogenetic mechanisms compared with their nodal counterparts. Furthermore, the detection of a t(14;18) translocation in cutaneous B-cell lymphoma should suggest the presence of systemic disease, which underlies the need for exhaustive staging procedures.

Chromosomes, Human, Pair 14↗
PubMed2000

In vitro cytotoxicity of norviburtinal and isopinnatal from Kigelia pinnata against cancer cell lines.

Crude dichloromethane extracts of Kigelia pinnata stem bark and fruit showed cytotoxic activity in vitro against cultured melanoma and other cancer cell lines using the Sulphorhodamine B assay, which was used for bioassay-guided fractionation. Thin layer chromatography (TLC) examination of the most active fractions of both stem bark and fruits showed the presence of the same major components which were found to be norviburtinal and beta-sitosterol. Norviburtinal was found to be the most active compound but had little selectivity for melanoma cell lines whilst isopinnatal also showed some cytotoxic activity. beta-Sitosterol was found to be comparatively inactive. HPLC analysis of the crude extract showed that the amount of norviburtinal present in the plant material did not account for all of the activity of the total extracts.

Anthraquinones↗
PubMed1999

Melanocyte-directed enzyme prodrug therapy (MDEPT): development of a targeted treatment for malignant melanoma.

A novel prodrug rationally designed to function as a tyrosinase substrate has been synthesised to allow targeted treatment of malignant melanoma. This agent has been evaluated for tyrosinase-mediated drug release, and has been shown to act in the desired manner. Furthermore, differential cytotoxicity has been demonstrated in cell lines which express tyrosinase and those which do not.

Animals↗
PubMed1997

In vitro synergy of paclitaxel (Taxol) and vinorelbine (navelbine) against human melanoma cell lines.

Paclitaxel (PTXL) (Taxol), a taxane, and vinorelbine (VRB), a semisynthetic vinca alkaloid drug, have tubulin as their common intracellular target, but inhibit growth by binding to different sites. We evaluated in vitro the antiproliferative activity of these two drugs as single agents and in combination, against two human melanoma cell lines, G361 and StM111a. The SRB (sulphorhodamine B) assay was used to determine growth inhibition. Possible drug-drug interaction at the cellular level was assessed by constructing Isoboles (Isobologram analysis) and applying the concept of an 'envelope of additivity'. Both agents were active in the nanomolar range at clinically achievable concentrations. The mean IC50 for G361 was 46.6 nM (PTXL) and 19.9 nM (VRB) after a 1 h drug exposure. Mean IC50 (1 h) for StM111a was 9.7 nM (PTXL) and 26.9 nM (VRB). Isobole analysis at the isoeffect levels of 25%, 50% and 75% indicated that drug interaction was predominantly synergistic (supra-additive) when paclitaxel and VRB were added concurrently for 1 h to cultures of StM11 1a or G361. In some experiments, this synergy was observed with particularly low concentrations of paclitaxel (3 nM) and VRB (0.01 nM). A new points were located within the envelope of additivity or in the subadditive (antagonism) region of the isobole. An overall synergy was also found if the data were analysed by the median effect analysis. The effect of these agents on the cytoskeleton and ultrastructure were studied with immunofluorescence and electron microscopy, respectively. These results confirm the in vitro inhibitory activity of paclitaxel and VRB against malignant melanoma, but more importantly the two drugs appear to act synergistically at relatively low concentrations.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

The combination of paclitaxel with cisplatin exhibits antagonism in vitro against human melanoma.

The in vitro cytotoxicity of paclitaxel and cisplatin, alone and in combination, was evaluated against the established human melanoma cell line, G361, with either 1 or 24 h asynchronous paclitaxel exposure using the sulforhodamine B assay. As single agent, the mean cisplatin concentration which inhibited G361 cell growth by 50% (IC50) was 10,000 nM for 1 h exposure. IC50 values obtained with 1 and 24 h paclitaxel exposure were, respectively, 63 and 3.8 nM, concentrations clinically achievable. The combination of paclitaxel with cisplatin was found to be antagonistic by the classical isobologram method, independent of drug sequence and of paclitaxel exposure time. The antagonism was significantly more pronounced for the sequence of paclitaxel followed by cisplatin compared with the reverse sequence for both 1 and 24 h paclitaxel exposure time (p < 0.05). Future clinical protocols employing paclitaxel and cisplatin, both active single agents for the treatment of metastatic malignant melanoma, should take into consideration that the combination of the two drugs may result in significant antagonism, irrespective of drug sequence, if administered within a short interval of each other.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Activity of extracts of Kigelia pinnata against melanoma and renal carcinoma cell lines.

Serial dilutions of standardised water, ethanol, and dichloromethane extracts of the stembark and fruits of Kigelia pinnata were tested for their growth inhibitory effects against four melanoma cell lines and a renal cell carcinoma line (Caki-2) using two different (MTT and SRB) assays. Lapachol, a possible constituent of these extracts, together with known therapeutic antineoplastic agents, was also tested in the same way. The IC50 of each extract was measured after extracts were diluted to 100 micrograms/ml in 1% ethanol or water. Significant inhibitory activity was shown by the dichloromethane extract of the stembark and lapachol (continuous exposure). Moreover, activity was dose-dependent, the extract being less active after 1 h exposure. Chemosensitivity of the melanoma cell lines to the stembark was greater than that seen for the renal adenocarcinoma line. In marked contrast, sensitivity to lapachol was similar amongst the five cell lines. Lapachol was not detected in the stembark extract.

Antineoplastic Agents, Phytogenic↗
PubMed1992

Antiproliferative activity of vinorelbine (Navelbine) against six human melanoma cell lines.

We compared in vitro the cytotoxic activity of vinorelbine (VRB) (Navelbine, 5'-nor-anhydro-vinblastine) a novel Vinca alkaloid, with that of vinblastine (VBL) vincristine (VCR) and vindesine (VDS). Five continuous human melanoma cell lines (C32, G361, StMl11a, StMl12d and StMl14a) and a new line WHMel 1, were used in this study. In growth-inhibition assays, VDS and VRB exhibited comparable cytotoxicity against the C32 and G361 melanoma lines; the effect being dose- and time-dependent. VRB appeared less inhibitory compared to VDS in the lowest concentrations (0.1-1 nM). The same activity was observed with 0.1-1 microM. These drugs exhibited comparable growth inhibition at clinically achievable doses. The MTT assay was used to compare VBL, VCR, VDS, and VRB. Overall IC50 values (concentration required to reduce viability by 50%) ranged from 1 pM to 10 nM. The reduction in cell viability with VRB was similar to that observed with the reference drugs in four out of five lines tested by this method. However a trend was observed for IC50 values to be lower with VBL and VDS. In clonogenic assays (StMl11a, StMl12d and StMl14a lines, 1 h exposure) VRB and VDS produced the same reduction in survival. Survival curves were exponential followed by a terminal plateau. IC50 values ranged from 60 nM to 70 nM. Our results indicate that VRB has in vitro activity against six melanoma lines with differing phenotypic characteristics.

Antineoplastic Agents↗
PubMed1986

Effect of hypothermia on radiosensitization.

Hypothermia reduces metabolism and oxygen utilization by tissues. If the blood supply to a solid tumour can be maintained at a sufficient level, the hypoxic fraction of tumour cells may be reduced and radiosensitivity increased. This may be achieved if hyperbaric oxygen is used in combination with the hypothermia. The blood supply and oxygen tension have been measured in C3H mouse mammary tumours under hypothermia and hyperbaric oxygen, and the enhancement of radiosensitivity by hyperbaric oxygen has been estimated in mice irradiated at different temperatures with and without anaesthesia. Measurement of xenon-133 clearance showed that the blood supply of a tumour tended to increase when anaesthetized mice became hypothermic. Oxygen cathode data showed that the oxygen tension tended to be relatively higher in tumours and lower in subcutaneous tissue when mice exposed to hyperbaric oxygen became hypothermic under anaesthesia. Hyperbaric oxygen enhanced the radiation response of the tumour in terms of an increase in regrowth delay by a factor of 1.7 when the mice had been anaesthetized, whether or not they became hypothermic. A lower factor of 1.4 was obtained without anaesthesia although induced hypothermia increased the response to a small extent. We conclude that anaesthesia and hypothermia affect oxygen metabolism in tumours by different mechanisms.

Adenocarcinoma↗
PubMedDate not supplied

Activity of platinum drugs against melanoma cell lines: is it modulated in vitro in the presence of tamoxifen?

Cisplatin and carboplatin have been used against human malignant melanoma as single agents and in combination. Tamoxifen is used in the treatment of breast cancer, but has no significant activity against human malignant melanoma. Tamoxifen, however, has been promoted as a modulator in some drug regimens. The addition of tamoxifen to cisplatin or carboplatin has been reported to enhance their activity against the human melanoma cell line T-289. We investigated whether tamoxifen potentiates, in vitro, the activity of cisplatin and carboplatin against C32, G361 and StMl11a melanoma cell lines. Tamoxifen alone at clinically achievable concentrations of 0.1 and 1.0 microM (168 hrs exposure) had no significant effect on growth. No chemopotentiation of the activity of cisplatin or carboplatin was observed with the addition of tamoxifen (0.1 and 1.0 microM). The platinum drugs were added for 1 hr (serially diluted from 100.0 microM). Against the G361 line there was a trend towards chemopotentiation of cisplatin by 0.1 microM of tamoxifen. However, this did not reach statistical significance. Tamoxifen (5.0 and 10.0 microM) produced some inhibitory activity, and a trend towards synergy with cisplatin was observed. However, these concentrations are not clinically feasible. Previous reports detecting synergistic interaction between tamoxifen (0.1 and 1.0 microM), and the platinum compounds against the T-289 melanoma cell line cannot be supported in our in vitro system.

Carboplatin↗
PubMedDate not supplied

Growth inhibitory activity of S12363, a novel vinca alkaloid derivative on human melanoma cell lines.

The growth inhibitory activity of S12363, a new antineoplastic agent which belongs to the vinca alkaloid group incorporating an amino-phosphonate (bioester of valine), was studied on six human melanoma cell lines with different phenotypic characteristics and in vitro growth rates. S12363 was compared with vinblastine (VBL), vincristine (VCR) and vindesine (VDS) using the MTT assay. Inhibition was time- and dose-dependent. Overall, IC50 values ranged from 24-6770nM and 4.6-11.6 nM for the reference drugs and for S12363 respectively, after exposure for 1 hr. All the vinca alkaloids were more active when cells were exposed continuously for 72 hrs, inhibition by S12363 was greater than the reference drugs (p < 0.05 in 15/18 comparisons). The activities of VDS and S12363 were also compared using the clonogenic assay. IC50 values ranged from 45-500 nM and 17-75 nM respectively. On a molar basis, S12363 was significantly more active than VDS (ANOVA p < 0.0001). The shape of the cell survival curve obtained with S12363 was exponential, whereas that of VDS was of the exponential-plateau type. Furthermore, survival with higher concentrations of S12363 was inversely related to cells seeded. Cell cycle analysis showed these compounds to block cells in G2+M after exposure to their respective IC50 concentrations for 1 hr. This effect was obtained using a lower S12363 concentration. In summary, S12363 proved to be 18-83 times more active than the reference drugs in the MTT and 3-11 times more active than VDS in the clonogenic assay. Its high potency and dissimilar cell survival profile indicate that this compound possesses different biological properties, and therefore merits further in vivo evaluation.

Antineoplastic Agents, Phytogenic↗