Biomedical subjects

Jonathan Hall

Publications and source records attributed to Jonathan Hall.

23 records · Page 2Linked to original sources

PubMed2002

Bcl-2/bcl-xL bispecific antisense treatment sensitizes breast carcinoma cells to doxorubicin, paclitaxel and cyclophosphamide.

Overexpression of the anti-apoptotic proteins bcl-2 and bcl-xL is implicated in breast cancer development, tumor progression and drug resistance. Here we describe the use of the bcl-2/bcl-xL bispecific antisense oligonucleotide 4625 to sensitize breast carcinoma cells to anti-cancer drugs routinely used in breast cancer therapy. MCF7 cells were treated with oligonucleotide 4625, doxorubicin, paclitaxel or cyclophosphamide alone, or with combinations of oligonucleotide and the anti-cancer drugs. As measured in cell viability assays, treatment with the various combinations reduced the number of viable MCF7 cells more effectively than treatment with the single drugs alone. Treatment with a sequence control oligonucleotide did not affect cell viability. All combination treatments induced apoptosis as demonstrated by the appearance of massive nuclear condensation in a high proportion of the cells. To further characterize the interaction between 4625 and doxorubicin, paclitaxel or cyclophosphamide, the median-effect method was used. In MCF7 cells all combinations resulted in potent synergistic effects over a broad range of toxicity with combination indices ranging from 0.8 to 0.1. Similarly, strong synergistic interactions between oligonucleotide 4625 and the anti-cancer drugs were also observed in cultures of the breast carcinoma cell line MDA-MB-231. Our data suggest the use of 4625 as a potent adjuvant in breast cancer chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2002

Bcl-2 and bcl-xL antisense oligonucleotides induce apoptosis in melanoma cells of different clinical stages.

Recent clinical studies have shown the promise of bcl-2 antisense therapy in patients with melanoma. To further demonstrate the importance of bcl-2 and validate the related antiapoptotic protein bcl-xL as targets for antisense therapy in melanoma, their implication as survival factors in melanoma cells of different clinical stages as well as in normal melanocytes was investigated. Primary cell cultures derived from 17 melanomas, the cell line A375, and normal melanocytes from healthy donors were treated with antisense oligonucleotides targeting either the bcl-xL mRNA or the bcl-2 and the bcl-xL mRNAs simultaneously. Bcl-2 and bcl-xL expression in cells was analyzed by real-time polymerase chain reaction and Western blotting. Cell viability was assessed in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and apoptosis assays. Bcl-2 expression was low in melanoma cells of stages I, II, and III, hardly detectable in A375 cells, but high in normal melanocytes. Bcl-xL expression was high in all cell types tested. As shown in A375 cells and the stage III melanoma cells 0513, both the bcl-xL monospecific oligonucleotide 4259 and the bcl-2/bcl-xL bispecific oligonucleotide 4625 effectively reduced tumor cell viability by induction of apoptosis with IC50 values ranging from 200 to 350 nM. Oligonucleotide 4625 proved to be superior to 4259, as it significantly reduced the viability of cells from all melanoma stages. Both oligonucleotides reduced also the viability of normal melanocytes. Our data suggest that bcl-2 and bcl-xL are promising targets for antisense therapy of melanoma, and that the simultaneous downregulation of their expression may provide additional clinical benefit.

Apoptosis↗

PubMed2002

Crystalloid strong ion difference determines metabolic acid-base change during in vitro hemodilution.

OBJECTIVES: To determine the relationship between the strong ion difference (SID) of a diluting crystalloid and its metabolic acid-base effects on in vitro blood dilution. DESIGN: Prospective in vitro study. SETTING: University research laboratory. SUBJECTS: Normal human blood. INTERVENTIONS: Three solutions were prepared, each with [Na] 140 mmol/L. [Cl-] for solutions 1, 2, and 3 was 120, 110, and 100 mmol/L, respectively, the other anion being HCO3-. SID values were thus 20, 30, and 40 mEq/L, respectively. Serial dilutions of well-oxygenated fresh venous blood were performed anaerobically by using each of solutions 1-3 as well as 0.9% saline (SID = 0 mEq/L) and Hartmann's solution (SID = -4 mEq/L). MEASUREMENTS AND MAIN RESULTS: Blood gas and electrolyte analyses were performed before and after each dilution. Apart from dilutions with solution 3 (crystalloid SID 40 mEq/L) during which plasma SID did not change, plasma SID decreased during hemodilution. In contrast, base excess increased during hemodilution with solutions 3 and 2 (crystalloid SID 40 mEq/L and 30 mEq/L, respectively) and decreased only with the remaining three solutions. The relationships between hemoglobin concentrations and both plasma SID and whole blood base excess throughout dilution were linear, with slopes proportional to the SID of the diluent in each case. Linear regression revealed that the SID of crystalloid producing a zero base excess/hemoglobin concentration slope during blood dilution (i.e., no change in metabolic acid-base status) is 23.7 mEq/L. CONCLUSIONS: On in vitro hemodilution, there is a simple linear relationship between diluent crystalloid SID and the rate and direction of change of plasma SID and whole blood base excess. Direct extrapolation to in vivo situations such as acute normovolemic hemodilution and large volume correction of extracellular fluid deficits requires experimental confirmation.

Acid-Base Equilibrium↗

PubMedDate not supplied

Artificial ribonucleases: efficient and specific in vitro cleavage of human c-raf-1 RNA.

We report here the first successful sequence-specific cleavage of large RNA using artificial ribonucleases. A series of uniformly 2'-methoxyethoxy-modified oligonucleotides bearing a europium complex were investigated as artificial ribonucleases specific for the human c-raf-1 mRNA. The efficiency and specificity of these oligonucleotide-metal conjugates to bind and to cleave 571 and 2,977 nucleotides long c-raf-1 RNA transcripts in vitro in a sequence-specific manner is demonstrated. Quantitative analysis reveals a cleavage efficiency of 60-70% within 4 h at 37 degrees C. Precise mapping of cleavage sites using primer extension analysis shows that cleavage generally occurs at two or three major sites adjacent to the 3'-end of the RNA target region. Cleavage is preferentially observed after purine nucleotides. This study demonstrates the potency of artificial ribonucleases targeting large, biologically relevant RNAs.

Europium↗

PubMedDate not supplied

A role for oligonucleotide-based RNA-knock down technologies in functional genomics.

Functional genomics is inundating the pharmaceutical industry with large numbers of potential gene targets from several sources such as gene expression profiling experiments (DNA microchips, proteomics) or database mining. Oligonucleotide-based RNA-knock down technologies such as antisense or RNA interference can aid in the filtering and prioritization of target candidates in the drug discovery process.

Drug Industry↗