Rebecca Hancock

Tetraphenylphosphonium chloride induced mr‐visible lipid accumulation in a malignant human breast cell line

The effect of the cationic lipophilic phosphonium salt tetraphenylphosphonium chloride (TPP) on a human malignant breast cell line, DU4475, was monitored with proton nuclear magnetic resonance (1H MRS). TPP caused a dose‐ and time‐dependent increase in resonances arising from MR‐visible lipid as measured by the CH2/CH3 ratio in the I‐dimensional 1H MR spectrum. Two‐dimensional MRS identified increases in the glycerophosphocholine/lysine cross‐peak ratio and corresponding decreases in the phosphocholine/lysine ratio in a dose‐dependent fashion in TPP‐treated cells. Lipid metabolic changes are discussed in the light of other MR experiments, and the data indicate that accumulation of MR‐visible lipids may arise from the rearrangement of phospholipids accompanying mitochondrial destruction or from the catabolism of phospholipids associated with early events in the cytotoxic process.

Modulation of MR-visible mobile lipid levels by cell culture conditions and correlations with chemotactic response.

A transformed murine fibroblast cell line has been used to assess which criteria govern the appearance of a lipid pool that is mobile on the MR time scale. A high‐resolution proton MR signal arising from neutral lipids, including triglyceride and cholesteryl esters, has previously been associated with membrane events in stimulated, transformed and malignant cells. We report that the attenuation of cellular proliferation by confluence or low pH caused significant increases in MR‐visible lipid and that the lipid signal could be amplified at high density by the removal of serum. A significant decrease in chemotactic response accompanied the culture of cells at high density, but chemotactic response was not generally linked to alteration of the lipid signal. The appearance of the signal was also not correlated with the proportion of cells in any phase of the cell cycle. Significant changes in the MR‐visible pools of the lipid metabolites choline, phosphocholine and glycerophosphocholine were measured under the culture conditions employed with 2D MRS and suggest that MR‐visible lipid may arise from the catabolism of phospholipids.

Induction of magnetic resonance-visible lipid in a transformed human breast cell line by tetraphenylphosphonium chloride

Proton magnetic resonance spectroscopy (1H MRS) and DNA flow cytometry were used to monitor the effects of the cationic lipophilic phosphonium salt and potential antineoplastic agent tetraphenylphosphonium chloride (TPP) on the transformed human breast cell line HBL‐100. TPP treatment for 48 hr was cytostatic at low concentrations and cytotoxic at higher concentrations with an IC50 of 55 μM as measured by Trypan blue exclusion. At micromolar concentrations, TPP caused a significant increase in the methylene MR signal arising from mobile lipid as measured by the ratio of the lipid CH2 peak height to either the CH3 peak height (internal referencing) or the peak height for p‐aminobenzoic acid (PABA) as an external reference in a co‐axial capillary within the sample. Over the same concentration range, TPP caused a slowing of passage through S phase as demonstrated by a significant depletion of cells in G2/M phase with a concurrent but non‐significant increase in cells in S. Time‐dependent increases in MR‐visible lipid were observed with 2 μM TPP treatment, and the removal of TPP from the culture medium caused no significant reduction in mobile lipid. Two‐dimensional 1H|Cv1H COSY spectra of TPP‐treated HBL‐100 cells revealed concentration‐dependent increases in cross‐peak volume ratios arising from lipid acyl chains relative to both internal (lysine, polyamines) and external (PABA) standards. Increases in choline and glycerophosphocholine cross‐peak volume ratios were observed, indicating that the catabolism or rearrangement of phospholipids may be responsible for the observed MR‐visible lipid increases. Int. J. Cancer 73:570–579, 1997.

MALIGNANCY-RELATED CHARACTERISTICS OF WILD TYPE AND DRUG-RESISTANT CHINESE HAMSTER OVARY CELLS

&NA; Chinese hamster ovary (CHO) cell lines are a very popular cell model for a wide range of studies but are often misused experimentally as a substitute for normal cells. Although CHO was originally derived from normal tissue, the cell lines studied here, including the parental wild type, have many characteristics which indicate that they have undergone malignant transformation. Biological properties associated with malignancy were investigated in this study on wild type CHO cells and 4 drug resistant sublines, EOT, Col R‐22, Pod R11‐6, and Vin R‐1. We report evidence of tumorigenicity in experimental animals, invasive capacity, in vivo and in vitro, protease release by 2 of the cell lines, features related to drug resistance in the mutant sublines, and numerical and structural chromosomal abnormalities.